Clash.Core.PartialEval.NormalForm

Normal forms for the partial evaluator. These provide a restricted model of how terms can be constructed (compared to the more liberal Term type) which give a stronger guarantee that evaluation does not produce invalid results. This module is only needed to define new evaluators, for calling an existing evaluator see Clash.Core.PartialEval.

Documentation

type Arg a = Either a Type

An argument applied to a function data constructor primitive.

type Args a = [Arg a]

data Neutral a

Neutral terms cannot be reduced, as they represent things like variables which are unknown, partially applied functions, or case expressions where the subject cannot be inspected. Consider:

v Stuck if "v" is a free variable p x1 ... xn Stuck if "p" is a primitive that cannot be reduced x $ y Stuck if "x" is not known to be a lambda x @ A Stuck if "x" is not known to be a type lambda case x of ... Stuck if "x" is neutral (cannot choose an alternative)

Neutral terms can also be let expressions which preserve required bindings in the normal form representation. Examples of bindings that may be kept are bindings which perform work (and should not be copied) or bindings that are recursive and are still referred to by the body of the let expression.

let ... in ... Preserved bindings are needed by the body

Constructors

NeVar !Id

NePrim !PrimInfo !(Args a)

NeApp !(Neutral a) !a

NeTyApp !(Neutral a) !Type

NeLet !(Bind a) !a

NeCase !a !Type ![(Pat, a)]

Instances

Show a => Show (Neutral a)

Defined in Clash.Core.PartialEval.NormalForm

Methods

showsPrec :: Int -> Neutral a -> ShowS

show :: Neutral a -> String

showList :: [Neutral a] -> ShowS

AsTerm a => AsTerm (Neutral a)

Defined in Clash.Core.PartialEval.AsTerm

Methods

asTerm :: Neutral a -> Term

data Value

A term which has been potentially evaluated to WHNF. If evaluation has occurred, then there will be no redexes at the head of the Value, but sub-terms may still have redexes. Data constructors are only considered to be values when fully applied, if partially applied they should be eta-expanded during evaluation.

Thunks are included so that lazy evaluation can be modelled without needing to store Either Term Value in the environment. This makes the presentation simpler, with the caveat that values must be forced when they are required to not be thunks.

Constructors

VNeutral !(Neutral Value)

VLiteral !Literal

VData !DataCon !(Args Value) !LocalEnv

VLam !Id !Term !LocalEnv

VTyLam !TyVar !Term !LocalEnv

VCast !Value !Type !Type

VTick !Value !TickInfo

VThunk !Term !LocalEnv

Instances

Show Value

Defined in Clash.Core.PartialEval.NormalForm

Methods

showsPrec :: Int -> Value -> ShowS

show :: Value -> String

showList :: [Value] -> ShowS

AsTerm Value

Defined in Clash.Core.PartialEval.AsTerm

Methods

asTerm :: Value -> Term

mkValueTicks :: Value -> [TickInfo] -> Value

stripValue :: Value -> Value

collectValueTicks :: Value -> (Value, [TickInfo])

isUndefined :: Value -> Bool

isUndefinedX :: Value -> Bool

data Normal

A term which is in beta-normal eta-long form (NF). This has no redexes, and all partially applied functions in sub-terms are eta-expanded.

While not strictly necessary, NLam includes the environment at the point the original term was evaluated. This makes it easier for the AsTerm instance for Normal to reintroduce let expressions before lambdas without accidentally floating a let using a lambda bound variable outwards.

Constructors

NNeutral !(Neutral Normal)

NLiteral !Literal

NData !DataCon !(Args Normal)

NLam !Id !Normal !LocalEnv

NTyLam !TyVar !Normal !LocalEnv

NCast !Normal !Type !Type

NTick !Normal !TickInfo

Instances

Show Normal

Defined in Clash.Core.PartialEval.NormalForm

Methods

showsPrec :: Int -> Normal -> ShowS

show :: Normal -> String

showList :: [Normal] -> ShowS

AsTerm Normal

Defined in Clash.Core.PartialEval.AsTerm

Methods

asTerm :: Normal -> Term

data LocalEnv

Constructors

LocalEnv

Fields

• lenvContext :: Id

  The id of the term currently under evaluation.

• lenvTypes :: Map TyVar Type

  Local type environment. These are types that are introduced while evaluating the current term (i.e. by type applications)

• lenvValues :: Map Id Value

  Local term environment. These are WHNF terms or unevaluated thunks introduced while evaluating the current term (i.e. by applications)

• lenvFuel :: Word

  The amount of fuel left in the local environment when the previous head was reached. This is needed so resuming evaluation does not lead to additional fuel being available.

• lenvKeepLifted :: Bool

  When evaluating, keep data constructors for boxed data types (e.g. I#) instead of converting these back to their corresponding primitive. This is used when evaluating terms where the result is subject of a case expression (see note: lifted data types).

Instances

Show LocalEnv

Defined in Clash.Core.PartialEval.NormalForm

Methods

showsPrec :: Int -> LocalEnv -> ShowS

show :: LocalEnv -> String

showList :: [LocalEnv] -> ShowS

MonadReader LocalEnv Eval

Defined in Clash.Core.PartialEval.Monad

Methods

ask :: Eval LocalEnv

local :: (LocalEnv -> LocalEnv) -> Eval a -> Eval a

reader :: (LocalEnv -> a) -> Eval a

data GlobalEnv

Constructors

GlobalEnv

Fields

• genvBindings :: VarEnv (Binding Value)

  Global term environment. These are the potentially evaluated bodies of the top level definitions which are forced on lookup.

• genvTyConMap :: TyConMap

  The type constructors known about by Clash.

• genvInScope :: InScopeSet

  The set of in scope variables during partial evaluation. This includes new variables introduced by the evaluator (such as the ids of binders introduced during eta expansion.)

• genvSupply :: Supply

  The supply of fresh names for generating identifiers.

• genvFuel :: Word

  The remaining fuel which can be spent inlining global variables. This is saved in the local environment, so when evaluation resumes from WHNF the amount of fuel used is preserved.

• genvHeap :: IntMap Value

  The heap containing the results of any evaluated IO primitives.

• genvAddr :: Int

  The address of the next element to be inserted into the heap.

• genvWorkCache :: VarEnv Bool

  Cache for the results of isWorkFree. This is required to use Clash.Rewrite.WorkFree.isWorkFree.

Instances

MonadState GlobalEnv Eval

Defined in Clash.Core.PartialEval.Monad

Methods

get :: Eval GlobalEnv

put :: GlobalEnv -> Eval ()

state :: (GlobalEnv -> (a, GlobalEnv)) -> Eval a

workFreeCache :: Lens' GlobalEnv (VarEnv Bool)