2 % (c) The AQUA Project, Glasgow University, 1993-1998
4 \section[SimplUtils]{The simplifier utilities}
8 simplBinder, simplBinders, simplIds,
10 mkCase, findAlt, findDefault,
12 -- The continuation type
13 SimplCont(..), DupFlag(..), contIsDupable, contResultType,
14 pushArgs, discardCont, countValArgs, countArgs,
15 analyseCont, discardInline
19 #include "HsVersions.h"
22 import CmdLineOpts ( opt_SimplDoLambdaEtaExpansion, opt_SimplCaseMerge )
24 import CoreUnfold ( isValueUnfolding )
25 import CoreFVs ( exprFreeVars )
26 import CoreUtils ( exprIsTrivial, cheapEqExpr, exprType, exprIsCheap, exprEtaExpandArity )
27 import Subst ( InScopeSet, mkSubst, substBndrs, substBndr, substIds, lookupIdSubst )
28 import Id ( Id, idType, isId, idName,
29 idOccInfo, idUnfolding,
30 idDemandInfo, mkId, idInfo
32 import IdInfo ( arityLowerBound, setOccInfo, vanillaIdInfo )
33 import Maybes ( maybeToBool, catMaybes )
34 import Name ( isLocalName, setNameUnique )
36 import Type ( Type, tyVarsOfType, tyVarsOfTypes, mkForAllTys, seqType,
37 splitTyConApp_maybe, mkTyVarTys, applyTys, splitFunTys, mkFunTys
39 import TysPrim ( statePrimTyCon )
40 import Var ( setVarUnique )
42 import VarEnv ( SubstEnv, SubstResult(..) )
43 import UniqSupply ( splitUniqSupply, uniqFromSupply )
44 import Util ( zipWithEqual, mapAccumL )
49 %************************************************************************
51 \subsection{The continuation data type}
53 %************************************************************************
56 data SimplCont -- Strict contexts
57 = Stop OutType -- Type of the result
59 | CoerceIt OutType -- The To-type, simplified
62 | InlinePlease -- This continuation makes a function very
63 SimplCont -- keen to inline itelf
66 InExpr SubstEnv -- The argument, as yet unsimplified,
67 SimplCont -- and its subst-env
70 InId [InAlt] SubstEnv -- The case binder, alts, and subst-env
73 | ArgOf DupFlag -- An arbitrary strict context: the argument
74 -- of a strict function, or a primitive-arg fn
76 OutType -- The type of the expression being sought by the context
77 -- f (error "foo") ==> coerce t (error "foo")
79 -- We need to know the type t, to which to coerce.
80 (OutExpr -> SimplM OutExprStuff) -- What to do with the result
82 instance Outputable SimplCont where
83 ppr (Stop _) = ptext SLIT("Stop")
84 ppr (ApplyTo dup arg se cont) = (ptext SLIT("ApplyTo") <+> ppr dup <+> ppr arg) $$ ppr cont
85 ppr (ArgOf dup _ _) = ptext SLIT("ArgOf...") <+> ppr dup
86 ppr (Select dup bndr alts se cont) = (ptext SLIT("Select") <+> ppr dup <+> ppr bndr) $$
87 (nest 4 (ppr alts)) $$ ppr cont
88 ppr (CoerceIt ty cont) = (ptext SLIT("CoerceIt") <+> ppr ty) $$ ppr cont
89 ppr (InlinePlease cont) = ptext SLIT("InlinePlease") $$ ppr cont
91 data DupFlag = OkToDup | NoDup
93 instance Outputable DupFlag where
94 ppr OkToDup = ptext SLIT("ok")
95 ppr NoDup = ptext SLIT("nodup")
97 contIsDupable :: SimplCont -> Bool
98 contIsDupable (Stop _) = True
99 contIsDupable (ApplyTo OkToDup _ _ _) = True
100 contIsDupable (ArgOf OkToDup _ _) = True
101 contIsDupable (Select OkToDup _ _ _ _) = True
102 contIsDupable (CoerceIt _ cont) = contIsDupable cont
103 contIsDupable (InlinePlease cont) = contIsDupable cont
104 contIsDupable other = False
106 pushArgs :: SubstEnv -> [InExpr] -> SimplCont -> SimplCont
107 pushArgs se [] cont = cont
108 pushArgs se (arg:args) cont = ApplyTo NoDup arg se (pushArgs se args cont)
110 discardCont :: SimplCont -- A continuation, expecting
111 -> SimplCont -- Replace the continuation with a suitable coerce
112 discardCont (Stop to_ty) = Stop to_ty
113 discardCont cont = CoerceIt to_ty (Stop to_ty)
115 to_ty = contResultType cont
