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"
15 import CoreUtils ( rhsIsStatic, manifestArity, exprType, findDefault )
19 import Coercion ( mkUnsafeCoercion )
20 import TyCon ( isAlgTyCon )
22 import Var ( Var, globalIdDetails, idType )
23 import TyCon ( isUnboxedTupleTyCon, isPrimTyCon, isFunTyCon, isHiBootTyCon )
26 import CostCentre ( noCCS )
29 import Maybes ( maybeToBool )
30 import Name ( getOccName, isExternalName, nameOccName )
31 import OccName ( occNameString, occNameFS )
32 import BasicTypes ( Arity )
33 import StaticFlags ( opt_RuntimeTypes )
34 import PackageConfig ( PackageId )
40 %************************************************************************
42 \subsection[live-vs-free-doc]{Documentation}
44 %************************************************************************
46 (There is other relevant documentation in codeGen/CgLetNoEscape.)
48 The actual Stg datatype is decorated with {\em live variable}
49 information, as well as {\em free variable} information. The two are
50 {\em not} the same. Liveness is an operational property rather than a
51 semantic one. A variable is live at a particular execution point if
52 it can be referred to {\em directly} again. In particular, a dead
53 variable's stack slot (if it has one):
56 should be stubbed to avoid space leaks, and
58 may be reused for something else.
61 There ought to be a better way to say this. Here are some examples:
68 Just after the `in', v is live, but q is dead. If the whole of that
69 let expression was enclosed in a case expression, thus:
71 case (let v = [q] \[x] -> e in ...v...) of
74 (ie @alts@ mention @q@), then @q@ is live even after the `in'; because
75 we'll return later to the @alts@ and need it.
77 Let-no-escapes make this a bit more interesting:
79 let-no-escape v = [q] \ [x] -> e
83 Here, @q@ is still live at the `in', because @v@ is represented not by
84 a closure but by the current stack state. In other words, if @v@ is
85 live then so is @q@. Furthermore, if @e@ mentions an enclosing
86 let-no-escaped variable, then {\em its} free variables are also live
89 %************************************************************************
91 \subsection[caf-info]{Collecting live CAF info}
93 %************************************************************************
95 In this pass we also collect information on which CAFs are live for
96 constructing SRTs (see SRT.lhs).
98 A top-level Id has CafInfo, which is
100 - MayHaveCafRefs, if it may refer indirectly to
102 - NoCafRefs if it definitely doesn't
104 The CafInfo has already been calculated during the CoreTidy pass.
106 During CoreToStg, we then pin onto each binding and case expression, a
107 list of Ids which represents the "live" CAFs at that point. The meaning
108 of "live" here is the same as for live variables, see above (which is
109 why it's convenient to collect CAF information here rather than elsewhere).
111 The later SRT pass takes these lists of Ids and uses them to construct
112 the actual nested SRTs, and replaces the lists of Ids with (offset,length)
116 Interaction of let-no-escape with SRTs [Sept 01]
117 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
120 let-no-escape x = ...caf1...caf2...
124 where caf1,caf2 are CAFs. Since x doesn't have a closure, we
125 build SRTs just as if x's defn was inlined at each call site, and
126 that means that x's CAF refs get duplicated in the overall SRT.
128 This is unlike ordinary lets, in which the CAF refs are not duplicated.
130 We could fix this loss of (static) sharing by making a sort of pseudo-closure
131 for x, solely to put in the SRTs lower down.
134 %************************************************************************
136 \subsection[binds-StgVarInfo]{Setting variable info: top-level, binds, RHSs}
138 %************************************************************************
141 coreToStg :: PackageId -> [CoreBind] -> IO [StgBinding]
142 coreToStg this_pkg pgm
144 where (_, _, pgm') = coreTopBindsToStg this_pkg emptyVarEnv pgm
146 coreExprToStg :: CoreExpr -> StgExpr
148 = new_expr where (new_expr,_,_) = initLne emptyVarEnv (coreToStgExpr expr)
153 -> IdEnv HowBound -- environment for the bindings
155 -> (IdEnv HowBound, FreeVarsInfo, [StgBinding])
157 coreTopBindsToStg this_pkg env [] = (env, emptyFVInfo, [])
158 coreTopBindsToStg this_pkg env (b:bs)
159 = (env2, fvs2, b':bs')
161 -- env accumulates down the list of binds, fvs accumulates upwards
162 (env1, fvs2, b' ) = coreTopBindToStg this_pkg env fvs1 b
163 (env2, fvs1, bs') = coreTopBindsToStg this_pkg env1 bs
169 -> FreeVarsInfo -- Info about the body
171 -> (IdEnv HowBound, FreeVarsInfo, StgBinding)
173 coreTopBindToStg this_pkg env body_fvs (NonRec id rhs)
