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"
19 import TyCon ( isAlgTyCon )
22 import Var ( Var, globalIdDetails, varType )
24 import MkId ( unsafeCoerceId )
28 import CostCentre ( noCCS )
31 import Maybes ( maybeToBool )
32 import Name ( getOccName, isExternalName, nameOccName )
33 import OccName ( occNameUserString, occNameFS )
34 import BasicTypes ( Arity )
35 import CmdLineOpts ( DynFlags, opt_RuntimeTypes )
41 %************************************************************************
43 \subsection[live-vs-free-doc]{Documentation}
45 %************************************************************************
47 (There is other relevant documentation in codeGen/CgLetNoEscape.)
49 The actual Stg datatype is decorated with {\em live variable}
50 information, as well as {\em free variable} information. The two are
51 {\em not} the same. Liveness is an operational property rather than a
52 semantic one. A variable is live at a particular execution point if
53 it can be referred to {\em directly} again. In particular, a dead
54 variable's stack slot (if it has one):
57 should be stubbed to avoid space leaks, and
59 may be reused for something else.
62 There ought to be a better way to say this. Here are some examples:
69 Just after the `in', v is live, but q is dead. If the whole of that
70 let expression was enclosed in a case expression, thus:
72 case (let v = [q] \[x] -> e in ...v...) of
75 (ie @alts@ mention @q@), then @q@ is live even after the `in'; because
76 we'll return later to the @alts@ and need it.
78 Let-no-escapes make this a bit more interesting:
80 let-no-escape v = [q] \ [x] -> e
84 Here, @q@ is still live at the `in', because @v@ is represented not by
85 a closure but by the current stack state. In other words, if @v@ is
86 live then so is @q@. Furthermore, if @e@ mentions an enclosing
87 let-no-escaped variable, then {\em its} free variables are also live
90 %************************************************************************
92 \subsection[caf-info]{Collecting live CAF info}
94 %************************************************************************
96 In this pass we also collect information on which CAFs are live for
97 constructing SRTs (see SRT.lhs).
99 A top-level Id has CafInfo, which is
101 - MayHaveCafRefs, if it may refer indirectly to
103 - NoCafRefs if it definitely doesn't
105 The CafInfo has already been calculated during the CoreTidy pass.
107 During CoreToStg, we then pin onto each binding and case expression, a
108 list of Ids which represents the "live" CAFs at that point. The meaning
109 of "live" here is the same as for live variables, see above (which is
110 why it's convenient to collect CAF information here rather than elsewhere).
112 The later SRT pass takes these lists of Ids and uses them to construct
113 the actual nested SRTs, and replaces the lists of Ids with (offset,length)
117 Interaction of let-no-escape with SRTs [Sept 01]
118 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
121 let-no-escape x = ...caf1...caf2...
125 where caf1,caf2 are CAFs. Since x doesn't have a closure, we
126 build SRTs just as if x's defn was inlined at each call site, and
127 that means that x's CAF refs get duplicated in the overall SRT.
129 This is unlike ordinary lets, in which the CAF refs are not duplicated.
131 We could fix this loss of (static) sharing by making a sort of pseudo-closure
132 for x, solely to put in the SRTs lower down.
135 %************************************************************************
137 \subsection[binds-StgVarInfo]{Setting variable info: top-level, binds, RHSs}
139 %************************************************************************
142 coreToStg :: DynFlags -> [CoreBind] -> IO [StgBinding]
145 where (_, _, pgm') = coreTopBindsToStg emptyVarEnv pgm
147 coreExprToStg :: CoreExpr -> StgExpr
149 = new_expr where (new_expr,_,_) = initLne emptyVarEnv (coreToStgExpr expr)
153 :: IdEnv HowBound -- environment for the bindings
155 -> (IdEnv HowBound, FreeVarsInfo, [StgBinding])
157 coreTopBindsToStg env [] = (env, emptyFVInfo, [])
158 coreTopBindsToStg env (b:bs)
159 = (env2, fvs2, b':bs')
161 -- env accumulates down the list of binds, fvs accumulates upwards
162 (env1, fvs2, b' ) = coreTopBindToStg env fvs1 b
163 (env2, fvs1, bs') = coreTopBindsToStg env1 bs
168 -> FreeVarsInfo -- Info about the body
170 -> (IdEnv HowBound, FreeVarsInfo, StgBinding)
