2 % (c) The GRASP/AQUA Project, Glasgow University, 1993-1998
4 \section[StgVarInfo]{Sets free/live variable info in STG syntax}
6 And, as we have the info in hand, we may convert some lets to
10 module StgVarInfo ( setStgVarInfo ) where
12 #include "HsVersions.h"
16 import Id ( setIdArityInfo, idArity, setIdOccInfo, Id )
20 import IdInfo ( ArityInfo(..), OccInfo(..),
22 import PrimOp ( PrimOp(..), ccallMayGC )
23 import TysWiredIn ( isForeignObjTy )
24 import Maybes ( maybeToBool, orElse )
25 import Name ( isLocallyDefined, getOccName )
26 import OccName ( occNameUserString )
27 import BasicTypes ( Arity )
30 infixr 9 `thenLne`, `thenLne_`
33 %************************************************************************
35 \subsection[live-vs-free-doc]{Documentation}
37 %************************************************************************
39 (There is other relevant documentation in codeGen/CgLetNoEscape.)
41 March 97: setStgVarInfo guarantees to leave every variable's arity correctly
42 set. The lambda lifter makes some let-bound variables (which have arities)
43 and turns them into lambda-bound ones (which should not, else we get Vap trouble),
44 so this guarantee is necessary, as well as desirable.
46 The arity information is used in the code generator, when deciding if
47 a right-hand side is a saturated application so we can generate a VAP
50 The actual Stg datatype is decorated with {\em live variable}
51 information, as well as {\em free variable} information. The two are
52 {\em not} the same. Liveness is an operational property rather than a
53 semantic one. A variable is live at a particular execution point if
54 it can be referred to {\em directly} again. In particular, a dead
55 variable's stack slot (if it has one):
58 should be stubbed to avoid space leaks, and
60 may be reused for something else.
63 There ought to be a better way to say this. Here are some examples:
70 Just after the `in', v is live, but q is dead. If the whole of that
71 let expression was enclosed in a case expression, thus:
73 case (let v = [q] \[x] -> e in ...v...) of
76 (ie @alts@ mention @q@), then @q@ is live even after the `in'; because
77 we'll return later to the @alts@ and need it.
79 Let-no-escapes make this a bit more interesting:
81 let-no-escape v = [q] \ [x] -> e
85 Here, @q@ is still live at the `in', because @v@ is represented not by
86 a closure but by the current stack state. In other words, if @v@ is
87 live then so is @q@. Furthermore, if @e@ mentions an enclosing
88 let-no-escaped variable, then {\em its} free variables are also live
91 %************************************************************************
93 \subsection[binds-StgVarInfo]{Setting variable info: top-level, binds, RHSs}
95 %************************************************************************
99 setStgVarInfo :: Bool -- True <=> do let-no-escapes
100 -> [StgBinding] -- input
101 -> [StgBinding] -- result
103 setStgVarInfo want_LNEs pgm
106 (pgm', _) = initLne want_LNEs (varsTopBinds pgm)
110 For top-level guys, we basically aren't worried about this
111 live-variable stuff; we do need to keep adding to the environment
112 as we step through the bindings (using @extendVarEnv@).
