2 % (c) The AQUA Project, Glasgow University, 1993-1998
4 \section[SimplMonad]{The simplifier Monad}
8 InId, InBind, InExpr, InAlt, InArg, InType, InBinder,
9 OutId, OutBind, OutExpr, OutAlt, OutArg, OutType, OutBinder,
10 OutExprStuff, OutStuff,
12 -- The continuation type
13 SimplCont(..), DupFlag(..), contIsDupable, contResultType,
14 contIsInteresting, pushArgs, discardCont, countValArgs, countArgs,
15 contIsInline, discardInlineCont,
19 initSmpl, returnSmpl, thenSmpl, thenSmpl_,
20 mapSmpl, mapAndUnzipSmpl, mapAccumLSmpl,
22 -- The inlining black-list
26 getUniqueSmpl, getUniquesSmpl,
32 getSimplCount, zeroSimplCount, pprSimplCount,
33 plusSimplCount, isZeroSimplCount,
36 SwitchChecker, getSwitchChecker, getSimplIntSwitch,
39 getEnclosingCC, setEnclosingCC,
43 getSubstEnv, extendSubst, extendSubstList,
44 getInScope, setInScope, extendInScope, extendInScopes, modifyInScope,
45 setSubstEnv, zapSubstEnv,
46 getSimplBinderStuff, setSimplBinderStuff,
50 #include "HsVersions.h"
52 import Const ( Con(DEFAULT) )
53 import Id ( Id, mkSysLocal, idMustBeINLINEd )
54 import IdInfo ( InlinePragInfo(..) )
55 import Demand ( Demand )
57 import PprCore () -- Instances
58 import Rules ( RuleBase )
59 import CostCentre ( CostCentreStack, subsumedCCS )
63 import qualified Subst
64 import Subst ( Subst, emptySubst, mkSubst,
66 InScopeSet, substInScope, isInScope, lookupInScope
68 import Type ( Type, TyVarSubst, applyTy )
69 import UniqSupply ( uniqsFromSupply, uniqFromSupply, splitUniqSupply,
73 import CmdLineOpts ( SimplifierSwitch(..), SwitchResult(..),
74 opt_PprStyle_Debug, opt_HistorySize,
77 import Unique ( Unique )
78 import Maybes ( expectJust )
79 import Util ( zipWithEqual )
82 infixr 9 `thenSmpl`, `thenSmpl_`
85 %************************************************************************
87 \subsection[Simplify-types]{Type declarations}
89 %************************************************************************
92 type InBinder = CoreBndr
93 type InId = Id -- Not yet cloned
94 type InType = Type -- Ditto
95 type InBind = CoreBind
96 type InExpr = CoreExpr
100 type OutBinder = CoreBndr
101 type OutId = Id -- Cloned
102 type OutType = Type -- Cloned
103 type OutBind = CoreBind
104 type OutExpr = CoreExpr
105 type OutAlt = CoreAlt
106 type OutArg = CoreArg
108 type SwitchChecker = SimplifierSwitch -> SwitchResult
112 %************************************************************************
114 \subsection{The continuation data type}
116 %************************************************************************
119 type OutExprStuff = OutStuff (InScopeSet, OutExpr)
120 type OutStuff a = ([OutBind], a)
121 -- We return something equivalent to (let b in e), but
122 -- in pieces to avoid the quadratic blowup when floating
123 -- incrementally. Comments just before simplExprB in Simplify.lhs
125 data SimplCont -- Strict contexts
126 = Stop OutType -- Type of the result
128 | CoerceIt OutType -- The To-type, simplified
131 | InlinePlease -- This continuation makes a function very
132 SimplCont -- keen to inline itelf
135 InExpr SubstEnv -- The argument, as yet unsimplified,
136 SimplCont -- and its subst-env
139 InId [InAlt] SubstEnv -- The case binder, alts, and subst-env
142 | ArgOf DupFlag -- An arbitrary strict context: the argument
143 -- of a strict function, or a primitive-arg fn
145 OutType -- The type of the expression being sought by the context
146 -- f (error "foo") ==> coerce t (error "foo")
148 -- We need to know the type t, to which to coerce.
