2 % (c) The AQUA Project, Glasgow University, 1993-1998
4 \section[SimplMonad]{The simplifier Monad}
8 InId, InBind, InExpr, InAlt, InArg, InType, InBndr,
9 OutId, OutTyVar, OutBind, OutExpr, OutAlt, OutArg, OutType, OutBndr,
10 InCoercion, OutCoercion,
12 -- The simplifier mode
16 SwitchChecker, SwitchResult(..), getSwitchChecker, getSimplIntSwitch,
17 isAmongSimpl, intSwitchSet, switchIsOn,
19 setEnclosingCC, getEnclosingCC,
22 SimplEnv(..), pprSimplEnv, -- Temp not abstract
23 mkSimplEnv, extendIdSubst, SimplEnv.extendTvSubst,
24 zapSubstEnv, setSubstEnv,
25 getInScope, setInScope, setInScopeSet, modifyInScope, addNewInScopeIds,
28 SimplSR(..), mkContEx, substId, lookupRecBndr,
30 simplNonRecBndr, simplRecBndrs, simplLamBndr, simplLamBndrs,
31 simplBinder, simplBinders, addBndrRules,
32 substExpr, substWorker, substTy,
35 Floats, emptyFloats, isEmptyFloats, addNonRec, addFloats, extendFloats,
36 wrapFloats, floatBinds, setFloats, zapFloats, addRecFloats,
37 doFloatFromRhs, getFloats
40 #include "HsVersions.h"
52 import qualified CoreSubst ( Subst, mkSubst, substExpr, substSpec, substWorker )
53 import qualified Type ( substTy, substTyVarBndr )
54 import Type hiding ( substTy, substTyVarBndr )
65 %************************************************************************
67 \subsection[Simplify-types]{Type declarations}
69 %************************************************************************
72 type InBndr = CoreBndr
73 type InId = Id -- Not yet cloned
74 type InType = Type -- Ditto
75 type InBind = CoreBind
76 type InExpr = CoreExpr
79 type InCoercion = Coercion
81 type OutBndr = CoreBndr
82 type OutId = Id -- Cloned
83 type OutTyVar = TyVar -- Cloned
84 type OutType = Type -- Cloned
85 type OutCoercion = Coercion
86 type OutBind = CoreBind
87 type OutExpr = CoreExpr
92 %************************************************************************
94 \subsubsection{The @SimplEnv@ type}
96 %************************************************************************
102 seMode :: SimplifierMode,
103 seChkr :: SwitchChecker,
104 seCC :: CostCentreStack, -- The enclosing CCS (when profiling)
106 -- The current set of in-scope variables
107 -- They are all OutVars, and all bound in this module
108 seInScope :: InScopeSet, -- OutVars only
109 -- Includes all variables bound by seFloats
111 -- See Note [Simplifier floats]
113 -- The current substitution
114 seTvSubst :: TvSubstEnv, -- InTyVar |--> OutType
115 seIdSubst :: SimplIdSubst -- InId |--> OutExpr
119 pprSimplEnv :: SimplEnv -> SDoc
120 -- Used for debugging; selective
122 = vcat [ptext (sLit "TvSubst:") <+> ppr (seTvSubst env),
123 ptext (sLit "IdSubst:") <+> ppr (seIdSubst env) ]
125 type SimplIdSubst = IdEnv SimplSR -- IdId |--> OutExpr
126 -- See Note [Extending the Subst] in CoreSubst
129 = DoneEx OutExpr -- Completed term
130 | DoneId OutId -- Completed term variable
131 | ContEx TvSubstEnv -- A suspended substitution
135 instance Outputable SimplSR where
136 ppr (DoneEx e) = ptext (sLit "DoneEx") <+> ppr e
137 ppr (DoneId v) = ptext (sLit "DoneId") <+> ppr v
138 ppr (ContEx _tv _id e) = vcat [ptext (sLit "ContEx") <+> ppr e {-,
139 ppr (filter_env tv), ppr (filter_env id) -}]
141 -- fvs = exprFreeVars e
142 -- filter_env env = filterVarEnv_Directly keep env
143 -- keep uniq _ = uniq `elemUFM_Directly` fvs
148 The in-scope part of Subst includes *all* in-scope TyVars and Ids
149 The elements of the set may have better IdInfo than the
150 occurrences of in-scope Ids, and (more important) they will
151 have a correctly-substituted type. So we use a lookup in this
152 set to replace occurrences
154 The Ids in the InScopeSet are replete with their Rules,
155 and as we gather info about the unfolding of an Id, we replace
156 it in the in-scope set.
