%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[CoreUtils]{Utility functions on @Core@ syntax}
\begin{code}
-#include "HsVersions.h"
-
module CoreUtils (
coreExprType, coreAltsType,
- substCoreExpr
-
- , mkCoreIfThenElse
- , mkErrorApp, escErrorMsg
- , argToExpr
- , unTagBinders, unTagBindersAlts
-{- exprSmallEnoughToDup,
- manifestlyWHNF, manifestlyBottom,
- coreExprArity,
- isWrapperFor,
- maybeErrorApp,
- nonErrorRHSs,
- squashableDictishCcExpr,
+ exprIsBottom, exprIsDupable, exprIsTrivial, exprIsWHNF, exprIsCheap, exprIsValue,
+ exprOkForSpeculation,
+ FormSummary(..), mkFormSummary, whnfOrBottom, exprArity,
+ cheapEqExpr, eqExpr, applyTypeToArgs
+ ) where
--} ) where
+#include "HsVersions.h"
-import Ubiq
-import IdLoop -- for pananoia-checking purposes
import CoreSyn
-
-import CostCentre ( isDictCC )
-import Id ( idType, mkSysLocal,
- addOneToIdEnv, growIdEnvList, lookupIdEnv,
- isNullIdEnv, IdEnv(..),
- GenId{-instances-}
- )
-import Literal ( literalType, isNoRepLit, Literal(..) )
-import Maybes ( catMaybes )
-import PprCore ( GenCoreExpr{-instances-}, GenCoreArg{-instances-} )
-import PprStyle ( PprStyle(..) )
-import PprType ( GenType{-instances-}, GenTyVar{-instance-} )
-import Pretty ( ppAboves )
-import PrelInfo ( trueDataCon, falseDataCon,
- augmentId, buildId,
- pAT_ERROR_ID
+import PprCore ( pprCoreExpr )
+import Var ( IdOrTyVar, isId, isTyVar )
+import VarSet
+import VarEnv
+import Name ( isLocallyDefined )
+import Const ( Con, isWHNFCon, conIsTrivial, conIsCheap, conIsDupable,
+ conType, conOkForSpeculation, conStrictness
)
-import PrimOp ( primOpType, PrimOp(..) )
-import SrcLoc ( mkUnknownSrcLoc )
-import TyVar ( isNullTyVarEnv, TyVarEnv(..), GenTyVar{-instances-} )
-import Type ( mkFunTys, mkForAllTy, mkForAllUsageTy,
- getFunTy_maybe, applyTy, splitSigmaTy
+import Id ( Id, idType, setIdType, idUnique, idAppIsBottom,
+ getIdArity,
+ getIdSpecialisation, setIdSpecialisation,
+ getInlinePragma, setInlinePragma,
+ getIdUnfolding, setIdUnfolding, idInfo
)
-import Unique ( Unique{-instances-} )
-import UniqSupply ( initUs, returnUs, thenUs,
- mapUs, mapAndUnzipUs,
- UniqSM(..), UniqSupply
+import IdInfo ( arityLowerBound, InlinePragInfo(..), lbvarInfo, LBVarInfo(..) )
+import Type ( Type, mkFunTy, mkForAllTy,
+ splitFunTy_maybe, tyVarsOfType, tyVarsOfTypes,
+ isNotUsgTy, mkUsgTy, unUsgTy, UsageAnn(..),
+ tidyTyVar, applyTys, isUnLiftedType
)
-import Util ( zipEqual, panic, pprPanic, assertPanic )
-
-type TypeEnv = TyVarEnv Type
-applyUsage = panic "CoreUtils.applyUsage:ToDo"
-dup_binder = panic "CoreUtils.dup_binder"
-applyTypeEnvToTy = panic "CoreUtils.applyTypeEnvToTy"
+import Demand ( isPrim, isLazy )
+import Unique ( buildIdKey, augmentIdKey )
+import Util ( zipWithEqual, mapAccumL )
+import Outputable
+import TysPrim ( alphaTy ) -- Debugging only
\end{code}
+
%************************************************************************
%* *
\subsection{Find the type of a Core atom/expression}
\begin{code}
coreExprType :: CoreExpr -> Type
-coreExprType (Var var) = idType var
-coreExprType (Lit lit) = literalType lit
-
-coreExprType (Let _ body) = coreExprType body
-coreExprType (SCC _ expr) = coreExprType expr
-coreExprType (Case _ alts) = coreAltsType alts
-
--- a Con is a fully-saturated application of a data constructor
--- a Prim is <ditto> of a PrimOp
-
-coreExprType (Con con args) = applyTypeToArgs (idType con) args
-coreExprType (Prim op args) = applyTypeToArgs (primOpType op) args
-
-coreExprType (Lam (ValBinder binder) expr)
- = mkFunTys [idType binder] (coreExprType expr)
-
-coreExprType (Lam (TyBinder tyvar) expr)
- = mkForAllTy tyvar (coreExprType expr)
-
-coreExprType (Lam (UsageBinder uvar) expr)
- = mkForAllUsageTy uvar (panic "coreExprType:Lam UsageBinder") (coreExprType expr)
-
-coreExprType (App expr (TyArg ty))
- = applyTy (coreExprType expr) ty
-
-coreExprType (App expr (UsageArg use))
- = applyUsage (coreExprType expr) use
-
-coreExprType (App expr val_arg)
- = ASSERT(isValArg val_arg)
- let
- fun_ty = coreExprType expr
- in
- case (getFunTy_maybe fun_ty) of
- Just (_, result_ty) -> result_ty
-#ifdef DEBUG
- Nothing -> pprPanic "coreExprType:\n"
- (ppAboves [ppr PprDebug fun_ty,
- ppr PprShowAll (App expr val_arg)])
-#endif
+coreExprType (Var var) = idType var
+coreExprType (Let _ body) = coreExprType body
+coreExprType (Case _ _ alts) = coreAltsType alts
+coreExprType (Note (Coerce ty _) e) = ty
+coreExprType (Note (TermUsg u) e) = mkUsgTy u (unUsgTy (coreExprType e))
+coreExprType (Note other_note e) = coreExprType e
+coreExprType e@(Con con args) = applyTypeToArgs e (conType con) args
