2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[CoreUtils]{Utility functions on @Core@ syntax}
9 mkNote, mkInlineMe, mkSCC, mkCoerce,
10 bindNonRec, mkIfThenElse, mkAltExpr,
13 -- Taking expressions apart
16 -- Properties of expressions
17 exprType, coreAltsType,
18 exprIsBottom, exprIsDupable, exprIsTrivial, exprIsCheap,
19 exprIsValue,exprOkForSpeculation, exprIsBig,
20 exprIsConApp_maybe, exprIsAtom,
21 idAppIsBottom, idAppIsCheap,
24 -- Expr transformation
26 exprArity, exprEtaExpandArity,
35 cheapEqExpr, eqExpr, applyTypeToArgs
38 #include "HsVersions.h"
41 import GlaExts -- For `xori`
44 import CoreFVs ( exprFreeVars )
45 import PprCore ( pprCoreExpr )
46 import Var ( Var, isId, isTyVar )
49 import Name ( hashName )
50 import Literal ( hashLiteral, literalType, litIsDupable )
51 import DataCon ( DataCon, dataConRepArity )
52 import PrimOp ( primOpOkForSpeculation, primOpIsCheap,
54 import Id ( Id, idType, globalIdDetails, idStrictness, idLBVarInfo,
55 mkWildId, idArity, idName, idUnfolding, idInfo, isOneShotLambda,
56 isDataConId_maybe, isPrimOpId_maybe, mkSysLocal, hasNoBinding
58 import IdInfo ( LBVarInfo(..),
61 import Demand ( appIsBottom )
62 import Type ( Type, mkFunTy, mkForAllTy, splitFunTy_maybe,
63 applyTys, isUnLiftedType, seqType, mkUTy, mkTyVarTy,
64 splitForAllTy_maybe, splitNewType_maybe
66 import TysWiredIn ( boolTy, trueDataCon, falseDataCon )
67 import CostCentre ( CostCentre )
68 import UniqSupply ( UniqSupply, splitUniqSupply, uniqFromSupply )
69 import Maybes ( maybeToBool )
71 import TysPrim ( alphaTy ) -- Debugging only
75 %************************************************************************
77 \subsection{Find the type of a Core atom/expression}
79 %************************************************************************
82 exprType :: CoreExpr -> Type
84 exprType (Var var) = idType var
85 exprType (Lit lit) = literalType lit
86 exprType (Let _ body) = exprType body
87 exprType (Case _ _ alts) = coreAltsType alts
88 exprType (Note (Coerce ty _) e) = ty -- **! should take usage from e
89 exprType (Note other_note e) = exprType e
90 exprType (Lam binder expr) = mkPiType binder (exprType expr)
92 = case collectArgs e of
93 (fun, args) -> applyTypeToArgs e (exprType fun) args
95 exprType other = pprTrace "exprType" (pprCoreExpr other) alphaTy
97 coreAltsType :: [CoreAlt] -> Type
98 coreAltsType ((_,_,rhs) : _) = exprType rhs
101 @mkPiType@ makes a (->) type or a forall type, depending on whether
102 it is given a type variable or a term variable. We cleverly use the
103 lbvarinfo field to figure out the right annotation for the arrove in
104 case of a term variable.
107 mkPiType :: Var -> Type -> Type -- The more polymorphic version doesn't work...
