X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2FcoreSyn%2FCoreUtils.lhs;h=379da8aef3c4cc44bc60ce53385b5f8b416b8319;hp=b79837919fec928ca2d183acfee9c85b1e9b68fd;hb=4bc25e8c30559b7a6a87b39afcc79340ae778788;hpb=71cad0e1783707f325973a537b3b0a74300bd866 diff --git a/compiler/coreSyn/CoreUtils.lhs b/compiler/coreSyn/CoreUtils.lhs index b798379..379da8a 100644 --- a/compiler/coreSyn/CoreUtils.lhs +++ b/compiler/coreSyn/CoreUtils.lhs @@ -1,94 +1,81 @@ % +% (c) The University of Glasgow 2006 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % -\section[CoreUtils]{Utility functions on @Core@ syntax} + +Utility functions on @Core@ syntax \begin{code} +{-# OPTIONS -fno-warn-incomplete-patterns #-} +-- The above warning supression flag is a temporary kludge. +-- While working on this module you are encouraged to remove it and fix +-- any warnings in the module. See +-- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings +-- for details + +-- | Commonly useful utilites for manipulating the Core language module CoreUtils ( - -- Construction - mkInlineMe, mkSCC, mkCoerce, + -- * Constructing expressions + mkInlineMe, mkSCC, mkCoerce, mkCoerceI, bindNonRec, needsCaseBinding, - mkIfThenElse, mkAltExpr, mkPiType, mkPiTypes, + mkAltExpr, mkPiType, mkPiTypes, - -- Taking expressions apart - findDefault, findAlt, isDefaultAlt, mergeAlts, + -- * Taking expressions apart + findDefault, findAlt, isDefaultAlt, mergeAlts, trimConArgs, - -- Properties of expressions - exprType, coreAltType, - exprIsDupable, exprIsTrivial, exprIsCheap, + -- * Properties of expressions + exprType, coreAltType, coreAltsType, + exprIsDupable, exprIsTrivial, exprIsCheap, exprIsExpandable, exprIsHNF,exprOkForSpeculation, exprIsBig, exprIsConApp_maybe, exprIsBottom, rhsIsStatic, - -- Arity and eta expansion - manifestArity, exprArity, - exprEtaExpandArity, etaExpand, - - -- Size - coreBindsSize, + -- * Expression and bindings size + coreBindsSize, exprSize, - -- Hashing + -- * Hashing hashExpr, - -- Equality - cheapEqExpr, tcEqExpr, tcEqExprX, applyTypeToArgs, applyTypeToArg, + -- * Equality + cheapEqExpr, + -- * Manipulating data constructors and types + applyTypeToArgs, applyTypeToArg, dataConOrigInstPat, dataConRepInstPat, dataConRepFSInstPat ) where #include "HsVersions.h" - -import GLAEXTS -- For `xori` - import CoreSyn -import CoreFVs ( exprFreeVars ) -import PprCore ( pprCoreExpr ) -import Var ( Var, TyVar, CoVar, isCoVar, tyVarKind, setVarUnique, - mkCoVar, mkTyVar, mkCoVar ) -import OccName ( OccName, occNameFS, mkVarOccFS ) -import VarSet ( unionVarSet ) +import PprCore +import Var +import SrcLoc import VarEnv -import Name ( hashName, mkSysTvName ) +import Name +import Module #if mingw32_TARGET_OS -import Packages ( isDllName ) +import Packages #endif -import Literal ( hashLiteral, literalType, litIsDupable, - litIsTrivial, isZeroLit, Literal( MachLabel ) ) -import DataCon ( DataCon, dataConRepArity, eqSpecPreds, - isVanillaDataCon, dataConTyCon, dataConRepArgTys, - dataConUnivTyVars, dataConExTyVars, dataConEqSpec, - dataConOrigArgTys ) -import PrimOp ( PrimOp(..), primOpOkForSpeculation, primOpIsCheap ) -import Id ( Id, idType, globalIdDetails, idNewStrictness, - mkWildId, idArity, idName, idUnfolding, idInfo, - isOneShotBndr, isStateHackType, isDataConWorkId_maybe, mkSysLocal, - isDataConWorkId, isBottomingId, isDictId - ) -import IdInfo ( GlobalIdDetails(..), megaSeqIdInfo ) -import NewDemand ( appIsBottom ) -import Type ( Type, mkFunTy, mkForAllTy, splitFunTy_maybe, - splitFunTy, tcEqTypeX, - applyTys, isUnLiftedType, seqType, mkTyVarTy, - splitForAllTy_maybe, isForAllTy, splitRecNewType_maybe, - splitTyConApp_maybe, coreEqType, funResultTy, applyTy, - substTyWith, mkPredTy - ) -import Coercion ( Coercion, mkTransCoercion, coercionKind, - splitNewTypeRepCo_maybe, mkSymCoercion, mkLeftCoercion, - mkRightCoercion, decomposeCo, coercionKindPredTy, - splitCoercionKind, mkEqPred ) -import TyCon ( tyConArity ) -import TysWiredIn ( boolTy, trueDataCon, falseDataCon ) -import CostCentre ( CostCentre ) -import BasicTypes ( Arity ) -import PackageConfig ( PackageId ) -import Unique ( Unique ) +import Literal +import DataCon +import PrimOp +import Id +import IdInfo +import NewDemand +import Type +import Coercion +import TyCon +import CostCentre +import Unique import Outputable -import DynFlags ( DynFlags, DynFlag(Opt_DictsCheap), dopt ) -import TysPrim ( alphaTy ) -- Debugging only -import Util ( equalLength, lengthAtLeast, foldl2 ) -import FastString ( FastString ) +import TysPrim +import FastString +import Maybes +import Util +import Data.Word +import Data.Bits + +import GHC.Exts -- For `xori` \end{code} @@ -100,15 +87,16 @@ import FastString ( FastString ) \begin{code} exprType :: CoreExpr -> Type - -exprType (Var var) = idType var -exprType (Lit lit) = literalType lit -exprType (Let _ body) = exprType body -exprType (Case _ _ ty alts) = ty -exprType (Cast e co) - = let (_, ty) = coercionKind co in ty -exprType (Note other_note e) = exprType e -exprType (Lam binder expr) = mkPiType binder (exprType expr) +-- ^ Recover the type of a well-typed Core expression. Fails when +-- applied to the actual 'CoreSyn.Type' expression as it cannot +-- really be said to have a type +exprType (Var var) = idType var +exprType (Lit lit) = literalType lit +exprType (Let _ body) = exprType body +exprType (Case _ _ ty _) = ty +exprType (Cast _ co) = snd (coercionKind co) +exprType (Note _ e) = exprType e +exprType (Lam binder expr) = mkPiType binder (exprType expr) exprType e@(App _ _) = case collectArgs e of (fun, args) -> applyTypeToArgs e (exprType fun) args @@ -116,35 +104,39 @@ exprType e@(App _ _) exprType other = pprTrace "exprType" (pprCoreExpr other) alphaTy coreAltType :: CoreAlt -> Type +-- ^ Returns the type of the alternatives right hand side coreAltType (_,_,rhs) = exprType rhs -\end{code} -@mkPiType@ makes a (->) type or a forall type, depending on whether -it is given a type variable or a term variable. We cleverly use the -lbvarinfo field to figure out the right annotation for the arrove in -case of a term variable. +coreAltsType :: [CoreAlt] -> Type +-- ^ Returns the type of the first alternative, which should be the same as for all alternatives +coreAltsType (alt:_) = coreAltType alt +coreAltsType [] = panic "corAltsType" +\end{code} \begin{code} -mkPiType :: Var -> Type -> Type -- The more polymorphic version -mkPiTypes :: [Var] -> Type -> Type -- doesn't work... - -mkPiTypes vs ty = foldr mkPiType ty vs +mkPiType :: Var -> Type -> Type +-- ^ Makes a @(->)@ type or a forall type, depending +-- on whether it is given a type variable or a term variable. +mkPiTypes :: [Var] -> Type -> Type +-- ^ 'mkPiType' for multiple type or value arguments mkPiType v ty | isId v = mkFunTy (idType v) ty | otherwise = mkForAllTy v ty + +mkPiTypes vs ty = foldr mkPiType ty vs \end{code} \begin{code} applyTypeToArg :: Type -> CoreExpr -> Type +-- ^ Determines the type resulting from applying an expression to a function with the given type applyTypeToArg fun_ty (Type arg_ty) = applyTy fun_ty arg_ty -applyTypeToArg fun_ty other_arg = funResultTy fun_ty +applyTypeToArg fun_ty _ = funResultTy fun_ty applyTypeToArgs :: CoreExpr -> Type -> [CoreExpr] -> Type --- A more efficient version of applyTypeToArg --- when we have several args --- The first argument is just for debugging -applyTypeToArgs e op_ty [] = op_ty +-- ^ A more efficient version of 'applyTypeToArg' when we have several arguments. +-- The first argument is just for debugging, and gives some context +applyTypeToArgs _ op_ty [] = op_ty applyTypeToArgs e op_ty (Type ty : args) = -- Accumulate type arguments so we can instantiate all at once @@ -153,15 +145,18 @@ applyTypeToArgs e op_ty (Type ty : args) go rev_tys (Type ty : args) = go (ty:rev_tys) args go rev_tys rest_args = applyTypeToArgs e op_ty' rest_args where - op_ty' = applyTys op_ty (reverse rev_tys) + op_ty' = applyTysD msg