2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[CoreUtils]{Utility functions on @Core@ syntax}
9 InScopeSet, emptyInScopeSet, mkInScopeSet,
10 extendInScopeSet, extendInScopeSetList,
11 lookupInScope, elemInScopeSet, uniqAway,
15 Subst, TyVarSubst, IdSubst,
16 emptySubst, mkSubst, substEnv, substInScope,
17 lookupSubst, lookupIdSubst, isEmptySubst, extendSubst, extendSubstList,
18 zapSubstEnv, setSubstEnv,
20 extendInScope, extendInScopeList, extendNewInScope, extendNewInScopeList,
21 isInScope, modifyInScope,
23 bindSubst, unBindSubst, bindSubstList, unBindSubstList,
26 simplBndr, simplBndrs, simplLetId, simplLamBndr, simplIdInfo,
27 substAndCloneId, substAndCloneIds, substAndCloneRecIds,
30 mkTyVarSubst, mkTopTyVarSubst,
31 substTyWith, substTy, substTheta,
37 #include "HsVersions.h"
39 import CmdLineOpts ( opt_PprStyle_Debug )
40 import CoreSyn ( Expr(..), Bind(..), Note(..), CoreExpr,
41 CoreRules(..), CoreRule(..),
42 isEmptyCoreRules, seqRules, hasUnfolding, noUnfolding, hasSomeUnfolding,
45 import CoreFVs ( exprFreeVars )
46 import TypeRep ( Type(..), TyNote(..) ) -- friend
47 import Type ( ThetaType, SourceType(..), PredType,
48 tyVarsOfType, tyVarsOfTypes, mkAppTy, mkUTy, isUTy
52 import Var ( setVarUnique, isId, mustHaveLocalBinding )
53 import Id ( idType, idInfo, setIdInfo, setIdType,
54 idUnfolding, setIdUnfolding,
55 idOccInfo, maybeModifyIdInfo )
56 import IdInfo ( IdInfo, vanillaIdInfo,
57 occInfo, isFragileOcc, setOccInfo,
58 specInfo, setSpecInfo,
59 unfoldingInfo, setUnfoldingInfo,
60 WorkerInfo(..), workerExists, workerInfo, setWorkerInfo, WorkerInfo,
61 lbvarInfo, LBVarInfo(..), setLBVarInfo, hasNoLBVarInfo
63 import BasicTypes ( OccInfo(..) )
64 import Unique ( Unique, Uniquable(..), deriveUnique )
65 import UniqSet ( elemUniqSet_Directly )
66 import UniqSupply ( UniqSupply, uniqFromSupply, uniqsFromSupply )
67 import Var ( Var, Id, TyVar, isTyVar )
69 import PprCore () -- Instances
70 import UniqFM ( ufmToList ) -- Yuk (add a new op to VarEnv)
71 import Util ( mapAccumL, foldl2, seqList )
76 %************************************************************************
78 \subsection{The in-scope set}
80 %************************************************************************
83 data InScopeSet = InScope (VarEnv Var) FastInt
84 -- The Int# is a kind of hash-value used by uniqAway
85 -- For example, it might be the size of the set
86 -- INVARIANT: it's not zero; we use it as a multiplier in uniqAway
88 emptyInScopeSet :: InScopeSet
89 emptyInScopeSet = InScope emptyVarSet 1#
91 mkInScopeSet :: VarEnv Var -> InScopeSet
92 mkInScopeSet in_scope = InScope in_scope 1#
94 extendInScopeSet :: InScopeSet -> Var -> InScopeSet
95 extendInScopeSet (InScope in_scope n) v = InScope (extendVarEnv in_scope v v) (n +# 1#)
97 extendInScopeSetList :: InScopeSet -> [Var] -> InScopeSet
98 extendInScopeSetList (InScope in_scope n) vs
99 = InScope (foldl (\s v -> extendVarEnv s v v) in_scope vs)
100 (n +# iUnbox (length vs))
102 modifyInScopeSet :: InScopeSet -> Var -> Var -> InScopeSet
103 -- Exploit the fact that the in-scope "set" is really a map
104 -- Make old_v map to new_v
105 modifyInScopeSet (InScope in_scope n) old_v new_v = InScope (extendVarEnv in_scope old_v new_v) (n +# 1#)
107 delInScopeSet :: InScopeSet -> Var -> InScopeSet
108 delInScopeSet (InScope in_scope n) v = InScope (in_scope `delVarEnv` v) n
110 elemInScopeSet :: Var -> InScopeSet -> Bool
111 elemInScopeSet v (InScope in_scope n) = v `elemVarEnv` in_scope
113 lookupInScope :: InScopeSet -> Var -> Var
114 -- It's important to look for a fixed point
115 -- When we see (case x of y { I# v -> ... })
116 -- we add [x -> y] to the in-scope set (Simplify.simplCaseBinder).