108 mkPiType v ty | isId v = (case idLBVarInfo v of
109 LBVarInfo u -> mkUTy u
111 mkFunTy (idType v) ty
112 | isTyVar v = mkForAllTy v ty
116 -- The first argument is just for debugging
117 applyTypeToArgs :: CoreExpr -> Type -> [CoreExpr] -> Type
118 applyTypeToArgs e op_ty [] = op_ty
120 applyTypeToArgs e op_ty (Type ty : args)
121 = -- Accumulate type arguments so we can instantiate all at once
122 applyTypeToArgs e (applyTys op_ty tys) rest_args
124 (tys, rest_args) = go [ty] args
125 go tys (Type ty : args) = go (ty:tys) args
126 go tys rest_args = (reverse tys, rest_args)
128 applyTypeToArgs e op_ty (other_arg : args)
129 = case (splitFunTy_maybe op_ty) of
130 Just (_, res_ty) -> applyTypeToArgs e res_ty args
131 Nothing -> pprPanic "applyTypeToArgs" (pprCoreExpr e)
136 %************************************************************************
138 \subsection{Attaching notes}
140 %************************************************************************
142 mkNote removes redundant coercions, and SCCs where possible
145 mkNote :: Note -> CoreExpr -> CoreExpr
146 mkNote (Coerce to_ty from_ty) expr = mkCoerce to_ty from_ty expr
147 mkNote (SCC cc) expr = mkSCC cc expr
148 mkNote InlineMe expr = mkInlineMe expr
149 mkNote note expr = Note note expr
151 -- Slide InlineCall in around the function
152 -- No longer necessary I think (SLPJ Apr 99)
153 -- mkNote InlineCall (App f a) = App (mkNote InlineCall f) a
154 -- mkNote InlineCall (Var v) = Note InlineCall (Var v)
155 -- mkNote InlineCall expr = expr
158 Drop trivial InlineMe's. This is somewhat important, because if we have an unfolding
159 that looks like (Note InlineMe (Var v)), the InlineMe doesn't go away because it may
160 not be *applied* to anything.
162 We don't use exprIsTrivial here, though, because we sometimes generate worker/wrapper
165 f = inline_me (coerce t fw)
166 As usual, the inline_me prevents the worker from getting inlined back into the wrapper.
167 We want the split, so that the coerces can cancel at the call site.
169 However, we can get left with tiresome type applications. Notably, consider
170 f = /\ a -> let t = e in (t, w)
171 Then lifting the let out of the big lambda gives
173 f = /\ a -> let t = inline_me (t' a) in (t, w)
174 The inline_me is to stop the simplifier inlining t' right back
175 into t's RHS. In the next phase we'll substitute for t (since
176 its rhs is trivial) and *then* we could get rid of the inline_me.
177 But it hardly seems worth it, so I don't bother.
180 mkInlineMe (Var v) = Var v
181 mkInlineMe e = Note InlineMe e
187 mkCoerce :: Type -> Type -> CoreExpr -> CoreExpr
189 mkCoerce to_ty from_ty (Note (Coerce to_ty2 from_ty2) expr)
190 = ASSERT( from_ty == to_ty2 )
191 mkCoerce to_ty from_ty2 expr
193 mkCoerce to_ty from_ty expr
194 | to_ty == from_ty = expr
195 | otherwise = ASSERT( from_ty == exprType expr )
196 Note (Coerce to_ty from_ty) expr
200 mkSCC :: CostCentre -> Expr b -> Expr b
201 -- Note: Nested SCC's *are* preserved for the benefit of
202 -- cost centre stack profiling (Durham)
204 mkSCC cc (Lit lit) = Lit lit
205 mkSCC cc (Lam x e) = Lam x (mkSCC cc e) -- Move _scc_ inside lambda
206 mkSCC cc expr = Note (SCC cc) expr
210 %************************************************************************
212 \subsection{Other expression construction}
214 %************************************************************************
217 bindNonRec :: Id -> CoreExpr -> CoreExpr -> CoreExpr
218 -- (bindNonRec x r b) produces either
221 -- case r of x { _DEFAULT_ -> b }
223 -- depending on whether x is unlifted or not
224 -- It's used by the desugarer to avoid building bindings
225 -- that give Core Lint a heart attack. Actually the simplifier
226 -- deals with them perfectly well.