175 env' = extendVarEnv env id how_bound
176 how_bound = LetBound TopLet $! manifestArity rhs
180 coreToTopStgRhs this_pkg body_fvs (id,rhs) `thenLne` \ (stg_rhs, fvs') ->
181 returnLne (stg_rhs, fvs')
184 bind = StgNonRec id stg_rhs
186 ASSERT2(manifestArity rhs == stgRhsArity stg_rhs, ppr id $$ (ptext SLIT("rhs:")) <+> ppr rhs $$ (ptext SLIT("stg_rhs:"))<+> ppr stg_rhs $$ (ptext SLIT("Manifest:")) <+> (ppr $ manifestArity rhs) $$ (ptext SLIT("STG:")) <+>(ppr $ stgRhsArity stg_rhs) )
187 ASSERT2(consistentCafInfo id bind, ppr id)
188 -- WARN(not (consistent caf_info bind), ppr id <+> ppr cafs <+> ppCafInfo caf_info)
189 (env', fvs' `unionFVInfo` body_fvs, bind)
191 coreTopBindToStg this_pkg env body_fvs (Rec pairs)
193 (binders, rhss) = unzip pairs
195 extra_env' = [ (b, LetBound TopLet $! manifestArity rhs)
196 | (b, rhs) <- pairs ]
197 env' = extendVarEnvList env extra_env'
201 mapAndUnzipLne (coreToTopStgRhs this_pkg body_fvs) pairs
202 `thenLne` \ (stg_rhss, fvss') ->
203 let fvs' = unionFVInfos fvss' in
204 returnLne (stg_rhss, fvs')
207 bind = StgRec (zip binders stg_rhss)
209 ASSERT2(and [manifestArity rhs == stgRhsArity stg_rhs | (rhs,stg_rhs) <- rhss `zip` stg_rhss], ppr binders)
210 ASSERT2(consistentCafInfo (head binders) bind, ppr binders)
211 (env', fvs' `unionFVInfo` body_fvs, bind)
214 -- Assertion helper: this checks that the CafInfo on the Id matches
215 -- what CoreToStg has figured out about the binding's SRT. The
216 -- CafInfo will be exact in all cases except when CorePrep has
217 -- floated out a binding, in which case it will be approximate.
218 consistentCafInfo id bind
219 | occNameFS (nameOccName (idName id)) == FSLIT("sat")
222 = WARN (not exact, ppr id) safe
224 safe = id_marked_caffy || not binding_is_caffy
225 exact = id_marked_caffy == binding_is_caffy
226 id_marked_caffy = mayHaveCafRefs (idCafInfo id)
227 binding_is_caffy = stgBindHasCafRefs bind
234 -> FreeVarsInfo -- Free var info for the scope of the binding
236 -> LneM (StgRhs, FreeVarsInfo)
238 coreToTopStgRhs this_pkg scope_fv_info (bndr, rhs)
239 = coreToStgExpr rhs `thenLne` \ (new_rhs, rhs_fvs, _) ->
240 freeVarsToLiveVars rhs_fvs `thenLne` \ lv_info ->
241 returnLne (mkTopStgRhs is_static rhs_fvs (mkSRT lv_info) bndr_info new_rhs, rhs_fvs)
243 bndr_info = lookupFVInfo scope_fv_info bndr
244 is_static = rhsIsStatic this_pkg rhs
246 mkTopStgRhs :: Bool -> FreeVarsInfo -> SRT -> StgBinderInfo -> StgExpr
249 mkTopStgRhs is_static rhs_fvs srt binder_info (StgLam _ bndrs body)
250 = ASSERT( is_static )
251 StgRhsClosure noCCS binder_info
257 mkTopStgRhs is_static rhs_fvs srt binder_info (StgConApp con args)
258 | is_static -- StgConApps can be updatable (see isCrossDllConApp)
259 = StgRhsCon noCCS con args
261 mkTopStgRhs is_static rhs_fvs srt binder_info rhs
262 = ASSERT2( not is_static, ppr rhs )
263 StgRhsClosure noCCS binder_info
271 -- ---------------------------------------------------------------------------
273 -- ---------------------------------------------------------------------------
278 -> LneM (StgExpr, -- Decorated STG expr
279 FreeVarsInfo, -- Its free vars (NB free, not live)
280 EscVarsSet) -- Its escapees, a subset of its free vars;
281 -- also a subset of the domain of the envt
282 -- because we are only interested in the escapees
283 -- for vars which might be turned into
284 -- let-no-escaped ones.
287 The second and third components can be derived in a simple bottom up pass, not
288 dependent on any decisions about which variables will be let-no-escaped or
289 not. The first component, that is, the decorated expression, may then depend
290 on these components, but it in turn is not scrutinised as the basis for any
291 decisions. Hence no black holes.
294 coreToStgExpr (Lit l) = returnLne (StgLit l, emptyFVInfo, emptyVarSet)
295 coreToStgExpr (Var v) = coreToStgApp Nothing v []
297 coreToStgExpr expr@(App _ _)
298 = coreToStgApp Nothing f args
300 (f, args) = myCollectArgs expr
302 coreToStgExpr expr@(Lam _ _)
304 (args, body) = myCollectBinders expr
305 args' = filterStgBinders args
307 extendVarEnvLne [ (a, LambdaBound) | a <- args' ] $
308 coreToStgExpr body `thenLne` \ (body, body_fvs, body_escs) ->
310 fvs = args' `minusFVBinders` body_fvs
311 escs = body_escs `delVarSetList` args'
312 result_expr | null args' = body
313 | otherwise = StgLam (exprType expr) args' body
315 returnLne (result_expr, fvs, escs)
317 coreToStgExpr (Note (SCC cc) expr)
318 = coreToStgExpr expr `thenLne` ( \ (expr2, fvs, escs) ->
319 returnLne (StgSCC cc expr2, fvs, escs) )
321 coreToStgExpr (Note (TickBox m n) expr)
322 = coreToStgExpr expr `thenLne` ( \ (expr2, fvs, escs) ->
323 returnLne (StgTick m n expr2, fvs, escs) )
325 -- BinaryTickBox'es are are removed by the CorePrep pass.