op_ty (reverse rev_tys) + msg = ptext (sLit "applyTypeToArgs") <+> + panic_msg e op_ty -applyTypeToArgs e op_ty (other_arg : args) +applyTypeToArgs e op_ty (_ : args) = case (splitFunTy_maybe op_ty) of Just (_, res_ty) -> applyTypeToArgs e res_ty args - Nothing -> pprPanic "applyTypeToArgs" (pprCoreExpr e $$ ppr op_ty) -\end{code} - + Nothing -> pprPanic "applyTypeToArgs" (panic_msg e op_ty) +panic_msg :: CoreExpr -> Type -> SDoc +panic_msg e op_ty = pprCoreExpr e $$ ppr op_ty +\end{code} %************************************************************************ %* * @@ -202,22 +197,29 @@ its rhs is trivial) and *then* we could get rid of the inline_me. But it hardly seems worth it, so I don't bother. \begin{code} +-- | Wraps the given expression in an inlining hint unless the expression +-- is trivial in some sense, so that doing so would usually hurt us +mkInlineMe :: CoreExpr -> CoreExpr mkInlineMe (Var v) = Var v mkInlineMe e = Note InlineMe e \end{code} - - \begin{code} +-- | Wrap the given expression in the coercion, dropping identity coercions and coalescing nested coercions +mkCoerceI :: CoercionI -> CoreExpr -> CoreExpr +mkCoerceI IdCo e = e +mkCoerceI (ACo co) e = mkCoerce co e + +-- | Wrap the given expression in the coercion safely, coalescing nested coercions mkCoerce :: Coercion -> CoreExpr -> CoreExpr mkCoerce co (Cast expr co2) - = ASSERT(let { (from_ty, to_ty) = coercionKind co; - (from_ty2, to_ty2) = coercionKind co2} in + = ASSERT(let { (from_ty, _to_ty) = coercionKind co; + (_from_ty2, to_ty2) = coercionKind co2} in from_ty `coreEqType` to_ty2 ) mkCoerce (mkTransCoercion co2 co) expr mkCoerce co expr - = let (from_ty, to_ty) = coercionKind co in + = let (from_ty, _to_ty) = coercionKind co in -- if to_ty `coreEqType` from_ty -- then expr -- else @@ -226,10 +228,12 @@ mkCoerce co expr \end{code} \begin{code} +-- | Wraps the given expression in the cost centre unless +-- in a way that maximises their utility to the user mkSCC :: CostCentre -> Expr b -> Expr b -- Note: Nested SCC's *are* preserved for the benefit of -- cost centre stack profiling -mkSCC cc (Lit lit) = Lit lit +mkSCC _ (Lit lit) = Lit lit mkSCC cc (Lam x e) = Lam x (mkSCC cc e) -- Move _scc_ inside lambda mkSCC cc (Note (SCC cc') e) = Note (SCC cc) (Note (SCC cc') e) mkSCC cc (Note n e) = Note n (mkSCC cc e) -- Move _scc_ inside notes @@ -246,20 +250,27 @@ mkSCC cc expr = Note (SCC cc) expr \begin{code} bindNonRec :: Id -> CoreExpr -> CoreExpr -> CoreExpr --- (bindNonRec x r b) produces either --- let x = r in b --- or --- case r of x { _DEFAULT_ -> b } +-- ^ @bindNonRec x r b@ produces either: +-- +-- > let x = r in b -- --- depending on whether x is unlifted or not +-- or: +-- +-- > case r of x { _DEFAULT_ -> b } +-- +-- depending on whether we have to use a @case@ or @let@ +-- binding for the expression (see 'needsCaseBinding'). -- It's used by the desugarer to avoid building bindings --- that give Core Lint a heart attack. Actually the simplifier --- deals with them perfectly well. - +-- that give Core Lint a heart attack, although actually +-- the simplifier deals with them perfectly well. See +-- also 'MkCore.mkCoreLet' bindNonRec bndr rhs body - | needsCaseBinding (idType bndr) rhs = Case rhs bndr (exprType body) [(DEFAULT,[],body)] + | needsCaseBinding (idType bndr) rhs = Case rhs bndr (exprType body) [(DEFAULT, [], body)] | otherwise = Let (NonRec bndr rhs) body +-- | Tests whether we have to use a @case@ rather than @let@ binding for this expression +-- as per the invariants of 'CoreExpr': see "CoreSyn#let_app_invariant" +needsCaseBinding :: Type -> CoreExpr -> Bool needsCaseBinding ty rhs = isUnLiftedType ty && not (exprOkForSpeculation rhs) -- Make a case expression instead of a let -- These can arise either from the desugarer, @@ -267,20 +278,18 @@ needsCaseBinding ty rhs = isUnLiftedType ty && not (exprOkForSpeculation rhs) \end{code} \begin{code} -mkAltExpr :: AltCon -> [CoreBndr] -> [Type] -> CoreExpr - -- This guy constructs the value that the scrutinee must have - -- when you are in one particular branch of a case +mkAltExpr :: AltCon -- ^ Case alternative constructor + -> [CoreBndr] -- ^ Things bound by the pattern match + -> [Type] -- ^ The type arguments to the case alternative + -> CoreExpr +-- ^ This guy constructs the value that the scrutinee must have +-- given that you are in one particular branch of a case mkAltExpr (DataAlt con) args inst_tys = mkConApp con (map Type inst_tys ++ varsToCoreExprs args) mkAltExpr (LitAlt lit) [] [] = Lit lit - -mkIfThenElse :: CoreExpr -> CoreExpr -> CoreExpr -> CoreExpr -mkIfThenElse guard then_expr else_expr --- Not going to be refining, so okay to take the type of the "then" clause - = Case guard (mkWildId boolTy) (exprType then_expr) - [ (DataAlt falseDataCon, [], else_expr), -- Increasing order of tag! - (DataAlt trueDataCon, [], then_expr) ] +mkAltExpr (LitAlt _) _ _ = panic "mkAltExpr LitAlt" +mkAltExpr DEFAULT _ _ = panic "mkAltExpr DEFAULT" \end{code} @@ -294,15 +303,18 @@ The default alternative must be first, if it exists at all. This makes it easy to find, though it makes matching marginally harder. \begin{code} +-- | Extract the default case alternative findDefault :: [CoreAlt] -> ([CoreAlt], Maybe CoreExpr) findDefault ((DEFAULT,args,rhs) : alts) = ASSERT( null args ) (alts, Just rhs) findDefault alts = (alts, Nothing) +-- | Find the case alternative corresponding to a particular +-- constructor: panics if no such constructor exists findAlt :: AltCon -> [CoreAlt] -> CoreAlt findAlt con alts = case alts of (deflt@(DEFAULT,_,_):alts) -> go alts deflt - other -> go alts panic_deflt + _ -> go alts panic_deflt where panic_deflt = pprPanic "Missing alternative" (ppr con $$ vcat (map ppr alts)) @@ -315,12 +327,12 @@ findAlt con alts isDefaultAlt :: CoreAlt -> Bool isDefaultAlt (DEFAULT, _, _) = True -isDefaultAlt other = False +isDefaultAlt _ = False --------------------------------- mergeAlts :: [CoreAlt] -> [CoreAlt] -> [CoreAlt] --- Merge preserving order; alternatives in the first arg --- shadow ones in the second +-- ^ Merge alternatives preserving order; alternatives in +-- the first argument shadow ones in the second mergeAlts [] as2 = as2 mergeAlts as1 [] = as1 mergeAlts (a1:as1) (a2:as2) @@ -328,6 +340,21 @@ mergeAlts (a1:as1) (a2:as2) LT -> a1 : mergeAlts as1 (a2:as2) EQ -> a1 : mergeAlts as1 as2 -- Discard a2 GT -> a2 : mergeAlts (a1:as1) as2 + + +--------------------------------- +trimConArgs :: AltCon -> [CoreArg] -> [CoreArg] +-- ^ Given: +-- +-- > case (C a b x y) of +-- > C b x y -> ... +-- +-- We want to drop the leading type argument of the scrutinee +-- leaving the arguments to match agains the pattern + +trimConArgs DEFAULT args = ASSERT( null args ) [] +trimConArgs (LitAlt _) args = ASSERT( null args ) [] +trimConArgs (DataAlt dc) args = dropList (dataConUnivTyVars dc) args \end{code} @@ -342,14 +369,11 @@ mergeAlts (a1:as1) (a2:as2) applications. Note that primop Ids aren't considered trivial unless -@exprIsBottom@ is true of expressions that are guaranteed to diverge - - There used to be a gruesome test for (hasNoBinding v) in the Var case: exprIsTrivial (Var v) | hasNoBinding v = idArity v == 0 -The idea here is that a constructor worker, like $wJust, is -really short for (\x -> $wJust x), becuase $wJust has no binding. +The idea here is that a constructor worker, like \$wJust, is +really short for (\x -> \$wJust x), becuase \$wJust has no binding. So it should be treated like a lambda. Ditto unsaturated primops. But now constructor workers are not "have-no-binding" Ids. And completely un-applied primops and foreign-call Ids are sufficiently @@ -362,15 +386,16 @@ SCC notes. We do not treat (_scc_ "foo" x) as trivial, because b) see the note [SCC-and-exprIsTrivial] in Simplify.simplLazyBind \begin{code} -exprIsTrivial (Var v) = True -- See notes above -exprIsTrivial (Type _) = True -exprIsTrivial (Lit lit) = litIsTrivial