227 bindNonRec bndr rhs body
228 | isUnLiftedType (idType bndr) = Case rhs bndr [(DEFAULT,[],body)]
229 | otherwise = Let (NonRec bndr rhs) body
233 mkAltExpr :: AltCon -> [CoreBndr] -> [Type] -> CoreExpr
234 -- This guy constructs the value that the scrutinee must have
235 -- when you are in one particular branch of a case
236 mkAltExpr (DataAlt con) args inst_tys
237 = mkConApp con (map Type inst_tys ++ map varToCoreExpr args)
238 mkAltExpr (LitAlt lit) [] []
241 mkIfThenElse :: CoreExpr -> CoreExpr -> CoreExpr -> CoreExpr
242 mkIfThenElse guard then_expr else_expr
243 = Case guard (mkWildId boolTy)
244 [ (DataAlt trueDataCon, [], then_expr),
245 (DataAlt falseDataCon, [], else_expr) ]
249 %************************************************************************
251 \subsection{Taking expressions apart}
253 %************************************************************************
257 findDefault :: [CoreAlt] -> ([CoreAlt], Maybe CoreExpr)
258 findDefault [] = ([], Nothing)
259 findDefault ((DEFAULT,args,rhs) : alts) = ASSERT( null alts && null args )
261 findDefault (alt : alts) = case findDefault alts of
262 (alts', deflt) -> (alt : alts', deflt)
264 findAlt :: AltCon -> [CoreAlt] -> CoreAlt
268 go [] = pprPanic "Missing alternative" (ppr con $$ vcat (map ppr alts))
269 go (alt : alts) | matches alt = alt
270 | otherwise = go alts
272 matches (DEFAULT, _, _) = True
273 matches (con1, _, _) = con == con1
277 %************************************************************************
279 \subsection{Figuring out things about expressions}
281 %************************************************************************
283 @exprIsTrivial@ is true of expressions we are unconditionally happy to
284 duplicate; simple variables and constants, and type
285 applications. Note that primop Ids aren't considered
288 @exprIsBottom@ is true of expressions that are guaranteed to diverge
292 exprIsTrivial (Var v)
293 | hasNoBinding v = idArity v == 0
294 -- WAS: | Just op <- isPrimOpId_maybe v = primOpIsDupable op
295 -- The idea here is that a constructor worker, like $wJust, is
296 -- really short for (\x -> $wJust x), becuase $wJust has no binding.
297 -- So it should be treated like a lambda.
298 -- Ditto unsaturated primops.
299 -- This came up when dealing with eta expansion/reduction for
301 -- Here we want to eta-expand. This looks like an optimisation,
302 -- but it's important (albeit tiresome) that CoreSat doesn't increase
305 exprIsTrivial (Type _) = True
306 exprIsTrivial (Lit lit) = True
307 exprIsTrivial (App e arg) = isTypeArg arg && exprIsTrivial e
308 exprIsTrivial (Note _ e) = exprIsTrivial e
309 exprIsTrivial (Lam b body) | isTyVar b = exprIsTrivial body
310 exprIsTrivial other = False
312 exprIsAtom :: CoreExpr -> Bool
313 -- Used to decide whether to let-binding an STG argument
314 -- when compiling to ILX => type applications are not allowed
315 exprIsAtom (Var v) = True -- primOpIsDupable?
316 exprIsAtom (Lit lit) = True
317 exprIsAtom (Type ty) = True
318 exprIsAtom (Note _ e) = exprIsAtom e
319 exprIsAtom other = False
323 @exprIsDupable@ is true of expressions that can be duplicated at a modest
324 cost in code size. This will only happen in different case
325 branches, so there's no issue about duplicating work.
327 That is, exprIsDupable returns True of (f x) even if
328 f is very very expensive to call.
330 Its only purpose is to avoid fruitless let-binding
331 and then inlining of case join points
335 exprIsDupable (Type _) = True
336 exprIsDupable (Var v) = True
337 exprIsDupable (Lit lit) = litIsDupable lit
338 exprIsDupable (Note _ e) = exprIsDupable e
342 go (Var v) n_args = True
343 go (App f a) n_args = n_args < dupAppSize
346 go other n_args = False
349 dupAppSize = 4 -- Size of application we are prepared to duplicate
352 @exprIsCheap@ looks at a Core expression and returns \tr{True} if
353 it is obviously in weak head normal form, or is cheap to get to WHNF.