149 (OutExpr -> SimplM OutExprStuff) -- What to do with the result
151 instance Outputable SimplCont where
152 ppr (Stop _) = ptext SLIT("Stop")
153 ppr (ApplyTo dup arg se cont) = (ptext SLIT("ApplyTo") <+> ppr dup <+> ppr arg) $$ ppr cont
154 ppr (ArgOf dup _ _) = ptext SLIT("ArgOf...") <+> ppr dup
155 ppr (Select dup bndr alts se cont) = (ptext SLIT("Select") <+> ppr dup <+> ppr bndr) $$
156 (nest 4 (ppr alts)) $$ ppr cont
157 ppr (CoerceIt ty cont) = (ptext SLIT("CoerceIt") <+> ppr ty) $$ ppr cont
158 ppr (InlinePlease cont) = ptext SLIT("InlinePlease") $$ ppr cont
160 data DupFlag = OkToDup | NoDup
162 instance Outputable DupFlag where
163 ppr OkToDup = ptext SLIT("ok")
164 ppr NoDup = ptext SLIT("nodup")
166 contIsDupable :: SimplCont -> Bool
167 contIsDupable (Stop _) = True
168 contIsDupable (ApplyTo OkToDup _ _ _) = True
169 contIsDupable (ArgOf OkToDup _ _) = True
170 contIsDupable (Select OkToDup _ _ _ _) = True
171 contIsDupable (CoerceIt _ cont) = contIsDupable cont
172 contIsDupable (InlinePlease cont) = contIsDupable cont
173 contIsDupable other = False
175 contIsInline :: SimplCont -> Bool
176 contIsInline (InlinePlease cont) = True
177 contIsInline other = False
179 discardInlineCont :: SimplCont -> SimplCont
180 discardInlineCont (InlinePlease cont) = cont
181 discardInlineCont cont = cont
185 Comment about contIsInteresting
186 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
187 We want to avoid inlining an expression where there can't possibly be
188 any gain, such as in an argument position. Hence, if the continuation
189 is interesting (eg. a case scrutinee, application etc.) then we
190 inline, otherwise we don't.
192 Previously some_benefit used to return True only if the variable was
193 applied to some value arguments. This didn't work:
195 let x = _coerce_ (T Int) Int (I# 3) in
196 case _coerce_ Int (T Int) x of
199 we want to inline x, but can't see that it's a constructor in a case
200 scrutinee position, and some_benefit is False.
204 dMonadST = _/\_ t -> :Monad (g1 _@_ t, g2 _@_ t, g3 _@_ t)
206 .... case dMonadST _@_ x0 of (a,b,c) -> ....
208 we'd really like to inline dMonadST here, but we *don't* want to
209 inline if the case expression is just
211 case x of y { DEFAULT -> ... }
213 since we can just eliminate this case instead (x is in WHNF). Similar
214 applies when x is bound to a lambda expression. Hence
215 contIsInteresting looks for case expressions with just a single
219 contIsInteresting :: SimplCont -> Bool
220 contIsInteresting (Select _ _ alts _ _) = not (just_default alts)
221 contIsInteresting (CoerceIt _ cont) = contIsInteresting cont
222 contIsInteresting (ApplyTo _ (Type _) _ cont) = contIsInteresting cont
223 contIsInteresting (ApplyTo _ _ _ _) = True
225 contIsInteresting (ArgOf _ _ _) = False
226 -- If this call is the arg of a strict function, the context
227 -- is a bit interesting. If we inline here, we may get useful
228 -- evaluation information to avoid repeated evals: e.g.
230 -- Here the contIsInteresting makes the '*' keener to inline,
231 -- which in turn exposes a constructor which makes the '+' inline.
232 -- Assuming that +,* aren't small enough to inline regardless.