117 contResultType :: SimplCont -> OutType
118 contResultType (Stop to_ty) = to_ty
119 contResultType (ArgOf _ to_ty _) = to_ty
120 contResultType (ApplyTo _ _ _ cont) = contResultType cont
121 contResultType (CoerceIt _ cont) = contResultType cont
122 contResultType (InlinePlease cont) = contResultType cont
123 contResultType (Select _ _ _ _ cont) = contResultType cont
125 countValArgs :: SimplCont -> Int
126 countValArgs (ApplyTo _ (Type ty) se cont) = countValArgs cont
127 countValArgs (ApplyTo _ val_arg se cont) = 1 + countValArgs cont
128 countValArgs other = 0
130 countArgs :: SimplCont -> Int
131 countArgs (ApplyTo _ arg se cont) = 1 + countArgs cont
136 Comment about analyseCont
137 ~~~~~~~~~~~~~~~~~~~~~~~~~
138 We want to avoid inlining an expression where there can't possibly be
139 any gain, such as in an argument position. Hence, if the continuation
140 is interesting (eg. a case scrutinee, application etc.) then we
141 inline, otherwise we don't.
143 Previously some_benefit used to return True only if the variable was
144 applied to some value arguments. This didn't work:
146 let x = _coerce_ (T Int) Int (I# 3) in
147 case _coerce_ Int (T Int) x of
150 we want to inline x, but can't see that it's a constructor in a case
151 scrutinee position, and some_benefit is False.
155 dMonadST = _/\_ t -> :Monad (g1 _@_ t, g2 _@_ t, g3 _@_ t)
157 .... case dMonadST _@_ x0 of (a,b,c) -> ....
159 we'd really like to inline dMonadST here, but we *don't* want to
160 inline if the case expression is just
162 case x of y { DEFAULT -> ... }
164 since we can just eliminate this case instead (x is in WHNF). Similar
165 applies when x is bound to a lambda expression. Hence
166 contIsInteresting looks for case expressions with just a single
170 analyseCont :: InScopeSet -> SimplCont
171 -> ([Bool], -- Arg-info flags; one for each value argument
172 Bool, -- Context of the result of the call is interesting
173 Bool) -- There was an InlinePlease
175 analyseCont in_scope cont
177 -- The "lone-variable" case is important. I spent ages
178 -- messing about with unsatisfactory varaints, but this is nice.
179 -- The idea is that if a variable appear all alone
180 -- as an arg of lazy fn, or rhs Stop
181 -- as scrutinee of a case Select
182 -- as arg of a strict fn ArgOf
183 -- then we should not inline it (unless there is some other reason,
184 -- e.g. is is the sole occurrence).
185 -- Why not? At least in the case-scrutinee situation, turning
186 -- case x of y -> ...
188 -- let y = (a,b) in ...
189 -- is bad if the binding for x will remain.
191 -- Another example: I discovered that strings
192 -- were getting inlined straight back into applications of 'error'
193 -- because the latter is strict.
195 -- f = \x -> ...(error s)...
197 -- Fundamentally such contexts should not ecourage inlining becuase
198 -- the context can ``see'' the unfolding of the variable (e.g. case or a RULE)
199 -- so there's no gain.
201 -- However, even a type application isn't a lone variable. Consider
202 -- case $fMonadST @ RealWorld of { :DMonad a b c -> c }
203 -- We had better inline that sucker! The case won't see through it.
205 (Stop _) -> boring_result -- Don't inline a lone variable
206 (Select _ _ _ _ _) -> boring_result -- Ditto
207 (ArgOf _ _ _) -> boring_result -- Ditto
208 (ApplyTo _ (Type _) _ cont) -> analyse_ty_app cont
209 other -> analyse_app cont
211 boring_result = ([], False, False)
213 -- For now, I'm treating not treating a variable applied to types as
214 -- "lone". The motivating example was
216 -- g = /\a. \y. h (f a)
217 -- There's no advantage in inlining f here, and perhaps
218 -- a significant disadvantage.