+
+coreExprType (Lam binder expr)
+ | isId binder = (case (lbvarInfo . idInfo) binder of
+ IsOneShotLambda -> mkUsgTy UsOnce
+ otherwise -> id) $
+ idType binder `mkFunTy` coreExprType expr
+ | isTyVar binder = mkForAllTy binder (coreExprType expr)
+
+coreExprType e@(App _ _)
+ = case collectArgs e of
+ (fun, args) -> applyTypeToArgs e (coreExprType fun) args
+
+coreExprType other = pprTrace "coreExprType" (pprCoreExpr other) alphaTy
+
+coreAltsType :: [CoreAlt] -> Type
+coreAltsType ((_,_,rhs) : _) = coreExprType rhs
\end{code}
\begin{code}
-coreAltsType :: CoreCaseAlts -> Type
-
-coreAltsType (AlgAlts [] deflt) = default_ty deflt
-coreAltsType (AlgAlts ((_,_,rhs1):_) _) = coreExprType rhs1
-
-coreAltsType (PrimAlts [] deflt) = default_ty deflt
-coreAltsType (PrimAlts ((_,rhs1):_) _) = coreExprType rhs1
-
-default_ty NoDefault = panic "coreExprType:Case:default_ty"
-default_ty (BindDefault _ rhs) = coreExprType rhs
+-- The first argument is just for debugging
+applyTypeToArgs :: CoreExpr -> Type -> [CoreExpr] -> Type
+applyTypeToArgs e op_ty [] = op_ty
+
+applyTypeToArgs e op_ty (Type ty : args)
+ = -- Accumulate type arguments so we can instantiate all at once
+ ASSERT2( all isNotUsgTy tys, ppr e <+> text "of" <+> ppr op_ty <+> text "to" <+> ppr (Type ty : args) <+> text "i.e." <+> ppr tys )
+ applyTypeToArgs e (applyTys op_ty tys) rest_args
+ where
+ (tys, rest_args) = go [ty] args
+ go tys (Type ty : args) = go (ty:tys) args
+ go tys rest_args = (reverse tys, rest_args)
+
+applyTypeToArgs e op_ty (other_arg : args)
+ = case (splitFunTy_maybe op_ty) of
+ Just (_, res_ty) -> applyTypeToArgs e res_ty args
+ Nothing -> pprPanic "applyTypeToArgs" (pprCoreExpr e)
\end{code}
-\begin{code}
-applyTypeToArgs = panic "applyTypeToArgs"
-\end{code}
%************************************************************************
%* *
-\subsection{Routines to manufacture bits of @CoreExpr@}
+\subsection{Figuring out things about expressions}
%* *
%************************************************************************
\begin{code}
-mkCoreIfThenElse (Var bool) then_expr else_expr
- | bool == trueDataCon = then_expr
- | bool == falseDataCon = else_expr
-
-mkCoreIfThenElse guard then_expr else_expr
- = Case guard
- (AlgAlts [ (trueDataCon, [], then_expr),
- (falseDataCon, [], else_expr) ]
- NoDefault )
+data FormSummary
+ = VarForm -- Expression is a variable (or scc var, etc)
+
+ | ValueForm -- Expression is a value: i.e. a value-lambda,constructor, or literal
+ -- May 1999: I'm experimenting with allowing "cheap" non-values
+ -- here.
+
+ | BottomForm -- Expression is guaranteed to be bottom. We're more gung
+ -- ho about inlining such things, because it can't waste work
+ | OtherForm -- Anything else
+
+instance Outputable FormSummary where
+ ppr VarForm = ptext SLIT("Var")
+ ppr ValueForm = ptext SLIT("Value")
+ ppr BottomForm = ptext SLIT("Bot")
+ ppr OtherForm = ptext SLIT("Other")
+
+whnfOrBottom :: FormSummary -> Bool
+whnfOrBottom VarForm = True
+whnfOrBottom ValueForm = True
+whnfOrBottom BottomForm = True
+whnfOrBottom OtherForm = False
\end{code}
\begin{code}
-mkErrorApp :: Type -> Id -> String -> CoreExpr
+mkFormSummary :: CoreExpr -> FormSummary
+ -- Used exclusively by CoreUnfold.mkUnfolding
+ -- Returns ValueForm for cheap things, not just values
+mkFormSummary expr
+ = go (0::Int) expr -- The "n" is the number of *value* arguments so far
+ where
+ go n (Con con _) | isWHNFCon con = ValueForm
+ | otherwise = OtherForm
-mkErrorApp ty str_var error_msg
- = Let (NonRec str_var (Lit (NoRepStr (_PK_ error_msg)))) (
- mkApp (Var pAT_ERROR_ID) [] [ty] [VarArg str_var])
+ go n (Note _ e) = go n e
-escErrorMsg [] = []
-escErrorMsg ('%':xs) = '%' : '%' : escErrorMsg xs
-escErrorMsg (x:xs) = x : escErrorMsg xs
-\end{code}
+ go n (Let (NonRec b r) e) | exprIsCheap r = go n e -- let f = f' alpha in (f,g)
+ -- should be treated as a value
+ go n (Let _ e) = OtherForm
-For making @Apps@ and @Lets@, we must take appropriate evasive
-action if the thing being bound has unboxed type. @mkCoApp@ requires
-a name supply to do its work. Other-monad code will call @mkCoApp@
-through its own interface function (e.g., the desugarer uses
-@mkCoAppDs@).
+ -- We want selectors to look like values
+ -- e.g. case x of { (a,b) -> a }
+ -- should give a ValueForm, so that it will be inlined vigorously
+ -- [June 99. I can't remember why this is a good idea. It means that
+ -- all overloading selectors get inlined at their usage sites, which is
+ -- not at all necessarily a good thing. So I'm rescinding this decision for now.]
