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 ( setIdArity, getIdArity, setIdOccInfo, Id )
20 import Const ( Con(..) )
21 import IdInfo ( ArityInfo(..), OccInfo(..),
23 import PrimOp ( PrimOp(..) )
24 import TysWiredIn ( isForeignObjTy )
25 import Maybes ( maybeToBool, orElse )
26 import Name ( isLocallyDefined )
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 `setIdArity` 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)
216 = case getIdArity f of
217 ArityExactly n -> n > n_args
218 ArityAtLeast n -> n > n_args
220 where n_args = length args
225 varsAtoms :: [StgArg]
226 -> LneM ([StgArg], FreeVarsInfo)
227 -- It's not *really* necessary to return fresh arguments,
228 -- because the only difference is that the argument variable
229 -- arities are correct. But it seems safer to do so.
232 = mapAndUnzipLne var_atom atoms `thenLne` \ (args', fvs_lists) ->
233 returnLne (args', unionFVInfos fvs_lists)
235 var_atom a@(StgConArg _) = returnLne (a, emptyFVInfo)
236 var_atom a@(StgVarArg v)
237 = lookupVarLne v `thenLne` \ (v', how_bound) ->
238 returnLne (StgVarArg v', singletonFVInfo v' how_bound stgArgOcc)
241 %************************************************************************
243 \subsection[expr-StgVarInfo]{Setting variable info on expressions}
245 %************************************************************************
247 @varsExpr@ carries in a monad-ised environment, which binds each
248 let(rec) variable (ie non top level, not imported, not lambda bound,
249 not case-alternative bound) to:
251 - its set of live vars.
252 For normal variables the set of live vars is just the variable
253 itself. For let-no-escaped variables, the set of live vars is the set
254 live at the moment the variable is entered. The set is guaranteed to
255 have no further let-no-escaped vars in it.
259 -> LneM (StgExpr, -- Decorated expr
260 FreeVarsInfo, -- Its free vars (NB free, not live)
261 EscVarsSet) -- Its escapees, a subset of its free vars;
262 -- also a subset of the domain of the envt
263 -- because we are only interested in the escapees
264 -- for vars which might be turned into
265 -- let-no-escaped ones.
268 The second and third components can be derived in a simple bottom up pass, not
269 dependent on any decisions about which variables will be let-no-escaped or
270 not. The first component, that is, the decorated expression, may then depend
271 on these components, but it in turn is not scrutinised as the basis for any
272 decisions. Hence no black holes.
275 varsExpr (StgApp f args) = varsApp Nothing f args
277 varsExpr (StgCon con args res_ty)
278 = getVarsLiveInCont `thenLne` \ live_in_cont ->
279 varsAtoms args `thenLne` \ (args', args_fvs) ->
280 returnLne (StgCon con 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 StgCon (PrimOp (CCallOp _ _ True{- _ccall_GC_ -} _)) args _ ->
306 Just (foldl findLiveArgs emptyVarSet args)
309 -- don't consider the default binder as being 'live in alts',
310 -- since this is from the point of view of the case expr, where
311 -- the default binder is not free.
312 live_in_alts = orElse (FMAP unionVarSet mb_live_across_case) id $
313 live_in_cont `unionVarSet`
314 (alts_lvs `minusVarSet` unitVarSet bndr)
316 -- we tell the scrutinee that everything live in the alts
317 -- is live in it, too.
318 setVarsLiveInCont live_in_alts (
320 ) `thenLne` \ (scrut2, scrut_fvs, scrut_escs) ->
321 lookupLiveVarsForSet scrut_fvs `thenLne` \ scrut_lvs ->
323 live_in_whole_case = live_in_alts `unionVarSet` scrut_lvs
326 StgCase scrut2 live_in_whole_case live_in_alts bndr' srt alts2,
327 (scrut_fvs `unionFVInfo` alts_fvs)
328 `minusFVBinders` [bndr],
329 (alts_escs `minusVarSet` unitVarSet bndr) `unionVarSet` getFVSet scrut_fvs
330 -- You might think we should have scrut_escs, not (getFVSet scrut_fvs),
331 -- but actually we can't call, and then return from, a let-no-escape thing.
