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 (Note (TickBox m n) expr)
321 = coreToStgExpr expr `thenLne` ( \ (expr2, fvs, escs) ->
322 returnLne (StgTick m n expr2, fvs, escs) )
324 -- BinaryTickBox'es are are removed by the CorePrep pass.
326 coreToStgExpr expr@(Note (BinaryTickBox m t e) _)
327 = pprPanic "coreToStgExpr: " (ppr expr)
329 coreToStgExpr (Note other_note expr)
332 coreToStgExpr (Cast expr co)
335 -- Cases require a little more real work.
337 coreToStgExpr (Case scrut bndr _ alts)
338 = extendVarEnvLne [(bndr, LambdaBound)] (
339 mapAndUnzip3Lne vars_alt alts `thenLne` \ (alts2, fvs_s, escs_s) ->
342 unionVarSets escs_s )
343 ) `thenLne` \ (alts2, alts_fvs, alts_escs) ->
345 -- Determine whether the default binder is dead or not
346 -- This helps the code generator to avoid generating an assignment
347 -- for the case binder (is extremely rare cases) ToDo: remove.
348 bndr' | bndr `elementOfFVInfo` alts_fvs = bndr
349 | otherwise = bndr `setIdOccInfo` IAmDead
351 -- Don't consider the default binder as being 'live in alts',
352 -- since this is from the point of view of the case expr, where
353 -- the default binder is not free.
354 alts_fvs_wo_bndr = bndr `minusFVBinder` alts_fvs
355 alts_escs_wo_bndr = alts_escs `delVarSet` bndr
358 freeVarsToLiveVars alts_fvs_wo_bndr `thenLne` \ alts_lv_info ->
360 -- We tell the scrutinee that everything
361 -- live in the alts is live in it, too.
362 setVarsLiveInCont alts_lv_info (
363 coreToStgExpr scrut `thenLne` \ (scrut2, scrut_fvs, scrut_escs) ->
364 freeVarsToLiveVars scrut_fvs `thenLne` \ scrut_lv_info ->
365 returnLne (scrut2, scrut_fvs, scrut_escs, scrut_lv_info)
367 `thenLne` \ (scrut2, scrut_fvs, scrut_escs, scrut_lv_info) ->
370 StgCase scrut2 (getLiveVars scrut_lv_info)
371 (getLiveVars alts_lv_info)
374 (mkStgAltType (idType bndr) alts)
376 scrut_fvs `unionFVInfo` alts_fvs_wo_bndr,
377 alts_escs_wo_bndr `unionVarSet` getFVSet scrut_fvs
378 -- You might think we should have scrut_escs, not
379 -- (getFVSet scrut_fvs), but actually we can't call, and
380 -- then return from, a let-no-escape thing.
383 vars_alt (con, binders, rhs)
384 = let -- Remove type variables
385 binders' = filterStgBinders binders
387 extendVarEnvLne [(b, LambdaBound) | b <- binders'] $
388 coreToStgExpr rhs `thenLne` \ (rhs2, rhs_fvs, rhs_escs) ->
390 -- Records whether each param is used in the RHS
391 good_use_mask = [ b `elementOfFVInfo` rhs_fvs | b <- binders' ]
393 returnLne ( (con, binders', good_use_mask, rhs2),
394 binders' `minusFVBinders` rhs_fvs,
395 rhs_escs `delVarSetList` binders' )
396 -- ToDo: remove the delVarSet;
397 -- since escs won't include any of these binders
400 Lets not only take quite a bit of work, but this is where we convert
401 then to let-no-escapes, if we wish.
403 (Meanwhile, we don't expect to see let-no-escapes...)
