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 )
21 import Var ( Var, globalIdDetails, idType )
22 import TyCon ( isUnboxedTupleTyCon, isPrimTyCon, isFunTyCon, isHiBootTyCon )
25 import CostCentre ( noCCS )
28 import Maybes ( maybeToBool )
29 import Name ( getOccName, isExternalName, nameOccName )
30 import OccName ( occNameString, occNameFS )
31 import BasicTypes ( Arity )
32 import StaticFlags ( opt_RuntimeTypes )
33 import PackageConfig ( PackageId )
39 %************************************************************************
41 \subsection[live-vs-free-doc]{Documentation}
43 %************************************************************************
45 (There is other relevant documentation in codeGen/CgLetNoEscape.)
47 The actual Stg datatype is decorated with {\em live variable}
48 information, as well as {\em free variable} information. The two are
49 {\em not} the same. Liveness is an operational property rather than a
50 semantic one. A variable is live at a particular execution point if
51 it can be referred to {\em directly} again. In particular, a dead
52 variable's stack slot (if it has one):
55 should be stubbed to avoid space leaks, and
57 may be reused for something else.
60 There ought to be a better way to say this. Here are some examples:
67 Just after the `in', v is live, but q is dead. If the whole of that
68 let expression was enclosed in a case expression, thus:
70 case (let v = [q] \[x] -> e in ...v...) of
73 (ie @alts@ mention @q@), then @q@ is live even after the `in'; because
74 we'll return later to the @alts@ and need it.
76 Let-no-escapes make this a bit more interesting:
78 let-no-escape v = [q] \ [x] -> e
82 Here, @q@ is still live at the `in', because @v@ is represented not by
83 a closure but by the current stack state. In other words, if @v@ is
84 live then so is @q@. Furthermore, if @e@ mentions an enclosing
85 let-no-escaped variable, then {\em its} free variables are also live
88 %************************************************************************
90 \subsection[caf-info]{Collecting live CAF info}
92 %************************************************************************
94 In this pass we also collect information on which CAFs are live for
95 constructing SRTs (see SRT.lhs).
97 A top-level Id has CafInfo, which is
99 - MayHaveCafRefs, if it may refer indirectly to
101 - NoCafRefs if it definitely doesn't
103 The CafInfo has already been calculated during the CoreTidy pass.
105 During CoreToStg, we then pin onto each binding and case expression, a
106 list of Ids which represents the "live" CAFs at that point. The meaning
107 of "live" here is the same as for live variables, see above (which is
108 why it's convenient to collect CAF information here rather than elsewhere).
110 The later SRT pass takes these lists of Ids and uses them to construct
111 the actual nested SRTs, and replaces the lists of Ids with (offset,length)
115 Interaction of let-no-escape with SRTs [Sept 01]
116 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
119 let-no-escape x = ...caf1...caf2...
123 where caf1,caf2 are CAFs. Since x doesn't have a closure, we
124 build SRTs just as if x's defn was inlined at each call site, and
125 that means that x's CAF refs get duplicated in the overall SRT.
127 This is unlike ordinary lets, in which the CAF refs are not duplicated.
129 We could fix this loss of (static) sharing by making a sort of pseudo-closure
130 for x, solely to put in the SRTs lower down.
133 %************************************************************************
135 \subsection[binds-StgVarInfo]{Setting variable info: top-level, binds, RHSs}
137 %************************************************************************
140 coreToStg :: PackageId -> [CoreBind] -> IO [StgBinding]
141 coreToStg this_pkg pgm
143 where (_, _, pgm') = coreTopBindsToStg this_pkg emptyVarEnv pgm
145 coreExprToStg :: CoreExpr -> StgExpr
147 = new_expr where (new_expr,_,_) = initLne emptyVarEnv (coreToStgExpr expr)
152 -> IdEnv HowBound -- environment for the bindings
154 -> (IdEnv HowBound, FreeVarsInfo, [StgBinding])
156 coreTopBindsToStg this_pkg env [] = (env, emptyFVInfo, [])
157 coreTopBindsToStg this_pkg env (b:bs)
158 = (env2, fvs2, b':bs')
160 -- env accumulates down the list of binds, fvs accumulates upwards
161 (env1, fvs2, b' ) = coreTopBindToStg this_pkg env fvs1 b
162 (env2, fvs1, bs') = coreTopBindsToStg this_pkg env1 bs
168 -> FreeVarsInfo -- Info about the body
170 -> (IdEnv HowBound, FreeVarsInfo, StgBinding)
172 coreTopBindToStg this_pkg env body_fvs (NonRec id rhs)
174 env' = extendVarEnv env id how_bound
175 how_bound = LetBound TopLet $! manifestArity rhs
179 coreToTopStgRhs this_pkg body_fvs (id,rhs) `thenLne` \ (stg_rhs, fvs') ->
180 returnLne (stg_rhs, fvs')
183 bind = StgNonRec id stg_rhs
185 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) )
186 ASSERT2(consistentCafInfo id bind, ppr id)
187 -- WARN(not (consistent caf_info bind), ppr id <+> ppr cafs <+> ppCafInfo caf_info)
188 (env', fvs' `unionFVInfo` body_fvs, bind)
190 coreTopBindToStg this_pkg env body_fvs (Rec pairs)
192 (binders, rhss) = unzip pairs
194 extra_env' = [ (b, LetBound TopLet $! manifestArity rhs)
195 | (b, rhs) <- pairs ]
196 env' = extendVarEnvList env extra_env'
200 mapAndUnzipLne (coreToTopStgRhs this_pkg body_fvs) pairs
201 `thenLne` \ (stg_rhss, fvss') ->
202 let fvs' = unionFVInfos fvss' in
203 returnLne (stg_rhss, fvs')
206 bind = StgRec (zip binders stg_rhss)
208 ASSERT2(and [manifestArity rhs == stgRhsArity stg_rhs | (rhs,stg_rhs) <- rhss `zip` stg_rhss], ppr binders)
209 ASSERT2(consistentCafInfo (head binders) bind, ppr binders)
210 (env', fvs' `unionFVInfo` body_fvs, bind)
213 -- Assertion helper: this checks that the CafInfo on the Id matches
214 -- what CoreToStg has figured out about the binding's SRT. The
215 -- CafInfo will be exact in all cases except when CorePrep has
216 -- floated out a binding, in which case it will be approximate.
