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 )
24 import MkId ( unsafeCoerceId )
28 import CostCentre ( noCCS )
31 import Maybes ( maybeToBool )
32 import Name ( getOccName, isExternalName, nameOccName )
33 import OccName ( occNameString, occNameFS )
34 import BasicTypes ( Arity )
35 import StaticFlags ( opt_RuntimeTypes )
36 import PackageConfig ( PackageId )
42 %************************************************************************
44 \subsection[live-vs-free-doc]{Documentation}
46 %************************************************************************
48 (There is other relevant documentation in codeGen/CgLetNoEscape.)
50 The actual Stg datatype is decorated with {\em live variable}
51 information, as well as {\em free variable} information. The two are
52 {\em not} the same. Liveness is an operational property rather than a
53 semantic one. A variable is live at a particular execution point if
54 it can be referred to {\em directly} again. In particular, a dead
55 variable's stack slot (if it has one):
58 should be stubbed to avoid space leaks, and
60 may be reused for something else.
63 There ought to be a better way to say this. Here are some examples:
70 Just after the `in', v is live, but q is dead. If the whole of that
71 let expression was enclosed in a case expression, thus:
73 case (let v = [q] \[x] -> e in ...v...) of
76 (ie @alts@ mention @q@), then @q@ is live even after the `in'; because
77 we'll return later to the @alts@ and need it.
79 Let-no-escapes make this a bit more interesting:
81 let-no-escape v = [q] \ [x] -> e
85 Here, @q@ is still live at the `in', because @v@ is represented not by
86 a closure but by the current stack state. In other words, if @v@ is
87 live then so is @q@. Furthermore, if @e@ mentions an enclosing
88 let-no-escaped variable, then {\em its} free variables are also live
91 %************************************************************************
93 \subsection[caf-info]{Collecting live CAF info}
95 %************************************************************************
97 In this pass we also collect information on which CAFs are live for
98 constructing SRTs (see SRT.lhs).
100 A top-level Id has CafInfo, which is
102 - MayHaveCafRefs, if it may refer indirectly to
104 - NoCafRefs if it definitely doesn't
106 The CafInfo has already been calculated during the CoreTidy pass.
108 During CoreToStg, we then pin onto each binding and case expression, a
109 list of Ids which represents the "live" CAFs at that point. The meaning
110 of "live" here is the same as for live variables, see above (which is
111 why it's convenient to collect CAF information here rather than elsewhere).
113 The later SRT pass takes these lists of Ids and uses them to construct
114 the actual nested SRTs, and replaces the lists of Ids with (offset,length)
118 Interaction of let-no-escape with SRTs [Sept 01]
119 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
122 let-no-escape x = ...caf1...caf2...
126 where caf1,caf2 are CAFs. Since x doesn't have a closure, we
127 build SRTs just as if x's defn was inlined at each call site, and
128 that means that x's CAF refs get duplicated in the overall SRT.
130 This is unlike ordinary lets, in which the CAF refs are not duplicated.
132 We could fix this loss of (static) sharing by making a sort of pseudo-closure
133 for x, solely to put in the SRTs lower down.
