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, simplIdInfo,
27 substAndCloneId, substAndCloneIds, substAndCloneRecIds,
30 mkTyVarSubst, mkTopTyVarSubst,
31 substTyWith, substTy, substTheta,
34 substExpr, substIdInfo
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
44 import CoreFVs ( exprFreeVars )
45 import TypeRep ( Type(..), TyNote(..) ) -- friend
46 import Type ( ThetaType, SourceType(..), PredType,
47 tyVarsOfType, tyVarsOfTypes, mkAppTy, mkUTy, isUTy,
52 import Var ( setVarUnique, isId, mustHaveLocalBinding )
53 import Id ( idType, idInfo, setIdInfo, setIdType,
54 idOccInfo, maybeModifyIdInfo )
55 import IdInfo ( IdInfo, vanillaIdInfo,
56 occInfo, isFragileOcc, setOccInfo,
57 specInfo, setSpecInfo,
58 unfoldingInfo, setUnfoldingInfo,
59 WorkerInfo(..), workerExists, workerInfo, setWorkerInfo, WorkerInfo,
60 lbvarInfo, LBVarInfo(..), setLBVarInfo, hasNoLBVarInfo
62 import BasicTypes ( OccInfo(..) )
63 import Unique ( Unique, Uniquable(..), deriveUnique )
64 import UniqSet ( elemUniqSet_Directly )
65 import UniqSupply ( UniqSupply, uniqFromSupply, uniqsFromSupply )
66 import Var ( Var, Id, TyVar, isTyVar )
68 import PprCore () -- Instances
69 import UniqFM ( ufmToList ) -- Yuk (add a new op to VarEnv)
70 import Util ( mapAccumL, foldl2, seqList )
75 %************************************************************************
77 \subsection{The in-scope set}
79 %************************************************************************
82 data InScopeSet = InScope (VarEnv Var) FastInt
83 -- The Int# is a kind of hash-value used by uniqAway
84 -- For example, it might be the size of the set
85 -- INVARIANT: it's not zero; we use it as a multiplier in uniqAway
87 emptyInScopeSet :: InScopeSet
88 emptyInScopeSet = InScope emptyVarSet 1#
90 mkInScopeSet :: VarEnv Var -> InScopeSet
91 mkInScopeSet in_scope = InScope in_scope 1#
93 extendInScopeSet :: InScopeSet -> Var -> InScopeSet
94 extendInScopeSet (InScope in_scope n) v = InScope (extendVarEnv in_scope v v) (n +# 1#)
96 extendInScopeSetList :: InScopeSet -> [Var] -> InScopeSet
97 extendInScopeSetList (InScope in_scope n) vs
98 = InScope (foldl (\s v -> extendVarEnv s v v) in_scope vs)
99 (n +# iUnbox (length vs))
101 modifyInScopeSet :: InScopeSet -> Var -> Var -> InScopeSet
102 -- Exploit the fact that the in-scope "set" is really a map
103 -- Make old_v map to new_v
104 modifyInScopeSet (InScope in_scope n) old_v new_v = InScope (extendVarEnv in_scope old_v new_v) (n +# 1#)
106 delInScopeSet :: InScopeSet -> Var -> InScopeSet
107 delInScopeSet (InScope in_scope n) v = InScope (in_scope `delVarEnv` v) n
109 elemInScopeSet :: Var -> InScopeSet -> Bool
110 elemInScopeSet v (InScope in_scope n) = v `elemVarEnv` in_scope
112 lookupInScope :: InScopeSet -> Var -> Var
113 -- It's important to look for a fixed point
114 -- When we see (case x of y { I# v -> ... })
115 -- we add [x -> y] to the in-scope set (Simplify.simplCaseBinder).
116 -- When we lookup up an occurrence of x, we map to y, but then
117 -- we want to look up y in case it has acquired more evaluation information by now.