lit -exprIsTrivial (App e arg) = not (isRuntimeArg arg) && exprIsTrivial e -exprIsTrivial (Note (SCC _) e) = False -- See notes above +exprIsTrivial :: CoreExpr -> Bool +exprIsTrivial (Var _) = True -- See notes above +exprIsTrivial (Type _) = True +exprIsTrivial (Lit lit) = litIsTrivial lit +exprIsTrivial (App e arg) = not (isRuntimeArg arg) && exprIsTrivial e +exprIsTrivial (Note (SCC _) _) = False -- See notes above exprIsTrivial (Note _ e) = exprIsTrivial e -exprIsTrivial (Cast e co) = exprIsTrivial e -exprIsTrivial (Lam b body) = not (isRuntimeVar b) && exprIsTrivial body -exprIsTrivial other = False +exprIsTrivial (Cast e _) = exprIsTrivial e +exprIsTrivial (Lam b body) = not (isRuntimeVar b) && exprIsTrivial body +exprIsTrivial _ = False \end{code} @@ -386,20 +411,21 @@ exprIsTrivial other = False \begin{code} -exprIsDupable (Type _) = True -exprIsDupable (Var v) = True -exprIsDupable (Lit lit) = litIsDupable lit -exprIsDupable (Note InlineMe e) = True +exprIsDupable :: CoreExpr -> Bool +exprIsDupable (Type _) = True +exprIsDupable (Var _) = True +exprIsDupable (Lit lit) = litIsDupable lit +exprIsDupable (Note InlineMe _) = True exprIsDupable (Note _ e) = exprIsDupable e -exprIsDupable (Cast e co) = exprIsDupable e -exprIsDupable expr +exprIsDupable (Cast e _) = exprIsDupable e +exprIsDupable expr = go expr 0 where - go (Var v) n_args = True + go (Var _) _ = True go (App f a) n_args = n_args < dupAppSize && exprIsDupable a && go f (n_args+1) - go other n_args = False + go _ _ = False dupAppSize :: Int dupAppSize = 4 -- Size of application we are prepared to duplicate @@ -434,50 +460,51 @@ 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} -exprIsCheap :: CoreExpr -> Bool -exprIsCheap (Lit lit) = True -exprIsCheap (Type _) = True -exprIsCheap (Var _) = True -exprIsCheap (Note InlineMe e) = True -exprIsCheap (Note _ e) = exprIsCheap e -exprIsCheap (Cast e co) = exprIsCheap e -exprIsCheap (Lam x e) = isRuntimeVar x || exprIsCheap e -exprIsCheap (Case e _ _ alts) = exprIsCheap e && - and [exprIsCheap rhs | (_,_,rhs) <- alts] +exprIsCheap' :: (Id -> Bool) -> CoreExpr -> Bool +exprIsCheap' _ (Lit _) = True +exprIsCheap' _ (Type _) = True +exprIsCheap' _ (Var _) = True +exprIsCheap' _ (Note InlineMe _) = True +exprIsCheap' is_conlike (Note _ e) = exprIsCheap' is_conlike e +exprIsCheap' is_conlike (Cast e _) = exprIsCheap' is_conlike e +exprIsCheap' is_conlike (Lam x e) = isRuntimeVar x + || exprIsCheap' is_conlike e +exprIsCheap' is_conlike (Case e _ _ alts) = exprIsCheap' is_conlike e && + and [exprIsCheap' is_conlike rhs | (_,_,rhs) <- alts] -- Experimentally, treat (case x of ...) as cheap -- (and case __coerce x etc.) -- This improves arities of overloaded functions where -- there is only dictionary selection (no construction) involved -exprIsCheap (Let (NonRec x _) e) - | isUnLiftedType (idType x) = exprIsCheap e +exprIsCheap' is_conlike (Let (NonRec x _) e) + | isUnLiftedType (idType x) = exprIsCheap' is_conlike e | otherwise = False -- strict lets always have cheap right hand sides, -- and do no allocation. -exprIsCheap other_expr -- Applications and variables +exprIsCheap' is_conlike other_expr -- Applications and variables = go other_expr [] where -- Accumulate value arguments, then decide go (App f a) val_args | isRuntimeArg a = go f (a:val_args) | otherwise = go f val_args - go (Var f) [] = True -- Just a type application of a variable + go (Var _) [] = True -- Just a type application of a variable -- (f t1 t2 t3) counts as WHNF go (Var f) args - = case globalIdDetails f of - RecordSelId {} -> go_sel args - ClassOpId _ -> go_sel args - PrimOpId op -> go_primop op args + = case idDetails f of + RecSelId {} -> go_sel args + ClassOpId _ -> go_sel args + PrimOpId op -> go_primop op args - DataConWorkId _ -> go_pap args - other | length args < idArity f -> go_pap args + _ | is_conlike f -> go_pap args + | length args < idArity f -> go_pap args - other -> isBottomingId f + _ -> isBottomingId f -- Application of a function which -- always gives bottom; we treat this as cheap -- because it certainly doesn't need to be shared! - go other args = False + go _ _ = False -------------- go_pap args = all exprIsTrivial args @@ -487,62 +514,74 @@ exprIsCheap other_expr -- Applications and variables -- We'll put up with one constructor application, but not dozens -------------- - go_primop op args = primOpIsCheap op && all exprIsCheap args + go_primop op args = primOpIsCheap op && all (exprIsCheap' is_conlike) args -- In principle we should worry about primops -- that return a type variable, since the result -- might be applied to something, but I'm not going -- to bother to check the number of args -------------- - go_sel [arg] = exprIsCheap arg -- I'm experimenting with making record selection - go_sel other = False -- look cheap, so we will substitute it inside a + go_sel [arg] = exprIsCheap' is_conlike arg -- I'm experimenting with making record selection + go_sel _ = False -- look cheap, so we will substitute it inside a -- lambda. Particularly for dictionary field selection. -- BUT: Take care with (sel d x)! The (sel d) might be cheap, but -- there's no guarantee that (sel d x) will be too. Hence (n_val_args == 1) -\end{code} - -exprOkForSpeculation returns True of an expression that it is - - * safe to evaluate even if normal order eval might not - evaluate the expression at all, or - - * safe *not* to evaluate even if normal order would do so - -It returns True iff - the expression guarantees to terminate, - soon, - without raising an exception, - without causing a side effect (e.g. writing a mutable variable) - -NB: if exprIsHNF e, then exprOkForSpecuation e - -E.G. - let x = case y# +# 1# of { r# -> I# r# } - in E -==> - case y# +# 1# of { r# -> - let x = I# r# - in E - } +exprIsCheap :: CoreExpr -> Bool +exprIsCheap = exprIsCheap' isDataConWorkId -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. +exprIsExpandable :: CoreExpr -> Bool +exprIsExpandable = exprIsCheap' isConLikeId +\end{code} \begin{code} +-- | 'exprOkForSpeculation' returns True of an expression that is: +-- +-- * Safe to evaluate even if normal order eval might not +-- evaluate the expression at all, or +-- +-- * Safe /not/ to evaluate even if normal order would do so +-- +-- Precisely, it returns @True@ iff: +-- +-- * The expression guarantees to terminate, +-- +-- * soon, +-- +-- * without raising an exception, +-- +-- * without causing a side effect (e.g. writing a mutable variable) +-- +-- Note that if @exprIsHNF e@, then @exprOkForSpecuation e@. +-- As an example of the considerations in this test, consider: +-- +-- > let x = case y# +# 1# of { r# -> I# r# } +-- > in E +-- +-- being translated to: +-- +-- > case y# +# 1# of { r# -> +-- > let x = I# r# +-- > in E +-- > } +-- +-- 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. exprOkForSpeculation :: CoreExpr -> Bool exprOkForSpeculation (Lit _) = True exprOkForSpeculation (Type _) = True + -- Tick boxes are *not* suitable for speculation exprOkForSpeculation (Var v) = isUnLiftedType (idType v) + && not (isTickBoxOp v) exprOkForSpeculation (Note _ e) = exprOkForSpeculation e -exprOkForSpeculation (Cast e co) = exprOkForSpeculation e +exprOkForSpeculation (Cast e _) = exprOkForSpeculation e exprOkForSpeculation other_expr = case collectArgs other_expr of - (Var f, args) -> spec_ok (globalIdDetails f) args - other -> False + (Var f, args) -> spec_ok (idDetails f) args + _ -> False where - spec_ok (DataConWorkId _) args + spec_ok (DataConWorkId _) _ = True -- The strictness of the constructor has already -- been expressed by its "wrapper", so we don't need -- to take the arguments into account @@ -560,11 +599,10 @@ exprOkForSpeculation other_expr -- A bit conservative: we don't really need -- to care about lazy arguments, but this is easy - spec_ok other args = False + spec_ok _ _ = False +-- | True of dyadic operators that can fail only if the