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 (SCC _) e) = False
319 exprIsAtom (Note _ e) = exprIsAtom e
320 exprIsAtom other = False
324 @exprIsDupable@ is true of expressions that can be duplicated at a modest
325 cost in code size. This will only happen in different case
326 branches, so there's no issue about duplicating work.
328 That is, exprIsDupable returns True of (f x) even if
329 f is very very expensive to call.
331 Its only purpose is to avoid fruitless let-binding
332 and then inlining of case join points
336 exprIsDupable (Type _) = True
337 exprIsDupable (Var v) = True
338 exprIsDupable (Lit lit) = litIsDupable lit
339 exprIsDupable (Note InlineMe e) = True
340 exprIsDupable (Note _ e) = exprIsDupable e
344 go (Var v) n_args = True
345 go (App f a) n_args = n_args < dupAppSize
348 go other n_args = False
351 dupAppSize = 4 -- Size of application we are prepared to duplicate
354 @exprIsCheap@ looks at a Core expression and returns \tr{True} if
355 it is obviously in weak head normal form, or is cheap to get to WHNF.
356 [Note that that's not the same as exprIsDupable; an expression might be
357 big, and hence not dupable, but still cheap.]
359 By ``cheap'' we mean a computation we're willing to:
360 push inside a lambda, or
361 inline at more than one place
362 That might mean it gets evaluated more than once, instead of being
363 shared. The main examples of things which aren't WHNF but are
368 (where e, and all the ei are cheap)
371 (where e and b are cheap)
374 (where op is a cheap primitive operator)
377 (because we are happy to substitute it inside a lambda)
379 Notice that a variable is considered 'cheap': we can push it inside a lambda,
380 because sharing will make sure it is only evaluated once.
383 exprIsCheap :: CoreExpr -> Bool
384 exprIsCheap (Lit lit) = True
385 exprIsCheap (Type _) = True
386 exprIsCheap (Var _) = True
387 exprIsCheap (Note InlineMe e) = True
388 exprIsCheap (Note _ e) = exprIsCheap e
389 exprIsCheap (Lam x e) = if isId x then True else exprIsCheap e
390 exprIsCheap (Case e _ alts) = exprIsCheap e &&
391 and [exprIsCheap rhs | (_,_,rhs) <- alts]
392 -- Experimentally, treat (case x of ...) as cheap
393 -- (and case __coerce x etc.)
394 -- This improves arities of overloaded functions where
395 -- there is only dictionary selection (no construction) involved
396 exprIsCheap (Let (NonRec x _) e)
397 | isUnLiftedType (idType x) = exprIsCheap e
399 -- strict lets always have cheap right hand sides, and
402 exprIsCheap other_expr
403 = go other_expr 0 True
405 go (Var f) n_args args_cheap
406 = (idAppIsCheap f n_args && args_cheap)
407 -- A constructor, cheap primop, or partial application
409 || idAppIsBottom f n_args
410 -- Application of a function which
411 -- always gives bottom; we treat this as cheap
412 -- because it certainly doesn't need to be shared!
414 go (App f a) n_args args_cheap
415 | isTypeArg a = go f n_args args_cheap
416 | otherwise = go f (n_args + 1) (exprIsCheap a && args_cheap)
418 go other n_args args_cheap = False
420 idAppIsCheap :: Id -> Int -> Bool
421 idAppIsCheap id n_val_args
422 | n_val_args == 0 = True -- Just a type application of
423 -- a variable (f t1 t2 t3)
425 | otherwise = case globalIdDetails id of
427 RecordSelId _ -> True -- I'm experimenting with making record selection
428 -- look cheap, so we will substitute it inside a
429 -- lambda. Particularly for dictionary field selection
431 PrimOpId op -> primOpIsCheap op -- In principle we should worry about primops
432 -- that return a type variable, since the result
433 -- might be applied to something, but I'm not going
434 -- to bother to check the number of args
435 other -> n_val_args < idArity id
438 exprOkForSpeculation returns True of an expression that it is
440 * safe to evaluate even if normal order eval might not
441 evaluate the expression at all, or
443 * safe *not* to evaluate even if normal order would do so
447 the expression guarantees to terminate,
449 without raising an exception,
450 without causing a side effect (e.g. writing a mutable variable)
453 let x = case y# +# 1# of { r# -> I# r# }
456 case y# +# 1# of { r# ->
461 We can only do this if the (y+1) is ok for speculation: it has no
462 side effects, and can't diverge or raise an exception.