172 coreTopBindToStg env body_fvs (NonRec id rhs)
174 env' = extendVarEnv env id how_bound
175 how_bound = LetBound TopLet (manifestArity rhs)
179 coreToTopStgRhs 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)
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 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 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
232 :: FreeVarsInfo -- Free var info for the scope of the binding
234 -> LneM (StgRhs, FreeVarsInfo)
236 coreToTopStgRhs scope_fv_info (bndr, rhs)
237 = coreToStgExpr rhs `thenLne` \ (new_rhs, rhs_fvs, _) ->
238 freeVarsToLiveVars rhs_fvs `thenLne` \ lv_info ->
239 returnLne (mkTopStgRhs upd rhs_fvs (mkSRT lv_info) bndr_info new_rhs, rhs_fvs)
241 bndr_info = lookupFVInfo scope_fv_info bndr
243 upd | rhsIsNonUpd rhs = SingleEntry
244 | otherwise = Updatable
246 mkTopStgRhs :: UpdateFlag -> FreeVarsInfo -> SRT -> StgBinderInfo -> StgExpr
249 mkTopStgRhs upd rhs_fvs srt binder_info (StgLam _ bndrs body)
250 = StgRhsClosure noCCS binder_info
256 mkTopStgRhs upd rhs_fvs srt binder_info (StgConApp con args)
257 | not (isUpdatable upd) -- StgConApps can be updatable (see isCrossDllConApp)
258 = StgRhsCon noCCS con args
260 mkTopStgRhs upd rhs_fvs srt binder_info rhs
261 = StgRhsClosure noCCS binder_info
269 -- ---------------------------------------------------------------------------
271 -- ---------------------------------------------------------------------------
276 -> LneM (StgExpr, -- Decorated STG expr
277 FreeVarsInfo, -- Its free vars (NB free, not live)
278 EscVarsSet) -- Its escapees, a subset of its free vars;
279 -- also a subset of the domain of the envt
280 -- because we are only interested in the escapees
281 -- for vars which might be turned into
282 -- let-no-escaped ones.
285 The second and third components can be derived in a simple bottom up pass, not
286 dependent on any decisions about which variables will be let-no-escaped or
287 not. The first component, that is, the decorated expression, may then depend
288 on these components, but it in turn is not scrutinised as the basis for any
289 decisions. Hence no black holes.
292 coreToStgExpr (Lit l) = returnLne (StgLit l, emptyFVInfo, emptyVarSet)
293 coreToStgExpr (Var v) = coreToStgApp Nothing v []
295 coreToStgExpr expr@(App _ _)
296 = coreToStgApp Nothing f args
298 (f, args) = myCollectArgs expr
300 coreToStgExpr expr@(Lam _ _)
302 (args, body) = myCollectBinders expr
303 args' = filterStgBinders args
305 extendVarEnvLne [ (a, LambdaBound) | a <- args' ] $
306 coreToStgExpr body `thenLne` \ (body, body_fvs, body_escs) ->
308 fvs = args' `minusFVBinders` body_fvs
309 escs = body_escs `delVarSetList` args'
310 result_expr | null args' = body
311 | otherwise = StgLam (exprType expr) args' body
313 returnLne (result_expr, fvs, escs)
315 coreToStgExpr (Note (SCC cc) expr)
316 = coreToStgExpr expr `thenLne` ( \ (expr2, fvs, escs) ->
317 returnLne (StgSCC cc expr2, fvs, escs) )
320 -- For ILX, convert (__coerce__ to_ty from_ty e)
321 -- into (coerce to_ty from_ty e)
322 -- where coerce is real function
323 coreToStgExpr (Note (Coerce to_ty from_ty) expr)
324 = coreToStgExpr (mkApps (Var unsafeCoerceId)
325 [Type from_ty, Type to_ty, expr])
328 coreToStgExpr (Note other_note expr)
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) ->
336 returnLne ( mkStgAlts (idType bndr) alts2,
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)
371 scrut_fvs `unionFVInfo` alts_fvs_wo_bndr,
372 alts_escs_wo_bndr `unionVarSet` getFVSet scrut_fvs
373 -- You might think we should have scrut_escs, not
374 -- (getFVSet scrut_fvs), but actually we can't call, and
375 -- then return from, a let-no-escape thing.
378 vars_alt (con, binders, rhs)
379 = let -- Remove type variables
380 binders' = filterStgBinders binders
382 extendVarEnvLne [(b, LambdaBound) | b <- binders'] $
383 coreToStgExpr rhs `thenLne` \ (rhs2, rhs_fvs, rhs_escs) ->
385 -- Records whether each param is used in the RHS
386 good_use_mask = [ b `elementOfFVInfo` rhs_fvs | b <- binders' ]
388 returnLne ( (con, binders', good_use_mask, rhs2),
389 binders' `minusFVBinders` rhs_fvs,
390 rhs_escs `delVarSetList` binders' )
391 -- ToDo: remove the delVarSet;
392 -- since escs won't include any of these binders
395 Lets not only take quite a bit of work, but this is where we convert
396 then to let-no-escapes, if we wish.