117 -- When we lookup up an occurrence of x, we map to y, but then
118 -- we want to look up y in case it has acquired more evaluation information by now.
119 lookupInScope (InScope in_scope n) v
122 go v = case lookupVarEnv in_scope v of
123 Just v' | v == v' -> v' -- Reached a fixed point
125 Nothing -> WARN( mustHaveLocalBinding v, ppr v )
130 uniqAway :: InScopeSet -> Var -> Var
131 -- (uniqAway in_scope v) finds a unique that is not used in the
132 -- in-scope set, and gives that to v. It starts with v's current unique, of course,
133 -- in the hope that it won't have to change it, nad thereafter uses a combination
134 -- of that and the hash-code found in the in-scope set
135 uniqAway (InScope set n) var
136 | not (var `elemVarSet` set) = var -- Nothing to do
139 orig_unique = getUnique var
143 = pprPanic "uniqAway loop:" (ppr (iBox k) <+> text "tries" <+> ppr var <+> int (iBox n))
145 | uniq `elemUniqSet_Directly` set = try (k +# 1#)
147 | opt_PprStyle_Debug && k ># 3#
148 = pprTrace "uniqAway:" (ppr (iBox k) <+> text "tries" <+> ppr var <+> int (iBox n))
149 setVarUnique var uniq
151 | otherwise = setVarUnique var uniq
153 uniq = deriveUnique orig_unique (iBox (n *# k))
157 %************************************************************************
159 \subsection{Substitutions}
161 %************************************************************************
164 data Subst = Subst InScopeSet -- In scope
165 SubstEnv -- Substitution itself
166 -- INVARIANT 1: The (domain of the) in-scope set is a superset
167 -- of the free vars of the range of the substitution
168 -- that might possibly clash with locally-bound variables
169 -- in the thing being substituted in.
170 -- This is what lets us deal with name capture properly
171 -- It's a hard invariant to check...
172 -- There are various ways of causing it to happen:
173 -- - arrange that the in-scope set really is all the things in scope
174 -- - arrange that it's the free vars of the range of the substitution
175 -- - make it empty because all the free vars of the subst are fresh,
176 -- and hence can't possibly clash.a
178 -- INVARIANT 2: No variable is both in scope and in the domain of the substitution
179 -- Equivalently, the substitution is idempotent
180 -- [Sep 2000: Lies, all lies. The substitution now does contain
181 -- mappings x77 -> DoneId x77 occ
182 -- to record x's occurrence information.]
183 -- [Also watch out: the substitution can contain x77 -> DoneEx (Var x77)
184 -- Consider let x = case k of I# x77 -> ... in
185 -- let y = case k of I# x77 -> ... in ...
186 -- and suppose the body is strict in both x and y. Then the simplifier
187 -- will pull the first (case k) to the top; so the second (case k) will
188 -- cancel out, mapping x77 to, well, x77! But one is an in-Id and the
189 -- other is an out-Id. So the substitution is idempotent in the sense
190 -- that we *must not* repeatedly apply it.]
195 The general plan about the substitution and in-scope set for Ids is as follows
197 * substId always adds new_id to the in-scope set.
198 new_id has a correctly-substituted type, occ info
200 * substId adds a binding (DoneId new_id occ) to the substitution if
201 EITHER the Id's unique has changed
202 OR the Id has interesting occurrence information
203 So in effect you can only get to interesting occurrence information
204 by looking up the *old* Id; it's not really attached to the new id
207 Note, though that the substitution isn't necessarily extended
208 if the type changes. Why not? Because of the next point:
210 * We *always, always* finish by looking up in the in-scope set
211 any variable that doesn't get a DoneEx or DoneVar hit in the substitution.