217 consistentCafInfo id bind
218 | occNameFS (nameOccName (idName id)) == FSLIT("sat")
221 = WARN (not exact, ppr id) safe
223 safe = id_marked_caffy || not binding_is_caffy
224 exact = id_marked_caffy == binding_is_caffy
225 id_marked_caffy = mayHaveCafRefs (idCafInfo id)
226 binding_is_caffy = stgBindHasCafRefs bind
233 -> FreeVarsInfo -- Free var info for the scope of the binding
235 -> LneM (StgRhs, FreeVarsInfo)
237 coreToTopStgRhs this_pkg scope_fv_info (bndr, rhs)
238 = coreToStgExpr rhs `thenLne` \ (new_rhs, rhs_fvs, _) ->
239 freeVarsToLiveVars rhs_fvs `thenLne` \ lv_info ->
240 returnLne (mkTopStgRhs is_static rhs_fvs (mkSRT lv_info) bndr_info new_rhs, rhs_fvs)
242 bndr_info = lookupFVInfo scope_fv_info bndr
243 is_static = rhsIsStatic this_pkg rhs
245 mkTopStgRhs :: Bool -> FreeVarsInfo -> SRT -> StgBinderInfo -> StgExpr
248 mkTopStgRhs is_static rhs_fvs srt binder_info (StgLam _ bndrs body)
249 = ASSERT( is_static )
250 StgRhsClosure noCCS binder_info
256 mkTopStgRhs is_static rhs_fvs srt binder_info (StgConApp con args)
257 | is_static -- StgConApps can be updatable (see isCrossDllConApp)
258 = StgRhsCon noCCS con args
260 mkTopStgRhs is_static rhs_fvs srt binder_info rhs
261 = ASSERT2( not is_static, ppr rhs )
262 StgRhsClosure noCCS binder_info
270 -- ---------------------------------------------------------------------------
272 -- ---------------------------------------------------------------------------
277 -> LneM (StgExpr, -- Decorated STG expr
278 FreeVarsInfo, -- Its free vars (NB free, not live)
279 EscVarsSet) -- Its escapees, a subset of its free vars;
280 -- also a subset of the domain of the envt
281 -- because we are only interested in the escapees
282 -- for vars which might be turned into
283 -- let-no-escaped ones.
286 The second and third components can be derived in a simple bottom up pass, not
287 dependent on any decisions about which variables will be let-no-escaped or
288 not. The first component, that is, the decorated expression, may then depend
289 on these components, but it in turn is not scrutinised as the basis for any
290 decisions. Hence no black holes.
293 coreToStgExpr (Lit l) = returnLne (StgLit l, emptyFVInfo, emptyVarSet)
294 coreToStgExpr (Var v) = coreToStgApp Nothing v []
296 coreToStgExpr expr@(App _ _)
297 = coreToStgApp Nothing f args
299 (f, args) = myCollectArgs expr
301 coreToStgExpr expr@(Lam _ _)
303 (args, body) = myCollectBinders expr
304 args' = filterStgBinders args
306 extendVarEnvLne [ (a, LambdaBound) | a <- args' ] $
307 coreToStgExpr body `thenLne` \ (body, body_fvs, body_escs) ->
309 fvs = args' `minusFVBinders` body_fvs
310 escs = body_escs `delVarSetList` args'
311 result_expr | null args' = body
312 | otherwise = StgLam (exprType expr) args' body
314 returnLne (result_expr, fvs, escs)
316 coreToStgExpr (Note (SCC cc) expr)
317 = coreToStgExpr expr `thenLne` ( \ (expr2, fvs, escs) ->
318 returnLne (StgSCC cc expr2, fvs, escs) )
320 coreToStgExpr (Case (Var id) _bndr ty [(DEFAULT,[],expr)])
321 | Just (TickBox m n) <- isTickBoxOp_maybe id
322 = coreToStgExpr expr `thenLne` ( \ (expr2, fvs, escs) ->
323 returnLne (StgTick m n expr2, fvs, escs) )
325 coreToStgExpr (Note other_note expr)
328 coreToStgExpr (Cast expr co)
331 -- Cases require a little more real work.