465 exprOkForSpeculation :: CoreExpr -> Bool
466 exprOkForSpeculation (Lit _) = True
467 exprOkForSpeculation (Var v) = isUnLiftedType (idType v)
468 exprOkForSpeculation (Note _ e) = exprOkForSpeculation e
469 exprOkForSpeculation other_expr
470 = go other_expr 0 True
472 go (Var f) n_args args_ok
473 = case globalIdDetails f of
474 DataConId _ -> True -- The strictness of the constructor has already
475 -- been expressed by its "wrapper", so we don't need
476 -- to take the arguments into account
478 PrimOpId op -> primOpOkForSpeculation op && args_ok
479 -- A bit conservative: we don't really need
480 -- to care about lazy arguments, but this is easy
484 go (App f a) n_args args_ok
485 | isTypeArg a = go f n_args args_ok
486 | otherwise = go f (n_args + 1) (exprOkForSpeculation a && args_ok)
488 go other n_args args_ok = False
493 exprIsBottom :: CoreExpr -> Bool -- True => definitely bottom
494 exprIsBottom e = go 0 e
496 -- n is the number of args
497 go n (Note _ e) = go n e
498 go n (Let _ e) = go n e
499 go n (Case e _ _) = go 0 e -- Just check the scrut
500 go n (App e _) = go (n+1) e
501 go n (Var v) = idAppIsBottom v n
503 go n (Lam _ _) = False
505 idAppIsBottom :: Id -> Int -> Bool
506 idAppIsBottom id n_val_args = appIsBottom (idStrictness id) n_val_args
509 @exprIsValue@ returns true for expressions that are certainly *already*
510 evaluated to WHNF. This is used to decide wether it's ok to change
511 case x of _ -> e ===> e
513 and to decide whether it's safe to discard a `seq`
515 So, it does *not* treat variables as evaluated, unless they say they are.
517 But it *does* treat partial applications and constructor applications
518 as values, even if their arguments are non-trivial;
519 e.g. (:) (f x) (map f xs) is a value
520 map (...redex...) is a value
521 Because `seq` on such things completes immediately
523 A possible worry: constructors with unboxed args:
525 Suppose (f x) diverges; then C (f x) is not a value. True, but
526 this form is illegal (see the invariants in CoreSyn). Args of unboxed
527 type must be ok-for-speculation (or trivial).
530 exprIsValue :: CoreExpr -> Bool -- True => Value-lambda, constructor, PAP
531 exprIsValue (Type ty) = True -- Types are honorary Values; we don't mind
533 exprIsValue (Lit l) = True
534 exprIsValue (Lam b e) = isId b || exprIsValue e
535 exprIsValue (Note _ e) = exprIsValue e
536 exprIsValue other_expr
539 go (Var f) n_args = idAppIsValue f n_args
542 | isTypeArg a = go f n_args
543 | otherwise = go f (n_args + 1)
545 go (Note _ f) n_args = go f n_args
547 go other n_args = False
549 idAppIsValue :: Id -> Int -> Bool
550 idAppIsValue id n_val_args
551 = case globalIdDetails id of
553 PrimOpId _ -> n_val_args < idArity id
554 other | n_val_args == 0 -> isEvaldUnfolding (idUnfolding id)
555 | otherwise -> n_val_args < idArity id
556 -- A worry: what if an Id's unfolding is just itself:
557 -- then we could get an infinite loop...
561 exprIsConApp_maybe :: CoreExpr -> Maybe (DataCon, [CoreExpr])
562 exprIsConApp_maybe expr
563 = analyse (collectArgs expr)
565 analyse (Var fun, args)
566 | Just con <- isDataConId_maybe fun,
567 length args >= dataConRepArity con
568 -- Might be > because the arity excludes type args
571 -- Look through unfoldings, but only cheap ones, because
572 -- we are effectively duplicating the unfolding
573 analyse (Var fun, [])
574 | let unf = idUnfolding fun,
576 = exprIsConApp_maybe (unfoldingTemplate unf)
578 analyse other = Nothing
581 The arity of an expression (in the code-generator sense, i.e. the
582 number of lambdas at the beginning).
