{-# LANGUAGE DeriveFunctor #-} {-# LANGUAGE GeneralizedNewtypeDeriving #-} {-# LANGUAGE RecordWildCards #-} {-# LANGUAGE FlexibleContexts #-} {-# OPTIONS_GHC -fprof-auto-top #-} {-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-} -- -- (c) The University of Glasgow 2002-2006 -- -- | GHC.StgToByteCode: Generate bytecode from STG module GHC.StgToByteCode ( UnlinkedBCO, byteCodeGen) where import GHC.Prelude import GHC.Driver.Session import GHC.Driver.Env import GHC.ByteCode.Instr import GHC.ByteCode.Asm import GHC.ByteCode.Types import GHC.Cmm.CallConv import GHC.Cmm.Expr import GHC.Cmm.Node import GHC.Cmm.Utils import GHC.Platform import GHC.Platform.Profile import GHC.Runtime.Interpreter import GHCi.FFI import GHCi.RemoteTypes import GHC.Types.Basic import GHC.Utils.Outputable import GHC.Types.Name import GHC.Types.Id import GHC.Types.ForeignCall import GHC.Core import GHC.Types.Literal import GHC.Builtin.PrimOps import GHC.Builtin.PrimOps.Ids (primOpId) import GHC.Core.Type import GHC.Types.RepType import GHC.Core.DataCon import GHC.Core.TyCon import GHC.Utils.Misc import GHC.Utils.Logger import GHC.Types.Var.Set import GHC.Builtin.Types.Prim import GHC.Core.TyCo.Ppr ( pprType ) import GHC.Utils.Error import GHC.Types.Unique import GHC.Builtin.Uniques import GHC.Data.FastString import GHC.Utils.Panic import GHC.Utils.Panic.Plain import GHC.Utils.Exception (evaluate) import GHC.StgToCmm.Closure ( NonVoid(..), fromNonVoid, nonVoidIds ) import GHC.StgToCmm.Layout import GHC.Runtime.Heap.Layout hiding (WordOff, ByteOff, wordsToBytes) import GHC.Data.Bitmap import GHC.Data.OrdList import GHC.Data.Maybe import GHC.Types.Var.Env import GHC.Types.Tickish import Data.List ( genericReplicate, genericLength, intersperse , partition, scanl', sortBy, zip4, zip6 ) import Foreign hiding (shiftL, shiftR) import Control.Monad import Data.Char import GHC.Unit.Module import Data.Array import Data.Coerce (coerce) import Data.ByteString (ByteString) import Data.Map (Map) import Data.IntMap (IntMap) import qualified Data.Map as Map import qualified Data.IntMap as IntMap import qualified GHC.Data.FiniteMap as Map import Data.Ord import GHC.Stack.CCS import Data.Either ( partitionEithers ) import GHC.Stg.Syntax import qualified Data.IntSet as IntSet -- ----------------------------------------------------------------------------- -- Generating byte code for a complete module byteCodeGen :: HscEnv -> Module -> [CgStgTopBinding] -> [TyCon] -> Maybe ModBreaks -> IO CompiledByteCode byteCodeGen hsc_env this_mod binds tycs mb_modBreaks = withTiming logger (text "GHC.StgToByteCode"<+>brackets (ppr this_mod)) (const ()) $ do -- Split top-level binds into strings and others. -- See Note [generating code for top-level string literal bindings]. let (strings, lifted_binds) = partitionEithers $ do -- list monad bnd <- binds case bnd of StgTopLifted bnd -> [Right bnd] StgTopStringLit b str -> [Left (b, str)] flattenBind (StgNonRec b e) = [(b,e)] flattenBind (StgRec bs) = bs stringPtrs <- allocateTopStrings interp strings (BcM_State{..}, proto_bcos) <- runBc hsc_env this_mod mb_modBreaks (mkVarEnv stringPtrs) $ do let flattened_binds = concatMap flattenBind (reverse lifted_binds) mapM schemeTopBind flattened_binds when (notNull ffis) (panic "GHC.StgToByteCode.byteCodeGen: missing final emitBc?") putDumpFileMaybe logger Opt_D_dump_BCOs "Proto-BCOs" FormatByteCode (vcat (intersperse (char ' ') (map ppr proto_bcos))) cbc <- assembleBCOs interp profile proto_bcos tycs (map snd stringPtrs) (case modBreaks of Nothing -> Nothing Just mb -> Just mb{ modBreaks_breakInfo = breakInfo }) -- Squash space leaks in the CompiledByteCode. This is really -- important, because when loading a set of modules into GHCi -- we don't touch the CompiledByteCode until the end when we -- do linking. Forcing out the thunks here reduces space -- usage by more than 50% when loading a large number of -- modules. evaluate (seqCompiledByteCode cbc) return cbc where dflags = hsc_dflags hsc_env logger = hsc_logger hsc_env interp = hscInterp hsc_env profile = targetProfile dflags allocateTopStrings :: Interp -> [(Id, ByteString)] -> IO [(Var, RemotePtr ())] allocateTopStrings interp topStrings = do let !(bndrs, strings) = unzip topStrings ptrs <- interpCmd interp $ MallocStrings strings return $ zip bndrs ptrs {- Note [generating code for top-level string literal bindings] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Here is a summary on how the byte code generator deals with top-level string literals: 1. Top-level string literal bindings are separated from the rest of the module. 2. The strings are allocated via interpCmd, in allocateTopStrings 3. The mapping from binders to allocated strings (topStrings) are maintained in BcM and used when generating code for variable references. -} -- ----------------------------------------------------------------------------- -- Compilation schema for the bytecode generator type BCInstrList = OrdList BCInstr wordsToBytes :: Platform -> WordOff -> ByteOff wordsToBytes platform = fromIntegral . (* platformWordSizeInBytes platform) . fromIntegral -- Used when we know we have a whole number of words bytesToWords :: Platform -> ByteOff -> WordOff bytesToWords platform (ByteOff bytes) = let (q, r) = bytes `quotRem` (platformWordSizeInBytes platform) in if r == 0 then fromIntegral q else pprPanic "GHC.StgToByteCode.bytesToWords" (text "bytes=" <> ppr bytes) wordSize :: Platform -> ByteOff wordSize platform = ByteOff (platformWordSizeInBytes platform) type Sequel = ByteOff -- back off to this depth before ENTER type StackDepth = ByteOff -- | Maps Ids to their stack depth. This allows us to avoid having to mess with -- it after each push/pop. type BCEnv = Map Id StackDepth -- To find vars on the stack {- ppBCEnv :: BCEnv -> SDoc ppBCEnv p = text "begin-env" $$ nest 4 (vcat (map pp_one (sortBy cmp_snd (Map.toList p)))) $$ text "end-env" where pp_one (var, ByteOff offset) = int offset <> colon <+> ppr var <+> ppr (bcIdArgReps var) cmp_snd x y = compare (snd x) (snd y) -} -- Create a BCO and do a spot of peephole optimisation on the insns -- at the same time. mkProtoBCO :: Platform -> name -> BCInstrList -> Either [CgStgAlt] (CgStgRhs) -- ^ original expression; for debugging only -> Int -- ^ arity -> Word16 -- ^ bitmap size -> [StgWord] -- ^ bitmap -> Bool -- ^ True <=> is a return point, rather than a function -> [FFIInfo] -> ProtoBCO name mkProtoBCO platform nm instrs_ordlist origin arity bitmap_size bitmap is_ret ffis = ProtoBCO { protoBCOName = nm, protoBCOInstrs = maybe_with_stack_check, protoBCOBitmap = bitmap, protoBCOBitmapSize = bitmap_size, protoBCOArity = arity, protoBCOExpr = origin, protoBCOFFIs = ffis } where -- Overestimate the stack usage (in words) of this BCO, -- and if >= iNTERP_STACK_CHECK_THRESH, add an explicit -- stack check. (The interpreter always does a stack check -- for iNTERP_STACK_CHECK_THRESH words at the start of each -- BCO anyway, so we only need to add an explicit one in the -- (hopefully rare) cases when the (overestimated) stack use -- exceeds iNTERP_STACK_CHECK_THRESH. maybe_with_stack_check | is_ret && stack_usage < fromIntegral (pc_AP_STACK_SPLIM (platformConstants platform)) = peep_d -- don't do stack checks at return points, -- everything is aggregated up to the top BCO -- (which must be a function). -- That is, unless the stack usage is >= AP_STACK_SPLIM, -- see bug #1466. | stack_usage >= fromIntegral iNTERP_STACK_CHECK_THRESH = STKCHECK stack_usage : peep_d | otherwise = peep_d -- the supposedly common case -- We assume that this sum doesn't wrap stack_usage = sum (map bciStackUse peep_d) -- Merge local pushes peep_d = peep (fromOL instrs_ordlist) peep (PUSH_L off1 : PUSH_L off2 : PUSH_L off3 : rest) = PUSH_LLL off1 (off2-1) (off3-2) : peep rest peep (PUSH_L off1 : PUSH_L off2 : rest) = PUSH_LL off1 (off2-1) : peep rest peep (i:rest) = i : peep rest peep [] = [] argBits :: Platform -> [ArgRep] -> [Bool] argBits _ [] = [] argBits platform (rep : args) | isFollowableArg rep = False : argBits platform args | otherwise = take (argRepSizeW platform rep) (repeat True) ++ argBits platform args non_void :: [ArgRep] -> [ArgRep] non_void = filter nv where nv V = False nv _ = True -- ----------------------------------------------------------------------------- -- schemeTopBind -- Compile code for the right-hand side of a top-level binding schemeTopBind :: (Id, CgStgRhs) -> BcM (ProtoBCO Name) schemeTopBind (id, rhs) | Just data_con <- isDataConWorkId_maybe id, isNullaryRepDataCon data_con = do platform <- profilePlatform <$> getProfile -- Special case for the worker of a nullary data con. -- It'll look like this: Nil = /\a -> Nil a -- If we feed it into schemeR, we'll get -- Nil = Nil -- because mkConAppCode treats nullary constructor applications -- by just re-using the single top-level definition. So -- for the worker itself, we must allocate it directly. -- ioToBc (putStrLn $ "top level BCO") let enter = if isUnliftedTypeKind (tyConResKind (dataConTyCon data_con)) then RETURN_UNLIFTED P else ENTER emitBc (mkProtoBCO platform (getName id) (toOL [PACK data_con 0, enter]) (Right rhs) 0 0 [{-no bitmap-}] False{-not alts-}) | otherwise = schemeR [{- No free variables -}] (getName id, rhs) -- ----------------------------------------------------------------------------- -- schemeR -- Compile code for a right-hand side, to give a BCO that, -- when executed with the free variables and arguments on top of the stack, -- will return with a pointer to the result on top of the stack, after -- removing the free variables and arguments. -- -- Park the resulting BCO in the monad. Also requires the -- name of the variable to which this value was bound, -- so as to give the resulting BCO a name. schemeR :: [Id] -- Free vars of the RHS, ordered as they -- will appear in the thunk. Empty for -- top-level things, which have no free vars. -> (Name, CgStgRhs) -> BcM (ProtoBCO Name) schemeR fvs (nm, rhs) = schemeR_wrk fvs nm rhs (collect rhs) -- If an expression is a lambda, return the -- list of arguments to the lambda (in R-to-L order) and the -- underlying expression collect :: CgStgRhs -> ([Var], CgStgExpr) collect (StgRhsClosure _ _ _ args body) = (args, body) collect (StgRhsCon _cc dc cnum _ticks args) = ([], StgConApp dc cnum args []) schemeR_wrk :: [Id] -> Name -> CgStgRhs -- expression e, for debugging only -> ([Var], CgStgExpr) -- result of collect on e -> BcM (ProtoBCO Name) schemeR_wrk fvs nm original_body (args, body) = do profile <- getProfile let platform = profilePlatform profile all_args = reverse args ++ fvs arity = length all_args -- all_args are the args in reverse order. We're compiling a function -- \fv1..fvn x1..xn -> e -- i.e. the fvs come first -- Stack arguments always take a whole number of words, we never pack -- them unlike constructor fields. szsb_args = map (wordsToBytes platform . idSizeW platform) all_args sum_szsb_args = sum szsb_args p_init = Map.fromList (zip all_args (mkStackOffsets 0 szsb_args)) -- make the arg bitmap bits = argBits platform (reverse (map (bcIdArgRep platform) all_args)) bitmap_size = genericLength bits bitmap = mkBitmap platform bits body_code <- schemeER_wrk sum_szsb_args p_init body emitBc (mkProtoBCO platform nm body_code (Right original_body) arity bitmap_size bitmap False{-not alts-}) -- introduce break instructions for ticked expressions schemeER_wrk :: StackDepth -> BCEnv -> CgStgExpr -> BcM BCInstrList schemeER_wrk d p (StgTick (Breakpoint tick_ty tick_no fvs) rhs) = do code <- schemeE d 0 p rhs cc_arr <- getCCArray this_mod <- moduleName <$> getCurrentModule platform <- profilePlatform <$> getProfile let idOffSets = getVarOffSets platform d p fvs let breakInfo = CgBreakInfo { cgb_vars = idOffSets , cgb_resty = tick_ty } newBreakInfo tick_no breakInfo hsc_env <- getHscEnv let cc | Just interp <- hsc_interp hsc_env , interpreterProfiled interp = cc_arr ! tick_no | otherwise = toRemotePtr nullPtr let breakInstr = BRK_FUN (fromIntegral tick_no) (getUnique this_mod) cc return $ breakInstr `consOL` code schemeER_wrk d p rhs = schemeE d 0 p rhs getVarOffSets :: Platform -> StackDepth -> BCEnv -> [Id] -> [Maybe (Id, Word16)] getVarOffSets platform depth env = map getOffSet where getOffSet id = case lookupBCEnv_maybe id env of Nothing -> Nothing Just offset -> -- michalt: I'm not entirely sure why we need the stack -- adjustment by 2 here. I initially thought that there's -- something off with getIdValFromApStack (the only user of this -- value), but it looks ok to me. My current hypothesis is that -- this "adjustment" is needed due to stack manipulation for -- BRK_FUN in Interpreter.c In any case, this is used only when -- we trigger a breakpoint. let !var_depth_ws = trunc16W $ bytesToWords platform (depth - offset) + 2 in Just (id, var_depth_ws) truncIntegral16 :: Integral a => a -> Word16 truncIntegral16 w | w > fromIntegral (maxBound :: Word16) = panic "stack depth overflow" | otherwise = fromIntegral w trunc16B :: ByteOff -> Word16 trunc16B = truncIntegral16 trunc16W :: WordOff -> Word16 trunc16W = truncIntegral16 fvsToEnv :: BCEnv -> CgStgRhs -> [Id] -- Takes the free variables of a right-hand side, and -- delivers an ordered list of the local variables that will -- be captured in the thunk for the RHS -- The BCEnv argument tells which variables are in the local -- environment: these are the ones that should be captured -- -- The code that constructs the thunk, and the code that executes -- it, have to agree about this layout fvsToEnv p rhs = [v | v <- dVarSetElems $ freeVarsOfRhs rhs, v `Map.member` p] -- ----------------------------------------------------------------------------- -- schemeE -- Returning an unlifted value. -- Heave it on the stack, SLIDE, and RETURN. returnUnliftedAtom :: StackDepth -> Sequel -> BCEnv -> StgArg -> BcM BCInstrList returnUnliftedAtom d s p e = do let reps = case e of StgLitArg lit -> typePrimRepArgs (literalType lit) StgVarArg i -> bcIdPrimReps i (push, szb) <- pushAtom d p e ret <- returnUnliftedReps d s szb reps return (push `appOL` ret) -- return an unlifted value from the top of the stack returnUnliftedReps :: StackDepth -> Sequel -> ByteOff -- size of the thing we're returning -> [PrimRep] -- representations -> BcM BCInstrList returnUnliftedReps d s szb reps = do profile <- getProfile let platform = profilePlatform profile non_void VoidRep = False non_void _ = True ret <- case filter non_void reps of -- use RETURN_UBX for unary representations [] -> return (unitOL $ RETURN_UNLIFTED V) [rep] -> return (unitOL $ RETURN_UNLIFTED (toArgRep platform rep)) -- otherwise use RETURN_TUPLE with a tuple descriptor nv_reps -> do let (tuple_info, args_offsets) = layoutTuple profile 0 (primRepCmmType platform) nv_reps args_ptrs = map (\(rep, off) -> (isFollowableArg (toArgRep platform rep), off)) args_offsets tuple_bco <- emitBc (tupleBCO platform tuple_info args_ptrs) return $ PUSH_UBX (mkTupleInfoLit platform tuple_info) 1 `consOL` PUSH_BCO tuple_bco `consOL` unitOL RETURN_TUPLE return ( mkSlideB platform szb (d - s) -- clear to sequel `appOL` ret) -- go -- construct and return an unboxed tuple returnUnboxedTuple :: StackDepth -> Sequel -> BCEnv -> [StgArg] -> BcM BCInstrList returnUnboxedTuple d s p es = do profile <- getProfile let platform = profilePlatform profile arg_ty e = primRepCmmType platform (atomPrimRep e) (tuple_info, tuple_components) = layoutTuple profile d arg_ty es go _ pushes [] = return (reverse pushes) go !dd pushes ((a, off):cs) = do (push, szb) <- pushAtom dd p a massert (off == dd + szb) go (dd + szb) (push:pushes) cs pushes <- go d [] tuple_components ret <- returnUnliftedReps d s (wordsToBytes platform $ tupleSize tuple_info) (map atomPrimRep es) return (mconcat pushes `appOL` ret) -- Compile code to apply the given expression to the remaining args -- on the stack, returning a HNF. schemeE :: StackDepth -> Sequel -> BCEnv -> CgStgExpr -> BcM BCInstrList schemeE d s p (StgLit lit) = returnUnliftedAtom d s p (StgLitArg lit) schemeE d s p (StgApp x []) | isUnliftedType (idType x) = returnUnliftedAtom d s p (StgVarArg x) -- Delegate tail-calls to schemeT. schemeE d s p e@(StgApp {}) = schemeT d s p e schemeE d s p e@(StgConApp {}) = schemeT d s p e schemeE d s p e@(StgOpApp {}) = schemeT d s p e schemeE d s p (StgLetNoEscape xlet bnd body) = schemeE d s p (StgLet xlet bnd body) schemeE d s p (StgLet _xlet (StgNonRec x (StgRhsCon _cc data_con _cnum _ticks args)) body) = do -- Special case for a non-recursive let whose RHS is a -- saturated constructor application. -- Just allocate the constructor and carry on alloc_code <- mkConAppCode d s p data_con args platform <- targetPlatform <$> getDynFlags let !d2 = d + wordSize platform body_code <- schemeE d2 s (Map.insert x d2 p) body return (alloc_code `appOL` body_code) -- General case for let. Generates correct, if inefficient, code in -- all situations. schemeE d s p (StgLet _ext binds body) = do platform <- targetPlatform <$> getDynFlags let (xs,rhss) = case binds of StgNonRec x rhs -> ([x],[rhs]) StgRec xs_n_rhss -> unzip xs_n_rhss n_binds = genericLength xs fvss = map (fvsToEnv p') rhss -- Sizes of free vars size_w = trunc16W . idSizeW platform sizes = map (\rhs_fvs -> sum (map size_w rhs_fvs)) fvss -- the arity of each rhs arities = map (genericLength . fst . collect) rhss -- This p', d' defn is safe because all the items being pushed -- are ptrs, so all have size 1 word. d' and p' reflect the stack -- after the closures have been allocated in the heap (but not -- filled in), and pointers to them parked on the stack. offsets = mkStackOffsets d (genericReplicate n_binds (wordSize platform)) p' = Map.insertList (zipE xs offsets) p d' = d + wordsToBytes platform n_binds zipE = zipEqual "schemeE" -- ToDo: don't build thunks for things with no free variables build_thunk :: StackDepth -> [Id] -> Word16 -> ProtoBCO Name -> Word16 -> Word16 -> BcM BCInstrList build_thunk _ [] size bco off arity = return (PUSH_BCO bco `consOL` unitOL (mkap (off+size) size)) where mkap | arity == 0 = MKAP | otherwise = MKPAP build_thunk dd (fv:fvs) size bco off arity = do (push_code, pushed_szb) <- pushAtom dd p' (StgVarArg fv) more_push_code <- build_thunk (dd + pushed_szb) fvs size bco off arity return (push_code `appOL` more_push_code) alloc_code = toOL (zipWith mkAlloc sizes arities) where mkAlloc sz 0 | is_tick = ALLOC_AP_NOUPD sz | otherwise = ALLOC_AP sz mkAlloc sz arity = ALLOC_PAP arity sz is_tick = case binds of StgNonRec id _ -> occNameFS (getOccName id) == tickFS _other -> False compile_bind d' fvs x (rhs::CgStgRhs) size arity off = do bco <- schemeR fvs (getName x,rhs) build_thunk d' fvs size bco off arity compile_binds = [ compile_bind d' fvs x rhs size arity (trunc16W n) | (fvs, x, rhs, size, arity, n) <- zip6 fvss xs rhss sizes arities [n_binds, n_binds-1 .. 1] ] body_code <- schemeE d' s p' body thunk_codes <- sequence compile_binds return (alloc_code `appOL` concatOL thunk_codes `appOL` body_code) schemeE _d _s _p (StgTick (Breakpoint _ bp_id _) _rhs) = panic ("schemeE: Breakpoint without let binding: " ++ show bp_id ++ " forgot to run bcPrep?") -- ignore other kinds of tick schemeE d s p (StgTick _ rhs) = schemeE d s p rhs -- no alts: scrut is guaranteed to diverge schemeE d s p (StgCase scrut _ _ []) = schemeE d s p scrut schemeE d s p (StgCase scrut bndr _ alts) = doCase d s p scrut bndr alts {- Ticked Expressions ------------------ The idea is that the "breakpoint E" is really just an annotation on the code. When we find such a thing, we pull out the useful information, and then compile the code as if it was just the expression E. -} -- Compile code to do a tail call. Specifically, push the fn, -- slide the on-stack app back down to the sequel depth, -- and enter. Four cases: -- -- 0. (Nasty hack). -- An application "GHC.Prim.tagToEnum# unboxed-int". -- The int will be on the stack. Generate a code sequence -- to convert it to the relevant constructor, SLIDE and ENTER. -- -- 1. The fn denotes a ccall. Defer to generateCCall. -- -- 2. An unboxed tuple: push the components on the top of -- the stack and return. -- -- 3. Application of a constructor, by defn saturated. -- Split the args into ptrs and non-ptrs, and push the nonptrs, -- then the ptrs, and then do PACK and RETURN. -- -- 4. Otherwise, it must be a function call. Push the args -- right to left, SLIDE and ENTER. schemeT :: StackDepth -- Stack depth -> Sequel -- Sequel depth -> BCEnv -- stack env -> CgStgExpr -> BcM BCInstrList -- Case 0 schemeT d s p app | Just (arg, constr_names) <- maybe_is_tagToEnum_call app = implement_tagToId d s p arg constr_names -- Case 1 schemeT d s p (StgOpApp (StgFCallOp (CCall ccall_spec) _ty) args result_ty) = if isSupportedCConv ccall_spec then generateCCall d s p ccall_spec result_ty (reverse args) else unsupportedCConvException schemeT d s p (StgOpApp (StgPrimOp op) args _ty) = doTailCall d s p (primOpId op) (reverse args) schemeT _d _s _p (StgOpApp StgPrimCallOp{} _args _ty) = unsupportedCConvException -- Case 2: Unboxed tuple schemeT d s p (StgConApp con _cn args _tys) | isUnboxedTupleDataCon con || isUnboxedSumDataCon con = returnUnboxedTuple d s p args -- Case 3: Ordinary data constructor | otherwise = do alloc_con <- mkConAppCode d s p con args platform <- profilePlatform <$> getProfile return (alloc_con `appOL` mkSlideW 1 (bytesToWords platform $ d - s) `snocOL` if isUnliftedTypeKind (tyConResKind (dataConTyCon con)) then RETURN_UNLIFTED P else ENTER) -- Case 4: Tail call of function schemeT d s p (StgApp fn args) = doTailCall d s p fn (reverse args) schemeT _ _ _ e = pprPanic "GHC.StgToByteCode.schemeT" (pprStgExpr shortStgPprOpts e) -- ----------------------------------------------------------------------------- -- Generate code to build a constructor application, -- leaving it on top of the stack mkConAppCode :: StackDepth -> Sequel -> BCEnv -> DataCon -- The data constructor -> [StgArg] -- Args, in *reverse* order -> BcM BCInstrList mkConAppCode orig_d _ p con args = app_code where app_code = do profile <- getProfile let platform = profilePlatform profile non_voids = [ NonVoid (prim_rep, arg) | arg <- args , let prim_rep = atomPrimRep arg , not (isVoidRep prim_rep) ] (_, _, args_offsets) = mkVirtHeapOffsetsWithPadding profile StdHeader non_voids do_pushery !d (arg : args) = do (push, arg_bytes) <- case arg of (Padding l _) -> return $! pushPadding (ByteOff l) (FieldOff a _) -> pushConstrAtom d p (fromNonVoid a) more_push_code <- do_pushery (d + arg_bytes) args return (push `appOL` more_push_code) do_pushery !d [] = do let !n_arg_words = trunc16W $ bytesToWords platform (d - orig_d) return (unitOL (PACK con n_arg_words)) -- Push on the stack in the reverse order. do_pushery orig_d (reverse args_offsets) -- ----------------------------------------------------------------------------- -- Generate code for a tail-call doTailCall :: StackDepth -> Sequel -> BCEnv -> Id -> [StgArg] -> BcM BCInstrList doTailCall init_d s p fn args = do platform <- profilePlatform <$> getProfile do_pushes init_d args (map (atomRep platform) args) where do_pushes !d [] reps = do assert (null reps) return () (push_fn, sz) <- pushAtom d p (StgVarArg fn) platform <- profilePlatform <$> getProfile assert (sz == wordSize platform) return () let slide = mkSlideB platform (d - init_d + wordSize platform) (init_d - s) enter = if isUnliftedType (idType fn) then RETURN_UNLIFTED P else ENTER return (push_fn `appOL` (slide `appOL` unitOL enter)) do_pushes !d args reps = do let (push_apply, n, rest_of_reps) = findPushSeq reps (these_args, rest_of_args) = splitAt n args (next_d, push_code) <- push_seq d these_args platform <- profilePlatform <$> getProfile instrs <- do_pushes (next_d + wordSize platform) rest_of_args rest_of_reps -- ^^^ for the PUSH_APPLY_ instruction return (push_code `appOL` (push_apply `consOL` instrs)) push_seq d [] = return (d, nilOL) push_seq d (arg:args) = do (push_code, sz) <- pushAtom d p arg (final_d, more_push_code) <- push_seq (d + sz) args return (final_d, push_code `appOL` more_push_code) -- v. similar to CgStackery.findMatch, ToDo: merge findPushSeq :: [ArgRep] -> (BCInstr, Int, [ArgRep]) findPushSeq (P: P: P: P: P: P: rest) = (PUSH_APPLY_PPPPPP, 6, rest) findPushSeq (P: P: P: P: P: rest) = (PUSH_APPLY_PPPPP, 5, rest) findPushSeq (P: P: P: P: rest) = (PUSH_APPLY_PPPP, 4, rest) findPushSeq (P: P: P: rest) = (PUSH_APPLY_PPP, 3, rest) findPushSeq (P: P: rest) = (PUSH_APPLY_PP, 2, rest) findPushSeq (P: rest) = (PUSH_APPLY_P, 1, rest) findPushSeq (V: rest) = (PUSH_APPLY_V, 1, rest) findPushSeq (N: rest) = (PUSH_APPLY_N, 1, rest) findPushSeq (F: rest) = (PUSH_APPLY_F, 1, rest) findPushSeq (D: rest) = (PUSH_APPLY_D, 