335 vars_alts (StgAlgAlts ty alts deflt)
336 = mapAndUnzip3Lne vars_alg_alt alts
337 `thenLne` \ (alts2, alts_fvs_list, alts_escs_list) ->
339 alts_fvs = unionFVInfos alts_fvs_list
340 alts_escs = unionVarSets alts_escs_list
342 vars_deflt deflt `thenLne` \ (deflt2, deflt_fvs, deflt_escs) ->
344 StgAlgAlts ty alts2 deflt2,
345 alts_fvs `unionFVInfo` deflt_fvs,
346 alts_escs `unionVarSet` deflt_escs
349 vars_alg_alt (con, binders, worthless_use_mask, rhs)
350 = extendVarEnvLne [(zapArity b, CaseBound) | b <- binders] (
351 varsExpr rhs `thenLne` \ (rhs2, rhs_fvs, rhs_escs) ->
353 good_use_mask = [ b `elementOfFVInfo` rhs_fvs | b <- binders ]
354 -- records whether each param is used in the RHS
357 (con, binders, good_use_mask, rhs2),
358 rhs_fvs `minusFVBinders` binders,
359 rhs_escs `minusVarSet` mkVarSet binders -- ToDo: remove the minusVarSet;
360 -- since escs won't include
361 -- any of these binders
364 vars_alts (StgPrimAlts ty alts deflt)
365 = mapAndUnzip3Lne vars_prim_alt alts
366 `thenLne` \ (alts2, alts_fvs_list, alts_escs_list) ->
368 alts_fvs = unionFVInfos alts_fvs_list
369 alts_escs = unionVarSets alts_escs_list
371 vars_deflt deflt `thenLne` \ (deflt2, deflt_fvs, deflt_escs) ->
373 StgPrimAlts ty alts2 deflt2,
374 alts_fvs `unionFVInfo` deflt_fvs,
375 alts_escs `unionVarSet` deflt_escs
378 vars_prim_alt (lit, rhs)
379 = varsExpr rhs `thenLne` \ (rhs2, rhs_fvs, rhs_escs) ->
380 returnLne ((lit, rhs2), rhs_fvs, rhs_escs)
382 vars_deflt StgNoDefault
383 = returnLne (StgNoDefault, emptyFVInfo, emptyVarSet)
385 vars_deflt (StgBindDefault rhs)
386 = varsExpr rhs `thenLne` \ (rhs2, rhs_fvs, rhs_escs) ->
387 returnLne ( StgBindDefault rhs2, rhs_fvs, rhs_escs )
390 Lets not only take quite a bit of work, but this is where we convert
391 then to let-no-escapes, if we wish.
393 (Meanwhile, we don't expect to see let-no-escapes...)
395 varsExpr (StgLetNoEscape _ _ _ _) = panic "varsExpr: unexpected StgLetNoEscape"
397 varsExpr (StgLet bind body)
398 = isSwitchSetLne {-StgDoLetNoEscapes-} `thenLne` \ want_LNEs ->
400 (fixLne (\ ~(_, _, _, no_binder_escapes) ->
402 non_escaping_let = want_LNEs && no_binder_escapes
404 vars_let non_escaping_let bind body
405 )) `thenLne` \ (new_let, fvs, escs, _) ->
407 returnLne (new_let, fvs, escs)
410 If we've got a case containing a _ccall_GC_ primop, we need to
411 ensure that the arguments are kept live for the duration of the
412 call. This only an issue
415 findLiveArgs :: StgLiveVars -> StgArg -> StgLiveVars
416 findLiveArgs lvs (StgConArg _) = lvs
417 findLiveArgs lvs (StgVarArg x)
418 | isForeignObjTy (idType x) = extendVarSet lvs x
425 varsApp :: Maybe UpdateFlag -- Just upd <=> this application is
426 -- the rhs of a thunk binding
427 -- x = [...] \upd [] -> the_app
428 -- with specified update flag
430 -> [StgArg] -- Arguments
431 -> LneM (StgExpr, FreeVarsInfo, EscVarsSet)
433 varsApp maybe_thunk_body f args
434 = getVarsLiveInCont `thenLne` \ live_in_cont ->
436 varsAtoms args `thenLne` \ (args', args_fvs) ->
438 lookupVarLne f `thenLne` \ (f', how_bound) ->
442 not_letrec_bound = not (isLetrecBound how_bound)
443 f_arity = getIdArity f'
444 fun_fvs = singletonFVInfo f' how_bound fun_occ
448 = NoStgBinderInfo -- Uninteresting variable
450 | otherwise -- Letrec bound; must have its arity
453 | n_args == 0 -> stgFakeFunAppOcc -- Function Application
454 -- with no arguments.
455 -- used by the lambda lifter.
