2 % (c) The GRASP/AQUA Project, Glasgow University, 1993-1998
4 \section[CoreToStg]{Converts Core to STG Syntax}
6 And, as we have the info in hand, we may convert some lets to
10 module CoreToStg ( coreToStg, coreExprToStg ) where
12 #include "HsVersions.h"
19 import TyCon ( isAlgTyCon )
22 import Var ( Var, globalIdDetails )
25 import CostCentre ( noCCS )
28 import DataCon ( dataConWrapId )
29 import IdInfo ( OccInfo(..) )
30 import Maybes ( maybeToBool )
31 import Name ( getOccName, isExternallyVisibleName, isDllName )
32 import OccName ( occNameUserString )
33 import BasicTypes ( TopLevelFlag(..), isNotTopLevel, Arity )
34 import CmdLineOpts ( DynFlags, opt_KeepStgTypes )
35 import FastTypes hiding ( fastOr )
38 import List ( partition )
43 %************************************************************************
45 \subsection[live-vs-free-doc]{Documentation}
47 %************************************************************************
49 (There is other relevant documentation in codeGen/CgLetNoEscape.)
51 The actual Stg datatype is decorated with {\em live variable}
52 information, as well as {\em free variable} information. The two are
53 {\em not} the same. Liveness is an operational property rather than a
54 semantic one. A variable is live at a particular execution point if
55 it can be referred to {\em directly} again. In particular, a dead
56 variable's stack slot (if it has one):
59 should be stubbed to avoid space leaks, and
61 may be reused for something else.
64 There ought to be a better way to say this. Here are some examples:
71 Just after the `in', v is live, but q is dead. If the whole of that
72 let expression was enclosed in a case expression, thus:
74 case (let v = [q] \[x] -> e in ...v...) of
77 (ie @alts@ mention @q@), then @q@ is live even after the `in'; because
78 we'll return later to the @alts@ and need it.
80 Let-no-escapes make this a bit more interesting:
82 let-no-escape v = [q] \ [x] -> e
86 Here, @q@ is still live at the `in', because @v@ is represented not by
87 a closure but by the current stack state. In other words, if @v@ is
88 live then so is @q@. Furthermore, if @e@ mentions an enclosing
89 let-no-escaped variable, then {\em its} free variables are also live
92 %************************************************************************
94 \subsection[caf-info]{Collecting live CAF info}
96 %************************************************************************
98 In this pass we also collect information on which CAFs are live for
99 constructing SRTs (see SRT.lhs).
101 A top-level Id has CafInfo, which is
103 - MayHaveCafRefs, if it may refer indirectly to
105 - NoCafRefs if it definitely doesn't
107 we collect the CafInfo first by analysing the original Core expression, and
108 also place this information in the environment.
110 During CoreToStg, we then pin onto each binding and case expression, a
111 list of Ids which represents the "live" CAFs at that point. The meaning
112 of "live" here is the same as for live variables, see above (which is
113 why it's convenient to collect CAF information here rather than elsewhere).
115 The later SRT pass takes these lists of Ids and uses them to construct
116 the actual nested SRTs, and replaces the lists of Ids with (offset,length)
119 %************************************************************************
121 \subsection[binds-StgVarInfo]{Setting variable info: top-level, binds, RHSs}
123 %************************************************************************
126 coreToStg :: DynFlags -> [CoreBind] -> IO [StgBinding]
129 where (_, _, pgm') = coreTopBindsToStg emptyVarEnv pgm
131 coreExprToStg :: CoreExpr -> StgExpr
133 = new_expr where (new_expr,_,_) = initLne emptyVarEnv (coreToStgExpr expr)
137 :: IdEnv HowBound -- environment for the bindings
139 -> (IdEnv HowBound, FreeVarsInfo, [StgBinding])
141 coreTopBindsToStg env [] = (env, emptyFVInfo, [])
142 coreTopBindsToStg env (b:bs)
143 = (env2, fvs2, b':bs')
145 -- env accumulates down the list of binds, fvs accumulates upwards
146 (env1, fvs2, b' ) = coreTopBindToStg env fvs1 b
147 (env2, fvs1, bs') = coreTopBindsToStg env1 bs
152 -> FreeVarsInfo -- Info about the body
154 -> (IdEnv HowBound, FreeVarsInfo, StgBinding)
156 coreTopBindToStg env body_fvs (NonRec id rhs)
158 caf_info = hasCafRefs env rhs
160 env' = extendVarEnv env id (LetBound how_bound emptyLVS (predictArity rhs))
162 how_bound | mayHaveCafRefs caf_info = TopLevelHasCafs
163 | otherwise = TopLevelNoCafs
165 (stg_rhs, fvs', cafs) =
167 coreToStgRhs body_fvs TopLevel (id,rhs)