405 coreToStgExpr (Let bind body)
406 = fixLne (\ ~(_, _, _, no_binder_escapes) ->
407 coreToStgLet no_binder_escapes bind body
408 ) `thenLne` \ (new_let, fvs, escs, _) ->
410 returnLne (new_let, fvs, escs)
414 mkStgAltType scrut_ty alts
415 = case splitTyConApp_maybe (repType scrut_ty) of
416 Just (tc,_) | isUnboxedTupleTyCon tc -> UbxTupAlt tc
417 | isPrimTyCon tc -> PrimAlt tc
418 | isHiBootTyCon tc -> look_for_better_tycon
419 | isAlgTyCon tc -> AlgAlt tc
420 | isFunTyCon tc -> PolyAlt
421 | otherwise -> pprPanic "mkStgAlts" (ppr tc)
425 -- Sometimes, the TyCon in the type of the scrutinee is an HiBootTyCon,
426 -- which may not have any constructors inside it. If so, then we
427 -- can get a better TyCon by grabbing the one from a constructor alternative
429 look_for_better_tycon
430 | ((DataAlt con, _, _) : _) <- data_alts =
431 AlgAlt (dataConTyCon con)
433 ASSERT(null data_alts)
436 (data_alts, _deflt) = findDefault alts
440 -- ---------------------------------------------------------------------------
442 -- ---------------------------------------------------------------------------
446 :: Maybe UpdateFlag -- Just upd <=> this application is
447 -- the rhs of a thunk binding
448 -- x = [...] \upd [] -> the_app
449 -- with specified update flag
451 -> [CoreArg] -- Arguments
452 -> LneM (StgExpr, FreeVarsInfo, EscVarsSet)
454 coreToStgApp maybe_thunk_body f args
455 = coreToStgArgs args `thenLne` \ (args', args_fvs) ->
456 lookupVarLne f `thenLne` \ how_bound ->
459 n_val_args = valArgCount args
460 not_letrec_bound = not (isLetBound how_bound)
462 = let fvs = singletonFVInfo f how_bound fun_occ in
463 -- e.g. (f :: a -> int) (x :: a)
464 -- Here the free variables are "f", "x" AND the type variable "a"
465 -- coreToStgArgs will deal with the arguments recursively
466 if opt_RuntimeTypes then
467 fvs `unionFVInfo` tyvarFVInfo (tyVarsOfType (idType f))
470 -- Mostly, the arity info of a function is in the fn's IdInfo
471 -- But new bindings introduced by CoreSat may not have no
472 -- arity info; it would do us no good anyway. For example:
473 -- let f = \ab -> e in f
474 -- No point in having correct arity info for f!
475 -- Hence the hasArity stuff below.
476 -- NB: f_arity is only consulted for LetBound things
477 f_arity = stgArity f how_bound
478 saturated = f_arity <= n_val_args
481 | not_letrec_bound = noBinderInfo -- Uninteresting variable
482 | f_arity > 0 && saturated = stgSatOcc -- Saturated or over-saturated function call
483 | otherwise = stgUnsatOcc -- Unsaturated function or thunk
486 | not_letrec_bound = emptyVarSet -- Only letrec-bound escapees are interesting
487 | f_arity == n_val_args = emptyVarSet -- A function *or thunk* with an exactly
488 -- saturated call doesn't escape
489 -- (let-no-escape applies to 'thunks' too)
491 | otherwise = unitVarSet f -- Inexact application; it does escape
493 -- At the moment of the call:
495 -- either the function is *not* let-no-escaped, in which case
496 -- nothing is live except live_in_cont
497 -- or the function *is* let-no-escaped in which case the
498 -- variables it uses are live, but still the function
499 -- itself is not. PS. In this case, the function's
500 -- live vars should already include those of the
501 -- continuation, but it does no harm to just union the
504 res_ty = exprType (mkApps (Var f) args)
505 app = case globalIdDetails f of
506 DataConWorkId dc | saturated -> StgConApp dc args'
507 PrimOpId op -> ASSERT( saturated )
508 StgOpApp (StgPrimOp op) args' res_ty
509 FCallId call -> ASSERT( saturated )
510 StgOpApp (StgFCallOp call (idUnique f)) args' res_ty
511 _other -> StgApp f args'
516 fun_fvs `unionFVInfo` args_fvs,
517 fun_escs `unionVarSet` (getFVSet args_fvs)
518 -- All the free vars of the args are disqualified
519 -- from being let-no-escaped.