212 Reason: so that we never finish up with a "old" Id in the result.
213 An old Id might point to an old unfolding and so on... which gives a space leak.
215 [The DoneEx and DoneVar hits map to "new" stuff.]
217 * It follows that substExpr must not do a no-op if the substitution is empty.
218 substType is free to do so, however.
220 * When we come to a let-binding (say) we generate new IdInfo, including an
221 unfolding, attach it to the binder, and add this newly adorned binder to
222 the in-scope set. So all subsequent occurrences of the binder will get mapped
223 to the full-adorned binder, which is also the one put in the binding site.
225 * The in-scope "set" usually maps x->x; we use it simply for its domain.
226 But sometimes we have two in-scope Ids that are synomyms, and should
227 map to the same target: x->x, y->x. Notably:
229 That's why the "set" is actually a VarEnv Var
233 isEmptySubst :: Subst -> Bool
234 isEmptySubst (Subst _ env) = isEmptySubstEnv env
237 emptySubst = Subst emptyInScopeSet emptySubstEnv
239 mkSubst :: InScopeSet -> SubstEnv -> Subst
240 mkSubst in_scope env = Subst in_scope env
242 substEnv :: Subst -> SubstEnv
243 substEnv (Subst _ env) = env
245 substInScope :: Subst -> InScopeSet
246 substInScope (Subst in_scope _) = in_scope
248 zapSubstEnv :: Subst -> Subst
249 zapSubstEnv (Subst in_scope env) = Subst in_scope emptySubstEnv
251 extendSubst :: Subst -> Var -> SubstResult -> Subst
252 extendSubst (Subst in_scope env) v r = UASSERT( case r of { DoneTy ty -> not (isUTy ty) ; _ -> True } )
253 Subst in_scope (extendSubstEnv env v r)
255 extendSubstList :: Subst -> [Var] -> [SubstResult] -> Subst
256 extendSubstList (Subst in_scope env) v r = UASSERT( all (\ r1 -> case r1 of { DoneTy ty -> not (isUTy ty) ; _ -> True }) r )
257 Subst in_scope (extendSubstEnvList env v r)
259 lookupSubst :: Subst -> Var -> Maybe SubstResult
260 lookupSubst (Subst _ env) v = lookupSubstEnv env v
262 lookupIdSubst :: Subst -> Id -> SubstResult
263 -- Does the lookup in the in-scope set too
264 lookupIdSubst (Subst in_scope env) v
265 = case lookupSubstEnv env v of
266 Just (DoneId v' occ) -> DoneId (lookupInScope in_scope v') occ
268 Nothing -> DoneId v' (idOccInfo v')
269 -- We don't use DoneId for LoopBreakers, so the idOccInfo is
270 -- very important! If isFragileOcc returned True for
271 -- loop breakers we could avoid this call, but at the expense
272 -- of adding more to the substitution, and building new Ids
273 -- in substId a bit more often than really necessary
275 v' = lookupInScope in_scope v
277 isInScope :: Var -> Subst -> Bool
278 isInScope v (Subst in_scope _) = v `elemInScopeSet` in_scope
280 modifyInScope :: Subst -> Var -> Var -> Subst
281 modifyInScope (Subst in_scope env) old_v new_v = Subst (modifyInScopeSet in_scope old_v new_v) env
282 -- make old_v map to new_v
284 extendInScope :: Subst -> Var -> Subst
285 -- Add a new variable as in-scope
286 -- Remember to delete any existing binding in the substitution!
