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 TyCon ( isAlgTyCon )
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 | isPrimTyCon tc -> PrimAlt tc
414 | isHiBootTyCon tc -> look_for_better_tycon
415 | isAlgTyCon tc -> AlgAlt tc
416 | isFunTyCon tc -> PolyAlt
417 | otherwise -> pprPanic "mkStgAlts" (ppr tc)
421 -- Sometimes, the TyCon in the type of the scrutinee is an HiBootTyCon,
422 -- which may not have any constructors inside it. If so, then we
423 -- can get a better TyCon by grabbing the one from a constructor alternative
425 look_for_better_tycon
426 | ((DataAlt con, _, _) : _) <- data_alts =
427 AlgAlt (dataConTyCon con)
429 ASSERT(null data_alts)
432 (data_alts, _deflt) = findDefault alts
436 -- ---------------------------------------------------------------------------
438 -- ---------------------------------------------------------------------------
442 :: Maybe UpdateFlag -- Just upd <=> this application is
443 -- the rhs of a thunk binding
444 -- x = [...] \upd [] -> the_app
445 -- with specified update flag
447 -> [CoreArg] -- Arguments
448 -> LneM (StgExpr, FreeVarsInfo, EscVarsSet)
451 coreToStgApp maybe_thunk_body f args
452 = coreToStgArgs args `thenLne` \ (args', args_fvs) ->
453 lookupVarLne f `thenLne` \ how_bound ->
456 n_val_args = valArgCount args
457 not_letrec_bound = not (isLetBound how_bound)
459 = let fvs = singletonFVInfo f how_bound fun_occ in
460 -- e.g. (f :: a -> int) (x :: a)
461 -- Here the free variables are "f", "x" AND the type variable "a"
462 -- coreToStgArgs will deal with the arguments recursively
463 if opt_RuntimeTypes then
464 fvs `unionFVInfo` tyvarFVInfo (tyVarsOfType (idType f))
467 -- Mostly, the arity info of a function is in the fn's IdInfo
468 -- But new bindings introduced by CoreSat may not have no
469 -- arity info; it would do us no good anyway. For example:
470 -- let f = \ab -> e in f
471 -- No point in having correct arity info for f!
472 -- Hence the hasArity stuff below.
473 -- NB: f_arity is only consulted for LetBound things
474 f_arity = stgArity f how_bound
475 saturated = f_arity <= n_val_args
478 | not_letrec_bound = noBinderInfo -- Uninteresting variable
479 | f_arity > 0 && saturated = stgSatOcc -- Saturated or over-saturated function call
480 | otherwise = stgUnsatOcc -- Unsaturated function or thunk
483 | not_letrec_bound = emptyVarSet -- Only letrec-bound escapees are interesting
484 | f_arity == n_val_args = emptyVarSet -- A function *or thunk* with an exactly
485 -- saturated call doesn't escape
486 -- (let-no-escape applies to 'thunks' too)
488 | otherwise = unitVarSet f -- Inexact application; it does escape
490 -- At the moment of the call:
492 -- either the function is *not* let-no-escaped, in which case
493 -- nothing is live except live_in_cont
494 -- or the function *is* let-no-escaped in which case the
495 -- variables it uses are live, but still the function
496 -- itself is not. PS. In this case, the function's
497 -- live vars should already include those of the
498 -- continuation, but it does no harm to just union the
501 res_ty = exprType (mkApps (Var f) args)
502 app = case globalIdDetails f of
503 DataConWorkId dc | saturated -> StgConApp dc args'
504 PrimOpId op -> ASSERT( saturated )
505 StgOpApp (StgPrimOp op) args' res_ty
506 FCallId call -> ASSERT( saturated )
507 StgOpApp (StgFCallOp call (idUnique f)) args' res_ty
508 TickBoxOpId {} -> pprPanic "coreToStg TickBox" $ ppr (f,args')
509 _other -> StgApp f args'
514 fun_fvs `unionFVInfo` args_fvs,
515 fun_escs `unionVarSet` (getFVSet args_fvs)
516 -- All the free vars of the args are disqualified
517 -- from being let-no-escaped.