524 -- ---------------------------------------------------------------------------
526 -- This is the guy that turns applications into A-normal form
527 -- ---------------------------------------------------------------------------
529 coreToStgArgs :: [CoreArg] -> LneM ([StgArg], FreeVarsInfo)
531 = returnLne ([], emptyFVInfo)
533 coreToStgArgs (Type ty : args) -- Type argument
534 = coreToStgArgs args `thenLne` \ (args', fvs) ->
535 if opt_RuntimeTypes then
536 returnLne (StgTypeArg ty : args', fvs `unionFVInfo` tyvarFVInfo (tyVarsOfType ty))
538 returnLne (args', fvs)
540 coreToStgArgs (arg : args) -- Non-type argument
541 = coreToStgArgs args `thenLne` \ (stg_args, args_fvs) ->
542 coreToStgExpr arg `thenLne` \ (arg', arg_fvs, escs) ->
544 fvs = args_fvs `unionFVInfo` arg_fvs
545 stg_arg = case arg' of
546 StgApp v [] -> StgVarArg v
547 StgConApp con [] -> StgVarArg (dataConWorkId con)
548 StgLit lit -> StgLitArg lit
549 _ -> pprPanic "coreToStgArgs" (ppr arg)
551 -- WARNING: what if we have an argument like (v `cast` co)
552 -- where 'co' changes the representation type?
553 -- (This really only happens if co is unsafe.)
554 -- Then all the getArgAmode stuff in CgBindery will set the
555 -- cg_rep of the CgIdInfo based on the type of v, rather
556 -- than the type of 'co'.
557 -- This matters particularly when the function is a primop
559 -- Wanted: a better solution than this hacky warning
561 arg_ty = exprType arg
562 stg_arg_ty = stgArgType stg_arg
564 WARN( isUnLiftedType arg_ty /= isUnLiftedType stg_arg_ty,
565 ptext SLIT("Dangerous-looking argument. Probable cause: bad unsafeCoerce#") $$ ppr arg)
566 returnLne (stg_arg : stg_args, fvs)
569 -- ---------------------------------------------------------------------------
570 -- The magic for lets:
571 -- ---------------------------------------------------------------------------
574 :: Bool -- True <=> yes, we are let-no-escaping this let
575 -> CoreBind -- bindings
577 -> LneM (StgExpr, -- new let
578 FreeVarsInfo, -- variables free in the whole let
579 EscVarsSet, -- variables that escape from the whole let
580 Bool) -- True <=> none of the binders in the bindings
581 -- is among the escaping vars
583 coreToStgLet let_no_escape bind body
584 = fixLne (\ ~(_, _, _, _, _, rec_body_fvs, _, _) ->
586 -- Do the bindings, setting live_in_cont to empty if
587 -- we ain't in a let-no-escape world
588 getVarsLiveInCont `thenLne` \ live_in_cont ->
589 setVarsLiveInCont (if let_no_escape
592 (vars_bind rec_body_fvs bind)
593 `thenLne` \ ( bind2, bind_fvs, bind_escs, bind_lv_info, env_ext) ->
596 extendVarEnvLne env_ext (
597 coreToStgExpr body `thenLne` \(body2, body_fvs, body_escs) ->
598 freeVarsToLiveVars body_fvs `thenLne` \ body_lv_info ->
600 returnLne (bind2, bind_fvs, bind_escs, getLiveVars bind_lv_info,
601 body2, body_fvs, body_escs, getLiveVars body_lv_info)
604 ) `thenLne` (\ (bind2, bind_fvs, bind_escs, bind_lvs,
605 body2, body_fvs, body_escs, body_lvs) ->
608 -- Compute the new let-expression
610 new_let | let_no_escape = StgLetNoEscape live_in_whole_let bind_lvs bind2 body2
611 | otherwise = StgLet bind2 body2
614 = binders `minusFVBinders` (bind_fvs `unionFVInfo` body_fvs)
617 = bind_lvs `unionVarSet` (body_lvs `delVarSetList` binders)
619 real_bind_escs = if let_no_escape then
623 -- Everything escapes which is free in the bindings
625 let_escs = (real_bind_escs `unionVarSet` body_escs) `delVarSetList` binders
627 all_escs = bind_escs `unionVarSet` body_escs -- Still includes binders of
630 no_binder_escapes = isEmptyVarSet (set_of_binders `intersectVarSet` all_escs)
633 -- Debugging code as requested by Andrew Kennedy
634 checked_no_binder_escapes
635 | not no_binder_escapes && any is_join_var binders
636 = pprTrace "Interesting! A join var that isn't let-no-escaped" (ppr binders)
638 | otherwise = no_binder_escapes
640 checked_no_binder_escapes = no_binder_escapes
643 -- Mustn't depend on the passed-in let_no_escape flag, since
644 -- no_binder_escapes is used by the caller to derive the flag!
