{-
(c) The AQUA Project, Glasgow University, 1993-1998

\section[Simplify]{The main module of the simplifier}
-}

{-# LANGUAGE CPP #-}

module Simplify ( simplTopBinds, simplExpr, simplRules ) where

#include "HsVersions.h"

import GhcPrelude

import DynFlags
import SimplMonad
import Type hiding      ( substTy, substTyVar, extendTvSubst, extendCvSubst )
import SimplEnv
import SimplUtils
import OccurAnal        ( occurAnalyseExpr )
import FamInstEnv       ( FamInstEnv )
import Literal          ( litIsLifted ) --, mkLitInt ) -- temporalily commented out. See #8326
import Id
import MkId             ( seqId )
import MkCore           ( mkImpossibleExpr, castBottomExpr )
import IdInfo
import Name             ( mkSystemVarName, isExternalName, getOccFS )
import Coercion hiding  ( substCo, substCoVar )
import OptCoercion      ( optCoercion )
import FamInstEnv       ( topNormaliseType_maybe )
import DataCon          ( DataCon, dataConWorkId, dataConRepStrictness
                        , dataConRepArgTys, isUnboxedTupleCon
                        , StrictnessMark (..) )
import CoreMonad        ( Tick(..), SimplMode(..) )
import CoreSyn
import Demand           ( StrictSig(..), dmdTypeDepth, isStrictDmd )
import PprCore          ( pprCoreExpr )
import CoreUnfold
import CoreUtils
import CoreOpt          ( pushCoTyArg, pushCoValArg
                        , joinPointBinding_maybe, joinPointBindings_maybe )
import Rules            ( mkRuleInfo, lookupRule, getRules )
import Demand           ( mkClosedStrictSig, topDmd, exnRes )
import BasicTypes       ( TopLevelFlag(..), isNotTopLevel, isTopLevel,
                          RecFlag(..), Arity )
import MonadUtils       ( mapAccumLM, liftIO )
import Var              ( isTyCoVar )
import Maybes           (  orElse )
import Control.Monad
import Outputable
import FastString
import Pair
import Util
import ErrUtils
import Module          ( moduleName, pprModuleName )
import PrimOp          ( PrimOp (SeqOp) )


{-
The guts of the simplifier is in this module, but the driver loop for
the simplifier is in SimplCore.hs.

Note [The big picture]
~~~~~~~~~~~~~~~~~~~~~~
The general shape of the simplifier is this:

  simplExpr :: SimplEnv -> InExpr -> SimplCont -> SimplM (SimplFloats, OutExpr)
  simplBind :: SimplEnv -> InBind -> SimplM (SimplFloats, SimplEnv)

 * SimplEnv contains
     - Simplifier mode (which includes DynFlags for convenience)
     - Ambient substitution
     - InScopeSet

 * SimplFloats contains
     - Let-floats (which includes ok-for-spec case-floats)
     - Join floats
     - InScopeSet (including all the floats)

 * Expressions
      simplExpr :: SimplEnv -> InExpr -> SimplCont
                -> SimplM (SimplFloats, OutExpr)
   The result of simplifying an /expression/ is (floats, expr)
      - A bunch of floats (let bindings, join bindings)
      - A simplified expression.
   The overall result is effectively (let floats in expr)

 * Bindings
      simplBind :: SimplEnv -> InBind -> SimplM (SimplFloats, SimplEnv)
   The result of simplifying a binding is
     - A bunch of floats, the last of which is the simplified binding
       There may be auxiliary bindings too; see prepareRhs
     - An environment suitable for simplifying the scope of the binding

   The floats may also be empty, if the binding is inlined unconditionally;
   in that case the returned SimplEnv will have an augmented substitution.

   The returned floats and env both have an in-scope set, and they are
   guaranteed to be the same.


Note [Shadowing]
~~~~~~~~~~~~~~~~
The simplifier used to guarantee that the output had no shadowing, but
it does not do so any more.   (Actually, it never did!)  The reason is
documented with simplifyArgs.


Eta expansion
~~~~~~~~~~~~~~
For eta expansion, we want to catch things like

        case e of (a,b) -> \x -> case a of (p,q) -> \y -> r

If the \x was on the RHS of a let, we'd eta expand to bring the two
lambdas together.  And in general that's a good thing to do.  Perhaps
we should eta expand wherever we find a (value) lambda?  Then the eta
expansion at a let RHS can concentrate solely on the PAP case.

************************************************************************
*                                                                      *
\subsection{Bindings}
*                                                                      *
************************************************************************
-}

simplTopBinds :: SimplEnv -> [InBind] -> SimplM (SimplFloats, SimplEnv)
-- See Note [The big picture]
simplTopBinds :: SimplEnv -> [InBind] -> SimplM (SimplFloats, SimplEnv)
simplTopBinds env0 :: SimplEnv
env0 binds0 :: [InBind]
binds0
  = do  {       -- Put all the top-level binders into scope at the start
                -- so that if a transformation rule has unexpectedly brought
                -- anything into scope, then we don't get a complaint about that.
                -- It's rather as if the top-level binders were imported.
                -- See note [Glomming] in OccurAnal.
        ; SimplEnv
env1 <- {-#SCC "simplTopBinds-simplRecBndrs" #-} SimplEnv -> [InBndr] -> SimplM SimplEnv
simplRecBndrs SimplEnv
env0 ([InBind] -> [InBndr]
forall b. [Bind b] -> [b]
bindersOfBinds [InBind]
binds0)
        ; (floats :: SimplFloats
floats, env2 :: SimplEnv
env2) <- {-#SCC "simplTopBinds-simpl_binds" #-} SimplEnv -> [InBind] -> SimplM (SimplFloats, SimplEnv)
simpl_binds SimplEnv
env1 [InBind]
binds0
        ; Tick -> SimplM ()
freeTick Tick
SimplifierDone
        ; (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats
floats, SimplEnv
env2) }
  where
        -- We need to track the zapped top-level binders, because
        -- they should have their fragile IdInfo zapped (notably occurrence info)
        -- That's why we run down binds and bndrs' simultaneously.
        --
    simpl_binds :: SimplEnv -> [InBind] -> SimplM (SimplFloats, SimplEnv)
    simpl_binds :: SimplEnv -> [InBind] -> SimplM (SimplFloats, SimplEnv)
simpl_binds env :: SimplEnv
env []           = (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplEnv -> SimplFloats
emptyFloats SimplEnv
env, SimplEnv
env)
    simpl_binds env :: SimplEnv
env (bind :: InBind
bind:binds :: [InBind]
binds) = do { (float :: SimplFloats
float,  env1 :: SimplEnv
env1) <- SimplEnv -> InBind -> SimplM (SimplFloats, SimplEnv)
simpl_bind SimplEnv
env InBind
bind
                                      ; (floats :: SimplFloats
floats, env2 :: SimplEnv
env2) <- SimplEnv -> [InBind] -> SimplM (SimplFloats, SimplEnv)
simpl_binds SimplEnv
env1 [InBind]
binds
                                      ; (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats
float SimplFloats -> SimplFloats -> SimplFloats
`addFloats` SimplFloats
floats, SimplEnv
env2) }

    simpl_bind :: SimplEnv -> InBind -> SimplM (SimplFloats, SimplEnv)
simpl_bind env :: SimplEnv
env (Rec pairs :: [(InBndr, Expr InBndr)]
pairs)
      = SimplEnv
-> TopLevelFlag
-> MaybeJoinCont
-> [(InBndr, Expr InBndr)]
-> SimplM (SimplFloats, SimplEnv)
simplRecBind SimplEnv
env TopLevelFlag
TopLevel MaybeJoinCont
forall a. Maybe a
Nothing [(InBndr, Expr InBndr)]
pairs
    simpl_bind env :: SimplEnv
env (NonRec b :: InBndr
b r :: Expr InBndr
r)
      = do { (env' :: SimplEnv
env', b' :: InBndr
b') <- SimplEnv
-> InBndr -> InBndr -> MaybeJoinCont -> SimplM (SimplEnv, InBndr)
addBndrRules SimplEnv
env InBndr
b (SimplEnv -> InBndr -> InBndr
lookupRecBndr SimplEnv
env InBndr
b) MaybeJoinCont
forall a. Maybe a
Nothing
           ; SimplEnv
-> TopLevelFlag
-> RecFlag
-> MaybeJoinCont
-> InBndr
-> InBndr
-> Expr InBndr
-> SimplM (SimplFloats, SimplEnv)
simplRecOrTopPair SimplEnv
env' TopLevelFlag
TopLevel RecFlag
NonRecursive MaybeJoinCont
forall a. Maybe a
Nothing InBndr
b InBndr
b' Expr InBndr
r }

{-
************************************************************************
*                                                                      *
        Lazy bindings
*                                                                      *
************************************************************************

simplRecBind is used for
        * recursive bindings only
-}

simplRecBind :: SimplEnv -> TopLevelFlag -> MaybeJoinCont
             -> [(InId, InExpr)]
             -> SimplM (SimplFloats, SimplEnv)
simplRecBind :: SimplEnv
-> TopLevelFlag
-> MaybeJoinCont
-> [(InBndr, Expr InBndr)]
-> SimplM (SimplFloats, SimplEnv)
simplRecBind env0 :: SimplEnv
env0 top_lvl :: TopLevelFlag
top_lvl mb_cont :: MaybeJoinCont
mb_cont pairs0 :: [(InBndr, Expr InBndr)]
pairs0
  = do  { (env_with_info :: SimplEnv
env_with_info, triples :: [(InBndr, InBndr, Expr InBndr)]
triples) <- (SimplEnv
 -> (InBndr, Expr InBndr)
 -> SimplM (SimplEnv, (InBndr, InBndr, Expr InBndr)))
-> SimplEnv
-> [(InBndr, Expr InBndr)]
-> SimplM (SimplEnv, [(InBndr, InBndr, Expr InBndr)])
forall (m :: * -> *) acc x y.
Monad m =>
(acc -> x -> m (acc, y)) -> acc -> [x] -> m (acc, [y])
mapAccumLM SimplEnv
-> (InBndr, Expr InBndr)
-> SimplM (SimplEnv, (InBndr, InBndr, Expr InBndr))
add_rules SimplEnv
env0 [(InBndr, Expr InBndr)]
pairs0
        ; (rec_floats :: SimplFloats
rec_floats, env1 :: SimplEnv
env1) <- SimplEnv
-> [(InBndr, InBndr, Expr InBndr)]
-> SimplM (SimplFloats, SimplEnv)
go SimplEnv
env_with_info [(InBndr, InBndr, Expr InBndr)]
triples
        ; (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats -> SimplFloats
mkRecFloats SimplFloats
rec_floats, SimplEnv
env1) }
  where
    add_rules :: SimplEnv -> (InBndr,InExpr) -> SimplM (SimplEnv, (InBndr, OutBndr, InExpr))
        -- Add the (substituted) rules to the binder
    add_rules :: SimplEnv
-> (InBndr, Expr InBndr)
-> SimplM (SimplEnv, (InBndr, InBndr, Expr InBndr))
add_rules env :: SimplEnv
env (bndr :: InBndr
bndr, rhs :: Expr InBndr
rhs)
        = do { (env' :: SimplEnv
env', bndr' :: InBndr
bndr') <- SimplEnv
-> InBndr -> InBndr -> MaybeJoinCont -> SimplM (SimplEnv, InBndr)
addBndrRules SimplEnv
env InBndr
bndr (SimplEnv -> InBndr -> InBndr
lookupRecBndr SimplEnv
env InBndr
bndr) MaybeJoinCont
mb_cont
             ; (SimplEnv, (InBndr, InBndr, Expr InBndr))
-> SimplM (SimplEnv, (InBndr, InBndr, Expr InBndr))
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplEnv
env', (InBndr
bndr, InBndr
bndr', Expr InBndr
rhs)) }

    go :: SimplEnv
-> [(InBndr, InBndr, Expr InBndr)]
-> SimplM (SimplFloats, SimplEnv)
go env :: SimplEnv
env [] = (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplEnv -> SimplFloats
emptyFloats SimplEnv
env, SimplEnv
env)

    go env :: SimplEnv
env ((old_bndr :: InBndr
old_bndr, new_bndr :: InBndr
new_bndr, rhs :: Expr InBndr
rhs) : pairs :: [(InBndr, InBndr, Expr InBndr)]
pairs)
        = do { (float :: SimplFloats
float, env1 :: SimplEnv
env1) <- SimplEnv
-> TopLevelFlag
-> RecFlag
-> MaybeJoinCont
-> InBndr
-> InBndr
-> Expr InBndr
-> SimplM (SimplFloats, SimplEnv)
simplRecOrTopPair SimplEnv
env TopLevelFlag
top_lvl RecFlag
Recursive MaybeJoinCont
mb_cont
                                                  InBndr
old_bndr InBndr
new_bndr Expr InBndr
rhs
             ; (floats :: SimplFloats
floats, env2 :: SimplEnv
env2) <- SimplEnv
-> [(InBndr, InBndr, Expr InBndr)]
-> SimplM (SimplFloats, SimplEnv)
go SimplEnv
env1 [(InBndr, InBndr, Expr InBndr)]
pairs
             ; (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats
float SimplFloats -> SimplFloats -> SimplFloats
`addFloats` SimplFloats
floats, SimplEnv
env2) }

{-
simplOrTopPair is used for
        * recursive bindings (whether top level or not)
        * top-level non-recursive bindings

It assumes the binder has already been simplified, but not its IdInfo.
-}

simplRecOrTopPair :: SimplEnv
                  -> TopLevelFlag -> RecFlag -> MaybeJoinCont
                  -> InId -> OutBndr -> InExpr  -- Binder and rhs
                  -> SimplM (SimplFloats, SimplEnv)

simplRecOrTopPair :: SimplEnv
-> TopLevelFlag
-> RecFlag
-> MaybeJoinCont
-> InBndr
-> InBndr
-> Expr InBndr
-> SimplM (SimplFloats, SimplEnv)
simplRecOrTopPair env :: SimplEnv
env top_lvl :: TopLevelFlag
top_lvl is_rec :: RecFlag
is_rec mb_cont :: MaybeJoinCont
mb_cont old_bndr :: InBndr
old_bndr new_bndr :: InBndr
new_bndr rhs :: Expr InBndr
rhs
  | Just env' :: SimplEnv
env' <- SimplEnv
-> TopLevelFlag
-> InBndr
-> Expr InBndr
-> SimplEnv
-> Maybe SimplEnv
preInlineUnconditionally SimplEnv
env TopLevelFlag
top_lvl InBndr
old_bndr Expr InBndr
rhs SimplEnv
env
  = {-#SCC "simplRecOrTopPair-pre-inline-uncond" #-}
    [Char]
-> SimplM (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv)
forall a. [Char] -> a -> a
trace_bind "pre-inline-uncond" (SimplM (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv))
-> SimplM (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv)
forall a b. (a -> b) -> a -> b
$
    do { Tick -> SimplM ()
tick (InBndr -> Tick
PreInlineUnconditionally InBndr
old_bndr)
       ; (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv)
forall (m :: * -> *) a. Monad m => a -> m a
return ( SimplEnv -> SimplFloats
emptyFloats SimplEnv
env, SimplEnv
env' ) }

  | Just cont :: SimplCont
cont <- MaybeJoinCont
mb_cont
  = {-#SCC "simplRecOrTopPair-join" #-}
    ASSERT( isNotTopLevel top_lvl && isJoinId new_bndr )
    [Char]
-> SimplM (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv)
forall a. [Char] -> a -> a
trace_bind "join" (SimplM (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv))
-> SimplM (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv)
forall a b. (a -> b) -> a -> b
$
    SimplEnv
-> SimplCont
-> InBndr
-> InBndr
-> Expr InBndr
-> SimplEnv
-> SimplM (SimplFloats, SimplEnv)
simplJoinBind SimplEnv
env SimplCont
cont InBndr
old_bndr InBndr
new_bndr Expr InBndr
rhs SimplEnv
env

  | Bool
otherwise
  = {-#SCC "simplRecOrTopPair-normal" #-}
    [Char]
-> SimplM (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv)
forall a. [Char] -> a -> a
trace_bind "normal" (SimplM (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv))
-> SimplM (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv)
forall a b. (a -> b) -> a -> b
$
    SimplEnv
-> TopLevelFlag
-> RecFlag
-> InBndr
-> InBndr
-> Expr InBndr
-> SimplEnv
-> SimplM (SimplFloats, SimplEnv)
simplLazyBind SimplEnv
env TopLevelFlag
top_lvl RecFlag
is_rec InBndr
old_bndr InBndr
new_bndr Expr InBndr
rhs SimplEnv
env

  where
    dflags :: DynFlags
dflags = SimplEnv -> DynFlags
seDynFlags SimplEnv
env

    -- trace_bind emits a trace for each top-level binding, which
    -- helps to locate the tracing for inlining and rule firing
    trace_bind :: [Char] -> a -> a
trace_bind what :: [Char]
what thing_inside :: a
thing_inside
      | Bool -> Bool
not (DumpFlag -> DynFlags -> Bool
dopt DumpFlag
Opt_D_verbose_core2core DynFlags
dflags)
      = a
thing_inside
      | Bool
otherwise
      = [Char] -> SDoc -> a -> a
forall a. [Char] -> SDoc -> a -> a
pprTrace ("SimplBind " [Char] -> [Char] -> [Char]
forall a. [a] -> [a] -> [a]
++ [Char]
what) (InBndr -> SDoc
forall a. Outputable a => a -> SDoc
ppr InBndr
old_bndr) a
thing_inside

--------------------------
simplLazyBind :: SimplEnv
              -> TopLevelFlag -> RecFlag
              -> InId -> OutId          -- Binder, both pre-and post simpl
                                        -- Not a JoinId
                                        -- The OutId has IdInfo, except arity, unfolding
                                        -- Ids only, no TyVars
              -> InExpr -> SimplEnv     -- The RHS and its environment
              -> SimplM (SimplFloats, SimplEnv)
-- Precondition: not a JoinId
-- Precondition: rhs obeys the let/app invariant
-- NOT used for JoinIds
simplLazyBind :: SimplEnv
-> TopLevelFlag
-> RecFlag
-> InBndr
-> InBndr
-> Expr InBndr
-> SimplEnv
-> SimplM (SimplFloats, SimplEnv)
simplLazyBind env :: SimplEnv
env top_lvl :: TopLevelFlag
top_lvl is_rec :: RecFlag
is_rec bndr :: InBndr
bndr bndr1 :: InBndr
bndr1 rhs :: Expr InBndr
rhs rhs_se :: SimplEnv
rhs_se
  = ASSERT( isId bndr )
    ASSERT2( not (isJoinId bndr), ppr bndr )
    -- pprTrace "simplLazyBind" ((ppr bndr <+> ppr bndr1) $$ ppr rhs $$ ppr (seIdSubst rhs_se)) $
    do  { let   rhs_env :: SimplEnv
rhs_env     = SimplEnv
rhs_se SimplEnv -> SimplEnv -> SimplEnv
`setInScopeFromE` SimplEnv
env
                (tvs :: [InBndr]
tvs, body :: Expr InBndr
body) = case Expr InBndr -> ([InBndr], [InBndr], Expr InBndr)
collectTyAndValBinders Expr InBndr
rhs of
                                (tvs :: [InBndr]
tvs, [], body :: Expr InBndr
body)
                                  | Expr InBndr -> Bool
forall b. Expr b -> Bool
surely_not_lam Expr InBndr
body -> ([InBndr]
tvs, Expr InBndr
body)
                                _                       -> ([], Expr InBndr
rhs)

                surely_not_lam :: Expr b -> Bool
surely_not_lam (Lam {})     = Bool
False
                surely_not_lam (Tick t :: Tickish InBndr
t e :: Expr b
e)
                  | Bool -> Bool
not (Tickish InBndr -> Bool
forall id. Tickish id -> Bool
tickishFloatable Tickish InBndr
t) = Expr b -> Bool
surely_not_lam Expr b
e
                   -- eta-reduction could float
                surely_not_lam _            = Bool
True
                        -- Do not do the "abstract tyvar" thing if there's
                        -- a lambda inside, because it defeats eta-reduction
                        --    f = /\a. \x. g a x
                        -- should eta-reduce.


        ; (body_env :: SimplEnv
body_env, tvs' :: [InBndr]
tvs') <- {-#SCC "simplBinders" #-} SimplEnv -> [InBndr] -> SimplM (SimplEnv, [InBndr])
simplBinders SimplEnv
rhs_env [InBndr]
tvs
                -- See Note [Floating and type abstraction] in SimplUtils

        -- Simplify the RHS
        ; let rhs_cont :: SimplCont
rhs_cont = OutType -> SimplCont
mkRhsStop (SimplEnv -> OutType -> OutType
substTy SimplEnv
body_env (Expr InBndr -> OutType
exprType Expr InBndr
body))
        ; (body_floats0 :: SimplFloats
body_floats0, body0 :: Expr InBndr
body0) <- {-#SCC "simplExprF" #-} SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF SimplEnv
body_env Expr InBndr
body SimplCont
rhs_cont

              -- Never float join-floats out of a non-join let-binding
              -- So wrap the body in the join-floats right now
              -- Hence: body_floats1 consists only of let-floats
        ; let (body_floats1 :: SimplFloats
body_floats1, body1 :: Expr InBndr
body1) = SimplFloats -> Expr InBndr -> (SimplFloats, Expr InBndr)
wrapJoinFloatsX SimplFloats
body_floats0 Expr InBndr
body0

        -- ANF-ise a constructor or PAP rhs
        -- We get at most one float per argument here
        ; (let_floats :: LetFloats
let_floats, body2 :: Expr InBndr
body2) <- {-#SCC "prepareRhs" #-} SimplMode
-> TopLevelFlag
-> FastString
-> IdInfo
-> Expr InBndr
-> SimplM (LetFloats, Expr InBndr)
prepareRhs (SimplEnv -> SimplMode
getMode SimplEnv
env) TopLevelFlag
top_lvl
                                            (InBndr -> FastString
forall a. NamedThing a => a -> FastString
getOccFS InBndr
bndr1) (HasDebugCallStack => InBndr -> IdInfo
InBndr -> IdInfo
idInfo InBndr
bndr1) Expr InBndr
body1
        ; let body_floats2 :: SimplFloats
body_floats2 = SimplFloats
body_floats1 SimplFloats -> LetFloats -> SimplFloats
`addLetFloats` LetFloats
let_floats

        ; (rhs_floats :: SimplFloats
rhs_floats, rhs' :: Expr InBndr
rhs')
            <-  if Bool -> Bool
not (TopLevelFlag
-> RecFlag -> Bool -> SimplFloats -> Expr InBndr -> Bool
doFloatFromRhs TopLevelFlag
top_lvl RecFlag
is_rec Bool
False SimplFloats
body_floats2 Expr InBndr
body2)
                then                    -- No floating, revert to body1
                     {-#SCC "simplLazyBind-no-floating" #-}
                     do { Expr InBndr
rhs' <- SimplEnv
-> [InBndr] -> Expr InBndr -> SimplCont -> SimplM (Expr InBndr)
mkLam SimplEnv
env [InBndr]
tvs' (SimplFloats -> Expr InBndr -> Expr InBndr
wrapFloats SimplFloats
body_floats2 Expr InBndr
body1) SimplCont
rhs_cont
                        ; (SimplFloats, Expr InBndr) -> SimplM (SimplFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplEnv -> SimplFloats
emptyFloats SimplEnv
env, Expr InBndr
rhs') }

                else if [InBndr] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [InBndr]
tvs then   -- Simple floating
                     {-#SCC "simplLazyBind-simple-floating" #-}
                     do { Tick -> SimplM ()
tick Tick
LetFloatFromLet
                        ; (SimplFloats, Expr InBndr) -> SimplM (SimplFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats
body_floats2, Expr InBndr
body2) }

                else                    -- Do type-abstraction first
                     {-#SCC "simplLazyBind-type-abstraction-first" #-}
                     do { Tick -> SimplM ()
tick Tick
LetFloatFromLet
                        ; (poly_binds :: [InBind]
poly_binds, body3 :: Expr InBndr
body3) <- DynFlags
-> TopLevelFlag
-> [InBndr]
-> SimplFloats
-> Expr InBndr
-> SimplM ([InBind], Expr InBndr)
abstractFloats (SimplEnv -> DynFlags
seDynFlags SimplEnv
env) TopLevelFlag
top_lvl
                                                                [InBndr]
tvs' SimplFloats
body_floats2 Expr InBndr
body2
                        ; let floats :: SimplFloats
floats = (SimplFloats -> InBind -> SimplFloats)
-> SimplFloats -> [InBind] -> SimplFloats
forall (t :: * -> *) b a.
Foldable t =>
(b -> a -> b) -> b -> t a -> b
foldl' SimplFloats -> InBind -> SimplFloats
extendFloats (SimplEnv -> SimplFloats
emptyFloats SimplEnv
env) [InBind]
poly_binds
                        ; Expr InBndr
rhs' <- SimplEnv
-> [InBndr] -> Expr InBndr -> SimplCont -> SimplM (Expr InBndr)
mkLam SimplEnv
env [InBndr]
tvs' Expr InBndr
body3 SimplCont
rhs_cont
                        ; (SimplFloats, Expr InBndr) -> SimplM (SimplFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats
floats, Expr InBndr
rhs') }

        ; (bind_float :: SimplFloats
bind_float, env2 :: SimplEnv
env2) <- SimplEnv
-> TopLevelFlag
-> MaybeJoinCont
-> InBndr
-> InBndr
-> Expr InBndr
-> SimplM (SimplFloats, SimplEnv)
completeBind (SimplEnv
env SimplEnv -> SimplFloats -> SimplEnv
`setInScopeFromF` SimplFloats
rhs_floats)
                                             TopLevelFlag
top_lvl MaybeJoinCont
forall a. Maybe a
Nothing InBndr
bndr InBndr
bndr1 Expr InBndr
rhs'
        ; (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats
rhs_floats SimplFloats -> SimplFloats -> SimplFloats
`addFloats` SimplFloats
bind_float, SimplEnv
env2) }

--------------------------
simplJoinBind :: SimplEnv
              -> SimplCont
              -> InId -> OutId          -- Binder, both pre-and post simpl
                                        -- The OutId has IdInfo, except arity,
                                        --   unfolding
              -> InExpr -> SimplEnv     -- The right hand side and its env
              -> SimplM (SimplFloats, SimplEnv)
simplJoinBind :: SimplEnv
-> SimplCont
-> InBndr
-> InBndr
-> Expr InBndr
-> SimplEnv
-> SimplM (SimplFloats, SimplEnv)
simplJoinBind env :: SimplEnv
env cont :: SimplCont
cont old_bndr :: InBndr
old_bndr new_bndr :: InBndr
new_bndr rhs :: Expr InBndr
rhs rhs_se :: SimplEnv
rhs_se
  = do  { let rhs_env :: SimplEnv
rhs_env = SimplEnv
rhs_se SimplEnv -> SimplEnv -> SimplEnv
`setInScopeFromE` SimplEnv
env
        ; Expr InBndr
rhs' <- SimplEnv
-> InBndr -> Expr InBndr -> SimplCont -> SimplM (Expr InBndr)
simplJoinRhs SimplEnv
rhs_env InBndr
old_bndr Expr InBndr
rhs SimplCont
cont
        ; SimplEnv
-> TopLevelFlag
-> MaybeJoinCont
-> InBndr
-> InBndr
-> Expr InBndr
-> SimplM (SimplFloats, SimplEnv)
completeBind SimplEnv
env TopLevelFlag
NotTopLevel (SimplCont -> MaybeJoinCont
forall a. a -> Maybe a
Just SimplCont
cont) InBndr
old_bndr InBndr
new_bndr Expr InBndr
rhs' }

--------------------------
simplNonRecX :: SimplEnv
             -> InId            -- Old binder; not a JoinId
             -> OutExpr         -- Simplified RHS
             -> SimplM (SimplFloats, SimplEnv)
-- A specialised variant of simplNonRec used when the RHS is already
-- simplified, notably in knownCon.  It uses case-binding where necessary.
--
-- Precondition: rhs satisfies the let/app invariant

simplNonRecX :: SimplEnv -> InBndr -> Expr InBndr -> SimplM (SimplFloats, SimplEnv)
simplNonRecX env :: SimplEnv
env bndr :: InBndr
bndr new_rhs :: Expr InBndr
new_rhs
  | ASSERT2( not (isJoinId bndr), ppr bndr )
    InBndr -> Bool
isDeadBinder InBndr
bndr   -- Not uncommon; e.g. case (a,b) of c { (p,q) -> p }
  = (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplEnv -> SimplFloats
emptyFloats SimplEnv
env, SimplEnv
env)    --  Here c is dead, and we avoid
                                         --  creating the binding c = (a,b)

  | Coercion co :: Coercion
co <- Expr InBndr
new_rhs
  = (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplEnv -> SimplFloats
emptyFloats SimplEnv
env, SimplEnv -> InBndr -> Coercion -> SimplEnv
extendCvSubst SimplEnv
env InBndr
bndr Coercion
co)

  | Bool
otherwise
  = do  { (env' :: SimplEnv
env', bndr' :: InBndr
bndr') <- SimplEnv -> InBndr -> SimplM (SimplEnv, InBndr)
simplBinder SimplEnv
env InBndr
bndr
        ; TopLevelFlag
-> SimplEnv
-> Bool
-> InBndr
-> InBndr
-> Expr InBndr
-> SimplM (SimplFloats, SimplEnv)
completeNonRecX TopLevelFlag
NotTopLevel SimplEnv
env' (InBndr -> Bool
isStrictId InBndr
bndr) InBndr
bndr InBndr
bndr' Expr InBndr
new_rhs }
                -- simplNonRecX is only used for NotTopLevel things

--------------------------
completeNonRecX :: TopLevelFlag -> SimplEnv
                -> Bool
                -> InId                 -- Old binder; not a JoinId
                -> OutId                -- New binder
                -> OutExpr              -- Simplified RHS
                -> SimplM (SimplFloats, SimplEnv)    -- The new binding is in the floats
-- Precondition: rhs satisfies the let/app invariant
--               See Note [CoreSyn let/app invariant] in CoreSyn

completeNonRecX :: TopLevelFlag
-> SimplEnv
-> Bool
-> InBndr
-> InBndr
-> Expr InBndr
-> SimplM (SimplFloats, SimplEnv)
completeNonRecX top_lvl :: TopLevelFlag
top_lvl env :: SimplEnv
env is_strict :: Bool
is_strict old_bndr :: InBndr
old_bndr new_bndr :: InBndr
new_bndr new_rhs :: Expr InBndr
new_rhs
  = ASSERT2( not (isJoinId new_bndr), ppr new_bndr )
    do  { (prepd_floats :: LetFloats
prepd_floats, rhs1 :: Expr InBndr
rhs1) <- SimplMode
-> TopLevelFlag
-> FastString
-> IdInfo
-> Expr InBndr
-> SimplM (LetFloats, Expr InBndr)
prepareRhs (SimplEnv -> SimplMode
getMode SimplEnv
env) TopLevelFlag
top_lvl (InBndr -> FastString
forall a. NamedThing a => a -> FastString
getOccFS InBndr
new_bndr)
                                             (HasDebugCallStack => InBndr -> IdInfo
InBndr -> IdInfo
idInfo InBndr
new_bndr) Expr InBndr
new_rhs
        ; let floats :: SimplFloats
floats = SimplEnv -> SimplFloats
emptyFloats SimplEnv
env SimplFloats -> LetFloats -> SimplFloats
`addLetFloats` LetFloats
prepd_floats
        ; (rhs_floats :: SimplFloats
rhs_floats, rhs2 :: Expr InBndr
rhs2) <-
                if TopLevelFlag
-> RecFlag -> Bool -> SimplFloats -> Expr InBndr -> Bool
doFloatFromRhs TopLevelFlag
NotTopLevel RecFlag
NonRecursive Bool
is_strict SimplFloats
floats Expr InBndr
rhs1
                then    -- Add the floats to the main env
                     do { Tick -> SimplM ()
tick Tick
LetFloatFromLet
                        ; (SimplFloats, Expr InBndr) -> SimplM (SimplFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats
floats, Expr InBndr
rhs1) }
                else    -- Do not float; wrap the floats around the RHS
                     (SimplFloats, Expr InBndr) -> SimplM (SimplFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplEnv -> SimplFloats
emptyFloats SimplEnv
env, SimplFloats -> Expr InBndr -> Expr InBndr
wrapFloats SimplFloats
floats Expr InBndr
rhs1)

        ; (bind_float :: SimplFloats
bind_float, env2 :: SimplEnv
env2) <- SimplEnv
-> TopLevelFlag
-> MaybeJoinCont
-> InBndr
-> InBndr
-> Expr InBndr
-> SimplM (SimplFloats, SimplEnv)
completeBind (SimplEnv
env SimplEnv -> SimplFloats -> SimplEnv
`setInScopeFromF` SimplFloats
rhs_floats)
                                             TopLevelFlag
NotTopLevel MaybeJoinCont
forall a. Maybe a
Nothing
                                             InBndr
old_bndr InBndr
new_bndr Expr InBndr
rhs2
        ; (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats
rhs_floats SimplFloats -> SimplFloats -> SimplFloats
`addFloats` SimplFloats
bind_float, SimplEnv
env2) }


{- *********************************************************************
*                                                                      *
           prepareRhs, makeTrivial
*                                                                      *
************************************************************************

Note [prepareRhs]
~~~~~~~~~~~~~~~~~
prepareRhs takes a putative RHS, checks whether it's a PAP or
constructor application and, if so, converts it to ANF, so that the
resulting thing can be inlined more easily.  Thus
        x = (f a, g b)
becomes
        t1 = f a
        t2 = g b
        x = (t1,t2)