333 coreToStgExpr (Case scrut bndr _ alts)
334 = extendVarEnvLne [(bndr, LambdaBound)] (
335 mapAndUnzip3Lne vars_alt alts `thenLne` \ (alts2, fvs_s, escs_s) ->
338 unionVarSets escs_s )
339 ) `thenLne` \ (alts2, alts_fvs, alts_escs) ->
341 -- Determine whether the default binder is dead or not
342 -- This helps the code generator to avoid generating an assignment
343 -- for the case binder (is extremely rare cases) ToDo: remove.
344 bndr' | bndr `elementOfFVInfo` alts_fvs = bndr
345 | otherwise = bndr `setIdOccInfo` IAmDead
347 -- Don't consider the default binder as being 'live in alts',
348 -- since this is from the point of view of the case expr, where
349 -- the default binder is not free.
350 alts_fvs_wo_bndr = bndr `minusFVBinder` alts_fvs
351 alts_escs_wo_bndr = alts_escs `delVarSet` bndr
354 freeVarsToLiveVars alts_fvs_wo_bndr `thenLne` \ alts_lv_info ->
356 -- We tell the scrutinee that everything
357 -- live in the alts is live in it, too.
358 setVarsLiveInCont alts_lv_info (
359 coreToStgExpr scrut `thenLne` \ (scrut2, scrut_fvs, scrut_escs) ->
360 freeVarsToLiveVars scrut_fvs `thenLne` \ scrut_lv_info ->
361 returnLne (scrut2, scrut_fvs, scrut_escs, scrut_lv_info)
363 `thenLne` \ (scrut2, scrut_fvs, scrut_escs, scrut_lv_info) ->
366 StgCase scrut2 (getLiveVars scrut_lv_info)
367 (getLiveVars alts_lv_info)
370 (mkStgAltType (idType bndr) alts)
372 scrut_fvs `unionFVInfo` alts_fvs_wo_bndr,
373 alts_escs_wo_bndr `unionVarSet` getFVSet scrut_fvs
374 -- You might think we should have scrut_escs, not
375 -- (getFVSet scrut_fvs), but actually we can't call, and
376 -- then return from, a let-no-escape thing.
379 vars_alt (con, binders, rhs)
380 = let -- Remove type variables
381 binders' = filterStgBinders binders
383 extendVarEnvLne [(b, LambdaBound) | b <- binders'] $
384 coreToStgExpr rhs `thenLne` \ (rhs2, rhs_fvs, rhs_escs) ->
386 -- Records whether each param is used in the RHS
387 good_use_mask = [ b `elementOfFVInfo` rhs_fvs | b <- binders' ]
389 returnLne ( (con, binders', good_use_mask, rhs2),
390 binders' `minusFVBinders` rhs_fvs,
391 rhs_escs `delVarSetList` binders' )
392 -- ToDo: remove the delVarSet;
393 -- since escs won't include any of these binders
396 Lets not only take quite a bit of work, but this is where we convert
397 then to let-no-escapes, if we wish.
399 (Meanwhile, we don't expect to see let-no-escapes...)
401 coreToStgExpr (Let bind body)
402 = fixLne (\ ~(_, _, _, no_binder_escapes) ->
403 coreToStgLet no_binder_escapes bind body
404 ) `thenLne` \ (new_let, fvs, escs, _) ->
406 returnLne (new_let, fvs, escs)
410 mkStgAltType scrut_ty alts
411 = case splitTyConApp_maybe (repType scrut_ty) of
412 Just (tc,_) | isUnboxedTupleTyCon tc -> UbxTupAlt tc
413 | isUnLiftedTyCon tc -> PrimAlt tc
414 | isHiBootTyCon tc -> look_for_better_tycon
415 | isAlgTyCon tc -> AlgAlt tc
416 | isFunTyCon tc -> PolyAlt
417 | isPrimTyCon tc -> PolyAlt -- for "Any"
418 | otherwise -> pprPanic "mkStgAlts" (ppr tc)
422 -- Sometimes, the TyCon in the type of the scrutinee is an HiBootTyCon,
423 -- which may not have any constructors inside it. If so, then we
424 -- can get a better TyCon by grabbing the one from a constructor alternative
426 look_for_better_tycon
427 | ((DataAlt con, _, _) : _) <- data_alts =
428 AlgAlt (dataConTyCon con)
430 ASSERT(null data_alts)
433 (data_alts, _deflt) = findDefault alts
437 -- ---------------------------------------------------------------------------
439 -- ---------------------------------------------------------------------------
443 :: Maybe UpdateFlag -- Just upd <=> this application is
444 -- the rhs of a thunk binding
445 -- x = [...] \upd [] -> the_app
446 -- with specified update flag
448 -> [CoreArg] -- Arguments
449 -> LneM (StgExpr, FreeVarsInfo, EscVarsSet)
452 coreToStgApp maybe_thunk_body f args
453 = coreToStgArgs args `thenLne` \ (args', args_fvs) ->
454 lookupVarLne f `thenLne` \ how_bound ->
457 n_val_args = valArgCount args
458 not_letrec_bound = not (isLetBound how_bound)
460 = let fvs = singletonFVInfo f how_bound fun_occ in
461 -- e.g. (f :: a -> int) (x :: a)
462 -- Here the free variables are "f", "x" AND the type variable "a"
463 -- coreToStgArgs will deal with the arguments recursively
464 if opt_RuntimeTypes then
465 fvs `unionFVInfo` tyvarFVInfo (tyVarsOfType (idType f))
468 -- Mostly, the arity info of a function is in the fn's IdInfo
469 -- But new bindings introduced by CoreSat may not have no
470 -- arity info; it would do us no good anyway. For example:
471 -- let f = \ab -> e in f
472 -- No point in having correct arity info for f!