second arg is zero! isDivOp :: PrimOp -> Bool --- True of dyadic operators that can fail --- only if the second arg is zero -- This function probably belongs in PrimOp, or even in -- an automagically generated file.. but it's such a -- special case I thought I'd leave it here for now. @@ -576,53 +614,59 @@ isDivOp IntegerQuotRemOp = True isDivOp IntegerDivModOp = True isDivOp FloatDivOp = True isDivOp DoubleDivOp = True -isDivOp other = False +isDivOp _ = False \end{code} - \begin{code} -exprIsBottom :: CoreExpr -> Bool -- True => definitely bottom +-- | True of expressions that are guaranteed to diverge upon execution +exprIsBottom :: CoreExpr -> Bool exprIsBottom e = go 0 e - where - -- n is the number of args - go n (Note _ e) = go n e - go n (Cast e co) = 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 (Lit _) = False - go n (Lam _ _) = False - go n (Type _) = False + where + -- n is the number of args + go n (Note _ e) = go n e + go n (Cast e _) = go n e + go n (Let _ e) = go n e + go _ (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 _ (Lit _) = False + go _ (Lam _ _) = False + go _ (Type _) = False idAppIsBottom :: Id -> Int -> Bool idAppIsBottom id n_val_args = appIsBottom (idNewStrictness id) n_val_args \end{code} -@exprIsHNF@ returns true for expressions that are certainly *already* -evaluated to *head* normal form. This is used to decide whether it's ok -to change - - case x of _ -> e ===> e - -and to decide whether it's safe to discard a `seq` - -So, it does *not* treat variables as evaluated, unless they say they are. - -But it *does* treat partial applications and constructor applications -as values, even if their arguments are non-trivial, provided the argument -type is lifted; - e.g. (:) (f x) (map f xs) is a value - map (...redex...) is a value -Because `seq` on such things completes immediately - -For unlifted argument types, we have to be careful: - C (f x :: Int#) -Suppose (f x) diverges; then C (f x) is not a value. True, but -this form is illegal (see the invariants in CoreSyn). Args of unboxed -type must be ok-for-speculation (or trivial). - \begin{code} + +-- | This returns true for expressions that are certainly /already/ +-- evaluated to /head/ normal form. This is used to decide whether it's ok +-- to change: +-- +-- > case x of _ -> e +-- +-- into: +-- +-- > e +-- +-- and to decide whether it's safe to discard a 'seq'. +-- So, it does /not/ treat variables as evaluated, unless they say they are. +-- However, it /does/ treat partial applications and constructor applications +-- as values, even if their arguments are non-trivial, provided the argument +-- type is lifted. For example, both of these are values: +-- +-- > (:) (f x) (map f xs) +-- > map (...redex...) +-- +-- Because 'seq' on such things completes immediately. +-- +-- For unlifted argument types, we have to be careful: +-- +-- > C (f x :: Int#) +-- +-- Suppose @f x@ diverges; then @C (f x)@ is not a value. However this can't +-- happen: see "CoreSyn#let_app_invariant". This invariant states that arguments of +-- unboxed type must be ok-for-speculation (or trivial). exprIsHNF :: CoreExpr -> Bool -- True => Value-lambda, constructor, PAP exprIsHNF (Var v) -- NB: There are no value args at this point = isDataConWorkId v -- Catches nullary constructors, @@ -633,57 +677,39 @@ exprIsHNF (Var v) -- NB: There are no value args at this point -- A worry: what if an Id's unfolding is just itself: -- then we could get an infinite loop... -exprIsHNF (Lit l) = True -exprIsHNF (Type ty) = True -- Types are honorary Values; - -- we don't mind copying them -exprIsHNF (Lam b e) = isRuntimeVar b || exprIsHNF e -exprIsHNF (Note _ e) = exprIsHNF e -exprIsHNF (Cast e co) = exprIsHNF e +exprIsHNF (Lit _) = True +exprIsHNF (Type _) = True -- Types are honorary Values; + -- we don't mind copying them +exprIsHNF (Lam b e) = isRuntimeVar b || exprIsHNF e +exprIsHNF (Note _ e) = exprIsHNF e +exprIsHNF (Cast e _) = exprIsHNF e exprIsHNF (App e (Type _)) = exprIsHNF e exprIsHNF (App e a) = app_is_value e [a] -exprIsHNF other = False +exprIsHNF _ = False -- There is at least one value argument +app_is_value :: CoreExpr -> [CoreArg] -> Bool app_is_value (Var fun) args - | isDataConWorkId fun -- Constructor apps are values - || idArity fun > valArgCount args -- Under-applied function - = check_args (idType fun) args -app_is_value (App f a) as = app_is_value f (a:as) -app_is_value other as = False - - -- 'check_args' checks that unlifted-type args - -- are in fact guaranteed non-divergent -check_args fun_ty [] = True -check_args fun_ty (Type _ : args) = case splitForAllTy_maybe fun_ty of - Just (_, ty) -> check_args ty args -check_args fun_ty (arg : args) - | isUnLiftedType arg_ty = exprOkForSpeculation arg - | otherwise = check_args res_ty args - where - (arg_ty, res_ty) = splitFunTy fun_ty + = idArity fun > valArgCount args -- Under-applied function + || isDataConWorkId fun -- or data constructor +app_is_value (Note _ f) as = app_is_value f as +app_is_value (Cast f _) as = app_is_value f as +app_is_value (App f a) as = app_is_value f (a:as) +app_is_value _ _ = False \end{code} +These InstPat functions go here to avoid circularity between DataCon and Id + \begin{code} --- deep applies a TyConApp coercion as a substitution to a reflexive coercion --- deepCast t [a1,...,an] co corresponds to deep(t, [a1,...,an], co) from --- FC paper -deepCast :: Type -> [TyVar] -> Coercion -> Coercion -deepCast ty tyVars co - = ASSERT( let {(lty, rty) = coercionKind co; - Just (tc1, lArgs) = splitTyConApp_maybe lty; - Just (tc2, rArgs) = splitTyConApp_maybe rty} - in - tc1 == tc2 && length lArgs == length rArgs && - length lArgs == length tyVars ) - substTyWith tyVars coArgs ty - where - -- coArgs = [right (left (left co)), right (left co), right co] - coArgs = decomposeCo (length tyVars) co +dataConRepInstPat, dataConOrigInstPat :: [Unique] -> DataCon -> [Type] -> ([TyVar], [CoVar], [Id]) +dataConRepFSInstPat :: [FastString] -> [Unique] -> DataCon -> [Type] -> ([TyVar], [CoVar], [Id]) --- These InstPat functions go here to avoid circularity between DataCon and Id -dataConOrigInstPat = dataConInstPat dataConOrigArgTys (repeat (FSLIT("ipv"))) -dataConRepInstPat = dataConInstPat dataConRepArgTys (repeat (FSLIT("ipv"))) +dataConRepInstPat = dataConInstPat dataConRepArgTys (repeat ((fsLit "ipv"))) dataConRepFSInstPat = dataConInstPat dataConRepArgTys +dataConOrigInstPat = dataConInstPat dc_arg_tys (repeat ((fsLit "ipv"))) + where + dc_arg_tys dc = map mkPredTy (dataConEqTheta dc) ++ map mkPredTy (dataConDictTheta dc) ++ dataConOrigArgTys dc + -- Remember to include the existential dictionaries dataConInstPat :: (DataCon -> [Type]) -- function used to find arg tys -> [FastString] -- A long enough list of FSs to use for names @@ -691,16 +717,20 @@ dataConInstPat :: (DataCon -> [Type]) -- function used to find arg tys -> DataCon -> [Type] -- Types to instantiate the universally quantified tyvars -> ([TyVar], [CoVar], [Id]) -- Return instantiated variables --- dataConInstPat arg_fun us fss con inst_tys returns a triple +-- dataConInstPat arg_fun fss us con inst_tys returns a triple -- (ex_tvs, co_tvs, arg_ids), -- -- ex_tvs are intended to be used as binders for existential type args -- -- co_tvs are intended to be used as binders for coercion args and the kinds -- of these vars have been instantiated by the inst_tys and the ex_tys +-- The co_tvs include both GADT equalities (dcEqSpec) and +-- programmer-specified equalities (dcEqTheta) -- --- arg_ids are indended to be used as binders for value arguments, including --- dicts, and have their types instantiated with inst_tys and ex_tys +-- arg_ids are indended to be used as binders for value arguments, +-- and their types have been instantiated with inst_tys and ex_tys +-- The arg_ids include both dicts (dcDictTheta) and +-- programmer-specified arguments (after rep-ing) (deRepArgTys) -- -- Example. -- The