158 The in-scope set is actually a mapping OutVar -> OutVar, and
159 in case expressions we sometimes bind
162 The substitution is *apply-once* only, because InIds and OutIds can overlap.
163 For example, we generally omit mappings
165 from the substitution, when we decide not to clone a77, but it's quite
166 legitimate to put the mapping in the substitution anyway.
168 Furthermore, consider
169 let x = case k of I# x77 -> ... in
170 let y = case k of I# x77 -> ... in ...
171 and suppose the body is strict in both x and y. Then the simplifier
172 will pull the first (case k) to the top; so the second (case k) will
173 cancel out, mapping x77 to, well, x77! But one is an in-Id and the
176 Of course, the substitution *must* applied! Things in its domain
177 simply aren't necessarily bound in the result.
179 * substId adds a binding (DoneId new_id) to the substitution if
180 the Id's unique has changed
183 Note, though that the substitution isn't necessarily extended
184 if the type changes. Why not? Because of the next point:
186 * We *always, always* finish by looking up in the in-scope set
187 any variable that doesn't get a DoneEx or DoneVar hit in the substitution.
188 Reason: so that we never finish up with a "old" Id in the result.
189 An old Id might point to an old unfolding and so on... which gives a space leak.
191 [The DoneEx and DoneVar hits map to "new" stuff.]
193 * It follows that substExpr must not do a no-op if the substitution is empty.
194 substType is free to do so, however.
196 * When we come to a let-binding (say) we generate new IdInfo, including an
197 unfolding, attach it to the binder, and add this newly adorned binder to
198 the in-scope set. So all subsequent occurrences of the binder will get mapped
199 to the full-adorned binder, which is also the one put in the binding site.
201 * The in-scope "set" usually maps x->x; we use it simply for its domain.
202 But sometimes we have two in-scope Ids that are synomyms, and should
203 map to the same target: x->x, y->x. Notably:
205 That's why the "set" is actually a VarEnv Var
209 mkSimplEnv :: SimplifierMode -> SwitchChecker -> SimplEnv
210 mkSimplEnv mode switches
211 = SimplEnv { seChkr = switches, seCC = subsumedCCS,
212 seMode = mode, seInScope = emptyInScopeSet,
213 seFloats = emptyFloats,
214 seTvSubst = emptyVarEnv, seIdSubst = emptyVarEnv }
215 -- The top level "enclosing CC" is "SUBSUMED".