We also want to deal well cases like this
        v = (f e1 `cast` co) e2
Here we want to make e1,e2 trivial and get
        x1 = e1; x2 = e2; v = (f x1 `cast` co) v2
That's what the 'go' loop in prepareRhs does
-}

prepareRhs :: SimplMode -> TopLevelFlag
           -> FastString   -- Base for any new variables
           -> IdInfo       -- IdInfo for the LHS of this binding
           -> OutExpr
           -> SimplM (LetFloats, OutExpr)
-- Transforms a RHS into a better RHS by adding floats
-- e.g        x = Just e
-- becomes    a = e
--            x = Just a
-- See Note [prepareRhs]
prepareRhs :: SimplMode
-> TopLevelFlag
-> FastString
-> IdInfo
-> Expr InBndr
-> SimplM (LetFloats, Expr InBndr)
prepareRhs mode :: SimplMode
mode top_lvl :: TopLevelFlag
top_lvl occ :: FastString
occ info :: IdInfo
info (Cast rhs :: Expr InBndr
rhs co :: Coercion
co)  -- Note [Float coercions]
  | Pair ty1 :: OutType
ty1 _ty2 :: OutType
_ty2 <- Coercion -> Pair OutType
coercionKind Coercion
co         -- Do *not* do this if rhs has an unlifted type
  , Bool -> Bool
not (HasDebugCallStack => OutType -> Bool
OutType -> Bool
isUnliftedType OutType
ty1)                 -- see Note [Float coercions (unlifted)]
  = do  { (floats :: LetFloats
floats, rhs' :: Expr InBndr
rhs') <- SimplMode
-> TopLevelFlag
-> FastString
-> IdInfo
-> Expr InBndr
-> SimplM (LetFloats, Expr InBndr)
makeTrivialWithInfo SimplMode
mode TopLevelFlag
top_lvl FastString
occ IdInfo
sanitised_info Expr InBndr
rhs
        ; (LetFloats, Expr InBndr) -> SimplM (LetFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (LetFloats
floats, Expr InBndr -> Coercion -> Expr InBndr
forall b. Expr b -> Coercion -> Expr b
Cast Expr InBndr
rhs' Coercion
co) }
  where
    sanitised_info :: IdInfo
sanitised_info = IdInfo
vanillaIdInfo IdInfo -> StrictSig -> IdInfo
`setStrictnessInfo` IdInfo -> StrictSig
strictnessInfo IdInfo
info
                                   IdInfo -> Demand -> IdInfo
`setDemandInfo`     IdInfo -> Demand
demandInfo IdInfo
info

prepareRhs mode :: SimplMode
mode top_lvl :: TopLevelFlag
top_lvl occ :: FastString
occ _ rhs0 :: Expr InBndr
rhs0
  = do  { (_is_exp :: Bool
_is_exp, floats :: LetFloats
floats, rhs1 :: Expr InBndr
rhs1) <- Int -> Expr InBndr -> SimplM (Bool, LetFloats, Expr InBndr)
go 0 Expr InBndr
rhs0
        ; (LetFloats, Expr InBndr) -> SimplM (LetFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (LetFloats
floats, Expr InBndr
rhs1) }
  where
    go :: Int -> OutExpr -> SimplM (Bool, LetFloats, OutExpr)
    go :: Int -> Expr InBndr -> SimplM (Bool, LetFloats, Expr InBndr)
go n_val_args :: Int
n_val_args (Cast rhs :: Expr InBndr
rhs co :: Coercion
co)
        = do { (is_exp :: Bool
is_exp, floats :: LetFloats
floats, rhs' :: Expr InBndr
rhs') <- Int -> Expr InBndr -> SimplM (Bool, LetFloats, Expr InBndr)
go Int
n_val_args Expr InBndr
rhs
             ; (Bool, LetFloats, Expr InBndr)
-> SimplM (Bool, LetFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (Bool
is_exp, LetFloats
floats, Expr InBndr -> Coercion -> Expr InBndr
forall b. Expr b -> Coercion -> Expr b
Cast Expr InBndr
rhs' Coercion
co) }
    go n_val_args :: Int
n_val_args (App fun :: Expr InBndr
fun (Type ty :: OutType
ty))
        = do { (is_exp :: Bool
is_exp, floats :: LetFloats
floats, rhs' :: Expr InBndr
rhs') <- Int -> Expr InBndr -> SimplM (Bool, LetFloats, Expr InBndr)
go Int
n_val_args Expr InBndr
fun
             ; (Bool, LetFloats, Expr InBndr)
-> SimplM (Bool, LetFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (Bool
is_exp, LetFloats
floats, Expr InBndr -> Expr InBndr -> Expr InBndr
forall b. Expr b -> Expr b -> Expr b
App Expr InBndr
rhs' (OutType -> Expr InBndr
forall b. OutType -> Expr b
Type OutType
ty)) }
    go n_val_args :: Int
n_val_args (App fun :: Expr InBndr
fun arg :: Expr InBndr
arg)
        = do { (is_exp :: Bool
is_exp, floats1 :: LetFloats
floats1, fun' :: Expr InBndr
fun') <- Int -> Expr InBndr -> SimplM (Bool, LetFloats, Expr InBndr)
go (Int
n_val_argsInt -> Int -> Int
forall a. Num a => a -> a -> a
+1) Expr InBndr
fun
             ; case Bool
is_exp of
                False -> (Bool, LetFloats, Expr InBndr)
-> SimplM (Bool, LetFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (Bool
False, LetFloats
emptyLetFloats, Expr InBndr -> Expr InBndr -> Expr InBndr
forall b. Expr b -> Expr b -> Expr b
App Expr InBndr
fun Expr InBndr
arg)
                True  -> do { (floats2 :: LetFloats
floats2, arg' :: Expr InBndr
arg') <- SimplMode
-> TopLevelFlag
-> FastString
-> Expr InBndr
-> SimplM (LetFloats, Expr InBndr)
makeTrivial SimplMode
mode TopLevelFlag
top_lvl FastString
occ Expr InBndr
arg
                            ; (Bool, LetFloats, Expr InBndr)
-> SimplM (Bool, LetFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (Bool
True, LetFloats
floats1 LetFloats -> LetFloats -> LetFloats
`addLetFlts` LetFloats
floats2, Expr InBndr -> Expr InBndr -> Expr InBndr
forall b. Expr b -> Expr b -> Expr b
App Expr InBndr
fun' Expr InBndr
arg') } }
    go n_val_args :: Int
n_val_args (Var fun :: InBndr
fun)
        = (Bool, LetFloats, Expr InBndr)
-> SimplM (Bool, LetFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (Bool
is_exp, LetFloats
emptyLetFloats, InBndr -> Expr InBndr
forall b. InBndr -> Expr b
Var InBndr
fun)
        where
          is_exp :: Bool
is_exp = CheapAppFun
isExpandableApp InBndr
fun Int
n_val_args   -- The fun a constructor or PAP
                        -- See Note [CONLIKE pragma] in BasicTypes
                        -- The definition of is_exp should match that in
                        -- OccurAnal.occAnalApp

    go n_val_args :: Int
n_val_args (Tick t :: Tickish InBndr
t rhs :: Expr InBndr
rhs)
        -- We want to be able to float bindings past this
        -- tick. Non-scoping ticks don't care.
        | Tickish InBndr -> TickishScoping
forall id. Tickish id -> TickishScoping
tickishScoped Tickish InBndr
t TickishScoping -> TickishScoping -> Bool
forall a. Eq a => a -> a -> Bool
== TickishScoping
NoScope
        = do { (is_exp :: Bool
is_exp, floats :: LetFloats
floats, rhs' :: Expr InBndr
rhs') <- Int -> Expr InBndr -> SimplM (Bool, LetFloats, Expr InBndr)
go Int
n_val_args Expr InBndr
rhs
             ; (Bool, LetFloats, Expr InBndr)
-> SimplM (Bool, LetFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (Bool
is_exp, LetFloats
floats, Tickish InBndr -> Expr InBndr -> Expr InBndr
forall b. Tickish InBndr -> Expr b -> Expr b
Tick Tickish InBndr
t Expr InBndr
rhs') }

        -- On the other hand, for scoping ticks we need to be able to
        -- copy them on the floats, which in turn is only allowed if
        -- we can obtain non-counting ticks.
        | (Bool -> Bool
not (Tickish InBndr -> Bool
forall id. Tickish id -> Bool
tickishCounts Tickish InBndr
t) Bool -> Bool -> Bool
|| Tickish InBndr -> Bool
forall id. Tickish id -> Bool
tickishCanSplit Tickish InBndr
t)
        = do { (is_exp :: Bool
is_exp, floats :: LetFloats
floats, rhs' :: Expr InBndr
rhs') <- Int -> Expr InBndr -> SimplM (Bool, LetFloats, Expr InBndr)
go Int
n_val_args Expr InBndr
rhs
             ; let tickIt :: (a, Expr InBndr) -> (a, Expr InBndr)
tickIt (id :: a
id, expr :: Expr InBndr
expr) = (a
id, Tickish InBndr -> Expr InBndr -> Expr InBndr
mkTick (Tickish InBndr -> Tickish InBndr
forall id. Tickish id -> Tickish id
mkNoCount Tickish InBndr
t) Expr InBndr
expr)
                   floats' :: LetFloats
floats' = LetFloats
-> ((InBndr, Expr InBndr) -> (InBndr, Expr InBndr)) -> LetFloats
mapLetFloats LetFloats
floats (InBndr, Expr InBndr) -> (InBndr, Expr InBndr)
forall a. (a, Expr InBndr) -> (a, Expr InBndr)
tickIt
             ; (Bool, LetFloats, Expr InBndr)
-> SimplM (Bool, LetFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (Bool
is_exp, LetFloats
floats', Tickish InBndr -> Expr InBndr -> Expr InBndr
forall b. Tickish InBndr -> Expr b -> Expr b
Tick Tickish InBndr
t Expr InBndr
rhs') }

    go _ other :: Expr InBndr
other
        = (Bool, LetFloats, Expr InBndr)
-> SimplM (Bool, LetFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (Bool
False, LetFloats
emptyLetFloats, Expr InBndr
other)

{-
Note [Float coercions]
~~~~~~~~~~~~~~~~~~~~~~
When we find the binding
        x = e `cast` co
we'd like to transform it to
        x' = e
        x = x `cast` co         -- A trivial binding
There's a chance that e will be a constructor application or function, or something
like that, so moving the coercion to the usage site may well cancel the coercions
and lead to further optimisation.  Example:

     data family T a :: *
     data instance T Int = T Int

     foo :: Int -> Int -> Int
     foo m n = ...
        where
          x = T m
          go 0 = 0
          go n = case x of { T m -> go (n-m) }
                -- This case should optimise

Note [Preserve strictness when floating coercions]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In the Note [Float coercions] transformation, keep the strictness info.
Eg
        f = e `cast` co    -- f has strictness SSL
When we transform to
        f' = e             -- f' also has strictness SSL
        f = f' `cast` co   -- f still has strictness SSL

Its not wrong to drop it on the floor, but better to keep it.

Note [Float coercions (unlifted)]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
BUT don't do [Float coercions] if 'e' has an unlifted type.
This *can* happen:

     foo :: Int = (error (# Int,Int #) "urk")
                  `cast` CoUnsafe (# Int,Int #) Int

If do the makeTrivial thing to the error call, we'll get
    foo = case error (# Int,Int #) "urk" of v -> v `cast` ...
But 'v' isn't in scope!

These strange casts can happen as a result of case-of-case
        bar = case (case x of { T -> (# 2,3 #); F -> error "urk" }) of
                (# p,q #) -> p+q
-}

makeTrivialArg :: SimplMode -> ArgSpec -> SimplM (LetFloats, ArgSpec)
makeTrivialArg :: SimplMode -> ArgSpec -> SimplM (LetFloats, ArgSpec)
makeTrivialArg mode :: SimplMode
mode (ValArg e :: Expr InBndr
e)
  = do { (floats :: LetFloats
floats, e' :: Expr InBndr
e') <- SimplMode
-> TopLevelFlag
-> FastString
-> Expr InBndr
-> SimplM (LetFloats, Expr InBndr)
makeTrivial SimplMode
mode TopLevelFlag
NotTopLevel ([Char] -> FastString
fsLit "arg") Expr InBndr
e
       ; (LetFloats, ArgSpec) -> SimplM (LetFloats, ArgSpec)
forall (m :: * -> *) a. Monad m => a -> m a
return (LetFloats
floats, Expr InBndr -> ArgSpec
ValArg Expr InBndr
e') }
makeTrivialArg _ arg :: ArgSpec
arg
  = (LetFloats, ArgSpec) -> SimplM (LetFloats, ArgSpec)
forall (m :: * -> *) a. Monad m => a -> m a
return (LetFloats
emptyLetFloats, ArgSpec
arg)  -- CastBy, TyArg

makeTrivial :: SimplMode -> TopLevelFlag
            -> FastString  -- ^ A "friendly name" to build the new binder from
            -> OutExpr     -- ^ This expression satisfies the let/app invariant
            -> SimplM (LetFloats, OutExpr)
-- Binds the expression to a variable, if it's not trivial, returning the variable
makeTrivial :: SimplMode
-> TopLevelFlag
-> FastString
-> Expr InBndr
-> SimplM (LetFloats, Expr InBndr)
makeTrivial mode :: SimplMode
mode top_lvl :: TopLevelFlag
top_lvl context :: FastString
context expr :: Expr InBndr
expr
 = SimplMode
-> TopLevelFlag
-> FastString
-> IdInfo
-> Expr InBndr
-> SimplM (LetFloats, Expr InBndr)
makeTrivialWithInfo SimplMode
mode TopLevelFlag
top_lvl FastString
context IdInfo
vanillaIdInfo Expr InBndr
expr

makeTrivialWithInfo :: SimplMode -> TopLevelFlag
                    -> FastString  -- ^ a "friendly name" to build the new binder from
                    -> IdInfo
                    -> OutExpr     -- ^ This expression satisfies the let/app invariant
                    -> SimplM (LetFloats, OutExpr)
-- Propagate strictness and demand info to the new binder
-- Note [Preserve strictness when floating coercions]
-- Returned SimplEnv has same substitution as incoming one
makeTrivialWithInfo :: SimplMode
-> TopLevelFlag
-> FastString
-> IdInfo
-> Expr InBndr
-> SimplM (LetFloats, Expr InBndr)
makeTrivialWithInfo mode :: SimplMode
mode top_lvl :: TopLevelFlag
top_lvl occ_fs :: FastString
occ_fs info :: IdInfo
info expr :: Expr InBndr
expr
  | Expr InBndr -> Bool
exprIsTrivial Expr InBndr
expr                          -- Already trivial
  Bool -> Bool -> Bool
|| Bool -> Bool
not (TopLevelFlag -> Expr InBndr -> OutType -> Bool
bindingOk TopLevelFlag
top_lvl Expr InBndr
expr OutType
expr_ty)       -- Cannot trivialise
                                                --   See Note [Cannot trivialise]
  = (LetFloats, Expr InBndr) -> SimplM (LetFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (LetFloats
emptyLetFloats, Expr InBndr
expr)

  | Bool
otherwise
  = do  { (floats :: LetFloats
floats, expr1 :: Expr InBndr
expr1) <- SimplMode
-> TopLevelFlag
-> FastString
-> IdInfo
-> Expr InBndr
-> SimplM (LetFloats, Expr InBndr)
prepareRhs SimplMode
mode TopLevelFlag
top_lvl FastString
occ_fs IdInfo
info Expr InBndr
expr
        ; if   Expr InBndr -> Bool
exprIsTrivial Expr InBndr
expr1  -- See Note [Trivial after prepareRhs]
          then (LetFloats, Expr InBndr) -> SimplM (LetFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (LetFloats
floats, Expr InBndr
expr1)
          else do
        { Unique
uniq <- SimplM Unique
forall (m :: * -> *). MonadUnique m => m Unique
getUniqueM
        ; let name :: Name
name = Unique -> FastString -> Name
mkSystemVarName Unique
uniq FastString
occ_fs
              var :: InBndr
var  = Name -> OutType -> IdInfo -> InBndr
mkLocalIdOrCoVarWithInfo Name
name OutType
expr_ty IdInfo
info

        -- Now something very like completeBind,
        -- but without the postInlineUnconditinoally part
        ; (arity :: Int
arity, is_bot :: Bool
is_bot, expr2 :: Expr InBndr
expr2) <- SimplMode
-> InBndr -> Expr InBndr -> SimplM (Int, Bool, Expr InBndr)
tryEtaExpandRhs SimplMode
mode InBndr
var Expr InBndr
expr1
        ; Unfolding
unf <- DynFlags
-> TopLevelFlag
-> UnfoldingSource
-> InBndr
-> Expr InBndr
-> SimplM Unfolding
mkLetUnfolding (SimplMode -> DynFlags
sm_dflags SimplMode
mode) TopLevelFlag
top_lvl UnfoldingSource
InlineRhs InBndr
var Expr InBndr
expr2

        ; let final_id :: InBndr
final_id = InBndr -> Int -> Bool -> Unfolding -> InBndr
addLetBndrInfo InBndr
var Int
arity Bool
is_bot Unfolding
unf
              bind :: InBind
bind     = InBndr -> Expr InBndr -> InBind
forall b. b -> Expr b -> Bind b
NonRec InBndr
final_id Expr InBndr
expr2

        ; (LetFloats, Expr InBndr) -> SimplM (LetFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return ( LetFloats
floats LetFloats -> LetFloats -> LetFloats
`addLetFlts` InBind -> LetFloats
unitLetFloat InBind
bind, InBndr -> Expr InBndr
forall b. InBndr -> Expr b
Var InBndr
final_id ) }}
   where
     expr_ty :: OutType
expr_ty = Expr InBndr -> OutType
exprType Expr InBndr
expr

bindingOk :: TopLevelFlag -> CoreExpr -> Type -> Bool
-- True iff we can have a binding of this expression at this level
-- Precondition: the type is the type of the expression
bindingOk :: TopLevelFlag -> Expr InBndr -> OutType -> Bool
bindingOk top_lvl :: TopLevelFlag
top_lvl expr :: Expr InBndr
expr expr_ty :: OutType
expr_ty
  | TopLevelFlag -> Bool
isTopLevel TopLevelFlag
top_lvl = Expr InBndr -> OutType -> Bool
exprIsTopLevelBindable Expr InBndr
expr OutType
expr_ty
  | Bool
otherwise          = Bool
True

{- Note [Trivial after prepareRhs]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If we call makeTrival on (e |> co), the recursive use of prepareRhs
may leave us with
   { a1 = e }  and   (a1 |> co)
Now the latter is trivial, so we don't want to let-bind it.

Note [Cannot trivialise]
~~~~~~~~~~~~~~~~~~~~~~~~
Consider:
   f :: Int -> Addr#

   foo :: Bar
   foo = Bar (f 3)

Then we can't ANF-ise foo, even though we'd like to, because
we can't make a top-level binding for the Addr# (f 3). And if
so we don't want to turn it into
   foo = let x = f 3 in Bar x
because we'll just end up inlining x back, and that makes the
simplifier loop.  Better not to ANF-ise it at all.

Literal strings are an exception.

   foo = Ptr "blob"#

We want to turn this into:

   foo1 = "blob"#
   foo = Ptr foo1

See Note [CoreSyn top-level string literals] in CoreSyn.

************************************************************************
*                                                                      *
          Completing a lazy binding
*                                                                      *
************************************************************************

completeBind
  * deals only with Ids, not TyVars
  * takes an already-simplified binder and RHS
  * is used for both recursive and non-recursive bindings
  * is used for both top-level and non-top-level bindings

It does the following:
  - tries discarding a dead binding
  - tries PostInlineUnconditionally
  - add unfolding [this is the only place we add an unfolding]
  - add arity

It does *not* attempt to do let-to-case.  Why?  Because it is used for
  - top-level bindings (when let-to-case is impossible)
  - many situations where the "rhs" is known to be a WHNF
                (so let-to-case is inappropriate).

Nor does it do the atomic-argument thing
-}

completeBind :: SimplEnv
             -> TopLevelFlag            -- Flag stuck into unfolding
             -> MaybeJoinCont           -- Required only for join point
             -> InId                    -- Old binder
             -> OutId -> OutExpr        -- New binder and RHS
             -> SimplM (SimplFloats, SimplEnv)
-- completeBind may choose to do its work
--      * by extending the substitution (e.g. let x = y in ...)
--      * or by adding to the floats in the envt
--
-- Binder /can/ be a JoinId
-- Precondition: rhs obeys the let/app invariant
completeBind :: SimplEnv
-> TopLevelFlag
-> MaybeJoinCont
-> InBndr
-> InBndr
-> Expr InBndr
-> SimplM (SimplFloats, SimplEnv)
completeBind env :: SimplEnv
env top_lvl :: TopLevelFlag
top_lvl mb_cont :: MaybeJoinCont
mb_cont old_bndr :: InBndr
old_bndr new_bndr :: InBndr
new_bndr new_rhs :: Expr InBndr
new_rhs
 | InBndr -> Bool
isCoVar InBndr
old_bndr
 = case Expr InBndr
new_rhs of
     Coercion co :: Coercion
co -> (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplEnv -> SimplFloats
emptyFloats SimplEnv
env, SimplEnv -> InBndr -> Coercion -> SimplEnv
extendCvSubst SimplEnv
env InBndr
old_bndr Coercion
co)
     _           -> (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplEnv -> InBind -> (SimplFloats, SimplEnv)
mkFloatBind SimplEnv
env (InBndr -> Expr InBndr -> InBind
forall b. b -> Expr b -> Bind b
NonRec InBndr
new_bndr Expr InBndr
new_rhs))

 | Bool
otherwise
 = ASSERT( isId new_bndr )
   do { let old_info :: IdInfo
old_info = HasDebugCallStack => InBndr -> IdInfo
InBndr -> IdInfo
idInfo InBndr
old_bndr
            old_unf :: Unfolding
old_unf  = IdInfo -> Unfolding
unfoldingInfo IdInfo
old_info
            occ_info :: OccInfo
occ_info = IdInfo -> OccInfo
occInfo IdInfo
old_info

         -- Do eta-expansion on the RHS of the binding
         -- See Note [Eta-expanding at let bindings] in SimplUtils
      ; (new_arity :: Int
new_arity, is_bot :: Bool
is_bot, final_rhs :: Expr InBndr
final_rhs) <- SimplMode
-> InBndr -> Expr InBndr -> SimplM (Int, Bool, Expr InBndr)
tryEtaExpandRhs (SimplEnv -> SimplMode
getMode SimplEnv
env)
                                                          InBndr
new_bndr Expr InBndr
new_rhs

        -- Simplify the unfolding
      ; Unfolding
new_unfolding <- SimplEnv
-> TopLevelFlag
-> MaybeJoinCont
-> InBndr
-> Expr InBndr
-> OutType
-> Unfolding
-> SimplM Unfolding
simplLetUnfolding SimplEnv
env TopLevelFlag
top_lvl MaybeJoinCont
mb_cont InBndr
old_bndr
                                           Expr InBndr
final_rhs (InBndr -> OutType
idType InBndr
new_bndr) Unfolding
old_unf

      ; let final_bndr :: InBndr
final_bndr = InBndr -> Int -> Bool -> Unfolding -> InBndr
addLetBndrInfo InBndr
new_bndr Int
new_arity Bool
is_bot Unfolding
new_unfolding

      ; if SimplEnv
-> TopLevelFlag -> InBndr -> OccInfo -> Expr InBndr -> Bool
postInlineUnconditionally SimplEnv
env TopLevelFlag
top_lvl InBndr
final_bndr OccInfo
occ_info Expr InBndr
final_rhs

        then -- Inline and discard the binding
             do  { Tick -> SimplM ()
tick (InBndr -> Tick
PostInlineUnconditionally InBndr
old_bndr)
                 ; (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv)
forall (m :: * -> *) a. Monad m => a -> m a
return ( SimplEnv -> SimplFloats
emptyFloats SimplEnv
env
                          , SimplEnv -> InBndr -> SimplSR -> SimplEnv
extendIdSubst SimplEnv
env InBndr
old_bndr (SimplSR -> SimplEnv) -> SimplSR -> SimplEnv
forall a b. (a -> b) -> a -> b
$
                            Expr InBndr -> Maybe Int -> SimplSR
DoneEx Expr InBndr
final_rhs (InBndr -> Maybe Int
isJoinId_maybe InBndr
new_bndr)) }
                -- Use the substitution to make quite, quite sure that the
                -- substitution will happen, since we are going to discard the binding

        else -- Keep the binding
             -- pprTrace "Binding" (ppr final_bndr <+> ppr new_unfolding) $
             (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplEnv -> InBind -> (SimplFloats, SimplEnv)
mkFloatBind SimplEnv
env (InBndr -> Expr InBndr -> InBind
forall b. b -> Expr b -> Bind b
NonRec InBndr
final_bndr Expr InBndr
final_rhs)) }

addLetBndrInfo :: OutId -> Arity -> Bool -> Unfolding -> OutId
addLetBndrInfo :: InBndr -> Int -> Bool -> Unfolding -> InBndr
addLetBndrInfo new_bndr :: InBndr
new_bndr new_arity :: Int
new_arity is_bot :: Bool
is_bot new_unf :: Unfolding
new_unf
  = InBndr
new_bndr InBndr -> IdInfo -> InBndr
`setIdInfo` IdInfo
info5
  where
    info1 :: IdInfo
info1 = HasDebugCallStack => InBndr -> IdInfo
InBndr -> IdInfo
idInfo InBndr
new_bndr IdInfo -> Int -> IdInfo
`setArityInfo` Int
new_arity

    -- Unfolding info: Note [Setting the new unfolding]
    info2 :: IdInfo
info2 = IdInfo
info1 IdInfo -> Unfolding -> IdInfo
`setUnfoldingInfo` Unfolding
new_unf

    -- Demand info: Note [Setting the demand info]
    -- We also have to nuke demand info if for some reason
    -- eta-expansion *reduces* the arity of the binding to less
    -- than that of the strictness sig. This can happen: see Note [Arity decrease].
    info3 :: IdInfo
info3 | Unfolding -> Bool
isEvaldUnfolding Unfolding
new_unf
            Bool -> Bool -> Bool
|| (case IdInfo -> StrictSig
strictnessInfo IdInfo
info2 of
                  StrictSig dmd_ty :: DmdType
dmd_ty -> Int
new_arity Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
< DmdType -> Int
dmdTypeDepth DmdType
dmd_ty)
          = IdInfo -> Maybe IdInfo
zapDemandInfo IdInfo
info2 Maybe IdInfo -> IdInfo -> IdInfo
forall a. Maybe a -> a -> a
`orElse` IdInfo
info2
          | Bool
otherwise
          = IdInfo
info2

    -- Bottoming bindings: see Note [Bottoming bindings]
    info4 :: IdInfo
info4 | Bool
is_bot    = IdInfo
info3 IdInfo -> StrictSig -> IdInfo
`setStrictnessInfo`
                        [Demand] -> DmdResult -> StrictSig
mkClosedStrictSig (Int -> Demand -> [Demand]
forall a. Int -> a -> [a]
replicate Int
new_arity Demand
topDmd) DmdResult
exnRes
          | Bool
otherwise = IdInfo
info3

     -- Zap call arity info. We have used it by now (via
     -- `tryEtaExpandRhs`), and the simplifier can invalidate this
     -- information, leading to broken code later (e.g. #13479)
    info5 :: IdInfo
info5 = IdInfo -> IdInfo
zapCallArityInfo IdInfo
info4


{- Note [Arity decrease]
~~~~~~~~~~~~~~~~~~~~~~~~
Generally speaking the arity of a binding should not decrease.  But it *can*
legitimately happen because of RULES.  Eg
        f = g Int
where g has arity 2, will have arity 2.  But if there's a rewrite rule
        g Int --> h
where h has arity 1, then f's arity will decrease.  Here's a real-life example,
which is in the output of Specialise:

     Rec {
        $dm {Arity 2} = \d.\x. op d
        {-# RULES forall d. $dm Int d = $s$dm #-}

        dInt = MkD .... opInt ...
        opInt {Arity 1} = $dm dInt

        $s$dm {Arity 0} = \x. op dInt }

Here opInt has arity 1; but when we apply the rule its arity drops to 0.
That's why Specialise goes to a little trouble to pin the right arity
on specialised functions too.

Note [Bottoming bindings]
~~~~~~~~~~~~~~~~~~~~~~~~~
Suppose we have
   let x = error "urk"
   in ...(case x of <alts>)...
or
   let f = \x. error (x ++ "urk")
   in ...(case f "foo" of <alts>)...

Then we'd like to drop the dead <alts> immediately.  So it's good to
propagate the info that x's RHS is bottom to x's IdInfo as rapidly as
possible.

We use tryEtaExpandRhs on every binding, and it turns ou that the
arity computation it performs (via CoreArity.findRhsArity) already
does a simple bottoming-expression analysis.  So all we need to do
is propagate that info to the binder's IdInfo.

This showed up in Trac #12150; see comment:16.

Note [Setting the demand info]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If the unfolding is a value, the demand info may
go pear-shaped, so we nuke it.  Example:
     let x = (a,b) in
     case x of (p,q) -> h p q x
Here x is certainly demanded. But after we've nuked
the case, we'll get just
     let x = (a,b) in h a b x
and now x is not demanded (I'm assuming h is lazy)
This really happens.  Similarly
     let f = \x -> e in ...f..f...
After inlining f at some of its call sites the original binding may
(for example) be no longer strictly demanded.
The solution here is a bit ad hoc...


************************************************************************
*                                                                      *
\subsection[Simplify-simplExpr]{The main function: simplExpr}
*                                                                      *
************************************************************************

The reason for this OutExprStuff stuff is that we want to float *after*
simplifying a RHS, not before.  If we do so naively we get quadratic
behaviour as things float out.

To see why it's important to do it after, consider this (real) example:

        let t = f x
        in fst t
==>
        let t = let a = e1
                    b = e2
                in (a,b)
        in fst t
==>
        let a = e1
            b = e2
            t = (a,b)
        in
        a       -- Can't inline a this round, cos it appears twice
==>
        e1

Each of the ==> steps is a round of simplification.  We'd save a
whole round if we float first.  This can cascade.  Consider

        let f = g d
        in \x -> ...f...
==>
        let f = let d1 = ..d.. in \y -> e
        in \x -> ...f...
==>
        let d1 = ..d..
        in \x -> ...(\y ->e)...

Only in this second round can the \y be applied, and it
might do the same again.
-}

simplExpr :: SimplEnv -> CoreExpr -> SimplM CoreExpr
simplExpr :: SimplEnv -> Expr InBndr -> SimplM (Expr InBndr)
simplExpr env :: SimplEnv
env (Type ty :: OutType
ty)
  = do { OutType
ty' <- SimplEnv -> OutType -> SimplM OutType
simplType SimplEnv
env OutType
ty  -- See Note [Avoiding space leaks in OutType]
       ; Expr InBndr -> SimplM (Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (OutType -> Expr InBndr
forall b. OutType -> Expr b
Type OutType
ty') }

simplExpr env :: SimplEnv
env expr :: Expr InBndr
expr
  = SimplEnv -> Expr InBndr -> SimplCont -> SimplM (Expr InBndr)
simplExprC SimplEnv
env Expr InBndr
expr (OutType -> SimplCont
mkBoringStop OutType
expr_out_ty)
  where
    expr_out_ty :: OutType
    expr_out_ty :: OutType
expr_out_ty = SimplEnv -> OutType -> OutType
substTy SimplEnv
env (Expr InBndr -> OutType
exprType Expr InBndr
expr)
    -- NB: Since 'expr' is term-valued, not (Type ty), this call
    --     to exprType will succeed.  exprType fails on (Type ty).

simplExprC :: SimplEnv
           -> InExpr     -- A term-valued expression, never (Type ty)
           -> SimplCont
           -> SimplM OutExpr
        -- Simplify an expression, given a continuation
simplExprC :: SimplEnv -> Expr InBndr -> SimplCont -> SimplM (Expr InBndr)
simplExprC env :: SimplEnv
env expr :: Expr InBndr
expr cont :: SimplCont
cont
  = -- pprTrace "simplExprC" (ppr expr $$ ppr cont {- $$ ppr (seIdSubst env) -} $$ ppr (seLetFloats env) ) $
    do  { (floats :: SimplFloats
floats, expr' :: Expr InBndr
expr') <- SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF SimplEnv
env Expr InBndr
expr SimplCont
cont
        ; -- pprTrace "simplExprC ret" (ppr expr $$ ppr expr') $
          -- pprTrace "simplExprC ret3" (ppr (seInScope env')) $
          -- pprTrace "simplExprC ret4" (ppr (seLetFloats env')) $
          Expr InBndr -> SimplM (Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats -> Expr InBndr -> Expr InBndr
wrapFloats SimplFloats
floats Expr InBndr
expr') }

--------------------------------------------------
simplExprF :: SimplEnv
           -> InExpr     -- A term-valued expression, never (Type ty)
           -> SimplCont
           -> SimplM (SimplFloats, OutExpr)

simplExprF :: SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF env :: SimplEnv
env e :: Expr InBndr
e cont :: SimplCont
cont
  = {- pprTrace "simplExprF" (vcat
      [ ppr e
      , text "cont =" <+> ppr cont
      , text "inscope =" <+> ppr (seInScope env)
      , text "tvsubst =" <+> ppr (seTvSubst env)
      , text "idsubst =" <+> ppr (seIdSubst env)
      , text "cvsubst =" <+> ppr (seCvSubst env)
      ]) $ -}
    SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF1 SimplEnv
env Expr InBndr
e SimplCont
cont

simplExprF1 :: SimplEnv -> InExpr -> SimplCont
            -> SimplM (SimplFloats, OutExpr)

simplExprF1 :: SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF1 _ (Type ty :: OutType
ty) _
  = [Char] -> SDoc -> SimplM (SimplFloats, Expr InBndr)
forall a. HasCallStack => [Char] -> SDoc -> a
pprPanic "simplExprF: type" (OutType -> SDoc
forall a. Outputable a => a -> SDoc
ppr OutType
ty)
    -- simplExprF does only with term-valued expressions
    -- The (Type ty) case is handled separately by simplExpr
    -- and by the other callers of simplExprF

simplExprF1 env :: SimplEnv
env (Var v :: InBndr
v)        cont :: SimplCont
cont = {-#SCC "simplIdF" #-} SimplEnv
-> InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplIdF SimplEnv
env InBndr
v SimplCont
cont
simplExprF1 env :: SimplEnv
env (Lit lit :: Literal
lit)      cont :: SimplCont
cont = {-#SCC "rebuild" #-} SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
rebuild SimplEnv
env (Literal -> Expr InBndr
forall b. Literal -> Expr b
Lit Literal
lit) SimplCont
cont
simplExprF1 env :: SimplEnv
env (Tick t :: Tickish InBndr
t expr :: Expr InBndr
expr)  cont :: SimplCont
cont = {-#SCC "simplTick" #-} SimplEnv
-> Tickish InBndr
-> Expr InBndr
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
simplTick SimplEnv
env Tickish InBndr
t Expr InBndr
expr SimplCont
cont
simplExprF1 env :: SimplEnv
env (Cast body :: Expr InBndr
body co :: Coercion
co) cont :: SimplCont
cont = {-#SCC "simplCast" #-} SimplEnv
-> Expr InBndr
-> Coercion
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
simplCast SimplEnv
env Expr InBndr
body Coercion
co SimplCont
cont
simplExprF1 env :: SimplEnv
env (Coercion co :: Coercion
co)  cont :: SimplCont
cont = {-#SCC "simplCoercionF" #-} SimplEnv
-> Coercion -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplCoercionF SimplEnv
env Coercion
co SimplCont
cont

simplExprF1 env :: SimplEnv
env (App fun :: Expr InBndr
fun arg :: Expr InBndr
arg) cont :: SimplCont
cont
  = {-#SCC "simplExprF1-App" #-} case Expr InBndr
arg of
      Type ty :: OutType
ty -> do { -- The argument type will (almost) certainly be used
                      -- in the output program, so just force it now.
                      -- See Note [Avoiding space leaks in OutType]
                      OutType
arg' <- SimplEnv -> OutType -> SimplM OutType
simplType SimplEnv
env OutType
ty

                      -- But use substTy, not simplType, to avoid forcing
                      -- the hole type; it will likely not be needed.
                      -- See Note [The hole type in ApplyToTy]
                    ; let hole' :: OutType
hole' = SimplEnv -> OutType -> OutType
substTy SimplEnv
env (Expr InBndr -> OutType
exprType Expr InBndr
fun)

                    ; SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF SimplEnv
env Expr InBndr
fun (SimplCont -> SimplM (SimplFloats, Expr InBndr))
-> SimplCont -> SimplM (SimplFloats, Expr InBndr)
forall a b. (a -> b) -> a -> b
$
                      ApplyToTy :: OutType -> OutType -> SimplCont -> SimplCont
ApplyToTy { sc_arg_ty :: OutType
sc_arg_ty  = OutType
arg'
                                , sc_hole_ty :: OutType
sc_hole_ty = OutType
hole'
                                , sc_cont :: SimplCont
sc_cont    = SimplCont
cont } }
      _       -> SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF SimplEnv
env Expr InBndr
fun (SimplCont -> SimplM (SimplFloats, Expr InBndr))
-> SimplCont -> SimplM (SimplFloats, Expr InBndr)
forall a b. (a -> b) -> a -> b
$
                 ApplyToVal :: DupFlag -> Expr InBndr -> SimplEnv -> SimplCont -> SimplCont
ApplyToVal { sc_arg :: Expr InBndr
sc_arg = Expr InBndr
arg, sc_env :: SimplEnv
sc_env = SimplEnv
env
                            , sc_dup :: DupFlag
sc_dup = DupFlag
NoDup, sc_cont :: SimplCont
sc_cont = SimplCont
cont }

simplExprF1 env :: SimplEnv
env expr :: Expr InBndr
expr@(Lam {}) cont :: SimplCont
cont
  = {-#SCC "simplExprF1-Lam" #-}
    SimplEnv
-> [InBndr]
-> Expr InBndr
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
simplLam SimplEnv
env [InBndr]
zapped_bndrs Expr InBndr
body SimplCont
cont
        -- The main issue here is under-saturated lambdas
        --   (\x1. \x2. e) arg1
        -- Here x1 might have "occurs-once" occ-info, because occ-info
        -- is computed assuming that a group of lambdas is applied
        -- all at once.  If there are too few args, we must zap the
        -- occ-info, UNLESS the remaining binders are one-shot
  where
    (bndrs :: [InBndr]
bndrs, body :: Expr InBndr
body) = Expr InBndr -> ([InBndr], Expr InBndr)
forall b. Expr b -> ([b], Expr b)
collectBinders Expr InBndr
expr
    zapped_bndrs :: [InBndr]
zapped_bndrs | Bool
need_to_zap = (InBndr -> InBndr) -> [InBndr] -> [InBndr]
forall a b. (a -> b) -> [a] -> [b]
map InBndr -> InBndr
zap [InBndr]
bndrs
                 | Bool
otherwise   = [InBndr]
bndrs

    need_to_zap :: Bool
need_to_zap = (InBndr -> Bool) -> [InBndr] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any InBndr -> Bool
zappable_bndr (Int -> [InBndr] -> [InBndr]
forall a. Int -> [a] -> [a]
drop Int
n_args [InBndr]
bndrs)
    n_args :: Int
n_args = SimplCont -> Int
countArgs SimplCont
cont
        -- NB: countArgs counts all the args (incl type args)
        -- and likewise drop counts all binders (incl type lambdas)

    zappable_bndr :: InBndr -> Bool
zappable_bndr b :: InBndr
b = InBndr -> Bool
isId InBndr
b Bool -> Bool -> Bool
&& Bool -> Bool
not (InBndr -> Bool
isOneShotBndr InBndr
b)
    zap :: InBndr -> InBndr
zap b :: InBndr
b | InBndr -> Bool
isTyVar InBndr
b = InBndr
b
          | Bool
otherwise = InBndr -> InBndr
zapLamIdInfo InBndr
b

simplExprF1 env :: SimplEnv
env (Case scrut :: Expr InBndr
scrut bndr :: InBndr
bndr _ alts :: [Alt InBndr]
alts) cont :: SimplCont
cont
  = {-#SCC "simplExprF1-Case" #-}
    SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF SimplEnv
env Expr InBndr
scrut (Select :: DupFlag
-> InBndr -> [Alt InBndr] -> SimplEnv -> SimplCont -> SimplCont
Select { sc_dup :: DupFlag
sc_dup = DupFlag
NoDup, sc_bndr :: InBndr
sc_bndr = InBndr
bndr
                                 , sc_alts :: [Alt InBndr]
sc_alts = [Alt InBndr]
alts
                                 , sc_env :: SimplEnv
sc_env = SimplEnv
env, sc_cont :: SimplCont
sc_cont = SimplCont
cont })

simplExprF1 env :: SimplEnv
env (Let (Rec pairs :: [(InBndr, Expr InBndr)]
pairs) body :: Expr InBndr
body) cont :: SimplCont
cont
  | Just pairs' :: [(InBndr, Expr InBndr)]
pairs' <- [(InBndr, Expr InBndr)] -> Maybe [(InBndr, Expr InBndr)]
joinPointBindings_maybe [(InBndr, Expr InBndr)]
pairs
  = {-#SCC "simplRecJoinPoin" #-} SimplEnv
-> [(InBndr, Expr InBndr)]
-> Expr InBndr
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
simplRecJoinPoint SimplEnv
env [(InBndr, Expr InBndr)]
pairs' Expr InBndr
body SimplCont
cont

  | Bool
otherwise
  = {-#SCC "simplRecE" #-} SimplEnv
-> [(InBndr, Expr InBndr)]
-> Expr InBndr
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
simplRecE SimplEnv
env [(InBndr, Expr InBndr)]
pairs Expr InBndr
body SimplCont
cont

simplExprF1 env :: SimplEnv
env (Let (NonRec bndr :: InBndr
bndr rhs :: Expr InBndr
rhs) body :: Expr InBndr
body) cont :: SimplCont
cont
  | Type ty :: OutType
ty <- Expr InBndr
rhs    -- First deal with type lets (let a = Type ty in e)
  = {-#SCC "simplExprF1-NonRecLet-Type" #-}
    ASSERT( isTyVar bndr )
    do { OutType
ty' <- SimplEnv -> OutType -> SimplM OutType
simplType SimplEnv
env OutType
ty
       ; SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF (SimplEnv -> InBndr -> OutType -> SimplEnv
extendTvSubst SimplEnv
env InBndr
bndr OutType
ty') Expr InBndr
body SimplCont
cont }

  | Just (bndr' :: InBndr
bndr', rhs' :: Expr InBndr
rhs') <- InBndr -> Expr InBndr -> Maybe (InBndr, Expr InBndr)
joinPointBinding_maybe InBndr
bndr Expr InBndr
rhs
  = {-#SCC "simplNonRecJoinPoint" #-} SimplEnv
-> InBndr
-> Expr InBndr
-> Expr InBndr
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
simplNonRecJoinPoint SimplEnv
env InBndr
bndr' Expr InBndr
rhs' Expr InBndr
body SimplCont
cont

  | Bool
otherwise
  = {-#SCC "simplNonRecE" #-} SimplEnv
-> InBndr
-> (Expr InBndr, SimplEnv)
-> ([InBndr], Expr InBndr)
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
simplNonRecE SimplEnv
env InBndr
bndr (Expr InBndr
rhs, SimplEnv
env) ([], Expr InBndr
body) SimplCont
cont

{- Note [Avoiding space leaks in OutType]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Since the simplifier is run for multiple iterations, we need to ensure
that any thunks in the output of one simplifier iteration are forced
by the evaluation of the next simplifier iteration. Otherwise we may
retain multiple copies of the Core program and leak a terrible amount
of memory (as in #13426).

