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 ( isLocalId, setIdArityInfo, idArity, setIdOccInfo, Id )
20 import IdInfo ( ArityInfo(..), OccInfo(..) )
21 import PrimOp ( PrimOp(..), ccallMayGC )
22 import TysPrim ( foreignObjPrimTyCon )
23 import Type ( splitTyConApp_maybe )
24 import Maybes ( maybeToBool, orElse )
25 import Name ( 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 tycon 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 tycon 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 tycon 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 tycon 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 | isForeignObjPrimTy (idType x) = extendVarSet lvs x
420 findLiveArgs lvs arg = lvs
422 isForeignObjPrimTy ty
423 = case splitTyConApp_maybe ty of
424 Just (tycon, _) -> tycon == foreignObjPrimTyCon
431 varsApp :: Maybe UpdateFlag -- Just upd <=> this application is
432 -- the rhs of a thunk binding
433 -- x = [...] \upd [] -> the_app
434 -- with specified update flag
436 -> [StgArg] -- Arguments
437 -> LneM (StgExpr, FreeVarsInfo, EscVarsSet)
439 varsApp maybe_thunk_body f args
440 = getVarsLiveInCont `thenLne` \ live_in_cont ->
442 varsAtoms args `thenLne` \ (args', args_fvs) ->
444 lookupVarLne f `thenLne` \ (f', how_bound) ->
448 not_letrec_bound = not (isLetrecBound how_bound)
449 f_arity = idArity f' -- Will have an exact arity by now
450 fun_fvs = singletonFVInfo f' how_bound fun_occ
453 | not_letrec_bound = NoStgBinderInfo -- Uninteresting variable
455 -- Otherwise it is letrec bound; must have its arity
456 | n_args == 0 = stgFakeFunAppOcc -- Function Application
457 -- with no arguments.
458 -- used by the lambda lifter.
459 | f_arity > n_args = stgUnsatOcc -- Unsaturated
462 | f_arity == n_args &&
463 maybeToBool maybe_thunk_body -- Exactly saturated,
465 = case maybe_thunk_body of
466 Just Updatable -> stgStdHeapOcc
467 Just SingleEntry -> stgNoUpdHeapOcc
468 other -> panic "varsApp"
470 | otherwise = stgNormalOcc
471 -- Record only that it occurs free
473 myself = unitVarSet f'
475 fun_escs | not_letrec_bound = emptyVarSet -- Only letrec-bound escapees are interesting
476 | f_arity == n_args = emptyVarSet -- Function doesn't escape
477 | otherwise = myself -- Inexact application; it does escape
479 -- At the moment of the call:
481 -- either the function is *not* let-no-escaped, in which case
482 -- nothing is live except live_in_cont
483 -- or the function *is* let-no-escaped in which case the
484 -- variables it uses are live, but still the function
485 -- itself is not. PS. In this case, the function's
486 -- live vars should already include those of the
487 -- continuation, but it does no harm to just union the
492 -- = live_in_cont `unionVarSet` case how_bound of
493 -- LetrecBound _ lvs -> lvs `minusVarSet` myself
494 -- other -> emptyVarSet
498 fun_fvs `unionFVInfo` args_fvs,
499 fun_escs `unionVarSet` (getFVSet args_fvs)
500 -- All the free vars of the args are disqualified
501 -- from being let-no-escaped.