354 [Note that that's not the same as exprIsDupable; an expression might be
355 big, and hence not dupable, but still cheap.]
357 By ``cheap'' we mean a computation we're willing to:
358 push inside a lambda, or
359 inline at more than one place
360 That might mean it gets evaluated more than once, instead of being
361 shared. The main examples of things which aren't WHNF but are
366 (where e, and all the ei are cheap)
369 (where e and b are cheap)
372 (where op is a cheap primitive operator)
375 (because we are happy to substitute it inside a lambda)
377 Notice that a variable is considered 'cheap': we can push it inside a lambda,
378 because sharing will make sure it is only evaluated once.
381 exprIsCheap :: CoreExpr -> Bool
382 exprIsCheap (Lit lit) = True
383 exprIsCheap (Type _) = True
384 exprIsCheap (Var _) = True
385 exprIsCheap (Note _ e) = exprIsCheap e
386 exprIsCheap (Lam x e) = if isId x then True else exprIsCheap e
387 exprIsCheap (Case e _ alts) = exprIsCheap e &&
388 and [exprIsCheap rhs | (_,_,rhs) <- alts]
389 -- Experimentally, treat (case x of ...) as cheap
390 -- (and case __coerce x etc.)
391 -- This improves arities of overloaded functions where
392 -- there is only dictionary selection (no construction) involved
393 exprIsCheap (Let (NonRec x _) e)
394 | isUnLiftedType (idType x) = exprIsCheap e
396 -- strict lets always have cheap right hand sides, and
399 exprIsCheap other_expr
400 = go other_expr 0 True
402 go (Var f) n_args args_cheap
403 = (idAppIsCheap f n_args && args_cheap)
404 -- A constructor, cheap primop, or partial application
406 || idAppIsBottom f n_args
407 -- Application of a function which
408 -- always gives bottom; we treat this as cheap
409 -- because it certainly doesn't need to be shared!
411 go (App f a) n_args args_cheap
412 | isTypeArg a = go f n_args args_cheap
413 | otherwise = go f (n_args + 1) (exprIsCheap a && args_cheap)
415 go other n_args args_cheap = False
417 idAppIsCheap :: Id -> Int -> Bool
418 idAppIsCheap id n_val_args
419 | n_val_args == 0 = True -- Just a type application of
420 -- a variable (f t1 t2 t3)
422 | otherwise = case globalIdDetails id of
424 RecordSelId _ -> True -- I'm experimenting with making record selection
425 -- look cheap, so we will substitute it inside a
426 -- lambda. Particularly for dictionary field selection
428 PrimOpId op -> primOpIsCheap op -- In principle we should worry about primops
429 -- that return a type variable, since the result
430 -- might be applied to something, but I'm not going
431 -- to bother to check the number of args
432 other -> n_val_args < idArity id
435 exprOkForSpeculation returns True of an expression that it is
437 * safe to evaluate even if normal order eval might not
438 evaluate the expression at all, or
440 * safe *not* to evaluate even if normal order would do so
444 the expression guarantees to terminate,
446 without raising an exception,
447 without causing a side effect (e.g. writing a mutable variable)
450 let x = case y# +# 1# of { r# -> I# r# }
453 case y# +# 1# of { r# ->
458 We can only do this if the (y+1) is ok for speculation: it has no
459 side effects, and can't diverge or raise an exception.