136 %************************************************************************
138 \subsection[binds-StgVarInfo]{Setting variable info: top-level, binds, RHSs}
140 %************************************************************************
143 coreToStg :: PackageId -> [CoreBind] -> IO [StgBinding]
144 coreToStg this_pkg pgm
146 where (_, _, pgm') = coreTopBindsToStg this_pkg emptyVarEnv pgm
148 coreExprToStg :: CoreExpr -> StgExpr
150 = new_expr where (new_expr,_,_) = initLne emptyVarEnv (coreToStgExpr expr)
155 -> IdEnv HowBound -- environment for the bindings
157 -> (IdEnv HowBound, FreeVarsInfo, [StgBinding])
159 coreTopBindsToStg this_pkg env [] = (env, emptyFVInfo, [])
160 coreTopBindsToStg this_pkg env (b:bs)
161 = (env2, fvs2, b':bs')
163 -- env accumulates down the list of binds, fvs accumulates upwards
164 (env1, fvs2, b' ) = coreTopBindToStg this_pkg env fvs1 b
165 (env2, fvs1, bs') = coreTopBindsToStg this_pkg env1 bs
171 -> FreeVarsInfo -- Info about the body
173 -> (IdEnv HowBound, FreeVarsInfo, StgBinding)
175 coreTopBindToStg this_pkg env body_fvs (NonRec id rhs)
177 env' = extendVarEnv env id how_bound
178 how_bound = LetBound TopLet $! manifestArity rhs
182 coreToTopStgRhs this_pkg body_fvs (id,rhs) `thenLne` \ (stg_rhs, fvs') ->
183 returnLne (stg_rhs, fvs')
186 bind = StgNonRec id stg_rhs
188 ASSERT2(manifestArity rhs == stgRhsArity stg_rhs, ppr id)
189 ASSERT2(consistentCafInfo id bind, ppr id)
190 -- WARN(not (consistent caf_info bind), ppr id <+> ppr cafs <+> ppCafInfo caf_info)
191 (env', fvs' `unionFVInfo` body_fvs, bind)
193 coreTopBindToStg this_pkg env body_fvs (Rec pairs)
195 (binders, rhss) = unzip pairs
197 extra_env' = [ (b, LetBound TopLet $! manifestArity rhs)
198 | (b, rhs) <- pairs ]
199 env' = extendVarEnvList env extra_env'
203 mapAndUnzipLne (coreToTopStgRhs this_pkg body_fvs) pairs
204 `thenLne` \ (stg_rhss, fvss') ->
205 let fvs' = unionFVInfos fvss' in
206 returnLne (stg_rhss, fvs')
209 bind = StgRec (zip binders stg_rhss)
211 ASSERT2(and [manifestArity rhs == stgRhsArity stg_rhs | (rhs,stg_rhs) <- rhss `zip` stg_rhss], ppr binders)
212 ASSERT2(consistentCafInfo (head binders) bind, ppr binders)
213 (env', fvs' `unionFVInfo` body_fvs, bind)
216 -- Assertion helper: this checks that the CafInfo on the Id matches
217 -- what CoreToStg has figured out about the binding's SRT. The
218 -- CafInfo will be exact in all cases except when CorePrep has
219 -- floated out a binding, in which case it will be approximate.
220 consistentCafInfo id bind
221 | occNameFS (nameOccName (idName id)) == FSLIT("sat")
224 = WARN (not exact, ppr id) safe
226 safe = id_marked_caffy || not binding_is_caffy
227 exact = id_marked_caffy == binding_is_caffy
228 id_marked_caffy = mayHaveCafRefs (idCafInfo id)
229 binding_is_caffy = stgBindHasCafRefs bind
236 -> FreeVarsInfo -- Free var info for the scope of the binding
238 -> LneM (StgRhs, FreeVarsInfo)
240 coreToTopStgRhs this_pkg scope_fv_info (bndr, rhs)
241 = coreToStgExpr rhs `thenLne` \ (new_rhs, rhs_fvs, _) ->
242 freeVarsToLiveVars rhs_fvs `thenLne` \ lv_info ->
243 returnLne (mkTopStgRhs is_static rhs_fvs (mkSRT lv_info) bndr_info new_rhs, rhs_fvs)
245 bndr_info = lookupFVInfo scope_fv_info bndr
246 is_static = rhsIsStatic this_pkg rhs
248 mkTopStgRhs :: Bool -> FreeVarsInfo -> SRT -> StgBinderInfo -> StgExpr
251 mkTopStgRhs is_static rhs_fvs srt binder_info (StgLam _ bndrs body)
252 = ASSERT( is_static )
253 StgRhsClosure noCCS binder_info
259 mkTopStgRhs is_static rhs_fvs srt binder_info (StgConApp con args)
260 | is_static -- StgConApps can be updatable (see isCrossDllConApp)
261 = StgRhsCon noCCS con args
263 mkTopStgRhs is_static rhs_fvs srt binder_info rhs
264 = ASSERT2( not is_static, ppr rhs )
265 StgRhsClosure noCCS binder_info
273 -- ---------------------------------------------------------------------------
275 -- ---------------------------------------------------------------------------
280 -> LneM (StgExpr, -- Decorated STG expr
281 FreeVarsInfo, -- Its free vars (NB free, not live)
282 EscVarsSet) -- Its escapees, a subset of its free vars;
283 -- also a subset of the domain of the envt
284 -- because we are only interested in the escapees
285 -- for vars which might be turned into
286 -- let-no-escaped ones.