327 coreToStgExpr expr@(Note (BinaryTickBox m t e) _)
328 = pprPanic "coreToStgExpr: " (ppr expr)
330 coreToStgExpr (Note other_note expr)
333 coreToStgExpr (Cast expr co)
336 -- Cases require a little more real work.
338 coreToStgExpr (Case scrut bndr _ alts)
339 = extendVarEnvLne [(bndr, LambdaBound)] (
340 mapAndUnzip3Lne vars_alt alts `thenLne` \ (alts2, fvs_s, escs_s) ->
343 unionVarSets escs_s )
344 ) `thenLne` \ (alts2, alts_fvs, alts_escs) ->
346 -- Determine whether the default binder is dead or not
347 -- This helps the code generator to avoid generating an assignment
348 -- for the case binder (is extremely rare cases) ToDo: remove.
349 bndr' | bndr `elementOfFVInfo` alts_fvs = bndr
350 | otherwise = bndr `setIdOccInfo` IAmDead
352 -- Don't consider the default binder as being 'live in alts',
353 -- since this is from the point of view of the case expr, where
354 -- the default binder is not free.
355 alts_fvs_wo_bndr = bndr `minusFVBinder` alts_fvs
356 alts_escs_wo_bndr = alts_escs `delVarSet` bndr
359 freeVarsToLiveVars alts_fvs_wo_bndr `thenLne` \ alts_lv_info ->
361 -- We tell the scrutinee that everything
362 -- live in the alts is live in it, too.
363 setVarsLiveInCont alts_lv_info (
364 coreToStgExpr scrut `thenLne` \ (scrut2, scrut_fvs, scrut_escs) ->
365 freeVarsToLiveVars scrut_fvs `thenLne` \ scrut_lv_info ->
366 returnLne (scrut2, scrut_fvs, scrut_escs, scrut_lv_info)
368 `thenLne` \ (scrut2, scrut_fvs, scrut_escs, scrut_lv_info) ->
371 StgCase scrut2 (getLiveVars scrut_lv_info)
372 (getLiveVars alts_lv_info)
375 (mkStgAltType (idType bndr) alts)
377 scrut_fvs `unionFVInfo` alts_fvs_wo_bndr,
378 alts_escs_wo_bndr `unionVarSet` getFVSet scrut_fvs
379 -- You might think we should have scrut_escs, not
380 -- (getFVSet scrut_fvs), but actually we can't call, and
381 -- then return from, a let-no-escape thing.
384 vars_alt (con, binders, rhs)
385 = let -- Remove type variables
386 binders' = filterStgBinders binders
388 extendVarEnvLne [(b, LambdaBound) | b <- binders'] $
389 coreToStgExpr rhs `thenLne` \ (rhs2, rhs_fvs, rhs_escs) ->
391 -- Records whether each param is used in the RHS
392 good_use_mask = [ b `elementOfFVInfo` rhs_fvs | b <- binders' ]
394 returnLne ( (con, binders', good_use_mask, rhs2),
395 binders' `minusFVBinders` rhs_fvs,
396 rhs_escs `delVarSetList` binders' )
397 -- ToDo: remove the delVarSet;
398 -- since escs won't include any of these binders
401 Lets not only take quite a bit of work, but this is where we convert
402 then to let-no-escapes, if we wish.
404 (Meanwhile, we don't expect to see let-no-escapes...)
406 coreToStgExpr (Let bind body)
407 = fixLne (\ ~(_, _, _, no_binder_escapes) ->
408 coreToStgLet no_binder_escapes bind body
409 ) `thenLne` \ (new_let, fvs, escs, _) ->
411 returnLne (new_let, fvs, escs)
415 mkStgAltType scrut_ty alts
416 = case splitTyConApp_maybe (repType scrut_ty) of
417 Just (tc,_) | isUnboxedTupleTyCon tc -> UbxTupAlt tc
418 | isPrimTyCon tc -> PrimAlt tc
419 | isHiBootTyCon tc -> look_for_better_tycon
420 | isAlgTyCon tc -> AlgAlt tc
421 | isFunTyCon tc -> PolyAlt
422 | otherwise -> pprPanic "mkStgAlts" (ppr tc)
426 -- Sometimes, the TyCon in the type of the scrutinee is an HiBootTyCon,
427 -- which may not have any constructors inside it. If so, then we
428 -- can get a better TyCon by grabbing the one from a constructor alternative
430 look_for_better_tycon
431 | ((DataAlt con, _, _) : _) <- data_alts =
432 AlgAlt (dataConTyCon con)
434 ASSERT(null data_alts)
437 (data_alts, _deflt) = findDefault alts
441 -- ---------------------------------------------------------------------------
443 -- ---------------------------------------------------------------------------
447 :: Maybe UpdateFlag -- Just upd <=> this application is
448 -- the rhs of a thunk binding
449 -- x = [...] \upd [] -> the_app
450 -- with specified update flag
452 -> [CoreArg] -- Arguments
453 -> LneM (StgExpr, FreeVarsInfo, EscVarsSet)
455 coreToStgApp maybe_thunk_body f args
456 = coreToStgArgs args `thenLne` \ (args', args_fvs) ->
457 lookupVarLne f `thenLne` \ how_bound ->
460 n_val_args = valArgCount args
461 not_letrec_bound = not (isLetBound how_bound)
463 = let fvs = singletonFVInfo f how_bound fun_occ in
464 -- e.g. (f :: a -> int) (x :: a)
465 -- Here the free variables are "f", "x" AND the type variable "a"
466 -- coreToStgArgs will deal with the arguments recursively
467 if opt_RuntimeTypes then
468 fvs `unionFVInfo` tyvarFVInfo (tyVarsOfType (idType f))
471 -- Mostly, the arity info of a function is in the fn's IdInfo
472 -- But new bindings introduced by CoreSat may not have no
473 -- arity info; it would do us no good anyway. For example:
474 -- let f = \ab -> e in f
475 -- No point in having correct arity info for f!