398 (Meanwhile, we don't expect to see let-no-escapes...)
400 coreToStgExpr (Let bind body)
401 = fixLne (\ ~(_, _, _, no_binder_escapes) ->
402 coreToStgLet no_binder_escapes bind body
403 ) `thenLne` \ (new_let, fvs, escs, _) ->
405 returnLne (new_let, fvs, escs)
409 mkStgAlts scrut_ty orig_alts
410 | is_prim_case = StgPrimAlts (tyConAppTyCon scrut_ty) prim_alts deflt
411 | otherwise = StgAlgAlts maybe_tycon alg_alts deflt
413 is_prim_case = isUnLiftedType scrut_ty && not (isUnboxedTupleType scrut_ty)
415 prim_alts = [(lit, rhs) | (LitAlt lit, _, _, rhs) <- other_alts]
416 alg_alts = [(con, bndrs, use, rhs) | (DataAlt con, bndrs, use, rhs) <- other_alts]
419 = case orig_alts of -- DEFAULT is always first if it's there at all
420 (DEFAULT, _, _, rhs) : other_alts -> (other_alts, StgBindDefault rhs)
421 other -> (orig_alts, StgNoDefault)
423 maybe_tycon = case alg_alts of
424 -- Get the tycon from the data con
425 (dc, _, _, _) : _rest -> Just (dataConTyCon dc)
427 -- Otherwise just do your best
428 [] -> case splitTyConApp_maybe (repType scrut_ty) of
429 Just (tc,_) | isAlgTyCon tc -> Just tc
434 -- ---------------------------------------------------------------------------
436 -- ---------------------------------------------------------------------------
440 :: Maybe UpdateFlag -- Just upd <=> this application is
441 -- the rhs of a thunk binding
442 -- x = [...] \upd [] -> the_app
443 -- with specified update flag
445 -> [CoreArg] -- Arguments
446 -> LneM (StgExpr, FreeVarsInfo, EscVarsSet)
448 coreToStgApp maybe_thunk_body f args
449 = coreToStgArgs args `thenLne` \ (args', args_fvs) ->
450 lookupVarLne f `thenLne` \ how_bound ->
453 n_val_args = valArgCount args
454 not_letrec_bound = not (isLetBound how_bound)
456 = let fvs = singletonFVInfo f how_bound fun_occ in
457 -- e.g. (f :: a -> int) (x :: a)
458 -- Here the free variables are "f", "x" AND the type variable "a"
459 -- coreToStgArgs will deal with the arguments recursively
460 if opt_RuntimeTypes then
461 fvs `unionFVInfo` tyvarFVInfo (tyVarsOfType (varType f))
464 -- Mostly, the arity info of a function is in the fn's IdInfo
465 -- But new bindings introduced by CoreSat may not have no
466 -- arity info; it would do us no good anyway. For example:
467 -- let f = \ab -> e in f
468 -- No point in having correct arity info for f!
469 -- Hence the hasArity stuff below.
470 -- NB: f_arity is only consulted for LetBound things
471 f_arity = stgArity f how_bound
472 saturated = f_arity <= n_val_args
475 | not_letrec_bound = noBinderInfo -- Uninteresting variable
476 | f_arity > 0 && saturated = stgSatOcc -- Saturated or over-saturated function call
477 | otherwise = stgUnsatOcc -- Unsaturated function or thunk
480 | not_letrec_bound = emptyVarSet -- Only letrec-bound escapees are interesting
481 | f_arity == n_val_args = emptyVarSet -- A function *or thunk* with an exactly
482 -- saturated call doesn't escape
483 -- (let-no-escape applies to 'thunks' too)
485 | otherwise = unitVarSet f -- Inexact application; it does escape
487 -- At the moment of the call:
489 -- either the function is *not* let-no-escaped, in which case
490 -- nothing is live except live_in_cont
491 -- or the function *is* let-no-escaped in which case the
492 -- variables it uses are live, but still the function
493 -- itself is not. PS. In this case, the function's
494 -- live vars should already include those of the
495 -- continuation, but it does no harm to just union the
498 res_ty = exprType (mkApps (Var f) args)
499 app = case globalIdDetails f of
500 DataConWorkId dc | saturated -> StgConApp dc args'
501 PrimOpId op -> ASSERT( saturated )
502 StgOpApp (StgPrimOp op) args' res_ty
503 FCallId call -> ASSERT( saturated )
504 StgOpApp (StgFCallOp call (idUnique f)) args' res_ty
505 _other -> StgApp f args'
510 fun_fvs `unionFVInfo` args_fvs,
511 fun_escs `unionVarSet` (getFVSet args_fvs)
512 -- All the free vars of the args are disqualified
513 -- from being let-no-escaped.