289 The second and third components can be derived in a simple bottom up pass, not
290 dependent on any decisions about which variables will be let-no-escaped or
291 not. The first component, that is, the decorated expression, may then depend
292 on these components, but it in turn is not scrutinised as the basis for any
293 decisions. Hence no black holes.
296 coreToStgExpr (Lit l) = returnLne (StgLit l, emptyFVInfo, emptyVarSet)
297 coreToStgExpr (Var v) = coreToStgApp Nothing v []
299 coreToStgExpr expr@(App _ _)
300 = coreToStgApp Nothing f args
302 (f, args) = myCollectArgs expr
304 coreToStgExpr expr@(Lam _ _)
306 (args, body) = myCollectBinders expr
307 args' = filterStgBinders args
309 extendVarEnvLne [ (a, LambdaBound) | a <- args' ] $
310 coreToStgExpr body `thenLne` \ (body, body_fvs, body_escs) ->
312 fvs = args' `minusFVBinders` body_fvs
313 escs = body_escs `delVarSetList` args'
314 result_expr | null args' = body
315 | otherwise = StgLam (exprType expr) args' body
317 returnLne (result_expr, fvs, escs)
319 coreToStgExpr (Note (SCC cc) expr)
320 = coreToStgExpr expr `thenLne` ( \ (expr2, fvs, escs) ->
321 returnLne (StgSCC cc expr2, fvs, escs) )
324 -- For ILX, convert (__coerce__ to_ty from_ty e)
325 -- into (coerce to_ty from_ty e)
326 -- where coerce is real function
327 coreToStgExpr (Note (Coerce to_ty from_ty) expr)
328 = coreToStgExpr (mkApps (Var unsafeCoerceId)
329 [Type from_ty, Type to_ty, expr])
332 coreToStgExpr (Note other_note expr)
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 returnLne (stg_arg : stg_args, fvs)
554 -- ---------------------------------------------------------------------------
555 -- The magic for lets:
556 -- ---------------------------------------------------------------------------
559 :: Bool -- True <=> yes, we are let-no-escaping this let
560 -> CoreBind -- bindings
562 -> LneM (StgExpr, -- new let
563 FreeVarsInfo, -- variables free in the whole let
564 EscVarsSet, -- variables that escape from the whole let
565 Bool) -- True <=> none of the binders in the bindings
566 -- is among the escaping vars
568 coreToStgLet let_no_escape bind body
569 = fixLne (\ ~(_, _, _, _, _, rec_body_fvs, _, _) ->
571 -- Do the bindings, setting live_in_cont to empty if
572 -- we ain't in a let-no-escape world
573 getVarsLiveInCont `thenLne` \ live_in_cont ->
574 setVarsLiveInCont (if let_no_escape
577 (vars_bind rec_body_fvs bind)
578 `thenLne` \ ( bind2, bind_fvs, bind_escs, bind_lv_info, env_ext) ->
581 extendVarEnvLne env_ext (
582 coreToStgExpr body `thenLne` \(body2, body_fvs, body_escs) ->
583 freeVarsToLiveVars body_fvs `thenLne` \ body_lv_info ->
585 returnLne (bind2, bind_fvs, bind_escs, getLiveVars bind_lv_info,
586 body2, body_fvs, body_escs, getLiveVars body_lv_info)
589 ) `thenLne` (\ (bind2, bind_fvs, bind_escs, bind_lvs,
590 body2, body_fvs, body_escs, body_lvs) ->
593 -- Compute the new let-expression
595 new_let | let_no_escape = StgLetNoEscape live_in_whole_let bind_lvs bind2 body2
596 | otherwise = StgLet bind2 body2
599 = binders `minusFVBinders` (bind_fvs `unionFVInfo` body_fvs)
602 = bind_lvs `unionVarSet` (body_lvs `delVarSetList` binders)
604 real_bind_escs = if let_no_escape then
608 -- Everything escapes which is free in the bindings
610 let_escs = (real_bind_escs `unionVarSet` body_escs) `delVarSetList` binders