118 lookupInScope (InScope in_scope n) v
121 go v = case lookupVarEnv in_scope v of
122 Just v' | v == v' -> v' -- Reached a fixed point
124 Nothing -> WARN( mustHaveLocalBinding v, ppr v )
129 uniqAway :: InScopeSet -> Var -> Var
130 -- (uniqAway in_scope v) finds a unique that is not used in the
131 -- in-scope set, and gives that to v. It starts with v's current unique, of course,
132 -- in the hope that it won't have to change it, nad thereafter uses a combination
133 -- of that and the hash-code found in the in-scope set
134 uniqAway (InScope set n) var
135 | not (var `elemVarSet` set) = var -- Nothing to do
138 orig_unique = getUnique var
142 = pprPanic "uniqAway loop:" (ppr (iBox k) <+> text "tries" <+> ppr var <+> int (iBox n))
144 | uniq `elemUniqSet_Directly` set = try (k +# 1#)
146 | opt_PprStyle_Debug && k ># 3#
147 = pprTrace "uniqAway:" (ppr (iBox k) <+> text "tries" <+> ppr var <+> int (iBox n))
148 setVarUnique var uniq
150 | otherwise = setVarUnique var uniq
152 uniq = deriveUnique orig_unique (iBox (n *# k))
156 %************************************************************************
158 \subsection{Substitutions}
160 %************************************************************************
163 data Subst = Subst InScopeSet -- In scope
164 SubstEnv -- Substitution itself
165 -- INVARIANT 1: The (domain of the) in-scope set is a superset
166 -- of the free vars of the range of the substitution
167 -- that might possibly clash with locally-bound variables
168 -- in the thing being substituted in.
169 -- This is what lets us deal with name capture properly
170 -- It's a hard invariant to check...
171 -- There are various ways of causing it to happen:
172 -- - arrange that the in-scope set really is all the things in scope
173 -- - arrange that it's the free vars of the range of the substitution
174 -- - make it empty because all the free vars of the subst are fresh,
175 -- and hence can't possibly clash.a
177 -- INVARIANT 2: No variable is both in scope and in the domain of the substitution
178 -- Equivalently, the substitution is idempotent
179 -- [Sep 2000: Lies, all lies. The substitution now does contain
180 -- mappings x77 -> DoneId x77 occ
181 -- to record x's occurrence information.]
182 -- [Also watch out: the substitution can contain x77 -> DoneEx (Var x77)
183 -- Consider let x = case k of I# x77 -> ... in
184 -- let y = case k of I# x77 -> ... in ...
185 -- and suppose the body is strict in both x and y. Then the simplifier
186 -- will pull the first (case k) to the top; so the second (case k) will
187 -- cancel out, mapping x77 to, well, x77! But one is an in-Id and the
188 -- other is an out-Id. So the substitution is idempotent in the sense
189 -- that we *must not* repeatedly apply it.]
194 The general plan about the substitution and in-scope set for Ids is as follows
196 * substId always adds new_id to the in-scope set.
197 new_id has a correctly-substituted type, occ info
199 * substId adds a binding (DoneId new_id occ) to the substitution if
200 EITHER the Id's unique has changed
201 OR the Id has interesting occurrence information
202 So in effect you can only get to interesting occurrence information
203 by looking up the *old* Id; it's not really attached to the new id
206 Note, though that the substitution isn't necessarily extended
207 if the type changes. Why not? Because of the next point:
209 * We *always, always* finish by looking up in the in-scope set
210 any variable that doesn't get a DoneEx or DoneVar hit in the substitution.
211 Reason: so that we never finish up with a "old" Id in the result.
212 An old Id might point to an old unfolding and so on... which gives a space leak.
214 [The DoneEx and DoneVar hits map to "new" stuff.]
216 * It follows that substExpr must not do a no-op if the substitution is empty.
217 substType is free to do so, however.
219 * When we come to a let-binding (say) we generate new IdInfo, including an
220 unfolding, attach it to the binder, and add this newly adorned binder to
221 the in-scope set. So all subsequent occurrences of the binder will get mapped
222 to the full-adorned binder, which is also the one put in the binding site.