115 varsTopBinds :: [StgBinding] -> LneM ([StgBinding], FreeVarsInfo)
117 varsTopBinds [] = returnLne ([], emptyFVInfo)
118 varsTopBinds (bind:binds)
119 = extendVarEnvLne env_extension (
120 varsTopBinds binds `thenLne` \ (binds', fv_binds) ->
121 varsTopBind binders' fv_binds bind `thenLne` \ (bind', fv_bind) ->
122 returnLne ((bind' : binds'),
123 (fv_binds `unionFVInfo` fv_bind) `minusFVBinders` binders'
129 StgNonRec binder rhs -> [(binder,rhs)]
130 StgRec pairs -> pairs
132 binders' = [ binder `setIdArityInfo` ArityExactly (rhsArity rhs)
133 | (binder, rhs) <- pairs
136 env_extension = binders' `zip` repeat how_bound
138 how_bound = LetrecBound
143 varsTopBind :: [Id] -- New binders (with correct arity)
144 -> FreeVarsInfo -- Info about the body
146 -> LneM (StgBinding, FreeVarsInfo)
148 varsTopBind [binder'] body_fvs (StgNonRec binder rhs)
149 = varsRhs body_fvs (binder,rhs) `thenLne` \ (rhs2, fvs, _) ->
150 returnLne (StgNonRec binder' rhs2, fvs)
152 varsTopBind binders' body_fvs (StgRec pairs)
153 = fixLne (\ ~(_, rec_rhs_fvs) ->
155 scope_fvs = unionFVInfo body_fvs rec_rhs_fvs
157 mapAndUnzip3Lne (varsRhs scope_fvs) pairs `thenLne` \ (rhss2, fvss, _) ->
159 fvs = unionFVInfos fvss
161 returnLne (StgRec (binders' `zip` rhss2), fvs)
167 varsRhs :: FreeVarsInfo -- Free var info for the scope of the binding
169 -> LneM (StgRhs, FreeVarsInfo, EscVarsSet)
171 varsRhs scope_fv_info (binder, StgRhsCon cc con args)
172 = varsAtoms args `thenLne` \ (args', fvs) ->
173 returnLne (StgRhsCon cc con args', fvs, getFVSet fvs)
175 varsRhs scope_fv_info (binder, StgRhsClosure cc _ srt _ upd args body)
176 = extendVarEnvLne [ (zapArity a, LambdaBound) | a <- args ] (
177 do_body args body `thenLne` \ (body2, body_fvs, body_escs) ->
179 set_of_args = mkVarSet args
180 rhs_fvs = body_fvs `minusFVBinders` args
181 rhs_escs = body_escs `minusVarSet` set_of_args
182 binder_info = lookupFVInfo scope_fv_info binder
183 upd' | null args && isPAP body2 = ReEntrant
186 returnLne (StgRhsClosure cc binder_info srt (getFVs rhs_fvs) upd'
187 args body2, rhs_fvs, rhs_escs)
190 -- Pick out special case of application in body of thunk
191 do_body [] (StgApp f args) = varsApp (Just upd) f args
192 do_body _ other_body = varsExpr other_body
195 Detect thunks which will reduce immediately to PAPs, and make them
196 non-updatable. This has several advantages:
198 - the non-updatable thunk behaves exactly like the PAP,
200 - the thunk is more efficient to enter, because it is
201 specialised to the task.
203 - we save one update frame, one stg_update_PAP, one update
204 and lots of PAP_enters.
206 - in the case where the thunk is top-level, we save building
207 a black hole and futhermore the thunk isn't considered to
208 be a CAF any more, so it doesn't appear in any SRTs.
210 We do it here, because the arity information is accurate, and we need
211 to do it before the SRT pass to save the SRT entries associated with
215 isPAP (StgApp f args) = idArity f > length args
220 varsAtoms :: [StgArg]
221 -> LneM ([StgArg], FreeVarsInfo)
222 -- It's not *really* necessary to return fresh arguments,
223 -- because the only difference is that the argument variable
224 -- arities are correct. But it seems safer to do so.
227 = mapAndUnzipLne var_atom atoms `thenLne` \ (args', fvs_lists) ->
228 returnLne (args', unionFVInfos fvs_lists)
230 var_atom a@(StgVarArg v)
231 = lookupVarLne v `thenLne` \ (v', how_bound) ->
232 returnLne (StgVarArg v', singletonFVInfo v' how_bound stgArgOcc)
233 var_atom a = returnLne (a, emptyFVInfo)
236 %************************************************************************
238 \subsection[expr-StgVarInfo]{Setting variable info on expressions}
240 %************************************************************************
242 @varsExpr@ carries in a monad-ised environment, which binds each
243 let(rec) variable (ie non top level, not imported, not lambda bound,
244 not case-alternative bound) to:
246 - its set of live vars.