473 -- Hence the hasArity stuff below.
474 -- NB: f_arity is only consulted for LetBound things
475 f_arity = stgArity f how_bound
476 saturated = f_arity <= n_val_args
479 | not_letrec_bound = noBinderInfo -- Uninteresting variable
480 | f_arity > 0 && saturated = stgSatOcc -- Saturated or over-saturated function call
481 | otherwise = stgUnsatOcc -- Unsaturated function or thunk
484 | not_letrec_bound = emptyVarSet -- Only letrec-bound escapees are interesting
485 | f_arity == n_val_args = emptyVarSet -- A function *or thunk* with an exactly
486 -- saturated call doesn't escape
487 -- (let-no-escape applies to 'thunks' too)
489 | otherwise = unitVarSet f -- Inexact application; it does escape
491 -- At the moment of the call:
493 -- either the function is *not* let-no-escaped, in which case
494 -- nothing is live except live_in_cont
495 -- or the function *is* let-no-escaped in which case the
496 -- variables it uses are live, but still the function
497 -- itself is not. PS. In this case, the function's
498 -- live vars should already include those of the
499 -- continuation, but it does no harm to just union the
502 res_ty = exprType (mkApps (Var f) args)
503 app = case globalIdDetails f of
504 DataConWorkId dc | saturated -> StgConApp dc args'
505 PrimOpId op -> ASSERT( saturated )
506 StgOpApp (StgPrimOp op) args' res_ty
507 FCallId call -> ASSERT( saturated )
508 StgOpApp (StgFCallOp call (idUnique f)) args' res_ty
509 TickBoxOpId {} -> pprPanic "coreToStg TickBox" $ ppr (f,args')
510 _other -> StgApp f args'
515 fun_fvs `unionFVInfo` args_fvs,
516 fun_escs `unionVarSet` (getFVSet args_fvs)
517 -- All the free vars of the args are disqualified
518 -- from being let-no-escaped.
523 -- ---------------------------------------------------------------------------
525 -- This is the guy that turns applications into A-normal form
526 -- ---------------------------------------------------------------------------
528 coreToStgArgs :: [CoreArg] -> LneM ([StgArg], FreeVarsInfo)
530 = returnLne ([], emptyFVInfo)
532 coreToStgArgs (Type ty : args) -- Type argument
533 = coreToStgArgs args `thenLne` \ (args', fvs) ->
534 if opt_RuntimeTypes then
535 returnLne (StgTypeArg ty : args', fvs `unionFVInfo` tyvarFVInfo (tyVarsOfType ty))
537 returnLne (args', fvs)
539 coreToStgArgs (arg : args) -- Non-type argument
540 = coreToStgArgs args `thenLne` \ (stg_args, args_fvs) ->
541 coreToStgExpr arg `thenLne` \ (arg', arg_fvs, escs) ->
543 fvs = args_fvs `unionFVInfo` arg_fvs
544 stg_arg = case arg' of
545 StgApp v [] -> StgVarArg v
546 StgConApp con [] -> StgVarArg (dataConWorkId con)
547 StgLit lit -> StgLitArg lit
548 _ -> pprPanic "coreToStgArgs" (ppr arg)
550 -- WARNING: what if we have an argument like (v `cast` co)
551 -- where 'co' changes the representation type?
552 -- (This really only happens if co is unsafe.)
553 -- Then all the getArgAmode stuff in CgBindery will set the
554 -- cg_rep of the CgIdInfo based on the type of v, rather
555 -- than the type of 'co'.