The simplifier is naturally strict in the entire "Expr part" of the
input Core program, because any expression may contain binders, which
we must find in order to extend the SimplEnv accordingly. But types
do not contain binders and so it is tempting to write things like

    simplExpr env (Type ty) = return (Type (substTy env ty))   -- Bad!

This is Bad because the result includes a thunk (substTy env ty) which
retains a reference to the whole simplifier environment; and the next
simplifier iteration will not force this thunk either, because the
line above is not strict in ty.

So instead our strategy is for the simplifier to fully evaluate
OutTypes when it emits them into the output Core program, for example

    simplExpr env (Type ty) = do { ty' <- simplType env ty     -- Good
                                 ; return (Type ty') }

where the only difference from above is that simplType calls seqType
on the result of substTy.

However, SimplCont can also contain OutTypes and it's not necessarily
a good idea to force types on the way in to SimplCont, because they
may end up not being used and forcing them could be a lot of wasted
work. T5631 is a good example of this.

- For ApplyToTy's sc_arg_ty, we force the type on the way in because
  the type will almost certainly appear as a type argument in the
  output program.

- For the hole types in Stop and ApplyToTy, we force the type when we
  emit it into the output program, after obtaining it from
  contResultType. (The hole type in ApplyToTy is only directly used
  to form the result type in a new Stop continuation.)
-}

---------------------------------
-- Simplify a join point, adding the context.
-- Context goes *inside* the lambdas. IOW, if the join point has arity n, we do:
--   \x1 .. xn -> e => \x1 .. xn -> E[e]
-- Note that we need the arity of the join point, since e may be a lambda
-- (though this is unlikely). See Note [Case-of-case and join points].
simplJoinRhs :: SimplEnv -> InId -> InExpr -> SimplCont
             -> SimplM OutExpr
simplJoinRhs :: SimplEnv
-> InBndr -> Expr InBndr -> SimplCont -> SimplM (Expr InBndr)
simplJoinRhs env :: SimplEnv
env bndr :: InBndr
bndr expr :: Expr InBndr
expr cont :: SimplCont
cont
  | Just arity :: Int
arity <- InBndr -> Maybe Int
isJoinId_maybe InBndr
bndr
  =  do { let (join_bndrs :: [InBndr]
join_bndrs, join_body :: Expr InBndr
join_body) = Int -> Expr InBndr -> ([InBndr], Expr InBndr)
forall b. Int -> Expr b -> ([b], Expr b)
collectNBinders Int
arity Expr InBndr
expr
        ; (env' :: SimplEnv
env', join_bndrs' :: [InBndr]
join_bndrs') <- SimplEnv -> [InBndr] -> SimplM (SimplEnv, [InBndr])
simplLamBndrs SimplEnv
env [InBndr]
join_bndrs
        ; Expr InBndr
join_body' <- SimplEnv -> Expr InBndr -> SimplCont -> SimplM (Expr InBndr)
simplExprC SimplEnv
env' Expr InBndr
join_body SimplCont
cont
        ; Expr InBndr -> SimplM (Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (Expr InBndr -> SimplM (Expr InBndr))
-> Expr InBndr -> SimplM (Expr InBndr)
forall a b. (a -> b) -> a -> b
$ [InBndr] -> Expr InBndr -> Expr InBndr
forall b. [b] -> Expr b -> Expr b
mkLams [InBndr]
join_bndrs' Expr InBndr
join_body' }

  | Bool
otherwise
  = [Char] -> SDoc -> SimplM (Expr InBndr)
forall a. HasCallStack => [Char] -> SDoc -> a
pprPanic "simplJoinRhs" (InBndr -> SDoc
forall a. Outputable a => a -> SDoc
ppr InBndr
bndr)

---------------------------------
simplType :: SimplEnv -> InType -> SimplM OutType
        -- Kept monadic just so we can do the seqType
        -- See Note [Avoiding space leaks in OutType]
simplType :: SimplEnv -> OutType -> SimplM OutType
simplType env :: SimplEnv
env ty :: OutType
ty
  = -- pprTrace "simplType" (ppr ty $$ ppr (seTvSubst env)) $
    OutType -> ()
seqType OutType
new_ty () -> SimplM OutType -> SimplM OutType
forall a b. a -> b -> b
`seq` OutType -> SimplM OutType
forall (m :: * -> *) a. Monad m => a -> m a
return OutType
new_ty
  where
    new_ty :: OutType
new_ty = SimplEnv -> OutType -> OutType
substTy SimplEnv
env OutType
ty

---------------------------------
simplCoercionF :: SimplEnv -> InCoercion -> SimplCont
               -> SimplM (SimplFloats, OutExpr)
simplCoercionF :: SimplEnv
-> Coercion -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplCoercionF env :: SimplEnv
env co :: Coercion
co cont :: SimplCont
cont
  = do { Coercion
co' <- SimplEnv -> Coercion -> SimplM Coercion
simplCoercion SimplEnv
env Coercion
co
       ; SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
rebuild SimplEnv
env (Coercion -> Expr InBndr
forall b. Coercion -> Expr b
Coercion Coercion
co') SimplCont
cont }

simplCoercion :: SimplEnv -> InCoercion -> SimplM OutCoercion
simplCoercion :: SimplEnv -> Coercion -> SimplM Coercion
simplCoercion env :: SimplEnv
env co :: Coercion
co
  = do { DynFlags
dflags <- SimplM DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
       ; let opt_co :: Coercion
opt_co = DynFlags -> TCvSubst -> Coercion -> Coercion
optCoercion DynFlags
dflags (SimplEnv -> TCvSubst
getTCvSubst SimplEnv
env) Coercion
co
       ; Coercion -> ()
seqCo Coercion
opt_co () -> SimplM Coercion -> SimplM Coercion
forall a b. a -> b -> b
`seq` Coercion -> SimplM Coercion
forall (m :: * -> *) a. Monad m => a -> m a
return Coercion
opt_co }

-----------------------------------
-- | Push a TickIt context outwards past applications and cases, as
-- long as this is a non-scoping tick, to let case and application
-- optimisations apply.

simplTick :: SimplEnv -> Tickish Id -> InExpr -> SimplCont
          -> SimplM (SimplFloats, OutExpr)
simplTick :: SimplEnv
-> Tickish InBndr
-> Expr InBndr
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
simplTick env :: SimplEnv
env tickish :: Tickish InBndr
tickish expr :: Expr InBndr
expr cont :: SimplCont
cont
  -- A scoped tick turns into a continuation, so that we can spot
  -- (scc t (\x . e)) in simplLam and eliminate the scc.  If we didn't do
  -- it this way, then it would take two passes of the simplifier to
  -- reduce ((scc t (\x . e)) e').
  -- NB, don't do this with counting ticks, because if the expr is
  -- bottom, then rebuildCall will discard the continuation.

-- XXX: we cannot do this, because the simplifier assumes that
-- the context can be pushed into a case with a single branch. e.g.
--    scc<f>  case expensive of p -> e
-- becomes
--    case expensive of p -> scc<f> e
--
-- So I'm disabling this for now.  It just means we will do more
-- simplifier iterations that necessary in some cases.

--  | tickishScoped tickish && not (tickishCounts tickish)
--  = simplExprF env expr (TickIt tickish cont)

  -- For unscoped or soft-scoped ticks, we are allowed to float in new
  -- cost, so we simply push the continuation inside the tick.  This
  -- has the effect of moving the tick to the outside of a case or
  -- application context, allowing the normal case and application
  -- optimisations to fire.
  | Tickish InBndr
tickish Tickish InBndr -> TickishScoping -> Bool
forall id. Tickish id -> TickishScoping -> Bool
`tickishScopesLike` TickishScoping
SoftScope
  = do { (floats :: SimplFloats
floats, expr' :: Expr InBndr
expr') <- SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF SimplEnv
env Expr InBndr
expr SimplCont
cont
       ; (SimplFloats, Expr InBndr) -> SimplM (SimplFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats
floats, Tickish InBndr -> Expr InBndr -> Expr InBndr
mkTick Tickish InBndr
tickish Expr InBndr
expr')
       }

  -- Push tick inside if the context looks like this will allow us to
  -- do a case-of-case - see Note [case-of-scc-of-case]
  | Select {} <- SimplCont
cont, Just expr' :: Expr InBndr
expr' <- Maybe (Expr InBndr)
push_tick_inside
  = SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF SimplEnv
env Expr InBndr
expr' SimplCont
cont

  -- We don't want to move the tick, but we might still want to allow
  -- floats to pass through with appropriate wrapping (or not, see
  -- wrap_floats below)
  --- | not (tickishCounts tickish) || tickishCanSplit tickish
  -- = wrap_floats

  | Bool
otherwise
  = SimplM (SimplFloats, Expr InBndr)
no_floating_past_tick

 where

  -- Try to push tick inside a case, see Note [case-of-scc-of-case].
  push_tick_inside :: Maybe (Expr InBndr)
push_tick_inside =
    case Expr InBndr
expr0 of
      Case scrut :: Expr InBndr
scrut bndr :: InBndr
bndr ty :: OutType
ty alts :: [Alt InBndr]
alts
             -> Expr InBndr -> Maybe (Expr InBndr)
forall a. a -> Maybe a
Just (Expr InBndr -> Maybe (Expr InBndr))
-> Expr InBndr -> Maybe (Expr InBndr)
forall a b. (a -> b) -> a -> b
$ Expr InBndr -> InBndr -> OutType -> [Alt InBndr] -> Expr InBndr
forall b. Expr b -> b -> OutType -> [Alt b] -> Expr b
Case (Expr InBndr -> Expr InBndr
tickScrut Expr InBndr
scrut) InBndr
bndr OutType
ty ((Alt InBndr -> Alt InBndr) -> [Alt InBndr] -> [Alt InBndr]
forall a b. (a -> b) -> [a] -> [b]
map Alt InBndr -> Alt InBndr
forall a b. (a, b, Expr InBndr) -> (a, b, Expr InBndr)
tickAlt [Alt InBndr]
alts)
      _other :: Expr InBndr
_other -> Maybe (Expr InBndr)
forall a. Maybe a
Nothing
   where (ticks :: [Tickish InBndr]
ticks, expr0 :: Expr InBndr
expr0) = (Tickish InBndr -> Bool)
-> Expr InBndr -> ([Tickish InBndr], Expr InBndr)
forall b.
(Tickish InBndr -> Bool) -> Expr b -> ([Tickish InBndr], Expr b)
stripTicksTop Tickish InBndr -> Bool
forall id. Tickish id -> Bool
movable (Tickish InBndr -> Expr InBndr -> Expr InBndr
forall b. Tickish InBndr -> Expr b -> Expr b
Tick Tickish InBndr
tickish Expr InBndr
expr)
         movable :: Tickish id -> Bool
movable t :: Tickish id
t      = Bool -> Bool
not (Tickish id -> Bool
forall id. Tickish id -> Bool
tickishCounts Tickish id
t) Bool -> Bool -> Bool
||
                          Tickish id
t Tickish id -> TickishScoping -> Bool
forall id. Tickish id -> TickishScoping -> Bool
`tickishScopesLike` TickishScoping
NoScope Bool -> Bool -> Bool
||
                          Tickish id -> Bool
forall id. Tickish id -> Bool
tickishCanSplit Tickish id
t
         tickScrut :: Expr InBndr -> Expr InBndr
tickScrut e :: Expr InBndr
e    = (Tickish InBndr -> Expr InBndr -> Expr InBndr)
-> Expr InBndr -> [Tickish InBndr] -> Expr InBndr
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr Tickish InBndr -> Expr InBndr -> Expr InBndr
mkTick Expr InBndr
e [Tickish InBndr]
ticks
         -- Alternatives get annotated with all ticks that scope in some way,
         -- but we don't want to count entries.
         tickAlt :: (a, b, Expr InBndr) -> (a, b, Expr InBndr)
tickAlt (c :: a
c,bs :: b
bs,e :: Expr InBndr
e) = (a
c,b
bs, (Tickish InBndr -> Expr InBndr -> Expr InBndr)
-> Expr InBndr -> [Tickish InBndr] -> Expr InBndr
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr Tickish InBndr -> Expr InBndr -> Expr InBndr
mkTick Expr InBndr
e [Tickish InBndr]
ts_scope)
         ts_scope :: [Tickish InBndr]
ts_scope         = (Tickish InBndr -> Tickish InBndr)
-> [Tickish InBndr] -> [Tickish InBndr]
forall a b. (a -> b) -> [a] -> [b]
map Tickish InBndr -> Tickish InBndr
forall id. Tickish id -> Tickish id
mkNoCount ([Tickish InBndr] -> [Tickish InBndr])
-> [Tickish InBndr] -> [Tickish InBndr]
forall a b. (a -> b) -> a -> b
$
                            (Tickish InBndr -> Bool) -> [Tickish InBndr] -> [Tickish InBndr]
forall a. (a -> Bool) -> [a] -> [a]
filter (Bool -> Bool
not (Bool -> Bool)
-> (Tickish InBndr -> Bool) -> Tickish InBndr -> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. (Tickish InBndr -> TickishScoping -> Bool
forall id. Tickish id -> TickishScoping -> Bool
`tickishScopesLike` TickishScoping
NoScope)) [Tickish InBndr]
ticks

  no_floating_past_tick :: SimplM (SimplFloats, Expr InBndr)
no_floating_past_tick =
    do { let (inc :: SimplCont
inc,outc :: SimplCont
outc) = SimplCont -> (SimplCont, SimplCont)
splitCont SimplCont
cont
       ; (floats :: SimplFloats
floats, expr1 :: Expr InBndr
expr1) <- SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF SimplEnv
env Expr InBndr
expr SimplCont
inc
       ; let expr2 :: Expr InBndr
expr2    = SimplFloats -> Expr InBndr -> Expr InBndr
wrapFloats SimplFloats
floats Expr InBndr
expr1
             tickish' :: Tickish InBndr
tickish' = SimplEnv -> Tickish InBndr -> Tickish InBndr
simplTickish SimplEnv
env Tickish InBndr
tickish
       ; SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
rebuild SimplEnv
env (Tickish InBndr -> Expr InBndr -> Expr InBndr
mkTick Tickish InBndr
tickish' Expr InBndr
expr2) SimplCont
outc
       }

-- Alternative version that wraps outgoing floats with the tick.  This
-- results in ticks being duplicated, as we don't make any attempt to
-- eliminate the tick if we re-inline the binding (because the tick
-- semantics allows unrestricted inlining of HNFs), so I'm not doing
-- this any more.  FloatOut will catch any real opportunities for
-- floating.
--
--  wrap_floats =
--    do { let (inc,outc) = splitCont cont
--       ; (env', expr') <- simplExprF (zapFloats env) expr inc
--       ; let tickish' = simplTickish env tickish
--       ; let wrap_float (b,rhs) = (zapIdStrictness (setIdArity b 0),
--                                   mkTick (mkNoCount tickish') rhs)
--              -- when wrapping a float with mkTick, we better zap the Id's
--              -- strictness info and arity, because it might be wrong now.
--       ; let env'' = addFloats env (mapFloats env' wrap_float)
--       ; rebuild env'' expr' (TickIt tickish' outc)
--       }


  simplTickish :: SimplEnv -> Tickish InBndr -> Tickish InBndr
simplTickish env :: SimplEnv
env tickish :: Tickish InBndr
tickish
    | Breakpoint n :: Int
n ids :: [InBndr]
ids <- Tickish InBndr
tickish
          = Int -> [InBndr] -> Tickish InBndr
forall id. Int -> [id] -> Tickish id
Breakpoint Int
n ((InBndr -> InBndr) -> [InBndr] -> [InBndr]
forall a b. (a -> b) -> [a] -> [b]
map (SimplSR -> InBndr
getDoneId (SimplSR -> InBndr) -> (InBndr -> SimplSR) -> InBndr -> InBndr
forall b c a. (b -> c) -> (a -> b) -> a -> c
. SimplEnv -> InBndr -> SimplSR
substId SimplEnv
env) [InBndr]
ids)
    | Bool
otherwise = Tickish InBndr
tickish

  -- Push type application and coercion inside a tick
  splitCont :: SimplCont -> (SimplCont, SimplCont)
  splitCont :: SimplCont -> (SimplCont, SimplCont)
splitCont cont :: SimplCont
cont@(ApplyToTy { sc_cont :: SimplCont -> SimplCont
sc_cont = SimplCont
tail }) = (SimplCont
cont { sc_cont :: SimplCont
sc_cont = SimplCont
inc }, SimplCont
outc)
    where (inc :: SimplCont
inc,outc :: SimplCont
outc) = SimplCont -> (SimplCont, SimplCont)
splitCont SimplCont
tail
  splitCont (CastIt co :: Coercion
co c :: SimplCont
c) = (Coercion -> SimplCont -> SimplCont
CastIt Coercion
co SimplCont
inc, SimplCont
outc)
    where (inc :: SimplCont
inc,outc :: SimplCont
outc) = SimplCont -> (SimplCont, SimplCont)
splitCont SimplCont
c
  splitCont other :: SimplCont
other = (OutType -> SimplCont
mkBoringStop (SimplCont -> OutType
contHoleType SimplCont
other), SimplCont
other)

  getDoneId :: SimplSR -> InBndr
getDoneId (DoneId id :: InBndr
id)  = InBndr
id
  getDoneId (DoneEx e :: Expr InBndr
e _) = HasDebugCallStack => Expr InBndr -> InBndr
Expr InBndr -> InBndr
getIdFromTrivialExpr Expr InBndr
e -- Note [substTickish] in CoreSubst
  getDoneId other :: SimplSR
other = [Char] -> SDoc -> InBndr
forall a. HasCallStack => [Char] -> SDoc -> a
pprPanic "getDoneId" (SimplSR -> SDoc
forall a. Outputable a => a -> SDoc
ppr SimplSR
other)

-- Note [case-of-scc-of-case]
-- It's pretty important to be able to transform case-of-case when
-- there's an SCC in the way.  For example, the following comes up
-- in nofib/real/compress/Encode.hs:
--
--        case scctick<code_string.r1>
--             case $wcode_string_r13s wild_XC w1_s137 w2_s138 l_aje
--             of _ { (# ww1_s13f, ww2_s13g, ww3_s13h #) ->
--             (ww1_s13f, ww2_s13g, ww3_s13h)
--             }
--        of _ { (ww_s12Y, ww1_s12Z, ww2_s130) ->
--        tick<code_string.f1>
--        (ww_s12Y,
--         ww1_s12Z,
--         PTTrees.PT
--           @ GHC.Types.Char @ GHC.Types.Int wild2_Xj ww2_s130 r_ajf)
--        }
--
-- We really want this case-of-case to fire, because then the 3-tuple
-- will go away (indeed, the CPR optimisation is relying on this
-- happening).  But the scctick is in the way - we need to push it
-- inside to expose the case-of-case.  So we perform this
-- transformation on the inner case:
--
--   scctick c (case e of { p1 -> e1; ...; pn -> en })
--    ==>
--   case (scctick c e) of { p1 -> scc c e1; ...; pn -> scc c en }
--
-- So we've moved a constant amount of work out of the scc to expose
-- the case.  We only do this when the continuation is interesting: in
-- for now, it has to be another Case (maybe generalise this later).

{-
************************************************************************
*                                                                      *
\subsection{The main rebuilder}
*                                                                      *
************************************************************************
-}

rebuild :: SimplEnv -> OutExpr -> SimplCont -> SimplM (SimplFloats, OutExpr)
-- At this point the substitution in the SimplEnv should be irrelevant;
-- only the in-scope set matters
rebuild :: SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
rebuild env :: SimplEnv
env expr :: Expr InBndr
expr cont :: SimplCont
cont
  = case SimplCont
cont of
      Stop {}          -> (SimplFloats, Expr InBndr) -> SimplM (SimplFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplEnv -> SimplFloats
emptyFloats SimplEnv
env, Expr InBndr
expr)
      TickIt t :: Tickish InBndr
t cont :: SimplCont
cont    -> SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
rebuild SimplEnv
env (Tickish InBndr -> Expr InBndr -> Expr InBndr
mkTick Tickish InBndr
t Expr InBndr
expr) SimplCont
cont
      CastIt co :: Coercion
co cont :: SimplCont
cont   -> SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
rebuild SimplEnv
env (Expr InBndr -> Coercion -> Expr InBndr
mkCast Expr InBndr
expr Coercion
co) SimplCont
cont
                       -- NB: mkCast implements the (Coercion co |> g) optimisation

      Select { sc_bndr :: SimplCont -> InBndr
sc_bndr = InBndr
bndr, sc_alts :: SimplCont -> [Alt InBndr]
sc_alts = [Alt InBndr]
alts, sc_env :: SimplCont -> SimplEnv
sc_env = SimplEnv
se, sc_cont :: SimplCont -> SimplCont
sc_cont = SimplCont
cont }
        -> SimplEnv
-> Expr InBndr
-> InBndr
-> [Alt InBndr]
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
rebuildCase (SimplEnv
se SimplEnv -> SimplEnv -> SimplEnv
`setInScopeFromE` SimplEnv
env) Expr InBndr
expr InBndr
bndr [Alt InBndr]
alts SimplCont
cont

      StrictArg { sc_fun :: SimplCont -> ArgInfo
sc_fun = ArgInfo
fun, sc_cont :: SimplCont -> SimplCont
sc_cont = SimplCont
cont }
        -> SimplEnv
-> ArgInfo -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
rebuildCall SimplEnv
env (ArgInfo
fun ArgInfo -> Expr InBndr -> ArgInfo
`addValArgTo` Expr InBndr
expr) SimplCont
cont
      StrictBind { sc_bndr :: SimplCont -> InBndr
sc_bndr = InBndr
b, sc_bndrs :: SimplCont -> [InBndr]
sc_bndrs = [InBndr]
bs, sc_body :: SimplCont -> Expr InBndr
sc_body = Expr InBndr
body
                 , sc_env :: SimplCont -> SimplEnv
sc_env = SimplEnv
se, sc_cont :: SimplCont -> SimplCont
sc_cont = SimplCont
cont }
        -> do { (floats1 :: SimplFloats
floats1, env' :: SimplEnv
env') <- SimplEnv -> InBndr -> Expr InBndr -> SimplM (SimplFloats, SimplEnv)
simplNonRecX (SimplEnv
se SimplEnv -> SimplEnv -> SimplEnv
`setInScopeFromE` SimplEnv
env) InBndr
b Expr InBndr
expr
                                  -- expr satisfies let/app since it started life
                                  -- in a call to simplNonRecE
              ; (floats2 :: SimplFloats
floats2, expr' :: Expr InBndr
expr') <- SimplEnv
-> [InBndr]
-> Expr InBndr
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
simplLam SimplEnv
env' [InBndr]
bs Expr InBndr
body SimplCont
cont
              ; (SimplFloats, Expr InBndr) -> SimplM (SimplFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats
floats1 SimplFloats -> SimplFloats -> SimplFloats
`addFloats` SimplFloats
floats2, Expr InBndr
expr') }

      ApplyToTy  { sc_arg_ty :: SimplCont -> OutType
sc_arg_ty = OutType
ty, sc_cont :: SimplCont -> SimplCont
sc_cont = SimplCont
cont}
        -> SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
rebuild SimplEnv
env (Expr InBndr -> Expr InBndr -> Expr InBndr
forall b. Expr b -> Expr b -> Expr b
App Expr InBndr
expr (OutType -> Expr InBndr
forall b. OutType -> Expr b
Type OutType
ty)) SimplCont
cont

      ApplyToVal { sc_arg :: SimplCont -> Expr InBndr
sc_arg = Expr InBndr
arg, sc_env :: SimplCont -> SimplEnv
sc_env = SimplEnv
se, sc_dup :: SimplCont -> DupFlag
sc_dup = DupFlag
dup_flag, sc_cont :: SimplCont -> SimplCont
sc_cont = SimplCont
cont}
        -- See Note [Avoid redundant simplification]
        -> do { (_, _, arg' :: Expr InBndr
arg') <- SimplEnv
-> DupFlag
-> SimplEnv
-> Expr InBndr
-> SimplM (DupFlag, SimplEnv, Expr InBndr)
simplArg SimplEnv
env DupFlag
dup_flag SimplEnv
se Expr InBndr
arg
              ; SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
rebuild SimplEnv
env (Expr InBndr -> Expr InBndr -> Expr InBndr
forall b. Expr b -> Expr b -> Expr b
App Expr InBndr
expr Expr InBndr
arg') SimplCont
cont }

{-
************************************************************************
*                                                                      *
\subsection{Lambdas}
*                                                                      *
************************************************************************
-}

{- Note [Optimising reflexivity]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
It's important (for compiler performance) to get rid of reflexivity as soon
as it appears.  See Trac #11735, #14737, and #15019.

In particular, we want to behave well on

 *  e |> co1 |> co2
    where the two happen to cancel out entirely. That is quite common;
    e.g. a newtype wrapping and unwrapping cancel.


 * (f |> co) @t1 @t2 ... @tn x1 .. xm
   Here we wil use pushCoTyArg and pushCoValArg successively, which
   build up NthCo stacks.  Silly to do that if co is reflexive.

However, we don't want to call isReflexiveCo too much, because it uses
type equality which is expensive on big types (Trac #14737 comment:7).

A good compromise (determined experimentally) seems to be to call
isReflexiveCo
 * when composing casts, and
 * at the end

In investigating this I saw missed opportunities for on-the-fly
coercion shrinkage. See Trac #15090.
-}


simplCast :: SimplEnv -> InExpr -> Coercion -> SimplCont
          -> SimplM (SimplFloats, OutExpr)
simplCast :: SimplEnv
-> Expr InBndr
-> Coercion
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
simplCast env :: SimplEnv
env body :: Expr InBndr
body co0 :: Coercion
co0 cont0 :: SimplCont
cont0
  = do  { Coercion
co1   <- {-#SCC "simplCast-simplCoercion" #-} SimplEnv -> Coercion -> SimplM Coercion
simplCoercion SimplEnv
env Coercion
co0
        ; SimplCont
cont1 <- {-#SCC "simplCast-addCoerce" #-}
                   if Coercion -> Bool
isReflCo Coercion
co1
                   then SimplCont -> SimplM SimplCont
forall (m :: * -> *) a. Monad m => a -> m a
return SimplCont
cont0  -- See Note [Optimising reflexivity]
                   else Coercion -> SimplCont -> SimplM SimplCont
addCoerce Coercion
co1 SimplCont
cont0
        ; {-#SCC "simplCast-simplExprF" #-} SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF SimplEnv
env Expr InBndr
body SimplCont
cont1 }
  where
        -- If the first parameter is MRefl, then simplifying revealed a
        -- reflexive coercion. Omit.
        addCoerceM :: MOutCoercion -> SimplCont -> SimplM SimplCont
        addCoerceM :: MOutCoercion -> SimplCont -> SimplM SimplCont
addCoerceM MRefl   cont :: SimplCont
cont = SimplCont -> SimplM SimplCont
forall (m :: * -> *) a. Monad m => a -> m a
return SimplCont
cont
        addCoerceM (MCo co :: Coercion
co) cont :: SimplCont
cont = Coercion -> SimplCont -> SimplM SimplCont
addCoerce Coercion
co SimplCont
cont

        addCoerce :: OutCoercion -> SimplCont -> SimplM SimplCont
        addCoerce :: Coercion -> SimplCont -> SimplM SimplCont
addCoerce co1 :: Coercion
co1 (CastIt co2 :: Coercion
co2 cont :: SimplCont
cont)  -- See Note [Optimising reflexivity]
          | Coercion -> Bool
isReflexiveCo Coercion
co' = SimplCont -> SimplM SimplCont
forall (m :: * -> *) a. Monad m => a -> m a
return SimplCont
cont
          | Bool
otherwise         = Coercion -> SimplCont -> SimplM SimplCont
addCoerce Coercion
co' SimplCont
cont
          where
            co' :: Coercion
co' = Coercion -> Coercion -> Coercion
mkTransCo Coercion
co1 Coercion
co2

        addCoerce co :: Coercion
co cont :: SimplCont
cont@(ApplyToTy { sc_arg_ty :: SimplCont -> OutType
sc_arg_ty = OutType
arg_ty, sc_cont :: SimplCont -> SimplCont
sc_cont = SimplCont
tail })
          | Just (arg_ty' :: OutType
arg_ty', m_co' :: MOutCoercion
m_co') <- Coercion -> OutType -> Maybe (OutType, MOutCoercion)
pushCoTyArg Coercion
co OutType
arg_ty
          , Pair hole_ty :: OutType
hole_ty _ <- Coercion -> Pair OutType
coercionKind Coercion
co
          = {-#SCC "addCoerce-pushCoTyArg" #-}
            do { SimplCont
tail' <- MOutCoercion -> SimplCont -> SimplM SimplCont
addCoerceM MOutCoercion
m_co' SimplCont
tail
               ; SimplCont -> SimplM SimplCont
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplCont
cont { sc_arg_ty :: OutType
sc_arg_ty  = OutType
arg_ty'
                              , sc_hole_ty :: OutType
sc_hole_ty = OutType
hole_ty  -- NB!  As the cast goes past, the
                                                      -- type of the hole changes (#16312)
                              , sc_cont :: SimplCont
sc_cont    = SimplCont
tail' }) }

        addCoerce co :: Coercion
co cont :: SimplCont
cont@(ApplyToVal { sc_arg :: SimplCont -> Expr InBndr
sc_arg = Expr InBndr
arg, sc_env :: SimplCont -> SimplEnv
sc_env = SimplEnv
arg_se
                                      , sc_dup :: SimplCont -> DupFlag
sc_dup = DupFlag
dup, sc_cont :: SimplCont -> SimplCont
sc_cont = SimplCont
tail })
          | Just (co1 :: Coercion
co1, m_co2 :: MOutCoercion
m_co2) <- Coercion -> Maybe (Coercion, MOutCoercion)
pushCoValArg Coercion
co
          , Pair _ new_ty :: OutType
new_ty <- Coercion -> Pair OutType
coercionKind Coercion
co1
          , Bool -> Bool
not (OutType -> Bool
isTypeLevPoly OutType
new_ty)  -- Without this check, we get a lev-poly arg
                                        -- See Note [Levity polymorphism invariants] in CoreSyn
                                        -- test: typecheck/should_run/EtaExpandLevPoly
          = {-#SCC "addCoerce-pushCoValArg" #-}
            do { SimplCont
tail' <- MOutCoercion -> SimplCont -> SimplM SimplCont
addCoerceM MOutCoercion
m_co2 SimplCont
tail
               ; if Coercion -> Bool
isReflCo Coercion
co1
                 then SimplCont -> SimplM SimplCont
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplCont
cont { sc_cont :: SimplCont
sc_cont = SimplCont
tail' })
                      -- Avoid simplifying if possible;
                      -- See Note [Avoiding exponential behaviour]
                 else do
               { (dup' :: DupFlag
dup', arg_se' :: SimplEnv
arg_se', arg' :: Expr InBndr
arg') <- SimplEnv
-> DupFlag
-> SimplEnv
-> Expr InBndr
-> SimplM (DupFlag, SimplEnv, Expr InBndr)
simplArg SimplEnv
env DupFlag
dup SimplEnv
arg_se Expr InBndr
arg
                    -- When we build the ApplyTo we can't mix the OutCoercion
                    -- 'co' with the InExpr 'arg', so we simplify
                    -- to make it all consistent.  It's a bit messy.
                    -- But it isn't a common case.
                    -- Example of use: Trac #995
               ; SimplCont -> SimplM SimplCont
forall (m :: * -> *) a. Monad m => a -> m a
return (ApplyToVal :: DupFlag -> Expr InBndr -> SimplEnv -> SimplCont -> SimplCont
ApplyToVal { sc_arg :: Expr InBndr
sc_arg  = Expr InBndr -> Coercion -> Expr InBndr
mkCast Expr InBndr
arg' Coercion
co1
                                    , sc_env :: SimplEnv
sc_env  = SimplEnv
arg_se'
                                    , sc_dup :: DupFlag
sc_dup  = DupFlag
dup'
                                    , sc_cont :: SimplCont
sc_cont = SimplCont
tail' }) } }

        addCoerce co :: Coercion
co cont :: SimplCont
cont
          | Coercion -> Bool
isReflexiveCo Coercion
co = SimplCont -> SimplM SimplCont
forall (m :: * -> *) a. Monad m => a -> m a
return SimplCont
cont  -- Having this at the end makes a huge
                                            -- difference in T12227, for some reason
                                            -- See Note [Optimising reflexivity]
          | Bool
otherwise        = SimplCont -> SimplM SimplCont
forall (m :: * -> *) a. Monad m => a -> m a
return (Coercion -> SimplCont -> SimplCont
CastIt Coercion
co SimplCont
cont)

simplArg :: SimplEnv -> DupFlag -> StaticEnv -> CoreExpr
         -> SimplM (DupFlag, StaticEnv, OutExpr)
simplArg :: SimplEnv
-> DupFlag
-> SimplEnv
-> Expr InBndr
-> SimplM (DupFlag, SimplEnv, Expr InBndr)
simplArg env :: SimplEnv
env dup_flag :: DupFlag
dup_flag arg_env :: SimplEnv
arg_env arg :: Expr InBndr
arg
  | DupFlag -> Bool
isSimplified DupFlag
dup_flag
  = (DupFlag, SimplEnv, Expr InBndr)
-> SimplM (DupFlag, SimplEnv, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (DupFlag
dup_flag, SimplEnv
arg_env, Expr InBndr
arg)
  | Bool
otherwise
  = do { Expr InBndr
arg' <- SimplEnv -> Expr InBndr -> SimplM (Expr InBndr)
simplExpr (SimplEnv
arg_env SimplEnv -> SimplEnv -> SimplEnv
`setInScopeFromE` SimplEnv
env) Expr InBndr
arg
       ; (DupFlag, SimplEnv, Expr InBndr)
-> SimplM (DupFlag, SimplEnv, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (DupFlag
Simplified, SimplEnv -> SimplEnv
zapSubstEnv SimplEnv
arg_env, Expr InBndr
arg') }