247 For normal variables the set of live vars is just the variable
248 itself. For let-no-escaped variables, the set of live vars is the set
249 live at the moment the variable is entered. The set is guaranteed to
250 have no further let-no-escaped vars in it.
254 -> LneM (StgExpr, -- Decorated expr
255 FreeVarsInfo, -- Its free vars (NB free, not live)
256 EscVarsSet) -- Its escapees, a subset of its free vars;
257 -- also a subset of the domain of the envt
258 -- because we are only interested in the escapees
259 -- for vars which might be turned into
260 -- let-no-escaped ones.
263 The second and third components can be derived in a simple bottom up pass, not
264 dependent on any decisions about which variables will be let-no-escaped or
265 not. The first component, that is, the decorated expression, may then depend
266 on these components, but it in turn is not scrutinised as the basis for any
267 decisions. Hence no black holes.
270 varsExpr (StgLit l) = returnLne (StgLit l, emptyFVInfo, emptyVarSet)
272 varsExpr (StgApp f args) = varsApp Nothing f args
274 varsExpr (StgConApp con args)
275 = varsAtoms args `thenLne` \ (args', args_fvs) ->
276 returnLne (StgConApp con args', args_fvs, getFVSet args_fvs)
278 varsExpr (StgPrimApp op args res_ty)
279 = varsAtoms args `thenLne` \ (args', args_fvs) ->
280 returnLne (StgPrimApp op args' res_ty, args_fvs, getFVSet args_fvs)
282 varsExpr (StgSCC cc expr)
283 = varsExpr expr `thenLne` ( \ (expr2, fvs, escs) ->
284 returnLne (StgSCC cc expr2, fvs, escs) )
287 Cases require a little more real work.
289 varsExpr (StgCase scrut _ _ bndr srt alts)
290 = getVarsLiveInCont `thenLne` \ live_in_cont ->
291 extendVarEnvLne [(zapArity bndr, CaseBound)] (
292 vars_alts alts `thenLne` \ (alts2, alts_fvs, alts_escs) ->
293 lookupLiveVarsForSet alts_fvs `thenLne` \ alts_lvs ->
295 -- determine whether the default binder is dead or not
296 bndr'= if (bndr `elementOfFVInfo` alts_fvs)
297 then bndr `setIdOccInfo` NoOccInfo
298 else bndr `setIdOccInfo` IAmDead
300 -- for a _ccall_GC_, some of the *arguments* need to live across the
301 -- call (see findLiveArgs comments.), so we annotate them as being live
302 -- in the alts to achieve the desired effect.
303 mb_live_across_case =
305 StgPrimApp (CCallOp ccall) args _
307 -> Just (foldl findLiveArgs emptyVarSet args)
310 -- don't consider the default binder as being 'live in alts',
311 -- since this is from the point of view of the case expr, where
312 -- the default binder is not free.
313 live_in_alts = orElse (FMAP unionVarSet mb_live_across_case) id $
314 live_in_cont `unionVarSet`
315 (alts_lvs `minusVarSet` unitVarSet bndr)
317 -- we tell the scrutinee that everything live in the alts
318 -- is live in it, too.
319 setVarsLiveInCont live_in_alts (
321 ) `thenLne` \ (scrut2, scrut_fvs, scrut_escs) ->
322 lookupLiveVarsForSet scrut_fvs `thenLne` \ scrut_lvs ->
324 live_in_whole_case = live_in_alts `unionVarSet` scrut_lvs
327 StgCase scrut2 live_in_whole_case live_in_alts bndr' srt alts2,
328 (scrut_fvs `unionFVInfo` alts_fvs)
329 `minusFVBinders` [bndr],
330 (alts_escs `minusVarSet` unitVarSet bndr) `unionVarSet` getFVSet scrut_fvs
331 -- You might think we should have scrut_escs, not (getFVSet scrut_fvs),
332 -- but actually we can't call, and then return from, a let-no-escape thing.