456 | arity > n_args -> stgUnsatOcc -- Unsaturated
460 maybeToBool maybe_thunk_body -> -- Exactly saturated,
462 case maybe_thunk_body of
463 Just Updatable -> stgStdHeapOcc
464 Just SingleEntry -> stgNoUpdHeapOcc
465 other -> panic "varsApp"
467 | otherwise -> stgNormalOcc
468 -- Record only that it occurs free
470 myself = unitVarSet f'
472 fun_escs | not_letrec_bound = emptyVarSet -- Only letrec-bound escapees are interesting
473 | otherwise = case f_arity of -- Letrec bound, so must have its arity
475 | arity == n_args -> emptyVarSet
476 -- Function doesn't escape
477 | otherwise -> myself
478 -- Inexact application; it does escape
480 -- At the moment of the call:
482 -- either the function is *not* let-no-escaped, in which case
483 -- nothing is live except live_in_cont
484 -- or the function *is* let-no-escaped in which case the
485 -- variables it uses are live, but still the function
486 -- itself is not. PS. In this case, the function's
487 -- live vars should already include those of the
488 -- continuation, but it does no harm to just union the
493 -- = live_in_cont `unionVarSet` case how_bound of
494 -- LetrecBound _ lvs -> lvs `minusVarSet` myself
495 -- other -> emptyVarSet
499 fun_fvs `unionFVInfo` args_fvs,
500 fun_escs `unionVarSet` (getFVSet args_fvs)
501 -- All the free vars of the args are disqualified
502 -- from being let-no-escaped.
508 vars_let :: Bool -- True <=> yes, we are let-no-escaping this let
509 -> StgBinding -- bindings
511 -> LneM (StgExpr, -- new let
512 FreeVarsInfo, -- variables free in the whole let
513 EscVarsSet, -- variables that escape from the whole let
514 Bool) -- True <=> none of the binders in the bindings
515 -- is among the escaping vars
517 vars_let let_no_escape bind body
518 = fixLne (\ ~(_, _, _, rec_bind_lvs, _, rec_body_fvs, _, _) ->
520 -- Do the bindings, setting live_in_cont to empty if
521 -- we ain't in a let-no-escape world
522 getVarsLiveInCont `thenLne` \ live_in_cont ->
524 (if let_no_escape then live_in_cont else emptyVarSet)
525 (vars_bind rec_bind_lvs rec_body_fvs bind)
526 `thenLne` \ (bind2, bind_fvs, bind_escs, env_ext) ->
528 -- The live variables of this binding are the ones which are live
529 -- by virtue of being accessible via the free vars of the binding (lvs_from_fvs)
530 -- together with the live_in_cont ones
531 lookupLiveVarsForSet (bind_fvs `minusFVBinders` binders) `thenLne` \ lvs_from_fvs ->
533 bind_lvs = lvs_from_fvs `unionVarSet` live_in_cont
536 -- bind_fvs and bind_escs still include the binders of the let(rec)
537 -- but bind_lvs does not
540 extendVarEnvLne env_ext (
541 varsExpr body `thenLne` \ (body2, body_fvs, body_escs) ->
542 lookupLiveVarsForSet body_fvs `thenLne` \ body_lvs ->
544 returnLne (bind2, bind_fvs, bind_escs, bind_lvs,
545 body2, body_fvs, body_escs, body_lvs)
547 )) `thenLne` (\ (bind2, bind_fvs, bind_escs, bind_lvs,
548 body2, body_fvs, body_escs, body_lvs) ->
551 -- Compute the new let-expression
553 new_let = if let_no_escape then
554 -- trace "StgLetNoEscape!" (
555 StgLetNoEscape live_in_whole_let bind_lvs bind2 body2
561 = (bind_fvs `unionFVInfo` body_fvs) `minusFVBinders` binders
564 = bind_lvs `unionVarSet` (body_lvs `minusVarSet` set_of_binders)
566 real_bind_escs = if let_no_escape then
570 -- Everything escapes which is free in the bindings
572 let_escs = (real_bind_escs `unionVarSet` body_escs) `minusVarSet` set_of_binders
574 all_escs = bind_escs `unionVarSet` body_escs -- Still includes binders of
577 no_binder_escapes = isEmptyVarSet (set_of_binders `intersectVarSet` all_escs)
578 -- Mustn't depend on the passed-in let_no_escape flag, since
579 -- no_binder_escapes is used by the caller to derive the flag!