287 extendInScope (Subst in_scope env) v = Subst (in_scope `extendInScopeSet` v)
288 (env `delSubstEnv` v)
290 extendInScopeList :: Subst -> [Var] -> Subst
291 extendInScopeList (Subst in_scope env) vs = Subst (extendInScopeSetList in_scope vs)
292 (delSubstEnvList env vs)
294 -- The "New" variants are guaranteed to be adding freshly-allocated variables
295 -- It's not clear that the gain (not needing to delete it from the substitution)
296 -- is worth the extra proof obligation
297 extendNewInScope :: Subst -> Var -> Subst
298 extendNewInScope (Subst in_scope env) v = Subst (in_scope `extendInScopeSet` v) env
300 extendNewInScopeList :: Subst -> [Var] -> Subst
301 extendNewInScopeList (Subst in_scope env) vs = Subst (in_scope `extendInScopeSetList` vs) env
303 -------------------------------
304 bindSubst :: Subst -> Var -> Var -> Subst
305 -- Extend with a substitution, v1 -> Var v2
306 -- and extend the in-scopes with v2
307 bindSubst (Subst in_scope env) old_bndr new_bndr
308 = Subst (in_scope `extendInScopeSet` new_bndr)
309 (extendSubstEnv env old_bndr subst_result)
311 subst_result | isId old_bndr = DoneEx (Var new_bndr)
312 | otherwise = DoneTy (TyVarTy new_bndr)
314 unBindSubst :: Subst -> Var -> Var -> Subst
315 -- Reverse the effect of bindSubst
316 -- If old_bndr was already in the substitution, this doesn't quite work
317 unBindSubst (Subst in_scope env) old_bndr new_bndr
318 = Subst (in_scope `delInScopeSet` new_bndr) (delSubstEnv env old_bndr)
320 -- And the "List" forms
321 bindSubstList :: Subst -> [Var] -> [Var] -> Subst
322 bindSubstList subst old_bndrs new_bndrs
323 = foldl2 bindSubst subst old_bndrs new_bndrs
325 unBindSubstList :: Subst -> [Var] -> [Var] -> Subst
326 unBindSubstList subst old_bndrs new_bndrs
327 = foldl2 unBindSubst subst old_bndrs new_bndrs
330 -------------------------------
331 setInScope :: Subst -- Take env part from here
334 setInScope (Subst in_scope1 env1) in_scope2
335 = Subst in_scope2 env1
337 setSubstEnv :: Subst -- Take in-scope part from here
338 -> SubstEnv -- ... and env part from here
340 setSubstEnv (Subst in_scope1 _) env2 = Subst in_scope1 env2
343 Pretty printing, for debugging only
346 instance Outputable SubstResult where
347 ppr (DoneEx e) = ptext SLIT("DoneEx") <+> ppr e
348 ppr (DoneId v _) = ptext SLIT("DoneId") <+> ppr v
349 ppr (ContEx _ e) = ptext SLIT("ContEx") <+> ppr e
350 ppr (DoneTy t) = ptext SLIT("DoneTy") <+> ppr t
352 instance Outputable SubstEnv where
353 ppr se = brackets (fsep (punctuate comma (map ppr_elt (ufmToList (substEnvEnv se)))))
355 ppr_elt (uniq,sr) = ppr uniq <+> ptext SLIT("->") <+> ppr sr
357 instance Outputable Subst where
358 ppr (Subst (InScope in_scope _) se)
359 = ptext SLIT("<InScope =") <+> braces (fsep (map ppr (rngVarEnv in_scope)))
360 $$ ptext SLIT(" Subst =") <+> ppr se <> char '>'
363 %************************************************************************
365 \subsection{Type substitution}
367 %************************************************************************
370 type TyVarSubst = Subst -- TyVarSubst are expected to have range elements
371 -- (We could have a variant of Subst, but it doesn't seem worth it.)
373 -- mkTyVarSubst generates the in-scope set from
374 -- the types given; but it's just a thunk so with a bit of luck
375 -- it'll never be evaluated
376 mkTyVarSubst :: [TyVar] -> [Type] -> Subst
377 mkTyVarSubst tyvars tys = Subst (mkInScopeSet (tyVarsOfTypes tys))
378 (zip_ty_env tyvars tys emptySubstEnv)
380 -- mkTopTyVarSubst is called when doing top-level substitutions.
381 -- Here we expect that the free vars of the range of the
382 -- substitution will be empty.
383 mkTopTyVarSubst :: [TyVar] -> [Type] -> Subst
384 mkTopTyVarSubst tyvars tys = Subst emptyInScopeSet (zip_ty_env tyvars tys emptySubstEnv)
386 zip_ty_env [] [] env = env
387 zip_ty_env (tv:tvs) (ty:tys) env = zip_ty_env tvs tys (extendSubstEnv env tv (DoneTy ty))
388 -- There used to be a special case for when
390 -- (a not-uncommon case) in which case the substitution was dropped.
391 -- But the type-tidier changes the print-name of a type variable without
392 -- changing the unique, and that led to a bug. Why? Pre-tidying, we had
393 -- a type {Foo t}, where Foo is a one-method class. So Foo is really a newtype.