1, rest) findPushSeq (L: rest) = (PUSH_APPLY_L, 1, rest) findPushSeq argReps | any (`elem` [V16, V32, V64]) argReps = sorry "SIMD vector operations are not available in GHCi" findPushSeq _ = panic "GHC.StgToByteCode.findPushSeq" -- ----------------------------------------------------------------------------- -- Case expressions doCase :: StackDepth -> Sequel -> BCEnv -> CgStgExpr -> Id -> [CgStgAlt] -> BcM BCInstrList doCase d s p scrut bndr alts = do profile <- getProfile hsc_env <- getHscEnv let platform = profilePlatform profile -- Are we dealing with an unboxed tuple with a tuple return frame? -- -- 'Simple' tuples with at most one non-void component, -- like (# Word# #) or (# Int#, State# RealWorld# #) do not have a -- tuple return frame. This is because (# foo #) and (# foo, Void# #) -- have the same runtime rep. We have more efficient specialized -- return frames for the situations with one non-void element. ubx_tuple_frame = (isUnboxedTupleType bndr_ty || isUnboxedSumType bndr_ty) && length non_void_arg_reps > 1 unlifted_alg_ty = isUnliftedType bndr_ty && isAlgCase non_void_arg_reps = non_void (typeArgReps platform bndr_ty) profiling | Just interp <- hsc_interp hsc_env = interpreterProfiled interp | otherwise = False -- Top of stack is the return itbl, as usual. -- underneath it is the pointer to the alt_code BCO. -- When an alt is entered, it assumes the returned value is -- on top of the itbl. ret_frame_size_b :: StackDepth ret_frame_size_b | ubx_tuple_frame = (if profiling then 5 else 4) * wordSize platform | otherwise = 2 * wordSize platform -- The stack space used to save/restore the CCCS when profiling save_ccs_size_b | profiling && not ubx_tuple_frame = 2 * wordSize platform | otherwise = 0 -- The size of the return frame info table pointer if one exists unlifted_itbl_size_b :: StackDepth unlifted_itbl_size_b | ubx_tuple_frame = wordSize platform | not (isUnliftedType bndr_ty) -- See Note [Popping return frame for unlifted things] || unlifted_alg_ty = 0 | otherwise = wordSize platform (bndr_size, tuple_info, args_offsets) | ubx_tuple_frame = let bndr_ty = primRepCmmType platform bndr_reps = filter (not.isVoidRep) (bcIdPrimReps bndr) (tuple_info, args_offsets) = layoutTuple profile 0 bndr_ty bndr_reps in ( wordsToBytes platform (tupleSize tuple_info) , tuple_info , args_offsets ) | otherwise = ( wordsToBytes platform (idSizeW platform bndr) , voidTupleInfo , [] ) -- depth of stack after the return value has been pushed d_bndr = d + ret_frame_size_b + bndr_size -- depth of stack after the extra info table for an unlifted return -- has been pushed, if any. This is the stack depth at the -- continuation. d_alts = d + ret_frame_size_b + bndr_size + unlifted_itbl_size_b -- Env in which to compile the alts, not including -- any vars bound by the alts themselves p_alts = Map.insert bndr d_bndr p bndr_ty = idType bndr isAlgCase = isAlgType bndr_ty -- given an alt, return a discr and code for it. codeAlt :: CgStgAlt -> BcM (Discr, BCInstrList) codeAlt GenStgAlt{alt_con=DEFAULT,alt_bndrs=_,alt_rhs=rhs} = do rhs_code <- schemeE d_alts s p_alts rhs return (NoDiscr, rhs_code) codeAlt alt@GenStgAlt{alt_con=_, alt_bndrs=bndrs, alt_rhs=rhs} -- primitive or nullary constructor alt: no need to UNPACK | null real_bndrs = do rhs_code <- schemeE d_alts s p_alts rhs return (my_discr alt, rhs_code) | isUnboxedTupleType bndr_ty || isUnboxedSumType bndr_ty = let bndr_ty = primRepCmmType platform . bcIdPrimRep tuple_start = d_bndr (tuple_info, args_offsets) = layoutTuple profile 0 bndr_ty bndrs stack_bot = d_alts p' = Map.insertList [ (arg, tuple_start - wordsToBytes platform (tupleSize tuple_info) + offset) | (arg, offset) <- args_offsets , not (isVoidRep $ bcIdPrimRep arg)] p_alts in do rhs_code <- schemeE stack_bot s p' rhs return (NoDiscr, rhs_code) -- algebraic alt with some binders | otherwise = let (tot_wds, _ptrs_wds, args_offsets) = mkVirtHeapOffsets profile NoHeader [ NonVoid (bcIdPrimRep id, id) | NonVoid id <- nonVoidIds real_bndrs ] size = WordOff tot_wds stack_bot = d_alts + wordsToBytes platform size -- convert offsets from Sp into offsets into the virtual stack p' = Map.insertList [ (arg, stack_bot - ByteOff offset) | (NonVoid arg, offset) <- args_offsets ] p_alts in do massert isAlgCase rhs_code <- schemeE stack_bot s p' rhs return (my_discr alt, unitOL (UNPACK (trunc16W size)) `appOL` rhs_code) where real_bndrs = filterOut isTyVar bndrs my_discr alt = case alt_con alt of DEFAULT -> NoDiscr {-shouldn't really happen-} DataAlt dc | isUnboxedTupleDataCon dc || isUnboxedSumDataCon dc -> NoDiscr | otherwise -> DiscrP (fromIntegral (dataConTag dc - fIRST_TAG)) LitAlt l -> case l of LitNumber LitNumInt i -> DiscrI (fromInteger i) LitNumber LitNumWord w -> DiscrW (fromInteger w) LitFloat r -> DiscrF (fromRational r) LitDouble r -> DiscrD (fromRational r) LitChar i -> DiscrI (ord i) _ -> pprPanic "schemeE(StgCase).my_discr" (ppr l) maybe_ncons | not isAlgCase = Nothing | otherwise = case [dc | DataAlt dc <- alt_con <$> alts] of [] -> Nothing (dc:_) -> Just (tyConFamilySize (dataConTyCon dc)) -- the bitmap is relative to stack depth d, i.e. before the -- BCO, info table and return value are pushed on. -- This bit of code is v. similar to buildLivenessMask in CgBindery, -- except that here we build the bitmap from the known bindings of -- things that are pointers, whereas in CgBindery the code builds the -- bitmap from the free slots and unboxed bindings. -- (ToDo: merge?) -- -- NOTE [7/12/2006] bug #1013, testcase ghci/should_run/ghci002. -- The bitmap must cover the portion of the stack up to the sequel only. -- Previously we were building a bitmap for the whole depth (d), but we -- really want a bitmap up to depth (d-s). This affects compilation of -- case-of-case expressions, which is the only time we can be compiling a -- case expression with s /= 0. -- unboxed tuples get two more words, the second is a pointer (tuple_bco) (extra_pointers, extra_slots) | ubx_tuple_frame && profiling = ([1], 3) -- tuple_info, tuple_BCO, CCCS | ubx_tuple_frame = ([1], 2) -- tuple_info, tuple_BCO | otherwise = ([], 0) bitmap_size = trunc16W $ fromIntegral extra_slots + bytesToWords platform (d - s) bitmap_size' :: Int bitmap_size' = fromIntegral bitmap_size pointers = extra_pointers ++ filter (< bitmap_size') (map (+extra_slots) rel_slots) where -- NB: unboxed tuple cases bind the scrut binder to the same offset -- as one of the alt binders, so we have to remove any duplicates here: -- 'toAscList' takes care of sorting the result, which was previously done after the application of 'filter'. rel_slots = IntSet.toAscList $ IntSet.fromList $ Map.elems $ Map.mapMaybeWithKey spread p spread id offset | isUnboxedTupleType (idType id) || isUnboxedSumType (idType id) = Nothing | isFollowableArg (bcIdArgRep platform id) = Just (fromIntegral rel_offset) | otherwise = Nothing where rel_offset = trunc16W $ bytesToWords platform (d - offset) bitmap = intsToReverseBitmap platform bitmap_size'{-size-} pointers alt_stuff <- mapM codeAlt alts alt_final0 <- mkMultiBranch maybe_ncons alt_stuff -- Note [Popping return frame for unlifted things] -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -- When an unlifted value is returned, a special stg_ret_XXX_info frame will -- be sitting on top of the stack. This mechanism is used to aid in switching -- execution contexts between object code and interpreter. However, mkMultiBranch, -- which produces the bytecode to discriminate the case alternatives, does not -- account for that frame header and does branching based on the top of the stack. -- Therefore, we must compensate for this by popping the frame header (2 words -- for tuples and 1 word for other unlifted things) before passing control to -- the case discrimination continuation. This ensures we are looking at the -- right word and it also saves some stack space. Failing to account for this -- was the cause of #20194. let alt_final | ubx_tuple_frame = mkSlideW 0 2 `mappend` alt_final0 | unlifted_alg_ty = mkSlideW 0 1 `mappend` alt_final0 | otherwise = alt_final0 let alt_bco_name = getName bndr alt_bco = mkProtoBCO platform alt_bco_name alt_final (Left alts) 0{-no arity-} bitmap_size bitmap True{-is alts-} scrut_code <- schemeE (d + ret_frame_size_b + save_ccs_size_b) (d + ret_frame_size_b + save_ccs_size_b) p scrut alt_bco' <- emitBc alt_bco if ubx_tuple_frame then do let args_ptrs = map (\(rep, off) -> (isFollowableArg (toArgRep platform rep), off)) args_offsets tuple_bco <- emitBc (tupleBCO platform tuple_info args_ptrs) return (PUSH_ALTS_TUPLE alt_bco' tuple_info tuple_bco `consOL` scrut_code) else let push_alts | not (isUnliftedType bndr_ty) = PUSH_ALTS alt_bco' | otherwise = let unlifted_rep = case non_void_arg_reps of [] -> V [rep] -> rep _ -> panic "schemeE(StgCase).push_alts" in PUSH_ALTS_UNLIFTED alt_bco' unlifted_rep in return (push_alts `consOL` scrut_code) -- ----------------------------------------------------------------------------- -- Deal with tuples -- The native calling convention uses registers for tuples, but in the -- bytecode interpreter, all values live on the stack. layoutTuple :: Profile -> ByteOff -> (a -> CmmType) -> [a] -> ( TupleInfo -- See Note [GHCi TupleInfo] , [(a, ByteOff)] -- argument, offset on stack ) layoutTuple profile start_off arg_ty reps = let platform = profilePlatform profile (orig_stk_bytes, pos) = assignArgumentsPos profile 0 NativeReturn arg_ty reps -- keep the stack parameters in the same place orig_stk_params = [(x, fromIntegral off) | (x, StackParam off) <- pos] -- sort the register parameters by register and add them to the stack regs_order :: Map.Map GlobalReg Int regs_order = Map.fromList $ zip (tupleRegsCover platform) [0..] reg_order :: GlobalReg -> (Int, GlobalReg) reg_order reg | Just n <- Map.lookup reg regs_order = (n, reg) -- a VanillaReg goes to the same place regardless of whether it -- contains a pointer reg_order (VanillaReg n VNonGcPtr) = reg_order (VanillaReg n VGcPtr) -- if we don't have a position for a FloatReg then they must be passed -- in the equivalent DoubleReg reg_order (FloatReg n) = reg_order (DoubleReg n) -- one-tuples can be passed in other registers, but then we don't need -- to care about the order reg_order reg = (0, reg) (regs, reg_params) = unzip $ sortBy (comparing fst) [(reg_order reg, x) | (x, RegisterParam reg) <- pos] (new_stk_bytes, new_stk_params) = assignStack platform orig_stk_bytes arg_ty reg_params regs_set = mkRegSet (map snd regs) get_byte_off (x, StackParam y) = (x, fromIntegral y) get_byte_off _ = panic "GHC.StgToByteCode.layoutTuple get_byte_off" in ( TupleInfo { tupleSize = bytesToWords platform (ByteOff new_stk_bytes) , tupleRegs = regs_set , tupleNativeStackSize = bytesToWords platform (ByteOff orig_stk_bytes) } , sortBy (comparing snd) $ map (\(x, o) -> (x, o + start_off)) (orig_stk_params ++ map get_byte_off new_stk_params) ) {- Note [unboxed tuple bytecodes and tuple_BCO] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ We have the bytecode instructions RETURN_TUPLE and PUSH_ALTS_TUPLE to return and receive arbitrary unboxed tuples, respectively. These instructions use the helper data tuple_BCO and tuple_info. The helper data is used to convert tuples between GHCs native calling convention (object code), which uses stack and registers, and the bytecode calling convention, which only uses the stack. See Note [GHCi TupleInfo] for more details. Returning a tuple ================= Bytecode that returns a tuple first pushes all the tuple fields followed by the appropriate tuple_info and tuple_BCO onto the stack. It then executes the RETURN_TUPLE instruction, which causes the interpreter to push stg_ret_t_info to the top of the stack. The stack (growing down) then looks as follows: ... next_frame tuple_field_1 tuple_field_2 ... tuple_field_n tuple_info tuple_BCO stg_ret_t_info <- Sp If next_frame is bytecode, the interpreter will start executing it. If it's object code, the interpreter jumps back to the scheduler, which in turn jumps to stg_ret_t. stg_ret_t converts the tuple to the native calling convention using the description in tuple_info, and then jumps to next_frame. Receiving a tuple ================= Bytecode that receives a tuple uses the PUSH_ALTS_TUPLE instruction to push a continuation, followed by jumping to the code that produces the tuple. The PUSH_ALTS_TUPLE instuction contains three pieces of data: * cont_BCO: the continuation that receives the tuple * tuple_info: see below * tuple_BCO: see below The interpreter pushes these onto the stack when the PUSH_ALTS_TUPLE instruction is executed, followed by stg_ctoi_tN_info, with N depending on the number of stack words used by the tuple in the GHC native calling convention. N is derived from tuple_info. For example if we expect a tuple with three words on the stack, the stack looks as follows after PUSH_ALTS_TUPLE: ... next_frame cont_free_var_1 cont_free_var_2 ... cont_free_var_n tuple_info tuple_BCO cont_BCO stg_ctoi_t3_info <- Sp If the tuple is returned by object code, stg_ctoi_t3 will deal with adjusting the stack pointer and converting the tuple to the bytecode calling convention. See Note [GHCi unboxed tuples stack spills] for more details. The tuple_BCO ============= The tuple_BCO is a helper bytecode object. Its main purpose is describing the contents of the stack frame containing the tuple for the storage manager. It contains only instructions to immediately return the tuple that is already on the stack. The tuple_info word =================== The tuple_info word describes the stack and STG register (e.g. R1..R6, D1..D6) usage for the tuple. tuple_info contains enough information to convert the tuple between the stack-only bytecode and stack+registers GHC native calling conventions. See Note [GHCi tuple layout] for more details of how the data is packed in a single word. -} tupleBCO :: Platform -> TupleInfo -> [(Bool, ByteOff)] -> [FFIInfo] -> ProtoBCO Name tupleBCO platform info pointers = mkProtoBCO platform invented_name body_code (Left []) 0{-no arity-} bitmap_size bitmap False{-is alts-} where {- The tuple BCO is never referred to by name, so we can get away with using a fake name here. We will need to change this if we want to save some memory by sharing the BCO between places that have the same tuple shape -} invented_name = mkSystemVarName (mkPseudoUniqueE 0) (fsLit "tuple") -- the first word in the frame is the tuple_info word, -- which is not a pointer bitmap_size = trunc16W $ 1 + tupleSize info bitmap = intsToReverseBitmap platform (fromIntegral bitmap_size) $ map ((+1) . fromIntegral . bytesToWords platform . snd) (filter fst pointers) body_code = mkSlideW 0 1 -- pop frame header `snocOL` RETURN_TUPLE -- and add it again -- ----------------------------------------------------------------------------- -- Deal with a CCall. -- Taggedly push the args onto the stack R->L, -- deferencing ForeignObj#s and adjusting addrs to point to -- payloads in Ptr/Byte arrays. Then, generate the marshalling -- (machine) code for the ccall, and create bytecodes to call that and -- then return in the right way. generateCCall :: StackDepth -> Sequel -> BCEnv -> CCallSpec -- where to call -> Type -> [StgArg] -- args (atoms) -> BcM BCInstrList generateCCall d0 s p (CCallSpec target cconv safety) result_ty args_r_to_l = do profile <- getProfile let platform = profilePlatform profile -- useful constants addr_size_b :: ByteOff addr_size_b = wordSize platform arrayish_rep_hdr_size :: TyCon -> Maybe Int arrayish_rep_hdr_size t | t == arrayPrimTyCon || t == mutableArrayPrimTyCon = Just (arrPtrsHdrSize profile) | t == smallArrayPrimTyCon || t == smallMutableArrayPrimTyCon = Just (smallArrPtrsHdrSize profile) | t == byteArrayPrimTyCon || t == mutableByteArrayPrimTyCon = Just (arrWordsHdrSize profile) | otherwise = Nothing -- Get the args on the stack, with tags and suitably -- dereferenced for the CCall. For each arg, return the -- depth to the first word of the bits for that arg, and the -- ArgRep of what was actually pushed. pargs :: ByteOff -> [StgArg] -> BcM [(BCInstrList, PrimRep)] pargs _ [] = return [] pargs d (aa@(StgVarArg a):az) | Just t <- tyConAppTyCon_maybe (idType a) , Just hdr_sz <- arrayish_rep_hdr_size t -- Do magic for Ptr/Byte arrays. Push a ptr to the array on -- the stack but then advance it over the headers, so as to -- point to the payload. = do rest <- pargs (d + addr_size_b) az (push_fo, _) <- pushAtom