336 vars_alts (StgAlgAlts ty alts deflt)
337 = mapAndUnzip3Lne vars_alg_alt alts
338 `thenLne` \ (alts2, alts_fvs_list, alts_escs_list) ->
340 alts_fvs = unionFVInfos alts_fvs_list
341 alts_escs = unionVarSets alts_escs_list
343 vars_deflt deflt `thenLne` \ (deflt2, deflt_fvs, deflt_escs) ->
345 StgAlgAlts ty alts2 deflt2,
346 alts_fvs `unionFVInfo` deflt_fvs,
347 alts_escs `unionVarSet` deflt_escs
350 vars_alg_alt (con, binders, worthless_use_mask, rhs)
351 = extendVarEnvLne [(zapArity b, CaseBound) | b <- binders] (
352 varsExpr rhs `thenLne` \ (rhs2, rhs_fvs, rhs_escs) ->
354 good_use_mask = [ b `elementOfFVInfo` rhs_fvs | b <- binders ]
355 -- records whether each param is used in the RHS
358 (con, binders, good_use_mask, rhs2),
359 rhs_fvs `minusFVBinders` binders,
360 rhs_escs `minusVarSet` mkVarSet binders -- ToDo: remove the minusVarSet;
361 -- since escs won't include
362 -- any of these binders
365 vars_alts (StgPrimAlts ty alts deflt)
366 = mapAndUnzip3Lne vars_prim_alt alts
367 `thenLne` \ (alts2, alts_fvs_list, alts_escs_list) ->
369 alts_fvs = unionFVInfos alts_fvs_list
370 alts_escs = unionVarSets alts_escs_list
372 vars_deflt deflt `thenLne` \ (deflt2, deflt_fvs, deflt_escs) ->
374 StgPrimAlts ty alts2 deflt2,
375 alts_fvs `unionFVInfo` deflt_fvs,
376 alts_escs `unionVarSet` deflt_escs
379 vars_prim_alt (lit, rhs)
380 = varsExpr rhs `thenLne` \ (rhs2, rhs_fvs, rhs_escs) ->
381 returnLne ((lit, rhs2), rhs_fvs, rhs_escs)
383 vars_deflt StgNoDefault
384 = returnLne (StgNoDefault, emptyFVInfo, emptyVarSet)
386 vars_deflt (StgBindDefault rhs)
387 = varsExpr rhs `thenLne` \ (rhs2, rhs_fvs, rhs_escs) ->
388 returnLne ( StgBindDefault rhs2, rhs_fvs, rhs_escs )
391 Lets not only take quite a bit of work, but this is where we convert
392 then to let-no-escapes, if we wish.
394 (Meanwhile, we don't expect to see let-no-escapes...)