394 -- And it happened that t was the type variable of the class. Post-tiding,
395 -- it got turned into {Foo t2}. The ext-core printer expanded this using
396 -- sourceTypeRep, but that said "Oh, t == t2" because they have the same unique,
397 -- and so generated a rep type mentioning t not t2.
399 -- Simplest fix is to nuke the "optimisation"
402 substTy works with general Substs, so that it can be called from substExpr too.
405 substTyWith :: [TyVar] -> [Type] -> Type -> Type
406 substTyWith tvs tys = substTy (mkTyVarSubst tvs tys)
408 substTy :: Subst -> Type -> Type
409 substTy subst ty | isEmptySubst subst = ty
410 | otherwise = subst_ty subst ty
412 substTheta :: TyVarSubst -> ThetaType -> ThetaType
413 substTheta subst theta
414 | isEmptySubst subst = theta
415 | otherwise = map (substPred subst) theta
417 substPred :: TyVarSubst -> PredType -> PredType
418 substPred = substSourceType
420 substSourceType subst (IParam n ty) = IParam n (subst_ty subst ty)
421 substSourceType subst (ClassP clas tys) = ClassP clas (map (subst_ty subst) tys)
422 substSourceType subst (NType tc tys) = NType tc (map (subst_ty subst) tys)
427 go (TyConApp tc tys) = let args = map go tys
428 in args `seqList` TyConApp tc args
430 go (SourceTy p) = SourceTy $! (substSourceType subst p)
432 go (NoteTy (SynNote ty1) ty2) = NoteTy (SynNote $! (go ty1)) $! (go ty2)
433 go (NoteTy (FTVNote _) ty2) = go ty2 -- Discard the free tyvar note
435 go (FunTy arg res) = (FunTy $! (go arg)) $! (go res)
436 go (AppTy fun arg) = mkAppTy (go fun) $! (go arg)
437 go ty@(TyVarTy tv) = case (lookupSubst subst tv) of
439 Just (DoneTy ty') -> ty'
441 go (ForAllTy tv ty) = case substTyVar subst tv of
442 (subst', tv') -> ForAllTy tv' $! (subst_ty subst' ty)
444 go (UsageTy u ty) = mkUTy (go u) $! (go ty)
447 Here is where we invent a new binder if necessary.
450 substTyVar :: Subst -> TyVar -> (Subst, TyVar)
451 substTyVar subst@(Subst in_scope env) old_var
452 | old_var == new_var -- No need to clone
453 -- But we *must* zap any current substitution for the variable.
455 -- (\x.e) with id_subst = [x |-> e']
456 -- Here we must simply zap the substitution for x
458 -- The new_id isn't cloned, but it may have a different type
459 -- etc, so we must return it, not the old id
460 = (Subst (in_scope `extendInScopeSet` new_var)
461 (delSubstEnv env old_var),
464 | otherwise -- The new binder is in scope so
465 -- we'd better rename it away from the in-scope variables
466 -- Extending the substitution to do this renaming also
467 -- has the (correct) effect of discarding any existing
468 -- substitution for that variable
469 = (Subst (in_scope `extendInScopeSet` new_var)
470 (extendSubstEnv env old_var (DoneTy (TyVarTy new_var))),
473 new_var = uniqAway in_scope old_var
474 -- The uniqAway part makes sure the new variable is not already in scope
478 %************************************************************************
480 \section{Expression substitution}
482 %************************************************************************
484 This expression substituter deals correctly with name capture.
486 BUT NOTE that substExpr silently discards the
489 IdInfo attached to any binders in the expression. It's quite
490 tricky to do them 'right' in the case of mutually recursive bindings,
491 and so far has proved unnecessary.
494 substExpr :: Subst -> CoreExpr -> CoreExpr
496 -- NB: we do not do a no-op when the substitution is empty,
497 -- because we always want to substitute the variables in the
498 -- in-scope set for their occurrences. Why?
499 -- (a) because they may contain more information
500 -- (b) because leaving an un-substituted Id might cause
501 -- a space leak (its unfolding might point to an old version
502 -- of its right hand side).
