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 Coercion ( mkUnsafeCoercion )
20 import TyCon ( isAlgTyCon )
22 import Var ( Var, globalIdDetails, idType )
23 import TyCon ( isUnboxedTupleTyCon, isPrimTyCon, isFunTyCon, isHiBootTyCon )
25 import MkId ( unsafeCoerceId )
29 import CostCentre ( noCCS )
32 import Maybes ( maybeToBool )
33 import Name ( getOccName, isExternalName, nameOccName )
34 import OccName ( occNameString, occNameFS )
35 import BasicTypes ( Arity )
36 import StaticFlags ( opt_RuntimeTypes )
37 import PackageConfig ( PackageId )
43 %************************************************************************
45 \subsection[live-vs-free-doc]{Documentation}
47 %************************************************************************
49 (There is other relevant documentation in codeGen/CgLetNoEscape.)
51 The actual Stg datatype is decorated with {\em live variable}
52 information, as well as {\em free variable} information. The two are
53 {\em not} the same. Liveness is an operational property rather than a
54 semantic one. A variable is live at a particular execution point if
55 it can be referred to {\em directly} again. In particular, a dead
56 variable's stack slot (if it has one):
59 should be stubbed to avoid space leaks, and
61 may be reused for something else.
64 There ought to be a better way to say this. Here are some examples:
71 Just after the `in', v is live, but q is dead. If the whole of that
72 let expression was enclosed in a case expression, thus:
74 case (let v = [q] \[x] -> e in ...v...) of
77 (ie @alts@ mention @q@), then @q@ is live even after the `in'; because
78 we'll return later to the @alts@ and need it.
80 Let-no-escapes make this a bit more interesting:
82 let-no-escape v = [q] \ [x] -> e
86 Here, @q@ is still live at the `in', because @v@ is represented not by
87 a closure but by the current stack state. In other words, if @v@ is
88 live then so is @q@. Furthermore, if @e@ mentions an enclosing
89 let-no-escaped variable, then {\em its} free variables are also live
92 %************************************************************************
94 \subsection[caf-info]{Collecting live CAF info}
96 %************************************************************************
98 In this pass we also collect information on which CAFs are live for
99 constructing SRTs (see SRT.lhs).
101 A top-level Id has CafInfo, which is
103 - MayHaveCafRefs, if it may refer indirectly to
105 - NoCafRefs if it definitely doesn't
107 The CafInfo has already been calculated during the CoreTidy pass.
109 During CoreToStg, we then pin onto each binding and case expression, a
110 list of Ids which represents the "live" CAFs at that point. The meaning
111 of "live" here is the same as for live variables, see above (which is
112 why it's convenient to collect CAF information here rather than elsewhere).
114 The later SRT pass takes these lists of Ids and uses them to construct
115 the actual nested SRTs, and replaces the lists of Ids with (offset,length)
119 Interaction of let-no-escape with SRTs [Sept 01]
120 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
123 let-no-escape x = ...caf1...caf2...
127 where caf1,caf2 are CAFs. Since x doesn't have a closure, we
128 build SRTs just as if x's defn was inlined at each call site, and
129 that means that x's CAF refs get duplicated in the overall SRT.
131 This is unlike ordinary lets, in which the CAF refs are not duplicated.
133 We could fix this loss of (static) sharing by making a sort of pseudo-closure
134 for x, solely to put in the SRTs lower down.