+-- go n expr@(Case _ _ _) | exprIsCheap expr = ValueForm
-@mkCoApp@, @mkCoCon@ and @mkCoPrim@ also handle the
-arguments-must-be-atoms constraint.
+ go n expr@(Case _ _ _) = OtherForm
-\begin{code}
-{- LATER:
---mkCoApp :: CoreExpr -> CoreExpr -> UniqSM CoreExpr
-
-mkCoApp e1 (Var v) = returnUs (App e1 (VarArg v))
-mkCoApp e1 (Lit l) = returnUs (App e1 (LitArg l))
-mkCoApp e1 e2
- = let
- e2_ty = coreExprType e2
- in
- panic "getUnique" `thenUs` \ uniq ->
- let
- new_var = mkSysLocal SLIT("a") uniq e2_ty mkUnknownSrcLoc
- in
- returnUs (
- mkCoLetUnboxedToCase (NonRec new_var e2)
- (App e1 (VarArg new_var))
- )
--}
-\end{code}
+ go 0 (Lam x e) | isId x = ValueForm -- NB: \x.bottom /= bottom!
+ | otherwise = go 0 e
+ go n (Lam x e) | isId x = go (n-1) e -- Applied lambda
+ | otherwise = go n e
-\begin{code}
-{-LATER
-mkCoCon :: Id -> [CoreExpr] -> UniqSM CoreExpr
-mkCoPrim :: PrimOp -> [CoreExpr] -> UniqSM CoreExpr
+ go n (App fun (Type _)) = go n fun -- Ignore type args
+ go n (App fun arg) = go (n+1) fun
-mkCoCon con args = mkCoThing (Con con) args
-mkCoPrim op args = mkCoThing (Prim op) args
-
-mkCoThing thing arg_exprs
- = mapAndUnzipUs expr_to_arg arg_exprs `thenUs` \ (args, maybe_binds) ->
- returnUs (mkCoLetsUnboxedToCase (catMaybes maybe_binds) (thing args))
- where
- expr_to_arg :: CoreExpr
- -> UniqSM (CoreArg, Maybe CoreBinding)
-
- expr_to_arg (Var v) = returnUs (VarArg v, Nothing)
- expr_to_arg (Lit l) = returnUs (LitArg l, Nothing)
- expr_to_arg other_expr
- = let
- e_ty = coreExprType other_expr
- in
- panic "getUnique" `thenUs` \ uniq ->
- let
- new_var = mkSysLocal SLIT("a") uniq e_ty mkUnknownSrcLoc
- new_atom = VarArg new_var
- in
- returnUs (new_atom, Just (NonRec new_var other_expr))
--}
+ go n (Var f) | idAppIsBottom f n = BottomForm
+ go 0 (Var f) = VarForm
+ go n (Var f) | n < arityLowerBound (getIdArity f) = ValueForm
+ | otherwise = OtherForm
\end{code}
-\begin{code}
-argToExpr ::
- GenCoreArg val_occ tyvar uvar -> GenCoreExpr val_bdr val_occ tyvar uvar
+@exprIsTrivial@ is true of expressions we are unconditionally
+ happy to duplicate; simple variables and constants,
+ and type applications.
-argToExpr (VarArg v) = Var v
-argToExpr (LitArg lit) = Lit lit
-\end{code}
+@exprIsBottom@ is true of expressions that are guaranteed to diverge
-\begin{code}
-{- LATER:
---mkCoApps ::
--- GenCoreExpr val_bdr val_occ tyvar uvar ->
--- [GenCoreExpr val_bdr val_occ tyvar uvar] ->
--- UniqSM(GenCoreExpr val_bdr val_occ tyvar uvar)
-
-mkCoApps fun [] = returnUs fun
-mkCoApps fun (arg:args)
- = mkCoApp fun arg `thenUs` \ new_fun ->
- mkCoApps new_fun args
-\end{code}
\begin{code}
-exprSmallEnoughToDup :: GenCoreExpr binder Id -> Bool
-
-exprSmallEnoughToDup (Con _ _ _) = True -- Could check # of args
-exprSmallEnoughToDup (Prim op _ _) = not (fragilePrimOp op) -- Could check # of args
-exprSmallEnoughToDup (Lit lit) = not (isNoRepLit lit)
-
-exprSmallEnoughToDup expr -- for now, just: <var> applied to <args>
- = case (collectArgs expr) of { (fun, args) ->
- case fun of
- Var v -> v /= buildId
- && v /= augmentId
- && length args <= 6 -- or 10 or 1 or 4 or anything smallish.
- _ -> False
- }
+exprIsTrivial (Type _) = True
+exprIsTrivial (Var v) = True
+exprIsTrivial (App e arg) = isTypeArg arg && exprIsTrivial e
+exprIsTrivial (Note _ e) = exprIsTrivial e
+exprIsTrivial (Con con args) = conIsTrivial con && all isTypeArg args
+exprIsTrivial (Lam b body) | isTyVar b = exprIsTrivial body
+exprIsTrivial other = False
\end{code}
-Question (ADR): What is the above used for? Is a _ccall_ really small
-enough?
-@manifestlyWHNF@ looks at a Core expression and returns \tr{True} if
-it is obviously in weak head normal form. It isn't a disaster if it
-errs on the conservative side (returning \tr{False})---I've probably
-left something out... [WDP]
-\begin{code}
-manifestlyWHNF :: GenCoreExpr bndr Id -> Bool
-
-manifestlyWHNF (Var _) = True
-manifestlyWHNF (Lit _) = True
-manifestlyWHNF (Con _ _ _) = True -- ToDo: anything for Prim?
-manifestlyWHNF (Lam _ _) = True
-manifestlyWHNF (CoTyLam _ e) = manifestlyWHNF e
-manifestlyWHNF (SCC _ e) = manifestlyWHNF e
-manifestlyWHNF (Let _ e) = False
-manifestlyWHNF (Case _ _) = False
-
-manifestlyWHNF other_expr -- look for manifest partial application
- = case (collectArgs other_expr) of { (fun, args) ->
- case fun of
- Var f -> let
- num_val_args = length [ a | (ValArg a) <- args ]
- in
- num_val_args == 0 || -- Just a type application of
- -- a variable (f t1 t2 t3)
- -- counts as WHNF
- case (arityMaybe (getIdArity f)) of
- Nothing -> False
- Just arity -> num_val_args < arity
-
- _ -> False
- }
-\end{code}
+@exprIsDupable@ is true of expressions that can be duplicated at a modest
+ cost in space. This will only happen in different case
+ branches, so there's no issue about duplicating work.