224 * The in-scope "set" usually maps x->x; we use it simply for its domain.
225 But sometimes we have two in-scope Ids that are synomyms, and should
226 map to the same target: x->x, y->x. Notably:
228 That's why the "set" is actually a VarEnv Var
232 isEmptySubst :: Subst -> Bool
233 isEmptySubst (Subst _ env) = isEmptySubstEnv env
236 emptySubst = Subst emptyInScopeSet emptySubstEnv
238 mkSubst :: InScopeSet -> SubstEnv -> Subst
239 mkSubst in_scope env = Subst in_scope env
241 substEnv :: Subst -> SubstEnv
242 substEnv (Subst _ env) = env
244 substInScope :: Subst -> InScopeSet
245 substInScope (Subst in_scope _) = in_scope
247 zapSubstEnv :: Subst -> Subst
248 zapSubstEnv (Subst in_scope env) = Subst in_scope emptySubstEnv
250 extendSubst :: Subst -> Var -> SubstResult -> Subst
251 extendSubst (Subst in_scope env) v r = UASSERT( case r of { DoneTy ty -> not (isUTy ty) ; _ -> True } )
252 Subst in_scope (extendSubstEnv env v r)
254 extendSubstList :: Subst -> [Var] -> [SubstResult] -> Subst
255 extendSubstList (Subst in_scope env) v r = UASSERT( all (\ r1 -> case r1 of { DoneTy ty -> not (isUTy ty) ; _ -> True }) r )
256 Subst in_scope (extendSubstEnvList env v r)
258 lookupSubst :: Subst -> Var -> Maybe SubstResult
259 lookupSubst (Subst _ env) v = lookupSubstEnv env v
261 lookupIdSubst :: Subst -> Id -> SubstResult
262 -- Does the lookup in the in-scope set too
263 lookupIdSubst (Subst in_scope env) v
264 = case lookupSubstEnv env v of
265 Just (DoneId v' occ) -> DoneId (lookupInScope in_scope v') occ
267 Nothing -> DoneId v' (idOccInfo v')
268 -- We don't use DoneId for LoopBreakers, so the idOccInfo is
269 -- very important! If isFragileOcc returned True for
270 -- loop breakers we could avoid this call, but at the expense
271 -- of adding more to the substitution, and building new Ids
272 -- in substId a bit more often than really necessary
274 v' = lookupInScope in_scope v
276 isInScope :: Var -> Subst -> Bool
277 isInScope v (Subst in_scope _) = v `elemInScopeSet` in_scope
279 modifyInScope :: Subst -> Var -> Var -> Subst
280 modifyInScope (Subst in_scope env) old_v new_v = Subst (modifyInScopeSet in_scope old_v new_v) env
281 -- make old_v map to new_v
283 extendInScope :: Subst -> Var -> Subst
284 -- Add a new variable as in-scope
285 -- Remember to delete any existing binding in the substitution!