234 -- HOWEVER, I put this back to False when I discovered that strings
235 -- were getting inlined straight back into applications of 'error'
236 -- because the latter is strict.
238 -- f = \x -> ...(error s)...
240 contIsInteresting (InlinePlease _) = True
241 contIsInteresting other = False
243 just_default [(DEFAULT,_,_)] = True -- See notes below for why we look
244 just_default alts = False -- for this special case
249 pushArgs :: SubstEnv -> [InExpr] -> SimplCont -> SimplCont
250 pushArgs se [] cont = cont
251 pushArgs se (arg:args) cont = ApplyTo NoDup arg se (pushArgs se args cont)
253 discardCont :: SimplCont -- A continuation, expecting
254 -> SimplCont -- Replace the continuation with a suitable coerce
255 discardCont (Stop to_ty) = Stop to_ty
256 discardCont cont = CoerceIt to_ty (Stop to_ty)
258 to_ty = contResultType cont
260 contResultType :: SimplCont -> OutType
261 contResultType (Stop to_ty) = to_ty
262 contResultType (ArgOf _ to_ty _) = to_ty
263 contResultType (ApplyTo _ _ _ cont) = contResultType cont
264 contResultType (CoerceIt _ cont) = contResultType cont
265 contResultType (InlinePlease cont) = contResultType cont
266 contResultType (Select _ _ _ _ cont) = contResultType cont
268 countValArgs :: SimplCont -> Int
269 countValArgs (ApplyTo _ (Type ty) se cont) = countValArgs cont
270 countValArgs (ApplyTo _ val_arg se cont) = 1 + countValArgs cont
271 countValArgs other = 0
273 countArgs :: SimplCont -> Int
274 countArgs (ApplyTo _ arg se cont) = 1 + countArgs cont
279 %************************************************************************
281 \subsection{Monad plumbing}
283 %************************************************************************
285 For the simplifier monad, we want to {\em thread} a unique supply and a counter.
286 (Command-line switches move around through the explicitly-passed SimplEnv.)
289 type SimplM result -- We thread the unique supply because
290 = SimplEnv -- constantly splitting it is rather expensive
293 -> (result, UniqSupply, SimplCount)
297 seChkr :: SwitchChecker,
298 seCC :: CostCentreStack, -- The enclosing CCS (when profiling)
299 seBlackList :: Id -> Bool, -- True => don't inline this Id
300 seSubst :: Subst -- The current substitution
302 -- The range of the substitution is OutType and OutExpr resp
304 -- The substitution is idempotent
305 -- It *must* be applied; things in its domain simply aren't
306 -- bound in the result.
308 -- The substitution usually maps an Id to its clone,
309 -- but if the orig defn is a let-binding, and
310 -- the RHS of the let simplifies to an atom,
311 -- we just add the binding to the substitution and elide the let.
313 -- The in-scope part of Subst includes *all* in-scope TyVars and Ids
314 -- The elements of the set may have better IdInfo than the
315 -- occurrences of in-scope Ids, and (more important) they will
316 -- have a correctly-substituted type. So we use a lookup in this
317 -- set to replace occurrences
321 initSmpl :: SwitchChecker
322 -> UniqSupply -- No init count; set to 0
323 -> VarSet -- In scope (usually empty, but useful for nested calls)
324 -> (Id -> Bool) -- Black-list function
328 initSmpl chkr us in_scope black_list m
329 = case m (emptySimplEnv chkr in_scope black_list) us zeroSimplCount of
330 (result, _, count) -> (result, count)
333 {-# INLINE thenSmpl #-}
334 {-# INLINE thenSmpl_ #-}
335 {-# INLINE returnSmpl #-}
337 returnSmpl :: a -> SimplM a
338 returnSmpl e env us sc = (e, us, sc)
340 thenSmpl :: SimplM a -> (a -> SimplM b) -> SimplM b
341 thenSmpl_ :: SimplM a -> SimplM b -> SimplM b
343 thenSmpl m k env us0 sc0
344 = case (m env us0 sc0) of
345 (m_result, us1, sc1) -> k m_result env us1 sc1