518 -- ---------------------------------------------------------------------------
520 -- This is the guy that turns applications into A-normal form
521 -- ---------------------------------------------------------------------------
523 coreToStgArgs :: [CoreArg] -> LneM ([StgArg], FreeVarsInfo)
525 = returnLne ([], emptyFVInfo)
527 coreToStgArgs (Type ty : args) -- Type argument
528 = coreToStgArgs args `thenLne` \ (args', fvs) ->
529 if opt_RuntimeTypes then
530 returnLne (StgTypeArg ty : args', fvs `unionFVInfo` tyvarFVInfo (tyVarsOfType ty))
532 returnLne (args', fvs)
534 coreToStgArgs (arg : args) -- Non-type argument
535 = coreToStgArgs args `thenLne` \ (stg_args, args_fvs) ->
536 coreToStgExpr arg `thenLne` \ (arg', arg_fvs, escs) ->
538 fvs = args_fvs `unionFVInfo` arg_fvs
539 stg_arg = case arg' of
540 StgApp v [] -> StgVarArg v
541 StgConApp con [] -> StgVarArg (dataConWorkId con)
542 StgLit lit -> StgLitArg lit
543 _ -> pprPanic "coreToStgArgs" (ppr arg)
545 returnLne (stg_arg : stg_args, fvs)
548 -- ---------------------------------------------------------------------------
549 -- The magic for lets:
550 -- ---------------------------------------------------------------------------
553 :: Bool -- True <=> yes, we are let-no-escaping this let
554 -> CoreBind -- bindings
556 -> LneM (StgExpr, -- new let
557 FreeVarsInfo, -- variables free in the whole let
558 EscVarsSet, -- variables that escape from the whole let
559 Bool) -- True <=> none of the binders in the bindings
560 -- is among the escaping vars
562 coreToStgLet let_no_escape bind body
563 = fixLne (\ ~(_, _, _, _, _, rec_body_fvs, _, _) ->
565 -- Do the bindings, setting live_in_cont to empty if
566 -- we ain't in a let-no-escape world
567 getVarsLiveInCont `thenLne` \ live_in_cont ->
568 setVarsLiveInCont (if let_no_escape
571 (vars_bind rec_body_fvs bind)
572 `thenLne` \ ( bind2, bind_fvs, bind_escs, bind_lv_info, env_ext) ->
575 extendVarEnvLne env_ext (
576 coreToStgExpr body `thenLne` \(body2, body_fvs, body_escs) ->
577 freeVarsToLiveVars body_fvs `thenLne` \ body_lv_info ->
579 returnLne (bind2, bind_fvs, bind_escs, getLiveVars bind_lv_info,
580 body2, body_fvs, body_escs, getLiveVars body_lv_info)
583 ) `thenLne` (\ (bind2, bind_fvs, bind_escs, bind_lvs,
584 body2, body_fvs, body_escs, body_lvs) ->
587 -- Compute the new let-expression
589 new_let | let_no_escape = StgLetNoEscape live_in_whole_let bind_lvs bind2 body2
590 | otherwise = StgLet bind2 body2
593 = binders `minusFVBinders` (bind_fvs `unionFVInfo` body_fvs)
596 = bind_lvs `unionVarSet` (body_lvs `delVarSetList` binders)
598 real_bind_escs = if let_no_escape then
602 -- Everything escapes which is free in the bindings
604 let_escs = (real_bind_escs `unionVarSet` body_escs) `delVarSetList` binders
606 all_escs = bind_escs `unionVarSet` body_escs -- Still includes binders of
609 no_binder_escapes = isEmptyVarSet (set_of_binders `intersectVarSet` all_escs)
612 -- Debugging code as requested by Andrew Kennedy
613 checked_no_binder_escapes
614 | not no_binder_escapes && any is_join_var binders
615 = pprTrace "Interesting! A join var that isn't let-no-escaped" (ppr binders)
617 | otherwise = no_binder_escapes
619 checked_no_binder_escapes = no_binder_escapes
622 -- Mustn't depend on the passed-in let_no_escape flag, since
623 -- no_binder_escapes is used by the caller to derive the flag!