217 ---------------------
218 getSwitchChecker :: SimplEnv -> SwitchChecker
219 getSwitchChecker env = seChkr env
221 ---------------------
222 getMode :: SimplEnv -> SimplifierMode
223 getMode env = seMode env
225 setMode :: SimplifierMode -> SimplEnv -> SimplEnv
226 setMode mode env = env { seMode = mode }
228 ---------------------
229 getEnclosingCC :: SimplEnv -> CostCentreStack
230 getEnclosingCC env = seCC env
232 setEnclosingCC :: SimplEnv -> CostCentreStack -> SimplEnv
233 setEnclosingCC env cc = env {seCC = cc}
235 ---------------------
236 extendIdSubst :: SimplEnv -> Id -> SimplSR -> SimplEnv
237 extendIdSubst env@(SimplEnv {seIdSubst = subst}) var res
238 = env {seIdSubst = extendVarEnv subst var res}
240 extendTvSubst :: SimplEnv -> TyVar -> Type -> SimplEnv
241 extendTvSubst env@(SimplEnv {seTvSubst = subst}) var res
242 = env {seTvSubst = extendVarEnv subst var res}
244 ---------------------
245 getInScope :: SimplEnv -> InScopeSet
246 getInScope env = seInScope env
248 setInScopeSet :: SimplEnv -> InScopeSet -> SimplEnv
249 setInScopeSet env in_scope = env {seInScope = in_scope}
251 setInScope :: SimplEnv -> SimplEnv -> SimplEnv
252 -- Set the in-scope set, and *zap* the floats
253 setInScope env env_with_scope
254 = env { seInScope = seInScope env_with_scope,
255 seFloats = emptyFloats }
257 setFloats :: SimplEnv -> SimplEnv -> SimplEnv
258 -- Set the in-scope set *and* the floats
259 setFloats env env_with_floats
260 = env { seInScope = seInScope env_with_floats,
261 seFloats = seFloats env_with_floats }
263 addNewInScopeIds :: SimplEnv -> [CoreBndr] -> SimplEnv
264 -- The new Ids are guaranteed to be freshly allocated
265 addNewInScopeIds env@(SimplEnv { seInScope = in_scope, seIdSubst = id_subst }) vs
266 = env { seInScope = in_scope `extendInScopeSetList` vs,
267 seIdSubst = id_subst `delVarEnvList` vs }
268 -- Why delete? Consider
269 -- let x = a*b in (x, \x -> x+3)
270 -- We add [x |-> a*b] to the substitution, but we must
271 -- *delete* it from the substitution when going inside
274 modifyInScope :: SimplEnv -> CoreBndr -> CoreBndr -> SimplEnv
275 modifyInScope env@(SimplEnv {seInScope = in_scope}) v v'
276 = env {seInScope = modifyInScopeSet in_scope v v'}
278 ---------------------
279 zapSubstEnv :: SimplEnv -> SimplEnv
280 zapSubstEnv env = env {seTvSubst = emptyVarEnv, seIdSubst = emptyVarEnv}
282 setSubstEnv :: SimplEnv -> TvSubstEnv -> SimplIdSubst -> SimplEnv
283 setSubstEnv env tvs ids = env { seTvSubst = tvs, seIdSubst = ids }
285 mkContEx :: SimplEnv -> InExpr -> SimplSR
286 mkContEx (SimplEnv { seTvSubst = tvs, seIdSubst = ids }) e = ContEx tvs ids e
288 isEmptySimplSubst :: SimplEnv -> Bool
289 isEmptySimplSubst (SimplEnv { seTvSubst = tvs, seIdSubst = ids })