347 thenSmpl_ m k env us0 sc0
348 = case (m env us0 sc0) of
349 (_, us1, sc1) -> k env us1 sc1
354 mapSmpl :: (a -> SimplM b) -> [a] -> SimplM [b]
355 mapAndUnzipSmpl :: (a -> SimplM (b, c)) -> [a] -> SimplM ([b],[c])
357 mapSmpl f [] = returnSmpl []
359 = f x `thenSmpl` \ x' ->
360 mapSmpl f xs `thenSmpl` \ xs' ->
363 mapAndUnzipSmpl f [] = returnSmpl ([],[])
364 mapAndUnzipSmpl f (x:xs)
365 = f x `thenSmpl` \ (r1, r2) ->
366 mapAndUnzipSmpl f xs `thenSmpl` \ (rs1, rs2) ->
367 returnSmpl (r1:rs1, r2:rs2)
369 mapAccumLSmpl f acc [] = returnSmpl (acc, [])
370 mapAccumLSmpl f acc (x:xs) = f acc x `thenSmpl` \ (acc', x') ->
371 mapAccumLSmpl f acc' xs `thenSmpl` \ (acc'', xs') ->
372 returnSmpl (acc'', x':xs')
376 %************************************************************************
378 \subsection{The unique supply}
380 %************************************************************************
383 getUniqueSmpl :: SimplM Unique
384 getUniqueSmpl env us sc = case splitUniqSupply us of
385 (us1, us2) -> (uniqFromSupply us1, us2, sc)
387 getUniquesSmpl :: Int -> SimplM [Unique]
388 getUniquesSmpl n env us sc = case splitUniqSupply us of
389 (us1, us2) -> (uniqsFromSupply n us1, us2, sc)
393 %************************************************************************
395 \subsection{Counting up what we've done}
397 %************************************************************************
400 getSimplCount :: SimplM SimplCount
401 getSimplCount env us sc = (sc, us, sc)
403 tick :: Tick -> SimplM ()
404 tick t env us sc = sc' `seq` ((), us, sc')
408 freeTick :: Tick -> SimplM ()
409 -- Record a tick, but don't add to the total tick count, which is
410 -- used to decide when nothing further has happened
411 freeTick t env us sc = sc' `seq` ((), us, sc')
413 sc' = doFreeTick t sc
417 verboseSimplStats = opt_PprStyle_Debug -- For now, anyway
419 -- Defined both with and without debugging
420 zeroSimplCount :: SimplCount
421 isZeroSimplCount :: SimplCount -> Bool
422 pprSimplCount :: SimplCount -> SDoc
423 doTick, doFreeTick :: Tick -> SimplCount -> SimplCount
424 plusSimplCount :: SimplCount -> SimplCount -> SimplCount
429 ----------------------------------------------------------
431 ----------------------------------------------------------
432 type SimplCount = Int
436 isZeroSimplCount n = n==0
438 doTick t n = n+1 -- Very basic when not debugging
439 doFreeTick t n = n -- Don't count leaf visits
441 pprSimplCount n = ptext SLIT("Total ticks:") <+> int n
443 plusSimplCount n m = n+m
446 ----------------------------------------------------------
448 ----------------------------------------------------------
450 data SimplCount = SimplCount {
451 ticks :: !Int, -- Total ticks
452 details :: !TickCounts, -- How many of each type
454 log1 :: [Tick], -- Last N events; <= opt_HistorySize
455 log2 :: [Tick] -- Last opt_HistorySize events before that
458 type TickCounts = FiniteMap Tick Int
460 zeroSimplCount = SimplCount {ticks = 0, details = emptyFM,
461 n_log = 0, log1 = [], log2 = []}
463 isZeroSimplCount sc = ticks sc == 0
465 doFreeTick tick sc@SimplCount { details = dts }
466 = dts' `seqFM` sc { details = dts' }
468 dts' = dts `addTick` tick
470 -- Gross hack to persuade GHC 3.03 to do this important seq
471 seqFM fm x | isEmptyFM fm = x
474 doTick tick sc@SimplCount { ticks = tks, details = dts, n_log = nl, log1 = l1, log2 = l2 }
475 | nl >= opt_HistorySize = sc1 { n_log = 1, log1 = [tick], log2 = l1 }
476 | otherwise = sc1 { n_log = nl+1, log1 = tick : l1 }
478 sc1 = sc { ticks = tks+1, details = dts `addTick` tick }
480 -- Don't use plusFM_C because that's lazy, and we want to
481 -- be pretty strict here!