629 checked_no_binder_escapes
632 set_of_binders = mkVarSet binders
633 binders = bindersOf bind
635 mk_binding bind_lv_info binder rhs
636 = (binder, LetBound (NestedLet live_vars) (manifestArity rhs))
638 live_vars | let_no_escape = addLiveVar bind_lv_info binder
639 | otherwise = unitLiveVar binder
640 -- c.f. the invariant on NestedLet
642 vars_bind :: FreeVarsInfo -- Free var info for body of binding
646 EscVarsSet, -- free vars; escapee vars
647 LiveInfo, -- Vars and CAFs live in binding
648 [(Id, HowBound)]) -- extension to environment
651 vars_bind body_fvs (NonRec binder rhs)
652 = coreToStgRhs body_fvs [] (binder,rhs)
653 `thenLne` \ (rhs2, bind_fvs, bind_lv_info, escs) ->
655 env_ext_item = mk_binding bind_lv_info binder rhs
657 returnLne (StgNonRec binder rhs2,
658 bind_fvs, escs, bind_lv_info, [env_ext_item])
661 vars_bind body_fvs (Rec pairs)
662 = fixLne (\ ~(_, rec_rhs_fvs, _, bind_lv_info, _) ->
664 rec_scope_fvs = unionFVInfo body_fvs rec_rhs_fvs
665 binders = map fst pairs
666 env_ext = [ mk_binding bind_lv_info b rhs
669 extendVarEnvLne env_ext (
670 mapAndUnzip4Lne (coreToStgRhs rec_scope_fvs binders) pairs
671 `thenLne` \ (rhss2, fvss, lv_infos, escss) ->
673 bind_fvs = unionFVInfos fvss
674 bind_lv_info = foldr unionLiveInfo emptyLiveInfo lv_infos
675 escs = unionVarSets escss
677 returnLne (StgRec (binders `zip` rhss2),
678 bind_fvs, escs, bind_lv_info, env_ext)
682 is_join_var :: Id -> Bool
683 -- A hack (used only for compiler debuggging) to tell if
684 -- a variable started life as a join point ($j)
685 is_join_var j = occNameUserString (getOccName j) == "$j"
689 coreToStgRhs :: FreeVarsInfo -- Free var info for the scope of the binding
692 -> LneM (StgRhs, FreeVarsInfo, LiveInfo, EscVarsSet)
694 coreToStgRhs scope_fv_info binders (bndr, rhs)
695 = coreToStgExpr rhs `thenLne` \ (new_rhs, rhs_fvs, rhs_escs) ->
696 getEnvLne `thenLne` \ env ->
697 freeVarsToLiveVars (binders `minusFVBinders` rhs_fvs) `thenLne` \ lv_info ->
698 returnLne (mkStgRhs rhs_fvs (mkSRT lv_info) bndr_info new_rhs,
699 rhs_fvs, lv_info, rhs_escs)
701 bndr_info = lookupFVInfo scope_fv_info bndr
703 mkStgRhs :: FreeVarsInfo -> SRT -> StgBinderInfo -> StgExpr -> StgRhs
705 mkStgRhs rhs_fvs srt binder_info (StgConApp con args)
706 = StgRhsCon noCCS con args
708 mkStgRhs rhs_fvs srt binder_info (StgLam _ bndrs body)
709 = StgRhsClosure noCCS binder_info
714 mkStgRhs rhs_fvs srt binder_info rhs
715 = StgRhsClosure noCCS binder_info
721 SDM: disabled. Eval/Apply can't handle functions with arity zero very
722 well; and making these into simple non-updatable thunks breaks other
723 assumptions (namely that they will be entered only once).
725 upd_flag | isPAP env rhs = ReEntrant
726 | otherwise = Updatable
730 upd = if isOnceDem dem
731 then (if isNotTop toplev
732 then SingleEntry -- HA! Paydirt for "dem"
735 trace "WARNING: SE CAFs unsupported, forcing UPD instead" $
739 -- For now we forbid SingleEntry CAFs; they tickle the
740 -- ASSERT in rts/Storage.c line 215 at newCAF() re mut_link,
741 -- and I don't understand why. There's only one SE_CAF (well,
742 -- only one that tickled a great gaping bug in an earlier attempt
743 -- at ClosureInfo.getEntryConvention) in the whole of nofib,
744 -- specifically Main.lvl6 in spectral/cryptarithm2.
745 -- So no great loss. KSW 2000-07.
749 Detect thunks which will reduce immediately to PAPs, and make them
750 non-updatable. This has several advantages:
752 - the non-updatable thunk behaves exactly like the PAP,
754 - the thunk is more efficient to enter, because it is
755 specialised to the task.
757 - we save one update frame, one stg_update_PAP, one update
758 and lots of PAP_enters.
760 - in the case where the thunk is top-level, we save building
761 a black hole and futhermore the thunk isn't considered to
762 be a CAF any more, so it doesn't appear in any SRTs.