612 all_escs = bind_escs `unionVarSet` body_escs -- Still includes binders of
615 no_binder_escapes = isEmptyVarSet (set_of_binders `intersectVarSet` all_escs)
618 -- Debugging code as requested by Andrew Kennedy
619 checked_no_binder_escapes
620 | not no_binder_escapes && any is_join_var binders
621 = pprTrace "Interesting! A join var that isn't let-no-escaped" (ppr binders)
623 | otherwise = no_binder_escapes
625 checked_no_binder_escapes = no_binder_escapes
628 -- Mustn't depend on the passed-in let_no_escape flag, since
629 -- no_binder_escapes is used by the caller to derive the flag!
635 checked_no_binder_escapes
638 set_of_binders = mkVarSet binders
639 binders = bindersOf bind
641 mk_binding bind_lv_info binder rhs
642 = (binder, LetBound (NestedLet live_vars) (manifestArity rhs))
644 live_vars | let_no_escape = addLiveVar bind_lv_info binder
645 | otherwise = unitLiveVar binder
646 -- c.f. the invariant on NestedLet
648 vars_bind :: FreeVarsInfo -- Free var info for body of binding
652 EscVarsSet, -- free vars; escapee vars
653 LiveInfo, -- Vars and CAFs live in binding
654 [(Id, HowBound)]) -- extension to environment
657 vars_bind body_fvs (NonRec binder rhs)
658 = coreToStgRhs body_fvs [] (binder,rhs)
659 `thenLne` \ (rhs2, bind_fvs, bind_lv_info, escs) ->
661 env_ext_item = mk_binding bind_lv_info binder rhs
663 returnLne (StgNonRec binder rhs2,
664 bind_fvs, escs, bind_lv_info, [env_ext_item])
667 vars_bind body_fvs (Rec pairs)
668 = fixLne (\ ~(_, rec_rhs_fvs, _, bind_lv_info, _) ->
670 rec_scope_fvs = unionFVInfo body_fvs rec_rhs_fvs
671 binders = map fst pairs
672 env_ext = [ mk_binding bind_lv_info b rhs
675 extendVarEnvLne env_ext (
676 mapAndUnzip4Lne (coreToStgRhs rec_scope_fvs binders) pairs
677 `thenLne` \ (rhss2, fvss, lv_infos, escss) ->
679 bind_fvs = unionFVInfos fvss
680 bind_lv_info = foldr unionLiveInfo emptyLiveInfo lv_infos
681 escs = unionVarSets escss
683 returnLne (StgRec (binders `zip` rhss2),
684 bind_fvs, escs, bind_lv_info, env_ext)
688 is_join_var :: Id -> Bool
689 -- A hack (used only for compiler debuggging) to tell if
690 -- a variable started life as a join point ($j)
691 is_join_var j = occNameString (getOccName j) == "$j"
695 coreToStgRhs :: FreeVarsInfo -- Free var info for the scope of the binding
698 -> LneM (StgRhs, FreeVarsInfo, LiveInfo, EscVarsSet)
700 coreToStgRhs scope_fv_info binders (bndr, rhs)
701 = coreToStgExpr rhs `thenLne` \ (new_rhs, rhs_fvs, rhs_escs) ->
702 getEnvLne `thenLne` \ env ->
703 freeVarsToLiveVars (binders `minusFVBinders` rhs_fvs) `thenLne` \ lv_info ->
704 returnLne (mkStgRhs rhs_fvs (mkSRT lv_info) bndr_info new_rhs,
705 rhs_fvs, lv_info, rhs_escs)
707 bndr_info = lookupFVInfo scope_fv_info bndr
709 mkStgRhs :: FreeVarsInfo -> SRT -> StgBinderInfo -> StgExpr -> StgRhs
711 mkStgRhs rhs_fvs srt binder_info (StgConApp con args)
712 = StgRhsCon noCCS con args
714 mkStgRhs rhs_fvs srt binder_info (StgLam _ bndrs body)
715 = StgRhsClosure noCCS binder_info
720 mkStgRhs rhs_fvs srt binder_info rhs
721 = StgRhsClosure noCCS binder_info
727 SDM: disabled. Eval/Apply can't handle functions with arity zero very
728 well; and making these into simple non-updatable thunks breaks other
729 assumptions (namely that they will be entered only once).