462 exprOkForSpeculation :: CoreExpr -> Bool
463 exprOkForSpeculation (Lit _) = True
464 exprOkForSpeculation (Var v) = isUnLiftedType (idType v)
465 exprOkForSpeculation (Note _ e) = exprOkForSpeculation e
466 exprOkForSpeculation other_expr
467 = go other_expr 0 True
469 go (Var f) n_args args_ok
470 = case globalIdDetails f of
471 DataConId _ -> True -- The strictness of the constructor has already
472 -- been expressed by its "wrapper", so we don't need
473 -- to take the arguments into account
475 PrimOpId op -> primOpOkForSpeculation op && args_ok
476 -- A bit conservative: we don't really need
477 -- to care about lazy arguments, but this is easy
481 go (App f a) n_args args_ok
482 | isTypeArg a = go f n_args args_ok
483 | otherwise = go f (n_args + 1) (exprOkForSpeculation a && args_ok)
485 go other n_args args_ok = False
490 exprIsBottom :: CoreExpr -> Bool -- True => definitely bottom
491 exprIsBottom e = go 0 e
493 -- n is the number of args
494 go n (Note _ e) = go n e
495 go n (Let _ e) = go n e
496 go n (Case e _ _) = go 0 e -- Just check the scrut
497 go n (App e _) = go (n+1) e
498 go n (Var v) = idAppIsBottom v n
500 go n (Lam _ _) = False
502 idAppIsBottom :: Id -> Int -> Bool
503 idAppIsBottom id n_val_args = appIsBottom (idStrictness id) n_val_args
506 @exprIsValue@ returns true for expressions that are certainly *already*
507 evaluated to WHNF. This is used to decide wether it's ok to change
508 case x of _ -> e ===> e
510 and to decide whether it's safe to discard a `seq`
512 So, it does *not* treat variables as evaluated, unless they say they are.
514 But it *does* treat partial applications and constructor applications
515 as values, even if their arguments are non-trivial;
516 e.g. (:) (f x) (map f xs) is a value
517 map (...redex...) is a value
518 Because `seq` on such things completes immediately
520 A worry: constructors with unboxed args:
522 Suppose (f x) diverges; then C (f x) is not a value.
525 exprIsValue :: CoreExpr -> Bool -- True => Value-lambda, constructor, PAP
526 exprIsValue (Type ty) = True -- Types are honorary Values; we don't mind
528 exprIsValue (Lit l) = True
529 exprIsValue (Lam b e) = isId b || exprIsValue e
530 exprIsValue (Note _ e) = exprIsValue e
531 exprIsValue other_expr
534 go (Var f) n_args = idAppIsValue f n_args
537 | isTypeArg a = go f n_args
538 | otherwise = go f (n_args + 1)
540 go (Note _ f) n_args = go f n_args
542 go other n_args = False
544 idAppIsValue :: Id -> Int -> Bool
545 idAppIsValue id n_val_args
546 = case globalIdDetails id of
548 PrimOpId _ -> n_val_args < idArity id
549 other | n_val_args == 0 -> isEvaldUnfolding (idUnfolding id)
550 | otherwise -> n_val_args < idArity id
551 -- A worry: what if an Id's unfolding is just itself:
552 -- then we could get an infinite loop...
556 exprIsConApp_maybe :: CoreExpr -> Maybe (DataCon, [CoreExpr])
557 exprIsConApp_maybe expr
558 = analyse (collectArgs expr)
560 analyse (Var fun, args)
561 | Just con <- isDataConId_maybe fun,
562 length args >= dataConRepArity con
563 -- Might be > because the arity excludes type args
566 -- Look through unfoldings, but only cheap ones, because
567 -- we are effectively duplicating the unfolding
568 analyse (Var fun, [])
569 | let unf = idUnfolding fun,
571 = exprIsConApp_maybe (unfoldingTemplate unf)
573 analyse other = Nothing
576 The arity of an expression (in the code-generator sense, i.e. the
577 number of lambdas at the beginning).
580 exprArity :: CoreExpr -> Int
582 | isTyVar x = exprArity e
583 | otherwise = 1 + exprArity e
585 -- Ignore coercions. Top level sccs are removed by the final
586 -- profiling pass, so we ignore those too.
592 %************************************************************************
594 \subsection{Eta reduction and expansion}
596 %************************************************************************
598 @etaReduce@ trys an eta reduction at the top level of a Core Expr.
600 e.g. \ x y -> f x y ===> f
602 But we only do this if it gets rid of a whole lambda, not part.
603 The idea is that lambdas are often quite helpful: they indicate
604 head normal forms, so we don't want to chuck them away lightly.