168 `thenLne` \ (stg_rhs, fvs', _) ->
169 freeVarsToLiveVars fvs' `thenLne` \ (_, cafs) ->
170 returnLne (stg_rhs, fvs', cafs)
173 bind = StgNonRec (SRTEntries cafs) id stg_rhs
175 ASSERT2(predictArity rhs == stgRhsArity stg_rhs, ppr id)
176 ASSERT2(consistent caf_info bind, ppr id)
177 -- WARN(not (consistent caf_info bind), ppr id <+> ppr cafs <+> ppCafInfo caf_info)
178 (env', fvs' `unionFVInfo` body_fvs, bind)
180 coreTopBindToStg env body_fvs (Rec pairs)
182 (binders, rhss) = unzip pairs
184 -- to calculate caf_info, we initially map all the binders to
186 env1 = extendVarEnvList env
187 [ (b, LetBound TopLevelNoCafs emptyLVS (error "no arity"))
190 caf_info = hasCafRefss env1{-NB: not env'-} rhss
192 env' = extendVarEnvList env
193 [ (b, LetBound how_bound emptyLVS (predictArity rhs))
196 how_bound | mayHaveCafRefs caf_info = TopLevelHasCafs
197 | otherwise = TopLevelNoCafs
199 (stg_rhss, fvs', cafs)
201 mapAndUnzip3Lne (coreToStgRhs body_fvs TopLevel) pairs
202 `thenLne` \ (stg_rhss, fvss', _) ->
203 let fvs' = unionFVInfos fvss' in
204 freeVarsToLiveVars fvs' `thenLne` \ (_, cafs) ->
205 returnLne (stg_rhss, fvs', cafs)
208 bind = StgRec (SRTEntries cafs) (zip binders stg_rhss)
210 ASSERT2(and [predictArity rhs == stgRhsArity stg_rhs | (rhs,stg_rhs) <- rhss `zip` stg_rhss], ppr binders)
211 ASSERT2(consistent caf_info bind, ppr binders)
212 -- WARN(not (consistent caf_info bind), ppr binders <+> ppr cafs <+> ppCafInfo caf_info)
213 (env', fvs' `unionFVInfo` body_fvs, bind)
216 consistent caf_info bind = mayHaveCafRefs caf_info == stgBindHasCafRefs bind
221 :: FreeVarsInfo -- Free var info for the scope of the binding
224 -> LneM (StgRhs, FreeVarsInfo, EscVarsSet)
226 coreToStgRhs scope_fv_info top (binder, rhs)
227 = coreToStgExpr rhs `thenLne` \ (new_rhs, rhs_fvs, rhs_escs) ->
228 returnLne (mkStgRhs top rhs_fvs binder_info new_rhs,
231 binder_info = lookupFVInfo scope_fv_info binder
233 mkStgRhs :: TopLevelFlag -> FreeVarsInfo -> StgBinderInfo
236 mkStgRhs top rhs_fvs binder_info (StgLam _ bndrs body)
237 = StgRhsClosure noCCS binder_info
242 mkStgRhs top rhs_fvs binder_info (StgConApp con args)
243 | isNotTopLevel top || not (isDllConApp con args)
244 = StgRhsCon noCCS con args
246 mkStgRhs top rhs_fvs binder_info rhs
247 = StgRhsClosure noCCS binder_info
252 updatable args body | null args && isPAP body = ReEntrant
253 | otherwise = Updatable
255 upd = if isOnceDem dem
256 then (if isNotTop toplev
257 then SingleEntry -- HA! Paydirt for "dem"
260 trace "WARNING: SE CAFs unsupported, forcing UPD instead" $
264 -- For now we forbid SingleEntry CAFs; they tickle the
265 -- ASSERT in rts/Storage.c line 215 at newCAF() re mut_link,
266 -- and I don't understand why. There's only one SE_CAF (well,
267 -- only one that tickled a great gaping bug in an earlier attempt
268 -- at ClosureInfo.getEntryConvention) in the whole of nofib,
269 -- specifically Main.lvl6 in spectral/cryptarithm2.
270 -- So no great loss. KSW 2000-07.
274 Detect thunks which will reduce immediately to PAPs, and make them
275 non-updatable. This has several advantages:
277 - the non-updatable thunk behaves exactly like the PAP,
279 - the thunk is more efficient to enter, because it is
280 specialised to the task.
282 - we save one update frame, one stg_update_PAP, one update
283 and lots of PAP_enters.
285 - in the case where the thunk is top-level, we save building
286 a black hole and futhermore the thunk isn't considered to
287 be a CAF any more, so it doesn't appear in any SRTs.
289 We do it here, because the arity information is accurate, and we need
290 to do it before the SRT pass to save the SRT entries associated with
294 isPAP (StgApp f args) = idArity f > length args
299 -- ---------------------------------------------------------------------------
301 -- ---------------------------------------------------------------------------
306 -> LneM (StgExpr, -- Decorated STG expr
307 FreeVarsInfo, -- Its free vars (NB free, not live)
308 EscVarsSet) -- Its escapees, a subset of its free vars;
309 -- also a subset of the domain of the envt
310 -- because we are only interested in the escapees
311 -- for vars which might be turned into
312 -- let-no-escaped ones.
315 The second and third components can be derived in a simple bottom up pass, not
316 dependent on any decisions about which variables will be let-no-escaped or
317 not. The first component, that is, the decorated expression, may then depend
318 on these components, but it in turn is not scrutinised as the basis for any
319 decisions. Hence no black holes.