507 vars_let :: Bool -- True <=> yes, we are let-no-escaping this let
508 -> StgBinding -- bindings
510 -> LneM (StgExpr, -- new let
511 FreeVarsInfo, -- variables free in the whole let
512 EscVarsSet, -- variables that escape from the whole let
513 Bool) -- True <=> none of the binders in the bindings
514 -- is among the escaping vars
516 vars_let let_no_escape bind body
517 = fixLne (\ ~(_, _, _, rec_bind_lvs, _, rec_body_fvs, _, _) ->
519 -- Do the bindings, setting live_in_cont to empty if
520 -- we ain't in a let-no-escape world
521 getVarsLiveInCont `thenLne` \ live_in_cont ->
523 (if let_no_escape then live_in_cont else emptyVarSet)
524 (vars_bind rec_bind_lvs rec_body_fvs bind)
525 `thenLne` \ (bind2, bind_fvs, bind_escs, env_ext) ->
527 -- The live variables of this binding are the ones which are live
528 -- by virtue of being accessible via the free vars of the binding (lvs_from_fvs)
529 -- together with the live_in_cont ones
530 lookupLiveVarsForSet (bind_fvs `minusFVBinders` binders) `thenLne` \ lvs_from_fvs ->
532 bind_lvs = lvs_from_fvs `unionVarSet` live_in_cont
535 -- bind_fvs and bind_escs still include the binders of the let(rec)
536 -- but bind_lvs does not
539 extendVarEnvLne env_ext (
540 varsExpr body `thenLne` \ (body2, body_fvs, body_escs) ->
541 lookupLiveVarsForSet body_fvs `thenLne` \ body_lvs ->
543 returnLne (bind2, bind_fvs, bind_escs, bind_lvs,
544 body2, body_fvs, body_escs, body_lvs)
546 )) `thenLne` (\ (bind2, bind_fvs, bind_escs, bind_lvs,
547 body2, body_fvs, body_escs, body_lvs) ->
550 -- Compute the new let-expression
552 new_let | let_no_escape = StgLetNoEscape live_in_whole_let bind_lvs bind2 body2
553 | otherwise = StgLet bind2 body2
556 = (bind_fvs `unionFVInfo` body_fvs) `minusFVBinders` binders
559 = bind_lvs `unionVarSet` (body_lvs `minusVarSet` set_of_binders)
561 real_bind_escs = if let_no_escape then
565 -- Everything escapes which is free in the bindings
567 let_escs = (real_bind_escs `unionVarSet` body_escs) `minusVarSet` set_of_binders
569 all_escs = bind_escs `unionVarSet` body_escs -- Still includes binders of
572 no_binder_escapes = isEmptyVarSet (set_of_binders `intersectVarSet` all_escs)
575 -- Debugging code as requested by Andrew Kennedy
576 checked_no_binder_escapes
577 | not no_binder_escapes && any is_join_var binders
578 = pprTrace "Interesting! A join var that isn't let-no-escaped" (ppr binders)
580 | otherwise = no_binder_escapes
582 checked_no_binder_escapes = no_binder_escapes
585 -- Mustn't depend on the passed-in let_no_escape flag, since
586 -- no_binder_escapes is used by the caller to derive the flag!
592 checked_no_binder_escapes
595 set_of_binders = mkVarSet binders
596 binders = case bind of
597 StgNonRec binder rhs -> [binder]
598 StgRec pairs -> map fst pairs
600 mk_binding bind_lvs (binder,rhs)
601 = (binder `setIdArityInfo` ArityExactly (stgArity rhs),
602 LetrecBound False -- Not top level
606 live_vars = if let_no_escape then
607 extendVarSet bind_lvs binder
611 vars_bind :: StgLiveVars
612 -> FreeVarsInfo -- Free var info for body of binding
615 FreeVarsInfo, EscVarsSet, -- free vars; escapee vars
617 -- extension to environment
619 vars_bind rec_bind_lvs rec_body_fvs (StgNonRec binder rhs)
620 = varsRhs rec_body_fvs (binder,rhs) `thenLne` \ (rhs2, fvs, escs) ->
622 env_ext_item@(binder', _) = mk_binding rec_bind_lvs (binder,rhs)
624 returnLne (StgNonRec binder' rhs2, fvs, escs, [env_ext_item])
626 vars_bind rec_bind_lvs rec_body_fvs (StgRec pairs)
628 env_ext = map (mk_binding rec_bind_lvs) pairs
629 binders' = map fst env_ext
631 extendVarEnvLne env_ext (
632 fixLne (\ ~(_, rec_rhs_fvs, _, _) ->
634 rec_scope_fvs = unionFVInfo rec_body_fvs rec_rhs_fvs
636 mapAndUnzip3Lne (varsRhs rec_scope_fvs) pairs `thenLne` \ (rhss2, fvss, escss) ->
638 fvs = unionFVInfos fvss
639 escs = unionVarSets escss
641 returnLne (StgRec (binders' `zip` rhss2), fvs, escs, env_ext)
644 is_join_var :: Id -> Bool
645 -- A hack (used only for compiler debuggging) to tell if
646 -- a variable started life as a join point ($j)
647 is_join_var j = occNameUserString (getOccName j) == "$j"
650 %************************************************************************
652 \subsection[LNE-monad]{A little monad for this let-no-escaping pass}
654 %************************************************************************
656 There's a lot of stuff to pass around, so we use this @LneM@ monad to
657 help. All the stuff here is only passed {\em down}.