607 etaReduce :: CoreExpr -> CoreExpr
608 -- ToDo: we should really check that we don't turn a non-bottom
609 -- lambda into a bottom variable. Sigh
611 etaReduce expr@(Lam bndr body)
612 = check (reverse binders) body
614 (binders, body) = collectBinders expr
617 | not (any (`elemVarSet` body_fvs) binders)
620 body_fvs = exprFreeVars body
622 check (b : bs) (App fun arg)
623 | (varToCoreExpr b `cheapEqExpr` arg)
626 check _ _ = expr -- Bale out
628 etaReduce expr = expr -- The common case
633 exprEtaExpandArity :: CoreExpr -> (Int, Bool)
634 -- The Int is number of value args the thing can be
635 -- applied to without doing much work
636 -- The Bool is True iff there are enough explicit value lambdas
637 -- at the top to make this arity apparent
638 -- (but ignore it when arity==0)
640 -- This is used when eta expanding
641 -- e ==> \xy -> e x y
643 -- It returns 1 (or more) to:
644 -- case x of p -> \s -> ...
645 -- because for I/O ish things we really want to get that \s to the top.
646 -- We are prepared to evaluate x each time round the loop in order to get that
648 -- Consider let x = expensive in \y z -> E
649 -- We want this to have arity 2 if the \y-abstraction is a 1-shot lambda
650 -- Hence the extra Bool returned by go1
651 -- NB: this is particularly important/useful for IO state
652 -- transformers, where we often get
653 -- let x = E in \ s -> ...
654 -- and the \s is a real-world state token abstraction. Such
655 -- abstractions are almost invariably 1-shot, so we want to
656 -- pull the \s out, past the let x=E.
657 -- The hack is in Id.isOneShotLambda
662 go :: Int -> CoreExpr -> (Int,Bool)
663 go ar (Lam x e) | isId x = go (ar+1) e
664 | otherwise = go ar e
665 go ar (Note n e) | ok_note n = go ar e
666 go ar other = (ar + ar', ar' == 0)
668 ar' = length (go1 other)
670 go1 :: CoreExpr -> [Bool]
671 -- (go1 e) = [b1,..,bn]
672 -- means expression can be rewritten \x_b1 -> ... \x_bn -> body
673 -- where bi is True <=> the lambda is one-shot
675 go1 (Note n e) | ok_note n = go1 e
676 go1 (Var v) = replicate (idArity v) False -- When the type of the Id
677 -- encodes one-shot-ness, use
680 -- Lambdas; increase arity
681 go1 (Lam x e) | isId x = isOneShotLambda x : go1 e
684 -- Applications; decrease arity
685 go1 (App f (Type _)) = go1 f
686 go1 (App f a) = case go1 f of
687 (one_shot : xs) | one_shot || exprIsCheap a -> xs
690 -- Case/Let; keep arity if either the expression is cheap
691 -- or it's a 1-shot lambda
692 go1 (Case scrut _ alts) = case foldr1 (zipWith (&&)) [go1 rhs | (_,_,rhs) <- alts] of
693 xs@(one_shot : _) | one_shot || exprIsCheap scrut -> xs
695 go1 (Let b e) = case go1 e of
696 xs@(one_shot : _) | one_shot || all exprIsCheap (rhssOfBind b) -> xs
701 ok_note (Coerce _ _) = True
702 ok_note InlineCall = True
703 ok_note other = False
704 -- Notice that we do not look through __inline_me__
705 -- This one is a bit more surprising, but consider
706 -- f = _inline_me (\x -> e)
707 -- We DO NOT want to eta expand this to
708 -- f = \x -> (_inline_me (\x -> e)) x
709 -- because the _inline_me gets dropped now it is applied,
714 min_zero :: [Int] -> Int -- Find the minimum, but zero is the smallest
715 min_zero (x:xs) = go x xs
717 go 0 xs = 0 -- Nothing beats zero
719 go min (x:xs) | x < min = go x xs
720 | otherwise = go min xs
726 etaExpand :: Int -- Add this number of value args
728 -> CoreExpr -> Type -- Expression and its type
730 -- (etaExpand n us e ty) returns an expression with
731 -- the same meaning as 'e', but with arity 'n'.