522 -- ---------------------------------------------------------------------------
524 -- This is the guy that turns applications into A-normal form
525 -- ---------------------------------------------------------------------------
527 coreToStgArgs :: [CoreArg] -> LneM ([StgArg], FreeVarsInfo)
529 = returnLne ([], emptyFVInfo)
531 coreToStgArgs (Type ty : args) -- Type argument
532 = coreToStgArgs args `thenLne` \ (args', fvs) ->
533 if opt_RuntimeTypes then
534 returnLne (StgTypeArg ty : args', fvs `unionFVInfo` tyvarFVInfo (tyVarsOfType ty))
536 returnLne (args', fvs)
538 coreToStgArgs (arg : args) -- Non-type argument
539 = coreToStgArgs args `thenLne` \ (stg_args, args_fvs) ->
540 coreToStgExpr arg `thenLne` \ (arg', arg_fvs, escs) ->
542 fvs = args_fvs `unionFVInfo` arg_fvs
543 stg_arg = case arg' of
544 StgApp v [] -> StgVarArg v
545 StgConApp con [] -> StgVarArg (dataConWorkId con)
546 StgLit lit -> StgLitArg lit
547 _ -> pprPanic "coreToStgArgs" (ppr arg)
549 -- WARNING: what if we have an argument like (v `cast` co)
550 -- where 'co' changes the representation type?
551 -- (This really only happens if co is unsafe.)
552 -- Then all the getArgAmode stuff in CgBindery will set the
553 -- cg_rep of the CgIdInfo based on the type of v, rather
554 -- than the type of 'co'.
555 -- This matters particularly when the function is a primop
557 -- Wanted: a better solution than this hacky warning
559 arg_ty = exprType arg
560 stg_arg_ty = stgArgType stg_arg
562 WARN( isUnLiftedType arg_ty /= isUnLiftedType stg_arg_ty,
563 ptext SLIT("Dangerous-looking argument. Probable cause: bad unsafeCoerce#") $$ ppr arg)
564 returnLne (stg_arg : stg_args, fvs)
567 -- ---------------------------------------------------------------------------
568 -- The magic for lets:
569 -- ---------------------------------------------------------------------------
572 :: Bool -- True <=> yes, we are let-no-escaping this let
573 -> CoreBind -- bindings
575 -> LneM (StgExpr, -- new let
576 FreeVarsInfo, -- variables free in the whole let
577 EscVarsSet, -- variables that escape from the whole let
578 Bool) -- True <=> none of the binders in the bindings
579 -- is among the escaping vars
581 coreToStgLet let_no_escape bind body
582 = fixLne (\ ~(_, _, _, _, _, rec_body_fvs, _, _) ->
584 -- Do the bindings, setting live_in_cont to empty if
585 -- we ain't in a let-no-escape world
586 getVarsLiveInCont `thenLne` \ live_in_cont ->
587 setVarsLiveInCont (if let_no_escape
590 (vars_bind rec_body_fvs bind)
591 `thenLne` \ ( bind2, bind_fvs, bind_escs, bind_lv_info, env_ext) ->
594 extendVarEnvLne env_ext (
595 coreToStgExpr body `thenLne` \(body2, body_fvs, body_escs) ->
596 freeVarsToLiveVars body_fvs `thenLne` \ body_lv_info ->
598 returnLne (bind2, bind_fvs, bind_escs, getLiveVars bind_lv_info,
599 body2, body_fvs, body_escs, getLiveVars body_lv_info)
602 ) `thenLne` (\ (bind2, bind_fvs, bind_escs, bind_lvs,
603 body2, body_fvs, body_escs, body_lvs) ->
606 -- Compute the new let-expression
608 new_let | let_no_escape = StgLetNoEscape live_in_whole_let bind_lvs bind2 body2
609 | otherwise = StgLet bind2 body2
612 = binders `minusFVBinders` (bind_fvs `unionFVInfo` body_fvs)
615 = bind_lvs `unionVarSet` (body_lvs `delVarSetList` binders)
617 real_bind_escs = if let_no_escape then
621 -- Everything escapes which is free in the bindings
623 let_escs = (real_bind_escs `unionVarSet` body_escs) `delVarSetList` binders
625 all_escs = bind_escs `unionVarSet` body_escs -- Still includes binders of
628 no_binder_escapes = isEmptyVarSet (set_of_binders `intersectVarSet` all_escs)
631 -- Debugging code as requested by Andrew Kennedy
632 checked_no_binder_escapes
633 | not no_binder_escapes && any is_join_var binders
634 = pprTrace "Interesting! A join var that isn't let-no-escaped" (ppr binders)
636 | otherwise = no_binder_escapes
638 checked_no_binder_escapes = no_binder_escapes
641 -- Mustn't depend on the passed-in let_no_escape flag, since
642 -- no_binder_escapes is used by the caller to derive the flag!
