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,
26 getSimplRules, inGentleMode,
28 SimplSR(..), mkContEx, substId, lookupRecBndr,
30 simplNonRecBndr, simplRecBndrs, simplLamBndr, simplLamBndrs,
31 simplBinder, simplBinders, addBndrRules,
32 substExpr, substTy, mkCoreSubst,
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, substUnfolding )
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 inGentleMode :: SimplEnv -> Bool
229 inGentleMode env = case seMode env of
233 ---------------------
234 getEnclosingCC :: SimplEnv -> CostCentreStack
235 getEnclosingCC env = seCC env
237 setEnclosingCC :: SimplEnv -> CostCentreStack -> SimplEnv
238 setEnclosingCC env cc = env {seCC = cc}
240 ---------------------
241 extendIdSubst :: SimplEnv -> Id -> SimplSR -> SimplEnv
242 extendIdSubst env@(SimplEnv {seIdSubst = subst}) var res
243 = env {seIdSubst = extendVarEnv subst var res}
245 extendTvSubst :: SimplEnv -> TyVar -> Type -> SimplEnv
246 extendTvSubst env@(SimplEnv {seTvSubst = subst}) var res
247 = env {seTvSubst = extendVarEnv subst var res}
249 ---------------------
250 getInScope :: SimplEnv -> InScopeSet
251 getInScope env = seInScope env
253 setInScopeSet :: SimplEnv -> InScopeSet -> SimplEnv
254 setInScopeSet env in_scope = env {seInScope = in_scope}
256 setInScope :: SimplEnv -> SimplEnv -> SimplEnv
257 -- Set the in-scope set, and *zap* the floats
258 setInScope env env_with_scope
259 = env { seInScope = seInScope env_with_scope,
260 seFloats = emptyFloats }
262 setFloats :: SimplEnv -> SimplEnv -> SimplEnv
263 -- Set the in-scope set *and* the floats
264 setFloats env env_with_floats
265 = env { seInScope = seInScope env_with_floats,
266 seFloats = seFloats env_with_floats }
268 addNewInScopeIds :: SimplEnv -> [CoreBndr] -> SimplEnv
269 -- The new Ids are guaranteed to be freshly allocated
270 addNewInScopeIds env@(SimplEnv { seInScope = in_scope, seIdSubst = id_subst }) vs
271 = env { seInScope = in_scope `extendInScopeSetList` vs,
272 seIdSubst = id_subst `delVarEnvList` vs }
273 -- Why delete? Consider
274 -- let x = a*b in (x, \x -> x+3)
275 -- We add [x |-> a*b] to the substitution, but we must
276 -- _delete_ it from the substitution when going inside
279 modifyInScope :: SimplEnv -> CoreBndr -> SimplEnv
280 -- The variable should already be in scope, but
281 -- replace the existing version with this new one
282 -- which has more information
283 modifyInScope env@(SimplEnv {seInScope = in_scope}) v
284 = env {seInScope = extendInScopeSet in_scope v}
286 ---------------------
287 zapSubstEnv :: SimplEnv -> SimplEnv
288 zapSubstEnv env = env {seTvSubst = emptyVarEnv, seIdSubst = emptyVarEnv}
290 setSubstEnv :: SimplEnv -> TvSubstEnv -> SimplIdSubst -> SimplEnv
291 setSubstEnv env tvs ids = env { seTvSubst = tvs, seIdSubst = ids }
293 mkContEx :: SimplEnv -> InExpr -> SimplSR
294 mkContEx (SimplEnv { seTvSubst = tvs, seIdSubst = ids }) e = ContEx tvs ids e