219 analyse_ty_app (Stop _) = boring_result
220 analyse_ty_app (ArgOf _ _ _) = boring_result
221 analyse_ty_app (Select _ _ _ _ _) = ([], True, False) -- See the $fMonadST example above
222 analyse_ty_app (ApplyTo _ (Type _) _ cont) = analyse_ty_app cont
223 analyse_ty_app cont = analyse_app cont
225 analyse_app (InlinePlease cont)
226 = case analyse_app cont of
227 (infos, icont, inline) -> (infos, icont, True)
229 analyse_app (ApplyTo _ arg subst cont)
230 | isValArg arg = case analyse_app cont of
231 (infos, icont, inline) -> (analyse_arg subst arg : infos, icont, inline)
232 | otherwise = analyse_app cont
234 analyse_app cont = ([], interesting_call_context cont, False)
236 -- An argument is interesting if it has *some* structure
237 -- We are here trying to avoid unfolding a function that
238 -- is applied only to variables that have no unfolding
239 -- (i.e. they are probably lambda bound): f x y z
240 -- There is little point in inlining f here.
241 analyse_arg :: SubstEnv -> InExpr -> Bool
242 analyse_arg subst (Var v) = case lookupIdSubst (mkSubst in_scope subst) v of
243 DoneId v' _ -> isValueUnfolding (idUnfolding v')
245 analyse_arg subst (Type _) = False
246 analyse_arg subst (App fn (Type _)) = analyse_arg subst fn
247 analyse_arg subst (Note _ a) = analyse_arg subst a
248 analyse_arg subst other = True
250 interesting_call_context (Stop _) = False
251 interesting_call_context (InlinePlease _) = True
252 interesting_call_context (Select _ _ _ _ _) = True
253 interesting_call_context (CoerceIt _ cont) = interesting_call_context cont
254 interesting_call_context (ApplyTo _ (Type _) _ cont) = interesting_call_context cont
255 interesting_call_context (ApplyTo _ _ _ _) = True
256 interesting_call_context (ArgOf _ _ _) = True
257 -- If this call is the arg of a strict function, the context
258 -- is a bit interesting. If we inline here, we may get useful
259 -- evaluation information to avoid repeated evals: e.g.
261 -- Here the contIsInteresting makes the '*' keener to inline,
262 -- which in turn exposes a constructor which makes the '+' inline.
263 -- Assuming that +,* aren't small enough to inline regardless.
265 -- It's also very important to inline in a strict context for things
268 -- Here, the context of (f x) is strict, and if f's unfolding is
269 -- a build it's *great* to inline it here. So we must ensure that
270 -- the context for (f x) is not totally uninteresting.
273 discardInline :: SimplCont -> SimplCont
274 discardInline (InlinePlease cont) = cont
275 discardInline (ApplyTo d e s cont) = ApplyTo d e s (discardInline cont)
276 discardInline cont = cont
281 %************************************************************************
283 \section{Dealing with a single binder}
285 %************************************************************************
288 simplBinders :: [InBinder] -> ([OutBinder] -> SimplM a) -> SimplM a
289 simplBinders bndrs thing_inside
290 = getSubst `thenSmpl` \ subst ->
292 (subst', bndrs') = substBndrs subst bndrs
294 seqBndrs bndrs' `seq`
295 setSubst subst' (thing_inside bndrs')
297 simplBinder :: InBinder -> (OutBinder -> SimplM a) -> SimplM a
298 simplBinder bndr thing_inside
299 = getSubst `thenSmpl` \ subst ->
301 (subst', bndr') = substBndr subst bndr
304 setSubst subst' (thing_inside bndr')
307 -- Same semantics as simplBinders, but a little less
308 -- plumbing and hence a little more efficient.
309 -- Maybe not worth the candle?
310 simplIds :: [InBinder] -> ([OutBinder] -> SimplM a) -> SimplM a
311 simplIds ids thing_inside
312 = getSubst `thenSmpl` \ subst ->
314 (subst', bndrs') = substIds subst ids
316 seqBndrs bndrs' `seq`
317 setSubst subst' (thing_inside bndrs')
320 seqBndrs (b:bs) = seqBndr b `seq` seqBndrs bs
322 seqBndr b | isTyVar b = b `seq` ()
323 | otherwise = seqType (idType b) `seq`
329 %************************************************************************
331 \subsection{Transform a RHS}
333 %************************************************************************
335 Try (a) eta expansion
336 (b) type-lambda swizzling
339 transformRhs :: InExpr -> SimplM InExpr
341 = tryEtaExpansion body `thenSmpl` \ body' ->
342 mkRhsTyLam tyvars body'
344 (tyvars, body) = collectTyBinders rhs
348 %************************************************************************
350 \subsection{Local tyvar-lifting}
352 %************************************************************************
354 mkRhsTyLam tries this transformation, when the big lambda appears as
355 the RHS of a let(rec) binding:
357 /\abc -> let(rec) x = e in b
359 let(rec) x' = /\abc -> let x = x' a b c in e
361 /\abc -> let x = x' a b c in b
363 This is good because it can turn things like:
365 let f = /\a -> letrec g = ... g ... in g
367 letrec g' = /\a -> ... g' a ...