648 checked_no_binder_escapes
651 set_of_binders = mkVarSet binders
652 binders = bindersOf bind
654 mk_binding bind_lv_info binder rhs
655 = (binder, LetBound (NestedLet live_vars) (manifestArity rhs))
657 live_vars | let_no_escape = addLiveVar bind_lv_info binder
658 | otherwise = unitLiveVar binder
659 -- c.f. the invariant on NestedLet
661 vars_bind :: FreeVarsInfo -- Free var info for body of binding
665 EscVarsSet, -- free vars; escapee vars
666 LiveInfo, -- Vars and CAFs live in binding
667 [(Id, HowBound)]) -- extension to environment
670 vars_bind body_fvs (NonRec binder rhs)
671 = coreToStgRhs body_fvs [] (binder,rhs)
672 `thenLne` \ (rhs2, bind_fvs, bind_lv_info, escs) ->
674 env_ext_item = mk_binding bind_lv_info binder rhs
676 returnLne (StgNonRec binder rhs2,
677 bind_fvs, escs, bind_lv_info, [env_ext_item])
680 vars_bind body_fvs (Rec pairs)
681 = fixLne (\ ~(_, rec_rhs_fvs, _, bind_lv_info, _) ->
683 rec_scope_fvs = unionFVInfo body_fvs rec_rhs_fvs
684 binders = map fst pairs
685 env_ext = [ mk_binding bind_lv_info b rhs
688 extendVarEnvLne env_ext (
689 mapAndUnzip4Lne (coreToStgRhs rec_scope_fvs binders) pairs
690 `thenLne` \ (rhss2, fvss, lv_infos, escss) ->
692 bind_fvs = unionFVInfos fvss
693 bind_lv_info = foldr unionLiveInfo emptyLiveInfo lv_infos
694 escs = unionVarSets escss
696 returnLne (StgRec (binders `zip` rhss2),
697 bind_fvs, escs, bind_lv_info, env_ext)
701 is_join_var :: Id -> Bool
702 -- A hack (used only for compiler debuggging) to tell if
703 -- a variable started life as a join point ($j)
704 is_join_var j = occNameString (getOccName j) == "$j"
708 coreToStgRhs :: FreeVarsInfo -- Free var info for the scope of the binding
711 -> LneM (StgRhs, FreeVarsInfo, LiveInfo, EscVarsSet)
713 coreToStgRhs scope_fv_info binders (bndr, rhs)
714 = coreToStgExpr rhs `thenLne` \ (new_rhs, rhs_fvs, rhs_escs) ->
715 getEnvLne `thenLne` \ env ->
716 freeVarsToLiveVars (binders `minusFVBinders` rhs_fvs) `thenLne` \ lv_info ->
717 returnLne (mkStgRhs rhs_fvs (mkSRT lv_info) bndr_info new_rhs,
718 rhs_fvs, lv_info, rhs_escs)
720 bndr_info = lookupFVInfo scope_fv_info bndr
722 mkStgRhs :: FreeVarsInfo -> SRT -> StgBinderInfo -> StgExpr -> StgRhs
724 mkStgRhs rhs_fvs srt binder_info (StgConApp con args)
725 = StgRhsCon noCCS con args
727 mkStgRhs rhs_fvs srt binder_info (StgLam _ bndrs body)
728 = StgRhsClosure noCCS binder_info
733 mkStgRhs rhs_fvs srt binder_info rhs
734 = StgRhsClosure noCCS binder_info
740 SDM: disabled. Eval/Apply can't handle functions with arity zero very
741 well; and making these into simple non-updatable thunks breaks other
742 assumptions (namely that they will be entered only once).