660 type LneM a = Bool -- True <=> do let-no-escapes
661 -> IdEnv (Id, HowBound) -- Use the Id at all occurrences; it has correct
662 -- arity information inside it.
663 -> StgLiveVars -- vars live in continuation
671 Bool -- True <=> bound at top level
672 StgLiveVars -- Live vars... see notes below
674 isLetrecBound (LetrecBound _ _) = True
675 isLetrecBound other = False
678 For a let(rec)-bound variable, x, we record what varibles are live if
679 x is live. For "normal" variables that is just x alone. If x is
680 a let-no-escaped variable then x is represented by a code pointer and
681 a stack pointer (well, one for each stack). So all of the variables
682 needed in the execution of x are live if x is, and are therefore recorded
683 in the LetrecBound constructor; x itself *is* included.
685 The std monad functions:
687 initLne :: Bool -> LneM a -> a
688 initLne want_LNEs m = m want_LNEs emptyVarEnv emptyVarSet
690 {-# INLINE thenLne #-}
691 {-# INLINE thenLne_ #-}
692 {-# INLINE returnLne #-}
694 returnLne :: a -> LneM a
695 returnLne e sw env lvs_cont = e
697 thenLne :: LneM a -> (a -> LneM b) -> LneM b
698 thenLne m k sw env lvs_cont
699 = case (m sw env lvs_cont) of
700 m_result -> k m_result sw env lvs_cont
702 thenLne_ :: LneM a -> LneM b -> LneM b
703 thenLne_ m k sw env lvs_cont
704 = case (m sw env lvs_cont) of
705 _ -> k sw env lvs_cont
707 mapLne :: (a -> LneM b) -> [a] -> LneM [b]
708 mapLne f [] = returnLne []
710 = f x `thenLne` \ r ->
711 mapLne f xs `thenLne` \ rs ->
714 mapAndUnzipLne :: (a -> LneM (b,c)) -> [a] -> LneM ([b],[c])
716 mapAndUnzipLne f [] = returnLne ([],[])
717 mapAndUnzipLne f (x:xs)
718 = f x `thenLne` \ (r1, r2) ->
719 mapAndUnzipLne f xs `thenLne` \ (rs1, rs2) ->
720 returnLne (r1:rs1, r2:rs2)
722 mapAndUnzip3Lne :: (a -> LneM (b,c,d)) -> [a] -> LneM ([b],[c],[d])
724 mapAndUnzip3Lne f [] = returnLne ([],[],[])
725 mapAndUnzip3Lne f (x:xs)
726 = f x `thenLne` \ (r1, r2, r3) ->
727 mapAndUnzip3Lne f xs `thenLne` \ (rs1, rs2, rs3) ->
728 returnLne (r1:rs1, r2:rs2, r3:rs3)
730 fixLne :: (a -> LneM a) -> LneM a
731 fixLne expr sw env lvs_cont = result
733 result = expr result sw env lvs_cont
734 -- ^^^^^^ ------ ^^^^^^
737 Functions specific to this monad:
739 isSwitchSetLne :: LneM Bool
740 isSwitchSetLne want_LNEs env lvs_cont
743 getVarsLiveInCont :: LneM StgLiveVars
744 getVarsLiveInCont sw env lvs_cont = lvs_cont
746 setVarsLiveInCont :: StgLiveVars -> LneM a -> LneM a
747 setVarsLiveInCont new_lvs_cont expr sw env lvs_cont
748 = expr sw env new_lvs_cont
750 extendVarEnvLne :: [(Id, HowBound)] -> LneM a -> LneM a
751 extendVarEnvLne ids_w_howbound expr sw env lvs_cont
752 = expr sw (extendVarEnvList env [(id, pair) | pair@(id,_) <- ids_w_howbound]) lvs_cont
755 lookupVarLne :: Id -> LneM (Id, HowBound)
756 lookupVarLne v sw env lvs_cont
758 case (lookupVarEnv env v) of
760 Nothing -> --false:ASSERT(not (isLocallyDefined v))
764 -- The result of lookupLiveVarsForSet, a set of live variables, is
765 -- only ever tacked onto a decorated expression. It is never used as
766 -- the basis of a control decision, which might give a black hole.