+ Its only purpose is to avoid fruitless let-binding
+ and then inlining of case join points
-@manifestlyBottom@ looks at a Core expression and returns \tr{True} if
-it is obviously bottom, that is, it will certainly return bottom at
-some point. It isn't a disaster if it errs on the conservative side
-(returning \tr{False}).
\begin{code}
-manifestlyBottom :: GenCoreExpr bndr Id -> Bool
-
-manifestlyBottom (Var v) = isBottomingId v
-manifestlyBottom (Lit _) = False
-manifestlyBottom (Con _ _ _) = False
-manifestlyBottom (Prim _ _ _)= False
-manifestlyBottom (Lam _ _) = False -- we do not assume \x.bottom == bottom. should we? ToDo
-manifestlyBottom (CoTyLam _ e) = manifestlyBottom e
-manifestlyBottom (SCC _ e) = manifestlyBottom e
-manifestlyBottom (Let _ e) = manifestlyBottom e
-
-manifestlyBottom (Case e a)
- = manifestlyBottom e
- || (case a of
- AlgAlts alts def -> all mbalg alts && mbdef def
- PrimAlts alts def -> all mbprim alts && mbdef def
- )
- where
- mbalg (_,_,e') = manifestlyBottom e'
-
- mbprim (_,e') = manifestlyBottom e'
-
- mbdef NoDefault = True
- mbdef (BindDefault _ e') = manifestlyBottom e'
-
-manifestlyBottom other_expr -- look for manifest partial application
- = case (collectArgs other_expr) of { (fun, args) ->
- case fun of
- Var f | isBottomingId f -> True -- Application of a function which
- -- always gives bottom; we treat this as
- -- a WHNF, because it certainly doesn't
- -- need to be shared!
- _ -> False
- }
+exprIsDupable (Type _) = True
+exprIsDupable (Con con args) = conIsDupable con &&
+ all exprIsDupable args &&
+ valArgCount args <= dupAppSize
+
+exprIsDupable (Note _ e) = exprIsDupable e
+exprIsDupable expr = case collectArgs expr of
+ (Var f, args) -> valArgCount args <= dupAppSize
+ other -> False
+
+dupAppSize :: Int
+dupAppSize = 4 -- Size of application we are prepared to duplicate
\end{code}
-\begin{code}
-coreExprArity
- :: (Id -> Maybe (GenCoreExpr bndr Id))
- -> GenCoreExpr bndr Id
- -> Int
-coreExprArity f (Lam _ expr) = coreExprArity f expr + 1
-coreExprArity f (CoTyLam _ expr) = coreExprArity f expr
-coreExprArity f (App expr arg) = max (coreExprArity f expr - 1) 0
-coreExprArity f (CoTyApp expr _) = coreExprArity f expr
-coreExprArity f (Var v) = max further info
- where
- further
- = case f v of
- Nothing -> 0
- Just expr -> coreExprArity f expr
- info = case (arityMaybe (getIdArity v)) of
- Nothing -> 0
- Just arity -> arity
-coreExprArity f _ = 0
-\end{code}
+@exprIsCheap@ looks at a Core expression and returns \tr{True} if
+it is obviously in weak head normal form, or is cheap to get to WHNF.
+[Note that that's not the same as exprIsDupable; an expression might be
+big, and hence not dupable, but still cheap.]
+By ``cheap'' we mean a computation we're willing to push inside a lambda
+in order to bring a couple of lambdas together. That might mean it gets
+evaluated more than once, instead of being shared. The main examples of things
+which aren't WHNF but are ``cheap'' are:
-@isWrapperFor@: we want to see exactly:
-\begin{verbatim}
-/\ ... \ args -> case <arg> of ... -> case <arg> of ... -> wrkr <stuff>
-\end{verbatim}
+ * case e of
+ pi -> ei
-Probably a little too HACKY [WDP].
+ where e, and all the ei are cheap; and
-\begin{code}
-isWrapperFor :: CoreExpr -> Id -> Bool
+ * let x = e
+ in b
-expr `isWrapperFor` var
- = case (digForLambdas expr) of { (_, _, args, body) -> -- lambdas off the front
- unravel_casing args body
- --NO, THANKS: && not (null args)
- }
- where
- var's_worker = getWorkerId (getIdStrictness var)
-
- is_elem = isIn "isWrapperFor"
-
- --------------
- unravel_casing case_ables (Case scrut alts)
- = case (collectArgs scrut) of { (fun, args) ->
- case fun of
- Var scrut_var -> let
- answer =
- scrut_var /= var && all (doesn't_mention var) args
- && scrut_var `is_elem` case_ables
- && unravel_alts case_ables alts
- in
- answer
-
- _ -> False
- }
+ where e and b are cheap; and
- unravel_casing case_ables other_expr
- = case (collectArgs other_expr) of { (fun, args) ->
- case fun of
- Var wrkr -> let
- answer =
- -- DOESN'T WORK: wrkr == var's_worker
- wrkr /= var
- && isWorkerId wrkr
- && all (doesn't_mention var) args
- && all (only_from case_ables) args
- in
- answer
-
- _ -> False
- }
+ * op x1 ... xn
- --------------
- unravel_alts case_ables (AlgAlts [(_,params,rhs)] NoDefault)
- = unravel_casing (params ++ case_ables) rhs
- unravel_alts case_ables other = False
+ where op is a cheap primitive operator
- -------------------------
- doesn't_mention var (ValArg (VarArg v)) = v /= var
- doesn't_mention var other = True
-
- -------------------------
- only_from case_ables (ValArg (VarArg v)) = v `is_elem` case_ables
- only_from case_ables other = True
--}
-\end{code}
-
-All the following functions operate on binders, perform a uniform
-transformation on them; ie. the function @(\ x -> (x,False))@
-annotates all binders with False.