286 extendInScope (Subst in_scope env) v = Subst (in_scope `extendInScopeSet` v)
287 (env `delSubstEnv` v)
289 extendInScopeList :: Subst -> [Var] -> Subst
290 extendInScopeList (Subst in_scope env) vs = Subst (extendInScopeSetList in_scope vs)
291 (delSubstEnvList env vs)
293 -- The "New" variants are guaranteed to be adding freshly-allocated variables
294 -- It's not clear that the gain (not needing to delete it from the substitution)
295 -- is worth the extra proof obligation
296 extendNewInScope :: Subst -> Var -> Subst
297 extendNewInScope (Subst in_scope env) v = Subst (in_scope `extendInScopeSet` v) env
299 extendNewInScopeList :: Subst -> [Var] -> Subst
300 extendNewInScopeList (Subst in_scope env) vs = Subst (in_scope `extendInScopeSetList` vs) env
302 -------------------------------
303 bindSubst :: Subst -> Var -> Var -> Subst
304 -- Extend with a substitution, v1 -> Var v2
305 -- and extend the in-scopes with v2
306 bindSubst (Subst in_scope env) old_bndr new_bndr
307 = Subst (in_scope `extendInScopeSet` new_bndr)
308 (extendSubstEnv env old_bndr subst_result)
310 subst_result | isId old_bndr = DoneEx (Var new_bndr)
311 | otherwise = DoneTy (TyVarTy new_bndr)
313 unBindSubst :: Subst -> Var -> Var -> Subst
314 -- Reverse the effect of bindSubst
315 -- If old_bndr was already in the substitution, this doesn't quite work
316 unBindSubst (Subst in_scope env) old_bndr new_bndr
317 = Subst (in_scope `delInScopeSet` new_bndr) (delSubstEnv env old_bndr)
319 -- And the "List" forms
320 bindSubstList :: Subst -> [Var] -> [Var] -> Subst
321 bindSubstList subst old_bndrs new_bndrs
322 = foldl2 bindSubst subst old_bndrs new_bndrs
324 unBindSubstList :: Subst -> [Var] -> [Var] -> Subst
325 unBindSubstList subst old_bndrs new_bndrs
326 = foldl2 unBindSubst subst old_bndrs new_bndrs
329 -------------------------------
330 setInScope :: Subst -- Take env part from here
333 setInScope (Subst in_scope1 env1) in_scope2
334 = Subst in_scope2 env1
336 setSubstEnv :: Subst -- Take in-scope part from here
337 -> SubstEnv -- ... and env part from here
339 setSubstEnv (Subst in_scope1 _) env2 = Subst in_scope1 env2
342 Pretty printing, for debugging only
345 instance Outputable SubstResult where
346 ppr (DoneEx e) = ptext SLIT("DoneEx") <+> ppr e
347 ppr (DoneId v _) = ptext SLIT("DoneId") <+> ppr v
348 ppr (ContEx _ e) = ptext SLIT("ContEx") <+> ppr e
349 ppr (DoneTy t) = ptext SLIT("DoneTy") <+> ppr t
351 instance Outputable SubstEnv where
352 ppr se = brackets (fsep (punctuate comma (map ppr_elt (ufmToList (substEnvEnv se)))))
354 ppr_elt (uniq,sr) = ppr uniq <+> ptext SLIT("->") <+> ppr sr
356 instance Outputable Subst where
357 ppr (Subst (InScope in_scope _) se)
358 = ptext SLIT("<InScope =") <+> braces (fsep (map ppr (rngVarEnv in_scope)))
359 $$ ptext SLIT(" Subst =") <+> ppr se <> char '>'
362 %************************************************************************
364 \subsection{Type substitution}
366 %************************************************************************
369 type TyVarSubst = Subst -- TyVarSubst are expected to have range elements
370 -- (We could have a variant of Subst, but it doesn't seem worth it.)
372 -- mkTyVarSubst generates the in-scope set from
373 -- the types given; but it's just a thunk so with a bit of luck
374 -- it'll never be evaluated
375 mkTyVarSubst :: [TyVar] -> [Type] -> Subst
376 mkTyVarSubst tyvars tys = Subst (mkInScopeSet (tyVarsOfTypes tys))
377 (zip_ty_env tyvars tys emptySubstEnv)
379 -- mkTopTyVarSubst is called when doing top-level substitutions.
380 -- Here we expect that the free vars of the range of the
381 -- substitution will be empty.
382 mkTopTyVarSubst :: [TyVar] -> [Type] -> Subst
383 mkTopTyVarSubst tyvars tys = Subst emptyInScopeSet (zip_ty_env tyvars tys emptySubstEnv)
385 zip_ty_env [] [] env = env
386 zip_ty_env (tv:tvs) (ty:tys) env
387 | Just tv' <- getTyVar_maybe ty, tv==tv' = zip_ty_env tvs tys env
388 -- Shortcut for the (I think not uncommon) case where we are
389 -- making an identity substitution
390 | otherwise = zip_ty_env tvs tys (extendSubstEnv env tv (DoneTy ty))
393 substTy works with general Substs, so that it can be called from substExpr too.