299 %************************************************************************
303 %************************************************************************
305 Note [Simplifier floats]
306 ~~~~~~~~~~~~~~~~~~~~~~~~~
307 The Floats is a bunch of bindings, classified by a FloatFlag.
309 NonRec x (y:ys) FltLifted
310 Rec [(x,rhs)] FltLifted
312 NonRec x# (y +# 3) FltOkSpec -- Unboxed, but ok-for-spec'n
314 NonRec x# (a /# b) FltCareful
315 NonRec x* (f y) FltCareful -- Strict binding; might fail or diverge
316 NonRec x# (f y) FltCareful -- Unboxed binding: might fail or diverge
317 -- (where f :: Int -> Int#)
320 data Floats = Floats (OrdList OutBind) FloatFlag
321 -- See Note [Simplifier floats]
324 = FltLifted -- All bindings are lifted and lazy
325 -- Hence ok to float to top level, or recursive
327 | FltOkSpec -- All bindings are FltLifted *or*
328 -- strict (perhaps because unlifted,
329 -- perhaps because of a strict binder),
330 -- *and* ok-for-speculation
331 -- Hence ok to float out of the RHS
332 -- of a lazy non-recursive let binding
333 -- (but not to top level, or into a rec group)
335 | FltCareful -- At least one binding is strict (or unlifted)
336 -- and not guaranteed cheap
337 -- Do not float these bindings out of a lazy let
339 instance Outputable Floats where
340 ppr (Floats binds ff) = ppr ff $$ ppr (fromOL binds)
342 instance Outputable FloatFlag where
343 ppr FltLifted = ptext (sLit "FltLifted")
344 ppr FltOkSpec = ptext (sLit "FltOkSpec")
345 ppr FltCareful = ptext (sLit "FltCareful")
347 andFF :: FloatFlag -> FloatFlag -> FloatFlag
348 andFF FltCareful _ = FltCareful
349 andFF FltOkSpec FltCareful = FltCareful
350 andFF FltOkSpec _ = FltOkSpec
351 andFF FltLifted flt = flt
353 classifyFF :: CoreBind -> FloatFlag
354 classifyFF (Rec _) = FltLifted
355 classifyFF (NonRec bndr rhs)
356 | not (isStrictId bndr) = FltLifted
357 | exprOkForSpeculation rhs = FltOkSpec
358 | otherwise = FltCareful
360 doFloatFromRhs :: TopLevelFlag -> RecFlag -> Bool -> OutExpr -> SimplEnv -> Bool
361 doFloatFromRhs lvl rec str rhs (SimplEnv {seFloats = Floats fs ff})
362 = not (isNilOL fs) && want_to_float && can_float
364 want_to_float = isTopLevel lvl || exprIsExpandable rhs
365 can_float = case ff of
367 FltOkSpec -> isNotTopLevel lvl && isNonRec rec
368 FltCareful -> isNotTopLevel lvl && isNonRec rec && str
373 emptyFloats :: Floats
374 emptyFloats = Floats nilOL FltLifted
376 unitFloat :: OutBind -> Floats
377 -- A single-binding float
378 unitFloat bind = Floats (unitOL bind) (classifyFF bind)
380 addNonRec :: SimplEnv -> OutId -> OutExpr -> SimplEnv
381 -- Add a non-recursive binding and extend the in-scope set
382 -- The latter is important; the binder may already be in the
383 -- in-scope set (although it might also have been created with newId)
384 -- but it may now have more IdInfo
386 = env { seFloats = seFloats env `addFlts` unitFloat (NonRec id rhs),
387 seInScope = extendInScopeSet (seInScope env) id }
389 extendFloats :: SimplEnv -> OutBind -> SimplEnv
390 -- Add these bindings to the floats, and extend the in-scope env too
391 extendFloats env bind
392 = env { seFloats = seFloats env `addFlts` unitFloat bind,
393 seInScope = extendInScopeSetList (seInScope env) bndrs }
395 bndrs = bindersOf bind
397 addFloats :: SimplEnv -> SimplEnv -> SimplEnv
398 -- Add the floats for env2 to env1;
399 -- *plus* the in-scope set for env2, which is bigger
400 -- than that for env1
402 = env1 {seFloats = seFloats env1 `addFlts` seFloats env2,
403 seInScope = seInScope env2 }
405 addFlts :: Floats -> Floats -> Floats
406 addFlts (Floats bs1 l1) (Floats bs2 l2)
407 = Floats (bs1 `appOL` bs2) (l1 `andFF` l2)
409 zapFloats :: SimplEnv -> SimplEnv
410 zapFloats env = env { seFloats = emptyFloats }
412 addRecFloats :: SimplEnv -> SimplEnv -> SimplEnv
413 -- Flattens the floats from env2 into a single Rec group,