{-
************************************************************************
*                                                                      *
\subsection{Lambdas}
*                                                                      *
************************************************************************
-}

simplLam :: SimplEnv -> [InId] -> InExpr -> SimplCont
         -> SimplM (SimplFloats, OutExpr)

simplLam :: SimplEnv
-> [InBndr]
-> Expr InBndr
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
simplLam env :: SimplEnv
env [] body :: Expr InBndr
body cont :: SimplCont
cont
  = SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF SimplEnv
env Expr InBndr
body SimplCont
cont

simplLam env :: SimplEnv
env (bndr :: InBndr
bndr:bndrs :: [InBndr]
bndrs) body :: Expr InBndr
body (ApplyToTy { sc_arg_ty :: SimplCont -> OutType
sc_arg_ty = OutType
arg_ty, sc_cont :: SimplCont -> SimplCont
sc_cont = SimplCont
cont })
  = do { Tick -> SimplM ()
tick (InBndr -> Tick
BetaReduction InBndr
bndr)
       ; SimplEnv
-> [InBndr]
-> Expr InBndr
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
simplLam (SimplEnv -> InBndr -> OutType -> SimplEnv
extendTvSubst SimplEnv
env InBndr
bndr OutType
arg_ty) [InBndr]
bndrs Expr InBndr
body SimplCont
cont }

simplLam env :: SimplEnv
env (bndr :: InBndr
bndr:bndrs :: [InBndr]
bndrs) body :: Expr InBndr
body (ApplyToVal { sc_arg :: SimplCont -> Expr InBndr
sc_arg = Expr InBndr
arg, sc_env :: SimplCont -> SimplEnv
sc_env = SimplEnv
arg_se
                                           , sc_cont :: SimplCont -> SimplCont
sc_cont = SimplCont
cont, sc_dup :: SimplCont -> DupFlag
sc_dup = DupFlag
dup })
  | DupFlag -> Bool
isSimplified DupFlag
dup  -- Don't re-simplify if we've simplified it once
                      -- See Note [Avoiding exponential behaviour]
  = do  { Tick -> SimplM ()
tick (InBndr -> Tick
BetaReduction InBndr
bndr)
        ; (floats1 :: SimplFloats
floats1, env' :: SimplEnv
env') <- SimplEnv -> InBndr -> Expr InBndr -> SimplM (SimplFloats, SimplEnv)
simplNonRecX SimplEnv
env InBndr
zapped_bndr Expr InBndr
arg
        ; (floats2 :: SimplFloats
floats2, expr' :: Expr InBndr
expr') <- SimplEnv
-> [InBndr]
-> Expr InBndr
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
simplLam SimplEnv
env' [InBndr]
bndrs Expr InBndr
body SimplCont
cont
        ; (SimplFloats, Expr InBndr) -> SimplM (SimplFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats
floats1 SimplFloats -> SimplFloats -> SimplFloats
`addFloats` SimplFloats
floats2, Expr InBndr
expr') }

  | Bool
otherwise
  = do  { Tick -> SimplM ()
tick (InBndr -> Tick
BetaReduction InBndr
bndr)
        ; SimplEnv
-> InBndr
-> (Expr InBndr, SimplEnv)
-> ([InBndr], Expr InBndr)
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
simplNonRecE SimplEnv
env InBndr
zapped_bndr (Expr InBndr
arg, SimplEnv
arg_se) ([InBndr]
bndrs, Expr InBndr
body) SimplCont
cont }
  where
    zapped_bndr :: InBndr
zapped_bndr  -- See Note [Zap unfolding when beta-reducing]
      | InBndr -> Bool
isId InBndr
bndr = InBndr -> InBndr
zapStableUnfolding InBndr
bndr
      | Bool
otherwise = InBndr
bndr

      -- Discard a non-counting tick on a lambda.  This may change the
      -- cost attribution slightly (moving the allocation of the
      -- lambda elsewhere), but we don't care: optimisation changes
      -- cost attribution all the time.
simplLam env :: SimplEnv
env bndrs :: [InBndr]
bndrs body :: Expr InBndr
body (TickIt tickish :: Tickish InBndr
tickish cont :: SimplCont
cont)
  | Bool -> Bool
not (Tickish InBndr -> Bool
forall id. Tickish id -> Bool
tickishCounts Tickish InBndr
tickish)
  = SimplEnv
-> [InBndr]
-> Expr InBndr
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
simplLam SimplEnv
env [InBndr]
bndrs Expr InBndr
body SimplCont
cont

        -- Not enough args, so there are real lambdas left to put in the result
simplLam env :: SimplEnv
env bndrs :: [InBndr]
bndrs body :: Expr InBndr
body cont :: SimplCont
cont
  = do  { (env' :: SimplEnv
env', bndrs' :: [InBndr]
bndrs') <- SimplEnv -> [InBndr] -> SimplM (SimplEnv, [InBndr])
simplLamBndrs SimplEnv
env [InBndr]
bndrs
        ; Expr InBndr
body' <- SimplEnv -> Expr InBndr -> SimplM (Expr InBndr)
simplExpr SimplEnv
env' Expr InBndr
body
        ; Expr InBndr
new_lam <- SimplEnv
-> [InBndr] -> Expr InBndr -> SimplCont -> SimplM (Expr InBndr)
mkLam SimplEnv
env [InBndr]
bndrs' Expr InBndr
body' SimplCont
cont
        ; SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
rebuild SimplEnv
env' Expr InBndr
new_lam SimplCont
cont }

-------------
simplLamBndr :: SimplEnv -> InBndr -> SimplM (SimplEnv, OutBndr)
-- Used for lambda binders.  These sometimes have unfoldings added by
-- the worker/wrapper pass that must be preserved, because they can't
-- be reconstructed from context.  For example:
--      f x = case x of (a,b) -> fw a b x
--      fw a b x{=(a,b)} = ...
-- The "{=(a,b)}" is an unfolding we can't reconstruct otherwise.
simplLamBndr :: SimplEnv -> InBndr -> SimplM (SimplEnv, InBndr)
simplLamBndr env :: SimplEnv
env bndr :: InBndr
bndr
  | InBndr -> Bool
isId InBndr
bndr Bool -> Bool -> Bool
&& Unfolding -> Bool
isFragileUnfolding Unfolding
old_unf   -- Special case
  = do { (env1 :: SimplEnv
env1, bndr1 :: InBndr
bndr1) <- SimplEnv -> InBndr -> SimplM (SimplEnv, InBndr)
simplBinder SimplEnv
env InBndr
bndr
       ; Unfolding
unf'          <- SimplEnv
-> TopLevelFlag
-> MaybeJoinCont
-> InBndr
-> Unfolding
-> OutType
-> SimplM Unfolding
simplStableUnfolding SimplEnv
env1 TopLevelFlag
NotTopLevel MaybeJoinCont
forall a. Maybe a
Nothing InBndr
bndr
                                               Unfolding
old_unf (InBndr -> OutType
idType InBndr
bndr1)
       ; let bndr2 :: InBndr
bndr2 = InBndr
bndr1 InBndr -> Unfolding -> InBndr
`setIdUnfolding` Unfolding
unf'
       ; (SimplEnv, InBndr) -> SimplM (SimplEnv, InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplEnv -> InBndr -> SimplEnv
modifyInScope SimplEnv
env1 InBndr
bndr2, InBndr
bndr2) }

  | Bool
otherwise
  = SimplEnv -> InBndr -> SimplM (SimplEnv, InBndr)
simplBinder SimplEnv
env InBndr
bndr                -- Normal case
  where
    old_unf :: Unfolding
old_unf = InBndr -> Unfolding
idUnfolding InBndr
bndr

simplLamBndrs :: SimplEnv -> [InBndr] -> SimplM (SimplEnv, [OutBndr])
simplLamBndrs :: SimplEnv -> [InBndr] -> SimplM (SimplEnv, [InBndr])
simplLamBndrs env :: SimplEnv
env bndrs :: [InBndr]
bndrs = (SimplEnv -> InBndr -> SimplM (SimplEnv, InBndr))
-> SimplEnv -> [InBndr] -> SimplM (SimplEnv, [InBndr])
forall (m :: * -> *) acc x y.
Monad m =>
(acc -> x -> m (acc, y)) -> acc -> [x] -> m (acc, [y])
mapAccumLM SimplEnv -> InBndr -> SimplM (SimplEnv, InBndr)
simplLamBndr SimplEnv
env [InBndr]
bndrs

------------------
simplNonRecE :: SimplEnv
             -> InId                    -- The binder, always an Id
                                        -- Never a join point
             -> (InExpr, SimplEnv)      -- Rhs of binding (or arg of lambda)
             -> ([InBndr], InExpr)      -- Body of the let/lambda
                                        --      \xs.e
             -> SimplCont
             -> SimplM (SimplFloats, OutExpr)

-- simplNonRecE is used for
--  * non-top-level non-recursive non-join-point lets in expressions
--  * beta reduction
--
-- simplNonRec env b (rhs, rhs_se) (bs, body) k
--   = let env in
--     cont< let b = rhs_se(rhs) in \bs.body >
--
-- It deals with strict bindings, via the StrictBind continuation,
-- which may abort the whole process
--
-- Precondition: rhs satisfies the let/app invariant
--               Note [CoreSyn let/app invariant] in CoreSyn
--
-- The "body" of the binding comes as a pair of ([InId],InExpr)
-- representing a lambda; so we recurse back to simplLam
-- Why?  Because of the binder-occ-info-zapping done before
--       the call to simplLam in simplExprF (Lam ...)

simplNonRecE :: SimplEnv
-> InBndr
-> (Expr InBndr, SimplEnv)
-> ([InBndr], Expr InBndr)
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
simplNonRecE env :: SimplEnv
env bndr :: InBndr
bndr (rhs :: Expr InBndr
rhs, rhs_se :: SimplEnv
rhs_se) (bndrs :: [InBndr]
bndrs, body :: Expr InBndr
body) cont :: SimplCont
cont
  | ASSERT( isId bndr && not (isJoinId bndr) ) True
  , Just env' :: SimplEnv
env' <- SimplEnv
-> TopLevelFlag
-> InBndr
-> Expr InBndr
-> SimplEnv
-> Maybe SimplEnv
preInlineUnconditionally SimplEnv
env TopLevelFlag
NotTopLevel InBndr
bndr Expr InBndr
rhs SimplEnv
rhs_se
  = do { Tick -> SimplM ()
tick (InBndr -> Tick
PreInlineUnconditionally InBndr
bndr)
       ; -- pprTrace "preInlineUncond" (ppr bndr <+> ppr rhs) $
         SimplEnv
-> [InBndr]
-> Expr InBndr
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
simplLam SimplEnv
env' [InBndr]
bndrs Expr InBndr
body SimplCont
cont }

  -- Deal with strict bindings
  | InBndr -> Bool
isStrictId InBndr
bndr          -- Includes coercions
  , SimplMode -> Bool
sm_case_case (SimplEnv -> SimplMode
getMode SimplEnv
env)
  = SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF (SimplEnv
rhs_se SimplEnv -> SimplEnv -> SimplEnv
`setInScopeFromE` SimplEnv
env) Expr InBndr
rhs
               (StrictBind :: DupFlag
-> InBndr
-> [InBndr]
-> Expr InBndr
-> SimplEnv
-> SimplCont
-> SimplCont
StrictBind { sc_bndr :: InBndr
sc_bndr = InBndr
bndr, sc_bndrs :: [InBndr]
sc_bndrs = [InBndr]
bndrs, sc_body :: Expr InBndr
sc_body = Expr InBndr
body
                           , sc_env :: SimplEnv
sc_env = SimplEnv
env, sc_cont :: SimplCont
sc_cont = SimplCont
cont, sc_dup :: DupFlag
sc_dup = DupFlag
NoDup })

  -- Deal with lazy bindings
  | Bool
otherwise
  = ASSERT( not (isTyVar bndr) )
    do { (env1 :: SimplEnv
env1, bndr1 :: InBndr
bndr1) <- SimplEnv -> InBndr -> SimplM (SimplEnv, InBndr)
simplNonRecBndr SimplEnv
env InBndr
bndr
       ; (env2 :: SimplEnv
env2, bndr2 :: InBndr
bndr2) <- SimplEnv
-> InBndr -> InBndr -> MaybeJoinCont -> SimplM (SimplEnv, InBndr)
addBndrRules SimplEnv
env1 InBndr
bndr InBndr
bndr1 MaybeJoinCont
forall a. Maybe a
Nothing
       ; (floats1 :: SimplFloats
floats1, env3 :: SimplEnv
env3) <- SimplEnv
-> TopLevelFlag
-> RecFlag
-> InBndr
-> InBndr
-> Expr InBndr
-> SimplEnv
-> SimplM (SimplFloats, SimplEnv)
simplLazyBind SimplEnv
env2 TopLevelFlag
NotTopLevel RecFlag
NonRecursive InBndr
bndr InBndr
bndr2 Expr InBndr
rhs SimplEnv
rhs_se
       ; (floats2 :: SimplFloats
floats2, expr' :: Expr InBndr
expr') <- SimplEnv
-> [InBndr]
-> Expr InBndr
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
simplLam SimplEnv
env3 [InBndr]
bndrs Expr InBndr
body SimplCont
cont
       ; (SimplFloats, Expr InBndr) -> SimplM (SimplFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats
floats1 SimplFloats -> SimplFloats -> SimplFloats
`addFloats` SimplFloats
floats2, Expr InBndr
expr') }

------------------
simplRecE :: SimplEnv
          -> [(InId, InExpr)]
          -> InExpr
          -> SimplCont
          -> SimplM (SimplFloats, OutExpr)

-- simplRecE is used for
--  * non-top-level recursive lets in expressions
simplRecE :: SimplEnv
-> [(InBndr, Expr InBndr)]
-> Expr InBndr
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
simplRecE env :: SimplEnv
env pairs :: [(InBndr, Expr InBndr)]
pairs body :: Expr InBndr
body cont :: SimplCont
cont
  = do  { let bndrs :: [InBndr]
bndrs = ((InBndr, Expr InBndr) -> InBndr)
-> [(InBndr, Expr InBndr)] -> [InBndr]
forall a b. (a -> b) -> [a] -> [b]
map (InBndr, Expr InBndr) -> InBndr
forall a b. (a, b) -> a
fst [(InBndr, Expr InBndr)]
pairs
        ; MASSERT(all (not . isJoinId) bndrs)
        ; SimplEnv
env1 <- SimplEnv -> [InBndr] -> SimplM SimplEnv
simplRecBndrs SimplEnv
env [InBndr]
bndrs
                -- NB: bndrs' don't have unfoldings or rules
                -- We add them as we go down
        ; (floats1 :: SimplFloats
floats1, env2 :: SimplEnv
env2) <- SimplEnv
-> TopLevelFlag
-> MaybeJoinCont
-> [(InBndr, Expr InBndr)]
-> SimplM (SimplFloats, SimplEnv)
simplRecBind SimplEnv
env1 TopLevelFlag
NotTopLevel MaybeJoinCont
forall a. Maybe a
Nothing [(InBndr, Expr InBndr)]
pairs
        ; (floats2 :: SimplFloats
floats2, expr' :: Expr InBndr
expr') <- SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF SimplEnv
env2 Expr InBndr
body SimplCont
cont
        ; (SimplFloats, Expr InBndr) -> SimplM (SimplFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats
floats1 SimplFloats -> SimplFloats -> SimplFloats
`addFloats` SimplFloats
floats2, Expr InBndr
expr') }

{- Note [Avoiding exponential behaviour]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
One way in which we can get exponential behaviour is if we simplify a
big expression, and the re-simplify it -- and then this happens in a
deeply-nested way.  So we must be jolly careful about re-simplifying
an expression.  That is why completeNonRecX does not try
preInlineUnconditionally.

Example:
  f BIG, where f has a RULE
Then
 * We simplify BIG before trying the rule; but the rule does not fire
 * We inline f = \x. x True
 * So if we did preInlineUnconditionally we'd re-simplify (BIG True)

However, if BIG has /not/ already been simplified, we'd /like/ to
simplify BIG True; maybe good things happen.  That is why

* simplLam has
    - a case for (isSimplified dup), which goes via simplNonRecX, and
    - a case for the un-simplified case, which goes via simplNonRecE

* We go to some efforts to avoid unnecessarily simplifying ApplyToVal,
  in at least two places
    - In simplCast/addCoerce, where we check for isReflCo
    - In rebuildCall we avoid simplifying arguments before we have to
      (see Note [Trying rewrite rules])


Note [Zap unfolding when beta-reducing]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Lambda-bound variables can have stable unfoldings, such as
   $j = \x. \b{Unf=Just x}. e
See Note [Case binders and join points] below; the unfolding for lets
us optimise e better.  However when we beta-reduce it we want to
revert to using the actual value, otherwise we can end up in the
stupid situation of
          let x = blah in
          let b{Unf=Just x} = y
          in ...b...
Here it'd be far better to drop the unfolding and use the actual RHS.

************************************************************************
*                                                                      *
                     Join points
*                                                                      *
********************************************************************* -}

{- Note [Rules and unfolding for join points]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Suppose we have

   simplExpr (join j x = rhs                         ) cont
             (      {- RULE j (p:ps) = blah -}       )
             (      {- StableUnfolding j = blah -}   )
             (in blah                                )

Then we will push 'cont' into the rhs of 'j'.  But we should *also* push
'cont' into the RHS of
  * Any RULEs for j, e.g. generated by SpecConstr
  * Any stable unfolding for j, e.g. the result of an INLINE pragma

Simplifying rules and stable-unfoldings happens a bit after
simplifying the right-hand side, so we remember whether or not it
is a join point, and what 'cont' is, in a value of type MaybeJoinCont

Trac #13900 wsa caused by forgetting to push 'cont' into the RHS
of a SpecConstr-generated RULE for a join point.
-}

type MaybeJoinCont = Maybe SimplCont
  -- Nothing => Not a join point
  -- Just k  => This is a join binding with continuation k
  -- See Note [Rules and unfolding for join points]

simplNonRecJoinPoint :: SimplEnv -> InId -> InExpr
                     -> InExpr -> SimplCont
                     -> SimplM (SimplFloats, OutExpr)
simplNonRecJoinPoint :: SimplEnv
-> InBndr
-> Expr InBndr
-> Expr InBndr
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
simplNonRecJoinPoint env :: SimplEnv
env bndr :: InBndr
bndr rhs :: Expr InBndr
rhs body :: Expr InBndr
body cont :: SimplCont
cont
  | ASSERT( isJoinId bndr ) True
  , Just env' :: SimplEnv
env' <- SimplEnv
-> TopLevelFlag
-> InBndr
-> Expr InBndr
-> SimplEnv
-> Maybe SimplEnv
preInlineUnconditionally SimplEnv
env TopLevelFlag
NotTopLevel InBndr
bndr Expr InBndr
rhs SimplEnv
env
  = do { Tick -> SimplM ()
tick (InBndr -> Tick
PreInlineUnconditionally InBndr
bndr)
       ; SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF SimplEnv
env' Expr InBndr
body SimplCont
cont }

   | Bool
otherwise
   = SimplEnv
-> SimplCont
-> (SimplEnv -> SimplCont -> SimplM (SimplFloats, Expr InBndr))
-> SimplM (SimplFloats, Expr InBndr)
wrapJoinCont SimplEnv
env SimplCont
cont ((SimplEnv -> SimplCont -> SimplM (SimplFloats, Expr InBndr))
 -> SimplM (SimplFloats, Expr InBndr))
-> (SimplEnv -> SimplCont -> SimplM (SimplFloats, Expr InBndr))
-> SimplM (SimplFloats, Expr InBndr)
forall a b. (a -> b) -> a -> b
$ \ env :: SimplEnv
env cont :: SimplCont
cont ->
     do { -- We push join_cont into the join RHS and the body;
          -- and wrap wrap_cont around the whole thing
        ; let res_ty :: OutType
res_ty = SimplCont -> OutType
contResultType SimplCont
cont
        ; (env1 :: SimplEnv
env1, bndr1 :: InBndr
bndr1)    <- SimplEnv -> OutType -> InBndr -> SimplM (SimplEnv, InBndr)
simplNonRecJoinBndr SimplEnv
env OutType
res_ty InBndr
bndr
        ; (env2 :: SimplEnv
env2, bndr2 :: InBndr
bndr2)    <- SimplEnv
-> InBndr -> InBndr -> MaybeJoinCont -> SimplM (SimplEnv, InBndr)
addBndrRules SimplEnv
env1 InBndr
bndr InBndr
bndr1 (SimplCont -> MaybeJoinCont
forall a. a -> Maybe a
Just SimplCont
cont)
        ; (floats1 :: SimplFloats
floats1, env3 :: SimplEnv
env3)  <- SimplEnv
-> SimplCont
-> InBndr
-> InBndr
-> Expr InBndr
-> SimplEnv
-> SimplM (SimplFloats, SimplEnv)
simplJoinBind SimplEnv
env2 SimplCont
cont InBndr
bndr InBndr
bndr2 Expr InBndr
rhs SimplEnv
env
        ; (floats2 :: SimplFloats
floats2, body' :: Expr InBndr
body') <- SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF SimplEnv
env3 Expr InBndr
body SimplCont
cont
        ; (SimplFloats, Expr InBndr) -> SimplM (SimplFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats
floats1 SimplFloats -> SimplFloats -> SimplFloats
`addFloats` SimplFloats
floats2, Expr InBndr
body') }


------------------
simplRecJoinPoint :: SimplEnv -> [(InId, InExpr)]
                  -> InExpr -> SimplCont
                  -> SimplM (SimplFloats, OutExpr)
simplRecJoinPoint :: SimplEnv
-> [(InBndr, Expr InBndr)]
-> Expr InBndr
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
simplRecJoinPoint env :: SimplEnv
env pairs :: [(InBndr, Expr InBndr)]
pairs body :: Expr InBndr
body cont :: SimplCont
cont
  = SimplEnv
-> SimplCont
-> (SimplEnv -> SimplCont -> SimplM (SimplFloats, Expr InBndr))
-> SimplM (SimplFloats, Expr InBndr)
wrapJoinCont SimplEnv
env SimplCont
cont ((SimplEnv -> SimplCont -> SimplM (SimplFloats, Expr InBndr))
 -> SimplM (SimplFloats, Expr InBndr))
-> (SimplEnv -> SimplCont -> SimplM (SimplFloats, Expr InBndr))
-> SimplM (SimplFloats, Expr InBndr)
forall a b. (a -> b) -> a -> b
$ \ env :: SimplEnv
env cont :: SimplCont
cont ->
    do { let bndrs :: [InBndr]
bndrs = ((InBndr, Expr InBndr) -> InBndr)
-> [(InBndr, Expr InBndr)] -> [InBndr]
forall a b. (a -> b) -> [a] -> [b]
map (InBndr, Expr InBndr) -> InBndr
forall a b. (a, b) -> a
fst [(InBndr, Expr InBndr)]
pairs
             res_ty :: OutType
res_ty = SimplCont -> OutType
contResultType SimplCont
cont
       ; SimplEnv
env1 <- SimplEnv -> OutType -> [InBndr] -> SimplM SimplEnv
simplRecJoinBndrs SimplEnv
env OutType
res_ty [InBndr]
bndrs
               -- NB: bndrs' don't have unfoldings or rules
               -- We add them as we go down
       ; (floats1 :: SimplFloats
floats1, env2 :: SimplEnv
env2)  <- SimplEnv
-> TopLevelFlag
-> MaybeJoinCont
-> [(InBndr, Expr InBndr)]
-> SimplM (SimplFloats, SimplEnv)
simplRecBind SimplEnv
env1 TopLevelFlag
NotTopLevel (SimplCont -> MaybeJoinCont
forall a. a -> Maybe a
Just SimplCont
cont) [(InBndr, Expr InBndr)]
pairs
       ; (floats2 :: SimplFloats
floats2, body' :: Expr InBndr
body') <- SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF SimplEnv
env2 Expr InBndr
body SimplCont
cont
       ; (SimplFloats, Expr InBndr) -> SimplM (SimplFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats
floats1 SimplFloats -> SimplFloats -> SimplFloats
`addFloats` SimplFloats
floats2, Expr InBndr
body') }

--------------------
wrapJoinCont :: SimplEnv -> SimplCont
             -> (SimplEnv -> SimplCont -> SimplM (SimplFloats, OutExpr))
             -> SimplM (SimplFloats, OutExpr)
-- Deal with making the continuation duplicable if necessary,
-- and with the no-case-of-case situation.
wrapJoinCont :: SimplEnv
-> SimplCont
-> (SimplEnv -> SimplCont -> SimplM (SimplFloats, Expr InBndr))
-> SimplM (SimplFloats, Expr InBndr)
wrapJoinCont env :: SimplEnv
env cont :: SimplCont
cont thing_inside :: SimplEnv -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
thing_inside
  | SimplCont -> Bool
contIsStop SimplCont
cont        -- Common case; no need for fancy footwork
  = SimplEnv -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
thing_inside SimplEnv
env SimplCont
cont

  | Bool -> Bool
not (SimplMode -> Bool
sm_case_case (SimplEnv -> SimplMode
getMode SimplEnv
env))
    -- See Note [Join points wih -fno-case-of-case]
  = do { (floats1 :: SimplFloats
floats1, expr1 :: Expr InBndr
expr1) <- SimplEnv -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
thing_inside SimplEnv
env (OutType -> SimplCont
mkBoringStop (SimplCont -> OutType
contHoleType SimplCont
cont))
       ; let (floats2 :: SimplFloats
floats2, expr2 :: Expr InBndr
expr2) = SimplFloats -> Expr InBndr -> (SimplFloats, Expr InBndr)
wrapJoinFloatsX SimplFloats
floats1 Expr InBndr
expr1
       ; (floats3 :: SimplFloats
floats3, expr3 :: Expr InBndr
expr3) <- SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
rebuild (SimplEnv
env SimplEnv -> SimplFloats -> SimplEnv
`setInScopeFromF` SimplFloats
floats2) Expr InBndr
expr2 SimplCont
cont
       ; (SimplFloats, Expr InBndr) -> SimplM (SimplFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats
floats2 SimplFloats -> SimplFloats -> SimplFloats
`addFloats` SimplFloats
floats3, Expr InBndr
expr3) }

  | Bool
otherwise
    -- Normal case; see Note [Join points and case-of-case]
  = do { (floats1 :: SimplFloats
floats1, cont' :: SimplCont
cont')  <- SimplEnv -> SimplCont -> SimplM (SimplFloats, SimplCont)
mkDupableCont SimplEnv
env SimplCont
cont
       ; (floats2 :: SimplFloats
floats2, result :: Expr InBndr
result) <- SimplEnv -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
thing_inside (SimplEnv
env SimplEnv -> SimplFloats -> SimplEnv
`setInScopeFromF` SimplFloats
floats1) SimplCont
cont'
       ; (SimplFloats, Expr InBndr) -> SimplM (SimplFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats
floats1 SimplFloats -> SimplFloats -> SimplFloats
`addFloats` SimplFloats
floats2, Expr InBndr
result) }


--------------------
trimJoinCont :: Id -> Maybe JoinArity -> SimplCont -> SimplCont
-- Drop outer context from join point invocation (jump)
-- See Note [Join points and case-of-case]

trimJoinCont :: InBndr -> Maybe Int -> SimplCont -> SimplCont
trimJoinCont _ Nothing cont :: SimplCont
cont
  = SimplCont
cont -- Not a jump
trimJoinCont var :: InBndr
var (Just arity :: Int
arity) cont :: SimplCont
cont
  = Int -> SimplCont -> SimplCont
forall a. (Eq a, Num a) => a -> SimplCont -> SimplCont
trim Int
arity SimplCont
cont
  where
    trim :: a -> SimplCont -> SimplCont
trim 0 cont :: SimplCont
cont@(Stop {})
      = SimplCont
cont
    trim 0 cont :: SimplCont
cont
      = OutType -> SimplCont
mkBoringStop (SimplCont -> OutType
contResultType SimplCont
cont)
    trim n :: a
n cont :: SimplCont
cont@(ApplyToVal { sc_cont :: SimplCont -> SimplCont
sc_cont = SimplCont
k })
      = SimplCont
cont { sc_cont :: SimplCont
sc_cont = a -> SimplCont -> SimplCont
trim (a
na -> a -> a
forall a. Num a => a -> a -> a
-1) SimplCont
k }
    trim n :: a
n cont :: SimplCont
cont@(ApplyToTy { sc_cont :: SimplCont -> SimplCont
sc_cont = SimplCont
k })
      = SimplCont
cont { sc_cont :: SimplCont
sc_cont = a -> SimplCont -> SimplCont
trim (a
na -> a -> a
forall a. Num a => a -> a -> a
-1) SimplCont
k } -- join arity counts types!
    trim _ cont :: SimplCont
cont
      = [Char] -> SDoc -> SimplCont
forall a. HasCallStack => [Char] -> SDoc -> a
pprPanic "completeCall" (SDoc -> SimplCont) -> SDoc -> SimplCont
forall a b. (a -> b) -> a -> b
$ InBndr -> SDoc
forall a. Outputable a => a -> SDoc
ppr InBndr
var SDoc -> SDoc -> SDoc
$$ SimplCont -> SDoc
forall a. Outputable a => a -> SDoc
ppr SimplCont
cont


{- Note [Join points and case-of-case]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When we perform the case-of-case transform (or otherwise push continuations
inward), we want to treat join points specially. Since they're always
tail-called and we want to maintain this invariant, we can do this (for any
evaluation context E):

  E[join j = e
    in case ... of
         A -> jump j 1
         B -> jump j 2
         C -> f 3]

    -->

  join j = E[e]
  in case ... of
       A -> jump j 1
       B -> jump j 2
       C -> E[f 3]

As is evident from the example, there are two components to this behavior:

  1. When entering the RHS of a join point, copy the context inside.
  2. When a join point is invoked, discard the outer context.

We need to be very careful here to remain consistent---neither part is
optional!

We need do make the continuation E duplicable (since we are duplicating it)
with mkDuableCont.


Note [Join points wih -fno-case-of-case]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Supose case-of-case is switched off, and we are simplifying

    case (join j x = <j-rhs> in
          case y of
             A -> j 1
             B -> j 2
             C -> e) of <outer-alts>

Usually, we'd push the outer continuation (case . of <outer-alts>) into
both the RHS and the body of the join point j.  But since we aren't doing
case-of-case we may then end up with this totally bogus result

    join x = case <j-rhs> of <outer-alts> in
    case (case y of
             A -> j 1
             B -> j 2
             C -> e) of <outer-alts>

This would be OK in the language of the paper, but not in GHC: j is no longer
a join point.  We can only do the "push contination into the RHS of the
join point j" if we also push the contination right down to the /jumps/ to
j, so that it can evaporate there.  If we are doing case-of-case, we'll get to

    join x = case <j-rhs> of <outer-alts> in
    case y of
      A -> j 1
      B -> j 2
      C -> case e of <outer-alts>

which is great.

Bottom line: if case-of-case is off, we must stop pushing the continuation
inwards altogether at any join point.  Instead simplify the (join ... in ...)
with a Stop continuation, and wrap the original continuation around the
outside.  Surprisingly tricky!


************************************************************************
*                                                                      *
                     Variables
*                                                                      *
************************************************************************
-}

simplVar :: SimplEnv -> InVar -> SimplM OutExpr
-- Look up an InVar in the environment
simplVar :: SimplEnv -> InBndr -> SimplM (Expr InBndr)
simplVar env :: SimplEnv
env var :: InBndr
var
  | InBndr -> Bool
isTyVar InBndr
var = Expr InBndr -> SimplM (Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (OutType -> Expr InBndr
forall b. OutType -> Expr b
Type (SimplEnv -> InBndr -> OutType
substTyVar SimplEnv
env InBndr
var))
  | InBndr -> Bool
isCoVar InBndr
var = Expr InBndr -> SimplM (Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (Coercion -> Expr InBndr
forall b. Coercion -> Expr b
Coercion (SimplEnv -> InBndr -> Coercion
substCoVar SimplEnv
env InBndr
var))
  | Bool
otherwise
  = case SimplEnv -> InBndr -> SimplSR
substId SimplEnv
env InBndr
var of
        ContEx tvs :: TvSubstEnv
tvs cvs :: CvSubstEnv
cvs ids :: SimplIdSubst
ids e :: Expr InBndr
e -> SimplEnv -> Expr InBndr -> SimplM (Expr InBndr)
simplExpr (SimplEnv -> TvSubstEnv -> CvSubstEnv -> SimplIdSubst -> SimplEnv
setSubstEnv SimplEnv
env TvSubstEnv
tvs CvSubstEnv
cvs SimplIdSubst
ids) Expr InBndr
e
        DoneId var1 :: InBndr
var1          -> Expr InBndr -> SimplM (Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (InBndr -> Expr InBndr
forall b. InBndr -> Expr b
Var InBndr
var1)
        DoneEx e :: Expr InBndr
e _           -> Expr InBndr -> SimplM (Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return Expr InBndr
e

simplIdF :: SimplEnv -> InId -> SimplCont -> SimplM (SimplFloats, OutExpr)
simplIdF :: SimplEnv
-> InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplIdF env :: SimplEnv
env var :: InBndr
var cont :: SimplCont
cont
  = case SimplEnv -> InBndr -> SimplSR
substId SimplEnv
env InBndr
var of
      ContEx tvs :: TvSubstEnv
tvs cvs :: CvSubstEnv
cvs ids :: SimplIdSubst
ids e :: Expr InBndr
e -> SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF (SimplEnv -> TvSubstEnv -> CvSubstEnv -> SimplIdSubst -> SimplEnv
setSubstEnv SimplEnv
env TvSubstEnv
tvs CvSubstEnv
cvs SimplIdSubst
ids) Expr InBndr
e SimplCont
cont
                                -- Don't trim; haven't already simplified e,
                                -- so the cont is not embodied in e

      DoneId var1 :: InBndr
var1 -> SimplEnv
-> InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
completeCall SimplEnv
env InBndr
var1 (InBndr -> Maybe Int -> SimplCont -> SimplCont
trimJoinCont InBndr
var (InBndr -> Maybe Int
isJoinId_maybe InBndr
var1) SimplCont
cont)

      DoneEx e :: Expr InBndr
e mb_join :: Maybe Int
mb_join -> SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF (SimplEnv -> SimplEnv
zapSubstEnv SimplEnv
env) Expr InBndr
e (InBndr -> Maybe Int -> SimplCont -> SimplCont
trimJoinCont InBndr
var Maybe Int
mb_join SimplCont
cont)
              -- Note [zapSubstEnv]
              -- The template is already simplified, so don't re-substitute.
              -- This is VITAL.  Consider
              --      let x = e in
              --      let y = \z -> ...x... in
              --      \ x -> ...y...
              -- We'll clone the inner \x, adding x->x' in the id_subst
              -- Then when we inline y, we must *not* replace x by x' in
              -- the inlined copy!!