588 set_of_binders = mkVarSet binders
589 binders = case bind of
590 StgNonRec binder rhs -> [binder]
591 StgRec pairs -> map fst pairs
593 mk_binding bind_lvs (binder,rhs)
594 = (binder `setIdArity` ArityExactly (stgArity rhs),
595 LetrecBound False -- Not top level
599 live_vars = if let_no_escape then
600 extendVarSet bind_lvs binder
604 vars_bind :: StgLiveVars
605 -> FreeVarsInfo -- Free var info for body of binding
608 FreeVarsInfo, EscVarsSet, -- free vars; escapee vars
610 -- extension to environment
612 vars_bind rec_bind_lvs rec_body_fvs (StgNonRec binder rhs)
613 = varsRhs rec_body_fvs (binder,rhs) `thenLne` \ (rhs2, fvs, escs) ->
615 env_ext_item@(binder', _) = mk_binding rec_bind_lvs (binder,rhs)
617 returnLne (StgNonRec binder' rhs2, fvs, escs, [env_ext_item])
619 vars_bind rec_bind_lvs rec_body_fvs (StgRec pairs)
621 env_ext = map (mk_binding rec_bind_lvs) pairs
622 binders' = map fst env_ext
624 extendVarEnvLne env_ext (
625 fixLne (\ ~(_, rec_rhs_fvs, _, _) ->
627 rec_scope_fvs = unionFVInfo rec_body_fvs rec_rhs_fvs
629 mapAndUnzip3Lne (varsRhs rec_scope_fvs) pairs `thenLne` \ (rhss2, fvss, escss) ->
631 fvs = unionFVInfos fvss
632 escs = unionVarSets escss
634 returnLne (StgRec (binders' `zip` rhss2), fvs, escs, env_ext)
638 %************************************************************************
640 \subsection[LNE-monad]{A little monad for this let-no-escaping pass}
642 %************************************************************************
644 There's a lot of stuff to pass around, so we use this @LneM@ monad to
645 help. All the stuff here is only passed {\em down}.
648 type LneM a = Bool -- True <=> do let-no-escapes
649 -> IdEnv (Id, HowBound) -- Use the Id at all occurrences; it has correct
650 -- arity information inside it.
651 -> StgLiveVars -- vars live in continuation
659 Bool -- True <=> bound at top level
660 StgLiveVars -- Live vars... see notes below
662 isLetrecBound (LetrecBound _ _) = True
663 isLetrecBound other = False
666 For a let(rec)-bound variable, x, we record what varibles are live if
667 x is live. For "normal" variables that is just x alone. If x is
668 a let-no-escaped variable then x is represented by a code pointer and
669 a stack pointer (well, one for each stack). So all of the variables
670 needed in the execution of x are live if x is, and are therefore recorded
671 in the LetrecBound constructor; x itself *is* included.
673 The std monad functions:
675 initLne :: Bool -> LneM a -> a
676 initLne want_LNEs m = m want_LNEs emptyVarEnv emptyVarSet
678 {-# INLINE thenLne #-}
679 {-# INLINE thenLne_ #-}
680 {-# INLINE returnLne #-}
682 returnLne :: a -> LneM a
683 returnLne e sw env lvs_cont = e
685 thenLne :: LneM a -> (a -> LneM b) -> LneM b
686 thenLne m k sw env lvs_cont
687 = case (m sw env lvs_cont) of
688 m_result -> k m_result sw env lvs_cont
690 thenLne_ :: LneM a -> LneM b -> LneM b
691 thenLne_ m k sw env lvs_cont
692 = case (m sw env lvs_cont) of
693 _ -> k sw env lvs_cont
695 mapLne :: (a -> LneM b) -> [a] -> LneM [b]
696 mapLne f [] = returnLne []
698 = f x `thenLne` \ r ->
699 mapLne f xs `thenLne` \ rs ->
702 mapAndUnzipLne :: (a -> LneM (b,c)) -> [a] -> LneM ([b],[c])
704 mapAndUnzipLne f [] = returnLne ([],[])
705 mapAndUnzipLne f (x:xs)
706 = f x `thenLne` \ (r1, r2) ->
707 mapAndUnzipLne f xs `thenLne` \ (rs1, rs2) ->
708 returnLne (r1:rs1, r2:rs2)
710 mapAndUnzip3Lne :: (a -> LneM (b,c,d)) -> [a] -> LneM ([b],[c],[d])
712 mapAndUnzip3Lne f [] = returnLne ([],[],[])
713 mapAndUnzip3Lne f (x:xs)
714 = f x `thenLne` \ (r1, r2, r3) ->
715 mapAndUnzip3Lne f xs `thenLne` \ (rs1, rs2, rs3) ->
716 returnLne (r1:rs1, r2:rs2, r3:rs3)
718 fixLne :: (a -> LneM a) -> LneM a
719 fixLne expr sw env lvs_cont = result
721 result = expr result sw env lvs_cont
722 -- ^^^^^^ ------ ^^^^^^
725 Functions specific to this monad:
727 isSwitchSetLne :: LneM Bool
728 isSwitchSetLne want_LNEs env lvs_cont
731 getVarsLiveInCont :: LneM StgLiveVars
732 getVarsLiveInCont sw env lvs_cont = lvs_cont
734 setVarsLiveInCont :: StgLiveVars -> LneM a -> LneM a
735 setVarsLiveInCont new_lvs_cont expr sw env lvs_cont
736 = expr sw env new_lvs_cont
738 extendVarEnvLne :: [(Id, HowBound)] -> LneM a -> LneM a
739 extendVarEnvLne ids_w_howbound expr sw env lvs_cont
740 = expr sw (extendVarEnvList env [(id, pair) | pair@(id,_) <- ids_w_howbound]) lvs_cont
743 lookupVarLne :: Id -> LneM (Id, HowBound)
744 lookupVarLne v sw env lvs_cont
746 case (lookupVarEnv env v) of
748 Nothing -> --false:ASSERT(not (isLocallyDefined v))
752 -- The result of lookupLiveVarsForSet, a set of live variables, is
753 -- only ever tacked onto a decorated expression. It is never used as
754 -- the basis of a control decision, which might give a black hole.