764 We do it here, because the arity information is accurate, and we need
765 to do it before the SRT pass to save the SRT entries associated with
768 isPAP env (StgApp f args) = listLengthCmp args arity == LT -- idArity f > length args
770 arity = stgArity f (lookupBinding env f)
774 %************************************************************************
776 \subsection[LNE-monad]{A little monad for this let-no-escaping pass}
778 %************************************************************************
780 There's a lot of stuff to pass around, so we use this @LneM@ monad to
781 help. All the stuff here is only passed *down*.
784 type LneM a = IdEnv HowBound
785 -> LiveInfo -- Vars and CAFs live in continuation
788 type LiveInfo = (StgLiveVars, -- Dynamic live variables;
789 -- i.e. ones with a nested (non-top-level) binding
790 CafSet) -- Static live variables;
791 -- i.e. top-level variables that are CAFs or refer to them
793 type EscVarsSet = IdSet
797 = ImportBound -- Used only as a response to lookupBinding; never
798 -- exists in the range of the (IdEnv HowBound)
800 | LetBound -- A let(rec) in this module
801 LetInfo -- Whether top level or nested
802 Arity -- Its arity (local Ids don't have arity info at this point)
804 | LambdaBound -- Used for both lambda and case
807 = TopLet -- top level things
808 | NestedLet LiveInfo -- For nested things, what is live if this
809 -- thing is live? Invariant: the binder
810 -- itself is always a member of
811 -- the dynamic set of its own LiveInfo
813 isLetBound (LetBound _ _) = True
814 isLetBound other = False
816 topLevelBound ImportBound = True
817 topLevelBound (LetBound TopLet _) = True
818 topLevelBound other = False
821 For a let(rec)-bound variable, x, we record LiveInfo, the set of
822 variables that are live if x is live. This LiveInfo comprises
823 (a) dynamic live variables (ones with a non-top-level binding)
824 (b) static live variabes (CAFs or things that refer to CAFs)
826 For "normal" variables (a) is just x alone. If x is a let-no-escaped
827 variable then x is represented by a code pointer and a stack pointer
828 (well, one for each stack). So all of the variables needed in the
829 execution of x are live if x is, and are therefore recorded in the
830 LetBound constructor; x itself *is* included.
832 The set of dynamic live variables is guaranteed ot have no further let-no-escaped
836 emptyLiveInfo :: LiveInfo
837 emptyLiveInfo = (emptyVarSet,emptyVarSet)
839 unitLiveVar :: Id -> LiveInfo
840 unitLiveVar lv = (unitVarSet lv, emptyVarSet)
842 unitLiveCaf :: Id -> LiveInfo
843 unitLiveCaf caf = (emptyVarSet, unitVarSet caf)
845 addLiveVar :: LiveInfo -> Id -> LiveInfo
846 addLiveVar (lvs, cafs) id = (lvs `extendVarSet` id, cafs)
848 unionLiveInfo :: LiveInfo -> LiveInfo -> LiveInfo
849 unionLiveInfo (lv1,caf1) (lv2,caf2) = (lv1 `unionVarSet` lv2, caf1 `unionVarSet` caf2)
851 mkSRT :: LiveInfo -> SRT
852 mkSRT (_, cafs) = SRTEntries cafs
854 getLiveVars :: LiveInfo -> StgLiveVars
855 getLiveVars (lvs, _) = lvs
859 The std monad functions:
861 initLne :: IdEnv HowBound -> LneM a -> a
862 initLne env m = m env emptyLiveInfo
866 {-# INLINE thenLne #-}
867 {-# INLINE returnLne #-}
869 returnLne :: a -> LneM a
870 returnLne e env lvs_cont = e
872 thenLne :: LneM a -> (a -> LneM b) -> LneM b
873 thenLne m k env lvs_cont
874 = k (m env lvs_cont) env lvs_cont
876 mapLne :: (a -> LneM b) -> [a] -> LneM [b]
877 mapLne f [] = returnLne []
879 = f x `thenLne` \ r ->
880 mapLne f xs `thenLne` \ rs ->