476 -- Hence the hasArity stuff below.
477 -- NB: f_arity is only consulted for LetBound things
478 f_arity = stgArity f how_bound
479 saturated = f_arity <= n_val_args
482 | not_letrec_bound = noBinderInfo -- Uninteresting variable
483 | f_arity > 0 && saturated = stgSatOcc -- Saturated or over-saturated function call
484 | otherwise = stgUnsatOcc -- Unsaturated function or thunk
487 | not_letrec_bound = emptyVarSet -- Only letrec-bound escapees are interesting
488 | f_arity == n_val_args = emptyVarSet -- A function *or thunk* with an exactly
489 -- saturated call doesn't escape
490 -- (let-no-escape applies to 'thunks' too)
492 | otherwise = unitVarSet f -- Inexact application; it does escape
494 -- At the moment of the call:
496 -- either the function is *not* let-no-escaped, in which case
497 -- nothing is live except live_in_cont
498 -- or the function *is* let-no-escaped in which case the
499 -- variables it uses are live, but still the function
500 -- itself is not. PS. In this case, the function's
501 -- live vars should already include those of the
502 -- continuation, but it does no harm to just union the
505 res_ty = exprType (mkApps (Var f) args)
506 app = case globalIdDetails f of
507 DataConWorkId dc | saturated -> StgConApp dc args'
508 PrimOpId op -> ASSERT( saturated )
509 StgOpApp (StgPrimOp op) args' res_ty
510 FCallId call -> ASSERT( saturated )
511 StgOpApp (StgFCallOp call (idUnique f)) args' res_ty
512 _other -> StgApp f args'
517 fun_fvs `unionFVInfo` args_fvs,
518 fun_escs `unionVarSet` (getFVSet args_fvs)
519 -- All the free vars of the args are disqualified
520 -- from being let-no-escaped.
525 -- ---------------------------------------------------------------------------
527 -- This is the guy that turns applications into A-normal form
528 -- ---------------------------------------------------------------------------
530 coreToStgArgs :: [CoreArg] -> LneM ([StgArg], FreeVarsInfo)
532 = returnLne ([], emptyFVInfo)
534 coreToStgArgs (Type ty : args) -- Type argument
535 = coreToStgArgs args `thenLne` \ (args', fvs) ->
536 if opt_RuntimeTypes then
537 returnLne (StgTypeArg ty : args', fvs `unionFVInfo` tyvarFVInfo (tyVarsOfType ty))
539 returnLne (args', fvs)
541 coreToStgArgs (arg : args) -- Non-type argument
542 = coreToStgArgs args `thenLne` \ (stg_args, args_fvs) ->
543 coreToStgExpr arg `thenLne` \ (arg', arg_fvs, escs) ->
545 fvs = args_fvs `unionFVInfo` arg_fvs
546 stg_arg = case arg' of
547 StgApp v [] -> StgVarArg v
548 StgConApp con [] -> StgVarArg (dataConWorkId con)
549 StgLit lit -> StgLitArg lit
550 _ -> pprPanic "coreToStgArgs" (ppr arg)
552 returnLne (stg_arg : stg_args, fvs)
555 -- ---------------------------------------------------------------------------
556 -- The magic for lets:
557 -- ---------------------------------------------------------------------------
560 :: Bool -- True <=> yes, we are let-no-escaping this let
561 -> CoreBind -- bindings
563 -> LneM (StgExpr, -- new let
564 FreeVarsInfo, -- variables free in the whole let
565 EscVarsSet, -- variables that escape from the whole let
566 Bool) -- True <=> none of the binders in the bindings
567 -- is among the escaping vars
569 coreToStgLet let_no_escape bind body
570 = fixLne (\ ~(_, _, _, _, _, rec_body_fvs, _, _) ->
572 -- Do the bindings, setting live_in_cont to empty if
573 -- we ain't in a let-no-escape world
574 getVarsLiveInCont `thenLne` \ live_in_cont ->
575 setVarsLiveInCont (if let_no_escape
578 (vars_bind rec_body_fvs bind)
579 `thenLne` \ ( bind2, bind_fvs, bind_escs, bind_lv_info, env_ext) ->
582 extendVarEnvLne env_ext (
583 coreToStgExpr body `thenLne` \(body2, body_fvs, body_escs) ->
584 freeVarsToLiveVars body_fvs `thenLne` \ body_lv_info ->
586 returnLne (bind2, bind_fvs, bind_escs, getLiveVars bind_lv_info,
587 body2, body_fvs, body_escs, getLiveVars body_lv_info)