768 lookupLiveVarsForSet :: FreeVarsInfo -> LneM StgLiveVars
770 lookupLiveVarsForSet fvs sw env lvs_cont
771 = returnLne (unionVarSets (map do_one (getFVs fvs)))
775 = if isLocalId v then
776 case (lookupVarEnv env v) of
777 Just (_, LetrecBound _ lvs) -> extendVarSet lvs v
778 Just _ -> unitVarSet v
779 Nothing -> pprPanic "lookupVarEnv/do_one:" (ppr v)
785 %************************************************************************
787 \subsection[Free-var info]{Free variable information}
789 %************************************************************************
792 type FreeVarsInfo = IdEnv (Id, Bool, StgBinderInfo)
793 -- If f is mapped to NoStgBinderInfo, that means
794 -- that f *is* mentioned (else it wouldn't be in the
795 -- IdEnv at all), but only in a saturated applications.
797 -- All case/lambda-bound things are also mapped to
798 -- NoStgBinderInfo, since we aren't interested in their
801 -- The Bool is True <=> the Id is top level letrec bound
803 type EscVarsSet = IdSet
807 emptyFVInfo :: FreeVarsInfo
808 emptyFVInfo = emptyVarEnv
810 singletonFVInfo :: Id -> HowBound -> StgBinderInfo -> FreeVarsInfo
811 singletonFVInfo id ImportBound info = emptyVarEnv
812 singletonFVInfo id (LetrecBound top_level _) info = unitVarEnv id (id, top_level, info)
813 singletonFVInfo id other info = unitVarEnv id (id, False, info)
815 unionFVInfo :: FreeVarsInfo -> FreeVarsInfo -> FreeVarsInfo
816 unionFVInfo fv1 fv2 = plusVarEnv_C plusFVInfo fv1 fv2
818 unionFVInfos :: [FreeVarsInfo] -> FreeVarsInfo
819 unionFVInfos fvs = foldr unionFVInfo emptyFVInfo fvs
821 minusFVBinders :: FreeVarsInfo -> [Id] -> FreeVarsInfo
822 minusFVBinders fv ids = fv `delVarEnvList` ids
824 elementOfFVInfo :: Id -> FreeVarsInfo -> Bool
825 elementOfFVInfo id fvs = maybeToBool (lookupVarEnv fvs id)
827 lookupFVInfo :: FreeVarsInfo -> Id -> StgBinderInfo
828 lookupFVInfo fvs id = case lookupVarEnv fvs id of
829 Nothing -> NoStgBinderInfo
830 Just (_,_,info) -> info
832 getFVs :: FreeVarsInfo -> [Id] -- Non-top-level things only
833 getFVs fvs = [id | (id,False,_) <- rngVarEnv fvs]
835 getFVSet :: FreeVarsInfo -> IdSet
836 getFVSet fvs = mkVarSet (getFVs fvs)
838 plusFVInfo (id1,top1,info1) (id2,top2,info2)
839 = ASSERT (id1 == id2 && top1 == top2)
840 (id1, top1, combineStgBinderInfo info1 info2)
844 rhsArity :: StgRhs -> Arity
845 rhsArity (StgRhsCon _ _ _) = 0
846 rhsArity (StgRhsClosure _ _ _ _ _ args _) = length args
849 zapArity id = id `setIdArityInfo` UnknownArity