---------------------------------------------------------
--      Dealing with a call site

completeCall :: SimplEnv -> OutId -> SimplCont -> SimplM (SimplFloats, OutExpr)
completeCall :: SimplEnv
-> InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
completeCall env :: SimplEnv
env var :: InBndr
var cont :: SimplCont
cont
  | Just expr :: Expr InBndr
expr <- DynFlags
-> InBndr
-> Bool
-> Bool
-> [ArgSummary]
-> CallCtxt
-> Maybe (Expr InBndr)
callSiteInline DynFlags
dflags InBndr
var Bool
active_unf
                                Bool
lone_variable [ArgSummary]
arg_infos CallCtxt
interesting_cont
  -- Inline the variable's RHS
  = do { Tick -> SimplM ()
checkedTick (InBndr -> Tick
UnfoldingDone InBndr
var)
       ; Expr InBndr -> SimplCont -> SimplM ()
forall (m :: * -> *) a a.
(MonadIO m, Outputable a, Outputable a) =>
a -> a -> m ()
dump_inline Expr InBndr
expr SimplCont
cont
       ; SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF (SimplEnv -> SimplEnv
zapSubstEnv SimplEnv
env) Expr InBndr
expr SimplCont
cont }

  | Bool
otherwise
  -- Don't inline; instead rebuild the call
  = do { RuleEnv
rule_base <- SimplM RuleEnv
getSimplRules
       ; let info :: ArgInfo
info = SimplEnv -> InBndr -> [CoreRule] -> Int -> SimplCont -> ArgInfo
mkArgInfo SimplEnv
env InBndr
var (RuleEnv -> InBndr -> [CoreRule]
getRules RuleEnv
rule_base InBndr
var)
                              Int
n_val_args SimplCont
call_cont
       ; SimplEnv
-> ArgInfo -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
rebuildCall SimplEnv
env ArgInfo
info SimplCont
cont }

  where
    dflags :: DynFlags
dflags = SimplEnv -> DynFlags
seDynFlags SimplEnv
env
    (lone_variable :: Bool
lone_variable, arg_infos :: [ArgSummary]
arg_infos, call_cont :: SimplCont
call_cont) = SimplCont -> (Bool, [ArgSummary], SimplCont)
contArgs SimplCont
cont
    n_val_args :: Int
n_val_args       = [ArgSummary] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [ArgSummary]
arg_infos
    interesting_cont :: CallCtxt
interesting_cont = SimplEnv -> SimplCont -> CallCtxt
interestingCallContext SimplEnv
env SimplCont
call_cont
    active_unf :: Bool
active_unf       = SimplMode -> InBndr -> Bool
activeUnfolding (SimplEnv -> SimplMode
getMode SimplEnv
env) InBndr
var

    dump_inline :: a -> a -> m ()
dump_inline unfolding :: a
unfolding cont :: a
cont
      | Bool -> Bool
not (DumpFlag -> DynFlags -> Bool
dopt DumpFlag
Opt_D_dump_inlinings DynFlags
dflags) = () -> m ()
forall (m :: * -> *) a. Monad m => a -> m a
return ()
      | Bool -> Bool
not (DumpFlag -> DynFlags -> Bool
dopt DumpFlag
Opt_D_verbose_core2core DynFlags
dflags)
      = Bool -> m () -> m ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when (Name -> Bool
isExternalName (InBndr -> Name
idName InBndr
var)) (m () -> m ()) -> m () -> m ()
forall a b. (a -> b) -> a -> b
$
            IO () -> m ()
forall (m :: * -> *) a. MonadIO m => IO a -> m a
liftIO (IO () -> m ()) -> IO () -> m ()
forall a b. (a -> b) -> a -> b
$ DynFlags -> PrintUnqualified -> SDoc -> IO ()
printOutputForUser DynFlags
dflags PrintUnqualified
alwaysQualify (SDoc -> IO ()) -> SDoc -> IO ()
forall a b. (a -> b) -> a -> b
$
                [SDoc] -> SDoc
sep [[Char] -> SDoc
text "Inlining done:", Int -> SDoc -> SDoc
nest 4 (InBndr -> SDoc
forall a. Outputable a => a -> SDoc
ppr InBndr
var)]
      | Bool
otherwise
      = IO () -> m ()
forall (m :: * -> *) a. MonadIO m => IO a -> m a
liftIO (IO () -> m ()) -> IO () -> m ()
forall a b. (a -> b) -> a -> b
$ DynFlags -> PrintUnqualified -> SDoc -> IO ()
printOutputForUser DynFlags
dflags PrintUnqualified
alwaysQualify (SDoc -> IO ()) -> SDoc -> IO ()
forall a b. (a -> b) -> a -> b
$
           [SDoc] -> SDoc
sep [[Char] -> SDoc
text "Inlining done: " SDoc -> SDoc -> SDoc
<> InBndr -> SDoc
forall a. Outputable a => a -> SDoc
ppr InBndr
var,
                Int -> SDoc -> SDoc
nest 4 ([SDoc] -> SDoc
vcat [[Char] -> SDoc
text "Inlined fn: " SDoc -> SDoc -> SDoc
<+> Int -> SDoc -> SDoc
nest 2 (a -> SDoc
forall a. Outputable a => a -> SDoc
ppr a
unfolding),
                              [Char] -> SDoc
text "Cont:  " SDoc -> SDoc -> SDoc
<+> a -> SDoc
forall a. Outputable a => a -> SDoc
ppr a
cont])]

rebuildCall :: SimplEnv
            -> ArgInfo
            -> SimplCont
            -> SimplM (SimplFloats, OutExpr)
-- We decided not to inline, so
--    - simplify the arguments
--    - try rewrite rules
--    - and rebuild

---------- Bottoming applications --------------
rebuildCall :: SimplEnv
-> ArgInfo -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
rebuildCall env :: SimplEnv
env (ArgInfo { ai_fun :: ArgInfo -> InBndr
ai_fun = InBndr
fun, ai_args :: ArgInfo -> [ArgSpec]
ai_args = [ArgSpec]
rev_args, ai_strs :: ArgInfo -> [Bool]
ai_strs = [] }) cont :: SimplCont
cont
  -- When we run out of strictness args, it means
  -- that the call is definitely bottom; see SimplUtils.mkArgInfo
  -- Then we want to discard the entire strict continuation.  E.g.
  --    * case (error "hello") of { ... }
  --    * (error "Hello") arg
  --    * f (error "Hello") where f is strict
  --    etc
  -- Then, especially in the first of these cases, we'd like to discard
  -- the continuation, leaving just the bottoming expression.  But the
  -- type might not be right, so we may have to add a coerce.
  | Bool -> Bool
not (SimplCont -> Bool
contIsTrivial SimplCont
cont)     -- Only do this if there is a non-trivial
                                 -- continuation to discard, else we do it
                                 -- again and again!
  = OutType -> ()
seqType OutType
cont_ty ()
-> SimplM (SimplFloats, Expr InBndr)
-> SimplM (SimplFloats, Expr InBndr)
forall a b. a -> b -> b
`seq`        -- See Note [Avoiding space leaks in OutType]
    (SimplFloats, Expr InBndr) -> SimplM (SimplFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplEnv -> SimplFloats
emptyFloats SimplEnv
env, Expr InBndr -> OutType -> Expr InBndr
castBottomExpr Expr InBndr
res OutType
cont_ty)
  where
    res :: Expr InBndr
res     = InBndr -> [ArgSpec] -> Expr InBndr
argInfoExpr InBndr
fun [ArgSpec]
rev_args
    cont_ty :: OutType
cont_ty = SimplCont -> OutType
contResultType SimplCont
cont

---------- Try rewrite RULES --------------
-- See Note [Trying rewrite rules]
rebuildCall env :: SimplEnv
env info :: ArgInfo
info@(ArgInfo { ai_fun :: ArgInfo -> InBndr
ai_fun = InBndr
fun, ai_args :: ArgInfo -> [ArgSpec]
ai_args = [ArgSpec]
rev_args
                              , ai_rules :: ArgInfo -> FunRules
ai_rules = Just (nr_wanted :: Int
nr_wanted, rules :: [CoreRule]
rules) }) cont :: SimplCont
cont
  | Int
nr_wanted Int -> Int -> Bool
forall a. Eq a => a -> a -> Bool
== 0 Bool -> Bool -> Bool
|| Bool
no_more_args
  , let info' :: ArgInfo
info' = ArgInfo
info { ai_rules :: FunRules
ai_rules = FunRules
forall a. Maybe a
Nothing }
  = -- We've accumulated a simplified call in <fun,rev_args>
    -- so try rewrite rules; see Note [RULEs apply to simplified arguments]
    -- See also Note [Rules for recursive functions]
    do { Maybe (SimplEnv, Expr InBndr, SimplCont)
mb_match <- SimplEnv
-> [CoreRule]
-> InBndr
-> [ArgSpec]
-> SimplCont
-> SimplM (Maybe (SimplEnv, Expr InBndr, SimplCont))
tryRules SimplEnv
env [CoreRule]
rules InBndr
fun ([ArgSpec] -> [ArgSpec]
forall a. [a] -> [a]
reverse [ArgSpec]
rev_args) SimplCont
cont
       ; case Maybe (SimplEnv, Expr InBndr, SimplCont)
mb_match of
             Just (env' :: SimplEnv
env', rhs :: Expr InBndr
rhs, cont' :: SimplCont
cont') -> SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF SimplEnv
env' Expr InBndr
rhs SimplCont
cont'
             Nothing                 -> SimplEnv
-> ArgInfo -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
rebuildCall SimplEnv
env ArgInfo
info' SimplCont
cont }
  where
    no_more_args :: Bool
no_more_args = case SimplCont
cont of
                      ApplyToTy  {} -> Bool
False
                      ApplyToVal {} -> Bool
False
                      _             -> Bool
True


---------- Simplify applications and casts --------------
rebuildCall env :: SimplEnv
env info :: ArgInfo
info (CastIt co :: Coercion
co cont :: SimplCont
cont)
  = SimplEnv
-> ArgInfo -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
rebuildCall SimplEnv
env (ArgInfo -> Coercion -> ArgInfo
addCastTo ArgInfo
info Coercion
co) SimplCont
cont

rebuildCall env :: SimplEnv
env info :: ArgInfo
info (ApplyToTy { sc_arg_ty :: SimplCont -> OutType
sc_arg_ty = OutType
arg_ty, sc_cont :: SimplCont -> SimplCont
sc_cont = SimplCont
cont })
  = SimplEnv
-> ArgInfo -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
rebuildCall SimplEnv
env (ArgInfo -> OutType -> ArgInfo
addTyArgTo ArgInfo
info OutType
arg_ty) SimplCont
cont

rebuildCall env :: SimplEnv
env info :: ArgInfo
info@(ArgInfo { ai_encl :: ArgInfo -> Bool
ai_encl = Bool
encl_rules, ai_type :: ArgInfo -> OutType
ai_type = OutType
fun_ty
                              , ai_strs :: ArgInfo -> [Bool]
ai_strs = str :: Bool
str:strs :: [Bool]
strs, ai_discs :: ArgInfo -> [Int]
ai_discs = disc :: Int
disc:discs :: [Int]
discs })
            (ApplyToVal { sc_arg :: SimplCont -> Expr InBndr
sc_arg = Expr InBndr
arg, sc_env :: SimplCont -> SimplEnv
sc_env = SimplEnv
arg_se
                        , sc_dup :: SimplCont -> DupFlag
sc_dup = DupFlag
dup_flag, sc_cont :: SimplCont -> SimplCont
sc_cont = SimplCont
cont })
  | DupFlag -> Bool
isSimplified DupFlag
dup_flag     -- See Note [Avoid redundant simplification]
  = SimplEnv
-> ArgInfo -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
rebuildCall SimplEnv
env (ArgInfo -> Expr InBndr -> ArgInfo
addValArgTo ArgInfo
info' Expr InBndr
arg) SimplCont
cont

  | Bool
str         -- Strict argument
  , SimplMode -> Bool
sm_case_case (SimplEnv -> SimplMode
getMode SimplEnv
env)
  = -- pprTrace "Strict Arg" (ppr arg $$ ppr (seIdSubst env) $$ ppr (seInScope env)) $
    SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF (SimplEnv
arg_se SimplEnv -> SimplEnv -> SimplEnv
`setInScopeFromE` SimplEnv
env) Expr InBndr
arg
               (StrictArg :: DupFlag -> ArgInfo -> CallCtxt -> SimplCont -> SimplCont
StrictArg { sc_fun :: ArgInfo
sc_fun = ArgInfo
info', sc_cci :: CallCtxt
sc_cci = CallCtxt
cci_strict
                          , sc_dup :: DupFlag
sc_dup = DupFlag
Simplified, sc_cont :: SimplCont
sc_cont = SimplCont
cont })
                -- Note [Shadowing]

  | Bool
otherwise                           -- Lazy argument
        -- DO NOT float anything outside, hence simplExprC
        -- There is no benefit (unlike in a let-binding), and we'd
        -- have to be very careful about bogus strictness through
        -- floating a demanded let.
  = do  { Expr InBndr
arg' <- SimplEnv -> Expr InBndr -> SimplCont -> SimplM (Expr InBndr)
simplExprC (SimplEnv
arg_se SimplEnv -> SimplEnv -> SimplEnv
`setInScopeFromE` SimplEnv
env) Expr InBndr
arg
                             (OutType -> CallCtxt -> SimplCont
mkLazyArgStop OutType
arg_ty CallCtxt
cci_lazy)
        ; SimplEnv
-> ArgInfo -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
rebuildCall SimplEnv
env (ArgInfo -> Expr InBndr -> ArgInfo
addValArgTo ArgInfo
info' Expr InBndr
arg') SimplCont
cont }
  where
    info' :: ArgInfo
info'  = ArgInfo
info { ai_strs :: [Bool]
ai_strs = [Bool]
strs, ai_discs :: [Int]
ai_discs = [Int]
discs }
    arg_ty :: OutType
arg_ty = OutType -> OutType
funArgTy OutType
fun_ty

    -- Use this for lazy arguments
    cci_lazy :: CallCtxt
cci_lazy | Bool
encl_rules = CallCtxt
RuleArgCtxt
             | Int
disc Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
> 0   = CallCtxt
DiscArgCtxt  -- Be keener here
             | Bool
otherwise  = CallCtxt
BoringCtxt   -- Nothing interesting

    -- ..and this for strict arguments
    cci_strict :: CallCtxt
cci_strict | Bool
encl_rules = CallCtxt
RuleArgCtxt
               | Int
disc Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
> 0   = CallCtxt
DiscArgCtxt
               | Bool
otherwise  = CallCtxt
RhsCtxt
      -- Why RhsCtxt?  if we see f (g x) (h x), and f is strict, we
      -- want to be a bit more eager to inline g, because it may
      -- expose an eval (on x perhaps) that can be eliminated or
      -- shared. I saw this in nofib 'boyer2', RewriteFuns.onewayunify1
      -- It's worth an 18% improvement in allocation for this
      -- particular benchmark; 5% on 'mate' and 1.3% on 'multiplier'

---------- No further useful info, revert to generic rebuild ------------
rebuildCall env :: SimplEnv
env (ArgInfo { ai_fun :: ArgInfo -> InBndr
ai_fun = InBndr
fun, ai_args :: ArgInfo -> [ArgSpec]
ai_args = [ArgSpec]
rev_args }) cont :: SimplCont
cont
  = SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
rebuild SimplEnv
env (InBndr -> [ArgSpec] -> Expr InBndr
argInfoExpr InBndr
fun [ArgSpec]
rev_args) SimplCont
cont

{- Note [Trying rewrite rules]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider an application (f e1 e2 e3) where the e1,e2,e3 are not yet
simplified.  We want to simplify enough arguments to allow the rules
to apply, but it's more efficient to avoid simplifying e2,e3 if e1 alone
is sufficient.  Example: class ops
   (+) dNumInt e2 e3
If we rewrite ((+) dNumInt) to plusInt, we can take advantage of the
latter's strictness when simplifying e2, e3.  Moreover, suppose we have
  RULE  f Int = \x. x True

Then given (f Int e1) we rewrite to
   (\x. x True) e1
without simplifying e1.  Now we can inline x into its unique call site,
and absorb the True into it all in the same pass.  If we simplified
e1 first, we couldn't do that; see Note [Avoiding exponential behaviour].

So we try to apply rules if either
  (a) no_more_args: we've run out of argument that the rules can "see"
  (b) nr_wanted: none of the rules wants any more arguments


Note [RULES apply to simplified arguments]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
It's very desirable to try RULES once the arguments have been simplified, because
doing so ensures that rule cascades work in one pass.  Consider
   {-# RULES g (h x) = k x
             f (k x) = x #-}
   ...f (g (h x))...
Then we want to rewrite (g (h x)) to (k x) and only then try f's rules. If
we match f's rules against the un-simplified RHS, it won't match.  This
makes a particularly big difference when superclass selectors are involved:
        op ($p1 ($p2 (df d)))
We want all this to unravel in one sweep.

Note [Avoid redundant simplification]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Because RULES apply to simplified arguments, there's a danger of repeatedly
simplifying already-simplified arguments.  An important example is that of
        (>>=) d e1 e2
Here e1, e2 are simplified before the rule is applied, but don't really
participate in the rule firing. So we mark them as Simplified to avoid
re-simplifying them.

Note [Shadowing]
~~~~~~~~~~~~~~~~
This part of the simplifier may break the no-shadowing invariant
Consider
        f (...(\a -> e)...) (case y of (a,b) -> e')
where f is strict in its second arg
If we simplify the innermost one first we get (...(\a -> e)...)
Simplifying the second arg makes us float the case out, so we end up with
        case y of (a,b) -> f (...(\a -> e)...) e'
So the output does not have the no-shadowing invariant.  However, there is
no danger of getting name-capture, because when the first arg was simplified
we used an in-scope set that at least mentioned all the variables free in its
static environment, and that is enough.

We can't just do innermost first, or we'd end up with a dual problem:
        case x of (a,b) -> f e (...(\a -> e')...)

I spent hours trying to recover the no-shadowing invariant, but I just could
not think of an elegant way to do it.  The simplifier is already knee-deep in
continuations.  We have to keep the right in-scope set around; AND we have
to get the effect that finding (error "foo") in a strict arg position will
discard the entire application and replace it with (error "foo").  Getting
all this at once is TOO HARD!


************************************************************************
*                                                                      *
                Rewrite rules
*                                                                      *
************************************************************************
-}

tryRules :: SimplEnv -> [CoreRule]
         -> Id -> [ArgSpec]
         -> SimplCont
         -> SimplM (Maybe (SimplEnv, CoreExpr, SimplCont))

tryRules :: SimplEnv
-> [CoreRule]
-> InBndr
-> [ArgSpec]
-> SimplCont
-> SimplM (Maybe (SimplEnv, Expr InBndr, SimplCont))
tryRules env :: SimplEnv
env rules :: [CoreRule]
rules fn :: InBndr
fn args :: [ArgSpec]
args call_cont :: SimplCont
call_cont
  | [CoreRule] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [CoreRule]
rules
  = Maybe (SimplEnv, Expr InBndr, SimplCont)
-> SimplM (Maybe (SimplEnv, Expr InBndr, SimplCont))
forall (m :: * -> *) a. Monad m => a -> m a
return Maybe (SimplEnv, Expr InBndr, SimplCont)
forall a. Maybe a
Nothing

{- Disabled until we fix #8326
  | fn `hasKey` tagToEnumKey   -- See Note [Optimising tagToEnum#]
  , [_type_arg, val_arg] <- args
  , Select dup bndr ((_,[],rhs1) : rest_alts) se cont <- call_cont
  , isDeadBinder bndr
  = do { let enum_to_tag :: CoreAlt -> CoreAlt
                -- Takes   K -> e  into   tagK# -> e
                -- where tagK# is the tag of constructor K
             enum_to_tag (DataAlt con, [], rhs)
               = ASSERT( isEnumerationTyCon (dataConTyCon con) )
                (LitAlt tag, [], rhs)
              where
                tag = mkLitInt dflags (toInteger (dataConTag con - fIRST_TAG))
             enum_to_tag alt = pprPanic "tryRules: tagToEnum" (ppr alt)

             new_alts = (DEFAULT, [], rhs1) : map enum_to_tag rest_alts
             new_bndr = setIdType bndr intPrimTy
                 -- The binder is dead, but should have the right type
      ; return (Just (val_arg, Select dup new_bndr new_alts se cont)) }
-}

  | Just (rule :: CoreRule
rule, rule_rhs :: Expr InBndr
rule_rhs) <- DynFlags
-> InScopeEnv
-> (Activation -> Bool)
-> InBndr
-> [Expr InBndr]
-> [CoreRule]
-> Maybe (CoreRule, Expr InBndr)
lookupRule DynFlags
dflags (SimplEnv -> InScopeEnv
getUnfoldingInRuleMatch SimplEnv
env)
                                        (SimplMode -> Activation -> Bool
activeRule (SimplEnv -> SimplMode
getMode SimplEnv
env)) InBndr
fn
                                        ([ArgSpec] -> [Expr InBndr]
argInfoAppArgs [ArgSpec]
args) [CoreRule]
rules
  -- Fire a rule for the function
  = do { Tick -> SimplM ()
checkedTick (FastString -> Tick
RuleFired (CoreRule -> FastString
ruleName CoreRule
rule))
       ; let cont' :: SimplCont
cont' = SimplEnv -> [ArgSpec] -> SimplCont -> SimplCont
pushSimplifiedArgs SimplEnv
zapped_env
                                        (Int -> [ArgSpec] -> [ArgSpec]
forall a. Int -> [a] -> [a]
drop (CoreRule -> Int
ruleArity CoreRule
rule) [ArgSpec]
args)
                                        SimplCont
call_cont
                     -- (ruleArity rule) says how
                     -- many args the rule consumed

             occ_anald_rhs :: Expr InBndr
occ_anald_rhs = Expr InBndr -> Expr InBndr
occurAnalyseExpr Expr InBndr
rule_rhs
                 -- See Note [Occurrence-analyse after rule firing]
       ; CoreRule -> Expr InBndr -> SimplM ()
forall (m :: * -> *) b.
(MonadIO m, OutputableBndr b) =>
CoreRule -> Expr b -> m ()
dump CoreRule
rule Expr InBndr
rule_rhs
       ; Maybe (SimplEnv, Expr InBndr, SimplCont)
-> SimplM (Maybe (SimplEnv, Expr InBndr, SimplCont))
forall (m :: * -> *) a. Monad m => a -> m a
return ((SimplEnv, Expr InBndr, SimplCont)
-> Maybe (SimplEnv, Expr InBndr, SimplCont)
forall a. a -> Maybe a
Just (SimplEnv
zapped_env, Expr InBndr
occ_anald_rhs, SimplCont
cont')) }
            -- The occ_anald_rhs and cont' are all Out things
            -- hence zapping the environment

  | Bool
otherwise  -- No rule fires
  = do { SimplM ()
nodump  -- This ensures that an empty file is written
       ; Maybe (SimplEnv, Expr InBndr, SimplCont)
-> SimplM (Maybe (SimplEnv, Expr InBndr, SimplCont))
forall (m :: * -> *) a. Monad m => a -> m a
return Maybe (SimplEnv, Expr InBndr, SimplCont)
forall a. Maybe a
Nothing }

  where
    dflags :: DynFlags
dflags     = SimplEnv -> DynFlags
seDynFlags SimplEnv
env
    zapped_env :: SimplEnv
zapped_env = SimplEnv -> SimplEnv
zapSubstEnv SimplEnv
env  -- See Note [zapSubstEnv]

    printRuleModule :: CoreRule -> SDoc
printRuleModule rule :: CoreRule
rule
      = SDoc -> SDoc
parens (SDoc -> (Module -> SDoc) -> Maybe Module -> SDoc
forall b a. b -> (a -> b) -> Maybe a -> b
maybe ([Char] -> SDoc
text "BUILTIN")
                      (ModuleName -> SDoc
pprModuleName (ModuleName -> SDoc) -> (Module -> ModuleName) -> Module -> SDoc
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Module -> ModuleName
moduleName)
                      (CoreRule -> Maybe Module
ruleModule CoreRule
rule))

    dump :: CoreRule -> Expr b -> m ()
dump rule :: CoreRule
rule rule_rhs :: Expr b
rule_rhs
      | DumpFlag -> DynFlags -> Bool
dopt DumpFlag
Opt_D_dump_rule_rewrites DynFlags
dflags
      = DynFlags -> DumpFlag -> [Char] -> SDoc -> m ()
forall (m :: * -> *).
MonadIO m =>
DynFlags -> DumpFlag -> [Char] -> SDoc -> m ()
log_rule DynFlags
dflags DumpFlag
Opt_D_dump_rule_rewrites "Rule fired" (SDoc -> m ()) -> SDoc -> m ()
forall a b. (a -> b) -> a -> b
$ [SDoc] -> SDoc
vcat
          [ [Char] -> SDoc
text "Rule:" SDoc -> SDoc -> SDoc
<+> FastString -> SDoc
ftext (CoreRule -> FastString
ruleName CoreRule
rule)
          , [Char] -> SDoc
text "Module:" SDoc -> SDoc -> SDoc
<+>  CoreRule -> SDoc
printRuleModule CoreRule
rule
          , [Char] -> SDoc
text "Before:" SDoc -> SDoc -> SDoc
<+> SDoc -> Int -> SDoc -> SDoc
hang (InBndr -> SDoc
forall a. Outputable a => a -> SDoc
ppr InBndr
fn) 2 ([SDoc] -> SDoc
sep ((ArgSpec -> SDoc) -> [ArgSpec] -> [SDoc]
forall a b. (a -> b) -> [a] -> [b]
map ArgSpec -> SDoc
forall a. Outputable a => a -> SDoc
ppr [ArgSpec]
args))
          , [Char] -> SDoc
text "After: " SDoc -> SDoc -> SDoc
<+> Expr b -> SDoc
forall b. OutputableBndr b => Expr b -> SDoc
pprCoreExpr Expr b
rule_rhs
          , [Char] -> SDoc
text "Cont:  " SDoc -> SDoc -> SDoc
<+> SimplCont -> SDoc
forall a. Outputable a => a -> SDoc
ppr SimplCont
call_cont ]

      | DumpFlag -> DynFlags -> Bool
dopt DumpFlag
Opt_D_dump_rule_firings DynFlags
dflags
      = DynFlags -> DumpFlag -> [Char] -> SDoc -> m ()
forall (m :: * -> *).
MonadIO m =>
DynFlags -> DumpFlag -> [Char] -> SDoc -> m ()
log_rule DynFlags
dflags DumpFlag
Opt_D_dump_rule_firings "Rule fired:" (SDoc -> m ()) -> SDoc -> m ()
forall a b. (a -> b) -> a -> b
$
          FastString -> SDoc
ftext (CoreRule -> FastString
ruleName CoreRule
rule)
            SDoc -> SDoc -> SDoc
<+> CoreRule -> SDoc
printRuleModule CoreRule
rule

      | Bool
otherwise
      = () -> m ()
forall (m :: * -> *) a. Monad m => a -> m a
return ()

    nodump :: SimplM ()
nodump
      | DumpFlag -> DynFlags -> Bool
dopt DumpFlag
Opt_D_dump_rule_rewrites DynFlags
dflags
      = IO () -> SimplM ()
forall (m :: * -> *) a. MonadIO m => IO a -> m a
liftIO (IO () -> SimplM ()) -> IO () -> SimplM ()
forall a b. (a -> b) -> a -> b
$ DynFlags -> PrintUnqualified -> DumpFlag -> [Char] -> SDoc -> IO ()
dumpSDoc DynFlags
dflags PrintUnqualified
alwaysQualify DumpFlag
Opt_D_dump_rule_rewrites "" SDoc
empty

      | DumpFlag -> DynFlags -> Bool
dopt DumpFlag
Opt_D_dump_rule_firings DynFlags
dflags
      = IO () -> SimplM ()
forall (m :: * -> *) a. MonadIO m => IO a -> m a
liftIO (IO () -> SimplM ()) -> IO () -> SimplM ()
forall a b. (a -> b) -> a -> b
$ DynFlags -> PrintUnqualified -> DumpFlag -> [Char] -> SDoc -> IO ()
dumpSDoc DynFlags
dflags PrintUnqualified
alwaysQualify DumpFlag
Opt_D_dump_rule_firings "" SDoc
empty

      | Bool
otherwise
      = () -> SimplM ()
forall (m :: * -> *) a. Monad m => a -> m a
return ()

    log_rule :: DynFlags -> DumpFlag -> [Char] -> SDoc -> m ()
log_rule dflags :: DynFlags
dflags flag :: DumpFlag
flag hdr :: [Char]
hdr details :: SDoc
details
      = IO () -> m ()
forall (m :: * -> *) a. MonadIO m => IO a -> m a
liftIO (IO () -> m ()) -> (SDoc -> IO ()) -> SDoc -> m ()
forall b c a. (b -> c) -> (a -> b) -> a -> c
. DynFlags -> PrintUnqualified -> DumpFlag -> [Char] -> SDoc -> IO ()
dumpSDoc DynFlags
dflags PrintUnqualified
alwaysQualify DumpFlag
flag "" (SDoc -> m ()) -> SDoc -> m ()
forall a b. (a -> b) -> a -> b
$
                   [SDoc] -> SDoc
sep [[Char] -> SDoc
text [Char]
hdr, Int -> SDoc -> SDoc
nest 4 SDoc
details]

trySeqRules :: SimplEnv
            -> OutExpr -> InExpr   -- Scrutinee and RHS
            -> SimplCont
            -> SimplM (Maybe (SimplEnv, CoreExpr, SimplCont))
-- See Note [User-defined RULES for seq]
trySeqRules :: SimplEnv
-> Expr InBndr
-> Expr InBndr
-> SimplCont
-> SimplM (Maybe (SimplEnv, Expr InBndr, SimplCont))
trySeqRules in_env :: SimplEnv
in_env scrut :: Expr InBndr
scrut rhs :: Expr InBndr
rhs cont :: SimplCont
cont
  = do { RuleEnv
rule_base <- SimplM RuleEnv
getSimplRules
       ; SimplEnv
-> [CoreRule]
-> InBndr
-> [ArgSpec]
-> SimplCont
-> SimplM (Maybe (SimplEnv, Expr InBndr, SimplCont))
tryRules SimplEnv
in_env (RuleEnv -> InBndr -> [CoreRule]
getRules RuleEnv
rule_base InBndr
seqId) InBndr
seqId [ArgSpec]
out_args SimplCont
rule_cont }
  where
    no_cast_scrut :: Expr InBndr
no_cast_scrut = Expr InBndr -> Expr InBndr
forall b. Expr b -> Expr b
drop_casts Expr InBndr
scrut
    scrut_ty :: OutType
scrut_ty  = Expr InBndr -> OutType
exprType Expr InBndr
no_cast_scrut
    seq_id_ty :: OutType
seq_id_ty = InBndr -> OutType
idType InBndr
seqId
    rhs_ty :: OutType
rhs_ty    = SimplEnv -> OutType -> OutType
substTy SimplEnv
in_env (Expr InBndr -> OutType
exprType Expr InBndr
rhs)
    out_args :: [ArgSpec]
out_args  = [ TyArg :: OutType -> OutType -> ArgSpec
TyArg { as_arg_ty :: OutType
as_arg_ty  = OutType
scrut_ty
                        , as_hole_ty :: OutType
as_hole_ty = OutType
seq_id_ty }
                , TyArg :: OutType -> OutType -> ArgSpec
TyArg { as_arg_ty :: OutType
as_arg_ty  = OutType
rhs_ty
                       , as_hole_ty :: OutType
as_hole_ty  = HasDebugCallStack => OutType -> OutType -> OutType
OutType -> OutType -> OutType
piResultTy OutType
seq_id_ty OutType
scrut_ty }
                , Expr InBndr -> ArgSpec
ValArg Expr InBndr
no_cast_scrut]
    rule_cont :: SimplCont
rule_cont = ApplyToVal :: DupFlag -> Expr InBndr -> SimplEnv -> SimplCont -> SimplCont
ApplyToVal { sc_dup :: DupFlag
sc_dup = DupFlag
NoDup, sc_arg :: Expr InBndr
sc_arg = Expr InBndr
rhs
                           , sc_env :: SimplEnv
sc_env = SimplEnv
in_env, sc_cont :: SimplCont
sc_cont = SimplCont
cont }
    -- Lazily evaluated, so we don't do most of this

    drop_casts :: Expr b -> Expr b
drop_casts (Cast e :: Expr b
e _) = Expr b -> Expr b
drop_casts Expr b
e
    drop_casts e :: Expr b
e          = Expr b
e

{- Note [User-defined RULES for seq]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Given
   case (scrut |> co) of _ -> rhs
look for rules that match the expression
   seq @t1 @t2 scrut
where scrut :: t1
      rhs   :: t2

If you find a match, rewrite it, and apply to 'rhs'.

Notice that we can simply drop casts on the fly here, which
makes it more likely that a rule will match.

See Note [User-defined RULES for seq] in MkId.

Note [Occurrence-analyse after rule firing]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
After firing a rule, we occurrence-analyse the instantiated RHS before
simplifying it.  Usually this doesn't make much difference, but it can
be huge.  Here's an example (simplCore/should_compile/T7785)

  map f (map f (map f xs)

= -- Use build/fold form of map, twice
  map f (build (\cn. foldr (mapFB c f) n
                           (build (\cn. foldr (mapFB c f) n xs))))

= -- Apply fold/build rule
  map f (build (\cn. (\cn. foldr (mapFB c f) n xs) (mapFB c f) n))

= -- Beta-reduce
  -- Alas we have no occurrence-analysed, so we don't know
  -- that c is used exactly once
  map f (build (\cn. let c1 = mapFB c f in
                     foldr (mapFB c1 f) n xs))

= -- Use mapFB rule:   mapFB (mapFB c f) g = mapFB c (f.g)
  -- We can do this because (mapFB c n) is a PAP and hence expandable
  map f (build (\cn. let c1 = mapFB c n in
                     foldr (mapFB c (f.f)) n x))

This is not too bad.  But now do the same with the outer map, and
we get another use of mapFB, and t can interact with /both/ remaining
mapFB calls in the above expression.  This is stupid because actually
that 'c1' binding is dead.  The outer map introduces another c2. If
there is a deep stack of maps we get lots of dead bindings, and lots
of redundant work as we repeatedly simplify the result of firing rules.

The easy thing to do is simply to occurrence analyse the result of
the rule firing.  Note that this occ-anals not only the RHS of the
rule, but also the function arguments, which by now are OutExprs.
E.g.
      RULE f (g x) = x+1

Call   f (g BIG)  -->   (\x. x+1) BIG

The rule binders are lambda-bound and applied to the OutExpr arguments
(here BIG) which lack all internal occurrence info.

Is this inefficient?  Not really: we are about to walk over the result
of the rule firing to simplify it, so occurrence analysis is at most
a constant factor.

Possible improvement: occ-anal the rules when putting them in the
database; and in the simplifier just occ-anal the OutExpr arguments.
But that's more complicated and the rule RHS is usually tiny; so I'm
just doing the simple thing.

Historical note: previously we did occ-anal the rules in Rule.hs,
but failed to occ-anal the OutExpr arguments, which led to the
nasty performance problem described above.


Note [Optimising tagToEnum#]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If we have an enumeration data type:

  data Foo = A | B | C

Then we want to transform

   case tagToEnum# x of   ==>    case x of
     A -> e1                       DEFAULT -> e1
     B -> e2                       1#      -> e2
     C -> e3                       2#      -> e3

thereby getting rid of the tagToEnum# altogether.  If there was a DEFAULT
alternative we retain it (remember it comes first).  If not the case must
be exhaustive, and we reflect that in the transformed version by adding
a DEFAULT.  Otherwise Lint complains that the new case is not exhaustive.
See #8317.

Note [Rules for recursive functions]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
You might think that we shouldn't apply rules for a loop breaker:
doing so might give rise to an infinite loop, because a RULE is
rather like an extra equation for the function:
     RULE:           f (g x) y = x+y
     Eqn:            f a     y = a-y

But it's too drastic to disable rules for loop breakers.
Even the foldr/build rule would be disabled, because foldr
is recursive, and hence a loop breaker:
     foldr k z (build g) = g k z
So it's up to the programmer: rules can cause divergence


************************************************************************
*                                                                      *
                Rebuilding a case expression
*                                                                      *
************************************************************************

Note [Case elimination]
~~~~~~~~~~~~~~~~~~~~~~~
The case-elimination transformation discards redundant case expressions.
Start with a simple situation:

        case x# of      ===>   let y# = x# in e
          y# -> e

(when x#, y# are of primitive type, of course).  We can't (in general)
do this for algebraic cases, because we might turn bottom into
non-bottom!