396 varsExpr (StgLetNoEscape _ _ _ _) = panic "varsExpr: unexpected StgLetNoEscape"
398 varsExpr (StgLet bind body)
399 = isSwitchSetLne {-StgDoLetNoEscapes-} `thenLne` \ want_LNEs ->
401 (fixLne (\ ~(_, _, _, no_binder_escapes) ->
403 non_escaping_let = want_LNEs && no_binder_escapes
405 vars_let non_escaping_let bind body
406 )) `thenLne` \ (new_let, fvs, escs, _) ->
408 returnLne (new_let, fvs, escs)
411 If we've got a case containing a _ccall_GC_ primop, we need to
412 ensure that the arguments are kept live for the duration of the
413 call. This only an issue
416 findLiveArgs :: StgLiveVars -> StgArg -> StgLiveVars
417 findLiveArgs lvs (StgVarArg x)
418 | isForeignObjTy (idType x) = extendVarSet lvs x
420 findLiveArgs lvs arg = lvs
426 varsApp :: Maybe UpdateFlag -- Just upd <=> this application is
427 -- the rhs of a thunk binding
428 -- x = [...] \upd [] -> the_app
429 -- with specified update flag
431 -> [StgArg] -- Arguments
432 -> LneM (StgExpr, FreeVarsInfo, EscVarsSet)
434 varsApp maybe_thunk_body f args
435 = getVarsLiveInCont `thenLne` \ live_in_cont ->
437 varsAtoms args `thenLne` \ (args', args_fvs) ->
439 lookupVarLne f `thenLne` \ (f', how_bound) ->
443 not_letrec_bound = not (isLetrecBound how_bound)
444 f_arity = idArity f' -- Will have an exact arity by now
445 fun_fvs = singletonFVInfo f' how_bound fun_occ
448 | not_letrec_bound = NoStgBinderInfo -- Uninteresting variable
450 -- Otherwise it is letrec bound; must have its arity
451 | n_args == 0 = stgFakeFunAppOcc -- Function Application
452 -- with no arguments.
453 -- used by the lambda lifter.
454 | f_arity > n_args = stgUnsatOcc -- Unsaturated
457 | f_arity == n_args &&
458 maybeToBool maybe_thunk_body -- Exactly saturated,
460 = case maybe_thunk_body of
461 Just Updatable -> stgStdHeapOcc
462 Just SingleEntry -> stgNoUpdHeapOcc
463 other -> panic "varsApp"
465 | otherwise = stgNormalOcc
466 -- Record only that it occurs free
468 myself = unitVarSet f'
470 fun_escs | not_letrec_bound = emptyVarSet -- Only letrec-bound escapees are interesting
471 | f_arity == n_args = emptyVarSet -- Function doesn't escape
472 | otherwise = myself -- Inexact application; it does escape
474 -- At the moment of the call:
476 -- either the function is *not* let-no-escaped, in which case
477 -- nothing is live except live_in_cont
478 -- or the function *is* let-no-escaped in which case the
479 -- variables it uses are live, but still the function
480 -- itself is not. PS. In this case, the function's
481 -- live vars should already include those of the
482 -- continuation, but it does no harm to just union the
487 -- = live_in_cont `unionVarSet` case how_bound of
488 -- LetrecBound _ lvs -> lvs `minusVarSet` myself
489 -- other -> emptyVarSet
493 fun_fvs `unionFVInfo` args_fvs,
494 fun_escs `unionVarSet` (getFVSet args_fvs)
495 -- All the free vars of the args are disqualified
496 -- from being let-no-escaped.
502 vars_let :: Bool -- True <=> yes, we are let-no-escaping this let
503 -> StgBinding -- bindings
505 -> LneM (StgExpr, -- new let
506 FreeVarsInfo, -- variables free in the whole let
507 EscVarsSet, -- variables that escape from the whole let
508 Bool) -- True <=> none of the binders in the bindings
509 -- is among the escaping vars
511 vars_let let_no_escape bind body
512 = fixLne (\ ~(_, _, _, rec_bind_lvs, _, rec_body_fvs, _, _) ->
514 -- Do the bindings, setting live_in_cont to empty if
515 -- we ain't in a let-no-escape world
516 getVarsLiveInCont `thenLne` \ live_in_cont ->
518 (if let_no_escape then live_in_cont else emptyVarSet)
519 (vars_bind rec_bind_lvs rec_body_fvs bind)
520 `thenLne` \ (bind2, bind_fvs, bind_escs, env_ext) ->