590 ) `thenLne` (\ (bind2, bind_fvs, bind_escs, bind_lvs,
591 body2, body_fvs, body_escs, body_lvs) ->
594 -- Compute the new let-expression
596 new_let | let_no_escape = StgLetNoEscape live_in_whole_let bind_lvs bind2 body2
597 | otherwise = StgLet bind2 body2
600 = binders `minusFVBinders` (bind_fvs `unionFVInfo` body_fvs)
603 = bind_lvs `unionVarSet` (body_lvs `delVarSetList` binders)
605 real_bind_escs = if let_no_escape then
609 -- Everything escapes which is free in the bindings
611 let_escs = (real_bind_escs `unionVarSet` body_escs) `delVarSetList` binders
613 all_escs = bind_escs `unionVarSet` body_escs -- Still includes binders of
616 no_binder_escapes = isEmptyVarSet (set_of_binders `intersectVarSet` all_escs)
619 -- Debugging code as requested by Andrew Kennedy
620 checked_no_binder_escapes
621 | not no_binder_escapes && any is_join_var binders
622 = pprTrace "Interesting! A join var that isn't let-no-escaped" (ppr binders)
624 | otherwise = no_binder_escapes
626 checked_no_binder_escapes = no_binder_escapes
629 -- Mustn't depend on the passed-in let_no_escape flag, since
630 -- no_binder_escapes is used by the caller to derive the flag!
636 checked_no_binder_escapes
639 set_of_binders = mkVarSet binders
640 binders = bindersOf bind
642 mk_binding bind_lv_info binder rhs
643 = (binder, LetBound (NestedLet live_vars) (manifestArity rhs))
645 live_vars | let_no_escape = addLiveVar bind_lv_info binder
646 | otherwise = unitLiveVar binder
647 -- c.f. the invariant on NestedLet
649 vars_bind :: FreeVarsInfo -- Free var info for body of binding
653 EscVarsSet, -- free vars; escapee vars
654 LiveInfo, -- Vars and CAFs live in binding
655 [(Id, HowBound)]) -- extension to environment
658 vars_bind body_fvs (NonRec binder rhs)
659 = coreToStgRhs body_fvs [] (binder,rhs)
660 `thenLne` \ (rhs2, bind_fvs, bind_lv_info, escs) ->
662 env_ext_item = mk_binding bind_lv_info binder rhs
664 returnLne (StgNonRec binder rhs2,
665 bind_fvs, escs, bind_lv_info, [env_ext_item])
668 vars_bind body_fvs (Rec pairs)
669 = fixLne (\ ~(_, rec_rhs_fvs, _, bind_lv_info, _) ->
671 rec_scope_fvs = unionFVInfo body_fvs rec_rhs_fvs
672 binders = map fst pairs
673 env_ext = [ mk_binding bind_lv_info b rhs
676 extendVarEnvLne env_ext (
677 mapAndUnzip4Lne (coreToStgRhs rec_scope_fvs binders) pairs
678 `thenLne` \ (rhss2, fvss, lv_infos, escss) ->
680 bind_fvs = unionFVInfos fvss
681 bind_lv_info = foldr unionLiveInfo emptyLiveInfo lv_infos
682 escs = unionVarSets escss
684 returnLne (StgRec (binders `zip` rhss2),
685 bind_fvs, escs, bind_lv_info, env_ext)
689 is_join_var :: Id -> Bool
690 -- A hack (used only for compiler debuggging) to tell if
691 -- a variable started life as a join point ($j)
692 is_join_var j = occNameString (getOccName j) == "$j"
696 coreToStgRhs :: FreeVarsInfo -- Free var info for the scope of the binding
699 -> LneM (StgRhs, FreeVarsInfo, LiveInfo, EscVarsSet)
701 coreToStgRhs scope_fv_info binders (bndr, rhs)
702 = coreToStgExpr rhs `thenLne` \ (new_rhs, rhs_fvs, rhs_escs) ->
703 getEnvLne `thenLne` \ env ->
704 freeVarsToLiveVars (binders `minusFVBinders` rhs_fvs) `thenLne` \ lv_info ->
705 returnLne (mkStgRhs rhs_fvs (mkSRT lv_info) bndr_info new_rhs,
706 rhs_fvs, lv_info, rhs_escs)
708 bndr_info = lookupFVInfo scope_fv_info bndr
710 mkStgRhs :: FreeVarsInfo -> SRT -> StgBinderInfo -> StgExpr -> StgRhs
712 mkStgRhs rhs_fvs srt binder_info (StgConApp con args)
713 = StgRhsCon noCCS con args
715 mkStgRhs rhs_fvs srt binder_info (StgLam _ bndrs body)
716 = StgRhsClosure noCCS binder_info
721 mkStgRhs rhs_fvs srt binder_info rhs
722 = StgRhsClosure noCCS binder_info
728 SDM: disabled. Eval/Apply can't handle functions with arity zero very
729 well; and making these into simple non-updatable thunks breaks other
730 assumptions (namely that they will be entered only once).