following constructor T1 @@ -710,27 +740,27 @@ dataConInstPat :: (DataCon -> [Type]) -- function used to find arg tys -- ... -- -- has representation type --- forall a. forall a1. forall a2. forall b. (a :=: (a1,a2)) => +-- forall a. forall a1. forall b. (a ~ (a1,b)) => -- Int -> b -> T a -- --- dataConInstPat us T1 (a1',a2') will return +-- dataConInstPat fss us T1 (a1',b') will return -- --- ([a1'', a2'', b''],[c :: (a1',a2'):=:(a1'',a2'')],[x :: Int,y :: b'']) +-- ([a1'', b''], [c :: (a1', b')~(a1'', b'')], [x :: Int, y :: b'']) -- --- where the double-primed variables are created from the unique list input --- getting names from the FS list input +-- where the double-primed variables are created with the FastStrings and +-- Uniques given as fss and us dataConInstPat arg_fun fss uniqs con inst_tys - = (ex_bndrs, co_bndrs, id_bndrs) + = (ex_bndrs, co_bndrs, arg_ids) where univ_tvs = dataConUnivTyVars con ex_tvs = dataConExTyVars con arg_tys = arg_fun con eq_spec = dataConEqSpec con - eq_preds = eqSpecPreds eq_spec + eq_theta = dataConEqTheta con + eq_preds = eqSpecPreds eq_spec ++ eq_theta n_ex = length ex_tvs - n_co = length eq_spec - n_id = length arg_tys + n_co = length eq_preds -- split the Uniques and FastStrings (ex_uniqs, uniqs') = splitAt n_ex uniqs @@ -739,98 +769,115 @@ dataConInstPat arg_fun fss uniqs con inst_tys (ex_fss, fss') = splitAt n_ex fss (co_fss, id_fss) = splitAt n_co fss' - -- make existential type variables + -- Make existential type variables + ex_bndrs = zipWith3 mk_ex_var ex_uniqs ex_fss ex_tvs mk_ex_var uniq fs var = mkTyVar new_name kind where new_name = mkSysTvName uniq fs kind = tyVarKind var - ex_bndrs = zipWith3 mk_ex_var ex_uniqs ex_fss ex_tvs + -- Make the instantiating substitution + subst = zipOpenTvSubst (univ_tvs ++ ex_tvs) (inst_tys ++ map mkTyVarTy ex_bndrs) - -- make the instantiation substitution - inst_subst = substTyWith (univ_tvs ++ ex_tvs) (inst_tys ++ map mkTyVarTy ex_bndrs) - - -- make new coercion vars, instantiating kind - mk_co_var uniq fs eq_pred = mkCoVar new_name (inst_subst (mkPredTy eq_pred)) + -- Make new coercion vars, instantiating kind + co_bndrs = zipWith3 mk_co_var co_uniqs co_fss eq_preds + mk_co_var uniq fs eq_pred = mkCoVar new_name co_kind where new_name = mkSysTvName uniq fs - - co_bndrs = zipWith3 mk_co_var co_uniqs co_fss eq_preds + co_kind = substTy subst (mkPredTy eq_pred) -- make value vars, instantiating types - mk_id_var uniq fs ty = mkUserLocal (mkVarOccFS fs) uniq (inst_subst ty) noSrcLoc - id_bndrs = zipWith3 mk_id_var id_uniqs id_fss arg_tys + mk_id_var uniq fs ty = mkUserLocal (mkVarOccFS fs) uniq (substTy subst ty) noSrcSpan + arg_ids = zipWith3 mk_id_var id_uniqs id_fss arg_tys +-- | Returns @Just (dc, [x1..xn])@ if the argument expression is +-- a constructor application of the form @dc x1 .. xn@ exprIsConApp_maybe :: CoreExpr -> Maybe (DataCon, [CoreExpr]) --- Returns (Just (dc, [x1..xn])) if the argument expression is --- a constructor application of the form (dc x1 .. xn) - exprIsConApp_maybe (Cast expr co) - = -- Maybe this is over the top, but here we try to turn - -- coerce (S,T) ( x, y ) - -- effectively into - -- ( coerce S x, coerce T y ) - -- This happens in anger in PrelArrExts which has a coerce - -- case coerce memcpy a b of - -- (# r, s #) -> ... - -- where the memcpy is in the IO monad, but the call is in - -- the (ST s) monad + = -- Here we do the KPush reduction rule as described in the FC paper case exprIsConApp_maybe expr of { - Nothing -> Nothing ; - Just (dc, args) -> - - let (from_ty, to_ty) = coercionKind co in - + Nothing -> Nothing ; + Just (dc, dc_args) -> + + -- The transformation applies iff we have + -- (C e1 ... en) `cast` co + -- where co :: (T t1 .. tn) ~ (T s1 ..sn) + -- That is, with a T at the top of both sides + -- The left-hand one must be a T, because exprIsConApp returned True + -- but the right-hand one might not be. (Though it usually will.) + + let (from_ty, to_ty) = coercionKind co + (from_tc, from_tc_arg_tys) = splitTyConApp from_ty + -- The inner one must be a TyConApp + in case splitTyConApp_maybe to_ty of { Nothing -> Nothing ; - Just (tc, tc_arg_tys) | tc /= dataConTyCon dc -> Nothing - -- | not (isVanillaDataCon dc) -> Nothing - | otherwise -> - -- Type constructor must match datacon - - case splitTyConApp_maybe from_ty of { - Nothing -> Nothing ; - Just (tc', tc_arg_tys') | tc /= tc' -> Nothing - -- Both sides of coercion must have the same type constructor - | otherwise -> - + Just (to_tc, to_tc_arg_tys) + | from_tc /= to_tc -> Nothing + -- These two Nothing cases are possible; we might see + -- (C x y) `cast` (g :: T a ~ S [a]), + -- where S is a type function. In fact, exprIsConApp + -- will probably not be called in such circumstances, + -- but there't nothing wrong with it + + | otherwise -> let - -- here we do the PushC reduction rule as described in the FC paper - arity = tyConArity tc - n_ex_tvs = length dc_ex_tyvars + tc_arity = tyConArity from_tc - (univ_args, rest) = splitAt arity args - (ex_args, val_args) = splitAt n_ex_tvs rest + (univ_args, rest1) = splitAt tc_arity dc_args + (ex_args, rest2) = splitAt n_ex_tvs rest1 + (co_args_spec, rest3) = splitAt n_cos_spec rest2 + (co_args_theta, val_args) = splitAt n_cos_theta rest3 arg_tys = dataConRepArgTys dc - dc_tyvars = dataConUnivTyVars dc + dc_univ_tyvars = dataConUnivTyVars dc dc_ex_tyvars = dataConExTyVars dc - - deep arg_ty = deepCast arg_ty dc_tyvars co - - -- first we appropriately cast the value arguments - arg_cos = map deep arg_tys - new_val_args = zipWith mkCoerce (map deep arg_tys) val_args - - -- then we cast the existential coercion arguments - orig_tvs = dc_tyvars ++ dc_ex_tyvars - gammas = decomposeCo arity co - new_tys = gammas ++ (map (\ (Type t) -> t) ex_args) - theta = substTyWith orig_tvs new_tys - cast_ty tv (Type ty) - | isCoVar tv - , (ty1, ty2) <- splitCoercionKind (tyVarKind tv) - = Type $ mkTransCoercion (mkSymCoercion (theta ty1)) - (mkTransCoercion ty (theta ty2)) - | otherwise - = Type ty - new_ex_args = zipWith cast_ty dc_ex_tyvars ex_args + dc_eq_spec = dataConEqSpec dc + dc_eq_theta = dataConEqTheta dc + dc_tyvars = dc_univ_tyvars ++ dc_ex_tyvars + n_ex_tvs = length dc_ex_tyvars + n_cos_spec = length dc_eq_spec + n_cos_theta = length dc_eq_theta + + -- Make the "theta" from Fig 3 of the paper + gammas = decomposeCo tc_arity co + new_tys = gammas ++ map (\ (Type t) -> t) ex_args + theta = zipOpenTvSubst dc_tyvars new_tys + + -- First we cast the existential coercion arguments + cast_co_spec (tv, ty) co + = cast_co_theta (mkEqPred (mkTyVarTy tv, ty)) co + cast_co_theta eqPred (Type co) + | (ty1, ty2) <- getEqPredTys eqPred + = Type $ mkSymCoercion (substTy theta ty1) + `mkTransCoercion` co + `mkTransCoercion` (substTy theta ty2) + new_co_args = zipWith cast_co_spec dc_eq_spec co_args_spec ++ + zipWith cast_co_theta dc_eq_theta co_args_theta + -- ...and now value arguments + new_val_args = zipWith cast_arg arg_tys val_args + cast_arg arg_ty arg = mkCoerce (substTy theta arg_ty) arg + in - ASSERT( all isTypeArg (take arity args) ) - ASSERT( equalLength val_args arg_tys ) - Just (dc, map Type tc_arg_tys ++ new_ex_args ++ new_val_args) - }}} + ASSERT( length univ_args == tc_arity ) + ASSERT( from_tc == dataConTyCon dc ) + ASSERT( and (zipWith coreEqType [t | Type t <- univ_args] from_tc_arg_tys) ) + ASSERT( all isTypeArg (univ_args ++ ex_args) ) + ASSERT2( equalLength val_args arg_tys, ppr dc $$ ppr dc_tyvars $$ ppr dc_ex_tyvars $$ ppr arg_tys $$ ppr dc_args $$ ppr univ_args $$ ppr ex_args $$ ppr val_args $$ ppr arg_tys ) + + Just (dc, map Type to_tc_arg_tys ++ ex_args ++ new_co_args ++ new_val_args) + }} + +{- +-- We do not want to tell the world that we have a +-- Cons, to *stop* Case of Known Cons, which removes +-- the TickBox. +exprIsConApp_maybe (Note (TickBox {}) expr) + = Nothing +exprIsConApp_maybe (Note (BinaryTickBox {}) expr) + = Nothing +-} exprIsConApp_maybe (Note _ expr) = exprIsConApp_maybe expr @@ -857,387 +904,26 @@ exprIsConApp_maybe expr = analyse (collectArgs expr) -- we are effectively duplicating the unfolding analyse (Var fun, []) | let unf = idUnfolding fun, - isCheapUnfolding unf + isExpandableUnfolding unf = exprIsConApp_maybe (unfoldingTemplate unf) - analyse other = Nothing + analyse _ = Nothing \end{code} %************************************************************************ %* * -\subsection{Eta reduction and expansion} -%* * -%************************************************************************ - -\begin{code} -exprEtaExpandArity :: DynFlags -> CoreExpr -> Arity -{- The Arity returned is the number of value args the - thing can be applied to without doing much work - -exprEtaExpandArity is used when eta expanding - e ==> \xy -> e x y - -It returns 1 (or more) to: - case x of p -> \s -> ... -because for I/O ish things we really want to get that \s to the top. -We are prepared to evaluate x each time round the loop in order to get that - -It's all a bit more subtle than it looks: - -1. One-shot lambdas - -Consider one-shot lambdas - let x = expensive in \y z -> E -We want this to have arity 2 if the \y-abstraction is a 1-shot lambda -Hence the ArityType returned by arityType - -2. The state-transformer hack - -The one-shot lambda special cause is particularly important/useful for -IO state transformers, where we often get - let x = E in \ s -> ... - -and the \s is a real-world state token abstraction. Such abstractions -are almost invariably 1-shot, so we want to pull the \s out, past the -let x=E, even if E is expensive. So we treat state-token lambdas as -one-shot even if they aren't really. The hack is in Id.isOneShotBndr. - -3. Dealing with bottom - -Consider also - f = \x -> error "foo" -Here, arity 1 is fine. But if it is - f = \x -> case x of - True -> error "foo" - False -> \y -> x+y -then we want to get arity 2. Tecnically, this isn't quite right, because - (f True) `seq` 1 -should diverge, but it'll converge if we eta-expand f. Nevertheless, we -do so; it improves some programs significantly, and increasing convergence -isn't a bad thing. Hence the ABot/ATop in ArityType. - -Actually, the situation is worse. Consider - f = \x -> case x of - True -> \y -> x+y - False -> \y -> x-y -Can we eta-expand here? At first the answer looks like "yes of course", but -consider - (f bot) `seq` 1 -This should diverge! But if we eta-expand, it won't. Again, we ignore this -"problem", because being scrupulous would lose an important transformation for -many programs. - - -4. Newtypes - -Non-recursive newtypes are transparent, and should not get in the way. -We do (currently) eta-expand recursive newtypes too. So if we have, say - - newtype T = MkT ([T] -> Int) - -Suppose we have - e = coerce T f -where f has arity 1. Then: etaExpandArity e = 1; -that is, etaExpandArity looks through the coerce. - -When we eta-expand e to arity 1: eta_expand 1 e T -we want to get: coerce T (\x::[T] -> (coerce ([T]->Int) e) x) - -HOWEVER, note that if you use coerce bogusly you can ge - coerce Int negate -And since negate has arity 2, you might try to eta expand. But you can't -decopose Int to a function type. Hence the final case in eta_expand. --} - - -exprEtaExpandArity dflags e = arityDepth (arityType dflags e) - --- A limited sort of function type -data ArityType = AFun Bool ArityType -- True <=> one-shot - | ATop -- Know nothing - | ABot -- Diverges - -arityDepth :: ArityType -> Arity -arityDepth (AFun _ ty) = 1 + arityDepth ty -arityDepth ty = 0 - -andArityType ABot at2 = at2 -andArityType ATop at2 = ATop -andArityType (AFun t1 at1) (AFun t2 at2) = AFun (t1 && t2) (andArityType at1 at2) -andArityType at1 at2 = andArityType at2 at1 - -arityType :: DynFlags -> CoreExpr -> ArityType - -- (go1 e) = [b1,..,bn] - -- means expression can be rewritten \x_b1 -> ... \x_bn -> body - -- where bi is True <=> the lambda is one-shot - -arityType dflags (Note n e) = arityType dflags e --- Not needed any more: etaExpand is cleverer --- | ok_note n = arityType dflags e --- | otherwise = ATop - -arityType dflags (Cast e co) = arityType dflags e - -arityType dflags (Var v) - = mk (idArity v) (arg_tys (idType v)) - where - mk :: Arity -> [Type] -> ArityType - -- The argument types are only to steer the "state hack" - -- Consider case x of - -- True -> foo - -- False -> \(s:RealWorld) -> e - -- where foo has arity 1. Then we want the state hack to - -- apply to foo too, so we can eta expand the case. - mk 0 tys | isBottomingId v = ABot - | (ty:tys) <- tys, isStateHackType ty = AFun True ATop - | otherwise = ATop - mk n (ty:tys) = AFun (isStateHackType ty) (mk (n-1) tys) - mk n [] = AFun False (mk (n-1) []) - - arg_tys :: Type -> [Type] -- Ignore for-alls - arg_tys ty - | Just (_, ty') <- splitForAllTy_maybe ty = arg_tys ty' - | Just (arg,res) <- splitFunTy_maybe ty = arg : arg_tys res - | otherwise = [] - - -- Lambdas; increase arity -arityType dflags (Lam x e) - | isId x = AFun (isOneShotBndr x) (arityType dflags e) - | otherwise = arityType dflags e - - -- Applications; decrease arity -arityType dflags (App f (Type _)) = arityType dflags f -arityType dflags (App f a) = case arityType dflags f of - AFun one_shot xs | exprIsCheap a -> xs - other -> ATop - - -- Case/Let; keep arity if either the expression is cheap - -- or it's a 1-shot lambda - -- The former is not really right for Haskell - -- f x = case x of { (a,b) -> \y. e } - -- ===> - -- f x y = case x of { (a,b) -> e } - -- The difference is observable using 'seq' -arityType dflags (Case scrut _ _ alts) - = case foldr1 andArityType [arityType dflags rhs | (_,_,rhs) <- alts] of - xs | exprIsCheap scrut -> xs - xs@(AFun one_shot _) | one_shot -> AFun True ATop - other -> ATop - -arityType dflags (Let b e) - = case arityType dflags e of - xs | cheap_bind b -> xs - xs@(AFun one_shot _) | one_shot -> AFun True ATop - other -> ATop - where - cheap_bind (NonRec b e) = is_cheap (b,e) - cheap_bind (Rec prs) = all is_cheap prs - is_cheap (b,e) = (dopt Opt_DictsCheap dflags && isDictId b) - || exprIsCheap e - -- If the experimental -fdicts-cheap flag is on, we eta-expand through - -- dictionary bindings. This improves arities. Thereby, it also - -- means that full laziness is less prone to floating out the - -- application of a function to its dictionary arguments, which - -- can thereby lose opportunities for fusion. Example: - -- foo :: Ord a => a -> ... - -- foo = /\a \(d:Ord a). let d' = ...d... in \(x:a). .... - -- -- So foo has arity 1 - -- - -- f = \x. foo dInt $ bar x - -- - -- The (foo DInt) is floated out, and makes ineffective a RULE - -- foo (bar x) = ... - -- - -- One could go further and make exprIsCheap reply True to any - -- dictionary-typed expression, but that's more work. - -arityType dflags other = ATop - -{- NOT NEEDED ANY MORE: etaExpand is cleverer -ok_note InlineMe = False -ok_note other = True - -- Notice that we do not look through __inline_me__ - -- This may seem surprising, but consider - -- f = _inline_me (\x -> e) - -- We DO NOT want to eta expand this to - -- f = \x -> (_inline_me (\x -> e)) x - -- because the _inline_me gets dropped now it is applied, - -- giving just - -- f = \x -> e - -- A Bad Idea --} -\end{code} - - -\begin{code} -etaExpand :: Arity -- Result should have this number of value args - -> [Unique] - -> CoreExpr -> Type -- Expression and its type - -> CoreExpr --- (etaExpand n us e ty) returns an expression with --- the same meaning as 'e', but with arity 'n'. --- --- Given e' = etaExpand n us e ty --- We should have --- ty = exprType e = exprType e' --- --- Note that SCCs are not treated specially. If we have --- etaExpand 2 (\x -> scc "foo" e) --- = (\xy -> (scc "foo" e) y) --- So the costs of evaluating 'e' (not 'e y') are attributed to "foo" - -etaExpand n us expr ty - | manifestArity expr >= n = expr -- The no-op case - | otherwise - = eta_expand n