The code in SimplUtils.prepareAlts has the effect of generalise this
idea to look for a case where we're scrutinising a variable, and we
know that only the default case can match.  For example:

        case x of
          0#      -> ...
          DEFAULT -> ...(case x of
                         0#      -> ...
                         DEFAULT -> ...) ...

Here the inner case is first trimmed to have only one alternative, the
DEFAULT, after which it's an instance of the previous case.  This
really only shows up in eliminating error-checking code.

Note that SimplUtils.mkCase combines identical RHSs.  So

        case e of       ===> case e of DEFAULT -> r
           True  -> r
           False -> r

Now again the case may be elminated by the CaseElim transformation.
This includes things like (==# a# b#)::Bool so that we simplify
      case ==# a# b# of { True -> x; False -> x }
to just
      x
This particular example shows up in default methods for
comparison operations (e.g. in (>=) for Int.Int32)

Note [Case to let transformation]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If a case over a lifted type has a single alternative, and is being
used as a strict 'let' (all isDeadBinder bndrs), we may want to do
this transformation:

    case e of r       ===>   let r = e in ...r...
      _ -> ...r...

We treat the unlifted and lifted cases separately:

* Unlifted case: 'e' satisfies exprOkForSpeculation
  (ok-for-spec is needed to satisfy the let/app invariant).
  This turns     case a +# b of r -> ...r...
  into           let r = a +# b in ...r...
  and thence     .....(a +# b)....

  However, if we have
      case indexArray# a i of r -> ...r...
  we might like to do the same, and inline the (indexArray# a i).
  But indexArray# is not okForSpeculation, so we don't build a let
  in rebuildCase (lest it get floated *out*), so the inlining doesn't
  happen either.  Annoying.

* Lifted case: we need to be sure that the expression is already
  evaluated (exprIsHNF).  If it's not already evaluated
      - we risk losing exceptions, divergence or
        user-specified thunk-forcing
      - even if 'e' is guaranteed to converge, we don't want to
        create a thunk (call by need) instead of evaluating it
        right away (call by value)

  However, we can turn the case into a /strict/ let if the 'r' is
  used strictly in the body.  Then we won't lose divergence; and
  we won't build a thunk because the let is strict.
  See also Note [Case-to-let for strictly-used binders]

  NB: absentError satisfies exprIsHNF: see Note [aBSENT_ERROR_ID] in MkCore.
  We want to turn
     case (absentError "foo") of r -> ...MkT r...
  into
     let r = absentError "foo" in ...MkT r...


Note [Case-to-let for strictly-used binders]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If we have this:
   case <scrut> of r { _ -> ..r.. }

where 'r' is used strictly in (..r..), we can safely transform to
   let r = <scrut> in ...r...

This is a Good Thing, because 'r' might be dead (if the body just
calls error), or might be used just once (in which case it can be
inlined); or we might be able to float the let-binding up or down.
E.g. Trac #15631 has an example.

Note that this can change the error behaviour.  For example, we might
transform
    case x of { _ -> error "bad" }
    --> error "bad"
which is might be puzzling if 'x' currently lambda-bound, but later gets
let-bound to (error "good").

Nevertheless, the paper "A semantics for imprecise exceptions" allows
this transformation. If you want to fix the evaluation order, use
'pseq'.  See Trac #8900 for an example where the loss of this
transformation bit us in practice.

See also Note [Empty case alternatives] in CoreSyn.

Historical notes

There have been various earlier versions of this patch:

* By Sept 18 the code looked like this:
     || scrut_is_demanded_var scrut

    scrut_is_demanded_var :: CoreExpr -> Bool
    scrut_is_demanded_var (Cast s _) = scrut_is_demanded_var s
    scrut_is_demanded_var (Var _)    = isStrictDmd (idDemandInfo case_bndr)
    scrut_is_demanded_var _          = False

  This only fired if the scrutinee was a /variable/, which seems
  an unnecessary restriction. So in Trac #15631 I relaxed it to allow
  arbitrary scrutinees.  Less code, less to explain -- but the change
  had 0.00% effect on nofib.

* Previously, in Jan 13 the code looked like this:
     || case_bndr_evald_next rhs

    case_bndr_evald_next :: CoreExpr -> Bool
      -- See Note [Case binder next]
    case_bndr_evald_next (Var v)         = v == case_bndr
    case_bndr_evald_next (Cast e _)      = case_bndr_evald_next e
    case_bndr_evald_next (App e _)       = case_bndr_evald_next e
    case_bndr_evald_next (Case e _ _ _)  = case_bndr_evald_next e
    case_bndr_evald_next _               = False

  This patch was part of fixing Trac #7542. See also
  Note [Eta reduction of an eval'd function] in CoreUtils.)


Further notes about case elimination
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider:       test :: Integer -> IO ()
                test = print

Turns out that this compiles to:
    Print.test
      = \ eta :: Integer
          eta1 :: Void# ->
          case PrelNum.< eta PrelNum.zeroInteger of wild { __DEFAULT ->
          case hPutStr stdout
                 (PrelNum.jtos eta ($w[] @ Char))
                 eta1
          of wild1 { (# new_s, a4 #) -> PrelIO.lvl23 new_s  }}

Notice the strange '<' which has no effect at all. This is a funny one.
It started like this:

f x y = if x < 0 then jtos x
          else if y==0 then "" else jtos x

At a particular call site we have (f v 1).  So we inline to get

        if v < 0 then jtos x
        else if 1==0 then "" else jtos x

Now simplify the 1==0 conditional:

        if v<0 then jtos v else jtos v

Now common-up the two branches of the case:

        case (v<0) of DEFAULT -> jtos v

Why don't we drop the case?  Because it's strict in v.  It's technically
wrong to drop even unnecessary evaluations, and in practice they
may be a result of 'seq' so we *definitely* don't want to drop those.
I don't really know how to improve this situation.
-}

---------------------------------------------------------
--      Eliminate the case if possible

rebuildCase, reallyRebuildCase
   :: SimplEnv
   -> OutExpr          -- Scrutinee
   -> InId             -- Case binder
   -> [InAlt]          -- Alternatives (inceasing order)
   -> SimplCont
   -> SimplM (SimplFloats, OutExpr)

--------------------------------------------------
--      1. Eliminate the case if there's a known constructor
--------------------------------------------------

rebuildCase :: SimplEnv
-> Expr InBndr
-> InBndr
-> [Alt InBndr]
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
rebuildCase env :: SimplEnv
env scrut :: Expr InBndr
scrut case_bndr :: InBndr
case_bndr alts :: [Alt InBndr]
alts cont :: SimplCont
cont
  | Lit lit :: Literal
lit <- Expr InBndr
scrut    -- No need for same treatment as constructors
                        -- because literals are inlined more vigorously
  , Bool -> Bool
not (Literal -> Bool
litIsLifted Literal
lit)
  = do  { Tick -> SimplM ()
tick (InBndr -> Tick
KnownBranch InBndr
case_bndr)
        ; case AltCon -> [Alt InBndr] -> Maybe (Alt InBndr)
forall a b. AltCon -> [(AltCon, a, b)] -> Maybe (AltCon, a, b)
findAlt (Literal -> AltCon
LitAlt Literal
lit) [Alt InBndr]
alts of
            Nothing           -> SimplEnv
-> InBndr
-> [Alt InBndr]
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
missingAlt SimplEnv
env InBndr
case_bndr [Alt InBndr]
alts SimplCont
cont
            Just (_, bs :: [InBndr]
bs, rhs :: Expr InBndr
rhs) -> [InBndr] -> Expr InBndr -> SimplM (SimplFloats, Expr InBndr)
forall (t :: * -> *) a.
Foldable t =>
t a -> Expr InBndr -> SimplM (SimplFloats, Expr InBndr)
simple_rhs [InBndr]
bs Expr InBndr
rhs }

  | Just (con :: DataCon
con, ty_args :: [OutType]
ty_args, other_args :: [Expr InBndr]
other_args) <- InScopeEnv
-> Expr InBndr -> Maybe (DataCon, [OutType], [Expr InBndr])
exprIsConApp_maybe (SimplEnv -> InScopeEnv
getUnfoldingInRuleMatch SimplEnv
env) Expr InBndr
scrut
        -- Works when the scrutinee is a variable with a known unfolding
        -- as well as when it's an explicit constructor application
  = do  { Tick -> SimplM ()
tick (InBndr -> Tick
KnownBranch InBndr
case_bndr)
        ; case AltCon -> [Alt InBndr] -> Maybe (Alt InBndr)
forall a b. AltCon -> [(AltCon, a, b)] -> Maybe (AltCon, a, b)
findAlt (DataCon -> AltCon
DataAlt DataCon
con) [Alt InBndr]
alts of
            Nothing  -> SimplEnv
-> InBndr
-> [Alt InBndr]
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
missingAlt SimplEnv
env InBndr
case_bndr [Alt InBndr]
alts SimplCont
cont
            Just (DEFAULT, bs :: [InBndr]
bs, rhs :: Expr InBndr
rhs) -> [InBndr] -> Expr InBndr -> SimplM (SimplFloats, Expr InBndr)
forall (t :: * -> *) a.
Foldable t =>
t a -> Expr InBndr -> SimplM (SimplFloats, Expr InBndr)
simple_rhs [InBndr]
bs Expr InBndr
rhs
            Just (_, bs :: [InBndr]
bs, rhs :: Expr InBndr
rhs)       -> SimplEnv
-> Expr InBndr
-> DataCon
-> [OutType]
-> [Expr InBndr]
-> InBndr
-> [InBndr]
-> Expr InBndr
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
knownCon SimplEnv
env Expr InBndr
scrut DataCon
con [OutType]
ty_args [Expr InBndr]
other_args
                                                InBndr
case_bndr [InBndr]
bs Expr InBndr
rhs SimplCont
cont
        }
  where
    simple_rhs :: t a -> Expr InBndr -> SimplM (SimplFloats, Expr InBndr)
simple_rhs bs :: t a
bs rhs :: Expr InBndr
rhs = ASSERT( null bs )
                        do { (floats1 :: SimplFloats
floats1, env' :: SimplEnv
env') <- SimplEnv -> InBndr -> Expr InBndr -> SimplM (SimplFloats, SimplEnv)
simplNonRecX SimplEnv
env InBndr
case_bndr Expr InBndr
scrut
                               -- scrut is a constructor application,
                               -- hence satisfies let/app invariant
                           ; (floats2 :: SimplFloats
floats2, expr' :: Expr InBndr
expr') <- SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF SimplEnv
env' Expr InBndr
rhs SimplCont
cont
                           ; (SimplFloats, Expr InBndr) -> SimplM (SimplFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats
floats1 SimplFloats -> SimplFloats -> SimplFloats
`addFloats` SimplFloats
floats2, Expr InBndr
expr') }


--------------------------------------------------
--      2. Eliminate the case if scrutinee is evaluated
--------------------------------------------------

rebuildCase env :: SimplEnv
env scrut :: Expr InBndr
scrut case_bndr :: InBndr
case_bndr alts :: [Alt InBndr]
alts@[(_, bndrs :: [InBndr]
bndrs, rhs :: Expr InBndr
rhs)] cont :: SimplCont
cont
  -- See if we can get rid of the case altogether
  -- See Note [Case elimination]
  -- mkCase made sure that if all the alternatives are equal,
  -- then there is now only one (DEFAULT) rhs

  -- 2a.  Dropping the case altogether, if
  --      a) it binds nothing (so it's really just a 'seq')
  --      b) evaluating the scrutinee has no side effects
  | Bool
is_plain_seq
  , Expr InBndr -> Bool
exprOkForSideEffects Expr InBndr
scrut
          -- The entire case is dead, so we can drop it
          -- if the scrutinee converges without having imperative
          -- side effects or raising a Haskell exception
          -- See Note [PrimOp can_fail and has_side_effects] in PrimOp
   = SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF SimplEnv
env Expr InBndr
rhs SimplCont
cont

  -- 2b.  Turn the case into a let, if
  --      a) it binds only the case-binder
  --      b) unlifted case: the scrutinee is ok-for-speculation
  --           lifted case: the scrutinee is in HNF (or will later be demanded)
  -- See Note [Case to let transformation]
  | Bool
all_dead_bndrs
  , Expr InBndr -> InBndr -> Bool
doCaseToLet Expr InBndr
scrut InBndr
case_bndr
  = do { Tick -> SimplM ()
tick (InBndr -> Tick
CaseElim InBndr
case_bndr)
       ; (floats1 :: SimplFloats
floats1, env' :: SimplEnv
env') <- SimplEnv -> InBndr -> Expr InBndr -> SimplM (SimplFloats, SimplEnv)
simplNonRecX SimplEnv
env InBndr
case_bndr Expr InBndr
scrut
       ; (floats2 :: SimplFloats
floats2, expr' :: Expr InBndr
expr') <- SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF SimplEnv
env' Expr InBndr
rhs SimplCont
cont
       ; (SimplFloats, Expr InBndr) -> SimplM (SimplFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats
floats1 SimplFloats -> SimplFloats -> SimplFloats
`addFloats` SimplFloats
floats2, Expr InBndr
expr') }

  -- 2c. Try the seq rules if
  --     a) it binds only the case binder
  --     b) a rule for seq applies
  -- See Note [User-defined RULES for seq] in MkId
  | Bool
is_plain_seq
  = do { Maybe (SimplEnv, Expr InBndr, SimplCont)
mb_rule <- SimplEnv
-> Expr InBndr
-> Expr InBndr
-> SimplCont
-> SimplM (Maybe (SimplEnv, Expr InBndr, SimplCont))
trySeqRules SimplEnv
env Expr InBndr
scrut Expr InBndr
rhs SimplCont
cont
       ; case Maybe (SimplEnv, Expr InBndr, SimplCont)
mb_rule of
           Just (env' :: SimplEnv
env', rule_rhs :: Expr InBndr
rule_rhs, cont' :: SimplCont
cont') -> SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF SimplEnv
env' Expr InBndr
rule_rhs SimplCont
cont'
           Nothing                      -> SimplEnv
-> Expr InBndr
-> InBndr
-> [Alt InBndr]
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
reallyRebuildCase SimplEnv
env Expr InBndr
scrut InBndr
case_bndr [Alt InBndr]
alts SimplCont
cont }
  where
    all_dead_bndrs :: Bool
all_dead_bndrs = (InBndr -> Bool) -> [InBndr] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
all InBndr -> Bool
isDeadBinder [InBndr]
bndrs       -- bndrs are [InId]
    is_plain_seq :: Bool
is_plain_seq   = Bool
all_dead_bndrs Bool -> Bool -> Bool
&& InBndr -> Bool
isDeadBinder InBndr
case_bndr -- Evaluation *only* for effect

rebuildCase env :: SimplEnv
env scrut :: Expr InBndr
scrut case_bndr :: InBndr
case_bndr alts :: [Alt InBndr]
alts cont :: SimplCont
cont
  = SimplEnv
-> Expr InBndr
-> InBndr
-> [Alt InBndr]
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
reallyRebuildCase SimplEnv
env Expr InBndr
scrut InBndr
case_bndr [Alt InBndr]
alts SimplCont
cont


doCaseToLet :: OutExpr          -- Scrutinee
            -> InId             -- Case binder
            -> Bool
-- The situation is         case scrut of b { DEFAULT -> body }
-- Can we transform thus?   let { b = scrut } in body
doCaseToLet :: Expr InBndr -> InBndr -> Bool
doCaseToLet scrut :: Expr InBndr
scrut case_bndr :: InBndr
case_bndr
  | InBndr -> Bool
isTyCoVar InBndr
case_bndr    -- Respect CoreSyn
  = Expr InBndr -> Bool
forall b. Expr b -> Bool
isTyCoArg Expr InBndr
scrut        -- Note [CoreSyn type and coercion invariant]

  | HasDebugCallStack => OutType -> Bool
OutType -> Bool
isUnliftedType (InBndr -> OutType
idType InBndr
case_bndr)
  = Expr InBndr -> Bool
exprOkForSpeculation Expr InBndr
scrut

  | Bool
otherwise  -- Scrut has a lifted type
  = Expr InBndr -> Bool
exprIsHNF Expr InBndr
scrut
    Bool -> Bool -> Bool
|| Demand -> Bool
forall s u. JointDmd (Str s) (Use u) -> Bool
isStrictDmd (InBndr -> Demand
idDemandInfo InBndr
case_bndr)
    -- See Note [Case-to-let for strictly-used binders]

--------------------------------------------------
--      3. Catch-all case
--------------------------------------------------

reallyRebuildCase :: SimplEnv
-> Expr InBndr
-> InBndr
-> [Alt InBndr]
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
reallyRebuildCase env :: SimplEnv
env scrut :: Expr InBndr
scrut case_bndr :: InBndr
case_bndr alts :: [Alt InBndr]
alts cont :: SimplCont
cont
  | Bool -> Bool
not (SimplMode -> Bool
sm_case_case (SimplEnv -> SimplMode
getMode SimplEnv
env))
  = do { Expr InBndr
case_expr <- SimplEnv
-> Expr InBndr
-> InBndr
-> [Alt InBndr]
-> SimplCont
-> SimplM (Expr InBndr)
simplAlts SimplEnv
env Expr InBndr
scrut InBndr
case_bndr [Alt InBndr]
alts
                                (OutType -> SimplCont
mkBoringStop (SimplCont -> OutType
contHoleType SimplCont
cont))
       ; SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
rebuild SimplEnv
env Expr InBndr
case_expr SimplCont
cont }

  | Bool
otherwise
  = do { (floats :: SimplFloats
floats, cont' :: SimplCont
cont') <- SimplEnv
-> [Alt InBndr] -> SimplCont -> SimplM (SimplFloats, SimplCont)
mkDupableCaseCont SimplEnv
env [Alt InBndr]
alts SimplCont
cont
       ; Expr InBndr
case_expr <- SimplEnv
-> Expr InBndr
-> InBndr
-> [Alt InBndr]
-> SimplCont
-> SimplM (Expr InBndr)
simplAlts (SimplEnv
env SimplEnv -> SimplFloats -> SimplEnv
`setInScopeFromF` SimplFloats
floats)
                                Expr InBndr
scrut InBndr
case_bndr [Alt InBndr]
alts SimplCont
cont'
       ; (SimplFloats, Expr InBndr) -> SimplM (SimplFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats
floats, Expr InBndr
case_expr) }

{-
simplCaseBinder checks whether the scrutinee is a variable, v.  If so,
try to eliminate uses of v in the RHSs in favour of case_bndr; that
way, there's a chance that v will now only be used once, and hence
inlined.

Historical note: we use to do the "case binder swap" in the Simplifier
so there were additional complications if the scrutinee was a variable.
Now the binder-swap stuff is done in the occurrence analyser; see
OccurAnal Note [Binder swap].

Note [knownCon occ info]
~~~~~~~~~~~~~~~~~~~~~~~~
If the case binder is not dead, then neither are the pattern bound
variables:
        case <any> of x { (a,b) ->
        case x of { (p,q) -> p } }
Here (a,b) both look dead, but come alive after the inner case is eliminated.
The point is that we bring into the envt a binding
        let x = (a,b)
after the outer case, and that makes (a,b) alive.  At least we do unless
the case binder is guaranteed dead.

Note [Case alternative occ info]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When we are simply reconstructing a case (the common case), we always
zap the occurrence info on the binders in the alternatives.  Even
if the case binder is dead, the scrutinee is usually a variable, and *that*
can bring the case-alternative binders back to life.
See Note [Add unfolding for scrutinee]

Note [Improving seq]
~~~~~~~~~~~~~~~~~~~
Consider
        type family F :: * -> *
        type instance F Int = Int

We'd like to transform
        case e of (x :: F Int) { DEFAULT -> rhs }
===>
        case e `cast` co of (x'::Int)
           I# x# -> let x = x' `cast` sym co
                    in rhs

so that 'rhs' can take advantage of the form of x'.  Notice that Note
[Case of cast] (in OccurAnal) may then apply to the result.

We'd also like to eliminate empty types (Trac #13468). So if

    data Void
    type instance F Bool = Void

then we'd like to transform
        case (x :: F Bool) of { _ -> error "urk" }
===>
        case (x |> co) of (x' :: Void) of {}

Nota Bene: we used to have a built-in rule for 'seq' that dropped
casts, so that
    case (x |> co) of { _ -> blah }
dropped the cast; in order to improve the chances of trySeqRules
firing.  But that works in the /opposite/ direction to Note [Improving
seq] so there's a danger of flip/flopping.  Better to make trySeqRules
insensitive to the cast, which is now is.

The need for [Improving seq] showed up in Roman's experiments.  Example:
  foo :: F Int -> Int -> Int
  foo t n = t `seq` bar n
     where
       bar 0 = 0
       bar n = bar (n - case t of TI i -> i)
Here we'd like to avoid repeated evaluating t inside the loop, by
taking advantage of the `seq`.

At one point I did transformation in LiberateCase, but it's more
robust here.  (Otherwise, there's a danger that we'll simply drop the
'seq' altogether, before LiberateCase gets to see it.)
-}

simplAlts :: SimplEnv
          -> OutExpr         -- Scrutinee
          -> InId            -- Case binder
          -> [InAlt]         -- Non-empty
          -> SimplCont
          -> SimplM OutExpr  -- Returns the complete simplified case expression

simplAlts :: SimplEnv
-> Expr InBndr
-> InBndr
-> [Alt InBndr]
-> SimplCont
-> SimplM (Expr InBndr)
simplAlts env0 :: SimplEnv
env0 scrut :: Expr InBndr
scrut case_bndr :: InBndr
case_bndr alts :: [Alt InBndr]
alts cont' :: SimplCont
cont'
  = do  { [Char] -> SDoc -> SimplM ()
traceSmpl "simplAlts" ([SDoc] -> SDoc
vcat [ InBndr -> SDoc
forall a. Outputable a => a -> SDoc
ppr InBndr
case_bndr
                                      , [Char] -> SDoc
text "cont':" SDoc -> SDoc -> SDoc
<+> SimplCont -> SDoc
forall a. Outputable a => a -> SDoc
ppr SimplCont
cont'
                                      , [Char] -> SDoc
text "in_scope" SDoc -> SDoc -> SDoc
<+> InScopeSet -> SDoc
forall a. Outputable a => a -> SDoc
ppr (SimplEnv -> InScopeSet
seInScope SimplEnv
env0) ])
        ; (env1 :: SimplEnv
env1, case_bndr1 :: InBndr
case_bndr1) <- SimplEnv -> InBndr -> SimplM (SimplEnv, InBndr)
simplBinder SimplEnv
env0 InBndr
case_bndr
        ; let case_bndr2 :: InBndr
case_bndr2 = InBndr
case_bndr1 InBndr -> Unfolding -> InBndr
`setIdUnfolding` Unfolding
evaldUnfolding
              env2 :: SimplEnv
env2       = SimplEnv -> InBndr -> SimplEnv
modifyInScope SimplEnv
env1 InBndr
case_bndr2
              -- See Note [Case binder evaluated-ness]

        ; (FamInstEnv, FamInstEnv)
fam_envs <- SimplM (FamInstEnv, FamInstEnv)
getFamEnvs
        ; (alt_env' :: SimplEnv
alt_env', scrut' :: Expr InBndr
scrut', case_bndr' :: InBndr
case_bndr') <- (FamInstEnv, FamInstEnv)
-> SimplEnv
-> Expr InBndr
-> InBndr
-> InBndr
-> [Alt InBndr]
-> SimplM (SimplEnv, Expr InBndr, InBndr)
improveSeq (FamInstEnv, FamInstEnv)
fam_envs SimplEnv
env2 Expr InBndr
scrut
                                                       InBndr
case_bndr InBndr
case_bndr2 [Alt InBndr]
alts

        ; (imposs_deflt_cons :: [AltCon]
imposs_deflt_cons, in_alts :: [Alt InBndr]
in_alts) <- Expr InBndr
-> InBndr -> [Alt InBndr] -> SimplM ([AltCon], [Alt InBndr])
prepareAlts Expr InBndr
scrut' InBndr
case_bndr' [Alt InBndr]
alts
          -- NB: it's possible that the returned in_alts is empty: this is handled
          -- by the caller (rebuildCase) in the missingAlt function

        ; [Alt InBndr]
alts' <- (Alt InBndr -> SimplM (Alt InBndr))
-> [Alt InBndr] -> SimplM [Alt InBndr]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (SimplEnv
-> Maybe (Expr InBndr)
-> [AltCon]
-> InBndr
-> SimplCont
-> Alt InBndr
-> SimplM (Alt InBndr)
simplAlt SimplEnv
alt_env' (Expr InBndr -> Maybe (Expr InBndr)
forall a. a -> Maybe a
Just Expr InBndr
scrut') [AltCon]
imposs_deflt_cons InBndr
case_bndr' SimplCont
cont') [Alt InBndr]
in_alts
        ; -- pprTrace "simplAlts" (ppr case_bndr $$ ppr alts_ty $$ ppr alts_ty' $$ ppr alts $$ ppr cont') $

        ; let alts_ty' :: OutType
alts_ty' = SimplCont -> OutType
contResultType SimplCont
cont'
        -- See Note [Avoiding space leaks in OutType]
        ; OutType -> ()
seqType OutType
alts_ty' () -> SimplM (Expr InBndr) -> SimplM (Expr InBndr)
forall a b. a -> b -> b
`seq`
          DynFlags
-> Expr InBndr
-> InBndr
-> OutType
-> [Alt InBndr]
-> SimplM (Expr InBndr)
mkCase (SimplEnv -> DynFlags
seDynFlags SimplEnv
env0) Expr InBndr
scrut' InBndr
case_bndr' OutType
alts_ty' [Alt InBndr]
alts' }


------------------------------------
improveSeq :: (FamInstEnv, FamInstEnv) -> SimplEnv
           -> OutExpr -> InId -> OutId -> [InAlt]
           -> SimplM (SimplEnv, OutExpr, OutId)
-- Note [Improving seq]
improveSeq :: (FamInstEnv, FamInstEnv)
-> SimplEnv
-> Expr InBndr
-> InBndr
-> InBndr
-> [Alt InBndr]
-> SimplM (SimplEnv, Expr InBndr, InBndr)
improveSeq fam_envs :: (FamInstEnv, FamInstEnv)
fam_envs env :: SimplEnv
env scrut :: Expr InBndr
scrut case_bndr :: InBndr
case_bndr case_bndr1 :: InBndr
case_bndr1 [(DEFAULT,_,_)]
  | Just (co :: Coercion
co, ty2 :: OutType
ty2) <- (FamInstEnv, FamInstEnv) -> OutType -> Maybe (Coercion, OutType)
topNormaliseType_maybe (FamInstEnv, FamInstEnv)
fam_envs (InBndr -> OutType
idType InBndr
case_bndr1)
  = do { InBndr
case_bndr2 <- FastString -> OutType -> SimplM InBndr
newId ([Char] -> FastString
fsLit "nt") OutType
ty2
        ; let rhs :: SimplSR
rhs  = Expr InBndr -> Maybe Int -> SimplSR
DoneEx (InBndr -> Expr InBndr
forall b. InBndr -> Expr b
Var InBndr
case_bndr2 Expr InBndr -> Coercion -> Expr InBndr
forall b. Expr b -> Coercion -> Expr b
`Cast` Coercion -> Coercion
mkSymCo Coercion
co) Maybe Int
forall a. Maybe a
Nothing
              env2 :: SimplEnv
env2 = SimplEnv -> InBndr -> SimplSR -> SimplEnv
extendIdSubst SimplEnv
env InBndr
case_bndr SimplSR
rhs
        ; (SimplEnv, Expr InBndr, InBndr)
-> SimplM (SimplEnv, Expr InBndr, InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplEnv
env2, Expr InBndr
scrut Expr InBndr -> Coercion -> Expr InBndr
forall b. Expr b -> Coercion -> Expr b
`Cast` Coercion
co, InBndr
case_bndr2) }

improveSeq _ env :: SimplEnv
env scrut :: Expr InBndr
scrut _ case_bndr1 :: InBndr
case_bndr1 _
  = (SimplEnv, Expr InBndr, InBndr)
-> SimplM (SimplEnv, Expr InBndr, InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplEnv
env, Expr InBndr
scrut, InBndr
case_bndr1)


------------------------------------
simplAlt :: SimplEnv
         -> Maybe OutExpr  -- The scrutinee
         -> [AltCon]       -- These constructors can't be present when
                           -- matching the DEFAULT alternative
         -> OutId          -- The case binder
         -> SimplCont
         -> InAlt
         -> SimplM OutAlt

simplAlt :: SimplEnv
-> Maybe (Expr InBndr)
-> [AltCon]
-> InBndr
-> SimplCont
-> Alt InBndr
-> SimplM (Alt InBndr)
simplAlt env :: SimplEnv
env _ imposs_deflt_cons :: [AltCon]
imposs_deflt_cons case_bndr' :: InBndr
case_bndr' cont' :: SimplCont
cont' (DEFAULT, bndrs :: [InBndr]
bndrs, rhs :: Expr InBndr
rhs)
  = ASSERT( null bndrs )
    do  { let env' :: SimplEnv
env' = SimplEnv -> InBndr -> Unfolding -> SimplEnv
addBinderUnfolding SimplEnv
env InBndr
case_bndr'
                                        ([AltCon] -> Unfolding
mkOtherCon [AltCon]
imposs_deflt_cons)
                -- Record the constructors that the case-binder *can't* be.
        ; Expr InBndr
rhs' <- SimplEnv -> Expr InBndr -> SimplCont -> SimplM (Expr InBndr)
simplExprC SimplEnv
env' Expr InBndr
rhs SimplCont
cont'
        ; Alt InBndr -> SimplM (Alt InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (AltCon
DEFAULT, [], Expr InBndr
rhs') }

simplAlt env :: SimplEnv
env scrut' :: Maybe (Expr InBndr)
scrut' _ case_bndr' :: InBndr
case_bndr' cont' :: SimplCont
cont' (LitAlt lit :: Literal
lit, bndrs :: [InBndr]
bndrs, rhs :: Expr InBndr
rhs)
  = ASSERT( null bndrs )
    do  { SimplEnv
env' <- SimplEnv
-> Maybe (Expr InBndr) -> InBndr -> Expr InBndr -> SimplM SimplEnv
addAltUnfoldings SimplEnv
env Maybe (Expr InBndr)
scrut' InBndr
case_bndr' (Literal -> Expr InBndr
forall b. Literal -> Expr b
Lit Literal
lit)
        ; Expr InBndr
rhs' <- SimplEnv -> Expr InBndr -> SimplCont -> SimplM (Expr InBndr)
simplExprC SimplEnv
env' Expr InBndr
rhs SimplCont
cont'
        ; Alt InBndr -> SimplM (Alt InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (Literal -> AltCon
LitAlt Literal
lit, [], Expr InBndr
rhs') }

simplAlt env :: SimplEnv
env scrut' :: Maybe (Expr InBndr)
scrut' _ case_bndr' :: InBndr
case_bndr' cont' :: SimplCont
cont' (DataAlt con :: DataCon
con, vs :: [InBndr]
vs, rhs :: Expr InBndr
rhs)
  = do  { -- See Note [Adding evaluatedness info to pattern-bound variables]
          let vs_with_evals :: [InBndr]
vs_with_evals = Maybe (Expr InBndr) -> DataCon -> [InBndr] -> [InBndr]
addEvals Maybe (Expr InBndr)
scrut' DataCon
con [InBndr]
vs
        ; (env' :: SimplEnv
env', vs' :: [InBndr]
vs') <- SimplEnv -> [InBndr] -> SimplM (SimplEnv, [InBndr])
simplLamBndrs SimplEnv
env [InBndr]
vs_with_evals

                -- Bind the case-binder to (con args)
        ; let inst_tys' :: [OutType]
inst_tys' = OutType -> [OutType]
tyConAppArgs (InBndr -> OutType
idType InBndr
case_bndr')
              con_app :: OutExpr
              con_app :: Expr InBndr
con_app   = DataCon -> [OutType] -> [InBndr] -> Expr InBndr
forall b. DataCon -> [OutType] -> [InBndr] -> Expr b
mkConApp2 DataCon
con [OutType]
inst_tys' [InBndr]
vs'

        ; SimplEnv
env'' <- SimplEnv
-> Maybe (Expr InBndr) -> InBndr -> Expr InBndr -> SimplM SimplEnv
addAltUnfoldings SimplEnv
env' Maybe (Expr InBndr)
scrut' InBndr
case_bndr' Expr InBndr
con_app
        ; Expr InBndr
rhs' <- SimplEnv -> Expr InBndr -> SimplCont -> SimplM (Expr InBndr)
simplExprC SimplEnv
env'' Expr InBndr
rhs SimplCont
cont'
        ; Alt InBndr -> SimplM (Alt InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (DataCon -> AltCon
DataAlt DataCon
con, [InBndr]
vs', Expr InBndr
rhs') }

{- Note [Adding evaluatedness info to pattern-bound variables]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
addEvals records the evaluated-ness of the bound variables of
a case pattern.  This is *important*.  Consider

     data T = T !Int !Int

     case x of { T a b -> T (a+1) b }

We really must record that b is already evaluated so that we don't
go and re-evaluate it when constructing the result.
See Note [Data-con worker strictness] in MkId.hs

NB: simplLamBinders preserves this eval info

In addition to handling data constructor fields with !s, addEvals
also records the fact that the result of seq# is always in WHNF.
See Note [seq# magic] in PrelRules.  Example (Trac #15226):

  case seq# v s of
    (# s', v' #) -> E

we want the compiler to be aware that v' is in WHNF in E.