556 -- This matters particularly when the function is a primop
558 -- Wanted: a better solution than this hacky warning
560 arg_ty = exprType arg
561 stg_arg_ty = stgArgType stg_arg
563 WARN( isUnLiftedType arg_ty /= isUnLiftedType stg_arg_ty,
564 ptext SLIT("Dangerous-looking argument. Probable cause: bad unsafeCoerce#") $$ ppr arg)
565 returnLne (stg_arg : stg_args, fvs)
568 -- ---------------------------------------------------------------------------
569 -- The magic for lets:
570 -- ---------------------------------------------------------------------------
573 :: Bool -- True <=> yes, we are let-no-escaping this let
574 -> CoreBind -- bindings
576 -> LneM (StgExpr, -- new let
577 FreeVarsInfo, -- variables free in the whole let
578 EscVarsSet, -- variables that escape from the whole let
579 Bool) -- True <=> none of the binders in the bindings
580 -- is among the escaping vars
582 coreToStgLet let_no_escape bind body
583 = fixLne (\ ~(_, _, _, _, _, rec_body_fvs, _, _) ->
585 -- Do the bindings, setting live_in_cont to empty if
586 -- we ain't in a let-no-escape world
587 getVarsLiveInCont `thenLne` \ live_in_cont ->
588 setVarsLiveInCont (if let_no_escape
591 (vars_bind rec_body_fvs bind)
592 `thenLne` \ ( bind2, bind_fvs, bind_escs, bind_lv_info, env_ext) ->
595 extendVarEnvLne env_ext (
596 coreToStgExpr body `thenLne` \(body2, body_fvs, body_escs) ->
597 freeVarsToLiveVars body_fvs `thenLne` \ body_lv_info ->
599 returnLne (bind2, bind_fvs, bind_escs, getLiveVars bind_lv_info,
600 body2, body_fvs, body_escs, getLiveVars body_lv_info)
603 ) `thenLne` (\ (bind2, bind_fvs, bind_escs, bind_lvs,
604 body2, body_fvs, body_escs, body_lvs) ->
607 -- Compute the new let-expression
609 new_let | let_no_escape = StgLetNoEscape live_in_whole_let bind_lvs bind2 body2
610 | otherwise = StgLet bind2 body2
613 = binders `minusFVBinders` (bind_fvs `unionFVInfo` body_fvs)
616 = bind_lvs `unionVarSet` (body_lvs `delVarSetList` binders)
618 real_bind_escs = if let_no_escape then
622 -- Everything escapes which is free in the bindings
624 let_escs = (real_bind_escs `unionVarSet` body_escs) `delVarSetList` binders
626 all_escs = bind_escs `unionVarSet` body_escs -- Still includes binders of
629 no_binder_escapes = isEmptyVarSet (set_of_binders `intersectVarSet` all_escs)
632 -- Debugging code as requested by Andrew Kennedy
633 checked_no_binder_escapes
634 | not no_binder_escapes && any is_join_var binders
635 = pprTrace "Interesting! A join var that isn't let-no-escaped" (ppr binders)
637 | otherwise = no_binder_escapes
639 checked_no_binder_escapes = no_binder_escapes
642 -- Mustn't depend on the passed-in let_no_escape flag, since
643 -- no_binder_escapes is used by the caller to derive the flag!
649 checked_no_binder_escapes
652 set_of_binders = mkVarSet binders
653 binders = bindersOf bind
655 mk_binding bind_lv_info binder rhs
656 = (binder, LetBound (NestedLet live_vars) (manifestArity rhs))
658 live_vars | let_no_escape = addLiveVar bind_lv_info binder
659 | otherwise = unitLiveVar binder
660 -- c.f. the invariant on NestedLet
662 vars_bind :: FreeVarsInfo -- Free var info for body of binding
666 EscVarsSet, -- free vars; escapee vars
667 LiveInfo, -- Vars and CAFs live in binding
668 [(Id, HowBound)]) -- extension to environment
671 vars_bind body_fvs (NonRec binder rhs)
672 = coreToStgRhs body_fvs [] (binder,rhs)
673 `thenLne` \ (rhs2, bind_fvs, bind_lv_info, escs) ->
675 env_ext_item = mk_binding bind_lv_info binder rhs
677 returnLne (StgNonRec binder rhs2,
678 bind_fvs, escs, bind_lv_info, [env_ext_item])
681 vars_bind body_fvs (Rec pairs)
682 = fixLne (\ ~(_, rec_rhs_fvs, _, bind_lv_info, _) ->
684 rec_scope_fvs = unionFVInfo body_fvs rec_rhs_fvs
685 binders = map fst pairs
686 env_ext = [ mk_binding bind_lv_info b rhs
689 extendVarEnvLne env_ext (
690 mapAndUnzip4Lne (coreToStgRhs rec_scope_fvs binders) pairs
691 `thenLne` \ (rhss2, fvss, lv_infos, escss) ->
693 bind_fvs = unionFVInfos fvss
694 bind_lv_info = foldr unionLiveInfo emptyLiveInfo lv_infos
695 escs = unionVarSets escss
697 returnLne (StgRec (binders `zip` rhss2),
698 bind_fvs, escs, bind_lv_info, env_ext)
702 is_join_var :: Id -> Bool
703 -- A hack (used only for compiler debuggging) to tell if
704 -- a variable started life as a join point ($j)
705 is_join_var j = occNameString (getOccName j) == "$j"
709 coreToStgRhs :: FreeVarsInfo -- Free var info for the scope of the binding
712 -> LneM (StgRhs, FreeVarsInfo, LiveInfo, EscVarsSet)
714 coreToStgRhs scope_fv_info binders (bndr, rhs)
715 = coreToStgExpr rhs `thenLne` \ (new_rhs, rhs_fvs, rhs_escs) ->
716 getEnvLne `thenLne` \ env ->
717 freeVarsToLiveVars (binders `minusFVBinders` rhs_fvs) `thenLne` \ lv_info ->
718 returnLne (mkStgRhs rhs_fvs (mkSRT lv_info) bndr_info new_rhs,
719 rhs_fvs, lv_info, rhs_escs)
721 bndr_info = lookupFVInfo scope_fv_info bndr
723 mkStgRhs :: FreeVarsInfo -> SRT -> StgBinderInfo -> StgExpr -> StgRhs
725 mkStgRhs rhs_fvs srt binder_info (StgConApp con args)
726 = StgRhsCon noCCS con args
728 mkStgRhs rhs_fvs srt binder_info (StgLam _ bndrs body)
729 = StgRhsClosure noCCS binder_info
734 mkStgRhs rhs_fvs srt binder_info rhs
735 = StgRhsClosure noCCS binder_info
741 SDM: disabled. Eval/Apply can't handle functions with arity zero very
742 well; and making these into simple non-updatable thunks breaks other
743 assumptions (namely that they will be entered only once).