883 mapAndUnzipLne :: (a -> LneM (b,c)) -> [a] -> LneM ([b],[c])
885 mapAndUnzipLne f [] = returnLne ([],[])
886 mapAndUnzipLne f (x:xs)
887 = f x `thenLne` \ (r1, r2) ->
888 mapAndUnzipLne f xs `thenLne` \ (rs1, rs2) ->
889 returnLne (r1:rs1, r2:rs2)
891 mapAndUnzip3Lne :: (a -> LneM (b,c,d)) -> [a] -> LneM ([b],[c],[d])
893 mapAndUnzip3Lne f [] = returnLne ([],[],[])
894 mapAndUnzip3Lne f (x:xs)
895 = f x `thenLne` \ (r1, r2, r3) ->
896 mapAndUnzip3Lne f xs `thenLne` \ (rs1, rs2, rs3) ->
897 returnLne (r1:rs1, r2:rs2, r3:rs3)
899 mapAndUnzip4Lne :: (a -> LneM (b,c,d,e)) -> [a] -> LneM ([b],[c],[d],[e])
901 mapAndUnzip4Lne f [] = returnLne ([],[],[],[])
902 mapAndUnzip4Lne f (x:xs)
903 = f x `thenLne` \ (r1, r2, r3, r4) ->
904 mapAndUnzip4Lne f xs `thenLne` \ (rs1, rs2, rs3, rs4) ->
905 returnLne (r1:rs1, r2:rs2, r3:rs3, r4:rs4)
907 fixLne :: (a -> LneM a) -> LneM a
908 fixLne expr env lvs_cont
911 result = expr result env lvs_cont
914 Functions specific to this monad:
917 getVarsLiveInCont :: LneM LiveInfo
918 getVarsLiveInCont env lvs_cont = lvs_cont
920 setVarsLiveInCont :: LiveInfo -> LneM a -> LneM a
921 setVarsLiveInCont new_lvs_cont expr env lvs_cont
922 = expr env new_lvs_cont
924 extendVarEnvLne :: [(Id, HowBound)] -> LneM a -> LneM a
925 extendVarEnvLne ids_w_howbound expr env lvs_cont
926 = expr (extendVarEnvList env ids_w_howbound) lvs_cont
928 lookupVarLne :: Id -> LneM HowBound
929 lookupVarLne v env lvs_cont = returnLne (lookupBinding env v) env lvs_cont
931 getEnvLne :: LneM (IdEnv HowBound)
932 getEnvLne env lvs_cont = returnLne env env lvs_cont
934 lookupBinding :: IdEnv HowBound -> Id -> HowBound
935 lookupBinding env v = case lookupVarEnv env v of
937 Nothing -> ASSERT2( isGlobalId v, ppr v ) ImportBound
940 -- The result of lookupLiveVarsForSet, a set of live variables, is
941 -- only ever tacked onto a decorated expression. It is never used as
942 -- the basis of a control decision, which might give a black hole.
944 freeVarsToLiveVars :: FreeVarsInfo -> LneM LiveInfo
945 freeVarsToLiveVars fvs env live_in_cont
946 = returnLne live_info env live_in_cont
948 live_info = foldr unionLiveInfo live_in_cont lvs_from_fvs
949 lvs_from_fvs = map do_one (allFreeIds fvs)
951 do_one (v, how_bound)
953 ImportBound -> unitLiveCaf v -- Only CAF imports are
956 | mayHaveCafRefs (idCafInfo v) -> unitLiveCaf v
957 | otherwise -> emptyLiveInfo
959 LetBound (NestedLet lvs) _ -> lvs -- lvs already contains v
960 -- (see the invariant on NestedLet)
962 _lambda_or_case_binding -> unitLiveVar v -- Bound by lambda or case
965 %************************************************************************
967 \subsection[Free-var info]{Free variable information}
969 %************************************************************************
972 type FreeVarsInfo = VarEnv (Var, HowBound, StgBinderInfo)
973 -- The Var is so we can gather up the free variables
976 -- The HowBound info just saves repeated lookups;
977 -- we look up just once when we encounter the occurrence.
978 -- INVARIANT: Any ImportBound Ids are HaveCafRef Ids
979 -- Imported Ids without CAF refs are simply
980 -- not put in the FreeVarsInfo for an expression.
981 -- See singletonFVInfo and freeVarsToLiveVars
983 -- StgBinderInfo records how it occurs; notably, we
984 -- are interested in whether it only occurs in saturated
985 -- applications, because then we don't need to build a
987 -- If f is mapped to noBinderInfo, that means
988 -- that f *is* mentioned (else it wouldn't be in the
989 -- IdEnv at all), but perhaps in an unsaturated applications.