482 addTick :: TickCounts -> Tick -> TickCounts
483 addTick fm tick = case lookupFM fm tick of
484 Nothing -> addToFM fm tick 1
485 Just n -> n1 `seq` addToFM fm tick n1
489 plusSimplCount sc1@(SimplCount { ticks = tks1, details = dts1 })
490 sc2@(SimplCount { ticks = tks2, details = dts2 })
491 = log_base { ticks = tks1 + tks2, details = plusFM_C (+) dts1 dts2 }
493 -- A hackish way of getting recent log info
494 log_base | null (log1 sc2) = sc1 -- Nothing at all in sc2
495 | null (log2 sc2) = sc2 { log2 = log1 sc1 }
499 pprSimplCount (SimplCount { ticks = tks, details = dts, log1 = l1, log2 = l2 })
500 = vcat [ptext SLIT("Total ticks: ") <+> int tks,
502 pprTickCounts (fmToList dts),
503 if verboseSimplStats then
505 ptext SLIT("Log (most recent first)"),
506 nest 4 (vcat (map ppr l1) $$ vcat (map ppr l2))]
510 pprTickCounts :: [(Tick,Int)] -> SDoc
511 pprTickCounts [] = empty
512 pprTickCounts ((tick1,n1):ticks)
513 = vcat [int tot_n <+> text (tickString tick1),
514 pprTCDetails real_these,
518 tick1_tag = tickToTag tick1
519 (these, others) = span same_tick ticks
520 real_these = (tick1,n1):these
521 same_tick (tick2,_) = tickToTag tick2 == tick1_tag
522 tot_n = sum [n | (_,n) <- real_these]
524 pprTCDetails ticks@((tick,_):_)
525 | verboseSimplStats || isRuleFired tick
526 = nest 4 (vcat [int n <+> pprTickCts tick | (tick,n) <- ticks])
532 %************************************************************************
536 %************************************************************************
540 = PreInlineUnconditionally Id
541 | PostInlineUnconditionally Id
544 | RuleFired FAST_STRING -- Rule name
546 | LetFloatFromLet Id -- Thing floated out
547 | EtaExpansion Id -- LHS binder
548 | EtaReduction Id -- Binder on outer lambda
549 | BetaReduction Id -- Lambda binder
552 | CaseOfCase Id -- Bndr on *inner* case
553 | KnownBranch Id -- Case binder
554 | CaseMerge Id -- Binder on outer case
555 | CaseElim Id -- Case binder
556 | CaseIdentity Id -- Case binder
557 | FillInCaseDefault Id -- Case binder
561 | SimplifierDone -- Ticked at each iteration of the simplifier
563 isRuleFired (RuleFired _) = True
564 isRuleFired other = False
566 instance Outputable Tick where
567 ppr tick = text (tickString tick) <+> pprTickCts tick
569 instance Eq Tick where
570 a == b = case a `cmpTick` b of { EQ -> True; other -> False }
572 instance Ord Tick where
575 tickToTag :: Tick -> Int
576 tickToTag (PreInlineUnconditionally _) = 0
577 tickToTag (PostInlineUnconditionally _) = 1
578 tickToTag (UnfoldingDone _) = 2
579 tickToTag (RuleFired _) = 3
580 tickToTag (LetFloatFromLet _) = 4
581 tickToTag (EtaExpansion _) = 5
582 tickToTag (EtaReduction _) = 6
583 tickToTag (BetaReduction _) = 7
584 tickToTag (CaseOfCase _) = 8
585 tickToTag (KnownBranch _) = 9
586 tickToTag (CaseMerge _) = 10
587 tickToTag (CaseElim _) = 11
588 tickToTag (CaseIdentity _) = 12
589 tickToTag (FillInCaseDefault _) = 13
590 tickToTag BottomFound = 14
591 tickToTag LeafVisit = 15
592 tickToTag SimplifierDone = 16
594 tickString :: Tick -> String
595 tickString (PreInlineUnconditionally _) = "PreInlineUnconditionally"
596 tickString (PostInlineUnconditionally _)= "PostInlineUnconditionally"