414 -- prepends the floats from env1, and puts the result back in env2
415 -- This is all very specific to the way recursive bindings are
416 -- handled; see Simplify.simplRecBind
417 addRecFloats env1 env2@(SimplEnv {seFloats = Floats bs ff})
418 = ASSERT2( case ff of { FltLifted -> True; _ -> False }, ppr (fromOL bs) )
419 env2 {seFloats = seFloats env1 `addFlts` unitFloat (Rec (flattenBinds (fromOL bs)))}
421 wrapFloats :: SimplEnv -> OutExpr -> OutExpr
422 wrapFloats env expr = wrapFlts (seFloats env) expr
424 wrapFlts :: Floats -> OutExpr -> OutExpr
425 -- Wrap the floats around the expression, using case-binding where necessary
426 wrapFlts (Floats bs _) body = foldrOL wrap body bs
428 wrap (Rec prs) body = Let (Rec prs) body
429 wrap (NonRec b r) body = bindNonRec b r body
431 getFloats :: SimplEnv -> [CoreBind]
432 getFloats (SimplEnv {seFloats = Floats bs _}) = fromOL bs
434 isEmptyFloats :: SimplEnv -> Bool
435 isEmptyFloats env = isEmptyFlts (seFloats env)
437 isEmptyFlts :: Floats -> Bool
438 isEmptyFlts (Floats bs _) = isNilOL bs
440 floatBinds :: Floats -> [OutBind]
441 floatBinds (Floats bs _) = fromOL bs
445 %************************************************************************
449 %************************************************************************
451 Note [Global Ids in the substitution]
452 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
453 We look up even a global (eg imported) Id in the substitution. Consider
454 case X.g_34 of b { (a,b) -> ... case X.g_34 of { (p,q) -> ...} ... }
455 The binder-swap in the occurence analyser will add a binding
456 for a LocalId version of g (with the same unique though):
457 case X.g_34 of b { (a,b) -> let g_34 = b in
458 ... case X.g_34 of { (p,q) -> ...} ... }
459 So we want to look up the inner X.g_34 in the substitution, where we'll
460 find that it has been substituted by b. (Or conceivably cloned.)
463 substId :: SimplEnv -> InId -> SimplSR
464 -- Returns DoneEx only on a non-Var expression
465 substId (SimplEnv { seInScope = in_scope, seIdSubst = ids }) v
466 = case lookupVarEnv ids v of -- Note [Global Ids in the substitution]
467 Nothing -> DoneId (refine in_scope v)
468 Just (DoneId v) -> DoneId (refine in_scope v)
469 Just (DoneEx (Var v)) -> DoneId (refine in_scope v)
470 Just res -> res -- DoneEx non-var, or ContEx
473 -- Get the most up-to-date thing from the in-scope set
474 -- Even though it isn't in the substitution, it may be in
475 -- the in-scope set with better IdInfo
476 refine :: InScopeSet -> Var -> Var
478 | isLocalId v = case lookupInScope in_scope v of
480 Nothing -> WARN( True, ppr v ) v -- This is an error!
483 lookupRecBndr :: SimplEnv -> InId -> OutId
484 -- Look up an Id which has been put into the envt by simplRecBndrs,
485 -- but where we have not yet done its RHS
486 lookupRecBndr (SimplEnv { seInScope = in_scope, seIdSubst = ids }) v
487 = case lookupVarEnv ids v of
489 Just _ -> pprPanic "lookupRecBndr" (ppr v)
490 Nothing -> refine in_scope v
494 %************************************************************************
496 \section{Substituting an Id binder}
498 %************************************************************************
501 These functions are in the monad only so that they can be made strict via seq.
504 simplBinders, simplLamBndrs
505 :: SimplEnv -> [InBndr] -> SimplM (SimplEnv, [OutBndr])
506 simplBinders env bndrs = mapAccumLM simplBinder env bndrs
507 simplLamBndrs env bndrs = mapAccumLM simplLamBndr env bndrs
510 simplBinder :: SimplEnv -> InBndr -> SimplM (SimplEnv, OutBndr)
511 -- Used for lambda and case-bound variables
512 -- Clone Id if necessary, substitute type
513 -- Return with IdInfo already substituted, but (fragile) occurrence info zapped
514 -- The substitution is extended only if the variable is cloned, because
515 -- we *don't* need to use it to track occurrence info.