650 checked_no_binder_escapes
653 set_of_binders = mkVarSet binders
654 binders = bindersOf bind
656 mk_binding bind_lv_info binder rhs
657 = (binder, LetBound (NestedLet live_vars) (manifestArity rhs))
659 live_vars | let_no_escape = addLiveVar bind_lv_info binder
660 | otherwise = unitLiveVar binder
661 -- c.f. the invariant on NestedLet
663 vars_bind :: FreeVarsInfo -- Free var info for body of binding
667 EscVarsSet, -- free vars; escapee vars
668 LiveInfo, -- Vars and CAFs live in binding
669 [(Id, HowBound)]) -- extension to environment
672 vars_bind body_fvs (NonRec binder rhs)
673 = coreToStgRhs body_fvs [] (binder,rhs)
674 `thenLne` \ (rhs2, bind_fvs, bind_lv_info, escs) ->
676 env_ext_item = mk_binding bind_lv_info binder rhs
678 returnLne (StgNonRec binder rhs2,
679 bind_fvs, escs, bind_lv_info, [env_ext_item])
682 vars_bind body_fvs (Rec pairs)
683 = fixLne (\ ~(_, rec_rhs_fvs, _, bind_lv_info, _) ->
685 rec_scope_fvs = unionFVInfo body_fvs rec_rhs_fvs
686 binders = map fst pairs
687 env_ext = [ mk_binding bind_lv_info b rhs
690 extendVarEnvLne env_ext (
691 mapAndUnzip4Lne (coreToStgRhs rec_scope_fvs binders) pairs
692 `thenLne` \ (rhss2, fvss, lv_infos, escss) ->
694 bind_fvs = unionFVInfos fvss
695 bind_lv_info = foldr unionLiveInfo emptyLiveInfo lv_infos
696 escs = unionVarSets escss
698 returnLne (StgRec (binders `zip` rhss2),
699 bind_fvs, escs, bind_lv_info, env_ext)
703 is_join_var :: Id -> Bool
704 -- A hack (used only for compiler debuggging) to tell if
705 -- a variable started life as a join point ($j)
706 is_join_var j = occNameString (getOccName j) == "$j"
710 coreToStgRhs :: FreeVarsInfo -- Free var info for the scope of the binding
713 -> LneM (StgRhs, FreeVarsInfo, LiveInfo, EscVarsSet)
715 coreToStgRhs scope_fv_info binders (bndr, rhs)
716 = coreToStgExpr rhs `thenLne` \ (new_rhs, rhs_fvs, rhs_escs) ->
717 getEnvLne `thenLne` \ env ->
718 freeVarsToLiveVars (binders `minusFVBinders` rhs_fvs) `thenLne` \ lv_info ->
719 returnLne (mkStgRhs rhs_fvs (mkSRT lv_info) bndr_info new_rhs,
720 rhs_fvs, lv_info, rhs_escs)
722 bndr_info = lookupFVInfo scope_fv_info bndr
724 mkStgRhs :: FreeVarsInfo -> SRT -> StgBinderInfo -> StgExpr -> StgRhs
726 mkStgRhs rhs_fvs srt binder_info (StgConApp con args)
727 = StgRhsCon noCCS con args
729 mkStgRhs rhs_fvs srt binder_info (StgLam _ bndrs body)
730 = StgRhsClosure noCCS binder_info
735 mkStgRhs rhs_fvs srt binder_info rhs
736 = StgRhsClosure noCCS binder_info
742 SDM: disabled. Eval/Apply can't handle functions with arity zero very
743 well; and making these into simple non-updatable thunks breaks other
744 assumptions (namely that they will be entered only once).