732 upd_flag | isPAP env rhs = ReEntrant
733 | otherwise = Updatable
737 upd = if isOnceDem dem
738 then (if isNotTop toplev
739 then SingleEntry -- HA! Paydirt for "dem"
742 trace "WARNING: SE CAFs unsupported, forcing UPD instead" $
746 -- For now we forbid SingleEntry CAFs; they tickle the
747 -- ASSERT in rts/Storage.c line 215 at newCAF() re mut_link,
748 -- and I don't understand why. There's only one SE_CAF (well,
749 -- only one that tickled a great gaping bug in an earlier attempt
750 -- at ClosureInfo.getEntryConvention) in the whole of nofib,
751 -- specifically Main.lvl6 in spectral/cryptarithm2.
752 -- So no great loss. KSW 2000-07.
756 Detect thunks which will reduce immediately to PAPs, and make them
757 non-updatable. This has several advantages:
759 - the non-updatable thunk behaves exactly like the PAP,
761 - the thunk is more efficient to enter, because it is
762 specialised to the task.
764 - we save one update frame, one stg_update_PAP, one update
765 and lots of PAP_enters.
767 - in the case where the thunk is top-level, we save building
768 a black hole and futhermore the thunk isn't considered to
769 be a CAF any more, so it doesn't appear in any SRTs.
771 We do it here, because the arity information is accurate, and we need
772 to do it before the SRT pass to save the SRT entries associated with
775 isPAP env (StgApp f args) = listLengthCmp args arity == LT -- idArity f > length args
777 arity = stgArity f (lookupBinding env f)
781 %************************************************************************
783 \subsection[LNE-monad]{A little monad for this let-no-escaping pass}
785 %************************************************************************
787 There's a lot of stuff to pass around, so we use this @LneM@ monad to
788 help. All the stuff here is only passed *down*.
791 type LneM a = IdEnv HowBound
792 -> LiveInfo -- Vars and CAFs live in continuation
795 type LiveInfo = (StgLiveVars, -- Dynamic live variables;
796 -- i.e. ones with a nested (non-top-level) binding
797 CafSet) -- Static live variables;
798 -- i.e. top-level variables that are CAFs or refer to them
800 type EscVarsSet = IdSet
804 = ImportBound -- Used only as a response to lookupBinding; never
805 -- exists in the range of the (IdEnv HowBound)
807 | LetBound -- A let(rec) in this module
808 LetInfo -- Whether top level or nested
809 Arity -- Its arity (local Ids don't have arity info at this point)
811 | LambdaBound -- Used for both lambda and case
814 = TopLet -- top level things
815 | NestedLet LiveInfo -- For nested things, what is live if this
816 -- thing is live? Invariant: the binder
817 -- itself is always a member of
818 -- the dynamic set of its own LiveInfo
820 isLetBound (LetBound _ _) = True
821 isLetBound other = False
823 topLevelBound ImportBound = True
824 topLevelBound (LetBound TopLet _) = True
825 topLevelBound other = False
828 For a let(rec)-bound variable, x, we record LiveInfo, the set of
829 variables that are live if x is live. This LiveInfo comprises
830 (a) dynamic live variables (ones with a non-top-level binding)
831 (b) static live variabes (CAFs or things that refer to CAFs)
833 For "normal" variables (a) is just x alone. If x is a let-no-escaped
834 variable then x is represented by a code pointer and a stack pointer
835 (well, one for each stack). So all of the variables needed in the
836 execution of x are live if x is, and are therefore recorded in the
837 LetBound constructor; x itself *is* included.
839 The set of dynamic live variables is guaranteed ot have no further let-no-escaped
843 emptyLiveInfo :: LiveInfo
844 emptyLiveInfo = (emptyVarSet,emptyVarSet)
846 unitLiveVar :: Id -> LiveInfo
847 unitLiveVar lv = (unitVarSet lv, emptyVarSet)
849 unitLiveCaf :: Id -> LiveInfo
850 unitLiveCaf caf = (emptyVarSet, unitVarSet caf)
852 addLiveVar :: LiveInfo -> Id -> LiveInfo
853 addLiveVar (lvs, cafs) id = (lvs `extendVarSet` id, cafs)
855 unionLiveInfo :: LiveInfo -> LiveInfo -> LiveInfo
856 unionLiveInfo (lv1,caf1) (lv2,caf2) = (lv1 `unionVarSet` lv2, caf1 `unionVarSet` caf2)