517 | isTyVar bndr = do { let (env', tv) = substTyVarBndr env bndr
518 ; seqTyVar tv `seq` return (env', tv) }
519 | otherwise = do { let (env', id) = substIdBndr env bndr
520 ; seqId id `seq` return (env', id) }
523 simplLamBndr :: SimplEnv -> Var -> SimplM (SimplEnv, Var)
524 -- Used for lambda binders. These sometimes have unfoldings added by
525 -- the worker/wrapper pass that must be preserved, because they can't
526 -- be reconstructed from context. For example:
527 -- f x = case x of (a,b) -> fw a b x
528 -- fw a b x{=(a,b)} = ...
529 -- The "{=(a,b)}" is an unfolding we can't reconstruct otherwise.
530 simplLamBndr env bndr
531 | isId bndr && hasSomeUnfolding old_unf = seqId id2 `seq` return (env2, id2) -- Special case
532 | otherwise = simplBinder env bndr -- Normal case
534 old_unf = idUnfolding bndr
535 (env1, id1) = substIdBndr env bndr
536 id2 = id1 `setIdUnfolding` substUnfolding env old_unf
537 env2 = modifyInScope env1 id2
540 simplNonRecBndr :: SimplEnv -> InBndr -> SimplM (SimplEnv, OutBndr)
541 -- A non-recursive let binder
542 simplNonRecBndr env id
543 = do { let (env1, id1) = substIdBndr env id
544 ; seqId id1 `seq` return (env1, id1) }
547 simplRecBndrs :: SimplEnv -> [InBndr] -> SimplM SimplEnv
548 -- Recursive let binders
549 simplRecBndrs env@(SimplEnv {}) ids
550 = do { let (env1, ids1) = mapAccumL substIdBndr env ids
551 ; seqIds ids1 `seq` return env1 }
554 substIdBndr :: SimplEnv
555 -> InBndr -- Env and binder to transform
556 -> (SimplEnv, OutBndr)
557 -- Clone Id if necessary, substitute its type
558 -- Return an Id with its
559 -- * Type substituted
560 -- * UnfoldingInfo, Rules, WorkerInfo zapped
561 -- * Fragile OccInfo (only) zapped: Note [Robust OccInfo]
562 -- * Robust info, retained especially arity and demand info,
563 -- so that they are available to occurrences that occur in an
564 -- earlier binding of a letrec
566 -- For the robust info, see Note [Arity robustness]
568 -- Augment the substitution if the unique changed
569 -- Extend the in-scope set with the new Id
571 -- Similar to CoreSubst.substIdBndr, except that
572 -- the type of id_subst differs
573 -- all fragile info is zapped
575 substIdBndr env@(SimplEnv { seInScope = in_scope, seIdSubst = id_subst })
577 = (env { seInScope = in_scope `extendInScopeSet` new_id,
578 seIdSubst = new_subst }, new_id)
580 id1 = uniqAway in_scope old_id
581 id2 = substIdType env id1
582 new_id = zapFragileIdInfo id2 -- Zaps rules, worker-info, unfolding
583 -- and fragile OccInfo
585 -- Extend the substitution if the unique has changed,
586 -- or there's some useful occurrence information
587 -- See the notes with substTyVarBndr for the delSubstEnv
588 new_subst | new_id /= old_id
589 = extendVarEnv id_subst old_id (DoneId new_id)
591 = delVarEnv id_subst old_id
595 ------------------------------------
596 seqTyVar :: TyVar -> ()
597 seqTyVar b = b `seq` ()
600 seqId id = seqType (idType id) `seq`
606 seqIds (id:ids) = seqId id `seq` seqIds ids
610 Note [Arity robustness]
611 ~~~~~~~~~~~~~~~~~~~~~~~
612 We *do* transfer the arity from from the in_id of a let binding to the
613 out_id. This is important, so that the arity of an Id is visible in
614 its own RHS. For example:
615 f = \x. ....g (\y. f y)....
616 We can eta-reduce the arg to g, becuase f is a value. But that
619 This interacts with the 'state hack' too:
624 Can we eta-expand f? Only if we see that f has arity 1, and then we
625 take advantage of the 'state hack' on the result of
626 (f y) :: State# -> (State#, Int) to expand the arity one more.