746 upd_flag | isPAP env rhs = ReEntrant
747 | otherwise = Updatable
751 upd = if isOnceDem dem
752 then (if isNotTop toplev
753 then SingleEntry -- HA! Paydirt for "dem"
756 trace "WARNING: SE CAFs unsupported, forcing UPD instead" $
760 -- For now we forbid SingleEntry CAFs; they tickle the
761 -- ASSERT in rts/Storage.c line 215 at newCAF() re mut_link,
762 -- and I don't understand why. There's only one SE_CAF (well,
763 -- only one that tickled a great gaping bug in an earlier attempt
764 -- at ClosureInfo.getEntryConvention) in the whole of nofib,
765 -- specifically Main.lvl6 in spectral/cryptarithm2.
766 -- So no great loss. KSW 2000-07.
770 Detect thunks which will reduce immediately to PAPs, and make them
771 non-updatable. This has several advantages:
773 - the non-updatable thunk behaves exactly like the PAP,
775 - the thunk is more efficient to enter, because it is
776 specialised to the task.
778 - we save one update frame, one stg_update_PAP, one update
779 and lots of PAP_enters.
781 - in the case where the thunk is top-level, we save building
782 a black hole and futhermore the thunk isn't considered to
783 be a CAF any more, so it doesn't appear in any SRTs.
785 We do it here, because the arity information is accurate, and we need
786 to do it before the SRT pass to save the SRT entries associated with
789 isPAP env (StgApp f args) = listLengthCmp args arity == LT -- idArity f > length args
791 arity = stgArity f (lookupBinding env f)
795 %************************************************************************
797 \subsection[LNE-monad]{A little monad for this let-no-escaping pass}
799 %************************************************************************
801 There's a lot of stuff to pass around, so we use this @LneM@ monad to
802 help. All the stuff here is only passed *down*.
805 type LneM a = IdEnv HowBound
806 -> LiveInfo -- Vars and CAFs live in continuation
809 type LiveInfo = (StgLiveVars, -- Dynamic live variables;
810 -- i.e. ones with a nested (non-top-level) binding
811 CafSet) -- Static live variables;
812 -- i.e. top-level variables that are CAFs or refer to them
814 type EscVarsSet = IdSet
818 = ImportBound -- Used only as a response to lookupBinding; never
819 -- exists in the range of the (IdEnv HowBound)
821 | LetBound -- A let(rec) in this module
822 LetInfo -- Whether top level or nested
823 Arity -- Its arity (local Ids don't have arity info at this point)
825 | LambdaBound -- Used for both lambda and case
828 = TopLet -- top level things
829 | NestedLet LiveInfo -- For nested things, what is live if this
830 -- thing is live? Invariant: the binder
831 -- itself is always a member of
832 -- the dynamic set of its own LiveInfo
834 isLetBound (LetBound _ _) = True
835 isLetBound other = False
837 topLevelBound ImportBound = True
838 topLevelBound (LetBound TopLet _) = True
839 topLevelBound other = False
842 For a let(rec)-bound variable, x, we record LiveInfo, the set of
843 variables that are live if x is live. This LiveInfo comprises
844 (a) dynamic live variables (ones with a non-top-level binding)
845 (b) static live variabes (CAFs or things that refer to CAFs)