731 upd_flag | isPAP env rhs = ReEntrant
732 | otherwise = Updatable
736 upd = if isOnceDem dem
737 then (if isNotTop toplev
738 then SingleEntry -- HA! Paydirt for "dem"
741 trace "WARNING: SE CAFs unsupported, forcing UPD instead" $
745 -- For now we forbid SingleEntry CAFs; they tickle the
746 -- ASSERT in rts/Storage.c line 215 at newCAF() re mut_link,
747 -- and I don't understand why. There's only one SE_CAF (well,
748 -- only one that tickled a great gaping bug in an earlier attempt
749 -- at ClosureInfo.getEntryConvention) in the whole of nofib,
750 -- specifically Main.lvl6 in spectral/cryptarithm2.
751 -- So no great loss. KSW 2000-07.
755 Detect thunks which will reduce immediately to PAPs, and make them
756 non-updatable. This has several advantages:
758 - the non-updatable thunk behaves exactly like the PAP,
760 - the thunk is more efficient to enter, because it is
761 specialised to the task.
763 - we save one update frame, one stg_update_PAP, one update
764 and lots of PAP_enters.
766 - in the case where the thunk is top-level, we save building
767 a black hole and futhermore the thunk isn't considered to
768 be a CAF any more, so it doesn't appear in any SRTs.
770 We do it here, because the arity information is accurate, and we need
771 to do it before the SRT pass to save the SRT entries associated with
774 isPAP env (StgApp f args) = listLengthCmp args arity == LT -- idArity f > length args
776 arity = stgArity f (lookupBinding env f)
780 %************************************************************************
782 \subsection[LNE-monad]{A little monad for this let-no-escaping pass}
784 %************************************************************************
786 There's a lot of stuff to pass around, so we use this @LneM@ monad to
787 help. All the stuff here is only passed *down*.
790 type LneM a = IdEnv HowBound
791 -> LiveInfo -- Vars and CAFs live in continuation
794 type LiveInfo = (StgLiveVars, -- Dynamic live variables;
795 -- i.e. ones with a nested (non-top-level) binding
796 CafSet) -- Static live variables;
797 -- i.e. top-level variables that are CAFs or refer to them
799 type EscVarsSet = IdSet
803 = ImportBound -- Used only as a response to lookupBinding; never
804 -- exists in the range of the (IdEnv HowBound)
806 | LetBound -- A let(rec) in this module
807 LetInfo -- Whether top level or nested
808 Arity -- Its arity (local Ids don't have arity info at this point)
810 | LambdaBound -- Used for both lambda and case
813 = TopLet -- top level things
814 | NestedLet LiveInfo -- For nested things, what is live if this
815 -- thing is live? Invariant: the binder
816 -- itself is always a member of
817 -- the dynamic set of its own LiveInfo
819 isLetBound (LetBound _ _) = True
820 isLetBound other = False
822 topLevelBound ImportBound = True
823 topLevelBound (LetBound TopLet _) = True
824 topLevelBound other = False
827 For a let(rec)-bound variable, x, we record LiveInfo, the set of
828 variables that are live if x is live. This LiveInfo comprises
829 (a) dynamic live variables (ones with a non-top-level binding)
830 (b) static live variabes (CAFs or things that refer to CAFs)