+Notice that a variable is considered 'cheap': we can push it inside a lambda,
+because sharing will make sure it is only evaluated once.
\begin{code}
-unTagBinders :: GenCoreExpr (Id,tag) bdee tv uv -> GenCoreExpr Id bdee tv uv
-unTagBinders expr = bop_expr fst expr
-
-unTagBindersAlts :: GenCoreCaseAlts (Id,tag) bdee tv uv -> GenCoreCaseAlts Id bdee tv uv
-unTagBindersAlts alts = bop_alts fst alts
+exprIsCheap :: CoreExpr -> Bool
+exprIsCheap (Type _) = True
+exprIsCheap (Var _) = True
+exprIsCheap (Con con args) = conIsCheap con && all exprIsCheap args
+exprIsCheap (Note _ e) = exprIsCheap e
+exprIsCheap (Lam x e) = if isId x then True else exprIsCheap e
+exprIsCheap (Let bind body) = all exprIsCheap (rhssOfBind bind) && exprIsCheap body
+exprIsCheap (Case scrut _ alts) = exprIsCheap scrut &&
+ all (\(_,_,rhs) -> exprIsCheap rhs) alts
+
+exprIsCheap other_expr -- look for manifest partial application
+ = case collectArgs other_expr of
+ (f, args) -> isPap f (valArgCount args) && all exprIsCheap args
\end{code}
\begin{code}
-bop_expr :: (a -> b) -> GenCoreExpr a bdee tv uv -> GenCoreExpr b bdee tv uv
-
-bop_expr f (Var b) = Var b
-bop_expr f (Lit lit) = Lit lit
-bop_expr f (Con con args) = Con con args
-bop_expr f (Prim op args) = Prim op args
-bop_expr f (Lam binder expr) = Lam (bop_binder f binder) (bop_expr f expr)
-bop_expr f (App expr arg) = App (bop_expr f expr) arg
-bop_expr f (SCC label expr) = SCC label (bop_expr f expr)
-bop_expr f (Let bind expr) = Let (bop_bind f bind) (bop_expr f expr)
-bop_expr f (Case expr alts) = Case (bop_expr f expr) (bop_alts f alts)
-
-bop_binder f (ValBinder v) = ValBinder (f v)
-bop_binder f (TyBinder t) = TyBinder t
-bop_binder f (UsageBinder u) = UsageBinder u
-
-bop_bind f (NonRec b e) = NonRec (f b) (bop_expr f e)
-bop_bind f (Rec pairs) = Rec [(f b, bop_expr f e) | (b, e) <- pairs]
-
-bop_alts f (AlgAlts alts deflt)
- = AlgAlts [ (con, [f b | b <- binders], bop_expr f e)
- | (con, binders, e) <- alts ]
- (bop_deflt f deflt)
-
-bop_alts f (PrimAlts alts deflt)
- = PrimAlts [ (lit, bop_expr f e) | (lit, e) <- alts ]
- (bop_deflt f deflt)
-
-bop_deflt f (NoDefault) = NoDefault
-bop_deflt f (BindDefault b expr) = BindDefault (f b) (bop_expr f expr)
+isPap :: CoreExpr -- Function
+ -> Int -- Number of value args
+ -> Bool
+isPap (Var f) n_val_args
+ = idAppIsBottom f n_val_args
+ -- Application of a function which
+ -- always gives bottom; we treat this as
+ -- a WHNF, because it certainly doesn't
+ -- need to be shared!
+
+ || n_val_args == 0 -- Just a type application of
+ -- a variable (f t1 t2 t3)
+ -- counts as WHNF
+
+ || n_val_args < arityLowerBound (getIdArity f)
+
+isPap fun n_val_args = False
\end{code}
-OLD (but left here because of the nice example): @singleAlt@ checks
-whether a bunch of case alternatives is actually just one alternative.
-It specifically {\em ignores} alternatives which consist of just a
-call to @error@, because they won't result in any code duplication.
-
-Example:
-\begin{verbatim}
- case (case <something> of
- True -> <rhs>
- False -> error "Foo") of
- <alts>
-
-===>
-
- case <something> of
- True -> case <rhs> of
- <alts>
- False -> case error "Foo" of
- <alts>
-
-===>
+exprOkForSpeculation returns True of an UNLIFTED-TYPE expression that it is safe
+to evaluate even if normal order eval might not evaluate the expression
+at all. E.G.
+ let x = case y# +# 1# of { r# -> I# r# }
+ in E
+==>
+ case y# +# 1# of { r# ->
+ let x = I# r#
+ in E
+ }
- case <something> of
- True -> case <rhs> of
- <alts>
- False -> error "Foo"
-\end{verbatim}
-Notice that the \tr{<alts>} don't get duplicated.
+We can only do this if the (y+1) is ok for speculation: it has no
+side effects, and can't diverge or raise an exception.
\begin{code}
-{- LATER:
-nonErrorRHSs :: GenCoreCaseAlts binder Id -> [GenCoreExpr binder Id]
-
-nonErrorRHSs alts = filter not_error_app (find_rhss alts)
+exprOkForSpeculation :: CoreExpr -> Bool
+exprOkForSpeculation (Var v) = True -- Unlifted type => already evaluated
+
+exprOkForSpeculation (Note _ e) = exprOkForSpeculation e
+exprOkForSpeculation (Let (NonRec b r) e) = isUnLiftedType (idType b) &&
+ exprOkForSpeculation r &&
+ exprOkForSpeculation e
+exprOkForSpeculation (Let (Rec _) _) = False
+exprOkForSpeculation (Case _ _ _) = False -- Conservative
+exprOkForSpeculation (App _ _) = False
+
+exprOkForSpeculation (Con con args)
+ = conOkForSpeculation con &&
+ and (zipWith ok (filter isValArg args) (fst (conStrictness con)))
where
- find_rhss (AlgAlts alts deflt) = [rhs | (_,_,rhs) <- alts] ++ deflt_rhs deflt
- find_rhss (PrimAlts alts deflt) = [rhs | (_,rhs) <- alts] ++ deflt_rhs deflt
-
- deflt_rhs NoDefault = []
- deflt_rhs (BindDefault _ rhs) = [rhs]
+ ok arg demand | isLazy demand = True
+ | isPrim demand = exprOkForSpeculation arg
+ | otherwise = False
- not_error_app rhs = case maybeErrorApp rhs Nothing of
- Just _ -> False
- Nothing -> True
+exprOkForSpeculation other = panic "exprOkForSpeculation"
+ -- Lam, Type
\end{code}
-maybeErrorApp checkes whether an expression is of the form
- error ty args
-
-If so, it returns
-
- Just (error ty' args)
-
-where ty' is supplied as an argument to maybeErrorApp.