597 tickString (UnfoldingDone _) = "UnfoldingDone"
598 tickString (RuleFired _) = "RuleFired"
599 tickString (LetFloatFromLet _) = "LetFloatFromLet"
600 tickString (EtaExpansion _) = "EtaExpansion"
601 tickString (EtaReduction _) = "EtaReduction"
602 tickString (BetaReduction _) = "BetaReduction"
603 tickString (CaseOfCase _) = "CaseOfCase"
604 tickString (KnownBranch _) = "KnownBranch"
605 tickString (CaseMerge _) = "CaseMerge"
606 tickString (CaseElim _) = "CaseElim"
607 tickString (CaseIdentity _) = "CaseIdentity"
608 tickString (FillInCaseDefault _) = "FillInCaseDefault"
609 tickString BottomFound = "BottomFound"
610 tickString SimplifierDone = "SimplifierDone"
611 tickString LeafVisit = "LeafVisit"
613 pprTickCts :: Tick -> SDoc
614 pprTickCts (PreInlineUnconditionally v) = ppr v
615 pprTickCts (PostInlineUnconditionally v)= ppr v
616 pprTickCts (UnfoldingDone v) = ppr v
617 pprTickCts (RuleFired v) = ppr v
618 pprTickCts (LetFloatFromLet v) = ppr v
619 pprTickCts (EtaExpansion v) = ppr v
620 pprTickCts (EtaReduction v) = ppr v
621 pprTickCts (BetaReduction v) = ppr v
622 pprTickCts (CaseOfCase v) = ppr v
623 pprTickCts (KnownBranch v) = ppr v
624 pprTickCts (CaseMerge v) = ppr v
625 pprTickCts (CaseElim v) = ppr v
626 pprTickCts (CaseIdentity v) = ppr v
627 pprTickCts (FillInCaseDefault v) = ppr v
628 pprTickCts other = empty
630 cmpTick :: Tick -> Tick -> Ordering
631 cmpTick a b = case (tickToTag a `compare` tickToTag b) of
633 EQ | isRuleFired a || verboseSimplStats -> cmpEqTick a b
636 -- Always distinguish RuleFired, so that the stats
637 -- can report them even in non-verbose mode
639 cmpEqTick :: Tick -> Tick -> Ordering
640 cmpEqTick (PreInlineUnconditionally a) (PreInlineUnconditionally b) = a `compare` b
641 cmpEqTick (PostInlineUnconditionally a) (PostInlineUnconditionally b) = a `compare` b
642 cmpEqTick (UnfoldingDone a) (UnfoldingDone b) = a `compare` b
643 cmpEqTick (RuleFired a) (RuleFired b) = a `compare` b
644 cmpEqTick (LetFloatFromLet a) (LetFloatFromLet b) = a `compare` b
645 cmpEqTick (EtaExpansion a) (EtaExpansion b) = a `compare` b
646 cmpEqTick (EtaReduction a) (EtaReduction b) = a `compare` b
647 cmpEqTick (BetaReduction a) (BetaReduction b) = a `compare` b
648 cmpEqTick (CaseOfCase a) (CaseOfCase b) = a `compare` b
649 cmpEqTick (KnownBranch a) (KnownBranch b) = a `compare` b
650 cmpEqTick (CaseMerge a) (CaseMerge b) = a `compare` b
651 cmpEqTick (CaseElim a) (CaseElim b) = a `compare` b
652 cmpEqTick (CaseIdentity a) (CaseIdentity b) = a `compare` b
653 cmpEqTick (FillInCaseDefault a) (FillInCaseDefault b) = a `compare` b
654 cmpEqTick other1 other2 = EQ
658 %************************************************************************
660 \subsubsection{Command-line switches}
662 %************************************************************************
665 getSwitchChecker :: SimplM SwitchChecker
666 getSwitchChecker env us sc = (seChkr env, us, sc)
668 getSimplIntSwitch :: SwitchChecker -> (Int-> SimplifierSwitch) -> Int
669 getSimplIntSwitch chkr switch
670 = expectJust "getSimplIntSwitch" (intSwitchSet chkr switch)
674 @switchOffInlining@ is used to prepare the environment for simplifying