628 There is a disadvantage though. Making the arity visible in the RHS
629 allows us to eta-reduce
633 which technically is not sound. This is very much a corner case, so
634 I'm not worried about it. Another idea is to ensure that f's arity
635 never decreases; its arity started as 1, and we should never eta-reduce
639 Note [Robust OccInfo]
640 ~~~~~~~~~~~~~~~~~~~~~
641 It's important that we *do* retain the loop-breaker OccInfo, because
642 that's what stops the Id getting inlined infinitely, in the body of
646 Note [Rules in a letrec]
647 ~~~~~~~~~~~~~~~~~~~~~~~~
648 After creating fresh binders for the binders of a letrec, we
649 substitute the RULES and add them back onto the binders; this is done
650 *before* processing any of the RHSs. This is important. Manuel found
651 cases where he really, really wanted a RULE for a recursive function
652 to apply in that function's own right-hand side.
654 See Note [Loop breaking and RULES] in OccAnal.
658 addBndrRules :: SimplEnv -> InBndr -> OutBndr -> (SimplEnv, OutBndr)
659 -- Rules are added back in to to the bin
660 addBndrRules env in_id out_id
661 | isEmptySpecInfo old_rules = (env, out_id)
662 | otherwise = (modifyInScope env final_id, final_id)
664 subst = mkCoreSubst env
665 old_rules = idSpecialisation in_id
666 new_rules = CoreSubst.substSpec subst out_id old_rules
667 final_id = out_id `setIdSpecialisation` new_rules
671 %************************************************************************
673 Impedence matching to type substitution
675 %************************************************************************
678 substTy :: SimplEnv -> Type -> Type
679 substTy (SimplEnv { seInScope = in_scope, seTvSubst = tv_env }) ty
680 = Type.substTy (TvSubst in_scope tv_env) ty
682 substTyVarBndr :: SimplEnv -> TyVar -> (SimplEnv, TyVar)
683 substTyVarBndr env@(SimplEnv { seInScope = in_scope, seTvSubst = tv_env }) tv
684 = case Type.substTyVarBndr (TvSubst in_scope tv_env) tv of
685 (TvSubst in_scope' tv_env', tv')
686 -> (env { seInScope = in_scope', seTvSubst = tv_env'}, tv')
688 -- When substituting in rules etc we can get CoreSubst to do the work
689 -- But CoreSubst uses a simpler form of IdSubstEnv, so we must impedence-match
690 -- here. I think the this will not usually result in a lot of work;
691 -- the substitutions are typically small, and laziness will avoid work in many cases.
693 mkCoreSubst :: SimplEnv -> CoreSubst.Subst
694 mkCoreSubst (SimplEnv { seInScope = in_scope, seTvSubst = tv_env, seIdSubst = id_env })
695 = mk_subst tv_env id_env
697 mk_subst tv_env id_env = CoreSubst.mkSubst in_scope tv_env (mapVarEnv fiddle id_env)
699 fiddle (DoneEx e) = e
700 fiddle (DoneId v) = Var v
701 fiddle (ContEx tv id e) = CoreSubst.substExpr (mk_subst tv id) e
704 substIdType :: SimplEnv -> Id -> Id
705 substIdType (SimplEnv { seInScope = in_scope, seTvSubst = tv_env}) id
706 | isEmptyVarEnv tv_env || isEmptyVarSet (tyVarsOfType old_ty) = id
707 | otherwise = Id.setIdType id (Type.substTy (TvSubst in_scope tv_env) old_ty)
708 -- The tyVarsOfType is cheaper than it looks
709 -- because we cache the free tyvars of the type
710 -- in a Note in the id's type itself
715 substExpr :: SimplEnv -> CoreExpr -> CoreExpr
716 substExpr env expr = CoreSubst.substExpr (mkCoreSubst env) expr
717 -- Do *not* short-cut in the case of an empty substitution
718 -- See CoreSubst: Note [Extending the Subst]
720 substUnfolding :: SimplEnv -> Unfolding -> Unfolding
721 substUnfolding env unf = CoreSubst.substUnfolding (mkCoreSubst env) unf