371 which is better. In effect, it means that big lambdas don't impede
374 This optimisation is CRUCIAL in eliminating the junk introduced by
375 desugaring mutually recursive definitions. Don't eliminate it lightly!
377 So far as the implemtation is concerned:
379 Invariant: go F e = /\tvs -> F e
383 = Let x' = /\tvs -> F e
387 G = F . Let x = x' tvs
389 go F (Letrec xi=ei in b)
390 = Letrec {xi' = /\tvs -> G ei}
394 G = F . Let {xi = xi' tvs}
396 [May 1999] If we do this transformation *regardless* then we can
397 end up with some pretty silly stuff. For example,
400 st = /\ s -> let { x1=r1 ; x2=r2 } in ...
405 st = /\s -> ...[y1 s/x1, y2 s/x2]
408 Unless the "..." is a WHNF there is really no point in doing this.
409 Indeed it can make things worse. Suppose x1 is used strictly,
412 x1* = case f y of { (a,b) -> e }
414 If we abstract this wrt the tyvar we then can't do the case inline
415 as we would normally do.
419 mkRhsTyLam tyvars body -- Only does something if there's a let
420 | null tyvars || not (worth_it body) -- inside a type lambda, and a WHNF inside that
421 = returnSmpl (mkLams tyvars body)
425 worth_it (Let _ e) = whnf_in_middle e
426 worth_it other = False
427 whnf_in_middle (Let _ e) = whnf_in_middle e
428 whnf_in_middle e = exprIsCheap e
430 main_tyvar_set = mkVarSet tyvars
432 go fn (Let bind@(NonRec var rhs) body) | exprIsTrivial rhs
433 = go (fn . Let bind) body
435 go fn (Let bind@(NonRec var rhs) body)
436 = mk_poly tyvars_here var `thenSmpl` \ (var', rhs') ->
437 go (fn . Let (mk_silly_bind var rhs')) body `thenSmpl` \ body' ->
438 returnSmpl (Let (NonRec var' (mkLams tyvars_here (fn rhs))) body')
441 -- varSetElems (main_tyvar_set `intersectVarSet` tyVarsOfType var_ty)
442 -- tyvars_here was an attempt to reduce the number of tyvars
443 -- wrt which the new binding is abstracted. But the naive
444 -- approach of abstract wrt the tyvars free in the Id's type
446 -- /\ a b -> let t :: (a,b) = (e1, e2)
449 -- Here, b isn't free in x's type, but we must nevertheless
450 -- abstract wrt b as well, because t's type mentions b.
451 -- Since t is floated too, we'd end up with the bogus:
452 -- poly_t = /\ a b -> (e1, e2)
453 -- poly_x = /\ a -> fst (poly_t a *b*)
454 -- So for now we adopt the even more naive approach of
455 -- abstracting wrt *all* the tyvars. We'll see if that
456 -- gives rise to problems. SLPJ June 98
460 go fn (Let (Rec prs) body)
461 = mapAndUnzipSmpl (mk_poly tyvars_here) vars `thenSmpl` \ (vars', rhss') ->
463 gn body = fn $ foldr Let body (zipWith mk_silly_bind vars rhss')
465 go gn body `thenSmpl` \ body' ->
466 returnSmpl (Let (Rec (vars' `zip` [mkLams tyvars_here (gn rhs) | rhs <- rhss])) body')
468 (vars,rhss) = unzip prs
470 -- varSetElems (main_tyvar_set `intersectVarSet` tyVarsOfTypes var_tys)
471 -- See notes with tyvars_here above
473 var_tys = map idType vars
475 go fn body = returnSmpl (mkLams tyvars (fn body))
477 mk_poly tyvars_here var
478 = getUniqueSmpl `thenSmpl` \ uniq ->
480 poly_name = setNameUnique (idName var) uniq -- Keep same name
481 poly_ty = mkForAllTys tyvars_here (idType var) -- But new type of course
483 -- It's crucial to copy the occInfo of the original var, because
484 -- we're looking at occurrence-analysed but as yet unsimplified code!