290 = isEmptyVarEnv tvs && isEmptyVarEnv ids
295 %************************************************************************
299 %************************************************************************
301 Note [Simplifier floats]
302 ~~~~~~~~~~~~~~~~~~~~~~~~~
303 The Floats is a bunch of bindings, classified by a FloatFlag.
305 NonRec x (y:ys) FltLifted
306 Rec [(x,rhs)] FltLifted
308 NonRec x# (y +# 3) FltOkSpec -- Unboxed, but ok-for-spec'n
310 NonRec x# (a /# b) FltCareful
311 NonRec x* (f y) FltCareful -- Strict binding; might fail or diverge
312 NonRec x# (f y) FltCareful -- Unboxed binding: might fail or diverge
313 -- (where f :: Int -> Int#)
316 data Floats = Floats (OrdList OutBind) FloatFlag
317 -- See Note [Simplifier floats]
320 = FltLifted -- All bindings are lifted and lazy
321 -- Hence ok to float to top level, or recursive
323 | FltOkSpec -- All bindings are FltLifted *or*
324 -- strict (perhaps because unlifted,
325 -- perhaps because of a strict binder),
326 -- *and* ok-for-speculation
327 -- Hence ok to float out of the RHS
328 -- of a lazy non-recursive let binding
329 -- (but not to top level, or into a rec group)
331 | FltCareful -- At least one binding is strict (or unlifted)
332 -- and not guaranteed cheap
333 -- Do not float these bindings out of a lazy let
335 instance Outputable Floats where
336 ppr (Floats binds ff) = ppr ff $$ ppr (fromOL binds)
338 instance Outputable FloatFlag where
339 ppr FltLifted = ptext (sLit "FltLifted")
340 ppr FltOkSpec = ptext (sLit "FltOkSpec")
341 ppr FltCareful = ptext (sLit "FltCareful")
343 andFF :: FloatFlag -> FloatFlag -> FloatFlag
344 andFF FltCareful _ = FltCareful
345 andFF FltOkSpec FltCareful = FltCareful
346 andFF FltOkSpec _ = FltOkSpec
347 andFF FltLifted flt = flt
349 classifyFF :: CoreBind -> FloatFlag
350 classifyFF (Rec _) = FltLifted
351 classifyFF (NonRec bndr rhs)
352 | not (isStrictId bndr) = FltLifted
353 | exprOkForSpeculation rhs = FltOkSpec
354 | otherwise = FltCareful
356 doFloatFromRhs :: TopLevelFlag -> RecFlag -> Bool -> OutExpr -> SimplEnv -> Bool
357 doFloatFromRhs lvl rec str rhs (SimplEnv {seFloats = Floats fs ff})
358 = not (isNilOL fs) && want_to_float && can_float
360 want_to_float = isTopLevel lvl || exprIsCheap rhs
361 can_float = case ff of
363 FltOkSpec -> isNotTopLevel lvl && isNonRec rec
364 FltCareful -> isNotTopLevel lvl && isNonRec rec && str
369 emptyFloats :: Floats
370 emptyFloats = Floats nilOL FltLifted
372 unitFloat :: OutBind -> Floats
373 -- A single-binding float
374 unitFloat bind = Floats (unitOL bind) (classifyFF bind)
376 addNonRec :: SimplEnv -> OutId -> OutExpr -> SimplEnv
377 -- Add a non-recursive binding and extend the in-scope set
378 -- The latter is important; the binder may already be in the
379 -- in-scope set (although it might also have been created with newId)
380 -- but it may now have more IdInfo
382 = env { seFloats = seFloats env `addFlts` unitFloat (NonRec id rhs),
383 seInScope = extendInScopeSet (seInScope env) id }
385 extendFloats :: SimplEnv -> OutBind -> SimplEnv
386 -- Add these bindings to the floats, and extend the in-scope env too
387 extendFloats env bind
388 = env { seFloats = seFloats env `addFlts` unitFloat bind,
389 seInScope = extendInScopeSetList (seInScope env) bndrs }
391 bndrs = bindersOf bind
393 addFloats :: SimplEnv -> SimplEnv -> SimplEnv
394 -- Add the floats for env2 to env1;
395 -- *plus* the in-scope set for env2, which is bigger
396 -- than that for env1
398 = env1 {seFloats = seFloats env1 `addFlts` seFloats env2,
399 seInScope = seInScope env2 }
401 addFlts :: Floats -> Floats -> Floats
402 addFlts (Floats bs1 l1) (Floats bs2 l2)
403 = Floats (bs1 `appOL` bs2) (l1 `andFF` l2)
405 zapFloats :: SimplEnv -> SimplEnv
406 zapFloats env = env { seFloats = emptyFloats }
408 addRecFloats :: SimplEnv -> SimplEnv -> SimplEnv
409 -- Flattens the floats from env2 into a single Rec group,