832 For "normal" variables (a) is just x alone. If x is a let-no-escaped
833 variable then x is represented by a code pointer and a stack pointer
834 (well, one for each stack). So all of the variables needed in the
835 execution of x are live if x is, and are therefore recorded in the
836 LetBound constructor; x itself *is* included.
838 The set of dynamic live variables is guaranteed ot have no further let-no-escaped
842 emptyLiveInfo :: LiveInfo
843 emptyLiveInfo = (emptyVarSet,emptyVarSet)
845 unitLiveVar :: Id -> LiveInfo
846 unitLiveVar lv = (unitVarSet lv, emptyVarSet)
848 unitLiveCaf :: Id -> LiveInfo
849 unitLiveCaf caf = (emptyVarSet, unitVarSet caf)
851 addLiveVar :: LiveInfo -> Id -> LiveInfo
852 addLiveVar (lvs, cafs) id = (lvs `extendVarSet` id, cafs)
854 unionLiveInfo :: LiveInfo -> LiveInfo -> LiveInfo
855 unionLiveInfo (lv1,caf1) (lv2,caf2) = (lv1 `unionVarSet` lv2, caf1 `unionVarSet` caf2)
857 mkSRT :: LiveInfo -> SRT
858 mkSRT (_, cafs) = SRTEntries cafs
860 getLiveVars :: LiveInfo -> StgLiveVars
861 getLiveVars (lvs, _) = lvs
865 The std monad functions:
867 initLne :: IdEnv HowBound -> LneM a -> a
868 initLne env m = m env emptyLiveInfo
872 {-# INLINE thenLne #-}
873 {-# INLINE returnLne #-}
875 returnLne :: a -> LneM a
876 returnLne e env lvs_cont = e
878 thenLne :: LneM a -> (a -> LneM b) -> LneM b
879 thenLne m k env lvs_cont
880 = k (m env lvs_cont) env lvs_cont
882 mapAndUnzipLne :: (a -> LneM (b,c)) -> [a] -> LneM ([b],[c])
883 mapAndUnzipLne f [] = returnLne ([],[])
884 mapAndUnzipLne f (x:xs)
885 = f x `thenLne` \ (r1, r2) ->
886 mapAndUnzipLne f xs `thenLne` \ (rs1, rs2) ->
887 returnLne (r1:rs1, r2:rs2)
889 mapAndUnzip3Lne :: (a -> LneM (b,c,d)) -> [a] -> LneM ([b],[c],[d])
890 mapAndUnzip3Lne f [] = returnLne ([],[],[])
891 mapAndUnzip3Lne f (x:xs)
892 = f x `thenLne` \ (r1, r2, r3) ->
893 mapAndUnzip3Lne f xs `thenLne` \ (rs1, rs2, rs3) ->
894 returnLne (r1:rs1, r2:rs2, r3:rs3)
896 mapAndUnzip4Lne :: (a -> LneM (b,c,d,e)) -> [a] -> LneM ([b],[c],[d],[e])
897 mapAndUnzip4Lne f [] = returnLne ([],[],[],[])
898 mapAndUnzip4Lne f (x:xs)
899 = f x `thenLne` \ (r1, r2, r3, r4) ->
900 mapAndUnzip4Lne f xs `thenLne` \ (rs1, rs2, rs3, rs4) ->
901 returnLne (r1:rs1, r2:rs2, r3:rs3, r4:rs4)
903 fixLne :: (a -> LneM a) -> LneM a
904 fixLne expr env lvs_cont
907 result = expr result env lvs_cont
910 Functions specific to this monad:
913 getVarsLiveInCont :: LneM LiveInfo
914 getVarsLiveInCont env lvs_cont = lvs_cont
916 setVarsLiveInCont :: LiveInfo -> LneM a -> LneM a
917 setVarsLiveInCont new_lvs_cont expr env lvs_cont
918 = expr env new_lvs_cont
920 extendVarEnvLne :: [(Id, HowBound)] -> LneM a -> LneM a
921 extendVarEnvLne ids_w_howbound expr env lvs_cont
922 = expr (extendVarEnvList env ids_w_howbound) lvs_cont
924 lookupVarLne :: Id -> LneM HowBound
925 lookupVarLne v env lvs_cont = returnLne (lookupBinding env v) env lvs_cont
927 getEnvLne :: LneM (IdEnv HowBound)
928 getEnvLne env lvs_cont = returnLne env env lvs_cont
930 lookupBinding :: IdEnv HowBound -> Id -> HowBound
931 lookupBinding env v = case lookupVarEnv env v of
933 Nothing -> ASSERT2( isGlobalId v, ppr v ) ImportBound
936 -- The result of lookupLiveVarsForSet, a set of live variables, is
937 -- only ever tacked onto a decorated expression. It is never used as
938 -- the basis of a control decision, which might give a black hole.