675 the RHS of an Id that's marked with an INLINE pragma. It is going to
676 be inlined wherever they are used, and then all the inlining will take
677 effect. Meanwhile, there isn't much point in doing anything to the
678 as-yet-un-INLINEd rhs. Furthremore, it's very important to switch off
680 (a) not doing so will inline a worker straight back into its wrapper!
682 and (b) Consider the following example
687 in ...g...g...g...g...g...
689 Now, if that's the ONLY occurrence of f, it will be inlined inside g,
690 and thence copied multiple times when g is inlined.
692 Andy disagrees! Example:
693 all xs = foldr (&&) True xs
694 any p = all . map p {-# INLINE any #-}
696 Problem: any won't get deforested, and so if it's exported and
697 the importer doesn't use the inlining, (eg passes it as an arg)
698 then we won't get deforestation at all.
699 We havn't solved this problem yet!
701 We prepare the envt by simply modifying the in_scope_env, which has all the
702 unfolding info. At one point we did it by modifying the chkr so that
703 it said "EssentialUnfoldingsOnly", but that prevented legitmate, and
704 important, simplifications happening in the body of the RHS.
708 We *don't* prevent inlining from happening for identifiers
709 that are marked as IMustBeINLINEd. An example of where
710 doing this is crucial is:
712 class Bar a => Foo a where
718 If `f' needs to peer inside Foo's superclass, Bar, it refers
719 to the appropriate super class selector, which is marked as
720 must-inlineable. We don't generate any code for a superclass
721 selector, so failing to inline it in the RHS of `f' will
722 leave a reference to a non-existent id, with bad consequences.
724 ALSO NOTE that we do all this by modifing the inline-pragma,
725 not by zapping the unfolding. The latter may still be useful for
726 knowing when something is evaluated.
728 June 98 update: I've gone back to dealing with this by adding
729 the EssentialUnfoldingsOnly switch. That doesn't stop essential
730 unfoldings, nor inlineUnconditionally stuff; and the thing's going
731 to be inlined at every call site anyway. Running over the whole
732 environment seems like wild overkill.
735 switchOffInlining :: SimplM a -> SimplM a
736 switchOffInlining m env us sc
737 = m (env { seBlackList = \v -> True }) us sc
741 %************************************************************************
743 \subsubsection{The ``enclosing cost-centre''}
745 %************************************************************************
748 getEnclosingCC :: SimplM CostCentreStack
749 getEnclosingCC env us sc = (seCC env, us, sc)
751 setEnclosingCC :: CostCentreStack -> SimplM a -> SimplM a
752 setEnclosingCC cc m env us sc = m (env { seCC = cc }) us sc
756 %************************************************************************
758 \subsubsection{The @SimplEnv@ type}
760 %************************************************************************
764 emptySimplEnv :: SwitchChecker -> InScopeSet -> (Id -> Bool) -> SimplEnv
766 emptySimplEnv sw_chkr in_scope black_list
767 = SimplEnv { seChkr = sw_chkr, seCC = subsumedCCS,
768 seBlackList = black_list,
769 seSubst = mkSubst in_scope emptySubstEnv }
770 -- The top level "enclosing CC" is "SUBSUMED".