733 -- Given e' = etaExpand n us e ty
735 -- ty = exprType e = exprType e'
737 -- etaExpand deals with for-alls and coerces. For example:
739 -- where E :: forall a. T
740 -- newtype T = MkT (A -> B)
743 -- (/\b. coerce T (\y::A -> (coerce (A->B) (E b) y)
745 -- (case x of { I# x -> /\ a -> coerce T E)
747 etaExpand n us expr ty
748 | n == 0 -- Saturated, so nothing to do
751 | otherwise -- An unsaturated constructor or primop; eta expand it
752 = case splitForAllTy_maybe ty of {
753 Just (tv,ty') -> Lam tv (etaExpand n us (App expr (Type (mkTyVarTy tv))) ty')
757 case splitFunTy_maybe ty of {
758 Just (arg_ty, res_ty) -> Lam arg1 (etaExpand (n-1) us2 (App expr (Var arg1)) res_ty)
760 arg1 = mkSysLocal SLIT("eta") uniq arg_ty
761 (us1, us2) = splitUniqSupply us
762 uniq = uniqFromSupply us1
766 case splitNewType_maybe ty of {
767 Just ty' -> mkCoerce ty ty' (etaExpand n us (mkCoerce ty' ty expr) ty') ;
769 Nothing -> pprTrace "Bad eta expand" (ppr expr $$ ppr ty) expr
774 %************************************************************************
776 \subsection{Equality}
778 %************************************************************************
780 @cheapEqExpr@ is a cheap equality test which bales out fast!
781 True => definitely equal
782 False => may or may not be equal
785 cheapEqExpr :: Expr b -> Expr b -> Bool
787 cheapEqExpr (Var v1) (Var v2) = v1==v2
788 cheapEqExpr (Lit lit1) (Lit lit2) = lit1 == lit2
789 cheapEqExpr (Type t1) (Type t2) = t1 == t2
791 cheapEqExpr (App f1 a1) (App f2 a2)
792 = f1 `cheapEqExpr` f2 && a1 `cheapEqExpr` a2
794 cheapEqExpr _ _ = False
796 exprIsBig :: Expr b -> Bool
797 -- Returns True of expressions that are too big to be compared by cheapEqExpr
798 exprIsBig (Lit _) = False
799 exprIsBig (Var v) = False
800 exprIsBig (Type t) = False
801 exprIsBig (App f a) = exprIsBig f || exprIsBig a
802 exprIsBig other = True
807 eqExpr :: CoreExpr -> CoreExpr -> Bool
808 -- Works ok at more general type, but only needed at CoreExpr
810 = eq emptyVarEnv e1 e2
812 -- The "env" maps variables in e1 to variables in ty2
813 -- So when comparing lambdas etc,
814 -- we in effect substitute v2 for v1 in e1 before continuing
815 eq env (Var v1) (Var v2) = case lookupVarEnv env v1 of
816 Just v1' -> v1' == v2
819 eq env (Lit lit1) (Lit lit2) = lit1 == lit2
820 eq env (App f1 a1) (App f2 a2) = eq env f1 f2 && eq env a1 a2
821 eq env (Lam v1 e1) (Lam v2 e2) = eq (extendVarEnv env v1 v2) e1 e2
822 eq env (Let (NonRec v1 r1) e1)
823 (Let (NonRec v2 r2) e2) = eq env r1 r2 && eq (extendVarEnv env v1 v2) e1 e2
824 eq env (Let (Rec ps1) e1)
825 (Let (Rec ps2) e2) = length ps1 == length ps2 &&
826 and (zipWith eq_rhs ps1 ps2) &&
829 env' = extendVarEnvList env [(v1,v2) | ((v1,_),(v2,_)) <- zip ps1 ps2]
830 eq_rhs (_,r1) (_,r2) = eq env' r1 r2
831 eq env (Case e1 v1 a1)
832 (Case e2 v2 a2) = eq env e1 e2 &&
833 length a1 == length a2 &&
834 and (zipWith (eq_alt env') a1 a2)