396 substTyWith :: [TyVar] -> [Type] -> Type -> Type
397 substTyWith tvs tys = substTy (mkTyVarSubst tvs tys)
399 substTy :: Subst -> Type -> Type
400 substTy subst ty | isEmptySubst subst = ty
401 | otherwise = subst_ty subst ty
403 substTheta :: TyVarSubst -> ThetaType -> ThetaType
404 substTheta subst theta
405 | isEmptySubst subst = theta
406 | otherwise = map (substPred subst) theta
408 substPred :: TyVarSubst -> PredType -> PredType
409 substPred = substSourceType
411 substSourceType subst (IParam n ty) = IParam n (subst_ty subst ty)
412 substSourceType subst (ClassP clas tys) = ClassP clas (map (subst_ty subst) tys)
413 substSourceType subst (NType tc tys) = NType tc (map (subst_ty subst) tys)
418 go (TyConApp tc tys) = let args = map go tys
419 in args `seqList` TyConApp tc args
421 go (SourceTy p) = SourceTy $! (substSourceType subst p)
423 go (NoteTy (SynNote ty1) ty2) = NoteTy (SynNote $! (go ty1)) $! (go ty2)
424 go (NoteTy (FTVNote _) ty2) = go ty2 -- Discard the free tyvar note
426 go (FunTy arg res) = (FunTy $! (go arg)) $! (go res)
427 go (AppTy fun arg) = mkAppTy (go fun) $! (go arg)
428 go ty@(TyVarTy tv) = case (lookupSubst subst tv) of
430 Just (DoneTy ty') -> ty'
432 go (ForAllTy tv ty) = case substTyVar subst tv of
433 (subst', tv') -> ForAllTy tv' $! (subst_ty subst' ty)
435 go (UsageTy u ty) = mkUTy (go u) $! (go ty)
438 Here is where we invent a new binder if necessary.
441 substTyVar :: Subst -> TyVar -> (Subst, TyVar)
442 substTyVar subst@(Subst in_scope env) old_var
443 | old_var == new_var -- No need to clone
444 -- But we *must* zap any current substitution for the variable.
446 -- (\x.e) with id_subst = [x |-> e']
447 -- Here we must simply zap the substitution for x
449 -- The new_id isn't cloned, but it may have a different type
450 -- etc, so we must return it, not the old id
451 = (Subst (in_scope `extendInScopeSet` new_var)
452 (delSubstEnv env old_var),
455 | otherwise -- The new binder is in scope so
456 -- we'd better rename it away from the in-scope variables
457 -- Extending the substitution to do this renaming also
458 -- has the (correct) effect of discarding any existing
459 -- substitution for that variable
460 = (Subst (in_scope `extendInScopeSet` new_var)
461 (extendSubstEnv env old_var (DoneTy (TyVarTy new_var))),
464 new_var = uniqAway in_scope old_var
465 -- The uniqAway part makes sure the new variable is not already in scope
469 %************************************************************************
471 \section{Expression substitution}
473 %************************************************************************
475 This expression substituter deals correctly with name capture.
477 BUT NOTE that substExpr silently discards the
480 IdInfo attached to any binders in the expression. It's quite
481 tricky to do them 'right' in the case of mutually recursive bindings,
482 and so far has proved unnecessary.
485 substExpr :: Subst -> CoreExpr -> CoreExpr
487 -- NB: we do not do a no-op when the substitution is empty,
488 -- because we always want to substitute the variables in the
489 -- in-scope set for their occurrences. Why?
490 -- (a) because they may contain more information
491 -- (b) because leaving an un-substituted Id might cause
492 -- a space leak (its unfolding might point to an old version
493 -- of its right hand side).