485 -- In particular, we mustn't lose the loop breakers.
487 -- It's even right to retain single-occurrence or dead-var info:
488 -- Suppose we started with /\a -> let x = E in B
489 -- where x occurs once in E. Then we transform to:
490 -- let x' = /\a -> E in /\a -> let x* = x' a in B
491 -- where x* has an INLINE prag on it. Now, once x* is inlined,
492 -- the occurrences of x' will be just the occurrences originaly
494 poly_info = vanillaIdInfo `setOccInfo` idOccInfo var
496 poly_id = mkId poly_name poly_ty poly_info
498 returnSmpl (poly_id, mkTyApps (Var poly_id) (mkTyVarTys tyvars_here))
500 mk_silly_bind var rhs = NonRec var rhs
501 -- The Inline note is really important! If we don't say
502 -- INLINE on these silly little bindings then look what happens!
503 -- Suppose we start with:
505 -- x = let g = /\a -> \x -> f x x
507 -- /\ b -> let g* = g b in E
509 -- Then: * the binding for g gets floated out
510 -- * but then it gets inlined into the rhs of g*
511 -- * then the binding for g* is floated out of the /\b
512 -- * so we're back to square one
513 -- The silly binding for g* must be INLINEd, so that
514 -- we simply substitute for g* throughout.
518 %************************************************************************
520 \subsection{Eta expansion}
522 %************************************************************************
524 Try eta expansion for RHSs
527 \x1..xn -> N ==> \x1..xn y1..ym -> N y1..ym
529 N E1..En ==> let z1=E1 .. zn=En in \y1..ym -> N z1..zn y1..ym
531 where (in both cases) N is a NORMAL FORM (i.e. no redexes anywhere)
532 wanting a suitable number of extra args.
534 NB: the Ei may have unlifted type, but the simplifier (which is applied
535 to the result) deals OK with this.
537 There is no point in looking for a combination of the two,
538 because that would leave use with some lets sandwiched between lambdas;
539 that's what the final test in the first equation is for.
542 tryEtaExpansion :: InExpr -> SimplM InExpr
544 | not opt_SimplDoLambdaEtaExpansion
545 || exprIsTrivial rhs -- Don't eta-expand a trival RHS
546 || null y_tys -- No useful expansion
547 || not (null x_bndrs || and trivial_args) -- Not (no x-binders or no z-binds)
550 | otherwise -- Consider eta expansion
551 = newIds y_tys $ ( \ y_bndrs ->
552 tick (EtaExpansion (head y_bndrs)) `thenSmpl_`
553 mapAndUnzipSmpl bind_z_arg (args `zip` trivial_args) `thenSmpl` (\ (maybe_z_binds, z_args) ->
554 returnSmpl (mkLams x_bndrs $
555 mkLets (catMaybes maybe_z_binds) $
557 mkApps (mkApps fun z_args) (map Var y_bndrs))))
559 (x_bndrs, body) = collectValBinders rhs
560 (fun, args) = collectArgs body
561 trivial_args = map exprIsTrivial args
562 fun_arity = exprEtaExpandArity fun
564 bind_z_arg (arg, trivial_arg)
565 | trivial_arg = returnSmpl (Nothing, arg)
566 | otherwise = newId (exprType arg) $ \ z ->
567 returnSmpl (Just (NonRec z arg), Var z)
569 -- Note: I used to try to avoid the exprType call by using
570 -- the type of the binder. But this type doesn't necessarily
571 -- belong to the same substitution environment as this rhs;
572 -- and we are going to make extra term binders (y_bndrs) from the type
573 -- which will be processed with the rhs substitution environment.
574 -- This only went wrong in a mind bendingly complicated case.
575 (potential_extra_arg_tys, inner_ty) = splitFunTys (exprType body)
578 y_tys = take no_extras_wanted potential_extra_arg_tys
580 no_extras_wanted :: Int
581 no_extras_wanted = 0 `max`
583 -- We used to expand the arity to the previous arity fo the
584 -- function; but this is pretty dangerous. Consdier
586 -- so that f has arity 2. Now float something into f's RHS:
587 -- f = let z = BIG in \xy -> e
588 -- The last thing we want to do now is to put some lambdas
590 -- f = \xy -> let z = BIG in e
592 -- (bndr_arity - no_of_xs) `max`
594 -- See if the body could obviously do with more args
595 (fun_arity - valArgCount args)
597 -- This case is now deal with by exprEtaExpandArity
598 -- Finally, see if it's a state transformer, and xs is non-null
599 -- (so it's also a function not a thunk) in which
600 -- case we eta-expand on principle! This can waste work,
601 -- but usually doesn't.