585 exprArity :: CoreExpr -> Int
587 | isTyVar x = exprArity e
588 | otherwise = 1 + exprArity e
590 -- Ignore coercions. Top level sccs are removed by the final
591 -- profiling pass, so we ignore those too.
597 %************************************************************************
599 \subsection{Eta reduction and expansion}
601 %************************************************************************
603 @etaReduce@ trys an eta reduction at the top level of a Core Expr.
605 e.g. \ x y -> f x y ===> f
607 But we only do this if it gets rid of a whole lambda, not part.
608 The idea is that lambdas are often quite helpful: they indicate
609 head normal forms, so we don't want to chuck them away lightly.
612 etaReduce :: CoreExpr -> CoreExpr
613 -- ToDo: we should really check that we don't turn a non-bottom
614 -- lambda into a bottom variable. Sigh
616 etaReduce expr@(Lam bndr body)
617 = check (reverse binders) body
619 (binders, body) = collectBinders expr
622 | not (any (`elemVarSet` body_fvs) binders)
625 body_fvs = exprFreeVars body
627 check (b : bs) (App fun arg)
628 | (varToCoreExpr b `cheapEqExpr` arg)
631 check _ _ = expr -- Bale out
633 etaReduce expr = expr -- The common case
638 exprEtaExpandArity :: CoreExpr -> (Int, Bool)
639 -- The Int is number of value args the thing can be
640 -- applied to without doing much work
641 -- The Bool is True iff there are enough explicit value lambdas
642 -- at the top to make this arity apparent
643 -- (but ignore it when arity==0)
645 -- This is used when eta expanding
646 -- e ==> \xy -> e x y
648 -- It returns 1 (or more) to:
649 -- case x of p -> \s -> ...
650 -- because for I/O ish things we really want to get that \s to the top.
651 -- We are prepared to evaluate x each time round the loop in order to get that
653 -- Consider let x = expensive in \y z -> E
654 -- We want this to have arity 2 if the \y-abstraction is a 1-shot lambda
655 -- Hence the extra Bool returned by go1
656 -- NB: this is particularly important/useful for IO state
657 -- transformers, where we often get
658 -- let x = E in \ s -> ...
659 -- and the \s is a real-world state token abstraction. Such
660 -- abstractions are almost invariably 1-shot, so we want to
661 -- pull the \s out, past the let x=E.
662 -- The hack is in Id.isOneShotLambda
667 go :: Int -> CoreExpr -> (Int,Bool)
668 go ar (Lam x e) | isId x = go (ar+1) e
669 | otherwise = go ar e
670 go ar (Note n e) | ok_note n = go ar e
671 go ar other = (ar + ar', ar' == 0)
673 ar' = length (go1 other)
675 go1 :: CoreExpr -> [Bool]
676 -- (go1 e) = [b1,..,bn]
677 -- means expression can be rewritten \x_b1 -> ... \x_bn -> body
678 -- where bi is True <=> the lambda is one-shot
680 go1 (Note n e) | ok_note n = go1 e
681 go1 (Var v) = replicate (idArity v) False -- When the type of the Id
682 -- encodes one-shot-ness, use
685 -- Lambdas; increase arity
686 go1 (Lam x e) | isId x = isOneShotLambda x : go1 e
689 -- Applications; decrease arity
690 go1 (App f (Type _)) = go1 f
691 go1 (App f a) = case go1 f of
692 (one_shot : xs) | one_shot || exprIsCheap a -> xs
695 -- Case/Let; keep arity if either the expression is cheap
696 -- or it's a 1-shot lambda
697 go1 (Case scrut _ alts) = case foldr1 (zipWith (&&)) [go1 rhs | (_,_,rhs) <- alts] of
698 xs@(one_shot : _) | one_shot || exprIsCheap scrut -> xs
700 go1 (Let b e) = case go1 e of
701 xs@(one_shot : _) | one_shot || all exprIsCheap (rhssOfBind b) -> xs
706 ok_note (Coerce _ _) = True
707 ok_note InlineCall = True
708 ok_note other = False
709 -- Notice that we do not look through __inline_me__
710 -- This one is a bit more surprising, but consider
711 -- f = _inline_me (\x -> e)
712 -- We DO NOT want to eta expand this to
713 -- f = \x -> (_inline_me (\x -> e)) x
714 -- because the _inline_me gets dropped now it is applied,
719 min_zero :: [Int] -> Int -- Find the minimum, but zero is the smallest
720 min_zero (x:xs) = go x xs
722 go 0 xs = 0 -- Nothing beats zero
724 go min (x:xs) | x < min = go x xs
725 | otherwise = go min xs
731 etaExpand :: Int -- Add this number of value args
733 -> CoreExpr -> Type -- Expression and its type
735 -- (etaExpand n us e ty) returns an expression with
736 -- the same meaning as 'e', but with arity 'n'.