us expr ty - where - --- manifestArity sees how many leading value lambdas there are -manifestArity :: CoreExpr -> Arity -manifestArity (Lam v e) | isId v = 1 + manifestArity e - | otherwise = manifestArity e -manifestArity (Note _ e) = manifestArity e -manifestArity (Cast e _) = manifestArity e -manifestArity e = 0 - --- etaExpand deals with for-alls. For example: --- etaExpand 1 E --- where E :: forall a. a -> a --- would return --- (/\b. \y::a -> E b y) --- --- It deals with coerces too, though they are now rare --- so perhaps the extra code isn't worth it - -eta_expand n us expr ty - | n == 0 && - -- The ILX code generator requires eta expansion for type arguments - -- too, but alas the 'n' doesn't tell us how many of them there - -- may be. So we eagerly eta expand any big lambdas, and just - -- cross our fingers about possible loss of sharing in the ILX case. - -- The Right Thing is probably to make 'arity' include - -- type variables throughout the compiler. (ToDo.) - not (isForAllTy ty) - -- Saturated, so nothing to do - = expr - - -- Short cut for the case where there already - -- is a lambda; no point in gratuitously adding more -eta_expand n us (Lam v body) ty - | isTyVar v - = Lam v (eta_expand n us body (applyTy ty (mkTyVarTy v))) - - | otherwise - = Lam v (eta_expand (n-1) us body (funResultTy ty)) - --- We used to have a special case that stepped inside Coerces here, --- thus: eta_expand n us (Note note@(Coerce _ ty) e) _ --- = Note note (eta_expand n us e ty) --- BUT this led to an infinite loop --- Example: newtype T = MkT (Int -> Int) --- eta_expand 1 (coerce (Int->Int) e) --- --> coerce (Int->Int) (eta_expand 1 T e) --- by the bogus eqn --- --> coerce (Int->Int) (coerce T --- (\x::Int -> eta_expand 1 (coerce (Int->Int) e))) --- by the splitNewType_maybe case below --- and round we go - -eta_expand n us expr ty - = ASSERT2 (exprType expr `coreEqType` ty, ppr (exprType expr) $$ ppr ty) - case splitForAllTy_maybe ty of { - Just (tv,ty') -> - - Lam lam_tv (eta_expand n us2 (App expr (Type (mkTyVarTy lam_tv))) (substTyWith [tv] [mkTyVarTy lam_tv] ty')) - where - lam_tv = mkTyVar (mkSysTvName uniq FSLIT("etaT")) (tyVarKind tv) - (uniq:us2) = us - ; Nothing -> - - case splitFunTy_maybe ty of { - Just (arg_ty, res_ty) -> Lam arg1 (eta_expand (n-1) us2 (App expr (Var arg1)) res_ty) - where - arg1 = mkSysLocal FSLIT("eta") uniq arg_ty - (uniq:us2) = us - - ; Nothing -> - - -- Given this: - -- newtype T = MkT ([T] -> Int) - -- Consider eta-expanding this - -- eta_expand 1 e T - -- We want to get - -- coerce T (\x::[T] -> (coerce ([T]->Int) e) x) - - case splitNewTypeRepCo_maybe ty of { - Just(ty1,co) -> - mkCoerce co (eta_expand n us (mkCoerce (mkSymCoercion co) expr) ty1) ; - Nothing -> - - -- We have an expression of arity > 0, but its type isn't a function - -- This *can* legitmately happen: e.g. coerce Int (\x. x) - -- Essentially the programmer is playing fast and loose with types - -- (Happy does this a lot). So we simply decline to eta-expand. - expr - }}} -\end{code} - -exprArity is a cheap-and-cheerful version of exprEtaExpandArity. -It tells how many things the expression can be applied to before doing -any work. It doesn't look inside cases, lets, etc. The idea is that -exprEtaExpandArity will do the hard work, leaving something that's easy -for exprArity to grapple with. In particular, Simplify uses exprArity to -compute the ArityInfo for the Id. - -Originally I thought that it was enough just to look for top-level lambdas, but -it isn't. I've seen this - - foo = PrelBase.timesInt - -We want foo to get arity 2 even though the eta-expander will leave it -unchanged, in the expectation that it'll be inlined. But occasionally it -isn't, because foo is blacklisted (used in a rule). - -Similarly, see the ok_note check in exprEtaExpandArity. So - f = __inline_me (\x -> e) -won't be eta-expanded. - -And in any case it seems more robust to have exprArity be a bit more intelligent. -But note that (\x y z -> f x y z) -should have arity 3, regardless of f's arity. - -\begin{code} -exprArity :: CoreExpr -> Arity -exprArity e = go e - where - go (Var v) = idArity v - go (Lam x e) | isId x = go e + 1 - | otherwise = go e - go (Note n e) = go e - go (Cast e _) = go e - go (App e (Type t)) = go e - go (App f a) | exprIsCheap a = (go f - 1) `max` 0 - -- NB: exprIsCheap a! - -- f (fac x) does not have arity 2, - -- even if f has arity 3! - -- NB: `max 0`! (\x y -> f x) has arity 2, even if f is - -- unknown, hence arity 0 - go _ = 0 -\end{code} - -%************************************************************************ -%* * \subsection{Equality} %* * %************************************************************************ -@cheapEqExpr@ is a cheap equality test which bales out fast! - True => definitely equal - False => may or may not be equal - \begin{code} +-- | A cheap equality test which bales out fast! +-- If it returns @True@ the arguments are definitely equal, +-- otherwise, they may or may not be equal. +-- +-- See also 'exprIsBig' cheapEqExpr :: Expr b -> Expr b -> Bool cheapEqExpr (Var v1) (Var v2) = v1==v2 @@ -1247,63 +933,22 @@ cheapEqExpr (Type t1) (Type t2) = t1 `coreEqType` t2 cheapEqExpr (App f1 a1) (App f2 a2) = f1 `cheapEqExpr` f2 && a1 `cheapEqExpr` a2 +cheapEqExpr (Cast e1 t1) (Cast e2 t2) + = e1 `cheapEqExpr` e2 && t1 `coreEqCoercion` t2 + cheapEqExpr _ _ = False exprIsBig :: Expr b -> Bool --- Returns True of expressions that are too big to be compared by cheapEqExpr +-- ^ Returns @True@ of expressions that are too big to be compared by 'cheapEqExpr' exprIsBig (Lit _) = False -exprIsBig (Var v) = False -exprIsBig (Type t) = False +exprIsBig (Var _) = False +exprIsBig (Type _) = False exprIsBig (App f a) = exprIsBig f || exprIsBig a -exprIsBig other = True +exprIsBig (Cast e _) = exprIsBig e -- Hopefully coercions are not too big! +exprIsBig _ = True \end{code} -\begin{code} -tcEqExpr :: CoreExpr -> CoreExpr -> Bool --- Used in rule matching, so does *not* look through --- newtypes, predicate types; hence tcEqExpr - -tcEqExpr e1 e2 = tcEqExprX rn_env e1 e2 - where - rn_env = mkRnEnv2 (mkInScopeSet (exprFreeVars e1 `unionVarSet` exprFreeVars e2)) - -tcEqExprX :: RnEnv2 -> CoreExpr -> CoreExpr -> Bool -tcEqExprX env (Var v1) (Var v2) = rnOccL env v1 == rnOccR env v2 -tcEqExprX env (Lit lit1) (Lit lit2) = lit1 == lit2 -tcEqExprX env (App f1 a1) (App f2 a2) = tcEqExprX env f1 f2 && tcEqExprX env a1 a2 -tcEqExprX env (Lam v1 e1) (Lam v2 e2) = tcEqExprX (rnBndr2 env v1 v2) e1 e2 -tcEqExprX env (Let (NonRec v1 r1) e1) - (Let (NonRec v2 r2) e2) = tcEqExprX env r1 r2 - && tcEqExprX (rnBndr2 env v1 v2) e1 e2 -tcEqExprX env (Let (Rec ps1) e1) - (Let (Rec ps2) e2) = equalLength ps1 ps2 - && and (zipWith eq_rhs ps1 ps2) - && tcEqExprX env' e1 e2 - where - env' = foldl2 rn_bndr2 env ps2 ps2 - rn_bndr2 env (b1,_) (b2,_) = rnBndr2 env b1 b2 - eq_rhs (_,r1) (_,r2) = tcEqExprX env' r1 r2 -tcEqExprX env (Case e1 v1 t1 a1) - (Case e2 v2 t2 a2) = tcEqExprX env e1 e2 - && tcEqTypeX env t1 t2 - && equalLength a1 a2 - && and (zipWith (eq_alt env') a1 a2) - where - env' = rnBndr2 env v1 v2 - -tcEqExprX env (Note n1 e1) (Note n2 e2) = eq_note env n1 n2 && tcEqExprX env e1 e2 -tcEqExprX env (Cast e1 co1) (Cast e2 co2) = tcEqTypeX env co1 co2 && tcEqExprX env e1 e2 -tcEqExprX env (Type t1) (Type t2) = tcEqTypeX env t1 t2 -tcEqExprX env e1 e2 = False - -eq_alt env (c1,vs1,r1) (c2,vs2,r2) = c1==c2 && tcEqExprX (rnBndrs2 env vs1 vs2) r1 r2 - -eq_note env (SCC cc1) (SCC cc2) = cc1 == cc2 -eq_note env (CoreNote s1) (CoreNote s2) = s1 == s2 -eq_note env other1 other2 = False -\end{code} - %************************************************************************ %* * @@ -1316,8 +961,8 @@ coreBindsSize :: [CoreBind] -> Int coreBindsSize bs = foldr ((+) . bindSize) 0 bs exprSize :: CoreExpr -> Int - -- A measure of the size of the expressions - -- It also forces the expression pretty drastically as