322 coreToStgExpr (Lit l) = returnLne (StgLit l, emptyFVInfo, emptyVarSet)
323 coreToStgExpr (Var v) = coreToStgApp Nothing v []
325 coreToStgExpr expr@(App _ _)
326 = coreToStgApp Nothing f args
328 (f, args) = myCollectArgs expr
330 coreToStgExpr expr@(Lam _ _)
331 = let (args, body) = myCollectBinders expr
332 args' = filterStgBinders args
334 extendVarEnvLne [ (a, LambdaBound) | a <- args' ] $
335 coreToStgExpr body `thenLne` \ (body, body_fvs, body_escs) ->
337 set_of_args = mkVarSet args'
338 fvs = args' `minusFVBinders` body_fvs
339 escs = body_escs `minusVarSet` set_of_args
340 result_expr | null args' = body
341 | otherwise = StgLam (exprType expr) args' body
343 returnLne (result_expr, fvs, escs)
345 coreToStgExpr (Note (SCC cc) expr)
346 = coreToStgExpr expr `thenLne` ( \ (expr2, fvs, escs) ->
347 returnLne (StgSCC cc expr2, fvs, escs) )
349 coreToStgExpr (Note other_note expr)
353 -- Cases require a little more real work.
355 coreToStgExpr (Case scrut bndr alts)
356 = extendVarEnvLne [(bndr, CaseBound)] $
357 vars_alts (findDefault alts) `thenLne` \ (alts2, alts_fvs, alts_escs) ->
358 freeVarsToLiveVars alts_fvs `thenLne` \ (alts_lvs, alts_caf_refs) ->
360 -- determine whether the default binder is dead or not
361 -- This helps the code generator to avoid generating an assignment
362 -- for the case binder (is extremely rare cases) ToDo: remove.
363 bndr'= if (bndr `elementOfFVInfo` alts_fvs)
365 else bndr `setIdOccInfo` IAmDead
367 -- Don't consider the default binder as being 'live in alts',
368 -- since this is from the point of view of the case expr, where
369 -- the default binder is not free.
370 live_in_alts = (alts_lvs `minusVarSet` unitVarSet bndr)
372 -- we tell the scrutinee that everything live in the alts
373 -- is live in it, too.
374 setVarsLiveInCont (live_in_alts,alts_caf_refs) (
375 coreToStgExpr scrut `thenLne` \ (scrut2, scrut_fvs, scrut_escs) ->
376 freeVarsToLiveVars scrut_fvs `thenLne` \ (scrut_lvs, _) ->
377 returnLne (scrut2, scrut_fvs, scrut_escs, scrut_lvs)
379 `thenLne` \ (scrut2, scrut_fvs, scrut_escs, scrut_lvs) ->
381 let srt = SRTEntries alts_caf_refs
384 StgCase scrut2 scrut_lvs live_in_alts bndr' srt alts2,
385 bndr `minusFVBinder` (scrut_fvs `unionFVInfo` alts_fvs),
386 (alts_escs `minusVarSet` unitVarSet bndr) `unionVarSet` getFVSet scrut_fvs
387 -- You might think we should have scrut_escs, not
388 -- (getFVSet scrut_fvs), but actually we can't call, and
389 -- then return from, a let-no-escape thing.
392 scrut_ty = idType bndr
393 prim_case = isUnLiftedType scrut_ty && not (isUnboxedTupleType scrut_ty)
395 vars_alts (alts,deflt)
397 = mapAndUnzip3Lne vars_prim_alt alts
398 `thenLne` \ (alts2, alts_fvs_list, alts_escs_list) ->
400 alts_fvs = unionFVInfos alts_fvs_list
401 alts_escs = unionVarSets alts_escs_list
403 vars_deflt deflt `thenLne` \ (deflt2, deflt_fvs, deflt_escs) ->
405 mkStgPrimAlts scrut_ty alts2 deflt2,
406 alts_fvs `unionFVInfo` deflt_fvs,
407 alts_escs `unionVarSet` deflt_escs
411 = mapAndUnzip3Lne vars_alg_alt alts
412 `thenLne` \ (alts2, alts_fvs_list, alts_escs_list) ->
414 alts_fvs = unionFVInfos alts_fvs_list
415 alts_escs = unionVarSets alts_escs_list
417 vars_deflt deflt `thenLne` \ (deflt2, deflt_fvs, deflt_escs) ->
419 mkStgAlgAlts scrut_ty alts2 deflt2,
420 alts_fvs `unionFVInfo` deflt_fvs,
421 alts_escs `unionVarSet` deflt_escs
425 vars_prim_alt (LitAlt lit, _, rhs)
426 = coreToStgExpr rhs `thenLne` \ (rhs2, rhs_fvs, rhs_escs) ->
427 returnLne ((lit, rhs2), rhs_fvs, rhs_escs)
429 vars_alg_alt (DataAlt con, binders, rhs)
431 -- remove type variables
432 binders' = filterStgBinders binders
434 extendVarEnvLne [(b, CaseBound) | b <- binders'] $
435 coreToStgExpr rhs `thenLne` \ (rhs2, rhs_fvs, rhs_escs) ->
437 good_use_mask = [ b `elementOfFVInfo` rhs_fvs | b <- binders' ]
438 -- records whether each param is used in the RHS
441 (con, binders', good_use_mask, rhs2),
442 binders' `minusFVBinders` rhs_fvs,
443 rhs_escs `minusVarSet` mkVarSet binders'
444 -- ToDo: remove the minusVarSet;
445 -- since escs won't include any of these binders
447 vars_alg_alt other = pprPanic "vars_alg_alt" (ppr other)
450 = returnLne (StgNoDefault, emptyFVInfo, emptyVarSet)
452 vars_deflt (Just rhs)
453 = coreToStgExpr rhs `thenLne` \ (rhs2, rhs_fvs, rhs_escs) ->
454 returnLne (StgBindDefault rhs2, rhs_fvs, rhs_escs)
457 Lets not only take quite a bit of work, but this is where we convert
458 then to let-no-escapes, if we wish.