738 -- Given e' = etaExpand n us e ty
740 -- ty = exprType e = exprType e'
742 -- etaExpand deals with for-alls and coerces. For example:
744 -- where E :: forall a. T
745 -- newtype T = MkT (A -> B)
748 -- (/\b. coerce T (\y::A -> (coerce (A->B) (E b) y)
750 -- (case x of { I# x -> /\ a -> coerce T E)
752 etaExpand n us expr ty
753 | n == 0 -- Saturated, so nothing to do
756 | otherwise -- An unsaturated constructor or primop; eta expand it
757 = case splitForAllTy_maybe ty of {
758 Just (tv,ty') -> Lam tv (etaExpand n us (App expr (Type (mkTyVarTy tv))) ty')
762 case splitFunTy_maybe ty of {
763 Just (arg_ty, res_ty) -> Lam arg1 (etaExpand (n-1) us2 (App expr (Var arg1)) res_ty)
765 arg1 = mkSysLocal SLIT("eta") uniq arg_ty
766 (us1, us2) = splitUniqSupply us
767 uniq = uniqFromSupply us1
771 case splitNewType_maybe ty of {
772 Just ty' -> mkCoerce ty ty' (etaExpand n us (mkCoerce ty' ty expr) ty') ;
774 Nothing -> pprTrace "Bad eta expand" (ppr expr $$ ppr ty) expr
779 %************************************************************************
781 \subsection{Equality}
783 %************************************************************************
785 @cheapEqExpr@ is a cheap equality test which bales out fast!
786 True => definitely equal
787 False => may or may not be equal
790 cheapEqExpr :: Expr b -> Expr b -> Bool
792 cheapEqExpr (Var v1) (Var v2) = v1==v2
793 cheapEqExpr (Lit lit1) (Lit lit2) = lit1 == lit2
794 cheapEqExpr (Type t1) (Type t2) = t1 == t2
796 cheapEqExpr (App f1 a1) (App f2 a2)
797 = f1 `cheapEqExpr` f2 && a1 `cheapEqExpr` a2
799 cheapEqExpr _ _ = False
801 exprIsBig :: Expr b -> Bool
802 -- Returns True of expressions that are too big to be compared by cheapEqExpr
803 exprIsBig (Lit _) = False
804 exprIsBig (Var v) = False
805 exprIsBig (Type t) = False
806 exprIsBig (App f a) = exprIsBig f || exprIsBig a
807 exprIsBig other = True
812 eqExpr :: CoreExpr -> CoreExpr -> Bool
813 -- Works ok at more general type, but only needed at CoreExpr
815 = eq emptyVarEnv e1 e2
817 -- The "env" maps variables in e1 to variables in ty2
818 -- So when comparing lambdas etc,
819 -- we in effect substitute v2 for v1 in e1 before continuing
820 eq env (Var v1) (Var v2) = case lookupVarEnv env v1 of
821 Just v1' -> v1' == v2
824 eq env (Lit lit1) (Lit lit2) = lit1 == lit2
825 eq env (App f1 a1) (App f2 a2) = eq env f1 f2 && eq env a1 a2
826 eq env (Lam v1 e1) (Lam v2 e2) = eq (extendVarEnv env v1 v2) e1 e2
827 eq env (Let (NonRec v1 r1) e1)
828 (Let (NonRec v2 r2) e2) = eq env r1 r2 && eq (extendVarEnv env v1 v2) e1 e2
829 eq env (Let (Rec ps1) e1)
830 (Let (Rec ps2) e2) = length ps1 == length ps2 &&
831 and (zipWith eq_rhs ps1 ps2) &&
834 env' = extendVarEnvList env [(v1,v2) | ((v1,_),(v2,_)) <- zip ps1 ps2]
835 eq_rhs (_,r1) (_,r2) = eq env' r1 r2
836 eq env (Case e1 v1 a1)
837 (Case e2 v2 a2) = eq env e1 e2 &&
838 length a1 == length a2 &&
839 and (zipWith (eq_alt env') a1 a2)