506 go (Var v) = -- See the notes at the top, with the Subst data type declaration
507 case lookupIdSubst subst v of
509 ContEx env' e' -> substExpr (setSubstEnv subst env') e'
513 go (Type ty) = Type (go_ty ty)
514 go (Lit lit) = Lit lit
515 go (App fun arg) = App (go fun) (go arg)
516 go (Note note e) = Note (go_note note) (go e)
518 go (Lam bndr body) = Lam bndr' (substExpr subst' body)
520 (subst', bndr') = substBndr subst bndr
522 go (Let (NonRec bndr rhs) body) = Let (NonRec bndr' (go rhs)) (substExpr subst' body)
524 (subst', bndr') = substBndr subst bndr
526 go (Let (Rec pairs) body) = Let (Rec pairs') (substExpr subst' body)
528 (subst', bndrs') = substRecIds subst (map fst pairs)
529 pairs' = bndrs' `zip` rhss'
530 rhss' = map (substExpr subst' . snd) pairs
532 go (Case scrut bndr alts) = Case (go scrut) bndr' (map (go_alt subst') alts)
534 (subst', bndr') = substBndr subst bndr
536 go_alt subst (con, bndrs, rhs) = (con, bndrs', substExpr subst' rhs)
538 (subst', bndrs') = substBndrs subst bndrs
540 go_note (Coerce ty1 ty2) = Coerce (go_ty ty1) (go_ty ty2)
543 go_ty ty = substTy subst ty
548 %************************************************************************
550 \section{Substituting an Id binder}
552 %************************************************************************
555 -- simplBndr and simplLetId are used by the simplifier
557 simplBndr :: Subst -> Var -> (Subst, Var)
558 -- Used for lambda and case-bound variables
559 -- Clone Id if necessary, substitute type
560 -- Return with IdInfo already substituted, but (fragile) occurrence info zapped
561 -- The substitution is extended only if the variable is cloned, because
562 -- we *don't* need to use it to track occurrence info.
564 | isTyVar bndr = substTyVar subst bndr
565 | otherwise = subst_id isFragileOcc subst subst bndr
567 simplBndrs :: Subst -> [Var] -> (Subst, [Var])
568 simplBndrs subst bndrs = mapAccumL simplBndr subst bndrs
570 simplLamBndr :: Subst -> Var -> (Subst, Var)
571 -- Used for lambda binders. These sometimes have unfoldings added by
572 -- the worker/wrapper pass that must be preserved, becuase they can't
573 -- be reconstructed from context. For example:
574 -- f x = case x of (a,b) -> fw a b x
575 -- fw a b x{=(a,b)} = ...
576 -- The "{=(a,b)}" is an unfolding we can't reconstruct otherwise.
577 simplLamBndr subst bndr
578 | not (isId bndr && hasSomeUnfolding old_unf)
579 = simplBndr subst bndr -- Normal case
581 = (subst', bndr' `setIdUnfolding` substUnfolding subst old_unf)
583 old_unf = idUnfolding bndr
584 (subst', bndr') = subst_id isFragileOcc subst subst bndr
587 simplLetId :: Subst -> Id -> (Subst, Id)
588 -- Clone Id if necessary
589 -- Substitute its type
590 -- Return an Id with completely zapped IdInfo
591 -- [A subsequent substIdInfo will restore its IdInfo]
592 -- Augment the subtitution
593 -- if the unique changed, *or*
594 -- if there's interesting occurrence info
596 simplLetId subst@(Subst in_scope env) old_id
597 = (Subst (in_scope `extendInScopeSet` new_id) new_env, new_id)
599 old_info = idInfo old_id
600 id1 = uniqAway in_scope old_id
601 id2 = substIdType subst id1
602 new_id = setIdInfo id2 vanillaIdInfo
604 -- Extend the substitution if the unique has changed,
605 -- or there's some useful occurrence information
606 -- See the notes with substTyVar for the delSubstEnv
607 occ_info = occInfo old_info
608 new_env | new_id /= old_id || isFragileOcc occ_info
609 = extendSubstEnv env old_id (DoneId new_id occ_info)
611 = delSubstEnv env old_id
613 simplIdInfo :: Subst -> IdInfo -> Id -> Id