497 go (Var v) = -- See the notes at the top, with the Subst data type declaration
498 case lookupIdSubst subst v of
500 ContEx env' e' -> substExpr (setSubstEnv subst env') e'
504 go (Type ty) = Type (go_ty ty)
505 go (Lit lit) = Lit lit
506 go (App fun arg) = App (go fun) (go arg)
507 go (Note note e) = Note (go_note note) (go e)
509 go (Lam bndr body) = Lam bndr' (substExpr subst' body)
511 (subst', bndr') = substBndr subst bndr
513 go (Let (NonRec bndr rhs) body) = Let (NonRec bndr' (go rhs)) (substExpr subst' body)
515 (subst', bndr') = substBndr subst bndr
517 go (Let (Rec pairs) body) = Let (Rec pairs') (substExpr subst' body)
519 (subst', bndrs') = substRecIds subst (map fst pairs)
520 pairs' = bndrs' `zip` rhss'
521 rhss' = map (substExpr subst' . snd) pairs
523 go (Case scrut bndr alts) = Case (go scrut) bndr' (map (go_alt subst') alts)
525 (subst', bndr') = substBndr subst bndr
527 go_alt subst (con, bndrs, rhs) = (con, bndrs', substExpr subst' rhs)
529 (subst', bndrs') = substBndrs subst bndrs
531 go_note (Coerce ty1 ty2) = Coerce (go_ty ty1) (go_ty ty2)
534 go_ty ty = substTy subst ty
539 %************************************************************************
541 \section{Substituting an Id binder}
543 %************************************************************************
546 -- simplBndr and simplLetId are used by the simplifier
548 simplBndr :: Subst -> Var -> (Subst, Var)
549 -- Used for lambda and case-bound variables
550 -- Clone Id if necessary, substitute type
551 -- Return with IdInfo already substituted, but (fragile) occurrence info zapped
552 -- The substitution is extended only if the variable is cloned, because
553 -- we *don't* need to use it to track occurrence info.
555 | isTyVar bndr = substTyVar subst bndr
556 | otherwise = subst_id isFragileOcc subst subst bndr
558 simplBndrs :: Subst -> [Var] -> (Subst, [Var])
559 simplBndrs subst bndrs = mapAccumL simplBndr subst bndrs
561 simplLetId :: Subst -> Id -> (Subst, Id)
562 -- Clone Id if necessary
563 -- Substitute its type
564 -- Return an Id with completely zapped IdInfo
565 -- [A subsequent substIdInfo will restore its IdInfo]
566 -- Augment the subtitution
567 -- if the unique changed, *or*
568 -- if there's interesting occurrence info
570 simplLetId subst@(Subst in_scope env) old_id
571 = (Subst (in_scope `extendInScopeSet` new_id) new_env, new_id)
573 old_info = idInfo old_id
574 id1 = uniqAway in_scope old_id
575 id2 = substIdType subst id1
576 new_id = setIdInfo id2 vanillaIdInfo
578 -- Extend the substitution if the unique has changed,
579 -- or there's some useful occurrence information
580 -- See the notes with substTyVar for the delSubstEnv
581 occ_info = occInfo old_info
582 new_env | new_id /= old_id || isFragileOcc occ_info
583 = extendSubstEnv env old_id (DoneId new_id occ_info)
585 = delSubstEnv env old_id
587 simplIdInfo :: Subst -> IdInfo -> Id -> Id
588 -- Used by the simplifier to compute new IdInfo for a let(rec) binder,
589 -- subsequent to simplLetId having zapped its IdInfo
590 simplIdInfo subst old_info bndr
591 = case substIdInfo subst isFragileOcc old_info of
592 Just new_info -> bndr `setIdInfo` new_info
593 Nothing -> bndr `setIdInfo` old_info