410 -- prepends the floats from env1, and puts the result back in env2
411 -- This is all very specific to the way recursive bindings are
412 -- handled; see Simplify.simplRecBind
413 addRecFloats env1 env2@(SimplEnv {seFloats = Floats bs ff})
414 = ASSERT2( case ff of { FltLifted -> True; _ -> False }, ppr (fromOL bs) )
415 env2 {seFloats = seFloats env1 `addFlts` unitFloat (Rec (flattenBinds (fromOL bs)))}
417 wrapFloats :: SimplEnv -> OutExpr -> OutExpr
418 wrapFloats env expr = wrapFlts (seFloats env) expr
420 wrapFlts :: Floats -> OutExpr -> OutExpr
421 -- Wrap the floats around the expression, using case-binding where necessary
422 wrapFlts (Floats bs _) body = foldrOL wrap body bs
424 wrap (Rec prs) body = Let (Rec prs) body
425 wrap (NonRec b r) body = bindNonRec b r body
427 getFloats :: SimplEnv -> [CoreBind]
428 getFloats (SimplEnv {seFloats = Floats bs _}) = fromOL bs
430 isEmptyFloats :: SimplEnv -> Bool
431 isEmptyFloats env = isEmptyFlts (seFloats env)
433 isEmptyFlts :: Floats -> Bool
434 isEmptyFlts (Floats bs _) = isNilOL bs
436 floatBinds :: Floats -> [OutBind]
437 floatBinds (Floats bs _) = fromOL bs
441 %************************************************************************
445 %************************************************************************
449 substId :: SimplEnv -> InId -> SimplSR
450 -- Returns DoneEx only on a non-Var expression
451 substId (SimplEnv { seInScope = in_scope, seIdSubst = ids }) v
454 | otherwise -- A local Id
455 = case lookupVarEnv ids v of
456 Nothing -> DoneId (refine in_scope v)
457 Just (DoneId v) -> DoneId (refine in_scope v)
458 Just (DoneEx (Var v))
459 | isLocalId v -> DoneId (refine in_scope v)
460 | otherwise -> DoneId v
461 Just res -> res -- DoneEx non-var, or ContEx
464 -- Get the most up-to-date thing from the in-scope set
465 -- Even though it isn't in the substitution, it may be in
466 -- the in-scope set with better IdInfo
467 refine :: InScopeSet -> Var -> Var
468 refine in_scope v = case lookupInScope in_scope v of
470 Nothing -> WARN( True, ppr v ) v -- This is an error!
472 lookupRecBndr :: SimplEnv -> InId -> OutId
473 -- Look up an Id which has been put into the envt by simplRecBndrs,
474 -- but where we have not yet done its RHS
475 lookupRecBndr (SimplEnv { seInScope = in_scope, seIdSubst = ids }) v
476 = case lookupVarEnv ids v of
478 Just _ -> pprPanic "lookupRecBndr" (ppr v)
479 Nothing -> refine in_scope v
483 %************************************************************************
485 \section{Substituting an Id binder}
487 %************************************************************************
490 These functions are in the monad only so that they can be made strict via seq.
493 simplBinders, simplLamBndrs
494 :: SimplEnv -> [InBndr] -> SimplM (SimplEnv, [OutBndr])
495 simplBinders env bndrs = mapAccumLM simplBinder env bndrs
496 simplLamBndrs env bndrs = mapAccumLM simplLamBndr env bndrs
499 simplBinder :: SimplEnv -> InBndr -> SimplM (SimplEnv, OutBndr)
500 -- Used for lambda and case-bound variables
501 -- Clone Id if necessary, substitute type
502 -- Return with IdInfo already substituted, but (fragile) occurrence info zapped
503 -- The substitution is extended only if the variable is cloned, because
504 -- we *don't* need to use it to track occurrence info.
506 | isTyVar bndr = do { let (env', tv) = substTyVarBndr env bndr
507 ; seqTyVar tv `seq` return (env', tv) }
508 | otherwise = do { let (env', id) = substIdBndr env bndr
509 ; seqId id `seq` return (env', id) }
512 simplLamBndr :: SimplEnv -> Var -> SimplM (SimplEnv, Var)
513 -- Used for lambda binders. These sometimes have unfoldings added by
514 -- the worker/wrapper pass that must be preserved, because they can't
515 -- be reconstructed from context. For example:
516 -- f x = case x of (a,b) -> fw a b x
517 -- fw a b x{=(a,b)} = ...
518 -- The "{=(a,b)}" is an unfolding we can't reconstruct otherwise.