614 -- Used by the simplifier to compute new IdInfo for a let(rec) binder,
615 -- subsequent to simplLetId having zapped its IdInfo
616 simplIdInfo subst old_info bndr
617 = case substIdInfo subst isFragileOcc old_info of
618 Just new_info -> bndr `setIdInfo` new_info
619 Nothing -> bndr `setIdInfo` old_info
623 -- substBndr and friends are used when doing expression substitution only
624 -- In this case we can *preserve* occurrence information, and indeed we *want*
625 -- to do so else lose useful occ info in rules. Hence the calls to
626 -- simpl_id with keepOccInfo
628 substBndr :: Subst -> Var -> (Subst, Var)
630 | isTyVar bndr = substTyVar subst bndr
631 | otherwise = subst_id keepOccInfo subst subst bndr
633 substBndrs :: Subst -> [Var] -> (Subst, [Var])
634 substBndrs subst bndrs = mapAccumL substBndr subst bndrs
636 substRecIds :: Subst -> [Id] -> (Subst, [Id])
637 -- Substitute a mutually recursive group
638 substRecIds subst bndrs
639 = (new_subst, new_bndrs)
641 -- Here's the reason we need to pass rec_subst to subst_id
642 (new_subst, new_bndrs) = mapAccumL (subst_id keepOccInfo new_subst) subst bndrs
644 keepOccInfo occ = False -- Never fragile
649 subst_id :: (OccInfo -> Bool) -- True <=> the OccInfo is fragile
650 -> Subst -- Substitution to use for the IdInfo
651 -> Subst -> Id -- Substitition and Id to transform
652 -> (Subst, Id) -- Transformed pair
655 -- * Unique changed if necessary
656 -- * Type substituted
657 -- * Unfolding zapped
658 -- * Rules, worker, lbvar info all substituted
659 -- * Occurrence info zapped if is_fragile_occ returns True
660 -- * The in-scope set extended with the returned Id
661 -- * The substitution extended with a DoneId if unique changed
662 -- In this case, the var in the DoneId is the same as the
665 subst_id is_fragile_occ rec_subst subst@(Subst in_scope env) old_id
666 = (Subst (in_scope `extendInScopeSet` new_id) new_env, new_id)
668 -- id1 is cloned if necessary
669 id1 = uniqAway in_scope old_id
671 -- id2 has its type zapped
672 id2 = substIdType subst id1
674 -- new_id has the right IdInfo
675 -- The lazy-set is because we're in a loop here, with
676 -- rec_subst, when dealing with a mutually-recursive group
677 new_id = maybeModifyIdInfo (substIdInfo rec_subst is_fragile_occ) id2
679 -- Extend the substitution if the unique has changed
680 -- See the notes with substTyVar for the delSubstEnv
681 new_env | new_id /= old_id
682 = extendSubstEnv env old_id (DoneId new_id (idOccInfo old_id))
684 = delSubstEnv env old_id
687 Now a variant that unconditionally allocates a new unique.
688 It also unconditionally zaps the OccInfo.
691 subst_clone_id :: Subst -- Substitution to use (lazily) for the rules and worker
692 -> Subst -> (Id, Unique) -- Substitition and Id to transform
693 -> (Subst, Id) -- Transformed pair
695 subst_clone_id rec_subst subst@(Subst in_scope env) (old_id, uniq)
696 = (Subst (in_scope `extendInScopeSet` new_id) new_env, new_id)
698 id1 = setVarUnique old_id uniq
699 id2 = substIdType subst id1
701 new_id = maybeModifyIdInfo (substIdInfo rec_subst isFragileOcc) id2
702 new_env = extendSubstEnv env old_id (DoneId new_id NoOccInfo)
704 substAndCloneIds :: Subst -> UniqSupply -> [Id] -> (Subst, [Id])
705 substAndCloneIds subst us ids
706 = mapAccumL (subst_clone_id subst) subst (ids `zip` uniqsFromSupply us)
708 substAndCloneRecIds :: Subst -> UniqSupply -> [Id] -> (Subst, [Id])
709 substAndCloneRecIds subst us ids
712 (subst', ids') = mapAccumL (subst_clone_id subst') subst
713 (ids `zip` uniqsFromSupply us)