847 For "normal" variables (a) is just x alone. If x is a let-no-escaped
848 variable then x is represented by a code pointer and a stack pointer
849 (well, one for each stack). So all of the variables needed in the
850 execution of x are live if x is, and are therefore recorded in the
851 LetBound constructor; x itself *is* included.
853 The set of dynamic live variables is guaranteed ot have no further let-no-escaped
857 emptyLiveInfo :: LiveInfo
858 emptyLiveInfo = (emptyVarSet,emptyVarSet)
860 unitLiveVar :: Id -> LiveInfo
861 unitLiveVar lv = (unitVarSet lv, emptyVarSet)
863 unitLiveCaf :: Id -> LiveInfo
864 unitLiveCaf caf = (emptyVarSet, unitVarSet caf)
866 addLiveVar :: LiveInfo -> Id -> LiveInfo
867 addLiveVar (lvs, cafs) id = (lvs `extendVarSet` id, cafs)
869 unionLiveInfo :: LiveInfo -> LiveInfo -> LiveInfo
870 unionLiveInfo (lv1,caf1) (lv2,caf2) = (lv1 `unionVarSet` lv2, caf1 `unionVarSet` caf2)
872 mkSRT :: LiveInfo -> SRT
873 mkSRT (_, cafs) = SRTEntries cafs
875 getLiveVars :: LiveInfo -> StgLiveVars
876 getLiveVars (lvs, _) = lvs
880 The std monad functions:
882 initLne :: IdEnv HowBound -> LneM a -> a
883 initLne env m = m env emptyLiveInfo
887 {-# INLINE thenLne #-}
888 {-# INLINE returnLne #-}
890 returnLne :: a -> LneM a
891 returnLne e env lvs_cont = e
893 thenLne :: LneM a -> (a -> LneM b) -> LneM b
894 thenLne m k env lvs_cont
895 = k (m env lvs_cont) env lvs_cont
897 mapAndUnzipLne :: (a -> LneM (b,c)) -> [a] -> LneM ([b],[c])
898 mapAndUnzipLne f [] = returnLne ([],[])
899 mapAndUnzipLne f (x:xs)
900 = f x `thenLne` \ (r1, r2) ->
901 mapAndUnzipLne f xs `thenLne` \ (rs1, rs2) ->
902 returnLne (r1:rs1, r2:rs2)
904 mapAndUnzip3Lne :: (a -> LneM (b,c,d)) -> [a] -> LneM ([b],[c],[d])
905 mapAndUnzip3Lne f [] = returnLne ([],[],[])
906 mapAndUnzip3Lne f (x:xs)
907 = f x `thenLne` \ (r1, r2, r3) ->
908 mapAndUnzip3Lne f xs `thenLne` \ (rs1, rs2, rs3) ->
909 returnLne (r1:rs1, r2:rs2, r3:rs3)
911 mapAndUnzip4Lne :: (a -> LneM (b,c,d,e)) -> [a] -> LneM ([b],[c],[d],[e])
912 mapAndUnzip4Lne f [] = returnLne ([],[],[],[])
913 mapAndUnzip4Lne f (x:xs)
914 = f x `thenLne` \ (r1, r2, r3, r4) ->
915 mapAndUnzip4Lne f xs `thenLne` \ (rs1, rs2, rs3, rs4) ->
916 returnLne (r1:rs1, r2:rs2, r3:rs3, r4:rs4)
918 fixLne :: (a -> LneM a) -> LneM a
919 fixLne expr env lvs_cont
922 result = expr result env lvs_cont
925 Functions specific to this monad:
928 getVarsLiveInCont :: LneM LiveInfo
929 getVarsLiveInCont env lvs_cont = lvs_cont
931 setVarsLiveInCont :: LiveInfo -> LneM a -> LneM a
932 setVarsLiveInCont new_lvs_cont expr env lvs_cont
933 = expr env new_lvs_cont
935 extendVarEnvLne :: [(Id, HowBound)] -> LneM a -> LneM a
936 extendVarEnvLne ids_w_howbound expr env lvs_cont
937 = expr (extendVarEnvList env ids_w_howbound) lvs_cont
939 lookupVarLne :: Id -> LneM HowBound
940 lookupVarLne v env lvs_cont = returnLne (lookupBinding env v) env lvs_cont
942 getEnvLne :: LneM (IdEnv HowBound)
943 getEnvLne env lvs_cont = returnLne env env lvs_cont
945 lookupBinding :: IdEnv HowBound -> Id -> HowBound
946 lookupBinding env v = case lookupVarEnv env v of
948 Nothing -> ASSERT2( isGlobalId v, ppr v ) ImportBound
951 -- The result of lookupLiveVarsForSet, a set of live variables, is
952 -- only ever tacked onto a decorated expression. It is never used as
953 -- the basis of a control decision, which might give a black hole.