d p aa -- The ptr points at the header. Advance it over the -- header and then pretend this is an Addr#. let code = push_fo `snocOL` SWIZZLE 0 (fromIntegral hdr_sz) return ((code, AddrRep) : rest) pargs d (aa:az) = do (code_a, sz_a) <- pushAtom d p aa rest <- pargs (d + sz_a) az return ((code_a, atomPrimRep aa) : rest) code_n_reps <- pargs d0 args_r_to_l let (pushs_arg, a_reps_pushed_r_to_l) = unzip code_n_reps a_reps_sizeW = sum (map (repSizeWords platform) a_reps_pushed_r_to_l) push_args = concatOL pushs_arg !d_after_args = d0 + wordsToBytes platform a_reps_sizeW a_reps_pushed_RAW | null a_reps_pushed_r_to_l || not (isVoidRep (head a_reps_pushed_r_to_l)) = panic "GHC.StgToByteCode.generateCCall: missing or invalid World token?" | otherwise = reverse (tail a_reps_pushed_r_to_l) -- Now: a_reps_pushed_RAW are the reps which are actually on the stack. -- push_args is the code to do that. -- d_after_args is the stack depth once the args are on. -- Get the result rep. (returns_void, r_rep) = case maybe_getCCallReturnRep result_ty of Nothing -> (True, VoidRep) Just rr -> (False, rr) {- Because the Haskell stack grows down, the a_reps refer to lowest to highest addresses in that order. The args for the call are on the stack. Now push an unboxed Addr# indicating the C function to call. Then push a dummy placeholder for the result. Finally, emit a CCALL insn with an offset pointing to the Addr# just pushed, and a literal field holding the mallocville address of the piece of marshalling code we generate. So, just prior to the CCALL insn, the stack looks like this (growing down, as usual): ... Addr# address_of_C_fn (must be an unboxed type) The interpreter then calls the marshall code mentioned in the CCALL insn, passing it (& ), that is, the addr of the topmost word in the stack. When this returns, the placeholder will have been filled in. The placeholder is slid down to the sequel depth, and we RETURN. This arrangement makes it simple to do f-i-dynamic since the Addr# value is the first arg anyway. The marshalling code is generated specifically for this call site, and so knows exactly the (Haskell) stack offsets of the args, fn address and placeholder. It copies the args to the C stack, calls the stacked addr, and parks the result back in the placeholder. The interpreter calls it as a normal C call, assuming it has a signature void marshall_code ( StgWord* ptr_to_top_of_stack ) -} -- resolve static address maybe_static_target :: Maybe Literal maybe_static_target = case target of DynamicTarget -> Nothing StaticTarget _ _ _ False -> panic "generateCCall: unexpected FFI value import" StaticTarget _ target _ True -> Just (LitLabel target mb_size IsFunction) where mb_size | OSMinGW32 <- platformOS platform , StdCallConv <- cconv = Just (fromIntegral a_reps_sizeW * platformWordSizeInBytes platform) | otherwise = Nothing let is_static = isJust maybe_static_target -- Get the arg reps, zapping the leading Addr# in the dynamic case a_reps -- | trace (showSDoc (ppr a_reps_pushed_RAW)) False = error "???" | is_static = a_reps_pushed_RAW | otherwise = if null a_reps_pushed_RAW then panic "GHC.StgToByteCode.generateCCall: dyn with no args" else tail a_reps_pushed_RAW -- push the Addr# (push_Addr, d_after_Addr) | Just machlabel <- maybe_static_target = (toOL [PUSH_UBX machlabel 1], d_after_args + addr_size_b) | otherwise -- is already on the stack = (nilOL, d_after_args) -- Push the return placeholder. For a call returning nothing, -- this is a V (tag). r_sizeW = repSizeWords platform r_rep d_after_r = d_after_Addr + wordsToBytes platform r_sizeW push_r = if returns_void then nilOL else unitOL (PUSH_UBX (mkDummyLiteral platform r_rep) (trunc16W r_sizeW)) -- generate the marshalling code we're going to call -- Offset of the next stack frame down the stack. The CCALL -- instruction needs to describe the chunk of stack containing -- the ccall args to the GC, so it needs to know how large it -- is. See comment in Interpreter.c with the CCALL instruction. stk_offset = trunc16W $ bytesToWords platform (d_after_r - s) conv = case cconv of CCallConv -> FFICCall CApiConv -> FFICCall StdCallConv -> FFIStdCall _ -> panic "GHC.StgToByteCode: unexpected calling convention" -- the only difference in libffi mode is that we prepare a cif -- describing the call type by calling libffi, and we attach the -- address of this to the CCALL instruction. let ffires = primRepToFFIType platform r_rep ffiargs = map (primRepToFFIType platform) a_reps interp <- hscInterp <$> getHscEnv token <- ioToBc $ interpCmd interp (PrepFFI conv ffiargs ffires) recordFFIBc token let -- do the call do_call = unitOL (CCALL stk_offset token flags) where flags = case safety of PlaySafe -> 0x0 PlayInterruptible -> 0x1 PlayRisky -> 0x2 -- slide and return d_after_r_min_s = bytesToWords platform (d_after_r - s) wrapup = mkSlideW (trunc16W r_sizeW) (d_after_r_min_s - r_sizeW) `snocOL` RETURN_UNLIFTED (toArgRep platform r_rep) --trace (show (arg1_offW, args_offW , (map argRepSizeW a_reps) )) $ return ( push_args `appOL` push_Addr `appOL` push_r `appOL` do_call `appOL` wrapup ) primRepToFFIType :: Platform -> PrimRep -> FFIType primRepToFFIType platform r = case r of VoidRep -> FFIVoid IntRep -> signed_word WordRep -> unsigned_word Int8Rep -> FFISInt8 Word8Rep -> FFIUInt8 Int16Rep -> FFISInt16 Word16Rep -> FFIUInt16 Int32Rep -> FFISInt32 Word32Rep -> FFIUInt32 Int64Rep -> FFISInt64 Word64Rep -> FFIUInt64 AddrRep -> FFIPointer FloatRep -> FFIFloat DoubleRep -> FFIDouble LiftedRep -> FFIPointer UnliftedRep -> FFIPointer _ -> pprPanic "primRepToFFIType" (ppr r) where (signed_word, unsigned_word) = case platformWordSize platform of PW4 -> (FFISInt32, FFIUInt32) PW8 -> (FFISInt64, FFIUInt64) -- Make a dummy literal, to be used as a placeholder for FFI return -- values on the stack. mkDummyLiteral :: Platform -> PrimRep -> Literal mkDummyLiteral platform pr = case pr of IntRep -> mkLitInt platform 0 WordRep -> mkLitWord platform 0 Int8Rep -> mkLitInt8 0 Word8Rep -> mkLitWord8 0 Int16Rep -> mkLitInt16 0 Word16Rep -> mkLitWord16 0 Int32Rep -> mkLitInt32 0 Word32Rep -> mkLitWord32 0 Int64Rep -> mkLitInt64 0 Word64Rep -> mkLitWord64 0 AddrRep -> LitNullAddr DoubleRep -> LitDouble 0 FloatRep -> LitFloat 0 LiftedRep -> LitNullAddr UnliftedRep -> LitNullAddr _ -> pprPanic "mkDummyLiteral" (ppr pr) -- Convert (eg) -- GHC.Prim.Char# -> GHC.Prim.State# GHC.Prim.RealWorld -- -> (# GHC.Prim.State# GHC.Prim.RealWorld, GHC.Prim.Int# #) -- -- to Just IntRep -- and check that an unboxed pair is returned wherein the first arg is V'd. -- -- Alternatively, for call-targets returning nothing, convert -- -- GHC.Prim.Char# -> GHC.Prim.State# GHC.Prim.RealWorld -- -> (# GHC.Prim.State# GHC.Prim.RealWorld #) -- -- to Nothing maybe_getCCallReturnRep :: Type -> Maybe PrimRep maybe_getCCallReturnRep fn_ty = let (_a_tys, r_ty) = splitFunTys (dropForAlls fn_ty) r_reps = typePrimRepArgs r_ty blargh :: a -- Used at more than one type blargh = pprPanic "maybe_getCCallReturn: can't handle:" (pprType fn_ty) in case r_reps of [] -> panic "empty typePrimRepArgs" [VoidRep] -> Nothing [rep] -> Just rep -- if it was, it would be impossible to create a -- valid return value placeholder on the stack _ -> blargh maybe_is_tagToEnum_call :: CgStgExpr -> Maybe (Id, [Name]) -- Detect and extract relevant info for the tagToEnum kludge. maybe_is_tagToEnum_call (StgOpApp (StgPrimOp TagToEnumOp) [StgVarArg v] t) = Just (v, extract_constr_Names t) where extract_constr_Names ty | rep_ty <- unwrapType ty , Just tyc <- tyConAppTyCon_maybe rep_ty , isDataTyCon tyc = map (getName . dataConWorkId) (tyConDataCons tyc) -- NOTE: use the worker name, not the source name of -- the DataCon. See "GHC.Core.DataCon" for details. | otherwise = pprPanic "maybe_is_tagToEnum_call.extract_constr_Ids" (ppr ty) maybe_is_tagToEnum_call _ = Nothing {- ----------------------------------------------------------------------------- Note [Implementing tagToEnum#] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ (implement_tagToId arg names) compiles code which takes an argument 'arg', (call it i), and enters the i'th closure in the supplied list as a consequence. The [Name] is a list of the constructors of this (enumeration) type. The