a side effect +-- ^ A measure of the size of the expressions, strictly greater than 0 +-- It also forces the expression pretty drastically as a side effect exprSize (Var v) = v `seq` 1 exprSize (Lit lit) = lit `seq` 1 exprSize (App f a) = exprSize f + exprSize a @@ -1328,23 +973,28 @@ exprSize (Cast e co) = (seqType co `seq` 1) + exprSize e exprSize (Note n e) = noteSize n + exprSize e exprSize (Type t) = seqType t `seq` 1 +noteSize :: Note -> Int noteSize (SCC cc) = cc `seq` 1 noteSize InlineMe = 1 noteSize (CoreNote s) = s `seq` 1 -- hdaume: core annotations - + varSize :: Var -> Int varSize b | isTyVar b = 1 | otherwise = seqType (idType b) `seq` megaSeqIdInfo (idInfo b) `seq` 1 -varsSize = foldr ((+) . varSize) 0 +varsSize :: [Var] -> Int +varsSize = sum . map varSize +bindSize :: CoreBind -> Int bindSize (NonRec b e) = varSize b + exprSize e bindSize (Rec prs) = foldr ((+) . pairSize) 0 prs +pairSize :: (Var, CoreExpr) -> Int pairSize (b,e) = varSize b + exprSize e +altSize :: CoreAlt -> Int altSize (c,bs,e) = c `seq` varsSize bs + exprSize e \end{code} @@ -1357,39 +1007,60 @@ altSize (c,bs,e) = c `seq` varsSize bs + exprSize e \begin{code} hashExpr :: CoreExpr -> Int --- Two expressions that hash to the same Int may be equal (but may not be) --- Two expressions that hash to the different Ints are definitely unequal +-- ^ Two expressions that hash to the same @Int@ may be equal (but may not be) +-- Two expressions that hash to the different Ints are definitely unequal. +-- +-- The emphasis is on a crude, fast hash, rather than on high precision. -- --- But "unequal" here means "not identical"; two alpha-equivalent --- expressions may hash to the different Ints +-- But unequal here means \"not identical\"; two alpha-equivalent +-- expressions may hash to the different Ints. -- --- The emphasis is on a crude, fast hash, rather than on high precision - -hashExpr e | hash < 0 = 77 -- Just in case we hit -maxInt - | otherwise = hash - where - hash = abs (hash_expr e) -- Negative numbers kill UniqFM - -hash_expr (Note _ e) = hash_expr e -hash_expr (Cast e co) = hash_expr e -hash_expr (Let (NonRec b r) e) = hashId b -hash_expr (Let (Rec ((b,r):_)) e) = hashId b -hash_expr (Case _ b _ _) = hashId b -hash_expr (App f e) = hash_expr f * fast_hash_expr e -hash_expr (Var v) = hashId v -hash_expr (Lit lit) = hashLiteral lit -hash_expr (Lam b _) = hashId b -hash_expr (Type t) = trace "hash_expr: type" 1 -- Shouldn't happen - -fast_hash_expr (Var v) = hashId v -fast_hash_expr (Lit lit) = hashLiteral lit -fast_hash_expr (App f (Type _)) = fast_hash_expr f -fast_hash_expr (App f a) = fast_hash_expr a -fast_hash_expr (Lam b _) = hashId b -fast_hash_expr other = 1 - -hashId :: Id -> Int -hashId id = hashName (idName id) +-- We must be careful that @\\x.x@ and @\\y.y@ map to the same hash code, +-- (at least if we want the above invariant to be true). + +hashExpr e = fromIntegral (hash_expr (1,emptyVarEnv) e .&. 0x7fffffff) + -- UniqFM doesn't like negative Ints + +type HashEnv = (Int, VarEnv Int) -- Hash code for bound variables + +hash_expr :: HashEnv -> CoreExpr -> Word32 +-- Word32, because we're expecting overflows here, and overflowing +-- signed types just isn't cool. In C it's even undefined. +hash_expr env (Note _ e) = hash_expr env e +hash_expr env (Cast e _) = hash_expr env e +hash_expr env (Var v) = hashVar env v +hash_expr _ (Lit lit) = fromIntegral (hashLiteral lit) +hash_expr env (App f e) = hash_expr env f * fast_hash_expr env e +hash_expr env (Let (NonRec b r) e) = hash_expr (extend_env env b) e * fast_hash_expr env r +hash_expr env (Let (Rec ((b,_):_)) e) = hash_expr (extend_env env b) e +hash_expr env (Case e _ _ _) = hash_expr env e +hash_expr env (Lam b e) = hash_expr (extend_env env b) e +hash_expr _ (Type _) = WARN(True, text "hash_expr: type") 1 +-- Shouldn't happen. Better to use WARN than trace, because trace +-- prevents the CPR optimisation kicking in for hash_expr. + +fast_hash_expr :: HashEnv -> CoreExpr -> Word32 +fast_hash_expr env (Var v) = hashVar env v +fast_hash_expr env (Type t) = fast_hash_type env t +fast_hash_expr _ (Lit lit) = fromIntegral (hashLiteral lit) +fast_hash_expr env (Cast e _) = fast_hash_expr env e +fast_hash_expr env (Note _ e) = fast_hash_expr env e +fast_hash_expr env (App _ a) = fast_hash_expr env a -- A bit idiosyncratic ('a' not 'f')! +fast_hash_expr _ _ = 1 + +fast_hash_type :: HashEnv -> Type -> Word32 +fast_hash_type env ty + | Just tv <- getTyVar_maybe ty = hashVar env tv + | Just (tc,tys) <- splitTyConApp_maybe ty = let hash_tc = fromIntegral (hashName (tyConName tc)) + in foldr (\t n -> fast_hash_type env t + n) hash_tc tys + | otherwise = 1 + +extend_env :: HashEnv -> Var -> (Int, VarEnv Int) +extend_env (n,env) b = (n+1, extendVarEnv env b n) + +hashVar :: HashEnv -> Var -> Word32 +hashVar (_,env) v + = fromIntegral (lookupVarEnv env v `orElse` hashName (idName v)) \end{code} %************************************************************************ @@ -1404,17 +1075,17 @@ arguments, come from another DLL (because we can't refer to static labels in other DLLs). If this happens we simply make the RHS into an updatable thunk, -and 'exectute' it rather than allocating it statically. +and 'execute' it rather than allocating it statically. \begin{code} +-- | This function is called only on *top-level* right-hand sides. +-- Returns @True@ if the RHS can be allocated statically in the output, +-- with no thunks involved at all. rhsIsStatic :: PackageId -> CoreExpr -> Bool --- This function is called only on *top-level* right-hand sides --- Returns True if the RHS can be allocated statically, with --- no thunks involved at all. --- -- It's called (i) in TidyPgm.hasCafRefs to decide if the rhs is, or --- refers to, CAFs; and (ii) in CoreToStg to decide whether to put an --- update flag on it. +-- refers to, CAFs; (ii) in CoreToStg to decide whether to put an +-- update flag on it and (iii) in DsExpr to decide how to expand +-- list literals -- -- The basic idea is that rhsIsStatic returns True only if the RHS is -- (a) a value lambda @@ -1464,25 +1135,22 @@ rhsIsStatic :: PackageId -> CoreExpr -> Bool -- dynamic -- -- c) don't look through unfolding of f in (f x). --- --- When opt_RuntimeTypes is on, we keep type lambdas and treat --- them as making the RHS re-entrant (non-updatable). -rhsIsStatic this_pkg rhs = is_static False rhs +rhsIsStatic _this_pkg rhs = is_static False rhs where is_static :: Bool -- True <=> in a constructor argument; must be atomic -> CoreExpr -> Bool is_static False (Lam b e) = isRuntimeVar b || is_static False e - is_static in_arg (Note (SCC _) e) = False + is_static _ (Note (SCC _) _) = False is_static in_arg (Note _ e) = is_static in_arg e - is_static in_arg (Cast e co) = is_static in_arg e + is_static in_arg (Cast e _) = is_static in_arg e - is_static in_arg (Lit lit) + is_static _ (Lit lit) = case lit of - MachLabel _ _ -> False - other -> True + MachLabel _ _ _ -> False + _ -> True -- A MachLabel (foreign import "&foo") in an argument -- prevents a constructor application from being static. The -- reason is that it might give rise to unresolvable symbols @@ -1496,7 +1164,7 @@ rhsIsStatic this_pkg rhs = is_static False rhs where go (Var f) n_val_args #if mingw32_TARGET_OS - | not (isDllName this_pkg (idName f)) + | not (isDllName _this_pkg (idName f)) #endif = saturated_data_con f n_val_args || (in_arg && n_val_args == 0) @@ -1518,11 +1186,11 @@ rhsIsStatic this_pkg rhs = is_static False rhs -- x = D# (1.0## /## 2.0##) -- can't float because /## can fail. - go (Note (SCC _) f) n_val_args = False - go (Note _ f) n_val_args = go f n_val_args - go (Cast e co) n_val_args = go e n_val_args + go (Note (SCC _) _) _ = False + go (Note _ f) n_val_args = go f n_val_args + go (Cast e _) n_val_args = go e n_val_args - go other n_val_args = False + go _ _ = False saturated_data_con f n_val_args = case isDataConWorkId_maybe f of