460 (Meanwhile, we don't expect to see let-no-escapes...)
462 coreToStgExpr (Let bind body)
463 = fixLne (\ ~(_, _, _, no_binder_escapes) ->
464 coreToStgLet no_binder_escapes bind body
465 ) `thenLne` \ (new_let, fvs, escs, _) ->
467 returnLne (new_let, fvs, escs)
471 mkStgAlgAlts ty alts deflt
473 -- Get the tycon from the data con
474 (dc, _, _, _) : _rest
475 -> StgAlgAlts (Just (dataConTyCon dc)) alts deflt
477 -- Otherwise just do your best
478 [] -> case splitTyConApp_maybe (repType ty) of
479 Just (tc,_) | isAlgTyCon tc
480 -> StgAlgAlts (Just tc) alts deflt
482 -> StgAlgAlts Nothing alts deflt
484 mkStgPrimAlts ty alts deflt
485 = StgPrimAlts (tyConAppTyCon ty) alts deflt
489 -- ---------------------------------------------------------------------------
491 -- ---------------------------------------------------------------------------
495 :: Maybe UpdateFlag -- Just upd <=> this application is
496 -- the rhs of a thunk binding
497 -- x = [...] \upd [] -> the_app
498 -- with specified update flag
500 -> [CoreArg] -- Arguments
501 -> LneM (StgExpr, FreeVarsInfo, EscVarsSet)
503 coreToStgApp maybe_thunk_body f args
504 = coreToStgArgs args `thenLne` \ (args', args_fvs) ->
505 lookupVarLne f `thenLne` \ how_bound ->
508 n_val_args = valArgCount args
509 not_letrec_bound = not (isLetBound how_bound)
510 fun_fvs = singletonFVInfo f how_bound fun_occ
512 f_arity = case how_bound of
513 LetBound _ _ arity -> arity
517 | not_letrec_bound = noBinderInfo -- Uninteresting variable
518 | f_arity > 0 && f_arity <= n_val_args = stgSatOcc -- Saturated or over-saturated function call
519 | otherwise = stgUnsatOcc -- Unsaturated function or thunk
522 | not_letrec_bound = emptyVarSet -- Only letrec-bound escapees are interesting
523 | f_arity == n_val_args = emptyVarSet -- A function *or thunk* with an exactly
524 -- saturated call doesn't escape
525 -- (let-no-escape applies to 'thunks' too)
527 | otherwise = unitVarSet f -- Inexact application; it does escape
529 -- At the moment of the call:
531 -- either the function is *not* let-no-escaped, in which case
532 -- nothing is live except live_in_cont
533 -- or the function *is* let-no-escaped in which case the
534 -- variables it uses are live, but still the function
535 -- itself is not. PS. In this case, the function's
536 -- live vars should already include those of the
537 -- continuation, but it does no harm to just union the
540 res_ty = exprType (mkApps (Var f) args)
541 app = case globalIdDetails f of
542 DataConId dc -> StgConApp dc args'
543 PrimOpId op -> StgOpApp (StgPrimOp op) args' res_ty
544 FCallId call -> StgOpApp (StgFCallOp call (idUnique f)) args' res_ty
545 _other -> StgApp f args'
550 fun_fvs `unionFVInfo` args_fvs,
551 fun_escs `unionVarSet` (getFVSet args_fvs)
552 -- All the free vars of the args are disqualified
553 -- from being let-no-escaped.
558 -- ---------------------------------------------------------------------------
560 -- This is the guy that turns applications into A-normal form
561 -- ---------------------------------------------------------------------------
563 coreToStgArgs :: [CoreArg] -> LneM ([StgArg], FreeVarsInfo)
565 = returnLne ([], emptyFVInfo)
567 coreToStgArgs (Type ty : args) -- Type argument
568 = coreToStgArgs args `thenLne` \ (args', fvs) ->
569 if opt_KeepStgTypes then
570 returnLne (StgTypeArg ty : args', fvs `unionFVInfo` tyvarFVInfo (tyVarsOfType ty))
572 returnLne (args', fvs)
574 coreToStgArgs (arg : args) -- Non-type argument
575 = coreToStgArgs args `thenLne` \ (stg_args, args_fvs) ->
576 coreToStgExpr arg `thenLne` \ (arg', arg_fvs, escs) ->
578 fvs = args_fvs `unionFVInfo` arg_fvs
579 stg_arg = case arg' of
580 StgApp v [] -> StgVarArg v
581 StgConApp con [] -> StgVarArg (dataConWrapId con)
582 StgLit lit -> StgLitArg lit
583 _ -> pprPanic "coreToStgArgs" (ppr arg)
585 returnLne (stg_arg : stg_args, fvs)
588 -- ---------------------------------------------------------------------------
589 -- The magic for lets:
590 -- ---------------------------------------------------------------------------
593 :: Bool -- True <=> yes, we are let-no-escaping this let
594 -> CoreBind -- bindings
596 -> LneM (StgExpr, -- new let
597 FreeVarsInfo, -- variables free in the whole let