955 freeVarsToLiveVars :: FreeVarsInfo -> LneM LiveInfo
956 freeVarsToLiveVars fvs env live_in_cont
957 = returnLne live_info env live_in_cont
959 live_info = foldr unionLiveInfo live_in_cont lvs_from_fvs
960 lvs_from_fvs = map do_one (allFreeIds fvs)
962 do_one (v, how_bound)
964 ImportBound -> unitLiveCaf v -- Only CAF imports are
967 | mayHaveCafRefs (idCafInfo v) -> unitLiveCaf v
968 | otherwise -> emptyLiveInfo
970 LetBound (NestedLet lvs) _ -> lvs -- lvs already contains v
971 -- (see the invariant on NestedLet)
973 _lambda_or_case_binding -> unitLiveVar v -- Bound by lambda or case
976 %************************************************************************
978 \subsection[Free-var info]{Free variable information}
980 %************************************************************************
983 type FreeVarsInfo = VarEnv (Var, HowBound, StgBinderInfo)
984 -- The Var is so we can gather up the free variables
987 -- The HowBound info just saves repeated lookups;
988 -- we look up just once when we encounter the occurrence.
989 -- INVARIANT: Any ImportBound Ids are HaveCafRef Ids
990 -- Imported Ids without CAF refs are simply
991 -- not put in the FreeVarsInfo for an expression.
992 -- See singletonFVInfo and freeVarsToLiveVars
994 -- StgBinderInfo records how it occurs; notably, we
995 -- are interested in whether it only occurs in saturated
996 -- applications, because then we don't need to build a
998 -- If f is mapped to noBinderInfo, that means
999 -- that f *is* mentioned (else it wouldn't be in the
1000 -- IdEnv at all), but perhaps in an unsaturated applications.
1002 -- All case/lambda-bound things are also mapped to
1003 -- noBinderInfo, since we aren't interested in their
1006 -- For ILX we track free var info for type variables too;
1007 -- hence VarEnv not IdEnv
1011 emptyFVInfo :: FreeVarsInfo
1012 emptyFVInfo = emptyVarEnv
1014 singletonFVInfo :: Id -> HowBound -> StgBinderInfo -> FreeVarsInfo
1015 -- Don't record non-CAF imports at all, to keep free-var sets small
1016 singletonFVInfo id ImportBound info
1017 | mayHaveCafRefs (idCafInfo id) = unitVarEnv id (id, ImportBound, info)
1018 | otherwise = emptyVarEnv
1019 singletonFVInfo id how_bound info = unitVarEnv id (id, how_bound, info)
1021 tyvarFVInfo :: TyVarSet -> FreeVarsInfo
1022 tyvarFVInfo tvs = foldVarSet add emptyFVInfo tvs
1024 add tv fvs = extendVarEnv fvs tv (tv, LambdaBound, noBinderInfo)
1025 -- Type variables must be lambda-bound
1027 unionFVInfo :: FreeVarsInfo -> FreeVarsInfo -> FreeVarsInfo
1028 unionFVInfo fv1 fv2 = plusVarEnv_C plusFVInfo fv1 fv2
1030 unionFVInfos :: [FreeVarsInfo] -> FreeVarsInfo
1031 unionFVInfos fvs = foldr unionFVInfo emptyFVInfo fvs
1033 minusFVBinders :: [Id] -> FreeVarsInfo -> FreeVarsInfo
1034 minusFVBinders vs fv = foldr minusFVBinder fv vs
1036 minusFVBinder :: Id -> FreeVarsInfo -> FreeVarsInfo
1037 minusFVBinder v fv | isId v && opt_RuntimeTypes
1038 = (fv `delVarEnv` v) `unionFVInfo`
1039 tyvarFVInfo (tyVarsOfType (idType v))
1040 | otherwise = fv `delVarEnv` v
1041 -- When removing a binder, remember to add its type variables
1042 -- c.f. CoreFVs.delBinderFV
1044 elementOfFVInfo :: Id -> FreeVarsInfo -> Bool
1045 elementOfFVInfo id fvs = maybeToBool (lookupVarEnv fvs id)
1047 lookupFVInfo :: FreeVarsInfo -> Id -> StgBinderInfo
1048 -- Find how the given Id is used.