744 upd_flag | isPAP env rhs = ReEntrant
745 | otherwise = Updatable
749 upd = if isOnceDem dem
750 then (if isNotTop toplev
751 then SingleEntry -- HA! Paydirt for "dem"
754 trace "WARNING: SE CAFs unsupported, forcing UPD instead" $
758 -- For now we forbid SingleEntry CAFs; they tickle the
759 -- ASSERT in rts/Storage.c line 215 at newCAF() re mut_link,
760 -- and I don't understand why. There's only one SE_CAF (well,
761 -- only one that tickled a great gaping bug in an earlier attempt
762 -- at ClosureInfo.getEntryConvention) in the whole of nofib,
763 -- specifically Main.lvl6 in spectral/cryptarithm2.
764 -- So no great loss. KSW 2000-07.
768 Detect thunks which will reduce immediately to PAPs, and make them
769 non-updatable. This has several advantages:
771 - the non-updatable thunk behaves exactly like the PAP,
773 - the thunk is more efficient to enter, because it is
774 specialised to the task.
776 - we save one update frame, one stg_update_PAP, one update
777 and lots of PAP_enters.
779 - in the case where the thunk is top-level, we save building
780 a black hole and futhermore the thunk isn't considered to
781 be a CAF any more, so it doesn't appear in any SRTs.
783 We do it here, because the arity information is accurate, and we need
784 to do it before the SRT pass to save the SRT entries associated with
787 isPAP env (StgApp f args) = listLengthCmp args arity == LT -- idArity f > length args
789 arity = stgArity f (lookupBinding env f)
793 %************************************************************************
795 \subsection[LNE-monad]{A little monad for this let-no-escaping pass}
797 %************************************************************************
799 There's a lot of stuff to pass around, so we use this @LneM@ monad to
800 help. All the stuff here is only passed *down*.
803 type LneM a = IdEnv HowBound
804 -> LiveInfo -- Vars and CAFs live in continuation
807 type LiveInfo = (StgLiveVars, -- Dynamic live variables;
808 -- i.e. ones with a nested (non-top-level) binding
809 CafSet) -- Static live variables;
810 -- i.e. top-level variables that are CAFs or refer to them
812 type EscVarsSet = IdSet
816 = ImportBound -- Used only as a response to lookupBinding; never
817 -- exists in the range of the (IdEnv HowBound)
819 | LetBound -- A let(rec) in this module
820 LetInfo -- Whether top level or nested
821 Arity -- Its arity (local Ids don't have arity info at this point)
823 | LambdaBound -- Used for both lambda and case
826 = TopLet -- top level things
827 | NestedLet LiveInfo -- For nested things, what is live if this
828 -- thing is live? Invariant: the binder
829 -- itself is always a member of
830 -- the dynamic set of its own LiveInfo
832 isLetBound (LetBound _ _) = True
833 isLetBound other = False
835 topLevelBound ImportBound = True
836 topLevelBound (LetBound TopLet _) = True
837 topLevelBound other = False
840 For a let(rec)-bound variable, x, we record LiveInfo, the set of
841 variables that are live if x is live. This LiveInfo comprises
842 (a) dynamic live variables (ones with a non-top-level binding)
843 (b) static live variabes (CAFs or things that refer to CAFs)