522 -- The live variables of this binding are the ones which are live
523 -- by virtue of being accessible via the free vars of the binding (lvs_from_fvs)
524 -- together with the live_in_cont ones
525 lookupLiveVarsForSet (bind_fvs `minusFVBinders` binders) `thenLne` \ lvs_from_fvs ->
527 bind_lvs = lvs_from_fvs `unionVarSet` live_in_cont
530 -- bind_fvs and bind_escs still include the binders of the let(rec)
531 -- but bind_lvs does not
534 extendVarEnvLne env_ext (
535 varsExpr body `thenLne` \ (body2, body_fvs, body_escs) ->
536 lookupLiveVarsForSet body_fvs `thenLne` \ body_lvs ->
538 returnLne (bind2, bind_fvs, bind_escs, bind_lvs,
539 body2, body_fvs, body_escs, body_lvs)
541 )) `thenLne` (\ (bind2, bind_fvs, bind_escs, bind_lvs,
542 body2, body_fvs, body_escs, body_lvs) ->
545 -- Compute the new let-expression
547 new_let | let_no_escape = StgLetNoEscape live_in_whole_let bind_lvs bind2 body2
548 | otherwise = StgLet bind2 body2
551 = (bind_fvs `unionFVInfo` body_fvs) `minusFVBinders` binders
554 = bind_lvs `unionVarSet` (body_lvs `minusVarSet` set_of_binders)
556 real_bind_escs = if let_no_escape then
560 -- Everything escapes which is free in the bindings
562 let_escs = (real_bind_escs `unionVarSet` body_escs) `minusVarSet` set_of_binders
564 all_escs = bind_escs `unionVarSet` body_escs -- Still includes binders of
567 no_binder_escapes = isEmptyVarSet (set_of_binders `intersectVarSet` all_escs)
570 -- Debugging code as requested by Andrew Kennedy
571 checked_no_binder_escapes
572 | not no_binder_escapes && any is_join_var binders
573 = pprTrace "Interesting! A join var that isn't let-no-escaped" (ppr binders)
575 | otherwise = no_binder_escapes
577 checked_no_binder_escapes = no_binder_escapes
580 -- Mustn't depend on the passed-in let_no_escape flag, since
581 -- no_binder_escapes is used by the caller to derive the flag!
587 checked_no_binder_escapes
590 set_of_binders = mkVarSet binders
591 binders = case bind of
592 StgNonRec binder rhs -> [binder]
593 StgRec pairs -> map fst pairs
595 mk_binding bind_lvs (binder,rhs)
596 = (binder `setIdArityInfo` ArityExactly (stgArity rhs),
597 LetrecBound False -- Not top level
601 live_vars = if let_no_escape then
602 extendVarSet bind_lvs binder
606 vars_bind :: StgLiveVars
607 -> FreeVarsInfo -- Free var info for body of binding
610 FreeVarsInfo, EscVarsSet, -- free vars; escapee vars
612 -- extension to environment
614 vars_bind rec_bind_lvs rec_body_fvs (StgNonRec binder rhs)
615 = varsRhs rec_body_fvs (binder,rhs) `thenLne` \ (rhs2, fvs, escs) ->
617 env_ext_item@(binder', _) = mk_binding rec_bind_lvs (binder,rhs)
619 returnLne (StgNonRec binder' rhs2, fvs, escs, [env_ext_item])
621 vars_bind rec_bind_lvs rec_body_fvs (StgRec pairs)
623 env_ext = map (mk_binding rec_bind_lvs) pairs
624 binders' = map fst env_ext
626 extendVarEnvLne env_ext (
627 fixLne (\ ~(_, rec_rhs_fvs, _, _) ->
629 rec_scope_fvs = unionFVInfo rec_body_fvs rec_rhs_fvs
631 mapAndUnzip3Lne (varsRhs rec_scope_fvs) pairs `thenLne` \ (rhss2, fvss, escss) ->
633 fvs = unionFVInfos fvss
634 escs = unionVarSets escss
636 returnLne (StgRec (binders' `zip` rhss2), fvs, escs, env_ext)
639 is_join_var :: Id -> Bool
640 -- A hack (used only for compiler debuggging) to tell if
641 -- a variable started life as a join point ($j)
642 is_join_var j = occNameUserString (getOccName j) == "$j"
645 %************************************************************************
647 \subsection[LNE-monad]{A little monad for this let-no-escaping pass}
649 %************************************************************************
651 There's a lot of stuff to pass around, so we use this @LneM@ monad to
652 help. All the stuff here is only passed {\em down}.