836 env' = extendVarEnv env v1 v2
838 eq env (Note n1 e1) (Note n2 e2) = eq_note env n1 n2 && eq env e1 e2
839 eq env (Type t1) (Type t2) = t1 == t2
842 eq_list env [] [] = True
843 eq_list env (e1:es1) (e2:es2) = eq env e1 e2 && eq_list env es1 es2
844 eq_list env es1 es2 = False
846 eq_alt env (c1,vs1,r1) (c2,vs2,r2) = c1==c2 &&
847 eq (extendVarEnvList env (vs1 `zip` vs2)) r1 r2
849 eq_note env (SCC cc1) (SCC cc2) = cc1 == cc2
850 eq_note env (Coerce t1 f1) (Coerce t2 f2) = t1==t2 && f1==f2
851 eq_note env InlineCall InlineCall = True
852 eq_note env other1 other2 = False
856 %************************************************************************
858 \subsection{The size of an expression}
860 %************************************************************************
863 coreBindsSize :: [CoreBind] -> Int
864 coreBindsSize bs = foldr ((+) . bindSize) 0 bs
866 exprSize :: CoreExpr -> Int
867 -- A measure of the size of the expressions
868 -- It also forces the expression pretty drastically as a side effect
869 exprSize (Var v) = varSize v
870 exprSize (Lit lit) = lit `seq` 1
871 exprSize (App f a) = exprSize f + exprSize a
872 exprSize (Lam b e) = varSize b + exprSize e
873 exprSize (Let b e) = bindSize b + exprSize e
874 exprSize (Case e b as) = exprSize e + varSize b + foldr ((+) . altSize) 0 as
875 exprSize (Note n e) = noteSize n + exprSize e
876 exprSize (Type t) = seqType t `seq` 1
878 noteSize (SCC cc) = cc `seq` 1
879 noteSize (Coerce t1 t2) = seqType t1 `seq` seqType t2 `seq` 1
880 noteSize InlineCall = 1
881 noteSize InlineMe = 1
883 varSize :: Var -> Int
884 varSize b | isTyVar b = 1
885 | otherwise = seqType (idType b) `seq`
886 megaSeqIdInfo (idInfo b) `seq`
889 varsSize = foldr ((+) . varSize) 0
891 bindSize (NonRec b e) = varSize b + exprSize e
892 bindSize (Rec prs) = foldr ((+) . pairSize) 0 prs
894 pairSize (b,e) = varSize b + exprSize e
896 altSize (c,bs,e) = c `seq` varsSize bs + exprSize e
900 %************************************************************************
904 %************************************************************************
907 hashExpr :: CoreExpr -> Int
908 hashExpr e | hash < 0 = 77 -- Just in case we hit -maxInt
911 hash = abs (hash_expr e) -- Negative numbers kill UniqFM
913 hash_expr (Note _ e) = hash_expr e
914 hash_expr (Let (NonRec b r) e) = hashId b
915 hash_expr (Let (Rec ((b,r):_)) e) = hashId b
916 hash_expr (Case _ b _) = hashId b
917 hash_expr (App f e) = hash_expr f * fast_hash_expr e
918 hash_expr (Var v) = hashId v
919 hash_expr (Lit lit) = hashLiteral lit
920 hash_expr (Lam b _) = hashId b
921 hash_expr (Type t) = trace "hash_expr: type" 1 -- Shouldn't happen
923 fast_hash_expr (Var v) = hashId v
924 fast_hash_expr (Lit lit) = hashLiteral lit
925 fast_hash_expr (App f (Type _)) = fast_hash_expr f
926 fast_hash_expr (App f a) = fast_hash_expr a
927 fast_hash_expr (Lam b _) = hashId b
928 fast_hash_expr other = 1
931 hashId id = hashName (idName id)