745 upd_flag | isPAP env rhs = ReEntrant
746 | otherwise = Updatable
750 upd = if isOnceDem dem
751 then (if isNotTop toplev
752 then SingleEntry -- HA! Paydirt for "dem"
755 trace "WARNING: SE CAFs unsupported, forcing UPD instead" $
759 -- For now we forbid SingleEntry CAFs; they tickle the
760 -- ASSERT in rts/Storage.c line 215 at newCAF() re mut_link,
761 -- and I don't understand why. There's only one SE_CAF (well,
762 -- only one that tickled a great gaping bug in an earlier attempt
763 -- at ClosureInfo.getEntryConvention) in the whole of nofib,
764 -- specifically Main.lvl6 in spectral/cryptarithm2.
765 -- So no great loss. KSW 2000-07.
769 Detect thunks which will reduce immediately to PAPs, and make them
770 non-updatable. This has several advantages:
772 - the non-updatable thunk behaves exactly like the PAP,
774 - the thunk is more efficient to enter, because it is
775 specialised to the task.
777 - we save one update frame, one stg_update_PAP, one update
778 and lots of PAP_enters.
780 - in the case where the thunk is top-level, we save building
781 a black hole and futhermore the thunk isn't considered to
782 be a CAF any more, so it doesn't appear in any SRTs.
784 We do it here, because the arity information is accurate, and we need
785 to do it before the SRT pass to save the SRT entries associated with
788 isPAP env (StgApp f args) = listLengthCmp args arity == LT -- idArity f > length args
790 arity = stgArity f (lookupBinding env f)
794 %************************************************************************
796 \subsection[LNE-monad]{A little monad for this let-no-escaping pass}
798 %************************************************************************
800 There's a lot of stuff to pass around, so we use this @LneM@ monad to
801 help. All the stuff here is only passed *down*.
804 type LneM a = IdEnv HowBound
805 -> LiveInfo -- Vars and CAFs live in continuation
808 type LiveInfo = (StgLiveVars, -- Dynamic live variables;
809 -- i.e. ones with a nested (non-top-level) binding
810 CafSet) -- Static live variables;
811 -- i.e. top-level variables that are CAFs or refer to them
813 type EscVarsSet = IdSet
817 = ImportBound -- Used only as a response to lookupBinding; never
818 -- exists in the range of the (IdEnv HowBound)
820 | LetBound -- A let(rec) in this module
821 LetInfo -- Whether top level or nested
822 Arity -- Its arity (local Ids don't have arity info at this point)
824 | LambdaBound -- Used for both lambda and case
827 = TopLet -- top level things
828 | NestedLet LiveInfo -- For nested things, what is live if this
829 -- thing is live? Invariant: the binder
830 -- itself is always a member of
831 -- the dynamic set of its own LiveInfo
833 isLetBound (LetBound _ _) = True
834 isLetBound other = False
836 topLevelBound ImportBound = True
837 topLevelBound (LetBound TopLet _) = True
838 topLevelBound other = False
841 For a let(rec)-bound variable, x, we record LiveInfo, the set of
842 variables that are live if x is live. This LiveInfo comprises
843 (a) dynamic live variables (ones with a non-top-level binding)
844 (b) static live variabes (CAFs or things that refer to CAFs)