655 type LneM a = Bool -- True <=> do let-no-escapes
656 -> IdEnv (Id, HowBound) -- Use the Id at all occurrences; it has correct
657 -- arity information inside it.
658 -> StgLiveVars -- vars live in continuation
666 Bool -- True <=> bound at top level
667 StgLiveVars -- Live vars... see notes below
669 isLetrecBound (LetrecBound _ _) = True
670 isLetrecBound other = False
673 For a let(rec)-bound variable, x, we record what varibles are live if
674 x is live. For "normal" variables that is just x alone. If x is
675 a let-no-escaped variable then x is represented by a code pointer and
676 a stack pointer (well, one for each stack). So all of the variables
677 needed in the execution of x are live if x is, and are therefore recorded
678 in the LetrecBound constructor; x itself *is* included.
680 The std monad functions:
682 initLne :: Bool -> LneM a -> a
683 initLne want_LNEs m = m want_LNEs emptyVarEnv emptyVarSet
685 {-# INLINE thenLne #-}
686 {-# INLINE thenLne_ #-}
687 {-# INLINE returnLne #-}
689 returnLne :: a -> LneM a
690 returnLne e sw env lvs_cont = e
692 thenLne :: LneM a -> (a -> LneM b) -> LneM b
693 thenLne m k sw env lvs_cont
694 = case (m sw env lvs_cont) of
695 m_result -> k m_result sw env lvs_cont
697 thenLne_ :: LneM a -> LneM b -> LneM b
698 thenLne_ m k sw env lvs_cont
699 = case (m sw env lvs_cont) of
700 _ -> k sw env lvs_cont
702 mapLne :: (a -> LneM b) -> [a] -> LneM [b]
703 mapLne f [] = returnLne []
705 = f x `thenLne` \ r ->
706 mapLne f xs `thenLne` \ rs ->
709 mapAndUnzipLne :: (a -> LneM (b,c)) -> [a] -> LneM ([b],[c])
711 mapAndUnzipLne f [] = returnLne ([],[])
712 mapAndUnzipLne f (x:xs)
713 = f x `thenLne` \ (r1, r2) ->
714 mapAndUnzipLne f xs `thenLne` \ (rs1, rs2) ->
715 returnLne (r1:rs1, r2:rs2)
717 mapAndUnzip3Lne :: (a -> LneM (b,c,d)) -> [a] -> LneM ([b],[c],[d])
719 mapAndUnzip3Lne f [] = returnLne ([],[],[])
720 mapAndUnzip3Lne f (x:xs)
721 = f x `thenLne` \ (r1, r2, r3) ->
722 mapAndUnzip3Lne f xs `thenLne` \ (rs1, rs2, rs3) ->
723 returnLne (r1:rs1, r2:rs2, r3:rs3)
725 fixLne :: (a -> LneM a) -> LneM a
726 fixLne expr sw env lvs_cont = result
728 result = expr result sw env lvs_cont
729 -- ^^^^^^ ------ ^^^^^^
732 Functions specific to this monad:
734 isSwitchSetLne :: LneM Bool
735 isSwitchSetLne want_LNEs env lvs_cont
738 getVarsLiveInCont :: LneM StgLiveVars
739 getVarsLiveInCont sw env lvs_cont = lvs_cont
741 setVarsLiveInCont :: StgLiveVars -> LneM a -> LneM a
742 setVarsLiveInCont new_lvs_cont expr sw env lvs_cont
743 = expr sw env new_lvs_cont
745 extendVarEnvLne :: [(Id, HowBound)] -> LneM a -> LneM a
746 extendVarEnvLne ids_w_howbound expr sw env lvs_cont
747 = expr sw (extendVarEnvList env [(id, pair) | pair@(id,_) <- ids_w_howbound]) lvs_cont
750 lookupVarLne :: Id -> LneM (Id, HowBound)
751 lookupVarLne v sw env lvs_cont
753 case (lookupVarEnv env v) of
755 Nothing -> --false:ASSERT(not (isLocallyDefined v))
759 -- The result of lookupLiveVarsForSet, a set of live variables, is
760 -- only ever tacked onto a decorated expression. It is never used as
761 -- the basis of a control decision, which might give a black hole.