-
-Here's where it is useful:
-
- case (error ty "Foo" e1 e2) of <alts>
- ===>
- error ty' "Foo"
-
-where ty' is the type of any of the alternatives.
-You might think this never occurs, but see the comments on
-the definition of @singleAlt@.
-
-Note: we *avoid* the case where ty' might end up as a
-primitive type: this is very uncool (totally wrong).
-
-NOTICE: in the example above we threw away e1 and e2, but
-not the string "Foo". How did we know to do that?
-
-Answer: for now anyway, we only handle the case of a function
-whose type is of form
+\begin{code}
+exprIsBottom :: CoreExpr -> Bool -- True => definitely bottom
+exprIsBottom e = go 0 e
+ where
+ -- n is the number of args
+ go n (Note _ e) = go n e
+ go n (Let _ e) = go n e
+ go n (Case e _ _) = go 0 e -- Just check the scrut
+ go n (App e _) = go (n+1) e
+ go n (Var v) = idAppIsBottom v n
+ go n (Con _ _) = False
+ go n (Lam _ _) = False
+\end{code}
- bottomingFn :: forall a. t1 -> ... -> tn -> a
- ^---------------------^ NB!
+@exprIsValue@ returns true for expressions that are evaluated.
+It does not treat variables as evaluated.
-Furthermore, we only count a bottomingApp if the function is
-applied to more than n args. If so, we transform:
+\begin{code}
+exprIsValue :: CoreExpr -> Bool -- True => Value-lambda, constructor, PAP
+exprIsValue (Type ty) = True -- Types are honorary Values; we don't mind
+ -- copying them
+exprIsValue (Var v) = False
+exprIsValue (Lam b e) = isId b || exprIsValue e
+exprIsValue (Note _ e) = exprIsValue e
+exprIsValue (Let _ e) = False
+exprIsValue (Case _ _ _) = False
+exprIsValue (Con con _) = isWHNFCon con
+exprIsValue e@(App _ _) = case collectArgs e of
+ (Var v, args) -> fun_arity > valArgCount args
+ where
+ fun_arity = arityLowerBound (getIdArity v)
+ _ -> False
+\end{code}
- bottomingFn ty e1 ... en en+1 ... em
-to
- bottomingFn ty' e1 ... en
+exprIsWHNF reports True for head normal forms. Note that does not necessarily
+mean *normal* forms; constructors might have non-trivial argument expressions, for
+example. We use a let binding for WHNFs, rather than a case binding, even if it's
+used strictly. We try to expose WHNFs by floating lets out of the RHS of lets.
-That is, we discard en+1 .. em
+ We treat applications of buildId and augmentId as honorary WHNFs,
+ because we want them to get exposed.
+ [May 99: I've disabled this because it looks jolly dangerous:
+ we'll substitute inside lambda with potential big loss of sharing.]
\begin{code}
-maybeErrorApp :: GenCoreExpr bndr Id -- Expr to look at
- -> Maybe Type -- Just ty => a result type *already cloned*;
- -- Nothing => don't know result ty; we
- -- *pretend* that the result ty won't be
- -- primitive -- somebody later must
- -- ensure this.
- -> Maybe (GenCoreExpr bndr Id)
-
-maybeErrorApp expr result_ty_maybe
- = case collectArgs expr of
- (Var fun, (TypeArg ty : other_args))
- | isBottomingId fun
- && maybeToBool result_ty_maybe -- we *know* the result type
- -- (otherwise: live a fairy-tale existence...)
- && not (isPrimType result_ty) ->
- case splitSigmaTy (idType fun) of
- ([tyvar_tmpl], [], tau_ty) ->
- case (splitTyArgs tau_ty) of { (arg_tys, res_ty) ->
- let
- n_args_to_keep = length arg_tys
- args_to_keep = take n_args_to_keep other_args
- in
- if res_ty == mkTyVarTemplateTy tyvar_tmpl &&
- n_args_to_keep <= length other_args
- then
- -- Phew! We're in business
- Just (mkGenApp (Var fun)
- (TypeArg result_ty : args_to_keep))
- else
- Nothing
- }
-
- other -> -- Function type wrong shape
- Nothing
- other -> Nothing
- where
- Just result_ty = result_ty_maybe
+exprIsWHNF :: CoreExpr -> Bool -- True => Variable, value-lambda, constructor, PAP
+exprIsWHNF (Type ty) = True -- Types are honorary WHNFs; we don't mind
+ -- copying them
+exprIsWHNF (Var v) = True
+exprIsWHNF (Lam b e) = isId b || exprIsWHNF e
+exprIsWHNF (Note _ e) = exprIsWHNF e
+exprIsWHNF (Let _ e) = False
+exprIsWHNF (Case _ _ _) = False
+exprIsWHNF (Con con _) = isWHNFCon con
+exprIsWHNF e@(App _ _) = case collectArgs e of
+ (Var v, args) -> n_val_args == 0
+ || fun_arity > n_val_args
+-- [May 99: disabled. See note above] || v_uniq == buildIdKey
+-- || v_uniq == augmentIdKey
+ where
+ n_val_args = valArgCount args
+ fun_arity = arityLowerBound (getIdArity v)
+ v_uniq = idUnique v
+
+ _ -> False
\end{code}
\begin{code}
-squashableDictishCcExpr :: CostCentre -> GenCoreExpr a b -> Bool
-
-squashableDictishCcExpr cc expr
- = if not (isDictCC cc) then
- False -- that was easy...