845 For "normal" variables (a) is just x alone. If x is a let-no-escaped
846 variable then x is represented by a code pointer and a stack pointer
847 (well, one for each stack). So all of the variables needed in the
848 execution of x are live if x is, and are therefore recorded in the
849 LetBound constructor; x itself *is* included.
851 The set of dynamic live variables is guaranteed ot have no further let-no-escaped
855 emptyLiveInfo :: LiveInfo
856 emptyLiveInfo = (emptyVarSet,emptyVarSet)
858 unitLiveVar :: Id -> LiveInfo
859 unitLiveVar lv = (unitVarSet lv, emptyVarSet)
861 unitLiveCaf :: Id -> LiveInfo
862 unitLiveCaf caf = (emptyVarSet, unitVarSet caf)
864 addLiveVar :: LiveInfo -> Id -> LiveInfo
865 addLiveVar (lvs, cafs) id = (lvs `extendVarSet` id, cafs)
867 unionLiveInfo :: LiveInfo -> LiveInfo -> LiveInfo
868 unionLiveInfo (lv1,caf1) (lv2,caf2) = (lv1 `unionVarSet` lv2, caf1 `unionVarSet` caf2)
870 mkSRT :: LiveInfo -> SRT
871 mkSRT (_, cafs) = SRTEntries cafs
873 getLiveVars :: LiveInfo -> StgLiveVars
874 getLiveVars (lvs, _) = lvs
878 The std monad functions:
880 initLne :: IdEnv HowBound -> LneM a -> a
881 initLne env m = m env emptyLiveInfo
885 {-# INLINE thenLne #-}
886 {-# INLINE returnLne #-}
888 returnLne :: a -> LneM a
889 returnLne e env lvs_cont = e
891 thenLne :: LneM a -> (a -> LneM b) -> LneM b
892 thenLne m k env lvs_cont
893 = k (m env lvs_cont) env lvs_cont
895 mapAndUnzipLne :: (a -> LneM (b,c)) -> [a] -> LneM ([b],[c])
896 mapAndUnzipLne f [] = returnLne ([],[])
897 mapAndUnzipLne f (x:xs)
898 = f x `thenLne` \ (r1, r2) ->
899 mapAndUnzipLne f xs `thenLne` \ (rs1, rs2) ->
900 returnLne (r1:rs1, r2:rs2)
902 mapAndUnzip3Lne :: (a -> LneM (b,c,d)) -> [a] -> LneM ([b],[c],[d])
903 mapAndUnzip3Lne f [] = returnLne ([],[],[])
904 mapAndUnzip3Lne f (x:xs)
905 = f x `thenLne` \ (r1, r2, r3) ->
906 mapAndUnzip3Lne f xs `thenLne` \ (rs1, rs2, rs3) ->
907 returnLne (r1:rs1, r2:rs2, r3:rs3)
909 mapAndUnzip4Lne :: (a -> LneM (b,c,d,e)) -> [a] -> LneM ([b],[c],[d],[e])
910 mapAndUnzip4Lne f [] = returnLne ([],[],[],[])
911 mapAndUnzip4Lne f (x:xs)
912 = f x `thenLne` \ (r1, r2, r3, r4) ->
913 mapAndUnzip4Lne f xs `thenLne` \ (rs1, rs2, rs3, rs4) ->
914 returnLne (r1:rs1, r2:rs2, r3:rs3, r4:rs4)
916 fixLne :: (a -> LneM a) -> LneM a
917 fixLne expr env lvs_cont
920 result = expr result env lvs_cont
923 Functions specific to this monad:
926 getVarsLiveInCont :: LneM LiveInfo
927 getVarsLiveInCont env lvs_cont = lvs_cont
929 setVarsLiveInCont :: LiveInfo -> LneM a -> LneM a
930 setVarsLiveInCont new_lvs_cont expr env lvs_cont
931 = expr env new_lvs_cont
933 extendVarEnvLne :: [(Id, HowBound)] -> LneM a -> LneM a
934 extendVarEnvLne ids_w_howbound expr env lvs_cont
935 = expr (extendVarEnvList env ids_w_howbound) lvs_cont
937 lookupVarLne :: Id -> LneM HowBound
938 lookupVarLne v env lvs_cont = returnLne (lookupBinding env v) env lvs_cont
940 getEnvLne :: LneM (IdEnv HowBound)
941 getEnvLne env lvs_cont = returnLne env env lvs_cont
943 lookupBinding :: IdEnv HowBound -> Id -> HowBound
944 lookupBinding env v = case lookupVarEnv env v of
946 Nothing -> ASSERT2( isGlobalId v, ppr v ) ImportBound
949 -- The result of lookupLiveVarsForSet, a set of live variables, is
950 -- only ever tacked onto a decorated expression. It is never used as
951 -- the basis of a control decision, which might give a black hole.