519 simplLamBndr env bndr
520 | isId bndr && hasSomeUnfolding old_unf = seqId id2 `seq` return (env2, id2) -- Special case
521 | otherwise = simplBinder env bndr -- Normal case
523 old_unf = idUnfolding bndr
524 (env1, id1) = substIdBndr env bndr
525 id2 = id1 `setIdUnfolding` substUnfolding env old_unf
526 env2 = modifyInScope env1 id1 id2
529 simplNonRecBndr :: SimplEnv -> InBndr -> SimplM (SimplEnv, OutBndr)
530 -- A non-recursive let binder
531 simplNonRecBndr env id
532 = do { let (env1, id1) = substIdBndr env id
533 ; seqId id1 `seq` return (env1, id1) }
536 simplRecBndrs :: SimplEnv -> [InBndr] -> SimplM SimplEnv
537 -- Recursive let binders
538 simplRecBndrs env@(SimplEnv {}) ids
539 = do { let (env1, ids1) = mapAccumL substIdBndr env ids
540 ; seqIds ids1 `seq` return env1 }
543 substIdBndr :: SimplEnv
544 -> InBndr -- Env and binder to transform
545 -> (SimplEnv, OutBndr)
546 -- Clone Id if necessary, substitute its type
547 -- Return an Id with its
548 -- * Type substituted
549 -- * UnfoldingInfo, Rules, WorkerInfo zapped
550 -- * Fragile OccInfo (only) zapped: Note [Robust OccInfo]
551 -- * Robust info, retained especially arity and demand info,
552 -- so that they are available to occurrences that occur in an
553 -- earlier binding of a letrec
555 -- For the robust info, see Note [Arity robustness]
557 -- Augment the substitution if the unique changed
558 -- Extend the in-scope set with the new Id
560 -- Similar to CoreSubst.substIdBndr, except that
561 -- the type of id_subst differs
562 -- all fragile info is zapped
564 substIdBndr env@(SimplEnv { seInScope = in_scope, seIdSubst = id_subst })
566 = (env { seInScope = in_scope `extendInScopeSet` new_id,
567 seIdSubst = new_subst }, new_id)
569 id1 = uniqAway in_scope old_id
570 id2 = substIdType env id1
571 new_id = zapFragileIdInfo id2 -- Zaps rules, worker-info, unfolding
572 -- and fragile OccInfo
574 -- Extend the substitution if the unique has changed,
575 -- or there's some useful occurrence information
576 -- See the notes with substTyVarBndr for the delSubstEnv
577 new_subst | new_id /= old_id
578 = extendVarEnv id_subst old_id (DoneId new_id)
580 = delVarEnv id_subst old_id
584 ------------------------------------
585 seqTyVar :: TyVar -> ()
586 seqTyVar b = b `seq` ()
589 seqId id = seqType (idType id) `seq`
595 seqIds (id:ids) = seqId id `seq` seqIds ids
599 Note [Arity robustness]
600 ~~~~~~~~~~~~~~~~~~~~~~~
601 We *do* transfer the arity from from the in_id of a let binding to the
602 out_id. This is important, so that the arity of an Id is visible in
603 its own RHS. For example:
604 f = \x. ....g (\y. f y)....
605 We can eta-reduce the arg to g, becuase f is a value. But that
608 This interacts with the 'state hack' too:
613 Can we eta-expand f? Only if we see that f has arity 1, and then we
614 take advantage of the 'state hack' on the result of
615 (f y) :: State# -> (State#, Int) to expand the arity one more.
617 There is a disadvantage though. Making the arity visible in the RHS
618 allows us to eta-reduce
622 which technically is not sound. This is very much a corner case, so
623 I'm not worried about it. Another idea is to ensure that f's arity
624 never decreases; its arity started as 1, and we should never eta-reduce
628 Note [Robust OccInfo]
629 ~~~~~~~~~~~~~~~~~~~~~
630 It's important that we *do* retain the loop-breaker OccInfo, because
631 that's what stops the Id getting inlined infinitely, in the body of
635 Note [Rules in a letrec]
636 ~~~~~~~~~~~~~~~~~~~~~~~~
637 After creating fresh binders for the binders of a letrec, we
638 substitute the RULES and add them back onto the binders; this is done
639 *before* processing any of the RHSs. This is important. Manuel found
640 cases where he really, really wanted a RULE for a recursive function
641 to apply in that function's own right-hand side.