940 freeVarsToLiveVars :: FreeVarsInfo -> LneM LiveInfo
941 freeVarsToLiveVars fvs env live_in_cont
942 = returnLne live_info env live_in_cont
944 live_info = foldr unionLiveInfo live_in_cont lvs_from_fvs
945 lvs_from_fvs = map do_one (allFreeIds fvs)
947 do_one (v, how_bound)
949 ImportBound -> unitLiveCaf v -- Only CAF imports are
952 | mayHaveCafRefs (idCafInfo v) -> unitLiveCaf v
953 | otherwise -> emptyLiveInfo
955 LetBound (NestedLet lvs) _ -> lvs -- lvs already contains v
956 -- (see the invariant on NestedLet)
958 _lambda_or_case_binding -> unitLiveVar v -- Bound by lambda or case
961 %************************************************************************
963 \subsection[Free-var info]{Free variable information}
965 %************************************************************************
968 type FreeVarsInfo = VarEnv (Var, HowBound, StgBinderInfo)
969 -- The Var is so we can gather up the free variables
972 -- The HowBound info just saves repeated lookups;
973 -- we look up just once when we encounter the occurrence.
974 -- INVARIANT: Any ImportBound Ids are HaveCafRef Ids
975 -- Imported Ids without CAF refs are simply
976 -- not put in the FreeVarsInfo for an expression.
977 -- See singletonFVInfo and freeVarsToLiveVars
979 -- StgBinderInfo records how it occurs; notably, we
980 -- are interested in whether it only occurs in saturated
981 -- applications, because then we don't need to build a
983 -- If f is mapped to noBinderInfo, that means
984 -- that f *is* mentioned (else it wouldn't be in the
985 -- IdEnv at all), but perhaps in an unsaturated applications.
987 -- All case/lambda-bound things are also mapped to
988 -- noBinderInfo, since we aren't interested in their
991 -- For ILX we track free var info for type variables too;
992 -- hence VarEnv not IdEnv
996 emptyFVInfo :: FreeVarsInfo
997 emptyFVInfo = emptyVarEnv
999 singletonFVInfo :: Id -> HowBound -> StgBinderInfo -> FreeVarsInfo
1000 -- Don't record non-CAF imports at all, to keep free-var sets small
1001 singletonFVInfo id ImportBound info
1002 | mayHaveCafRefs (idCafInfo id) = unitVarEnv id (id, ImportBound, info)
1003 | otherwise = emptyVarEnv
1004 singletonFVInfo id how_bound info = unitVarEnv id (id, how_bound, info)
1006 tyvarFVInfo :: TyVarSet -> FreeVarsInfo
1007 tyvarFVInfo tvs = foldVarSet add emptyFVInfo tvs
1009 add tv fvs = extendVarEnv fvs tv (tv, LambdaBound, noBinderInfo)
1010 -- Type variables must be lambda-bound
1012 unionFVInfo :: FreeVarsInfo -> FreeVarsInfo -> FreeVarsInfo
1013 unionFVInfo fv1 fv2 = plusVarEnv_C plusFVInfo fv1 fv2
1015 unionFVInfos :: [FreeVarsInfo] -> FreeVarsInfo
1016 unionFVInfos fvs = foldr unionFVInfo emptyFVInfo fvs
1018 minusFVBinders :: [Id] -> FreeVarsInfo -> FreeVarsInfo
1019 minusFVBinders vs fv = foldr minusFVBinder fv vs
1021 minusFVBinder :: Id -> FreeVarsInfo -> FreeVarsInfo
1022 minusFVBinder v fv | isId v && opt_RuntimeTypes
1023 = (fv `delVarEnv` v) `unionFVInfo`
1024 tyvarFVInfo (tyVarsOfType (idType v))
1025 | otherwise = fv `delVarEnv` v
1026 -- When removing a binder, remember to add its type variables
1027 -- c.f. CoreFVs.delBinderFV
1029 elementOfFVInfo :: Id -> FreeVarsInfo -> Bool
1030 elementOfFVInfo id fvs = maybeToBool (lookupVarEnv fvs id)
1032 lookupFVInfo :: FreeVarsInfo -> Id -> StgBinderInfo
1033 -- Find how the given Id is used.