846 For "normal" variables (a) is just x alone. If x is a let-no-escaped
847 variable then x is represented by a code pointer and a stack pointer
848 (well, one for each stack). So all of the variables needed in the
849 execution of x are live if x is, and are therefore recorded in the
850 LetBound constructor; x itself *is* included.
852 The set of dynamic live variables is guaranteed ot have no further let-no-escaped
856 emptyLiveInfo :: LiveInfo
857 emptyLiveInfo = (emptyVarSet,emptyVarSet)
859 unitLiveVar :: Id -> LiveInfo
860 unitLiveVar lv = (unitVarSet lv, emptyVarSet)
862 unitLiveCaf :: Id -> LiveInfo
863 unitLiveCaf caf = (emptyVarSet, unitVarSet caf)
865 addLiveVar :: LiveInfo -> Id -> LiveInfo
866 addLiveVar (lvs, cafs) id = (lvs `extendVarSet` id, cafs)
868 unionLiveInfo :: LiveInfo -> LiveInfo -> LiveInfo
869 unionLiveInfo (lv1,caf1) (lv2,caf2) = (lv1 `unionVarSet` lv2, caf1 `unionVarSet` caf2)
871 mkSRT :: LiveInfo -> SRT
872 mkSRT (_, cafs) = SRTEntries cafs
874 getLiveVars :: LiveInfo -> StgLiveVars
875 getLiveVars (lvs, _) = lvs
879 The std monad functions:
881 initLne :: IdEnv HowBound -> LneM a -> a
882 initLne env m = m env emptyLiveInfo
886 {-# INLINE thenLne #-}
887 {-# INLINE returnLne #-}
889 returnLne :: a -> LneM a
890 returnLne e env lvs_cont = e
892 thenLne :: LneM a -> (a -> LneM b) -> LneM b
893 thenLne m k env lvs_cont
894 = k (m env lvs_cont) env lvs_cont
896 mapAndUnzipLne :: (a -> LneM (b,c)) -> [a] -> LneM ([b],[c])
897 mapAndUnzipLne f [] = returnLne ([],[])
898 mapAndUnzipLne f (x:xs)
899 = f x `thenLne` \ (r1, r2) ->
900 mapAndUnzipLne f xs `thenLne` \ (rs1, rs2) ->
901 returnLne (r1:rs1, r2:rs2)
903 mapAndUnzip3Lne :: (a -> LneM (b,c,d)) -> [a] -> LneM ([b],[c],[d])
904 mapAndUnzip3Lne f [] = returnLne ([],[],[])
905 mapAndUnzip3Lne f (x:xs)
906 = f x `thenLne` \ (r1, r2, r3) ->
907 mapAndUnzip3Lne f xs `thenLne` \ (rs1, rs2, rs3) ->
908 returnLne (r1:rs1, r2:rs2, r3:rs3)
910 mapAndUnzip4Lne :: (a -> LneM (b,c,d,e)) -> [a] -> LneM ([b],[c],[d],[e])
911 mapAndUnzip4Lne f [] = returnLne ([],[],[],[])
912 mapAndUnzip4Lne f (x:xs)
913 = f x `thenLne` \ (r1, r2, r3, r4) ->
914 mapAndUnzip4Lne f xs `thenLne` \ (rs1, rs2, rs3, rs4) ->
915 returnLne (r1:rs1, r2:rs2, r3:rs3, r4:rs4)
917 fixLne :: (a -> LneM a) -> LneM a
918 fixLne expr env lvs_cont
921 result = expr result env lvs_cont
924 Functions specific to this monad:
927 getVarsLiveInCont :: LneM LiveInfo
928 getVarsLiveInCont env lvs_cont = lvs_cont
930 setVarsLiveInCont :: LiveInfo -> LneM a -> LneM a
931 setVarsLiveInCont new_lvs_cont expr env lvs_cont
932 = expr env new_lvs_cont
934 extendVarEnvLne :: [(Id, HowBound)] -> LneM a -> LneM a
935 extendVarEnvLne ids_w_howbound expr env lvs_cont
936 = expr (extendVarEnvList env ids_w_howbound) lvs_cont
938 lookupVarLne :: Id -> LneM HowBound
939 lookupVarLne v env lvs_cont = returnLne (lookupBinding env v) env lvs_cont
941 getEnvLne :: LneM (IdEnv HowBound)
942 getEnvLne env lvs_cont = returnLne env env lvs_cont
944 lookupBinding :: IdEnv HowBound -> Id -> HowBound
945 lookupBinding env v = case lookupVarEnv env v of
947 Nothing -> ASSERT2( isGlobalId v, ppr v ) ImportBound
950 -- The result of lookupLiveVarsForSet, a set of live variables, is
951 -- only ever tacked onto a decorated expression. It is never used as
952 -- the basis of a control decision, which might give a black hole.
954 freeVarsToLiveVars :: FreeVarsInfo -> LneM LiveInfo
955 freeVarsToLiveVars fvs env live_in_cont
956 = returnLne live_info env live_in_cont
958 live_info = foldr unionLiveInfo live_in_cont lvs_from_fvs
959 lvs_from_fvs = map do_one (allFreeIds fvs)
961 do_one (v, how_bound)
963 ImportBound -> unitLiveCaf v -- Only CAF imports are
966 | mayHaveCafRefs (idCafInfo v) -> unitLiveCaf v
967 | otherwise -> emptyLiveInfo
969 LetBound (NestedLet lvs) _ -> lvs -- lvs already contains v
970 -- (see the invariant on NestedLet)
972 _lambda_or_case_binding -> unitLiveVar v -- Bound by lambda or case
975 %************************************************************************
977 \subsection[Free-var info]{Free variable information}
979 %************************************************************************
982 type FreeVarsInfo = VarEnv (Var, HowBound, StgBinderInfo)
983 -- The Var is so we can gather up the free variables
986 -- The HowBound info just saves repeated lookups;
987 -- we look up just once when we encounter the occurrence.
988 -- INVARIANT: Any ImportBound Ids are HaveCafRef Ids
989 -- Imported Ids without CAF refs are simply
990 -- not put in the FreeVarsInfo for an expression.
991 -- See singletonFVInfo and freeVarsToLiveVars
993 -- StgBinderInfo records how it occurs; notably, we
994 -- are interested in whether it only occurs in saturated
995 -- applications, because then we don't need to build a
997 -- If f is mapped to noBinderInfo, that means
998 -- that f *is* mentioned (else it wouldn't be in the
999 -- IdEnv at all), but perhaps in an unsaturated applications.