602 -- I originally checked for a singleton type [ty] in this case
603 -- but then I found a situation in which I had
604 -- \ x -> let {..} in \ s -> f (...) s
605 -- AND f RETURNED A FUNCTION. That is, 's' wasn't the only
606 -- potential extra arg.
607 -- case (x_bndrs, potential_extra_arg_tys) of
608 -- (_:_, ty:_) -> case splitTyConApp_maybe ty of
609 -- Just (tycon,_) | tycon == statePrimTyCon -> 1
615 %************************************************************************
617 \subsection{Case absorption and identity-case elimination}
619 %************************************************************************
622 mkCase :: OutExpr -> OutId -> [OutAlt] -> SimplM OutExpr
625 @mkCase@ tries the following transformation (if possible):
627 case e of b { ==> case e of b {
628 p1 -> rhs1 p1 -> rhs1
630 pm -> rhsm pm -> rhsm
631 _ -> case b of b' { pn -> rhsn[b/b'] {or (alg) let b=b' in rhsn}
632 {or (prim) case b of b' { _ -> rhsn}}
635 po -> rhso _ -> rhsd[b/b'] {or let b'=b in rhsd}
639 which merges two cases in one case when -- the default alternative of
640 the outer case scrutises the same variable as the outer case This
641 transformation is called Case Merging. It avoids that the same
642 variable is scrutinised multiple times.
645 mkCase scrut outer_bndr outer_alts
647 && maybeToBool maybe_case_in_default
649 = tick (CaseMerge outer_bndr) `thenSmpl_`
650 returnSmpl (Case scrut outer_bndr new_alts)
651 -- Warning: don't call mkCase recursively!
652 -- Firstly, there's no point, because inner alts have already had
653 -- mkCase applied to them, so they won't have a case in their default
654 -- Secondly, if you do, you get an infinite loop, because the bindNonRec
655 -- in munge_rhs puts a case into the DEFAULT branch!
657 new_alts = outer_alts_without_deflt ++ munged_inner_alts
658 maybe_case_in_default = case findDefault outer_alts of
659 (outer_alts_without_default,
660 Just (Case (Var scrut_var) inner_bndr inner_alts))
662 | outer_bndr == scrut_var
663 -> Just (outer_alts_without_default, inner_bndr, inner_alts)
666 Just (outer_alts_without_deflt, inner_bndr, inner_alts) = maybe_case_in_default
668 -- Eliminate any inner alts which are shadowed by the outer ones
669 outer_cons = [con | (con,_,_) <- outer_alts_without_deflt]
671 munged_inner_alts = [ (con, args, munge_rhs rhs)
672 | (con, args, rhs) <- inner_alts,
673 not (con `elem` outer_cons) -- Eliminate shadowed inner alts
675 munge_rhs rhs = bindNonRec inner_bndr (Var outer_bndr) rhs
678 Now the identity-case transformation:
687 mkCase scrut case_bndr alts
688 | all identity_alt alts
689 = tick (CaseIdentity case_bndr) `thenSmpl_`
692 identity_alt (DEFAULT, [], Var v) = v == case_bndr
693 identity_alt (DataAlt con, args, rhs) = cheapEqExpr rhs
694 (mkConApp con (map Type arg_tys ++ map varToCoreExpr args))
695 identity_alt other = False
697 arg_tys = case splitTyConApp_maybe (idType case_bndr) of
698 Just (tycon, arg_tys) -> arg_tys
704 mkCase other_scrut case_bndr other_alts
705 = returnSmpl (Case other_scrut case_bndr other_alts)
710 findDefault :: [CoreAlt] -> ([CoreAlt], Maybe CoreExpr)
711 findDefault [] = ([], Nothing)
712 findDefault ((DEFAULT,args,rhs) : alts) = ASSERT( null alts && null args )
714 findDefault (alt : alts) = case findDefault alts of
715 (alts', deflt) -> (alt : alts', deflt)
717 findAlt :: AltCon -> [CoreAlt] -> CoreAlt
721 go [] = pprPanic "Missing alternative" (ppr con $$ vcat (map ppr alts))
722 go (alt : alts) | matches alt = alt
723 | otherwise = go alts
725 matches (DEFAULT, _, _) = True
726 matches (con1, _, _) = con == con1