1049 -- Externally visible things may be used any old how
1051 | isExternalName (idName id) = noBinderInfo
1052 | otherwise = case lookupVarEnv fvs id of
1053 Nothing -> noBinderInfo
1054 Just (_,_,info) -> info
1056 allFreeIds :: FreeVarsInfo -> [(Id,HowBound)] -- Both top level and non-top-level Ids
1057 allFreeIds fvs = [(id,how_bound) | (id,how_bound,_) <- varEnvElts fvs, isId id]
1059 -- Non-top-level things only, both type variables and ids
1060 -- (type variables only if opt_RuntimeTypes)
1061 getFVs :: FreeVarsInfo -> [Var]
1062 getFVs fvs = [id | (id, how_bound, _) <- varEnvElts fvs,
1063 not (topLevelBound how_bound) ]
1065 getFVSet :: FreeVarsInfo -> VarSet
1066 getFVSet fvs = mkVarSet (getFVs fvs)
1068 plusFVInfo (id1,hb1,info1) (id2,hb2,info2)
1069 = ASSERT (id1 == id2 && hb1 `check_eq_how_bound` hb2)
1070 (id1, hb1, combineStgBinderInfo info1 info2)
1073 -- The HowBound info for a variable in the FVInfo should be consistent
1074 check_eq_how_bound ImportBound ImportBound = True
1075 check_eq_how_bound LambdaBound LambdaBound = True
1076 check_eq_how_bound (LetBound li1 ar1) (LetBound li2 ar2) = ar1 == ar2 && check_eq_li li1 li2
1077 check_eq_how_bound hb1 hb2 = False
1079 check_eq_li (NestedLet _) (NestedLet _) = True
1080 check_eq_li TopLet TopLet = True
1081 check_eq_li li1 li2 = False
1087 filterStgBinders :: [Var] -> [Var]
1088 filterStgBinders bndrs
1089 | opt_RuntimeTypes = bndrs
1090 | otherwise = filter isId bndrs
1095 -- Ignore all notes except SCC
1096 myCollectBinders expr
1099 go bs (Lam b e) = go (b:bs) e
1100 go bs e@(Note (SCC _) _) = (reverse bs, e)
1101 go bs e@(Note (TickBox {}) _) = (reverse bs, e)
1102 go bs e@(Note (BinaryTickBox {}) _) = (reverse bs, e)
1103 go bs (Cast e co) = go bs e
1104 go bs (Note _ e) = go bs e
1105 go bs e = (reverse bs, e)
1107 myCollectArgs :: CoreExpr -> (Id, [CoreArg])
1108 -- We assume that we only have variables
1109 -- in the function position by now
1113 go (Var v) as = (v, as)
1114 go (App f a) as = go f (a:as)
1115 go (Note (SCC _) e) as = pprPanic "CoreToStg.myCollectArgs" (ppr expr)
1116 go (Note (TickBox {}) e) as = pprPanic "CoreToStg.myCollectArgs" (ppr expr)
1117 go (Note (BinaryTickBox {}) e) as = pprPanic "CoreToStg.myCollectArgs" (ppr expr)
1118 go (Cast e co) as = go e as
1119 go (Note n e) as = go e as
1120 go _ as = pprPanic "CoreToStg.myCollectArgs" (ppr expr)
1124 stgArity :: Id -> HowBound -> Arity
1125 stgArity f (LetBound _ arity) = arity
1126 stgArity f ImportBound = idArity f
1127 stgArity f LambdaBound = 0