643 See Note [Loop breaking and RULES] in OccAnal.
647 addBndrRules :: SimplEnv -> InBndr -> OutBndr -> (SimplEnv, OutBndr)
648 -- Rules are added back in to to the bin
649 addBndrRules env in_id out_id
650 | isEmptySpecInfo old_rules = (env, out_id)
651 | otherwise = (modifyInScope env out_id final_id, final_id)
653 subst = mkCoreSubst env
654 old_rules = idSpecialisation in_id
655 new_rules = CoreSubst.substSpec subst out_id old_rules
656 final_id = out_id `setIdSpecialisation` new_rules
659 substIdType :: SimplEnv -> Id -> Id
660 substIdType (SimplEnv { seInScope = in_scope, seTvSubst = tv_env}) id
661 | isEmptyVarEnv tv_env || isEmptyVarSet (tyVarsOfType old_ty) = id
662 | otherwise = Id.setIdType id (Type.substTy (TvSubst in_scope tv_env) old_ty)
663 -- The tyVarsOfType is cheaper than it looks
664 -- because we cache the free tyvars of the type
665 -- in a Note in the id's type itself
670 substUnfolding :: SimplEnv -> Unfolding -> Unfolding
671 substUnfolding _ NoUnfolding = NoUnfolding
672 substUnfolding _ (OtherCon cons) = OtherCon cons
673 substUnfolding env (CompulsoryUnfolding rhs) = CompulsoryUnfolding (substExpr env rhs)
674 substUnfolding env (CoreUnfolding rhs t v w g) = CoreUnfolding (substExpr env rhs) t v w g
677 substWorker :: SimplEnv -> WorkerInfo -> WorkerInfo
678 substWorker _ NoWorker = NoWorker
679 substWorker env wkr_info = CoreSubst.substWorker (mkCoreSubst env) wkr_info
683 %************************************************************************
685 Impedence matching to type substitution
687 %************************************************************************
690 substTy :: SimplEnv -> Type -> Type
691 substTy (SimplEnv { seInScope = in_scope, seTvSubst = tv_env }) ty
692 = Type.substTy (TvSubst in_scope tv_env) ty
694 substTyVarBndr :: SimplEnv -> TyVar -> (SimplEnv, TyVar)
695 substTyVarBndr env@(SimplEnv { seInScope = in_scope, seTvSubst = tv_env }) tv
696 = case Type.substTyVarBndr (TvSubst in_scope tv_env) tv of
697 (TvSubst in_scope' tv_env', tv')
698 -> (env { seInScope = in_scope', seTvSubst = tv_env'}, tv')
700 -- When substituting in rules etc we can get CoreSubst to do the work
701 -- But CoreSubst uses a simpler form of IdSubstEnv, so we must impedence-match
702 -- here. I think the this will not usually result in a lot of work;
703 -- the substitutions are typically small, and laziness will avoid work in many cases.
705 mkCoreSubst :: SimplEnv -> CoreSubst.Subst
706 mkCoreSubst (SimplEnv { seInScope = in_scope, seTvSubst = tv_env, seIdSubst = id_env })
707 = mk_subst tv_env id_env
709 mk_subst tv_env id_env = CoreSubst.mkSubst in_scope tv_env (mapVarEnv fiddle id_env)
711 fiddle (DoneEx e) = e
712 fiddle (DoneId v) = Var v
713 fiddle (ContEx tv id e) = CoreSubst.substExpr (mk_subst tv id) e
715 substExpr :: SimplEnv -> CoreExpr -> CoreExpr
717 | isEmptySimplSubst env = expr
718 | otherwise = CoreSubst.substExpr (mkCoreSubst env) expr