598 EscVarsSet, -- variables that escape from the whole let
599 Bool) -- True <=> none of the binders in the bindings
600 -- is among the escaping vars
602 coreToStgLet let_no_escape bind body
603 = fixLne (\ ~(_, _, _, _, _, _, rec_body_fvs, _, _) ->
605 -- Do the bindings, setting live_in_cont to empty if
606 -- we ain't in a let-no-escape world
607 getVarsLiveInCont `thenLne` \ live_in_cont ->
608 setVarsLiveInCont (if let_no_escape
611 (vars_bind rec_body_fvs bind)
612 `thenLne` \ ( bind2, bind_fvs, bind_escs
613 , bind_lvs, bind_cafs, env_ext) ->
616 extendVarEnvLne env_ext (
617 coreToStgExpr body `thenLne` \(body2, body_fvs, body_escs) ->
618 freeVarsToLiveVars body_fvs `thenLne` \(body_lvs, _) ->
620 returnLne (bind2, bind_fvs, bind_escs, bind_lvs, bind_cafs,
621 body2, body_fvs, body_escs, body_lvs)
624 ) `thenLne` (\ (bind2, bind_fvs, bind_escs, bind_lvs, bind_cafs,
625 body2, body_fvs, body_escs, body_lvs) ->
628 -- Compute the new let-expression
630 new_let | let_no_escape = StgLetNoEscape live_in_whole_let bind_lvs bind2 body2
631 | otherwise = StgLet bind2 body2
634 = binders `minusFVBinders` (bind_fvs `unionFVInfo` body_fvs)
637 = bind_lvs `unionVarSet` (body_lvs `minusVarSet` set_of_binders)
639 real_bind_escs = if let_no_escape then
643 -- Everything escapes which is free in the bindings
645 let_escs = (real_bind_escs `unionVarSet` body_escs) `minusVarSet` set_of_binders
647 all_escs = bind_escs `unionVarSet` body_escs -- Still includes binders of
650 no_binder_escapes = isEmptyVarSet (set_of_binders `intersectVarSet` all_escs)
653 -- Debugging code as requested by Andrew Kennedy
654 checked_no_binder_escapes
655 | not no_binder_escapes && any is_join_var binders
656 = pprTrace "Interesting! A join var that isn't let-no-escaped" (ppr binders)
658 | otherwise = no_binder_escapes
660 checked_no_binder_escapes = no_binder_escapes
663 -- Mustn't depend on the passed-in let_no_escape flag, since
664 -- no_binder_escapes is used by the caller to derive the flag!
670 checked_no_binder_escapes
673 set_of_binders = mkVarSet binders
674 binders = case bind of
675 NonRec binder rhs -> [binder]
676 Rec pairs -> map fst pairs
678 mk_binding bind_lvs bind_cafs binder rhs
679 = (binder, LetBound NotTopLevelBound -- Not top level
680 live_vars (predictArity rhs)
683 live_vars = if let_no_escape then
684 (extendVarSet bind_lvs binder, bind_cafs)
686 (unitVarSet binder, emptyVarSet)
688 vars_bind :: FreeVarsInfo -- Free var info for body of binding
692 EscVarsSet, -- free vars; escapee vars
693 StgLiveVars, -- vars live in binding
694 IdSet, -- CAFs live in binding
695 [(Id, HowBound)]) -- extension to environment
698 vars_bind body_fvs (NonRec binder rhs)
699 = coreToStgRhs body_fvs NotTopLevel (binder,rhs)
700 `thenLne` \ (rhs2, bind_fvs, escs) ->
702 freeVarsToLiveVars bind_fvs `thenLne` \ (bind_lvs, bind_cafs) ->
704 env_ext_item = mk_binding bind_lvs bind_cafs binder rhs
706 returnLne (StgNonRec (SRTEntries bind_cafs) binder rhs2,
707 bind_fvs, escs, bind_lvs, bind_cafs, [env_ext_item])
710 vars_bind body_fvs (Rec pairs)
711 = fixLne (\ ~(_, rec_rhs_fvs, _, bind_lvs, bind_cafs, _) ->
713 rec_scope_fvs = unionFVInfo body_fvs rec_rhs_fvs
714 binders = map fst pairs
715 env_ext = [ mk_binding bind_lvs bind_cafs b rhs
718 extendVarEnvLne env_ext (
719 mapAndUnzip3Lne (coreToStgRhs rec_scope_fvs NotTopLevel) pairs
720 `thenLne` \ (rhss2, fvss, escss) ->
722 bind_fvs = unionFVInfos fvss
723 escs = unionVarSets escss
725 freeVarsToLiveVars (binders `minusFVBinders` bind_fvs)
726 `thenLne` \ (bind_lvs, bind_cafs) ->
728 returnLne (StgRec (SRTEntries bind_cafs) (binders `zip` rhss2),
729 bind_fvs, escs, bind_lvs, bind_cafs, env_ext)
733 is_join_var :: Id -> Bool
734 -- A hack (used only for compiler debuggging) to tell if
735 -- a variable started life as a join point ($j)
736 is_join_var j = occNameUserString (getOccName j) == "$j"
739 %************************************************************************
741 \subsection{Arity prediction}
743 %************************************************************************
745 To avoid yet another knot, we predict the arity of each function from
746 its Core form, based on the number of visible top-level lambdas.