953 freeVarsToLiveVars :: FreeVarsInfo -> LneM LiveInfo
954 freeVarsToLiveVars fvs env live_in_cont
955 = returnLne live_info env live_in_cont
957 live_info = foldr unionLiveInfo live_in_cont lvs_from_fvs
958 lvs_from_fvs = map do_one (allFreeIds fvs)
960 do_one (v, how_bound)
962 ImportBound -> unitLiveCaf v -- Only CAF imports are
965 | mayHaveCafRefs (idCafInfo v) -> unitLiveCaf v
966 | otherwise -> emptyLiveInfo
968 LetBound (NestedLet lvs) _ -> lvs -- lvs already contains v
969 -- (see the invariant on NestedLet)
971 _lambda_or_case_binding -> unitLiveVar v -- Bound by lambda or case
974 %************************************************************************
976 \subsection[Free-var info]{Free variable information}
978 %************************************************************************
981 type FreeVarsInfo = VarEnv (Var, HowBound, StgBinderInfo)
982 -- The Var is so we can gather up the free variables
985 -- The HowBound info just saves repeated lookups;
986 -- we look up just once when we encounter the occurrence.
987 -- INVARIANT: Any ImportBound Ids are HaveCafRef Ids
988 -- Imported Ids without CAF refs are simply
989 -- not put in the FreeVarsInfo for an expression.
990 -- See singletonFVInfo and freeVarsToLiveVars
992 -- StgBinderInfo records how it occurs; notably, we
993 -- are interested in whether it only occurs in saturated
994 -- applications, because then we don't need to build a
996 -- If f is mapped to noBinderInfo, that means
997 -- that f *is* mentioned (else it wouldn't be in the
998 -- IdEnv at all), but perhaps in an unsaturated applications.
1000 -- All case/lambda-bound things are also mapped to
1001 -- noBinderInfo, since we aren't interested in their
1004 -- For ILX we track free var info for type variables too;
1005 -- hence VarEnv not IdEnv
1009 emptyFVInfo :: FreeVarsInfo
1010 emptyFVInfo = emptyVarEnv
1012 singletonFVInfo :: Id -> HowBound -> StgBinderInfo -> FreeVarsInfo
1013 -- Don't record non-CAF imports at all, to keep free-var sets small
1014 singletonFVInfo id ImportBound info
1015 | mayHaveCafRefs (idCafInfo id) = unitVarEnv id (id, ImportBound, info)
1016 | otherwise = emptyVarEnv
1017 singletonFVInfo id how_bound info = unitVarEnv id (id, how_bound, info)
1019 tyvarFVInfo :: TyVarSet -> FreeVarsInfo
1020 tyvarFVInfo tvs = foldVarSet add emptyFVInfo tvs
1022 add tv fvs = extendVarEnv fvs tv (tv, LambdaBound, noBinderInfo)
1023 -- Type variables must be lambda-bound
1025 unionFVInfo :: FreeVarsInfo -> FreeVarsInfo -> FreeVarsInfo
1026 unionFVInfo fv1 fv2 = plusVarEnv_C plusFVInfo fv1 fv2
1028 unionFVInfos :: [FreeVarsInfo] -> FreeVarsInfo
1029 unionFVInfos fvs = foldr unionFVInfo emptyFVInfo fvs
1031 minusFVBinders :: [Id] -> FreeVarsInfo -> FreeVarsInfo
1032 minusFVBinders vs fv = foldr minusFVBinder fv vs
1034 minusFVBinder :: Id -> FreeVarsInfo -> FreeVarsInfo
1035 minusFVBinder v fv | isId v && opt_RuntimeTypes
1036 = (fv `delVarEnv` v) `unionFVInfo`
1037 tyvarFVInfo (tyVarsOfType (idType v))
1038 | otherwise = fv `delVarEnv` v
1039 -- When removing a binder, remember to add its type variables
1040 -- c.f. CoreFVs.delBinderFV
1042 elementOfFVInfo :: Id -> FreeVarsInfo -> Bool
1043 elementOfFVInfo id fvs = maybeToBool (lookupVarEnv fvs id)
1045 lookupFVInfo :: FreeVarsInfo -> Id -> StgBinderInfo
1046 -- Find how the given Id is used.