772 getSubst :: SimplM Subst
773 getSubst env us sc = (seSubst env, us, sc)
775 getBlackList :: SimplM (Id -> Bool)
776 getBlackList env us sc = (seBlackList env, us, sc)
778 setSubst :: Subst -> SimplM a -> SimplM a
779 setSubst subst m env us sc = m (env {seSubst = subst}) us sc
781 getSubstEnv :: SimplM SubstEnv
782 getSubstEnv env us sc = (substEnv (seSubst env), us, sc)
784 extendInScope :: CoreBndr -> SimplM a -> SimplM a
785 extendInScope v m env@(SimplEnv {seSubst = subst}) us sc
786 = m (env {seSubst = Subst.extendInScope subst v}) us sc
788 extendInScopes :: [CoreBndr] -> SimplM a -> SimplM a
789 extendInScopes vs m env@(SimplEnv {seSubst = subst}) us sc
790 = m (env {seSubst = Subst.extendInScopes subst vs}) us sc
792 getInScope :: SimplM InScopeSet
793 getInScope env us sc = (substInScope (seSubst env), us, sc)
795 setInScope :: InScopeSet -> SimplM a -> SimplM a
796 setInScope in_scope m env@(SimplEnv {seSubst = subst}) us sc
797 = m (env {seSubst = Subst.setInScope subst in_scope}) us sc
799 modifyInScope :: CoreBndr -> SimplM a -> SimplM a
800 modifyInScope v m env us sc
802 | not (v `isInScope` seSubst env)
803 = pprTrace "modifyInScope: not in scope:" (ppr v)
807 = extendInScope v m env us sc
809 extendSubst :: CoreBndr -> SubstResult -> SimplM a -> SimplM a
810 extendSubst var res m env@(SimplEnv {seSubst = subst}) us sc
811 = m (env { seSubst = Subst.extendSubst subst var res }) us sc
813 extendSubstList :: [CoreBndr] -> [SubstResult] -> SimplM a -> SimplM a
814 extendSubstList vars ress m env@(SimplEnv {seSubst = subst}) us sc
815 = m (env { seSubst = Subst.extendSubstList subst vars ress }) us sc
817 setSubstEnv :: SubstEnv -> SimplM a -> SimplM a
818 setSubstEnv senv m env@(SimplEnv {seSubst = subst}) us sc
819 = m (env {seSubst = Subst.setSubstEnv subst senv}) us sc
821 zapSubstEnv :: SimplM a -> SimplM a
822 zapSubstEnv m env@(SimplEnv {seSubst = subst}) us sc
823 = m (env {seSubst = Subst.zapSubstEnv subst}) us sc
825 getSimplBinderStuff :: SimplM (Subst, UniqSupply)
826 getSimplBinderStuff (SimplEnv {seSubst = subst}) us sc
827 = ((subst, us), us, sc)
829 setSimplBinderStuff :: (Subst, UniqSupply) -> SimplM a -> SimplM a
830 setSimplBinderStuff (subst, us) m env _ sc
831 = m (env {seSubst = subst}) us sc
836 newId :: Type -> (Id -> SimplM a) -> SimplM a
837 -- Extends the in-scope-env too
838 newId ty m env@(SimplEnv {seSubst = subst}) us sc
839 = case splitUniqSupply us of
840 (us1, us2) -> m v (env {seSubst = Subst.extendInScope subst v}) us2 sc
842 v = mkSysLocal SLIT("s") (uniqFromSupply us1) ty
844 newIds :: [Type] -> ([Id] -> SimplM a) -> SimplM a
845 newIds tys m env@(SimplEnv {seSubst = subst}) us sc
846 = case splitUniqSupply us of
847 (us1, us2) -> m vs (env {seSubst = Subst.extendInScopes subst vs}) us2 sc
849 vs = zipWithEqual "newIds" (mkSysLocal SLIT("s"))
850 (uniqsFromSupply (length tys) us1) tys