991 -- All case/lambda-bound things are also mapped to
992 -- noBinderInfo, since we aren't interested in their
995 -- For ILX we track free var info for type variables too;
996 -- hence VarEnv not IdEnv
1000 emptyFVInfo :: FreeVarsInfo
1001 emptyFVInfo = emptyVarEnv
1003 singletonFVInfo :: Id -> HowBound -> StgBinderInfo -> FreeVarsInfo
1004 -- Don't record non-CAF imports at all, to keep free-var sets small
1005 singletonFVInfo id ImportBound info
1006 | mayHaveCafRefs (idCafInfo id) = unitVarEnv id (id, ImportBound, info)
1007 | otherwise = emptyVarEnv
1008 singletonFVInfo id how_bound info = unitVarEnv id (id, how_bound, info)
1010 tyvarFVInfo :: TyVarSet -> FreeVarsInfo
1011 tyvarFVInfo tvs = foldVarSet add emptyFVInfo tvs
1013 add tv fvs = extendVarEnv fvs tv (tv, LambdaBound, noBinderInfo)
1014 -- Type variables must be lambda-bound
1016 unionFVInfo :: FreeVarsInfo -> FreeVarsInfo -> FreeVarsInfo
1017 unionFVInfo fv1 fv2 = plusVarEnv_C plusFVInfo fv1 fv2
1019 unionFVInfos :: [FreeVarsInfo] -> FreeVarsInfo
1020 unionFVInfos fvs = foldr unionFVInfo emptyFVInfo fvs
1022 minusFVBinders :: [Id] -> FreeVarsInfo -> FreeVarsInfo
1023 minusFVBinders vs fv = foldr minusFVBinder fv vs
1025 minusFVBinder :: Id -> FreeVarsInfo -> FreeVarsInfo
1026 minusFVBinder v fv | isId v && opt_RuntimeTypes
1027 = (fv `delVarEnv` v) `unionFVInfo`
1028 tyvarFVInfo (tyVarsOfType (idType v))
1029 | otherwise = fv `delVarEnv` v
1030 -- When removing a binder, remember to add its type variables
1031 -- c.f. CoreFVs.delBinderFV
1033 elementOfFVInfo :: Id -> FreeVarsInfo -> Bool
1034 elementOfFVInfo id fvs = maybeToBool (lookupVarEnv fvs id)
1036 lookupFVInfo :: FreeVarsInfo -> Id -> StgBinderInfo
1037 -- Find how the given Id is used.
1038 -- Externally visible things may be used any old how
1040 | isExternalName (idName id) = noBinderInfo
1041 | otherwise = case lookupVarEnv fvs id of
1042 Nothing -> noBinderInfo
1043 Just (_,_,info) -> info
1045 allFreeIds :: FreeVarsInfo -> [(Id,HowBound)] -- Both top level and non-top-level Ids
1046 allFreeIds fvs = [(id,how_bound) | (id,how_bound,_) <- rngVarEnv fvs, isId id]
1048 -- Non-top-level things only, both type variables and ids
1049 -- (type variables only if opt_RuntimeTypes)
1050 getFVs :: FreeVarsInfo -> [Var]
1051 getFVs fvs = [id | (id, how_bound, _) <- rngVarEnv fvs,
1052 not (topLevelBound how_bound) ]
1054 getFVSet :: FreeVarsInfo -> VarSet
1055 getFVSet fvs = mkVarSet (getFVs fvs)
1057 plusFVInfo (id1,hb1,info1) (id2,hb2,info2)
1058 = ASSERT (id1 == id2 && hb1 `check_eq_how_bound` hb2)
1059 (id1, hb1, combineStgBinderInfo info1 info2)
1062 -- The HowBound info for a variable in the FVInfo should be consistent
1063 check_eq_how_bound ImportBound ImportBound = True
1064 check_eq_how_bound LambdaBound LambdaBound = True
1065 check_eq_how_bound (LetBound li1 ar1) (LetBound li2 ar2) = ar1 == ar2 && check_eq_li li1 li2
1066 check_eq_how_bound hb1 hb2 = False
1068 check_eq_li (NestedLet _) (NestedLet _) = True
1069 check_eq_li TopLet TopLet = True
1070 check_eq_li li1 li2 = False
1076 filterStgBinders :: [Var] -> [Var]
1077 filterStgBinders bndrs
1078 | opt_RuntimeTypes = bndrs
1079 | otherwise = filter isId bndrs
1084 -- Ignore all notes except SCC
1085 myCollectBinders expr
1088 go bs (Lam b e) = go (b:bs) e
1089 go bs e@(Note (SCC _) _) = (reverse bs, e)
1090 go bs (Note _ e) = go bs e
1091 go bs e = (reverse bs, e)
1093 myCollectArgs :: CoreExpr -> (Id, [CoreArg])
1094 -- We assume that we only have variables
1095 -- in the function position by now
1099 go (Var v) as = (v, as)
1100 go (App f a) as = go f (a:as)
1101 go (Note (SCC _) e) as = pprPanic "CoreToStg.myCollectArgs" (ppr expr)
1102 go (Note n e) as = go e as
1103 go _ as = pprPanic "CoreToStg.myCollectArgs" (ppr expr)
1107 stgArity :: Id -> HowBound -> Arity
1108 stgArity f (LetBound _ arity) = arity
1109 stgArity f ImportBound = idArity f
1110 stgArity f LambdaBound = 0