715 substAndCloneId :: Subst -> UniqSupply -> Id -> (Subst, Id)
716 substAndCloneId subst@(Subst in_scope env) us old_id
717 = subst_clone_id subst subst (old_id, uniqFromSupply us)
721 %************************************************************************
723 \section{IdInfo substitution}
725 %************************************************************************
729 -> (OccInfo -> Bool) -- True <=> zap the occurrence info
737 -- Zap the occ info if instructed to do so
739 -- Seq'ing on the returned IdInfo is enough to cause all the
740 -- substitutions to happen completely
742 substIdInfo subst is_fragile_occ info
743 | nothing_to_do = Nothing
744 | otherwise = Just (info `setOccInfo` (if zap_occ then NoOccInfo else old_occ)
745 `setSpecInfo` substRules subst old_rules
746 `setWorkerInfo` substWorker subst old_wrkr
747 `setLBVarInfo` substLBVar subst old_lbv
748 `setUnfoldingInfo` noUnfolding)
749 -- setSpecInfo does a seq
750 -- setWorkerInfo does a seq
752 nothing_to_do = not zap_occ &&
753 isEmptyCoreRules old_rules &&
754 not (workerExists old_wrkr) &&
755 hasNoLBVarInfo old_lbv &&
756 not (hasUnfolding (unfoldingInfo info))
758 zap_occ = is_fragile_occ old_occ
759 old_occ = occInfo info
760 old_rules = specInfo info
761 old_wrkr = workerInfo info
762 old_lbv = lbvarInfo info
765 substIdType :: Subst -> Id -> Id
766 substIdType subst@(Subst in_scope env) id
767 | noTypeSubst env || isEmptyVarSet (tyVarsOfType old_ty) = id
768 | otherwise = setIdType id (substTy subst old_ty)
769 -- The tyVarsOfType is cheaper than it looks
770 -- because we cache the free tyvars of the type
771 -- in a Note in the id's type itself
776 substWorker :: Subst -> WorkerInfo -> WorkerInfo
777 -- Seq'ing on the returned WorkerInfo is enough to cause all the
778 -- substitutions to happen completely
780 substWorker subst NoWorker
782 substWorker subst (HasWorker w a)
783 = case lookupIdSubst subst w of
784 (DoneId w1 _) -> HasWorker w1 a
785 (DoneEx (Var w1)) -> HasWorker w1 a
786 (DoneEx other) -> WARN( True, text "substWorker: DoneEx" <+> ppr w )
787 NoWorker -- Worker has got substituted away altogether
788 (ContEx se1 e) -> WARN( True, text "substWorker: ContEx" <+> ppr w <+> ppr e)
792 substUnfolding subst NoUnfolding = NoUnfolding
793 substUnfolding subst (OtherCon cons) = OtherCon cons
794 substUnfolding subst (CompulsoryUnfolding rhs) = CompulsoryUnfolding (substExpr subst rhs)
795 substUnfolding subst (CoreUnfolding rhs t v w g) = CoreUnfolding (substExpr subst rhs) t v w g
798 substRules :: Subst -> CoreRules -> CoreRules
799 -- Seq'ing on the returned CoreRules is enough to cause all the
800 -- substitutions to happen completely
802 substRules subst rules
803 | isEmptySubst subst = rules
805 substRules subst (Rules rules rhs_fvs)
806 = seqRules new_rules `seq` new_rules
808 new_rules = Rules (map do_subst rules) (substVarSet subst rhs_fvs)
810 do_subst rule@(BuiltinRule _ _) = rule
811 do_subst (Rule name act tpl_vars lhs_args rhs)
812 = Rule name act tpl_vars'
813 (map (substExpr subst') lhs_args)
814 (substExpr subst' rhs)
816 (subst', tpl_vars') = substBndrs subst tpl_vars
819 substVarSet subst fvs
820 = foldVarSet (unionVarSet . subst_fv subst) emptyVarSet fvs
822 subst_fv subst fv = case lookupIdSubst subst fv of
823 DoneId fv' _ -> unitVarSet fv'
824 DoneEx expr -> exprFreeVars expr
825 DoneTy ty -> tyVarsOfType ty
826 ContEx se' expr -> substVarSet (setSubstEnv subst se') (exprFreeVars expr)
829 substLBVar subst NoLBVarInfo = NoLBVarInfo
830 substLBVar subst (LBVarInfo ty) = ty1 `seq` LBVarInfo ty1
832 ty1 = substTy subst ty