code we generate is this: push arg push bogus-word TESTEQ_I 0 L1 PUSH_G JMP L_Exit L1: TESTEQ_I 1 L2 PUSH_G JMP L_Exit ...etc... Ln: TESTEQ_I n L_fail PUSH_G JMP L_Exit L_fail: CASEFAIL L_exit: SLIDE 1 n ENTER The 'bogus-word' push is because TESTEQ_I expects the top of the stack to have an info-table, and the next word to have the value to be tested. This is very weird, but it's the way it is right now. See Interpreter.c. We don't actually need an info-table here; we just need to have the argument to be one-from-top on the stack, hence pushing a 1-word null. See #8383. -} implement_tagToId :: StackDepth -> Sequel -> BCEnv -> Id -> [Name] -> BcM BCInstrList -- See Note [Implementing tagToEnum#] implement_tagToId d s p arg names = assert (notNull names) $ do (push_arg, arg_bytes) <- pushAtom d p (StgVarArg arg) labels <- getLabelsBc (genericLength names) label_fail <- getLabelBc label_exit <- getLabelBc dflags <- getDynFlags let infos = zip4 labels (tail labels ++ [label_fail]) [0 ..] names platform = targetPlatform dflags steps = map (mkStep label_exit) infos slide_ws = bytesToWords platform (d - s + arg_bytes) return (push_arg `appOL` unitOL (PUSH_UBX LitNullAddr 1) -- Push bogus word (see Note [Implementing tagToEnum#]) `appOL` concatOL steps `appOL` toOL [ LABEL label_fail, CASEFAIL, LABEL label_exit ] `appOL` mkSlideW 1 (slide_ws + 1) -- "+1" to account for bogus word -- (see Note [Implementing tagToEnum#]) `appOL` unitOL ENTER) where mkStep l_exit (my_label, next_label, n, name_for_n) = toOL [LABEL my_label, TESTEQ_I n next_label, PUSH_G name_for_n, JMP l_exit] -- ----------------------------------------------------------------------------- -- pushAtom -- Push an atom onto the stack, returning suitable code & number of -- stack words used. -- -- The env p must map each variable to the highest- numbered stack -- slot for it. For example, if the stack has depth 4 and we -- tagged-ly push (v :: Int#) on it, the value will be in stack[4], -- the tag in stack[5], the stack will have depth 6, and p must map v -- to 5 and not to 4. Stack locations are numbered from zero, so a -- depth 6 stack has valid words 0 .. 5. pushAtom :: StackDepth -> BCEnv -> StgArg -> BcM (BCInstrList, ByteOff) -- See Note [Empty case alternatives] in GHC.Core -- and Note [Bottoming expressions] in GHC.Core.Utils: -- The scrutinee of an empty case evaluates to bottom pushAtom d p (StgVarArg var) | [] <- typePrimRep (idType var) = return (nilOL, 0) | isFCallId var = pprPanic "pushAtom: shouldn't get an FCallId here" (ppr var) | Just primop <- isPrimOpId_maybe var = do platform <- targetPlatform <$> getDynFlags return (unitOL (PUSH_PRIMOP primop), wordSize platform) | Just d_v <- lookupBCEnv_maybe var p -- var is a local variable = do platform <- targetPlatform <$> getDynFlags let !szb = idSizeCon platform var with_instr instr = do let !off_b = trunc16B $ d - d_v return (unitOL (instr off_b), wordSize platform) case szb of 1 -> with_instr PUSH8_W 2 -> with_instr PUSH16_W 4 -> with_instr PUSH32_W _ -> do let !szw = bytesToWords platform szb !off_w = trunc16W $ bytesToWords platform (d - d_v) + szw - 1 return (toOL (genericReplicate szw (PUSH_L off_w)), wordsToBytes platform szw) -- d - d_v offset from TOS to the first slot of the object -- -- d - d_v + sz - 1 offset from the TOS of the last slot of the object -- -- Having found the last slot, we proceed to copy the right number of -- slots on to the top of the stack. | otherwise -- var must be a global variable = do topStrings <- getTopStrings platform <- targetPlatform <$> getDynFlags case lookupVarEnv topStrings var of Just ptr -> pushAtom d p $ StgLitArg $ mkLitWord platform $ fromIntegral $ ptrToWordPtr $ fromRemotePtr ptr Nothing -> do let sz = idSizeCon platform var massert (sz == wordSize platform) return (unitOL (PUSH_G (getName var)), sz) pushAtom _ _ (StgLitArg lit) = pushLiteral True lit pushLiteral :: Bool -> Literal -> BcM (BCInstrList, ByteOff) pushLiteral padded lit = do platform <- targetPlatform <$> getDynFlags let code :: PrimRep -> BcM (BCInstrList, ByteOff) code rep = return (padding_instr `snocOL` instr, size_bytes + padding_bytes) where size_bytes = ByteOff $ primRepSizeB platform rep -- Here we handle the non-word-width cases specifically since we -- must emit different bytecode for them. round_to_words (ByteOff bytes) = ByteOff (roundUpToWords platform bytes) padding_bytes | padded = round_to_words size_bytes - size_bytes | otherwise = 0 (padding_instr, _) = pushPadding padding_bytes instr = case size_bytes of 1 -> PUSH_UBX8 lit 2 -> PUSH_UBX16 lit 4 -> PUSH_UBX32 lit _ -> PUSH_UBX lit (trunc16W $ bytesToWords platform size_bytes) case lit of LitLabel {} -> code AddrRep LitFloat {} -> code FloatRep LitDouble {} -> code DoubleRep LitChar {} -> code WordRep LitNullAddr -> code AddrRep LitString {} -> code AddrRep LitRubbish {} -> code WordRep LitNumber nt _ -> case nt of LitNumInt -> code IntRep LitNumWord -> code WordRep LitNumInt8 -> code Int8Rep LitNumWord8 -> code Word8Rep LitNumInt16 -> code Int16Rep LitNumWord16 -> code Word16Rep LitNumInt32 -> code Int32Rep LitNumWord32 -> code Word32Rep LitNumInt64 -> code Int64Rep LitNumWord64 -> code Word64Rep -- No LitNumBigNat should be left by the time this is called. CorePrep -- should have converted them all to a real core representation. LitNumBigNat -> panic "pushAtom: LitNumBigNat" -- | Push an atom for constructor (i.e., PACK instruction) onto the stack. -- This is slightly different to @pushAtom@ due to the fact that we allow -- packing constructor fields. See also @mkConAppCode@ and @pushPadding@. pushConstrAtom :: StackDepth -> BCEnv -> StgArg -> BcM (BCInstrList, ByteOff) pushConstrAtom _ _ (StgLitArg lit) = pushLiteral False lit pushConstrAtom d p va@(StgVarArg v) | Just d_v <- lookupBCEnv_maybe v p = do -- v is a local variable platform <- targetPlatform <$> getDynFlags let !szb = idSizeCon platform v done instr = do let !off = trunc16B $ d - d_v return (unitOL (instr off), szb) case szb of 1 -> done PUSH8 2 -> done PUSH16 4 -> done PUSH32 _ -> pushAtom d p va pushConstrAtom d p expr = pushAtom d p expr pushPadding :: ByteOff -> (BCInstrList, ByteOff) pushPadding (ByteOff n) = go n (nilOL, 0) where go n acc@(!instrs, !off) = case n of 0 -> acc 1 -> (instrs `mappend` unitOL PUSH_PAD8, off + 1) 2 -> (instrs `mappend` unitOL PUSH_PAD16, off + 2) 3 -> go 1 (go 2 acc) 4 -> (instrs `mappend` unitOL PUSH_PAD32, off + 4) _ -> go (n - 4) (go 4 acc) -- ----------------------------------------------------------------------------- -- Given a bunch of alts code and their discrs, do the donkey work -- of making a multiway branch using a switch tree. -- What a load of hassle! mkMultiBranch :: Maybe Int -- # datacons in tycon, if alg alt -- a hint; generates better code -- Nothing is always safe -> [(Discr, BCInstrList)] -> BcM BCInstrList mkMultiBranch maybe_ncons raw_ways = do lbl_default <- getLabelBc let mkTree :: [(Discr, BCInstrList)] -> Discr -> Discr -> BcM BCInstrList mkTree [] _range_lo _range_hi = return (unitOL (JMP lbl_default)) -- shouldn't happen? mkTree [val] range_lo range_hi | range_lo == range_hi = return (snd val) | null defaults -- Note [CASEFAIL] = do lbl <- getLabelBc return (testEQ (fst val) lbl `consOL` (snd val `appOL` (LABEL lbl `consOL` unitOL CASEFAIL))) | otherwise = return (testEQ (fst val) lbl_default `consOL` snd val) -- Note [CASEFAIL] -- ~~~~~~~~~~~~~~~ -- It may be that this case has no default -- branch, but the alternatives are not exhaustive - this -- happens for GADT cases for example, where the types -- prove that certain branches are impossible. We could -- just assume that the other cases won't occur, but if -- this assumption was wrong (because of a bug in GHC) -- then the result would be a segfault. So instead we -- emit an explicit test and a CASEFAIL instruction that -- causes the interpreter to barf() if it is ever -- executed. mkTree vals range_lo range_hi = let n = length vals `div` 2 vals_lo = take n vals vals_hi = drop n vals v_mid = fst (head vals_hi) in do label_geq <- getLabelBc code_lo <- mkTree vals_lo range_lo (dec v_mid) code_hi <- mkTree vals_hi v_mid range_hi return (testLT v_mid label_geq `consOL` (code_lo `appOL` unitOL (LABEL