1001 -- All case/lambda-bound things are also mapped to
1002 -- noBinderInfo, since we aren't interested in their
1005 -- For ILX we track free var info for type variables too;
1006 -- hence VarEnv not IdEnv
1010 emptyFVInfo :: FreeVarsInfo
1011 emptyFVInfo = emptyVarEnv
1013 singletonFVInfo :: Id -> HowBound -> StgBinderInfo -> FreeVarsInfo
1014 -- Don't record non-CAF imports at all, to keep free-var sets small
1015 singletonFVInfo id ImportBound info
1016 | mayHaveCafRefs (idCafInfo id) = unitVarEnv id (id, ImportBound, info)
1017 | otherwise = emptyVarEnv
1018 singletonFVInfo id how_bound info = unitVarEnv id (id, how_bound, info)
1020 tyvarFVInfo :: TyVarSet -> FreeVarsInfo
1021 tyvarFVInfo tvs = foldVarSet add emptyFVInfo tvs
1023 add tv fvs = extendVarEnv fvs tv (tv, LambdaBound, noBinderInfo)
1024 -- Type variables must be lambda-bound
1026 unionFVInfo :: FreeVarsInfo -> FreeVarsInfo -> FreeVarsInfo
1027 unionFVInfo fv1 fv2 = plusVarEnv_C plusFVInfo fv1 fv2
1029 unionFVInfos :: [FreeVarsInfo] -> FreeVarsInfo
1030 unionFVInfos fvs = foldr unionFVInfo emptyFVInfo fvs
1032 minusFVBinders :: [Id] -> FreeVarsInfo -> FreeVarsInfo
1033 minusFVBinders vs fv = foldr minusFVBinder fv vs
1035 minusFVBinder :: Id -> FreeVarsInfo -> FreeVarsInfo
1036 minusFVBinder v fv | isId v && opt_RuntimeTypes
1037 = (fv `delVarEnv` v) `unionFVInfo`
1038 tyvarFVInfo (tyVarsOfType (idType v))
1039 | otherwise = fv `delVarEnv` v
1040 -- When removing a binder, remember to add its type variables
1041 -- c.f. CoreFVs.delBinderFV
1043 elementOfFVInfo :: Id -> FreeVarsInfo -> Bool
1044 elementOfFVInfo id fvs = maybeToBool (lookupVarEnv fvs id)
1046 lookupFVInfo :: FreeVarsInfo -> Id -> StgBinderInfo
1047 -- Find how the given Id is used.
1048 -- Externally visible things may be used any old how
1050 | isExternalName (idName id) = noBinderInfo
1051 | otherwise = case lookupVarEnv fvs id of
1052 Nothing -> noBinderInfo
1053 Just (_,_,info) -> info
1055 allFreeIds :: FreeVarsInfo -> [(Id,HowBound)] -- Both top level and non-top-level Ids
1056 allFreeIds fvs = [(id,how_bound) | (id,how_bound,_) <- varEnvElts fvs, isId id]
1058 -- Non-top-level things only, both type variables and ids
1059 -- (type variables only if opt_RuntimeTypes)
1060 getFVs :: FreeVarsInfo -> [Var]
1061 getFVs fvs = [id | (id, how_bound, _) <- varEnvElts fvs,
1062 not (topLevelBound how_bound) ]
1064 getFVSet :: FreeVarsInfo -> VarSet
1065 getFVSet fvs = mkVarSet (getFVs fvs)
1067 plusFVInfo (id1,hb1,info1) (id2,hb2,info2)
1068 = ASSERT (id1 == id2 && hb1 `check_eq_how_bound` hb2)
1069 (id1, hb1, combineStgBinderInfo info1 info2)
1072 -- The HowBound info for a variable in the FVInfo should be consistent
1073 check_eq_how_bound ImportBound ImportBound = True
1074 check_eq_how_bound LambdaBound LambdaBound = True
1075 check_eq_how_bound (LetBound li1 ar1) (LetBound li2 ar2) = ar1 == ar2 && check_eq_li li1 li2
1076 check_eq_how_bound hb1 hb2 = False
1078 check_eq_li (NestedLet _) (NestedLet _) = True
1079 check_eq_li TopLet TopLet = True
1080 check_eq_li li1 li2 = False
1086 filterStgBinders :: [Var] -> [Var]
1087 filterStgBinders bndrs
1088 | opt_RuntimeTypes = bndrs
1089 | otherwise = filter isId bndrs
1094 -- Ignore all notes except SCC
1095 myCollectBinders expr
1098 go bs (Lam b e) = go (b:bs) e
1099 go bs e@(Note (SCC _) _) = (reverse bs, e)
1100 go bs (Cast e co) = go bs e
1101 go bs (Note _ e) = go bs e
1102 go bs e = (reverse bs, e)
1104 myCollectArgs :: CoreExpr -> (Id, [CoreArg])
1105 -- We assume that we only have variables
1106 -- in the function position by now
1110 go (Var v) as = (v, as)
1111 go (App f a) as = go f (a:as)
1112 go (Note (SCC _) e) as = pprPanic "CoreToStg.myCollectArgs" (ppr expr)
1113 go (Cast e co) as = go e as
1114 go (Note n e) as = go e as
1115 go _ as = pprPanic "CoreToStg.myCollectArgs" (ppr expr)
1119 stgArity :: Id -> HowBound -> Arity
1120 stgArity f (LetBound _ arity) = arity
1121 stgArity f ImportBound = idArity f
1122 stgArity f LambdaBound = 0