- else
- squashable expr -- note: quite like the "atomic_rhs" stuff in simplifier
- where
- squashable (Var _) = True
- squashable (CoTyApp f _) = squashable f
- squashable (Con _ _ _) = True -- I think so... WDP 94/09
- squashable (Prim _ _ _) = True -- ditto
- squashable other = False
--}
+exprArity :: CoreExpr -> Int -- How many value lambdas are at the top
+exprArity (Lam b e) | isTyVar b = exprArity e
+ | otherwise = 1 + exprArity e
+exprArity other = 0
\end{code}
+
%************************************************************************
%* *
-\subsection{Core-renaming utils}
+\subsection{Equality}
%* *
%************************************************************************
-\begin{code}
-substCoreExpr :: ValEnv
- -> TypeEnv -- TyVar=>Type
- -> CoreExpr
- -> UniqSM CoreExpr
-
-substCoreExpr venv tenv expr
- -- if the envs are empty, then avoid doing anything
- = if (isNullIdEnv venv && isNullTyVarEnv tenv) then
- returnUs expr
- else
- do_CoreExpr venv tenv expr
-\end{code}
-
-The equiv code for @Types@ is in @TyUtils@.
-
-Because binders aren't necessarily unique: we don't do @plusEnvs@
-(which check for duplicates); rather, we use the shadowing version,
-@growIdEnv@ (and shorthand @addOneToIdEnv@).
-
-@do_CoreBindings@ takes into account the semantics of a list of
-@CoreBindings@---things defined early in the list are visible later in
-the list, but not vice versa.
+@cheapEqExpr@ is a cheap equality test which bales out fast!
+ True => definitely equal
+ False => may or may not be equal
\begin{code}
-type ValEnv = IdEnv CoreExpr
-
-do_CoreBindings :: ValEnv
- -> TypeEnv
- -> [CoreBinding]
- -> UniqSM [CoreBinding]
-
-do_CoreBinding :: ValEnv
- -> TypeEnv
- -> CoreBinding
- -> UniqSM (CoreBinding, ValEnv)
-
-do_CoreBindings venv tenv [] = returnUs []
-do_CoreBindings venv tenv (b:bs)
- = do_CoreBinding venv tenv b `thenUs` \ (new_b, new_venv) ->
- do_CoreBindings new_venv tenv bs `thenUs` \ new_bs ->
- returnUs (new_b : new_bs)
-
-do_CoreBinding venv tenv (NonRec binder rhs)
- = do_CoreExpr venv tenv rhs `thenUs` \ new_rhs ->
+cheapEqExpr :: Expr b -> Expr b -> Bool
- dup_binder tenv binder `thenUs` \ (new_binder, (old, new)) ->
- -- now plug new bindings into envs
- let new_venv = addOneToIdEnv venv old new in
+cheapEqExpr (Var v1) (Var v2) = v1==v2
+cheapEqExpr (Con con1 args1) (Con con2 args2)
+ = con1 == con2 &&
+ and (zipWithEqual "cheapEqExpr" cheapEqExpr args1 args2)
- returnUs (NonRec new_binder new_rhs, new_venv)
+cheapEqExpr (App f1 a1) (App f2 a2)
+ = f1 `cheapEqExpr` f2 && a1 `cheapEqExpr` a2
-do_CoreBinding venv tenv (Rec binds)
- = -- for letrec, we plug in new bindings BEFORE cloning rhss
- mapAndUnzipUs (dup_binder tenv) binders `thenUs` \ (new_binders, new_maps) ->
- let new_venv = growIdEnvList venv new_maps in
+cheapEqExpr (Type t1) (Type t2) = t1 == t2
- mapUs (do_CoreExpr new_venv tenv) rhss `thenUs` \ new_rhss ->
- returnUs (Rec (new_binders `zipEqual` new_rhss), new_venv)
- where
- (binders, rhss) = unzip binds
+cheapEqExpr _ _ = False
\end{code}
-\begin{code}
-do_CoreArg :: ValEnv
- -> TypeEnv
- -> CoreArg
- -> UniqSM CoreExpr
-
-do_CoreArg venv tenv (LitArg lit) = returnUs (Lit lit)
-do_CoreArg venv tenv (TyArg ty) = panic "do_CoreArg: TyArg"
-do_CoreArg venv tenv (UsageArg usage) = panic "do_CoreArg: UsageArg"
-do_CoreArg venv tenv (VarArg v)
- = returnUs (
- case (lookupIdEnv venv v) of
- Nothing -> --false:ASSERT(toplevelishId v)
- Var v
- Just expr -> expr
- )
-\end{code}
\begin{code}
-do_CoreExpr :: ValEnv
- -> TypeEnv
- -> CoreExpr
- -> UniqSM CoreExpr
-
-do_CoreExpr venv tenv orig_expr@(Var var)
- = returnUs (
- case (lookupIdEnv venv var) of
- Nothing -> --false:ASSERT(toplevelishId var) (SIGH)
- orig_expr
- Just expr -> expr
- )
-
-do_CoreExpr venv tenv e@(Lit _) = returnUs e
-
-do_CoreExpr venv tenv (Con con as)
- = panic "CoreUtils.do_CoreExpr:Con"
-{- LATER:
- = mapUs (do_CoreArg venv tenv) as `thenUs` \ new_as ->
- mkCoCon con new_as
--}
-
-do_CoreExpr venv tenv (Prim op as)
- = panic "CoreUtils.do_CoreExpr:Prim"
-{- LATER:
- = mapUs (do_CoreArg venv tenv) as `thenUs` \ new_as ->
- do_PrimOp op `thenUs` \ new_op ->
- mkCoPrim new_op new_as
