Safe Haskell	Safe-Inferred
Language	Haskell2010

GHC.Core.Opt.Arity

Contents

ArityType
Join points
Coercions and casts

Description

Arity and eta expansion

Synopsis

manifestArity :: CoreExpr -> Arity
joinRhsArity :: CoreExpr -> JoinArity
exprArity :: CoreExpr -> Arity
typeArity :: Type -> [OneShotInfo]
exprEtaExpandArity :: DynFlags -> CoreExpr -> ArityType
findRhsArity :: DynFlags -> Id -> CoreExpr -> Arity -> ArityType
etaExpand :: Arity -> CoreExpr -> CoreExpr
etaExpandAT :: ArityType -> CoreExpr -> CoreExpr
exprBotStrictness_maybe :: CoreExpr -> Maybe (Arity, StrictSig)
data ArityType = AT ![OneShotInfo] !Divergence
mkBotArityType :: [OneShotInfo] -> ArityType
mkTopArityType :: [OneShotInfo] -> ArityType
expandableArityType :: ArityType -> Bool
arityTypeArity :: ArityType -> Arity
maxWithArity :: ArityType -> Arity -> ArityType
idArityType :: Id -> ArityType
etaExpandToJoinPoint :: JoinArity -> CoreExpr -> ([CoreBndr], CoreExpr)
etaExpandToJoinPointRule :: JoinArity -> CoreRule -> CoreRule
pushCoArg :: CoercionR -> CoreArg -> Maybe (CoreArg, MCoercion)
pushCoArgs :: CoercionR -> [CoreArg] -> Maybe ([CoreArg], MCoercion)
pushCoValArg :: CoercionR -> Maybe (MCoercionR, MCoercionR)
pushCoTyArg :: CoercionR -> Type -> Maybe (Type, MCoercionR)
pushCoercionIntoLambda :: InScopeSet -> Var -> CoreExpr -> CoercionR -> Maybe (Var, CoreExpr)
pushCoDataCon :: DataCon -> [CoreExpr] -> Coercion -> Maybe (DataCon, [Type], [CoreExpr])
collectBindersPushingCo :: CoreExpr -> ([Var], CoreExpr)

Documentation

manifestArity :: CoreExpr -> Arity Source #

manifestArity sees how many leading value lambdas there are, after looking through casts

joinRhsArity :: CoreExpr -> JoinArity Source #

exprArity :: CoreExpr -> Arity Source #

An approximate, fast, version of exprEtaExpandArity

typeArity :: Type -> [OneShotInfo] Source #

exprEtaExpandArity :: DynFlags -> CoreExpr -> ArityType Source #

The Arity returned is the number of value args the expression can be applied to without doing much work

findRhsArity :: DynFlags -> Id -> CoreExpr -> Arity -> ArityType Source #

etaExpand :: Arity -> CoreExpr -> CoreExpr Source #

etaExpand n e returns an expression with the same meaning as e, but with arity n.

Given:

e' = etaExpand n e

We should have that:

ty = exprType e = exprType e'

etaExpandAT :: ArityType -> CoreExpr -> CoreExpr Source #

exprBotStrictness_maybe :: CoreExpr -> Maybe (Arity, StrictSig) Source #

ArityType

data ArityType Source #

The analysis lattice of arity analysis. It is isomorphic to

   data ArityType'
     = AEnd Divergence
     | ALam OneShotInfo ArityType'

Which is easier to display the Hasse diagram for:

 ALam OneShotLam at
         |
     AEnd topDiv
         |
 ALam NoOneShotInfo at
         |
     AEnd exnDiv
         |
     AEnd botDiv

where the at fields of ALam are inductively subject to the same order. That is, ALam os at1 < ALam os at2 iff at1 < at2.

Why the strange Top element? See Note [Combining case branches].

We rely on this lattice structure for fixed-point iteration in findRhsArity. For the semantics of ArityType, see Note [ArityType].

Constructors

AT ![OneShotInfo] !Divergence

AT oss div means this value can safely be eta-expanded length oss times, provided use sites respect the OneShotInfos in oss. A OneShotLam annotation can come from two sources: * The user annotated a lambda as one-shot with oneShot * It's from a lambda binder of a type affected by `-fstate-hack`. See idStateHackOneShotInfo. In both cases, OneShotLam should win over NoOneShotInfo, see Note [Combining case branches].

If div is dead-ending (isDeadEndDiv), then application to length os arguments will surely diverge, similar to the situation with DmdType.

Instances

Instances details

Outputable ArityType #	This is the BNF of the generated output: @ We format AT [o1,..,on] topDiv `as` o1..on.T`and`AT [o1,..,on] botDiv `as` o1..on.⊥`, respectively. More concretely,`AT [NOI,OS,OS] topDiv `is formatted as` ?11.T`. If the one-shot info is empty, we omit the leading`.@.
Instance details Defined in GHC.Core.Opt.Arity Methods ppr :: ArityType -> SDoc Source #
Eq ArityType #
Instance details Defined in GHC.Core.Opt.Arity Methods (==) :: ArityType -> ArityType -> Bool # (/=) :: ArityType -> ArityType -> Bool #