Open problem: we don't record that v itself is in WHNF (and we can't
do it here).  The right thing is to do some kind of binder-swap;
see Trac #15226 for discussion.
-}

addEvals :: Maybe OutExpr -> DataCon -> [Id] -> [Id]
-- See Note [Adding evaluatedness info to pattern-bound variables]
addEvals :: Maybe (Expr InBndr) -> DataCon -> [InBndr] -> [InBndr]
addEvals scrut :: Maybe (Expr InBndr)
scrut con :: DataCon
con vs :: [InBndr]
vs
  -- Deal with seq# applications
  | Just scr :: Expr InBndr
scr <- Maybe (Expr InBndr)
scrut
  , DataCon -> Bool
isUnboxedTupleCon DataCon
con
  , [s :: InBndr
s,x :: InBndr
x] <- [InBndr]
vs
    -- Use stripNArgs rather than collectArgsTicks to avoid building
    -- a list of arguments only to throw it away immediately.
  , Just (Var f :: InBndr
f) <- Word -> Expr InBndr -> Maybe (Expr InBndr)
forall a. Word -> Expr a -> Maybe (Expr a)
stripNArgs 4 Expr InBndr
scr
  , Just SeqOp <- InBndr -> Maybe PrimOp
isPrimOpId_maybe InBndr
f
  , let x' :: InBndr
x' = StrictnessMark -> InBndr -> InBndr
zapIdOccInfoAndSetEvald StrictnessMark
MarkedStrict InBndr
x
  = [InBndr
s, InBndr
x']

  -- Deal with banged datacon fields
addEvals _scrut :: Maybe (Expr InBndr)
_scrut con :: DataCon
con vs :: [InBndr]
vs = [InBndr] -> [StrictnessMark] -> [InBndr]
go [InBndr]
vs [StrictnessMark]
the_strs
    where
      the_strs :: [StrictnessMark]
the_strs = DataCon -> [StrictnessMark]
dataConRepStrictness DataCon
con

      go :: [InBndr] -> [StrictnessMark] -> [InBndr]
go [] [] = []
      go (v :: InBndr
v:vs' :: [InBndr]
vs') strs :: [StrictnessMark]
strs | InBndr -> Bool
isTyVar InBndr
v = InBndr
v InBndr -> [InBndr] -> [InBndr]
forall a. a -> [a] -> [a]
: [InBndr] -> [StrictnessMark] -> [InBndr]
go [InBndr]
vs' [StrictnessMark]
strs
      go (v :: InBndr
v:vs' :: [InBndr]
vs') (str :: StrictnessMark
str:strs :: [StrictnessMark]
strs) = StrictnessMark -> InBndr -> InBndr
zapIdOccInfoAndSetEvald StrictnessMark
str InBndr
v InBndr -> [InBndr] -> [InBndr]
forall a. a -> [a] -> [a]
: [InBndr] -> [StrictnessMark] -> [InBndr]
go [InBndr]
vs' [StrictnessMark]
strs
      go _ _ = [Char] -> SDoc -> [InBndr]
forall a. HasCallStack => [Char] -> SDoc -> a
pprPanic "Simplify.addEvals"
                (DataCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr DataCon
con SDoc -> SDoc -> SDoc
$$
                 [InBndr] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [InBndr]
vs  SDoc -> SDoc -> SDoc
$$
                 [[Char]] -> SDoc
forall (t :: * -> *) a.
(Outputable (t a), Foldable t) =>
t a -> SDoc
ppr_with_length ((StrictnessMark -> [Char]) -> [StrictnessMark] -> [[Char]]
forall a b. (a -> b) -> [a] -> [b]
map StrictnessMark -> [Char]
strdisp [StrictnessMark]
the_strs) SDoc -> SDoc -> SDoc
$$
                 [OutType] -> SDoc
forall (t :: * -> *) a.
(Outputable (t a), Foldable t) =>
t a -> SDoc
ppr_with_length (DataCon -> [OutType]
dataConRepArgTys DataCon
con) SDoc -> SDoc -> SDoc
$$
                 [StrictnessMark] -> SDoc
forall (t :: * -> *) a.
(Outputable (t a), Foldable t) =>
t a -> SDoc
ppr_with_length (DataCon -> [StrictnessMark]
dataConRepStrictness DataCon
con))
        where
          ppr_with_length :: t a -> SDoc
ppr_with_length list :: t a
list
            = t a -> SDoc
forall a. Outputable a => a -> SDoc
ppr t a
list SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
parens ([Char] -> SDoc
text "length =" SDoc -> SDoc -> SDoc
<+> Int -> SDoc
forall a. Outputable a => a -> SDoc
ppr (t a -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length t a
list))
          strdisp :: StrictnessMark -> [Char]
strdisp MarkedStrict = "MarkedStrict"
          strdisp NotMarkedStrict = "NotMarkedStrict"

zapIdOccInfoAndSetEvald :: StrictnessMark -> Id -> Id
zapIdOccInfoAndSetEvald :: StrictnessMark -> InBndr -> InBndr
zapIdOccInfoAndSetEvald str :: StrictnessMark
str v :: InBndr
v =
  StrictnessMark -> InBndr -> InBndr
setCaseBndrEvald StrictnessMark
str (InBndr -> InBndr) -> InBndr -> InBndr
forall a b. (a -> b) -> a -> b
$ -- Add eval'dness info
  InBndr -> InBndr
zapIdOccInfo InBndr
v         -- And kill occ info;
                         -- see Note [Case alternative occ info]

addAltUnfoldings :: SimplEnv -> Maybe OutExpr -> OutId -> OutExpr -> SimplM SimplEnv
addAltUnfoldings :: SimplEnv
-> Maybe (Expr InBndr) -> InBndr -> Expr InBndr -> SimplM SimplEnv
addAltUnfoldings env :: SimplEnv
env scrut :: Maybe (Expr InBndr)
scrut case_bndr :: InBndr
case_bndr con_app :: Expr InBndr
con_app
  = do { let con_app_unf :: Unfolding
con_app_unf = Expr InBndr -> Unfolding
mk_simple_unf Expr InBndr
con_app
             env1 :: SimplEnv
env1 = SimplEnv -> InBndr -> Unfolding -> SimplEnv
addBinderUnfolding SimplEnv
env InBndr
case_bndr Unfolding
con_app_unf

             -- See Note [Add unfolding for scrutinee]
             env2 :: SimplEnv
env2 = case Maybe (Expr InBndr)
scrut of
                      Just (Var v :: InBndr
v)           -> SimplEnv -> InBndr -> Unfolding -> SimplEnv
addBinderUnfolding SimplEnv
env1 InBndr
v Unfolding
con_app_unf
                      Just (Cast (Var v :: InBndr
v) co :: Coercion
co) -> SimplEnv -> InBndr -> Unfolding -> SimplEnv
addBinderUnfolding SimplEnv
env1 InBndr
v (Unfolding -> SimplEnv) -> Unfolding -> SimplEnv
forall a b. (a -> b) -> a -> b
$
                                                Expr InBndr -> Unfolding
mk_simple_unf (Expr InBndr -> Coercion -> Expr InBndr
forall b. Expr b -> Coercion -> Expr b
Cast Expr InBndr
con_app (Coercion -> Coercion
mkSymCo Coercion
co))
                      _                      -> SimplEnv
env1

       ; [Char] -> SDoc -> SimplM ()
traceSmpl "addAltUnf" ([SDoc] -> SDoc
vcat [InBndr -> SDoc
forall a. Outputable a => a -> SDoc
ppr InBndr
case_bndr SDoc -> SDoc -> SDoc
<+> Maybe (Expr InBndr) -> SDoc
forall a. Outputable a => a -> SDoc
ppr Maybe (Expr InBndr)
scrut, Expr InBndr -> SDoc
forall a. Outputable a => a -> SDoc
ppr Expr InBndr
con_app])
       ; SimplEnv -> SimplM SimplEnv
forall (m :: * -> *) a. Monad m => a -> m a
return SimplEnv
env2 }
  where
    mk_simple_unf :: Expr InBndr -> Unfolding
mk_simple_unf = DynFlags -> Expr InBndr -> Unfolding
mkSimpleUnfolding (SimplEnv -> DynFlags
seDynFlags SimplEnv
env)

addBinderUnfolding :: SimplEnv -> Id -> Unfolding -> SimplEnv
addBinderUnfolding :: SimplEnv -> InBndr -> Unfolding -> SimplEnv
addBinderUnfolding env :: SimplEnv
env bndr :: InBndr
bndr unf :: Unfolding
unf
  | Bool
debugIsOn, Just tmpl :: Expr InBndr
tmpl <- Unfolding -> Maybe (Expr InBndr)
maybeUnfoldingTemplate Unfolding
unf
  = WARN( not (eqType (idType bndr) (exprType tmpl)),
          ppr bndr $$ ppr (idType bndr) $$ ppr tmpl $$ ppr (exprType tmpl) )
    SimplEnv -> InBndr -> SimplEnv
modifyInScope SimplEnv
env (InBndr
bndr InBndr -> Unfolding -> InBndr
`setIdUnfolding` Unfolding
unf)

  | Bool
otherwise
  = SimplEnv -> InBndr -> SimplEnv
modifyInScope SimplEnv
env (InBndr
bndr InBndr -> Unfolding -> InBndr
`setIdUnfolding` Unfolding
unf)

zapBndrOccInfo :: Bool -> Id -> Id
-- Consider  case e of b { (a,b) -> ... }
-- Then if we bind b to (a,b) in "...", and b is not dead,
-- then we must zap the deadness info on a,b
zapBndrOccInfo :: Bool -> InBndr -> InBndr
zapBndrOccInfo keep_occ_info :: Bool
keep_occ_info pat_id :: InBndr
pat_id
  | Bool
keep_occ_info = InBndr
pat_id
  | Bool
otherwise     = InBndr -> InBndr
zapIdOccInfo InBndr
pat_id

{- Note [Case binder evaluated-ness]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We pin on a (OtherCon []) unfolding to the case-binder of a Case,
even though it'll be over-ridden in every case alternative with a more
informative unfolding.  Why?  Because suppose a later, less clever, pass
simply replaces all occurrences of the case binder with the binder itself;
then Lint may complain about the let/app invariant.  Example
    case e of b { DEFAULT -> let v = reallyUnsafePtrEq# b y in ....
                ; K       -> blah }

The let/app invariant requires that y is evaluated in the call to
reallyUnsafePtrEq#, which it is.  But we still want that to be true if we
propagate binders to occurrences.

This showed up in Trac #13027.

Note [Add unfolding for scrutinee]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In general it's unlikely that a variable scrutinee will appear
in the case alternatives   case x of { ...x unlikely to appear... }
because the binder-swap in OccAnal has got rid of all such occurrences
See Note [Binder swap] in OccAnal.

BUT it is still VERY IMPORTANT to add a suitable unfolding for a
variable scrutinee, in simplAlt.  Here's why
   case x of y
     (a,b) -> case b of c
                I# v -> ...(f y)...
There is no occurrence of 'b' in the (...(f y)...).  But y gets
the unfolding (a,b), and *that* mentions b.  If f has a RULE
    RULE f (p, I# q) = ...
we want that rule to match, so we must extend the in-scope env with a
suitable unfolding for 'y'.  It's *essential* for rule matching; but
it's also good for case-elimintation -- suppose that 'f' was inlined
and did multi-level case analysis, then we'd solve it in one
simplifier sweep instead of two.

Exactly the same issue arises in SpecConstr;
see Note [Add scrutinee to ValueEnv too] in SpecConstr

HOWEVER, given
  case x of y { Just a -> r1; Nothing -> r2 }
we do not want to add the unfolding x -> y to 'x', which might seem cool,
since 'y' itself has different unfoldings in r1 and r2.  Reason: if we
did that, we'd have to zap y's deadness info and that is a very useful
piece of information.

So instead we add the unfolding x -> Just a, and x -> Nothing in the
respective RHSs.


************************************************************************
*                                                                      *
\subsection{Known constructor}
*                                                                      *
************************************************************************

We are a bit careful with occurrence info.  Here's an example

        (\x* -> case x of (a*, b) -> f a) (h v, e)

where the * means "occurs once".  This effectively becomes
        case (h v, e) of (a*, b) -> f a)
and then
        let a* = h v; b = e in f a
and then
        f (h v)

All this should happen in one sweep.
-}

knownCon :: SimplEnv
         -> OutExpr                             -- The scrutinee
         -> DataCon -> [OutType] -> [OutExpr]   -- The scrutinee (in pieces)
         -> InId -> [InBndr] -> InExpr          -- The alternative
         -> SimplCont
         -> SimplM (SimplFloats, OutExpr)

knownCon :: SimplEnv
-> Expr InBndr
-> DataCon
-> [OutType]
-> [Expr InBndr]
-> InBndr
-> [InBndr]
-> Expr InBndr
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
knownCon env :: SimplEnv
env scrut :: Expr InBndr
scrut dc :: DataCon
dc dc_ty_args :: [OutType]
dc_ty_args dc_args :: [Expr InBndr]
dc_args bndr :: InBndr
bndr bs :: [InBndr]
bs rhs :: Expr InBndr
rhs cont :: SimplCont
cont
  = do  { (floats1 :: SimplFloats
floats1, env1 :: SimplEnv
env1)  <- SimplEnv
-> [InBndr] -> [Expr InBndr] -> SimplM (SimplFloats, SimplEnv)
bind_args SimplEnv
env [InBndr]
bs [Expr InBndr]
dc_args
        ; (floats2 :: SimplFloats
floats2, env2 :: SimplEnv
env2) <- SimplEnv -> SimplM (SimplFloats, SimplEnv)
bind_case_bndr SimplEnv
env1
        ; (floats3 :: SimplFloats
floats3, expr' :: Expr InBndr
expr') <- SimplEnv
-> Expr InBndr -> SimplCont -> SimplM (SimplFloats, Expr InBndr)
simplExprF SimplEnv
env2 Expr InBndr
rhs SimplCont
cont
        ; (SimplFloats, Expr InBndr) -> SimplM (SimplFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats
floats1 SimplFloats -> SimplFloats -> SimplFloats
`addFloats` SimplFloats
floats2 SimplFloats -> SimplFloats -> SimplFloats
`addFloats` SimplFloats
floats3, Expr InBndr
expr') }
  where
    zap_occ :: InBndr -> InBndr
zap_occ = Bool -> InBndr -> InBndr
zapBndrOccInfo (InBndr -> Bool
isDeadBinder InBndr
bndr)    -- bndr is an InId

                  -- Ugh!
    bind_args :: SimplEnv
-> [InBndr] -> [Expr InBndr] -> SimplM (SimplFloats, SimplEnv)
bind_args env' :: SimplEnv
env' [] _  = (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplEnv -> SimplFloats
emptyFloats SimplEnv
env', SimplEnv
env')

    bind_args env' :: SimplEnv
env' (b :: InBndr
b:bs' :: [InBndr]
bs') (Type ty :: OutType
ty : args :: [Expr InBndr]
args)
      = ASSERT( isTyVar b )
        SimplEnv
-> [InBndr] -> [Expr InBndr] -> SimplM (SimplFloats, SimplEnv)
bind_args (SimplEnv -> InBndr -> OutType -> SimplEnv
extendTvSubst SimplEnv
env' InBndr
b OutType
ty) [InBndr]
bs' [Expr InBndr]
args

    bind_args env' :: SimplEnv
env' (b :: InBndr
b:bs' :: [InBndr]
bs') (Coercion co :: Coercion
co : args :: [Expr InBndr]
args)
      = ASSERT( isCoVar b )
        SimplEnv
-> [InBndr] -> [Expr InBndr] -> SimplM (SimplFloats, SimplEnv)
bind_args (SimplEnv -> InBndr -> Coercion -> SimplEnv
extendCvSubst SimplEnv
env' InBndr
b Coercion
co) [InBndr]
bs' [Expr InBndr]
args

    bind_args env' :: SimplEnv
env' (b :: InBndr
b:bs' :: [InBndr]
bs') (arg :: Expr InBndr
arg : args :: [Expr InBndr]
args)
      = ASSERT( isId b )
        do { let b' :: InBndr
b' = InBndr -> InBndr
zap_occ InBndr
b
             -- Note that the binder might be "dead", because it doesn't
             -- occur in the RHS; and simplNonRecX may therefore discard
             -- it via postInlineUnconditionally.
             -- Nevertheless we must keep it if the case-binder is alive,
             -- because it may be used in the con_app.  See Note [knownCon occ info]
           ; (floats1 :: SimplFloats
floats1, env2 :: SimplEnv
env2) <- SimplEnv -> InBndr -> Expr InBndr -> SimplM (SimplFloats, SimplEnv)
simplNonRecX SimplEnv
env' InBndr
b' Expr InBndr
arg  -- arg satisfies let/app invariant
           ; (floats2 :: SimplFloats
floats2, env3 :: SimplEnv
env3)  <- SimplEnv
-> [InBndr] -> [Expr InBndr] -> SimplM (SimplFloats, SimplEnv)
bind_args SimplEnv
env2 [InBndr]
bs' [Expr InBndr]
args
           ; (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats
floats1 SimplFloats -> SimplFloats -> SimplFloats
`addFloats` SimplFloats
floats2, SimplEnv
env3) }

    bind_args _ _ _ =
      [Char] -> SDoc -> SimplM (SimplFloats, SimplEnv)
forall a. HasCallStack => [Char] -> SDoc -> a
pprPanic "bind_args" (SDoc -> SimplM (SimplFloats, SimplEnv))
-> SDoc -> SimplM (SimplFloats, SimplEnv)
forall a b. (a -> b) -> a -> b
$ DataCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr DataCon
dc SDoc -> SDoc -> SDoc
$$ [InBndr] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [InBndr]
bs SDoc -> SDoc -> SDoc
$$ [Expr InBndr] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Expr InBndr]
dc_args SDoc -> SDoc -> SDoc
$$
                             [Char] -> SDoc
text "scrut:" SDoc -> SDoc -> SDoc
<+> Expr InBndr -> SDoc
forall a. Outputable a => a -> SDoc
ppr Expr InBndr
scrut

       -- It's useful to bind bndr to scrut, rather than to a fresh
       -- binding      x = Con arg1 .. argn
       -- because very often the scrut is a variable, so we avoid
       -- creating, and then subsequently eliminating, a let-binding
       -- BUT, if scrut is a not a variable, we must be careful
       -- about duplicating the arg redexes; in that case, make
       -- a new con-app from the args
    bind_case_bndr :: SimplEnv -> SimplM (SimplFloats, SimplEnv)
bind_case_bndr env :: SimplEnv
env
      | InBndr -> Bool
isDeadBinder InBndr
bndr   = (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplEnv -> SimplFloats
emptyFloats SimplEnv
env, SimplEnv
env)
      | Expr InBndr -> Bool
exprIsTrivial Expr InBndr
scrut = (SimplFloats, SimplEnv) -> SimplM (SimplFloats, SimplEnv)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplEnv -> SimplFloats
emptyFloats SimplEnv
env
                                     , SimplEnv -> InBndr -> SimplSR -> SimplEnv
extendIdSubst SimplEnv
env InBndr
bndr (Expr InBndr -> Maybe Int -> SimplSR
DoneEx Expr InBndr
scrut Maybe Int
forall a. Maybe a
Nothing))
      | Bool
otherwise           = do { [Expr InBndr]
dc_args <- (InBndr -> SimplM (Expr InBndr))
-> [InBndr] -> SimplM [Expr InBndr]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (SimplEnv -> InBndr -> SimplM (Expr InBndr)
simplVar SimplEnv
env) [InBndr]
bs
                                         -- dc_ty_args are aready OutTypes,
                                         -- but bs are InBndrs
                                 ; let con_app :: Expr InBndr
con_app = InBndr -> Expr InBndr
forall b. InBndr -> Expr b
Var (DataCon -> InBndr
dataConWorkId DataCon
dc)
                                                 Expr InBndr -> [OutType] -> Expr InBndr
forall b. Expr b -> [OutType] -> Expr b
`mkTyApps` [OutType]
dc_ty_args
                                                 Expr InBndr -> [Expr InBndr] -> Expr InBndr
forall b. Expr b -> [Expr b] -> Expr b
`mkApps`   [Expr InBndr]
dc_args
                                 ; SimplEnv -> InBndr -> Expr InBndr -> SimplM (SimplFloats, SimplEnv)
simplNonRecX SimplEnv
env InBndr
bndr Expr InBndr
con_app }

-------------------
missingAlt :: SimplEnv -> Id -> [InAlt] -> SimplCont
           -> SimplM (SimplFloats, OutExpr)
                -- This isn't strictly an error, although it is unusual.
                -- It's possible that the simplifier might "see" that
                -- an inner case has no accessible alternatives before
                -- it "sees" that the entire branch of an outer case is
                -- inaccessible.  So we simply put an error case here instead.
missingAlt :: SimplEnv
-> InBndr
-> [Alt InBndr]
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
missingAlt env :: SimplEnv
env case_bndr :: InBndr
case_bndr _ cont :: SimplCont
cont
  = WARN( True, text "missingAlt" <+> ppr case_bndr )
    -- See Note [Avoiding space leaks in OutType]
    let cont_ty :: OutType
cont_ty = SimplCont -> OutType
contResultType SimplCont
cont
    in OutType -> ()
seqType OutType
cont_ty ()
-> SimplM (SimplFloats, Expr InBndr)
-> SimplM (SimplFloats, Expr InBndr)
forall a b. a -> b -> b
`seq`
       (SimplFloats, Expr InBndr) -> SimplM (SimplFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplEnv -> SimplFloats
emptyFloats SimplEnv
env, OutType -> Expr InBndr
mkImpossibleExpr OutType
cont_ty)

{-
************************************************************************
*                                                                      *
\subsection{Duplicating continuations}
*                                                                      *
************************************************************************

Consider
  let x* = case e of { True -> e1; False -> e2 }
  in b
where x* is a strict binding.  Then mkDupableCont will be given
the continuation
   case [] of { True -> e1; False -> e2 } ; let x* = [] in b ; stop
and will split it into
   dupable:      case [] of { True -> $j1; False -> $j2 } ; stop
   join floats:  $j1 = e1, $j2 = e2
   non_dupable:  let x* = [] in b; stop

Putting this back together would give
   let x* = let { $j1 = e1; $j2 = e2 } in
            case e of { True -> $j1; False -> $j2 }
   in b
(Of course we only do this if 'e' wants to duplicate that continuation.)
Note how important it is that the new join points wrap around the
inner expression, and not around the whole thing.

In contrast, any let-bindings introduced by mkDupableCont can wrap
around the entire thing.

Note [Bottom alternatives]
~~~~~~~~~~~~~~~~~~~~~~~~~~
When we have
     case (case x of { A -> error .. ; B -> e; C -> error ..)
       of alts
then we can just duplicate those alts because the A and C cases
will disappear immediately.  This is more direct than creating
join points and inlining them away.  See Trac #4930.
-}

--------------------
mkDupableCaseCont :: SimplEnv -> [InAlt] -> SimplCont
                  -> SimplM (SimplFloats, SimplCont)
mkDupableCaseCont :: SimplEnv
-> [Alt InBndr] -> SimplCont -> SimplM (SimplFloats, SimplCont)
mkDupableCaseCont env :: SimplEnv
env alts :: [Alt InBndr]
alts cont :: SimplCont
cont
  | [Alt InBndr] -> Bool
altsWouldDup [Alt InBndr]
alts = SimplEnv -> SimplCont -> SimplM (SimplFloats, SimplCont)
mkDupableCont SimplEnv
env SimplCont
cont
  | Bool
otherwise         = (SimplFloats, SimplCont) -> SimplM (SimplFloats, SimplCont)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplEnv -> SimplFloats
emptyFloats SimplEnv
env, SimplCont
cont)

altsWouldDup :: [InAlt] -> Bool -- True iff strictly > 1 non-bottom alternative
altsWouldDup :: [Alt InBndr] -> Bool
altsWouldDup []  = Bool
False        -- See Note [Bottom alternatives]
altsWouldDup [_] = Bool
False
altsWouldDup (alt :: Alt InBndr
alt:alts :: [Alt InBndr]
alts)
  | Alt InBndr -> Bool
forall a b. (a, b, Expr InBndr) -> Bool
is_bot_alt Alt InBndr
alt = [Alt InBndr] -> Bool
altsWouldDup [Alt InBndr]
alts
  | Bool
otherwise      = Bool -> Bool
not ((Alt InBndr -> Bool) -> [Alt InBndr] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
all Alt InBndr -> Bool
forall a b. (a, b, Expr InBndr) -> Bool
is_bot_alt [Alt InBndr]
alts)
  where
    is_bot_alt :: (a, b, Expr InBndr) -> Bool
is_bot_alt (_,_,rhs :: Expr InBndr
rhs) = Expr InBndr -> Bool
exprIsBottom Expr InBndr
rhs

-------------------------
mkDupableCont :: SimplEnv -> SimplCont
              -> SimplM ( SimplFloats  -- Incoming SimplEnv augmented with
                                       --   extra let/join-floats and in-scope variables
                        , SimplCont)   -- dup_cont: duplicable continuation

mkDupableCont :: SimplEnv -> SimplCont -> SimplM (SimplFloats, SimplCont)
mkDupableCont env :: SimplEnv
env cont :: SimplCont
cont
  | SimplCont -> Bool
contIsDupable SimplCont
cont
  = (SimplFloats, SimplCont) -> SimplM (SimplFloats, SimplCont)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplEnv -> SimplFloats
emptyFloats SimplEnv
env, SimplCont
cont)

mkDupableCont _ (Stop {}) = [Char] -> SimplM (SimplFloats, SimplCont)
forall a. [Char] -> a
panic "mkDupableCont"     -- Handled by previous eqn

mkDupableCont env :: SimplEnv
env (CastIt ty :: Coercion
ty cont :: SimplCont
cont)
  = do  { (floats :: SimplFloats
floats, cont' :: SimplCont
cont') <- SimplEnv -> SimplCont -> SimplM (SimplFloats, SimplCont)
mkDupableCont SimplEnv
env SimplCont
cont
        ; (SimplFloats, SimplCont) -> SimplM (SimplFloats, SimplCont)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats
floats, Coercion -> SimplCont -> SimplCont
CastIt Coercion
ty SimplCont
cont') }

-- Duplicating ticks for now, not sure if this is good or not
mkDupableCont env :: SimplEnv
env (TickIt t :: Tickish InBndr
t cont :: SimplCont
cont)
  = do  { (floats :: SimplFloats
floats, cont' :: SimplCont
cont') <- SimplEnv -> SimplCont -> SimplM (SimplFloats, SimplCont)
mkDupableCont SimplEnv
env SimplCont
cont
        ; (SimplFloats, SimplCont) -> SimplM (SimplFloats, SimplCont)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats
floats, Tickish InBndr -> SimplCont -> SimplCont
TickIt Tickish InBndr
t SimplCont
cont') }

mkDupableCont env :: SimplEnv
env (StrictBind { sc_bndr :: SimplCont -> InBndr
sc_bndr = InBndr
bndr, sc_bndrs :: SimplCont -> [InBndr]
sc_bndrs = [InBndr]
bndrs
                              , sc_body :: SimplCont -> Expr InBndr
sc_body = Expr InBndr
body, sc_env :: SimplCont -> SimplEnv
sc_env = SimplEnv
se, sc_cont :: SimplCont -> SimplCont
sc_cont = SimplCont
cont})
  -- See Note [Duplicating StrictBind]
  = do { let sb_env :: SimplEnv
sb_env = SimplEnv
se SimplEnv -> SimplEnv -> SimplEnv
`setInScopeFromE` SimplEnv
env
       ; (sb_env1 :: SimplEnv
sb_env1, bndr' :: InBndr
bndr') <- SimplEnv -> InBndr -> SimplM (SimplEnv, InBndr)
simplBinder SimplEnv
sb_env InBndr
bndr
       ; (floats1 :: SimplFloats
floats1, join_inner :: Expr InBndr
join_inner) <- SimplEnv
-> [InBndr]
-> Expr InBndr
-> SimplCont
-> SimplM (SimplFloats, Expr InBndr)
simplLam SimplEnv
sb_env1 [InBndr]
bndrs Expr InBndr
body SimplCont
cont
          -- No need to use mkDupableCont before simplLam; we
          -- use cont once here, and then share the result if necessary

       ; let join_body :: Expr InBndr
join_body = SimplFloats -> Expr InBndr -> Expr InBndr
wrapFloats SimplFloats
floats1 Expr InBndr
join_inner
             res_ty :: OutType
res_ty    = SimplCont -> OutType
contResultType SimplCont
cont

       ; (floats2 :: SimplFloats
floats2, body2 :: Expr InBndr
body2)
            <- if DynFlags -> Expr InBndr -> Bool
exprIsDupable (SimplEnv -> DynFlags
seDynFlags SimplEnv
env) Expr InBndr
join_body
               then (SimplFloats, Expr InBndr) -> SimplM (SimplFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplEnv -> SimplFloats
emptyFloats SimplEnv
env, Expr InBndr
join_body)
               else do { InBndr
join_bndr <- [InBndr] -> OutType -> SimplM InBndr
newJoinId [InBndr
bndr'] OutType
res_ty
                       ; let join_call :: Expr b
join_call = Expr b -> Expr b -> Expr b
forall b. Expr b -> Expr b -> Expr b
App (InBndr -> Expr b
forall b. InBndr -> Expr b
Var InBndr
join_bndr) (InBndr -> Expr b
forall b. InBndr -> Expr b
Var InBndr
bndr')
                             join_rhs :: Expr InBndr
join_rhs  = InBndr -> Expr InBndr -> Expr InBndr
forall b. b -> Expr b -> Expr b
Lam (InBndr -> InBndr
setOneShotLambda InBndr
bndr') Expr InBndr
join_body
                             join_bind :: InBind
join_bind = InBndr -> Expr InBndr -> InBind
forall b. b -> Expr b -> Bind b
NonRec InBndr
join_bndr Expr InBndr
join_rhs
                             floats :: SimplFloats
floats    = SimplEnv -> SimplFloats
emptyFloats SimplEnv
env SimplFloats -> InBind -> SimplFloats
`extendFloats` InBind
join_bind
                       ; (SimplFloats, Expr InBndr) -> SimplM (SimplFloats, Expr InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats
floats, Expr InBndr
forall b. Expr b
join_call) }
       ; (SimplFloats, SimplCont) -> SimplM (SimplFloats, SimplCont)
forall (m :: * -> *) a. Monad m => a -> m a
return ( SimplFloats
floats2
                , StrictBind :: DupFlag
-> InBndr
-> [InBndr]
-> Expr InBndr
-> SimplEnv
-> SimplCont
-> SimplCont
StrictBind { sc_bndr :: InBndr
sc_bndr = InBndr
bndr', sc_bndrs :: [InBndr]
sc_bndrs = []
                             , sc_body :: Expr InBndr
sc_body = Expr InBndr
body2
                             , sc_env :: SimplEnv
sc_env  = SimplEnv -> SimplEnv
zapSubstEnv SimplEnv
se SimplEnv -> SimplFloats -> SimplEnv
`setInScopeFromF` SimplFloats
floats2
                                         -- See Note [StaticEnv invariant] in SimplUtils
                             , sc_dup :: DupFlag
sc_dup  = DupFlag
OkToDup
                             , sc_cont :: SimplCont
sc_cont = OutType -> SimplCont
mkBoringStop OutType
res_ty } ) }

mkDupableCont env :: SimplEnv
env (StrictArg { sc_fun :: SimplCont -> ArgInfo
sc_fun = ArgInfo
info, sc_cci :: SimplCont -> CallCtxt
sc_cci = CallCtxt
cci, sc_cont :: SimplCont -> SimplCont
sc_cont = SimplCont
cont })
        -- See Note [Duplicating StrictArg]
        -- NB: sc_dup /= OkToDup; that is caught earlier by contIsDupable
  = do { (floats1 :: SimplFloats
floats1, cont' :: SimplCont
cont') <- SimplEnv -> SimplCont -> SimplM (SimplFloats, SimplCont)
mkDupableCont SimplEnv
env SimplCont
cont
       ; (floats_s :: [LetFloats]
floats_s, args' :: [ArgSpec]
args') <- (ArgSpec -> SimplM (LetFloats, ArgSpec))
-> [ArgSpec] -> SimplM ([LetFloats], [ArgSpec])
forall (m :: * -> *) a b c.
Applicative m =>
(a -> m (b, c)) -> [a] -> m ([b], [c])
mapAndUnzipM (SimplMode -> ArgSpec -> SimplM (LetFloats, ArgSpec)
makeTrivialArg (SimplEnv -> SimplMode
getMode SimplEnv
env))
                                           (ArgInfo -> [ArgSpec]
ai_args ArgInfo
info)
       ; (SimplFloats, SimplCont) -> SimplM (SimplFloats, SimplCont)
forall (m :: * -> *) a. Monad m => a -> m a
return ( (SimplFloats -> LetFloats -> SimplFloats)
-> SimplFloats -> [LetFloats] -> SimplFloats
forall (t :: * -> *) b a.
Foldable t =>
(b -> a -> b) -> b -> t a -> b
foldl' SimplFloats -> LetFloats -> SimplFloats
addLetFloats SimplFloats
floats1 [LetFloats]
floats_s
                , StrictArg :: DupFlag -> ArgInfo -> CallCtxt -> SimplCont -> SimplCont
StrictArg { sc_fun :: ArgInfo
sc_fun = ArgInfo
info { ai_args :: [ArgSpec]
ai_args = [ArgSpec]
args' }
                            , sc_cci :: CallCtxt
sc_cci = CallCtxt
cci
                            , sc_cont :: SimplCont
sc_cont = SimplCont
cont'
                            , sc_dup :: DupFlag
sc_dup = DupFlag
OkToDup} ) }

mkDupableCont env :: SimplEnv
env (ApplyToTy { sc_cont :: SimplCont -> SimplCont
sc_cont = SimplCont
cont
                             , sc_arg_ty :: SimplCont -> OutType
sc_arg_ty = OutType
arg_ty, sc_hole_ty :: SimplCont -> OutType
sc_hole_ty = OutType
hole_ty })
  = do  { (floats :: SimplFloats
floats, cont' :: SimplCont
cont') <- SimplEnv -> SimplCont -> SimplM (SimplFloats, SimplCont)
mkDupableCont SimplEnv
env SimplCont
cont
        ; (SimplFloats, SimplCont) -> SimplM (SimplFloats, SimplCont)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats
floats, ApplyToTy :: OutType -> OutType -> SimplCont -> SimplCont
ApplyToTy { sc_cont :: SimplCont
sc_cont = SimplCont
cont'
                                    , sc_arg_ty :: OutType
sc_arg_ty = OutType
arg_ty, sc_hole_ty :: OutType
sc_hole_ty = OutType
hole_ty }) }

mkDupableCont env :: SimplEnv
env (ApplyToVal { sc_arg :: SimplCont -> Expr InBndr
sc_arg = Expr InBndr
arg, sc_dup :: SimplCont -> DupFlag
sc_dup = DupFlag
dup
                              , sc_env :: SimplCont -> SimplEnv
sc_env = SimplEnv
se, sc_cont :: SimplCont -> SimplCont
sc_cont = SimplCont
cont })
  =     -- e.g.         [...hole...] (...arg...)
        --      ==>
        --              let a = ...arg...
        --              in [...hole...] a
        -- NB: sc_dup /= OkToDup; that is caught earlier by contIsDupable
    do  { (floats1 :: SimplFloats
floats1, cont' :: SimplCont
cont') <- SimplEnv -> SimplCont -> SimplM (SimplFloats, SimplCont)
mkDupableCont SimplEnv
env SimplCont
cont
        ; let env' :: SimplEnv
env' = SimplEnv
env SimplEnv -> SimplFloats -> SimplEnv
`setInScopeFromF` SimplFloats
floats1
        ; (_, se' :: SimplEnv
se', arg' :: Expr InBndr
arg') <- SimplEnv
-> DupFlag
-> SimplEnv
-> Expr InBndr
-> SimplM (DupFlag, SimplEnv, Expr InBndr)
simplArg SimplEnv
env' DupFlag
dup SimplEnv
se Expr InBndr
arg
        ; (let_floats2 :: LetFloats
let_floats2, arg'' :: Expr InBndr
arg'') <- SimplMode
-> TopLevelFlag
-> FastString
-> Expr InBndr
-> SimplM (LetFloats, Expr InBndr)
makeTrivial (SimplEnv -> SimplMode
getMode SimplEnv
env) TopLevelFlag
NotTopLevel ([Char] -> FastString
fsLit "karg") Expr InBndr
arg'
        ; let all_floats :: SimplFloats
all_floats = SimplFloats
floats1 SimplFloats -> LetFloats -> SimplFloats
`addLetFloats` LetFloats
let_floats2
        ; (SimplFloats, SimplCont) -> SimplM (SimplFloats, SimplCont)
forall (m :: * -> *) a. Monad m => a -> m a
return ( SimplFloats
all_floats
                 , ApplyToVal :: DupFlag -> Expr InBndr -> SimplEnv -> SimplCont -> SimplCont
ApplyToVal { sc_arg :: Expr InBndr
sc_arg = Expr InBndr
arg''
                              , sc_env :: SimplEnv
sc_env = SimplEnv
se' SimplEnv -> SimplFloats -> SimplEnv
`setInScopeFromF` SimplFloats
all_floats
                                         -- Ensure that sc_env includes the free vars of
                                         -- arg'' in its in-scope set, even if makeTrivial
                                         -- has turned arg'' into a fresh variable
                                         -- See Note [StaticEnv invariant] in SimplUtils
                              , sc_dup :: DupFlag
sc_dup = DupFlag
OkToDup, sc_cont :: SimplCont
sc_cont = SimplCont
cont' }) }

mkDupableCont env :: SimplEnv
env (Select { sc_bndr :: SimplCont -> InBndr
sc_bndr = InBndr
case_bndr, sc_alts :: SimplCont -> [Alt InBndr]
sc_alts = [Alt InBndr]
alts
                          , sc_env :: SimplCont -> SimplEnv
sc_env = SimplEnv
se, sc_cont :: SimplCont -> SimplCont
sc_cont = SimplCont
cont })
  =     -- e.g.         (case [...hole...] of { pi -> ei })
        --      ===>
        --              let ji = \xij -> ei
        --              in case [...hole...] of { pi -> ji xij }
        -- NB: sc_dup /= OkToDup; that is caught earlier by contIsDupable
    do  { Tick -> SimplM ()
tick (InBndr -> Tick
CaseOfCase InBndr
case_bndr)
        ; (floats :: SimplFloats
floats, alt_cont :: SimplCont
alt_cont) <- SimplEnv
-> [Alt InBndr] -> SimplCont -> SimplM (SimplFloats, SimplCont)
mkDupableCaseCont SimplEnv
env [Alt InBndr]
alts SimplCont
cont
                -- NB: We call mkDupableCaseCont here to make cont duplicable
                --     (if necessary, depending on the number of alts)
                -- And this is important: see Note [Fusing case continuations]

        ; let alt_env :: SimplEnv
alt_env = SimplEnv
se SimplEnv -> SimplFloats -> SimplEnv
`setInScopeFromF` SimplFloats
floats
        ; (alt_env' :: SimplEnv
alt_env', case_bndr' :: InBndr
case_bndr') <- SimplEnv -> InBndr -> SimplM (SimplEnv, InBndr)
simplBinder SimplEnv
alt_env InBndr
case_bndr
        ; [Alt InBndr]
alts' <- (Alt InBndr -> SimplM (Alt InBndr))
-> [Alt InBndr] -> SimplM [Alt InBndr]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (SimplEnv
-> Maybe (Expr InBndr)
-> [AltCon]
-> InBndr
-> SimplCont
-> Alt InBndr
-> SimplM (Alt InBndr)
simplAlt SimplEnv
alt_env' Maybe (Expr InBndr)
forall a. Maybe a
Nothing [] InBndr
case_bndr' SimplCont
alt_cont) [Alt InBndr]
alts
        -- Safe to say that there are no handled-cons for the DEFAULT case
                -- NB: simplBinder does not zap deadness occ-info, so
                -- a dead case_bndr' will still advertise its deadness
                -- This is really important because in
                --      case e of b { (# p,q #) -> ... }
                -- b is always dead, and indeed we are not allowed to bind b to (# p,q #),
                -- which might happen if e was an explicit unboxed pair and b wasn't marked dead.
                -- In the new alts we build, we have the new case binder, so it must retain
                -- its deadness.
        -- NB: we don't use alt_env further; it has the substEnv for
        --     the alternatives, and we don't want that

        ; (join_floats :: JoinFloats
join_floats, alts'' :: [Alt InBndr]
alts'') <- (JoinFloats -> Alt InBndr -> SimplM (JoinFloats, Alt InBndr))
-> JoinFloats -> [Alt InBndr] -> SimplM (JoinFloats, [Alt InBndr])
forall (m :: * -> *) acc x y.
Monad m =>
(acc -> x -> m (acc, y)) -> acc -> [x] -> m (acc, [y])
mapAccumLM (DynFlags
-> InBndr
-> JoinFloats
-> Alt InBndr
-> SimplM (JoinFloats, Alt InBndr)
mkDupableAlt (SimplEnv -> DynFlags
seDynFlags SimplEnv
env) InBndr
case_bndr')
                                              JoinFloats
emptyJoinFloats [Alt InBndr]
alts'

        ; let all_floats :: SimplFloats
all_floats = SimplFloats
floats SimplFloats -> JoinFloats -> SimplFloats
`addJoinFloats` JoinFloats
join_floats
                           -- Note [Duplicated env]
        ; (SimplFloats, SimplCont) -> SimplM (SimplFloats, SimplCont)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplFloats
all_floats
                 , Select :: DupFlag
-> InBndr -> [Alt InBndr] -> SimplEnv -> SimplCont -> SimplCont
Select { sc_dup :: DupFlag
sc_dup  = DupFlag
OkToDup
                          , sc_bndr :: InBndr
sc_bndr = InBndr
case_bndr'
                          , sc_alts :: [Alt InBndr]
sc_alts = [Alt InBndr]
alts''
                          , sc_env :: SimplEnv
sc_env  = SimplEnv -> SimplEnv
zapSubstEnv SimplEnv
se SimplEnv -> SimplFloats -> SimplEnv
`setInScopeFromF` SimplFloats
all_floats
                                      -- See Note [StaticEnv invariant] in SimplUtils
                          , sc_cont :: SimplCont
sc_cont = OutType -> SimplCont
mkBoringStop (SimplCont -> OutType
contResultType SimplCont
cont) } ) }

mkDupableAlt :: DynFlags -> OutId
             -> JoinFloats -> OutAlt
             -> SimplM (JoinFloats, OutAlt)
mkDupableAlt :: DynFlags
-> InBndr
-> JoinFloats
-> Alt InBndr
-> SimplM (JoinFloats, Alt InBndr)
mkDupableAlt dflags :: DynFlags
dflags case_bndr :: InBndr
case_bndr jfloats :: JoinFloats
jfloats (con :: AltCon
con, bndrs' :: [InBndr]
bndrs', rhs' :: Expr InBndr
rhs')
  | DynFlags -> Expr InBndr -> Bool
exprIsDupable DynFlags
dflags Expr InBndr
rhs'  -- Note [Small alternative rhs]
  = (JoinFloats, Alt InBndr) -> SimplM (JoinFloats, Alt InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (JoinFloats
jfloats, (AltCon
con, [InBndr]
bndrs', Expr InBndr
rhs'))

  | Bool
otherwise
  = do  { let rhs_ty' :: OutType
rhs_ty'  = Expr InBndr -> OutType
exprType Expr InBndr
rhs'
              scrut_ty :: OutType
scrut_ty = InBndr -> OutType
idType InBndr
case_bndr
              case_bndr_w_unf :: InBndr
case_bndr_w_unf
                = case AltCon
con of
                      DEFAULT    -> InBndr
case_bndr
                      DataAlt dc :: DataCon
dc -> InBndr -> Unfolding -> InBndr
setIdUnfolding InBndr
case_bndr Unfolding
unf
                          where
                                 -- See Note [Case binders and join points]
                             unf :: Unfolding
unf = Expr InBndr -> Unfolding
mkInlineUnfolding Expr InBndr
forall b. Expr b
rhs
                             rhs :: Expr b
rhs = DataCon -> [OutType] -> [InBndr] -> Expr b
forall b. DataCon -> [OutType] -> [InBndr] -> Expr b
mkConApp2 DataCon
dc (OutType -> [OutType]
tyConAppArgs OutType
scrut_ty) [InBndr]
bndrs'

                      LitAlt {} -> WARN( True, text "mkDupableAlt"
                                                <+> ppr case_bndr <+> ppr con )
                                   InBndr
case_bndr
                           -- The case binder is alive but trivial, so why has
                           -- it not been substituted away?

              final_bndrs' :: [InBndr]
final_bndrs'
                | InBndr -> Bool
isDeadBinder InBndr
case_bndr = (InBndr -> Bool) -> [InBndr] -> [InBndr]
forall a. (a -> Bool) -> [a] -> [a]
filter InBndr -> Bool
abstract_over [InBndr]
bndrs'
                | Bool
otherwise              = [InBndr]
bndrs' [InBndr] -> [InBndr] -> [InBndr]
forall a. [a] -> [a] -> [a]
++ [InBndr
case_bndr_w_unf]

              abstract_over :: InBndr -> Bool
abstract_over bndr :: InBndr
bndr
                  | InBndr -> Bool
isTyVar InBndr
bndr = Bool
True -- Abstract over all type variables just in case
                  | Bool
otherwise    = Bool -> Bool
not (InBndr -> Bool
isDeadBinder InBndr
bndr)
                        -- The deadness info on the new Ids is preserved by simplBinders
              final_args :: [Expr b]
final_args = [InBndr] -> [Expr b]
forall b. [InBndr] -> [Expr b]
varsToCoreExprs [InBndr]
final_bndrs'
                           -- Note [Join point abstraction]

                -- We make the lambdas into one-shot-lambdas.  The
                -- join point is sure to be applied at most once, and doing so
                -- prevents the body of the join point being floated out by
                -- the full laziness pass
              really_final_bndrs :: [InBndr]
really_final_bndrs     = (InBndr -> InBndr) -> [InBndr] -> [InBndr]
forall a b. (a -> b) -> [a] -> [b]
map InBndr -> InBndr
one_shot [InBndr]
final_bndrs'
              one_shot :: InBndr -> InBndr
one_shot v :: InBndr
v | InBndr -> Bool
isId InBndr
v    = InBndr -> InBndr
setOneShotLambda InBndr
v
                         | Bool
otherwise = InBndr
v
              join_rhs :: Expr InBndr
join_rhs   = [InBndr] -> Expr InBndr -> Expr InBndr
forall b. [b] -> Expr b -> Expr b
mkLams [InBndr]
really_final_bndrs Expr InBndr
rhs'

        ; InBndr
join_bndr <- [InBndr] -> OutType -> SimplM InBndr
newJoinId [InBndr]
final_bndrs' OutType
rhs_ty'

        ; let join_call :: Expr b
join_call = Expr b -> [Expr b] -> Expr b
forall b. Expr b -> [Expr b] -> Expr b
mkApps (InBndr -> Expr b
forall b. InBndr -> Expr b
Var InBndr
join_bndr) [Expr b]
forall b. [Expr b]
final_args
              alt' :: (AltCon, [InBndr], Expr b)
alt'      = (AltCon
con, [InBndr]
bndrs', Expr b
forall b. Expr b
join_call)

        ; (JoinFloats, Alt InBndr) -> SimplM (JoinFloats, Alt InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return ( JoinFloats
jfloats JoinFloats -> JoinFloats -> JoinFloats
`addJoinFlts` InBind -> JoinFloats
unitJoinFloat (InBndr -> Expr InBndr -> InBind
forall b. b -> Expr b -> Bind b
NonRec InBndr
join_bndr Expr InBndr
join_rhs)
                 , Alt InBndr
forall b. (AltCon, [InBndr], Expr b)
alt') }
                -- See Note [Duplicated env]

{-
Note [Fusing case continuations]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
It's important to fuse two successive case continuations when the
first has one alternative.  That's why we call prepareCaseCont here.
Consider this, which arises from thunk splitting (see Note [Thunk
splitting] in WorkWrap):

      let
        x* = case (case v of {pn -> rn}) of
               I# a -> I# a
      in body

The simplifier will find
    (Var v) with continuation
            Select (pn -> rn) (
            Select [I# a -> I# a] (
            StrictBind body Stop

So we'll call mkDupableCont on
   Select [I# a -> I# a] (StrictBind body Stop)
There is just one alternative in the first Select, so we want to
simplify the rhs (I# a) with continuation (StrictBind body Stop)
Supposing that body is big, we end up with
          let $j a = <let x = I# a in body>
          in case v of { pn -> case rn of
                                 I# a -> $j a }
This is just what we want because the rn produces a box that
the case rn cancels with.

See Trac #4957 a fuller example.

Note [Case binders and join points]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider this
   case (case .. ) of c {
     I# c# -> ....c....

If we make a join point with c but not c# we get
  $j = \c -> ....c....

But if later inlining scrutinises the c, thus

  $j = \c -> ... case c of { I# y -> ... } ...

we won't see that 'c' has already been scrutinised.  This actually
happens in the 'tabulate' function in wave4main, and makes a significant
difference to allocation.

An alternative plan is this:

   $j = \c# -> let c = I# c# in ...c....

but that is bad if 'c' is *not* later scrutinised.

So instead we do both: we pass 'c' and 'c#' , and record in c's inlining
(a stable unfolding) that it's really I# c#, thus

   $j = \c# -> \c[=I# c#] -> ...c....

Absence analysis may later discard 'c'.

NB: take great care when doing strictness analysis;
    see Note [Lambda-bound unfoldings] in DmdAnal.

Also note that we can still end up passing stuff that isn't used.  Before
strictness analysis we have
   let $j x y c{=(x,y)} = (h c, ...)
   in ...
After strictness analysis we see that h is strict, we end up with
   let $j x y c{=(x,y)} = ($wh x y, ...)
and c is unused.

Note [Duplicated env]
~~~~~~~~~~~~~~~~~~~~~
Some of the alternatives are simplified, but have not been turned into a join point
So they *must* have a zapped subst-env.  So we can't use completeNonRecX to
bind the join point, because it might to do PostInlineUnconditionally, and
we'd lose that when zapping the subst-env.  We could have a per-alt subst-env,
but zapping it (as we do in mkDupableCont, the Select case) is safe, and
at worst delays the join-point inlining.