+eqExpr :: CoreExpr -> CoreExpr -> Bool
+ -- Works ok at more general type, but only needed at CoreExpr
+eqExpr e1 e2
+ = eq emptyVarEnv e1 e2
where
- do_PrimOp (CCallOp label is_asm may_gc arg_tys result_ty)
- = let
- new_arg_tys = map (applyTypeEnvToTy tenv) arg_tys
- new_result_ty = applyTypeEnvToTy tenv result_ty
- in
- returnUs (CCallOp label is_asm may_gc new_arg_tys new_result_ty)
-
- do_PrimOp other_op = returnUs other_op
--}
-
-do_CoreExpr venv tenv (Lam binder expr)
- = dup_binder tenv binder `thenUs` \(new_binder, (old,new)) ->
- let new_venv = addOneToIdEnv venv old new in
- do_CoreExpr new_venv tenv expr `thenUs` \ new_expr ->
- returnUs (Lam new_binder new_expr)
-
-do_CoreExpr venv tenv (App expr arg)
- = panic "CoreUtils.do_CoreExpr:App"
-{-
- = do_CoreExpr venv tenv expr `thenUs` \ new_expr ->
- do_CoreArg venv tenv arg `thenUs` \ new_arg ->
- mkCoApp new_expr new_arg
--}
-
-do_CoreExpr venv tenv (Case expr alts)
- = do_CoreExpr venv tenv expr `thenUs` \ new_expr ->
- do_alts venv tenv alts `thenUs` \ new_alts ->
- returnUs (Case new_expr new_alts)
- where
- do_alts venv tenv (AlgAlts alts deflt)
- = mapUs (do_boxed_alt venv tenv) alts `thenUs` \ new_alts ->
- do_default venv tenv deflt `thenUs` \ new_deflt ->
- returnUs (AlgAlts new_alts new_deflt)
- where
- do_boxed_alt venv tenv (con, binders, expr)
- = mapAndUnzipUs (dup_binder tenv) binders `thenUs` \ (new_binders, new_vmaps) ->
- let new_venv = growIdEnvList venv new_vmaps in
- do_CoreExpr new_venv tenv expr `thenUs` \ new_expr ->
- returnUs (con, new_binders, new_expr)
-
-
- do_alts venv tenv (PrimAlts alts deflt)
- = mapUs (do_unboxed_alt venv tenv) alts `thenUs` \ new_alts ->
- do_default venv tenv deflt `thenUs` \ new_deflt ->
- returnUs (PrimAlts new_alts new_deflt)
- where
- do_unboxed_alt venv tenv (lit, expr)
- = do_CoreExpr venv tenv expr `thenUs` \ new_expr ->
- returnUs (lit, new_expr)
-
- do_default venv tenv NoDefault = returnUs NoDefault
-
- do_default venv tenv (BindDefault binder expr)
- = dup_binder tenv binder `thenUs` \ (new_binder, (old, new)) ->
- let new_venv = addOneToIdEnv venv old new in
- do_CoreExpr new_venv tenv expr `thenUs` \ new_expr ->
- returnUs (BindDefault new_binder new_expr)
-
-do_CoreExpr venv tenv (Let core_bind expr)
- = do_CoreBinding venv tenv core_bind `thenUs` \ (new_bind, new_venv) ->
- -- and do the body of the let
- do_CoreExpr new_venv tenv expr `thenUs` \ new_expr ->
- returnUs (Let new_bind new_expr)
-
-do_CoreExpr venv tenv (SCC label expr)
- = do_CoreExpr venv tenv expr `thenUs` \ new_expr ->
- returnUs (SCC label new_expr)
+ -- The "env" maps variables in e1 to variables in ty2
+ -- So when comparing lambdas etc,
+ -- we in effect substitute v2 for v1 in e1 before continuing
+ eq env (Var v1) (Var v2) = case lookupVarEnv env v1 of
+ Just v1' -> v1' == v2
+ Nothing -> v1 == v2
+
+ eq env (Con c1 es1) (Con c2 es2) = c1 == c2 && eq_list env es1 es2
+ eq env (App f1 a1) (App f2 a2) = eq env f1 f2 && eq env a1 a2
+ eq env (Lam v1 e1) (Lam v2 e2) = eq (extendVarEnv env v1 v2) e1 e2
+ eq env (Let (NonRec v1 r1) e1)
+ (Let (NonRec v2 r2) e2) = eq env r1 r2 && eq (extendVarEnv env v1 v2) e1 e2
+ eq env (Let (Rec ps1) e1)
+ (Let (Rec ps2) e2) = length ps1 == length ps2 &&
+ and (zipWith eq_rhs ps1 ps2) &&
+ eq env' e1 e2
+ where
+ env' = extendVarEnvList env [(v1,v2) | ((v1,_),(v2,_)) <- zip ps1 ps2]
+ eq_rhs (_,r1) (_,r2) = eq env' r1 r2
+ eq env (Case e1 v1 a1)
+ (Case e2 v2 a2) = eq env e1 e2 &&
+ length a1 == length a2 &&
+ and (zipWith (eq_alt env') a1 a2)
+ where
+ env' = extendVarEnv env v1 v2
+
+ eq env (Note n1 e1) (Note n2 e2) = eq_note env n1 n2 && eq env e1 e2
+ eq env (Type t1) (Type t2) = t1 == t2
+ eq env e1 e2 = False
+
+ eq_list env [] [] = True
+ eq_list env (e1:es1) (e2:es2) = eq env e1 e2 && eq_list env es1 es2
+ eq_list env es1 es2 = False
+
+ eq_alt env (c1,vs1,r1) (c2,vs2,r2) = c1==c2 &&
+ eq (extendVarEnvList env (vs1 `zip` vs2)) r1 r2
+
+ eq_note env (SCC cc1) (SCC cc2) = cc1 == cc2
+ eq_note env (Coerce f1 t1) (Coerce f2 t2) = f1==f2 && t1==t2
+ eq_note env InlineCall InlineCall = True
+ eq_note env other1 other2 = False
\end{code}
+
projects / ghc-hetmet.git / blobdiff