1047 -- Externally visible things may be used any old how
1049 | isExternalName (idName id) = noBinderInfo
1050 | otherwise = case lookupVarEnv fvs id of
1051 Nothing -> noBinderInfo
1052 Just (_,_,info) -> info
1054 allFreeIds :: FreeVarsInfo -> [(Id,HowBound)] -- Both top level and non-top-level Ids
1055 allFreeIds fvs = [(id,how_bound) | (id,how_bound,_) <- varEnvElts fvs, isId id]
1057 -- Non-top-level things only, both type variables and ids
1058 -- (type variables only if opt_RuntimeTypes)
1059 getFVs :: FreeVarsInfo -> [Var]
1060 getFVs fvs = [id | (id, how_bound, _) <- varEnvElts fvs,
1061 not (topLevelBound how_bound) ]
1063 getFVSet :: FreeVarsInfo -> VarSet
1064 getFVSet fvs = mkVarSet (getFVs fvs)
1066 plusFVInfo (id1,hb1,info1) (id2,hb2,info2)
1067 = ASSERT (id1 == id2 && hb1 `check_eq_how_bound` hb2)
1068 (id1, hb1, combineStgBinderInfo info1 info2)
1071 -- The HowBound info for a variable in the FVInfo should be consistent
1072 check_eq_how_bound ImportBound ImportBound = True
1073 check_eq_how_bound LambdaBound LambdaBound = True
1074 check_eq_how_bound (LetBound li1 ar1) (LetBound li2 ar2) = ar1 == ar2 && check_eq_li li1 li2
1075 check_eq_how_bound hb1 hb2 = False
1077 check_eq_li (NestedLet _) (NestedLet _) = True
1078 check_eq_li TopLet TopLet = True
1079 check_eq_li li1 li2 = False
1085 filterStgBinders :: [Var] -> [Var]
1086 filterStgBinders bndrs
1087 | opt_RuntimeTypes = bndrs
1088 | otherwise = filter isId bndrs
1093 -- Ignore all notes except SCC
1094 myCollectBinders expr
1097 go bs (Lam b e) = go (b:bs) e
1098 go bs e@(Note (SCC _) _) = (reverse bs, e)
1099 go bs (Cast e co) = go bs e
1100 go bs (Note _ e) = go bs e
1101 go bs e = (reverse bs, e)
1103 myCollectArgs :: CoreExpr -> (Id, [CoreArg])
1104 -- We assume that we only have variables
1105 -- in the function position by now
1109 go (Var v) as = (v, as)
1110 go (App f a) as = go f (a:as)
1111 go (Note (SCC _) e) as = pprPanic "CoreToStg.myCollectArgs" (ppr expr)
1112 go (Cast e co) as = go e as
1113 go (Note n e) as = go e as
1114 go _ as = pprPanic "CoreToStg.myCollectArgs" (ppr expr)
1118 stgArity :: Id -> HowBound -> Arity
1119 stgArity f (LetBound _ arity) = arity
1120 stgArity f ImportBound = idArity f
1121 stgArity f LambdaBound = 0