Note [Small alternative rhs]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
It is worth checking for a small RHS because otherwise we
get extra let bindings that may cause an extra iteration of the simplifier to
inline back in place.  Quite often the rhs is just a variable or constructor.
The Ord instance of Maybe in PrelMaybe.hs, for example, took several extra
iterations because the version with the let bindings looked big, and so wasn't
inlined, but after the join points had been inlined it looked smaller, and so
was inlined.

NB: we have to check the size of rhs', not rhs.
Duplicating a small InAlt might invalidate occurrence information
However, if it *is* dupable, we return the *un* simplified alternative,
because otherwise we'd need to pair it up with an empty subst-env....
but we only have one env shared between all the alts.
(Remember we must zap the subst-env before re-simplifying something).
Rather than do this we simply agree to re-simplify the original (small) thing later.

Note [Funky mkLamTypes]
~~~~~~~~~~~~~~~~~~~~~~
Notice the funky mkLamTypes.  If the constructor has existentials
it's possible that the join point will be abstracted over
type variables as well as term variables.
 Example:  Suppose we have
        data T = forall t.  C [t]
 Then faced with
        case (case e of ...) of
            C t xs::[t] -> rhs
 We get the join point
        let j :: forall t. [t] -> ...
            j = /\t \xs::[t] -> rhs
        in
        case (case e of ...) of
            C t xs::[t] -> j t xs

Note [Duplicating StrictArg]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We make a StrictArg duplicable simply by making all its
stored-up arguments (in sc_fun) trivial, by let-binding
them.  Thus:
        f E [..hole..]
        ==>     let a = E
                in f a [..hole..]
Now if the thing in the hole is a case expression (which is when
we'll call mkDupableCont), we'll push the function call into the
branches, which is what we want.  Now RULES for f may fire, and
call-pattern specialisation.  Here's an example from Trac #3116
     go (n+1) (case l of
                 1  -> bs'
                 _  -> Chunk p fpc (o+1) (l-1) bs')
If we can push the call for 'go' inside the case, we get
call-pattern specialisation for 'go', which is *crucial* for
this program.

Here is the (&&) example:
        && E (case x of { T -> F; F -> T })
  ==>   let a = E in
        case x of { T -> && a F; F -> && a T }
Much better!

Notice that
  * Arguments to f *after* the strict one are handled by
    the ApplyToVal case of mkDupableCont.  Eg
        f [..hole..] E

  * We can only do the let-binding of E because the function
    part of a StrictArg continuation is an explicit syntax
    tree.  In earlier versions we represented it as a function
    (CoreExpr -> CoreEpxr) which we couldn't take apart.

Historical aide: previously we did this (where E is a
big argument:
        f E [..hole..]
        ==>     let $j = \a -> f E a
                in $j [..hole..]

But this is terrible! Here's an example:
        && E (case x of { T -> F; F -> T })
Now, && is strict so we end up simplifying the case with
an ArgOf continuation.  If we let-bind it, we get
        let $j = \v -> && E v
        in simplExpr (case x of { T -> F; F -> T })
                     (ArgOf (\r -> $j r)
And after simplifying more we get
        let $j = \v -> && E v
        in case x of { T -> $j F; F -> $j T }
Which is a Very Bad Thing


Note [Duplicating StrictBind]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We make a StrictBind duplicable in a very similar way to
that for case expressions.  After all,
   let x* = e in b   is similar to    case e of x -> b

So we potentially make a join-point for the body, thus:
   let x = [] in b   ==>   join j x = b
                           in let x = [] in j x


Note [Join point abstraction]  Historical note
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NB: This note is now historical, describing how (in the past) we used
to add a void argument to nullary join points.  But now that "join
point" is not a fuzzy concept but a formal syntactic construct (as
distinguished by the JoinId constructor of IdDetails), each of these
concerns is handled separately, with no need for a vestigial extra
argument.

Join points always have at least one value argument,
for several reasons

* If we try to lift a primitive-typed something out
  for let-binding-purposes, we will *caseify* it (!),
  with potentially-disastrous strictness results.  So
  instead we turn it into a function: \v -> e
  where v::Void#.  The value passed to this function is void,
  which generates (almost) no code.

* CPR.  We used to say "&& isUnliftedType rhs_ty'" here, but now
  we make the join point into a function whenever used_bndrs'
  is empty.  This makes the join-point more CPR friendly.
  Consider:       let j = if .. then I# 3 else I# 4
                  in case .. of { A -> j; B -> j; C -> ... }

  Now CPR doesn't w/w j because it's a thunk, so
  that means that the enclosing function can't w/w either,
  which is a lose.  Here's the example that happened in practice:
          kgmod :: Int -> Int -> Int
          kgmod x y = if x > 0 && y < 0 || x < 0 && y > 0
                      then 78
                      else 5

* Let-no-escape.  We want a join point to turn into a let-no-escape
  so that it is implemented as a jump, and one of the conditions
  for LNE is that it's not updatable.  In CoreToStg, see
  Note [What is a non-escaping let]

* Floating.  Since a join point will be entered once, no sharing is
  gained by floating out, but something might be lost by doing
  so because it might be allocated.

I have seen a case alternative like this:
        True -> \v -> ...
It's a bit silly to add the realWorld dummy arg in this case, making
        $j = \s v -> ...
           True -> $j s
(the \v alone is enough to make CPR happy) but I think it's rare

There's a slight infelicity here: we pass the overall
case_bndr to all the join points if it's used in *any* RHS,
because we don't know its usage in each RHS separately



************************************************************************
*                                                                      *
                    Unfoldings
*                                                                      *
************************************************************************
-}

simplLetUnfolding :: SimplEnv-> TopLevelFlag
                  -> MaybeJoinCont
                  -> InId
                  -> OutExpr -> OutType
                  -> Unfolding -> SimplM Unfolding
simplLetUnfolding :: SimplEnv
-> TopLevelFlag
-> MaybeJoinCont
-> InBndr
-> Expr InBndr
-> OutType
-> Unfolding
-> SimplM Unfolding
simplLetUnfolding env :: SimplEnv
env top_lvl :: TopLevelFlag
top_lvl cont_mb :: MaybeJoinCont
cont_mb id :: InBndr
id new_rhs :: Expr InBndr
new_rhs rhs_ty :: OutType
rhs_ty unf :: Unfolding
unf
  | Unfolding -> Bool
isStableUnfolding Unfolding
unf
  = SimplEnv
-> TopLevelFlag
-> MaybeJoinCont
-> InBndr
-> Unfolding
-> OutType
-> SimplM Unfolding
simplStableUnfolding SimplEnv
env TopLevelFlag
top_lvl MaybeJoinCont
cont_mb InBndr
id Unfolding
unf OutType
rhs_ty
  | InBndr -> Bool
isExitJoinId InBndr
id
  = Unfolding -> SimplM Unfolding
forall (m :: * -> *) a. Monad m => a -> m a
return Unfolding
noUnfolding -- See Note [Do not inline exit join points] in Exitify
  | Bool
otherwise
  = DynFlags
-> TopLevelFlag
-> UnfoldingSource
-> InBndr
-> Expr InBndr
-> SimplM Unfolding
mkLetUnfolding (SimplEnv -> DynFlags
seDynFlags SimplEnv
env) TopLevelFlag
top_lvl UnfoldingSource
InlineRhs InBndr
id Expr InBndr
new_rhs

-------------------
mkLetUnfolding :: DynFlags -> TopLevelFlag -> UnfoldingSource
               -> InId -> OutExpr -> SimplM Unfolding
mkLetUnfolding :: DynFlags
-> TopLevelFlag
-> UnfoldingSource
-> InBndr
-> Expr InBndr
-> SimplM Unfolding
mkLetUnfolding dflags :: DynFlags
dflags top_lvl :: TopLevelFlag
top_lvl src :: UnfoldingSource
src id :: InBndr
id new_rhs :: Expr InBndr
new_rhs
  = Bool
is_bottoming Bool -> SimplM Unfolding -> SimplM Unfolding
forall a b. a -> b -> b
`seq`  -- See Note [Force bottoming field]
    Unfolding -> SimplM Unfolding
forall (m :: * -> *) a. Monad m => a -> m a
return (DynFlags
-> UnfoldingSource -> Bool -> Bool -> Expr InBndr -> Unfolding
mkUnfolding DynFlags
dflags UnfoldingSource
src Bool
is_top_lvl Bool
is_bottoming Expr InBndr
new_rhs)
            -- We make an  unfolding *even for loop-breakers*.
            -- Reason: (a) It might be useful to know that they are WHNF
            --         (b) In TidyPgm we currently assume that, if we want to
            --             expose the unfolding then indeed we *have* an unfolding
            --             to expose.  (We could instead use the RHS, but currently
            --             we don't.)  The simple thing is always to have one.
  where
    is_top_lvl :: Bool
is_top_lvl   = TopLevelFlag -> Bool
isTopLevel TopLevelFlag
top_lvl
    is_bottoming :: Bool
is_bottoming = InBndr -> Bool
isBottomingId InBndr
id

-------------------
simplStableUnfolding :: SimplEnv -> TopLevelFlag
                     -> MaybeJoinCont  -- Just k => a join point with continuation k
                     -> InId
                     -> Unfolding -> OutType -> SimplM Unfolding
-- Note [Setting the new unfolding]
simplStableUnfolding :: SimplEnv
-> TopLevelFlag
-> MaybeJoinCont
-> InBndr
-> Unfolding
-> OutType
-> SimplM Unfolding
simplStableUnfolding env :: SimplEnv
env top_lvl :: TopLevelFlag
top_lvl mb_cont :: MaybeJoinCont
mb_cont id :: InBndr
id unf :: Unfolding
unf rhs_ty :: OutType
rhs_ty
  = case Unfolding
unf of
      NoUnfolding   -> Unfolding -> SimplM Unfolding
forall (m :: * -> *) a. Monad m => a -> m a
return Unfolding
unf
      BootUnfolding -> Unfolding -> SimplM Unfolding
forall (m :: * -> *) a. Monad m => a -> m a
return Unfolding
unf
      OtherCon {}   -> Unfolding -> SimplM Unfolding
forall (m :: * -> *) a. Monad m => a -> m a
return Unfolding
unf

      DFunUnfolding { df_bndrs :: Unfolding -> [InBndr]
df_bndrs = [InBndr]
bndrs, df_con :: Unfolding -> DataCon
df_con = DataCon
con, df_args :: Unfolding -> [Expr InBndr]
df_args = [Expr InBndr]
args }
        -> do { (env' :: SimplEnv
env', bndrs' :: [InBndr]
bndrs') <- SimplEnv -> [InBndr] -> SimplM (SimplEnv, [InBndr])
simplBinders SimplEnv
unf_env [InBndr]
bndrs
              ; [Expr InBndr]
args' <- (Expr InBndr -> SimplM (Expr InBndr))
-> [Expr InBndr] -> SimplM [Expr InBndr]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (SimplEnv -> Expr InBndr -> SimplM (Expr InBndr)
simplExpr SimplEnv
env') [Expr InBndr]
args
              ; Unfolding -> SimplM Unfolding
forall (m :: * -> *) a. Monad m => a -> m a
return ([InBndr] -> DataCon -> [Expr InBndr] -> Unfolding
mkDFunUnfolding [InBndr]
bndrs' DataCon
con [Expr InBndr]
args') }

      CoreUnfolding { uf_tmpl :: Unfolding -> Expr InBndr
uf_tmpl = Expr InBndr
expr, uf_src :: Unfolding -> UnfoldingSource
uf_src = UnfoldingSource
src, uf_guidance :: Unfolding -> UnfoldingGuidance
uf_guidance = UnfoldingGuidance
guide }
        | UnfoldingSource -> Bool
isStableSource UnfoldingSource
src
        -> do { Expr InBndr
expr' <- case MaybeJoinCont
mb_cont of -- See Note [Rules and unfolding for join points]
                           Just cont :: SimplCont
cont -> SimplEnv
-> InBndr -> Expr InBndr -> SimplCont -> SimplM (Expr InBndr)
simplJoinRhs SimplEnv
unf_env InBndr
id Expr InBndr
expr SimplCont
cont
                           Nothing   -> SimplEnv -> Expr InBndr -> SimplCont -> SimplM (Expr InBndr)
simplExprC SimplEnv
unf_env Expr InBndr
expr (OutType -> SimplCont
mkBoringStop OutType
rhs_ty)
              ; case UnfoldingGuidance
guide of
                  UnfWhen { ug_arity :: UnfoldingGuidance -> Int
ug_arity = Int
arity
                          , ug_unsat_ok :: UnfoldingGuidance -> Bool
ug_unsat_ok = Bool
sat_ok
                          , ug_boring_ok :: UnfoldingGuidance -> Bool
ug_boring_ok = Bool
boring_ok
                          }
                          -- Happens for INLINE things
                     -> let guide' :: UnfoldingGuidance
guide' =
                              UnfWhen :: Int -> Bool -> Bool -> UnfoldingGuidance
UnfWhen { ug_arity :: Int
ug_arity = Int
arity
                                      , ug_unsat_ok :: Bool
ug_unsat_ok = Bool
sat_ok
                                      , ug_boring_ok :: Bool
ug_boring_ok =
                                          Bool
boring_ok Bool -> Bool -> Bool
|| Expr InBndr -> Bool
inlineBoringOk Expr InBndr
expr'
                                      }
                        -- Refresh the boring-ok flag, in case expr'
                        -- has got small. This happens, notably in the inlinings
                        -- for dfuns for single-method classes; see
                        -- Note [Single-method classes] in TcInstDcls.
                        -- A test case is Trac #4138
                        -- But retain a previous boring_ok of True; e.g. see
                        -- the way it is set in calcUnfoldingGuidanceWithArity
                        in Unfolding -> SimplM Unfolding
forall (m :: * -> *) a. Monad m => a -> m a
return (UnfoldingSource
-> Bool -> Expr InBndr -> UnfoldingGuidance -> Unfolding
mkCoreUnfolding UnfoldingSource
src Bool
is_top_lvl Expr InBndr
expr' UnfoldingGuidance
guide')
                            -- See Note [Top-level flag on inline rules] in CoreUnfold

                  _other :: UnfoldingGuidance
_other              -- Happens for INLINABLE things
                     -> DynFlags
-> TopLevelFlag
-> UnfoldingSource
-> InBndr
-> Expr InBndr
-> SimplM Unfolding
mkLetUnfolding DynFlags
dflags TopLevelFlag
top_lvl UnfoldingSource
src InBndr
id Expr InBndr
expr' }
                -- If the guidance is UnfIfGoodArgs, this is an INLINABLE
                -- unfolding, and we need to make sure the guidance is kept up
                -- to date with respect to any changes in the unfolding.

        | Bool
otherwise -> Unfolding -> SimplM Unfolding
forall (m :: * -> *) a. Monad m => a -> m a
return Unfolding
noUnfolding   -- Discard unstable unfoldings
  where
    dflags :: DynFlags
dflags     = SimplEnv -> DynFlags
seDynFlags SimplEnv
env
    is_top_lvl :: Bool
is_top_lvl = TopLevelFlag -> Bool
isTopLevel TopLevelFlag
top_lvl
    act :: Activation
act        = InBndr -> Activation
idInlineActivation InBndr
id
    unf_env :: SimplEnv
unf_env    = (SimplMode -> SimplMode) -> SimplEnv -> SimplEnv
updMode (Activation -> SimplMode -> SimplMode
updModeForStableUnfoldings Activation
act) SimplEnv
env
         -- See Note [Simplifying inside stable unfoldings] in SimplUtils

{-
Note [Force bottoming field]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We need to force bottoming, or the new unfolding holds
on to the old unfolding (which is part of the id).

Note [Setting the new unfolding]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
* If there's an INLINE pragma, we simplify the RHS gently.  Maybe we
  should do nothing at all, but simplifying gently might get rid of
  more crap.

* If not, we make an unfolding from the new RHS.  But *only* for
  non-loop-breakers. Making loop breakers not have an unfolding at all
  means that we can avoid tests in exprIsConApp, for example.  This is
  important: if exprIsConApp says 'yes' for a recursive thing, then we
  can get into an infinite loop

If there's a stable unfolding on a loop breaker (which happens for
INLINABLE), we hang on to the inlining.  It's pretty dodgy, but the
user did say 'INLINE'.  May need to revisit this choice.

************************************************************************
*                                                                      *
                    Rules
*                                                                      *
************************************************************************

Note [Rules in a letrec]
~~~~~~~~~~~~~~~~~~~~~~~~
After creating fresh binders for the binders of a letrec, we
substitute the RULES and add them back onto the binders; this is done
*before* processing any of the RHSs.  This is important.  Manuel found
cases where he really, really wanted a RULE for a recursive function
to apply in that function's own right-hand side.

See Note [Forming Rec groups] in OccurAnal
-}

addBndrRules :: SimplEnv -> InBndr -> OutBndr
             -> MaybeJoinCont   -- Just k for a join point binder
                                -- Nothing otherwise
             -> SimplM (SimplEnv, OutBndr)
-- Rules are added back into the bin
addBndrRules :: SimplEnv
-> InBndr -> InBndr -> MaybeJoinCont -> SimplM (SimplEnv, InBndr)
addBndrRules env :: SimplEnv
env in_id :: InBndr
in_id out_id :: InBndr
out_id mb_cont :: MaybeJoinCont
mb_cont
  | [CoreRule] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [CoreRule]
old_rules
  = (SimplEnv, InBndr) -> SimplM (SimplEnv, InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplEnv
env, InBndr
out_id)
  | Bool
otherwise
  = do { [CoreRule]
new_rules <- SimplEnv
-> Maybe InBndr -> [CoreRule] -> MaybeJoinCont -> SimplM [CoreRule]
simplRules SimplEnv
env (InBndr -> Maybe InBndr
forall a. a -> Maybe a
Just InBndr
out_id) [CoreRule]
old_rules MaybeJoinCont
mb_cont
       ; let final_id :: InBndr
final_id  = InBndr
out_id InBndr -> RuleInfo -> InBndr
`setIdSpecialisation` [CoreRule] -> RuleInfo
mkRuleInfo [CoreRule]
new_rules
       ; (SimplEnv, InBndr) -> SimplM (SimplEnv, InBndr)
forall (m :: * -> *) a. Monad m => a -> m a
return (SimplEnv -> InBndr -> SimplEnv
modifyInScope SimplEnv
env InBndr
final_id, InBndr
final_id) }
  where
    old_rules :: [CoreRule]
old_rules = RuleInfo -> [CoreRule]
ruleInfoRules (InBndr -> RuleInfo
idSpecialisation InBndr
in_id)

simplRules :: SimplEnv -> Maybe OutId -> [CoreRule]
           -> MaybeJoinCont -> SimplM [CoreRule]
simplRules :: SimplEnv
-> Maybe InBndr -> [CoreRule] -> MaybeJoinCont -> SimplM [CoreRule]
simplRules env :: SimplEnv
env mb_new_id :: Maybe InBndr
mb_new_id rules :: [CoreRule]
rules mb_cont :: MaybeJoinCont
mb_cont
  = (CoreRule -> SimplM CoreRule) -> [CoreRule] -> SimplM [CoreRule]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM CoreRule -> SimplM CoreRule
simpl_rule [CoreRule]
rules
  where
    simpl_rule :: CoreRule -> SimplM CoreRule
simpl_rule rule :: CoreRule
rule@(BuiltinRule {})
      = CoreRule -> SimplM CoreRule
forall (m :: * -> *) a. Monad m => a -> m a
return CoreRule
rule

    simpl_rule rule :: CoreRule
rule@(Rule { ru_bndrs :: CoreRule -> [InBndr]
ru_bndrs = [InBndr]
bndrs, ru_args :: CoreRule -> [Expr InBndr]
ru_args = [Expr InBndr]
args
                          , ru_fn :: CoreRule -> Name
ru_fn = Name
fn_name, ru_rhs :: CoreRule -> Expr InBndr
ru_rhs = Expr InBndr
rhs })
      = do { (env' :: SimplEnv
env', bndrs' :: [InBndr]
bndrs') <- SimplEnv -> [InBndr] -> SimplM (SimplEnv, [InBndr])
simplBinders SimplEnv
env [InBndr]
bndrs
           ; let rhs_ty :: OutType
rhs_ty = SimplEnv -> OutType -> OutType
substTy SimplEnv
env' (Expr InBndr -> OutType
exprType Expr InBndr
rhs)
                 rhs_cont :: SimplCont
rhs_cont = case MaybeJoinCont
mb_cont of  -- See Note [Rules and unfolding for join points]
                                Nothing   -> OutType -> SimplCont
mkBoringStop OutType
rhs_ty
                                Just cont :: SimplCont
cont -> ASSERT2( join_ok, bad_join_msg )
                                             SimplCont
cont
                 rule_env :: SimplEnv
rule_env = (SimplMode -> SimplMode) -> SimplEnv -> SimplEnv
updMode SimplMode -> SimplMode
updModeForRules SimplEnv
env'
                 fn_name' :: Name
fn_name' = case Maybe InBndr
mb_new_id of
                              Just id :: InBndr
id -> InBndr -> Name
idName InBndr
id
                              Nothing -> Name
fn_name

                 -- join_ok is an assertion check that the join-arity of the
                 -- binder matches that of the rule, so that pushing the
                 -- continuation into the RHS makes sense
                 join_ok :: Bool
join_ok = case Maybe InBndr
mb_new_id of
                             Just id :: InBndr
id | Just join_arity :: Int
join_arity <- InBndr -> Maybe Int
isJoinId_maybe InBndr
id
                                     -> [Expr InBndr] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [Expr InBndr]
args Int -> Int -> Bool
forall a. Eq a => a -> a -> Bool
== Int
join_arity
                             _ -> Bool
False
                 bad_join_msg :: SDoc
bad_join_msg = [SDoc] -> SDoc
vcat [ Maybe InBndr -> SDoc
forall a. Outputable a => a -> SDoc
ppr Maybe InBndr
mb_new_id, CoreRule -> SDoc
forall a. Outputable a => a -> SDoc
ppr CoreRule
rule
                                     , Maybe (Maybe Int) -> SDoc
forall a. Outputable a => a -> SDoc
ppr ((InBndr -> Maybe Int) -> Maybe InBndr -> Maybe (Maybe Int)
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap InBndr -> Maybe Int
isJoinId_maybe Maybe InBndr
mb_new_id) ]

           ; [Expr InBndr]
args' <- (Expr InBndr -> SimplM (Expr InBndr))
-> [Expr InBndr] -> SimplM [Expr InBndr]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (SimplEnv -> Expr InBndr -> SimplM (Expr InBndr)
simplExpr SimplEnv
rule_env) [Expr InBndr]
args
           ; Expr InBndr
rhs'  <- SimplEnv -> Expr InBndr -> SimplCont -> SimplM (Expr InBndr)
simplExprC SimplEnv
rule_env Expr InBndr
rhs SimplCont
rhs_cont
           ; CoreRule -> SimplM CoreRule
forall (m :: * -> *) a. Monad m => a -> m a
return (CoreRule
rule { ru_bndrs :: [InBndr]
ru_bndrs = [InBndr]
bndrs'
                          , ru_fn :: Name
ru_fn    = Name
fn_name'
                          , ru_args :: [Expr InBndr]
ru_args  = [Expr InBndr]
args'
                          , ru_rhs :: Expr InBndr
ru_rhs   = Expr InBndr
rhs' }) }