858 mkSRT :: LiveInfo -> SRT
859 mkSRT (_, cafs) = SRTEntries cafs
861 getLiveVars :: LiveInfo -> StgLiveVars
862 getLiveVars (lvs, _) = lvs
866 The std monad functions:
868 initLne :: IdEnv HowBound -> LneM a -> a
869 initLne env m = m env emptyLiveInfo
873 {-# INLINE thenLne #-}
874 {-# INLINE returnLne #-}
876 returnLne :: a -> LneM a
877 returnLne e env lvs_cont = e
879 thenLne :: LneM a -> (a -> LneM b) -> LneM b
880 thenLne m k env lvs_cont
881 = k (m env lvs_cont) env lvs_cont
883 mapAndUnzipLne :: (a -> LneM (b,c)) -> [a] -> LneM ([b],[c])
884 mapAndUnzipLne f [] = returnLne ([],[])
885 mapAndUnzipLne f (x:xs)
886 = f x `thenLne` \ (r1, r2) ->
887 mapAndUnzipLne f xs `thenLne` \ (rs1, rs2) ->
888 returnLne (r1:rs1, r2:rs2)
890 mapAndUnzip3Lne :: (a -> LneM (b,c,d)) -> [a] -> LneM ([b],[c],[d])
891 mapAndUnzip3Lne f [] = returnLne ([],[],[])
892 mapAndUnzip3Lne f (x:xs)
893 = f x `thenLne` \ (r1, r2, r3) ->
894 mapAndUnzip3Lne f xs `thenLne` \ (rs1, rs2, rs3) ->
895 returnLne (r1:rs1, r2:rs2, r3:rs3)
897 mapAndUnzip4Lne :: (a -> LneM (b,c,d,e)) -> [a] -> LneM ([b],[c],[d],[e])
898 mapAndUnzip4Lne f [] = returnLne ([],[],[],[])
899 mapAndUnzip4Lne f (x:xs)
900 = f x `thenLne` \ (r1, r2, r3, r4) ->
901 mapAndUnzip4Lne f xs `thenLne` \ (rs1, rs2, rs3, rs4) ->
902 returnLne (r1:rs1, r2:rs2, r3:rs3, r4:rs4)
904 fixLne :: (a -> LneM a) -> LneM a
905 fixLne expr env lvs_cont
908 result = expr result env lvs_cont
911 Functions specific to this monad:
914 getVarsLiveInCont :: LneM LiveInfo
915 getVarsLiveInCont env lvs_cont = lvs_cont
917 setVarsLiveInCont :: LiveInfo -> LneM a -> LneM a
918 setVarsLiveInCont new_lvs_cont expr env lvs_cont
919 = expr env new_lvs_cont
921 extendVarEnvLne :: [(Id, HowBound)] -> LneM a -> LneM a
922 extendVarEnvLne ids_w_howbound expr env lvs_cont
923 = expr (extendVarEnvList env ids_w_howbound) lvs_cont
925 lookupVarLne :: Id -> LneM HowBound
926 lookupVarLne v env lvs_cont = returnLne (lookupBinding env v) env lvs_cont
928 getEnvLne :: LneM (IdEnv HowBound)
929 getEnvLne env lvs_cont = returnLne env env lvs_cont
931 lookupBinding :: IdEnv HowBound -> Id -> HowBound
932 lookupBinding env v = case lookupVarEnv env v of
934 Nothing -> ASSERT2( isGlobalId v, ppr v ) ImportBound
937 -- The result of lookupLiveVarsForSet, a set of live variables, is
938 -- only ever tacked onto a decorated expression. It is never used as
939 -- the basis of a control decision, which might give a black hole.
941 freeVarsToLiveVars :: FreeVarsInfo -> LneM LiveInfo
942 freeVarsToLiveVars fvs env live_in_cont
943 = returnLne live_info env live_in_cont
945 live_info = foldr unionLiveInfo live_in_cont lvs_from_fvs
946 lvs_from_fvs = map do_one (allFreeIds fvs)
948 do_one (v, how_bound)
950 ImportBound -> unitLiveCaf v -- Only CAF imports are
953 | mayHaveCafRefs (idCafInfo v) -> unitLiveCaf v
954 | otherwise -> emptyLiveInfo
956 LetBound (NestedLet lvs) _ -> lvs -- lvs already contains v
957 -- (see the invariant on NestedLet)
959 _lambda_or_case_binding -> unitLiveVar v -- Bound by lambda or case
962 %************************************************************************
964 \subsection[Free-var info]{Free variable information}
966 %************************************************************************
969 type FreeVarsInfo = VarEnv (Var, HowBound, StgBinderInfo)
970 -- The Var is so we can gather up the free variables
973 -- The HowBound info just saves repeated lookups;
974 -- we look up just once when we encounter the occurrence.
975 -- INVARIANT: Any ImportBound Ids are HaveCafRef Ids
976 -- Imported Ids without CAF refs are simply
977 -- not put in the FreeVarsInfo for an expression.
978 -- See singletonFVInfo and freeVarsToLiveVars
980 -- StgBinderInfo records how it occurs; notably, we
981 -- are interested in whether it only occurs in saturated
982 -- applications, because then we don't need to build a
984 -- If f is mapped to noBinderInfo, that means
985 -- that f *is* mentioned (else it wouldn't be in the
986 -- IdEnv at all), but perhaps in an unsaturated applications.