label_geq) `appOL` code_hi)) the_default = case defaults of [] -> nilOL [(_, def)] -> LABEL lbl_default `consOL` def _ -> panic "mkMultiBranch/the_default" instrs <- mkTree notd_ways init_lo init_hi return (instrs `appOL` the_default) where (defaults, not_defaults) = partition (isNoDiscr.fst) raw_ways notd_ways = sortBy (comparing fst) not_defaults testLT (DiscrI i) fail_label = TESTLT_I i fail_label testLT (DiscrW i) fail_label = TESTLT_W i fail_label testLT (DiscrF i) fail_label = TESTLT_F i fail_label testLT (DiscrD i) fail_label = TESTLT_D i fail_label testLT (DiscrP i) fail_label = TESTLT_P i fail_label testLT NoDiscr _ = panic "mkMultiBranch NoDiscr" testEQ (DiscrI i) fail_label = TESTEQ_I i fail_label testEQ (DiscrW i) fail_label = TESTEQ_W i fail_label testEQ (DiscrF i) fail_label = TESTEQ_F i fail_label testEQ (DiscrD i) fail_label = TESTEQ_D i fail_label testEQ (DiscrP i) fail_label = TESTEQ_P i fail_label testEQ NoDiscr _ = panic "mkMultiBranch NoDiscr" -- None of these will be needed if there are no non-default alts (init_lo, init_hi) | null notd_ways = panic "mkMultiBranch: awesome foursome" | otherwise = case fst (head notd_ways) of DiscrI _ -> ( DiscrI minBound, DiscrI maxBound ) DiscrW _ -> ( DiscrW minBound, DiscrW maxBound ) DiscrF _ -> ( DiscrF minF, DiscrF maxF ) DiscrD _ -> ( DiscrD minD, DiscrD maxD ) DiscrP _ -> ( DiscrP algMinBound, DiscrP algMaxBound ) NoDiscr -> panic "mkMultiBranch NoDiscr" (algMinBound, algMaxBound) = case maybe_ncons of -- XXX What happens when n == 0? Just n -> (0, fromIntegral n - 1) Nothing -> (minBound, maxBound) isNoDiscr NoDiscr = True isNoDiscr _ = False dec (DiscrI i) = DiscrI (i-1) dec (DiscrW w) = DiscrW (w-1) dec (DiscrP i) = DiscrP (i-1) dec other = other -- not really right, but if you -- do cases on floating values, you'll get what you deserve -- same snotty comment applies to the following minF, maxF :: Float minD, maxD :: Double minF = -1.0e37 maxF = 1.0e37 minD = -1.0e308 maxD = 1.0e308 -- ----------------------------------------------------------------------------- -- Supporting junk for the compilation schemes -- Describes case alts data Discr = DiscrI Int | DiscrW Word | DiscrF Float | DiscrD Double | DiscrP Word16 | NoDiscr deriving (Eq, Ord) instance Outputable Discr where ppr (DiscrI i) = int i ppr (DiscrW w) = text (show w) ppr (DiscrF f) = text (show f) ppr (DiscrD d) = text (show d) ppr (DiscrP i) = ppr i ppr NoDiscr = text "DEF" lookupBCEnv_maybe :: Id -> BCEnv -> Maybe ByteOff lookupBCEnv_maybe = Map.lookup idSizeW :: Platform -> Id -> WordOff idSizeW platform = WordOff . argRepSizeW platform . bcIdArgRep platform idSizeCon :: Platform -> Id -> ByteOff idSizeCon platform var -- unboxed tuple components are padded to word size | isUnboxedTupleType (idType var) || isUnboxedSumType (idType var) = wordsToBytes platform . WordOff . sum . map (argRepSizeW platform . toArgRep platform) . bcIdPrimReps $ var | otherwise = ByteOff (primRepSizeB platform (bcIdPrimRep var)) bcIdArgRep :: Platform -> Id -> ArgRep bcIdArgRep platform = toArgRep platform . bcIdPrimRep bcIdPrimRep :: Id -> PrimRep bcIdPrimRep id | [rep] <- typePrimRepArgs (idType id) = rep | otherwise = pprPanic "bcIdPrimRep" (ppr id <+> dcolon <+> ppr (idType id)) bcIdPrimReps :: Id -> [PrimRep] bcIdPrimReps id = typePrimRepArgs (idType id) repSizeWords :: Platform -> PrimRep -> WordOff repSizeWords platform rep = WordOff $ argRepSizeW platform (toArgRep platform rep) isFollowableArg :: ArgRep -> Bool isFollowableArg P = True isFollowableArg _ = False -- | Indicate if the calling convention is supported isSupportedCConv :: CCallSpec -> Bool isSupportedCConv (CCallSpec _ cconv _) = case cconv of CCallConv -> True -- we explicitly pattern match on every StdCallConv -> True -- convention to ensure that a warning PrimCallConv -> False -- is triggered when a new one is added JavaScriptCallConv -> False CApiConv -> True -- See bug #10462 unsupportedCConvException :: a unsupportedCConvException = throwGhcException (ProgramError ("Error: bytecode compiler can't handle some foreign calling conventions\n"++ " Workaround: use -fobject-code, or compile this module to .o separately.")) mkSlideB :: Platform -> ByteOff -> ByteOff -> OrdList BCInstr mkSlideB platform !nb !db = mkSlideW n d where !n = trunc16W $ bytesToWords platform nb !d = bytesToWords platform db mkSlideW :: Word16 -> WordOff -> OrdList BCInstr mkSlideW !n !ws | ws > fromIntegral limit -- If the amount to slide doesn't fit in a Word16, generate multiple slide -- instructions = SLIDE n limit `consOL` mkSlideW n (ws - fromIntegral limit) | ws == 0 = nilOL | otherwise = unitOL (SLIDE n $ fromIntegral ws) where limit :: Word16 limit = maxBound atomPrimRep :: StgArg -> PrimRep atomPrimRep (StgVarArg v) = bcIdPrimRep v atomPrimRep (StgLitArg l) = typePrimRep1 (literalType l) atomRep :: Platform -> StgArg -> ArgRep atomRep platform e = toArgRep platform (atomPrimRep e) -- | Let szsw be the sizes in bytes of some items pushed onto the stack, which -- has initial depth @original_depth@. Return the values which the stack -- environment should map these items to. mkStackOffsets :: ByteOff -> [ByteOff] -> [ByteOff] mkStackOffsets original_depth szsb = tail (scanl' (+) original_depth szsb) typeArgReps :: Platform -> Type -> [ArgRep] typeArgReps platform = map (toArgRep platform) . typePrimRepArgs -- ----------------------------------------------------------------------------- -- The bytecode generator's monad data BcM_State = BcM_State { bcm_hsc_env :: HscEnv , thisModule :: Module -- current module (for breakpoints) , nextlabel :: Word32 -- for generating local labels , ffis :: [FFIInfo] -- ffi info blocks, to free later -- Should be free()d when it is GCd , modBreaks :: Maybe ModBreaks -- info about breakpoints , breakInfo :: IntMap CgBreakInfo , topStrings :: IdEnv (RemotePtr ()) -- top-level string literals -- See Note [generating code for top-level string literal bindings]. } newtype BcM r = BcM (BcM_State -> IO (BcM_State, r)) deriving (Functor) ioToBc :: IO a -> BcM a ioToBc io = BcM $ \st -> do x <- io return (st, x) runBc :: HscEnv -> Module -> Maybe ModBreaks -> IdEnv (RemotePtr ()) -> BcM r -> IO (BcM_State, r) runBc hsc_env this_mod modBreaks topStrings (BcM m) = m (BcM_State hsc_env this_mod 0 [] modBreaks IntMap.empty topStrings) thenBc :: BcM a -> (a -> BcM b) -> BcM b thenBc (BcM expr) cont = BcM $ \st0 -> do (st1, q) <- expr st0 let BcM k = cont q (st2, r) <- k st1 return (st2, r) thenBc_ :: BcM a -> BcM b -> BcM b thenBc_ (BcM expr) (BcM cont) = BcM $ \st0 -> do (st1, _) <- expr st0 (st2, r) <- cont st1 return (st2, r) returnBc :: a -> BcM a returnBc result = BcM $ \st -> (return (st, result)) instance Applicative BcM where pure = returnBc (<*>) = ap (*>) = thenBc_ instance Monad BcM where (>>=) = thenBc (>>) = (*>) instance HasDynFlags BcM where getDynFlags = BcM $ \st -> return (st, hsc_dflags (bcm_hsc_env st)) getHscEnv :: BcM HscEnv getHscEnv = BcM $ \st -> return (st, bcm_hsc_env st) getProfile :: BcM Profile getProfile = targetProfile <$> getDynFlags emitBc :: ([FFIInfo] -> ProtoBCO Name) -> BcM (ProtoBCO Name) emitBc bco = BcM $ \st -> return (st{ffis=[]}, bco (ffis st)) recordFFIBc :: RemotePtr C_ffi_cif -> BcM () recordFFIBc a = BcM $ \st -> return (st{ffis = FFIInfo a : ffis st}, ()) getLabelBc :: BcM LocalLabel getLabelBc = BcM $ \st -> do let nl = nextlabel st when (nl == maxBound) $ panic "getLabelBc: Ran out of labels" return (st{nextlabel = nl + 1}, LocalLabel nl) getLabelsBc :: Word32 -> BcM [LocalLabel] getLabelsBc n = BcM $ \st -> let ctr = nextlabel st in return (st{nextlabel = ctr+n}, coerce [ctr .. ctr+n-1]) getCCArray :: BcM (Array BreakIndex (RemotePtr CostCentre)) getCCArray = BcM $ \st -> let breaks = expectJust "GHC.StgToByteCode.getCCArray" $ modBreaks st in return (st, modBreaks_ccs breaks) newBreakInfo :: BreakIndex -> CgBreakInfo -> BcM () newBreakInfo ix info = BcM $ \st -> return (st{breakInfo = IntMap.insert ix info (breakInfo st)}, ()) getCurrentModule :: BcM Module getCurrentModule = BcM $ \st -> return (st, thisModule st) getTopStrings :: BcM (IdEnv (RemotePtr ())) getTopStrings = BcM $ \st -> return (st, topStrings st) tickFS :: FastString tickFS = fsLit "ticked"