747 It should be the same as the arity of the STG RHS!
750 predictArity :: CoreExpr -> Int
751 predictArity (Lam x e)
752 | isTyVar x = predictArity e
753 | otherwise = 1 + predictArity e
754 predictArity (Note _ e)
755 -- Ignore coercions. Top level sccs are removed by the final
756 -- profiling pass, so we ignore those too.
762 %************************************************************************
764 \subsection[LNE-monad]{A little monad for this let-no-escaping pass}
766 %************************************************************************
768 There's a lot of stuff to pass around, so we use this @LneM@ monad to
769 help. All the stuff here is only passed *down*.
772 type LneM a = IdEnv HowBound
773 -> (StgLiveVars, -- vars live in continuation
774 IdSet) -- cafs live in continuation
783 (StgLiveVars, IdSet) -- (Live vars, Live CAFs)... see notes below
784 Arity -- its arity (local Ids don't have arity info at this point)
786 isLetBound (LetBound _ _ _) = True
787 isLetBound other = False
790 For a let(rec)-bound variable, x, we record StgLiveVars, the set of
791 variables that are live if x is live. For "normal" variables that is
792 just x alone. If x is a let-no-escaped variable then x is represented
793 by a code pointer and a stack pointer (well, one for each stack). So
794 all of the variables needed in the execution of x are live if x is,
795 and are therefore recorded in the LetBound constructor; x itself
798 The set of live variables is guaranteed ot have no further let-no-escaped
801 The std monad functions:
803 initLne :: IdEnv HowBound -> LneM a -> a
804 initLne env m = m env emptyLVS
806 emptyLVS = (emptyVarSet,emptyVarSet)
808 {-# INLINE thenLne #-}
809 {-# INLINE returnLne #-}
811 returnLne :: a -> LneM a
812 returnLne e env lvs_cont = e
814 thenLne :: LneM a -> (a -> LneM b) -> LneM b
815 thenLne m k env lvs_cont
816 = k (m env lvs_cont) env lvs_cont
818 mapLne :: (a -> LneM b) -> [a] -> LneM [b]
819 mapLne f [] = returnLne []
821 = f x `thenLne` \ r ->
822 mapLne f xs `thenLne` \ rs ->
825 mapAndUnzipLne :: (a -> LneM (b,c)) -> [a] -> LneM ([b],[c])
827 mapAndUnzipLne f [] = returnLne ([],[])
828 mapAndUnzipLne f (x:xs)
829 = f x `thenLne` \ (r1, r2) ->
830 mapAndUnzipLne f xs `thenLne` \ (rs1, rs2) ->
831 returnLne (r1:rs1, r2:rs2)
833 mapAndUnzip3Lne :: (a -> LneM (b,c,d)) -> [a] -> LneM ([b],[c],[d])
835 mapAndUnzip3Lne f [] = returnLne ([],[],[])
836 mapAndUnzip3Lne f (x:xs)
837 = f x `thenLne` \ (r1, r2, r3) ->
838 mapAndUnzip3Lne f xs `thenLne` \ (rs1, rs2, rs3) ->
839 returnLne (r1:rs1, r2:rs2, r3:rs3)
841 fixLne :: (a -> LneM a) -> LneM a
842 fixLne expr env lvs_cont
845 result = expr result env lvs_cont
848 Functions specific to this monad:
851 getVarsLiveInCont :: LneM (StgLiveVars, IdSet)
852 getVarsLiveInCont env lvs_cont = lvs_cont
854 setVarsLiveInCont :: (StgLiveVars,IdSet) -> LneM a -> LneM a
855 setVarsLiveInCont new_lvs_cont expr env lvs_cont
856 = expr env new_lvs_cont
858 extendVarEnvLne :: [(Id, HowBound)] -> LneM a -> LneM a
859 extendVarEnvLne ids_w_howbound expr env lvs_cont
860 = expr (extendVarEnvList env ids_w_howbound) lvs_cont
862 lookupVarLne :: Id -> LneM HowBound
863 lookupVarLne v env lvs_cont
865 case (lookupVarEnv env v) of
867 Nothing -> ImportBound
870 -- The result of lookupLiveVarsForSet, a set of live variables, is
871 -- only ever tacked onto a decorated expression. It is never used as
872 -- the basis of a control decision, which might give a black hole.
874 freeVarsToLiveVars :: FreeVarsInfo -> LneM (StgLiveVars, IdSet)
875 freeVarsToLiveVars fvs env live_in_cont
876 = returnLne (lvs, cafs) env live_in_cont
878 (lvs_cont, cafs_cont) = live_in_cont -- not a strict pattern match!
879 (local, global) = partition isLocalId (allFVs fvs)
881 (lvs_from_fvs, caf_extras) = unzip (map do_one local)
883 lvs = unionVarSets lvs_from_fvs
884 `unionVarSet` lvs_cont
886 cafs = mkVarSet (filter is_caf_one global)
887 `unionVarSet` (unionVarSets caf_extras)
888 `unionVarSet` cafs_cont
891 = case (lookupVarEnv env v) of
892 Just (LetBound _ (lvs,cafs) _) -> (extendVarSet lvs v, cafs)
893 Just _ -> (unitVarSet v, emptyVarSet)
894 Nothing -> pprPanic "lookupLiveVarsForSet/do_one:" (ppr v)
897 = case lookupVarEnv env v of
898 Just (LetBound TopLevelHasCafs (lvs,_) _) ->
899 ASSERT( isEmptyVarSet lvs ) True
900 Just (LetBound _ _ _) -> False
901 _otherwise -> mayHaveCafRefs (idCafInfo v)
904 %************************************************************************
906 \subsection[Free-var info]{Free variable information}
908 %************************************************************************
911 type FreeVarsInfo = VarEnv (Var, TopLevelCafInfo, StgBinderInfo)
912 -- If f is mapped to noBinderInfo, that means
913 -- that f *is* mentioned (else it wouldn't be in the
914 -- IdEnv at all), but perhaps in an unsaturated applications.