841 env' = extendVarEnv env v1 v2
843 eq env (Note n1 e1) (Note n2 e2) = eq_note env n1 n2 && eq env e1 e2
844 eq env (Type t1) (Type t2) = t1 == t2
847 eq_list env [] [] = True
848 eq_list env (e1:es1) (e2:es2) = eq env e1 e2 && eq_list env es1 es2
849 eq_list env es1 es2 = False
851 eq_alt env (c1,vs1,r1) (c2,vs2,r2) = c1==c2 &&
852 eq (extendVarEnvList env (vs1 `zip` vs2)) r1 r2
854 eq_note env (SCC cc1) (SCC cc2) = cc1 == cc2
855 eq_note env (Coerce t1 f1) (Coerce t2 f2) = t1==t2 && f1==f2
856 eq_note env InlineCall InlineCall = True
857 eq_note env other1 other2 = False
861 %************************************************************************
863 \subsection{The size of an expression}
865 %************************************************************************
868 coreBindsSize :: [CoreBind] -> Int
869 coreBindsSize bs = foldr ((+) . bindSize) 0 bs
871 exprSize :: CoreExpr -> Int
872 -- A measure of the size of the expressions
873 -- It also forces the expression pretty drastically as a side effect
874 exprSize (Var v) = varSize v
875 exprSize (Lit lit) = lit `seq` 1
876 exprSize (App f a) = exprSize f + exprSize a
877 exprSize (Lam b e) = varSize b + exprSize e
878 exprSize (Let b e) = bindSize b + exprSize e
879 exprSize (Case e b as) = exprSize e + varSize b + foldr ((+) . altSize) 0 as
880 exprSize (Note n e) = noteSize n + exprSize e
881 exprSize (Type t) = seqType t `seq` 1
883 noteSize (SCC cc) = cc `seq` 1
884 noteSize (Coerce t1 t2) = seqType t1 `seq` seqType t2 `seq` 1
885 noteSize InlineCall = 1
886 noteSize InlineMe = 1
888 varSize :: Var -> Int
889 varSize b | isTyVar b = 1
890 | otherwise = seqType (idType b) `seq`
891 megaSeqIdInfo (idInfo b) `seq`
894 varsSize = foldr ((+) . varSize) 0
896 bindSize (NonRec b e) = varSize b + exprSize e
897 bindSize (Rec prs) = foldr ((+) . pairSize) 0 prs
899 pairSize (b,e) = varSize b + exprSize e
901 altSize (c,bs,e) = c `seq` varsSize bs + exprSize e
905 %************************************************************************
909 %************************************************************************
912 hashExpr :: CoreExpr -> Int
913 hashExpr e | hash < 0 = 77 -- Just in case we hit -maxInt
916 hash = abs (hash_expr e) -- Negative numbers kill UniqFM
918 hash_expr (Note _ e) = hash_expr e
919 hash_expr (Let (NonRec b r) e) = hashId b
920 hash_expr (Let (Rec ((b,r):_)) e) = hashId b
921 hash_expr (Case _ b _) = hashId b
922 hash_expr (App f e) = hash_expr f * fast_hash_expr e
923 hash_expr (Var v) = hashId v
924 hash_expr (Lit lit) = hashLiteral lit
925 hash_expr (Lam b _) = hashId b
926 hash_expr (Type t) = trace "hash_expr: type" 1 -- Shouldn't happen
928 fast_hash_expr (Var v) = hashId v
929 fast_hash_expr (Lit lit) = hashLiteral lit
930 fast_hash_expr (App f (Type _)) = fast_hash_expr f
931 fast_hash_expr (App f a) = fast_hash_expr a
932 fast_hash_expr (Lam b _) = hashId b
933 fast_hash_expr other = 1
936 hashId id = hashName (idName id)