763 lookupLiveVarsForSet :: FreeVarsInfo -> LneM StgLiveVars
765 lookupLiveVarsForSet fvs sw env lvs_cont
766 = returnLne (unionVarSets (map do_one (getFVs fvs)))
770 = if isLocallyDefined v then
771 case (lookupVarEnv env v) of
772 Just (_, LetrecBound _ lvs) -> extendVarSet lvs v
773 Just _ -> unitVarSet v
774 Nothing -> pprPanic "lookupVarEnv/do_one:" (ppr v)
780 %************************************************************************
782 \subsection[Free-var info]{Free variable information}
784 %************************************************************************
787 type FreeVarsInfo = IdEnv (Id, Bool, StgBinderInfo)
788 -- If f is mapped to NoStgBinderInfo, that means
789 -- that f *is* mentioned (else it wouldn't be in the
790 -- IdEnv at all), but only in a saturated applications.
792 -- All case/lambda-bound things are also mapped to
793 -- NoStgBinderInfo, since we aren't interested in their
796 -- The Bool is True <=> the Id is top level letrec bound
798 type EscVarsSet = IdSet
802 emptyFVInfo :: FreeVarsInfo
803 emptyFVInfo = emptyVarEnv
805 singletonFVInfo :: Id -> HowBound -> StgBinderInfo -> FreeVarsInfo
806 singletonFVInfo id ImportBound info = emptyVarEnv
807 singletonFVInfo id (LetrecBound top_level _) info = unitVarEnv id (id, top_level, info)
808 singletonFVInfo id other info = unitVarEnv id (id, False, info)
810 unionFVInfo :: FreeVarsInfo -> FreeVarsInfo -> FreeVarsInfo
811 unionFVInfo fv1 fv2 = plusVarEnv_C plusFVInfo fv1 fv2
813 unionFVInfos :: [FreeVarsInfo] -> FreeVarsInfo
814 unionFVInfos fvs = foldr unionFVInfo emptyFVInfo fvs
816 minusFVBinders :: FreeVarsInfo -> [Id] -> FreeVarsInfo
817 minusFVBinders fv ids = fv `delVarEnvList` ids
819 elementOfFVInfo :: Id -> FreeVarsInfo -> Bool
820 elementOfFVInfo id fvs = maybeToBool (lookupVarEnv fvs id)
822 lookupFVInfo :: FreeVarsInfo -> Id -> StgBinderInfo
823 lookupFVInfo fvs id = case lookupVarEnv fvs id of
824 Nothing -> NoStgBinderInfo
825 Just (_,_,info) -> info
827 getFVs :: FreeVarsInfo -> [Id] -- Non-top-level things only
828 getFVs fvs = [id | (id,False,_) <- rngVarEnv fvs]
830 getFVSet :: FreeVarsInfo -> IdSet
831 getFVSet fvs = mkVarSet (getFVs fvs)
833 plusFVInfo (id1,top1,info1) (id2,top2,info2)
834 = ASSERT (id1 == id2 && top1 == top2)
835 (id1, top1, combineStgBinderInfo info1 info2)
839 rhsArity :: StgRhs -> Arity
840 rhsArity (StgRhsCon _ _ _) = 0
841 rhsArity (StgRhsClosure _ _ _ _ _ args _) = length args
844 zapArity id = id `setIdArityInfo` UnknownArity