916 -- All case/lambda-bound things are also mapped to
917 -- noBinderInfo, since we aren't interested in their
920 -- For ILX we track free var info for type variables too;
921 -- hence VarEnv not IdEnv
929 type EscVarsSet = IdSet
933 emptyFVInfo :: FreeVarsInfo
934 emptyFVInfo = emptyVarEnv
936 singletonFVInfo :: Id -> HowBound -> StgBinderInfo -> FreeVarsInfo
937 singletonFVInfo id ImportBound info
938 | mayHaveCafRefs (idCafInfo id) = unitVarEnv id (id, TopLevelHasCafs, info)
939 | otherwise = emptyVarEnv
940 singletonFVInfo id (LetBound top_level _ _) info
941 = unitVarEnv id (id, top_level, info)
942 singletonFVInfo id other info
943 = unitVarEnv id (id, NotTopLevelBound, info)
945 tyvarFVInfo :: TyVarSet -> FreeVarsInfo
946 tyvarFVInfo tvs = foldVarSet add emptyFVInfo tvs
948 add tv fvs = extendVarEnv fvs tv (tv, NotTopLevelBound, noBinderInfo)
950 unionFVInfo :: FreeVarsInfo -> FreeVarsInfo -> FreeVarsInfo
951 unionFVInfo fv1 fv2 = plusVarEnv_C plusFVInfo fv1 fv2
953 unionFVInfos :: [FreeVarsInfo] -> FreeVarsInfo
954 unionFVInfos fvs = foldr unionFVInfo emptyFVInfo fvs
956 minusFVBinders :: [Id] -> FreeVarsInfo -> FreeVarsInfo
957 minusFVBinders vs fv = foldr minusFVBinder fv vs
959 minusFVBinder :: Id -> FreeVarsInfo -> FreeVarsInfo
960 minusFVBinder v fv | isId v && opt_KeepStgTypes
961 = (fv `delVarEnv` v) `unionFVInfo`
962 tyvarFVInfo (tyVarsOfType (idType v))
963 | otherwise = fv `delVarEnv` v
964 -- When removing a binder, remember to add its type variables
965 -- c.f. CoreFVs.delBinderFV
967 elementOfFVInfo :: Id -> FreeVarsInfo -> Bool
968 elementOfFVInfo id fvs = maybeToBool (lookupVarEnv fvs id)
970 lookupFVInfo :: FreeVarsInfo -> Id -> StgBinderInfo
971 -- Find how the given Id is used.
972 -- Externally visible things may be used any old how
974 | isExternallyVisibleName (idName id) = noBinderInfo
975 | otherwise = case lookupVarEnv fvs id of
976 Nothing -> noBinderInfo
977 Just (_,_,info) -> info
979 allFVs :: FreeVarsInfo -> [Id] -- Non-top-level things only
980 allFVs fvs = [id | (id,_,_) <- rngVarEnv fvs]
982 getFVs :: FreeVarsInfo -> [Id] -- Non-top-level things only
983 getFVs fvs = [id | (id,NotTopLevelBound,_) <- rngVarEnv fvs]
985 getFVSet :: FreeVarsInfo -> IdSet
986 getFVSet fvs = mkVarSet (getFVs fvs)
988 plusFVInfo (id1,top1,info1) (id2,top2,info2)
989 = ASSERT (id1 == id2 && top1 == top2)
990 (id1, top1, combineStgBinderInfo info1 info2)
995 filterStgBinders :: [Var] -> [Var]
996 filterStgBinders bndrs
997 | opt_KeepStgTypes = bndrs
998 | otherwise = filter isId bndrs
1003 -- Ignore all notes except SCC
1004 myCollectBinders expr
1007 go bs (Lam b e) = go (b:bs) e
1008 go bs e@(Note (SCC _) _) = (reverse bs, e)
1009 go bs (Note _ e) = go bs e
1010 go bs e = (reverse bs, e)
1012 myCollectArgs :: CoreExpr -> (Id, [CoreArg])
1013 -- We assume that we only have variables
1014 -- in the function position by now
1018 go (Var v) as = (v, as)
1019 go (App f a) as = go f (a:as)
1020 go (Note (SCC _) e) as = pprPanic "CoreToStg.myCollectArgs" (ppr expr)
1021 go (Note n e) as = go e as
1022 go _ as = pprPanic "CoreToStg.myCollectArgs" (ppr expr)
1025 %************************************************************************
1027 \subsection{Figuring out CafInfo for an expression}
1029 %************************************************************************
1031 hasCafRefs decides whether a top-level closure can point into the dynamic heap.
1032 We mark such things as `MayHaveCafRefs' because this information is
1033 used to decide whether a particular closure needs to be referenced
1036 There are two reasons for setting MayHaveCafRefs:
1037 a) The RHS is a CAF: a top-level updatable thunk.