988 -- All case/lambda-bound things are also mapped to
989 -- noBinderInfo, since we aren't interested in their
992 -- For ILX we track free var info for type variables too;
993 -- hence VarEnv not IdEnv
997 emptyFVInfo :: FreeVarsInfo
998 emptyFVInfo = emptyVarEnv
1000 singletonFVInfo :: Id -> HowBound -> StgBinderInfo -> FreeVarsInfo
1001 -- Don't record non-CAF imports at all, to keep free-var sets small
1002 singletonFVInfo id ImportBound info
1003 | mayHaveCafRefs (idCafInfo id) = unitVarEnv id (id, ImportBound, info)
1004 | otherwise = emptyVarEnv
1005 singletonFVInfo id how_bound info = unitVarEnv id (id, how_bound, info)
1007 tyvarFVInfo :: TyVarSet -> FreeVarsInfo
1008 tyvarFVInfo tvs = foldVarSet add emptyFVInfo tvs
1010 add tv fvs = extendVarEnv fvs tv (tv, LambdaBound, noBinderInfo)
1011 -- Type variables must be lambda-bound
1013 unionFVInfo :: FreeVarsInfo -> FreeVarsInfo -> FreeVarsInfo
1014 unionFVInfo fv1 fv2 = plusVarEnv_C plusFVInfo fv1 fv2
1016 unionFVInfos :: [FreeVarsInfo] -> FreeVarsInfo
1017 unionFVInfos fvs = foldr unionFVInfo emptyFVInfo fvs
1019 minusFVBinders :: [Id] -> FreeVarsInfo -> FreeVarsInfo
1020 minusFVBinders vs fv = foldr minusFVBinder fv vs
1022 minusFVBinder :: Id -> FreeVarsInfo -> FreeVarsInfo
1023 minusFVBinder v fv | isId v && opt_RuntimeTypes
1024 = (fv `delVarEnv` v) `unionFVInfo`
1025 tyvarFVInfo (tyVarsOfType (idType v))
1026 | otherwise = fv `delVarEnv` v
1027 -- When removing a binder, remember to add its type variables
1028 -- c.f. CoreFVs.delBinderFV
1030 elementOfFVInfo :: Id -> FreeVarsInfo -> Bool
1031 elementOfFVInfo id fvs = maybeToBool (lookupVarEnv fvs id)
1033 lookupFVInfo :: FreeVarsInfo -> Id -> StgBinderInfo
1034 -- Find how the given Id is used.
1035 -- Externally visible things may be used any old how
1037 | isExternalName (idName id) = noBinderInfo
1038 | otherwise = case lookupVarEnv fvs id of
1039 Nothing -> noBinderInfo
1040 Just (_,_,info) -> info
1042 allFreeIds :: FreeVarsInfo -> [(Id,HowBound)] -- Both top level and non-top-level Ids
1043 allFreeIds fvs = [(id,how_bound) | (id,how_bound,_) <- varEnvElts fvs, isId id]
1045 -- Non-top-level things only, both type variables and ids
1046 -- (type variables only if opt_RuntimeTypes)
1047 getFVs :: FreeVarsInfo -> [Var]
1048 getFVs fvs = [id | (id, how_bound, _) <- varEnvElts fvs,
1049 not (topLevelBound how_bound) ]
1051 getFVSet :: FreeVarsInfo -> VarSet
1052 getFVSet fvs = mkVarSet (getFVs fvs)
1054 plusFVInfo (id1,hb1,info1) (id2,hb2,info2)
1055 = ASSERT (id1 == id2 && hb1 `check_eq_how_bound` hb2)
1056 (id1, hb1, combineStgBinderInfo info1 info2)
1059 -- The HowBound info for a variable in the FVInfo should be consistent
1060 check_eq_how_bound ImportBound ImportBound = True
1061 check_eq_how_bound LambdaBound LambdaBound = True
1062 check_eq_how_bound (LetBound li1 ar1) (LetBound li2 ar2) = ar1 == ar2 && check_eq_li li1 li2
1063 check_eq_how_bound hb1 hb2 = False
1065 check_eq_li (NestedLet _) (NestedLet _) = True
1066 check_eq_li TopLet TopLet = True
1067 check_eq_li li1 li2 = False
1073 filterStgBinders :: [Var] -> [Var]
1074 filterStgBinders bndrs
1075 | opt_RuntimeTypes = bndrs
1076 | otherwise = filter isId bndrs
1081 -- Ignore all notes except SCC
1082 myCollectBinders expr
1085 go bs (Lam b e) = go (b:bs) e
1086 go bs e@(Note (SCC _) _) = (reverse bs, e)
1087 go bs e@(Note (TickBox {}) _) = (reverse bs, e)
1088 go bs e@(Note (BinaryTickBox {}) _) = (reverse bs, e)
1089 go bs (Cast e co) = go bs e
1090 go bs (Note _ e) = go bs e
1091 go bs e = (reverse bs, e)
1093 myCollectArgs :: CoreExpr -> (Id, [CoreArg])
1094 -- We assume that we only have variables
1095 -- in the function position by now
1099 go (Var v) as = (v, as)
1100 go (App f a) as = go f (a:as)
1101 go (Note (SCC _) e) as = pprPanic "CoreToStg.myCollectArgs" (ppr expr)
1102 go (Note (TickBox {}) e) as = pprPanic "CoreToStg.myCollectArgs" (ppr expr)
1103 go (Note (BinaryTickBox {}) e) as = pprPanic "CoreToStg.myCollectArgs" (ppr expr)
1104 go (Cast e co) as = go e as
1105 go (Note n e) as = go e as
1106 go _ as = pprPanic "CoreToStg.myCollectArgs" (ppr expr)
1110 stgArity :: Id -> HowBound -> Arity
1111 stgArity f (LetBound _ arity) = arity
1112 stgArity f ImportBound = idArity f
1113 stgArity f LambdaBound = 0