756 lookupLiveVarsForSet :: FreeVarsInfo -> LneM StgLiveVars
758 lookupLiveVarsForSet fvs sw env lvs_cont
759 = returnLne (unionVarSets (map do_one (getFVs fvs)))
763 = if isLocallyDefined v then
764 case (lookupVarEnv env v) of
765 Just (_, LetrecBound _ lvs) -> extendVarSet lvs v
766 Just _ -> unitVarSet v
767 Nothing -> pprPanic "lookupVarEnv/do_one:" (ppr v)
773 %************************************************************************
775 \subsection[Free-var info]{Free variable information}
777 %************************************************************************
780 type FreeVarsInfo = IdEnv (Id, Bool, StgBinderInfo)
781 -- If f is mapped to NoStgBinderInfo, that means
782 -- that f *is* mentioned (else it wouldn't be in the
783 -- IdEnv at all), but only in a saturated applications.
785 -- All case/lambda-bound things are also mapped to
786 -- NoStgBinderInfo, since we aren't interested in their
789 -- The Bool is True <=> the Id is top level letrec bound
791 type EscVarsSet = IdSet
795 emptyFVInfo :: FreeVarsInfo
796 emptyFVInfo = emptyVarEnv
798 singletonFVInfo :: Id -> HowBound -> StgBinderInfo -> FreeVarsInfo
799 singletonFVInfo id ImportBound info = emptyVarEnv
800 singletonFVInfo id (LetrecBound top_level _) info = unitVarEnv id (id, top_level, info)
801 singletonFVInfo id other info = unitVarEnv id (id, False, info)
803 unionFVInfo :: FreeVarsInfo -> FreeVarsInfo -> FreeVarsInfo
804 unionFVInfo fv1 fv2 = plusVarEnv_C plusFVInfo fv1 fv2
806 unionFVInfos :: [FreeVarsInfo] -> FreeVarsInfo
807 unionFVInfos fvs = foldr unionFVInfo emptyFVInfo fvs
809 minusFVBinders :: FreeVarsInfo -> [Id] -> FreeVarsInfo
810 minusFVBinders fv ids = fv `delVarEnvList` ids
812 elementOfFVInfo :: Id -> FreeVarsInfo -> Bool
813 elementOfFVInfo id fvs = maybeToBool (lookupVarEnv fvs id)
815 lookupFVInfo :: FreeVarsInfo -> Id -> StgBinderInfo
816 lookupFVInfo fvs id = case lookupVarEnv fvs id of
817 Nothing -> NoStgBinderInfo
818 Just (_,_,info) -> info
820 getFVs :: FreeVarsInfo -> [Id] -- Non-top-level things only
821 getFVs fvs = [id | (id,False,_) <- rngVarEnv fvs]
823 getFVSet :: FreeVarsInfo -> IdSet
824 getFVSet fvs = mkVarSet (getFVs fvs)
826 plusFVInfo (id1,top1,info1) (id2,top2,info2)
827 = ASSERT (id1 == id2 && top1 == top2)
828 (id1, top1, combineStgBinderInfo info1 info2)
832 rhsArity :: StgRhs -> Arity
833 rhsArity (StgRhsCon _ _ _) = 0
834 rhsArity (StgRhsClosure _ _ _ _ _ args _) = length args
837 zapArity id = id `setIdArity` UnknownArity