1034 -- Externally visible things may be used any old how
1036 | isExternalName (idName id) = noBinderInfo
1037 | otherwise = case lookupVarEnv fvs id of
1038 Nothing -> noBinderInfo
1039 Just (_,_,info) -> info
1041 allFreeIds :: FreeVarsInfo -> [(Id,HowBound)] -- Both top level and non-top-level Ids
1042 allFreeIds fvs = [(id,how_bound) | (id,how_bound,_) <- varEnvElts fvs, isId id]
1044 -- Non-top-level things only, both type variables and ids
1045 -- (type variables only if opt_RuntimeTypes)
1046 getFVs :: FreeVarsInfo -> [Var]
1047 getFVs fvs = [id | (id, how_bound, _) <- varEnvElts fvs,
1048 not (topLevelBound how_bound) ]
1050 getFVSet :: FreeVarsInfo -> VarSet
1051 getFVSet fvs = mkVarSet (getFVs fvs)
1053 plusFVInfo (id1,hb1,info1) (id2,hb2,info2)
1054 = ASSERT (id1 == id2 && hb1 `check_eq_how_bound` hb2)
1055 (id1, hb1, combineStgBinderInfo info1 info2)
1058 -- The HowBound info for a variable in the FVInfo should be consistent
1059 check_eq_how_bound ImportBound ImportBound = True
1060 check_eq_how_bound LambdaBound LambdaBound = True
1061 check_eq_how_bound (LetBound li1 ar1) (LetBound li2 ar2) = ar1 == ar2 && check_eq_li li1 li2
1062 check_eq_how_bound hb1 hb2 = False
1064 check_eq_li (NestedLet _) (NestedLet _) = True
1065 check_eq_li TopLet TopLet = True
1066 check_eq_li li1 li2 = False
1072 filterStgBinders :: [Var] -> [Var]
1073 filterStgBinders bndrs
1074 | opt_RuntimeTypes = bndrs
1075 | otherwise = filter isId bndrs
1080 -- Ignore all notes except SCC
1081 myCollectBinders expr
1084 go bs (Lam b e) = go (b:bs) e
1085 go bs e@(Note (SCC _) _) = (reverse bs, e)
1086 go bs (Note _ e) = go bs e
1087 go bs e = (reverse bs, e)
1089 myCollectArgs :: CoreExpr -> (Id, [CoreArg])
1090 -- We assume that we only have variables
1091 -- in the function position by now
1095 go (Var v) as = (v, as)
1096 go (App f a) as = go f (a:as)
1097 go (Note (SCC _) e) as = pprPanic "CoreToStg.myCollectArgs" (ppr expr)
1098 go (Note n e) as = go e as
1099 go _ as = pprPanic "CoreToStg.myCollectArgs" (ppr expr)
1103 stgArity :: Id -> HowBound -> Arity
1104 stgArity f (LetBound _ arity) = arity
1105 stgArity f ImportBound = idArity f
1106 stgArity f LambdaBound = 0