1038 b) The RHS refers to something that MayHaveCafRefs
1040 Possible improvement: In an effort to keep the number of CAFs (and
1041 hence the size of the SRTs) down, we could also look at the expression and
1042 decide whether it requires a small bounded amount of heap, so we can ignore
1043 it as a CAF. In these cases however, we would need to use an additional
1044 CAF list to keep track of non-collectable CAFs.
1047 hasCafRefs :: IdEnv HowBound -> CoreExpr -> CafInfo
1048 -- Only called for the RHS of top-level lets
1049 hasCafRefss :: IdEnv HowBound -> [CoreExpr] -> CafInfo
1050 -- predicate returns True for a given Id if we look at this Id when
1051 -- calculating the result. Used to *avoid* looking at the CafInfo
1052 -- field for an Id that is part of the current recursive group.
1055 | isCAF expr || isFastTrue (cafRefs p expr) = MayHaveCafRefs
1056 | otherwise = NoCafRefs
1058 -- used for recursive groups. The whole group is set to
1059 -- "MayHaveCafRefs" if at least one of the group is a CAF or
1060 -- refers to any CAFs.
1062 | any isCAF exprs || isFastTrue (cafRefss p exprs) = MayHaveCafRefs
1063 | otherwise = NoCafRefs
1065 -- cafRefs compiles to beautiful code :)
1068 | isLocalId id = fastBool False
1070 case lookupVarEnv p id of
1071 Just (LetBound TopLevelHasCafs _ _) -> fastBool True
1072 Just (LetBound _ _ _) -> fastBool False
1073 Nothing -> fastBool (cgMayHaveCafRefs (idCgInfo id)) -- imported Ids
1075 cafRefs p (Lit l) = fastBool False
1076 cafRefs p (App f a) = fastOr (cafRefs p f) (cafRefs p) a
1077 cafRefs p (Lam x e) = cafRefs p e
1078 cafRefs p (Let b e) = fastOr (cafRefss p (rhssOfBind b)) (cafRefs p) e
1079 cafRefs p (Case e bndr alts) = fastOr (cafRefs p e)
1080 (cafRefss p) (rhssOfAlts alts)
1081 cafRefs p (Note n e) = cafRefs p e
1082 cafRefs p (Type t) = fastBool False
1084 cafRefss p [] = fastBool False
1085 cafRefss p (e:es) = fastOr (cafRefs p e) (cafRefss p) es
1087 -- hack for lazy-or over FastBool.
1088 fastOr a f x = fastBool (isFastTrue a || isFastTrue (f x))
1090 isCAF :: CoreExpr -> Bool
1091 -- Only called for the RHS of top-level lets
1092 isCAF e = not (rhsIsNonUpd e)
1093 {- ToDo: check type for onceness, i.e. non-updatable thunks? -}
1096 rhsIsNonUpd :: CoreExpr -> Bool
1097 -- True => Value-lambda, constructor, PAP
1098 -- This is a bit like CoreUtils.exprIsValue, with the following differences:
1099 -- a) scc "foo" (\x -> ...) is updatable (so we catch the right SCC)
1101 -- b) (C x xs), where C is a contructors is updatable if the application is
1102 -- dynamic: see isDynConApp
1104 -- c) don't look through unfolding of f in (f x). I'm suspicious of this one
1106 rhsIsNonUpd (Lam b e) = isId b || rhsIsNonUpd e
1107 rhsIsNonUpd (Note (SCC _) e) = False
1108 rhsIsNonUpd (Note _ e) = rhsIsNonUpd e
1109 rhsIsNonUpd other_expr
1110 = go other_expr 0 []
1112 go (Var f) n_args args = idAppIsNonUpd f n_args args
1114 go (App f a) n_args args
1115 | isTypeArg a = go f n_args args
1116 | otherwise = go f (n_args + 1) (a:args)
1118 go (Note (SCC _) f) n_args args = False
1119 go (Note _ f) n_args args = go f n_args args
1121 go other n_args args = False
1123 idAppIsNonUpd :: Id -> Int -> [CoreExpr] -> Bool
1124 idAppIsNonUpd id n_val_args args
1125 | Just con <- isDataConId_maybe id = not (isDynConApp con args)
1126 | otherwise = n_val_args < idArity id
1128 isDynConApp :: DataCon -> [CoreExpr] -> Bool
1129 isDynConApp con args = isDllName (dataConName con) || any isDynArg args
1130 -- Top-level constructor applications can usually be allocated
1131 -- statically, but they can't if
1132 -- a) the constructor, or any of the arguments, come from another DLL
1133 -- b) any of the arguments are LitLits
1134 -- (because we can't refer to static labels in other DLLs).
1135 -- If this happens we simply make the RHS into an updatable thunk,
1136 -- and 'exectute' it rather than allocating it statically.
1137 -- All this should match the decision in (see CoreToStg.coreToStgRhs)
1140 isDynArg :: CoreExpr -> Bool
1141 isDynArg (Var v) = isDllName (idName v)
1142 isDynArg (Note _ e) = isDynArg e
1143 isDynArg (Lit lit) = isLitLitLit lit
1144 isDynArg (App e _) = isDynArg e -- must be a type app
1145 isDynArg (Lam _ e) = isDynArg e -- must be a type lam