597 -- substBndr and friends are used when doing expression substitution only
598 -- In this case we can *preserve* occurrence information, and indeed we *want*
599 -- to do so else lose useful occ info in rules. Hence the calls to
600 -- simpl_id with keepOccInfo
602 substBndr :: Subst -> Var -> (Subst, Var)
604 | isTyVar bndr = substTyVar subst bndr
605 | otherwise = subst_id keepOccInfo subst subst bndr
607 substBndrs :: Subst -> [Var] -> (Subst, [Var])
608 substBndrs subst bndrs = mapAccumL substBndr subst bndrs
610 substRecIds :: Subst -> [Id] -> (Subst, [Id])
611 -- Substitute a mutually recursive group
612 substRecIds subst bndrs
613 = (new_subst, new_bndrs)
615 -- Here's the reason we need to pass rec_subst to subst_id
616 (new_subst, new_bndrs) = mapAccumL (subst_id keepOccInfo new_subst) subst bndrs
618 keepOccInfo occ = False -- Never fragile
623 subst_id :: (OccInfo -> Bool) -- True <=> the OccInfo is fragile
624 -> Subst -- Substitution to use for the IdInfo
625 -> Subst -> Id -- Substitition and Id to transform
626 -> (Subst, Id) -- Transformed pair
629 -- * Unique changed if necessary
630 -- * Type substituted
631 -- * Unfolding zapped
632 -- * Rules, worker, lbvar info all substituted
633 -- * Occurrence info zapped if is_fragile_occ returns True
634 -- * The in-scope set extended with the returned Id
635 -- * The substitution extended with a DoneId if unique changed
636 -- In this case, the var in the DoneId is the same as the
639 subst_id is_fragile_occ rec_subst subst@(Subst in_scope env) old_id
640 = (Subst (in_scope `extendInScopeSet` new_id) new_env, new_id)
642 -- id1 is cloned if necessary
643 id1 = uniqAway in_scope old_id
645 -- id2 has its type zapped
646 id2 = substIdType subst id1
648 -- new_id has the right IdInfo
649 -- The lazy-set is because we're in a loop here, with
650 -- rec_subst, when dealing with a mutually-recursive group
651 new_id = maybeModifyIdInfo (substIdInfo rec_subst is_fragile_occ) id2
653 -- Extend the substitution if the unique has changed
654 -- See the notes with substTyVar for the delSubstEnv
655 new_env | new_id /= old_id
656 = extendSubstEnv env old_id (DoneId new_id (idOccInfo old_id))
658 = delSubstEnv env old_id
661 Now a variant that unconditionally allocates a new unique.
662 It also unconditionally zaps the OccInfo.
665 subst_clone_id :: Subst -- Substitution to use (lazily) for the rules and worker
666 -> Subst -> (Id, Unique) -- Substitition and Id to transform
667 -> (Subst, Id) -- Transformed pair
669 subst_clone_id rec_subst subst@(Subst in_scope env) (old_id, uniq)
670 = (Subst (in_scope `extendInScopeSet` new_id) new_env, new_id)
672 id1 = setVarUnique old_id uniq
673 id2 = substIdType subst id1
675 new_id = maybeModifyIdInfo (substIdInfo rec_subst isFragileOcc) id2
676 new_env = extendSubstEnv env old_id (DoneId new_id NoOccInfo)
678 substAndCloneIds :: Subst -> UniqSupply -> [Id] -> (Subst, [Id])
679 substAndCloneIds subst us ids
680 = mapAccumL (subst_clone_id subst) subst (ids `zip` uniqsFromSupply us)
682 substAndCloneRecIds :: Subst -> UniqSupply -> [Id] -> (Subst, [Id])
683 substAndCloneRecIds subst us ids
686 (subst', ids') = mapAccumL (subst_clone_id subst') subst
687 (ids `zip` uniqsFromSupply us)
689 substAndCloneId :: Subst -> UniqSupply -> Id -> (Subst, Id)
690 substAndCloneId subst@(Subst in_scope env) us old_id
691 = subst_clone_id subst subst (old_id, uniqFromSupply us)
695 %************************************************************************
697 \section{IdInfo substitution}
699 %************************************************************************
703 -> (OccInfo -> Bool) -- True <=> zap the occurrence info
711 -- Zap the occ info if instructed to do so
713 -- Seq'ing on the returned IdInfo is enough to cause all the
714 -- substitutions to happen completely
716 substIdInfo subst is_fragile_occ info
717 | nothing_to_do = Nothing
718 | otherwise = Just (info `setOccInfo` (if zap_occ then NoOccInfo else old_occ)
719 `setSpecInfo` substRules subst old_rules
720 `setWorkerInfo` substWorker subst old_wrkr
721 `setLBVarInfo` substLBVar subst old_lbv
722 `setUnfoldingInfo` noUnfolding)
723 -- setSpecInfo does a seq
724 -- setWorkerInfo does a seq
726 nothing_to_do = not zap_occ &&
727 isEmptyCoreRules old_rules &&
728 not (workerExists old_wrkr) &&
729 hasNoLBVarInfo old_lbv &&
730 not (hasUnfolding (unfoldingInfo info))
732 zap_occ = is_fragile_occ old_occ
733 old_occ = occInfo info
734 old_rules = specInfo info
735 old_wrkr = workerInfo info
736 old_lbv = lbvarInfo info
738 substIdType :: Subst -> Id -> Id
739 substIdType subst@(Subst in_scope env) id
740 | noTypeSubst env || isEmptyVarSet (tyVarsOfType old_ty) = id
741 | otherwise = setIdType id (substTy subst old_ty)
742 -- The tyVarsOfType is cheaper than it looks
743 -- because we cache the free tyvars of the type
744 -- in a Note in the id's type itself
748 substWorker :: Subst -> WorkerInfo -> WorkerInfo
749 -- Seq'ing on the returned WorkerInfo is enough to cause all the
750 -- substitutions to happen completely
752 substWorker subst NoWorker
754 substWorker subst (HasWorker w a)
755 = case lookupIdSubst subst w of
756 (DoneId w1 _) -> HasWorker w1 a
757 (DoneEx (Var w1)) -> HasWorker w1 a
758 (DoneEx other) -> WARN( True, text "substWorker: DoneEx" <+> ppr w )
759 NoWorker -- Worker has got substituted away altogether
760 (ContEx se1 e) -> WARN( True, text "substWorker: ContEx" <+> ppr w <+> ppr e)
763 substRules :: Subst -> CoreRules -> CoreRules
764 -- Seq'ing on the returned CoreRules is enough to cause all the
765 -- substitutions to happen completely
767 substRules subst rules
768 | isEmptySubst subst = rules
770 substRules subst (Rules rules rhs_fvs)
771 = seqRules new_rules `seq` new_rules
773 new_rules = Rules (map do_subst rules) (substVarSet subst rhs_fvs)
775 do_subst rule@(BuiltinRule _) = rule
776 do_subst (Rule name tpl_vars lhs_args rhs)
777 = Rule name tpl_vars'
778 (map (substExpr subst') lhs_args)
779 (substExpr subst' rhs)
781 (subst', tpl_vars') = substBndrs subst tpl_vars
783 substVarSet subst fvs
784 = foldVarSet (unionVarSet . subst_fv subst) emptyVarSet fvs
786 subst_fv subst fv = case lookupIdSubst subst fv of
787 DoneId fv' _ -> unitVarSet fv'
788 DoneEx expr -> exprFreeVars expr
789 DoneTy ty -> tyVarsOfType ty
790 ContEx se' expr -> substVarSet (setSubstEnv subst se') (exprFreeVars expr)
792 substLBVar subst NoLBVarInfo = NoLBVarInfo
793 substLBVar subst (LBVarInfo ty) = ty1 `seq` LBVarInfo ty1
795 ty1 = substTy subst ty