137 %************************************************************************
139 \subsection[binds-StgVarInfo]{Setting variable info: top-level, binds, RHSs}
141 %************************************************************************
144 coreToStg :: PackageId -> [CoreBind] -> IO [StgBinding]
145 coreToStg this_pkg pgm
147 where (_, _, pgm') = coreTopBindsToStg this_pkg emptyVarEnv pgm
149 coreExprToStg :: CoreExpr -> StgExpr
151 = new_expr where (new_expr,_,_) = initLne emptyVarEnv (coreToStgExpr expr)
156 -> IdEnv HowBound -- environment for the bindings
158 -> (IdEnv HowBound, FreeVarsInfo, [StgBinding])
160 coreTopBindsToStg this_pkg env [] = (env, emptyFVInfo, [])
161 coreTopBindsToStg this_pkg env (b:bs)
162 = (env2, fvs2, b':bs')
164 -- env accumulates down the list of binds, fvs accumulates upwards
165 (env1, fvs2, b' ) = coreTopBindToStg this_pkg env fvs1 b
166 (env2, fvs1, bs') = coreTopBindsToStg this_pkg env1 bs
172 -> FreeVarsInfo -- Info about the body
174 -> (IdEnv HowBound, FreeVarsInfo, StgBinding)
176 coreTopBindToStg this_pkg env body_fvs (NonRec id rhs)
178 env' = extendVarEnv env id how_bound
179 how_bound = LetBound TopLet $! manifestArity rhs
183 coreToTopStgRhs this_pkg body_fvs (id,rhs) `thenLne` \ (stg_rhs, fvs') ->
184 returnLne (stg_rhs, fvs')
187 bind = StgNonRec id stg_rhs
189 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) )
190 ASSERT2(consistentCafInfo id bind, ppr id)
191 -- WARN(not (consistent caf_info bind), ppr id <+> ppr cafs <+> ppCafInfo caf_info)
192 (env', fvs' `unionFVInfo` body_fvs, bind)
194 coreTopBindToStg this_pkg env body_fvs (Rec pairs)
196 (binders, rhss) = unzip pairs
198 extra_env' = [ (b, LetBound TopLet $! manifestArity rhs)
199 | (b, rhs) <- pairs ]
200 env' = extendVarEnvList env extra_env'
204 mapAndUnzipLne (coreToTopStgRhs this_pkg body_fvs) pairs
205 `thenLne` \ (stg_rhss, fvss') ->
206 let fvs' = unionFVInfos fvss' in
207 returnLne (stg_rhss, fvs')
210 bind = StgRec (zip binders stg_rhss)
212 ASSERT2(and [manifestArity rhs == stgRhsArity stg_rhs | (rhs,stg_rhs) <- rhss `zip` stg_rhss], ppr binders)
213 ASSERT2(consistentCafInfo (head binders) bind, ppr binders)
214 (env', fvs' `unionFVInfo` body_fvs, bind)
217 -- Assertion helper: this checks that the CafInfo on the Id matches
218 -- what CoreToStg has figured out about the binding's SRT. The
219 -- CafInfo will be exact in all cases except when CorePrep has
220 -- floated out a binding, in which case it will be approximate.
221 consistentCafInfo id bind
222 | occNameFS (nameOccName (idName id)) == FSLIT("sat")
225 = WARN (not exact, ppr id) safe
227 safe = id_marked_caffy || not binding_is_caffy
228 exact = id_marked_caffy == binding_is_caffy
229 id_marked_caffy = mayHaveCafRefs (idCafInfo id)
230 binding_is_caffy = stgBindHasCafRefs bind
237 -> FreeVarsInfo -- Free var info for the scope of the binding
239 -> LneM (StgRhs, FreeVarsInfo)
241 coreToTopStgRhs this_pkg scope_fv_info (bndr, rhs)
242 = coreToStgExpr rhs `thenLne` \ (new_rhs, rhs_fvs, _) ->
243 freeVarsToLiveVars rhs_fvs `thenLne` \ lv_info ->
244 returnLne (mkTopStgRhs is_static rhs_fvs (mkSRT lv_info) bndr_info new_rhs, rhs_fvs)
246 bndr_info = lookupFVInfo scope_fv_info bndr
247 is_static = rhsIsStatic this_pkg rhs
249 mkTopStgRhs :: Bool -> FreeVarsInfo -> SRT -> StgBinderInfo -> StgExpr
252 mkTopStgRhs is_static rhs_fvs srt binder_info (StgLam _ bndrs body)
253 = ASSERT( is_static )
254 StgRhsClosure noCCS binder_info
260 mkTopStgRhs is_static rhs_fvs srt binder_info (StgConApp con args)
261 | is_static -- StgConApps can be updatable (see isCrossDllConApp)
262 = StgRhsCon noCCS con args
264 mkTopStgRhs is_static rhs_fvs srt binder_info rhs
265 = ASSERT2( not is_static, ppr rhs )
266 StgRhsClosure noCCS binder_info
274 -- ---------------------------------------------------------------------------
276 -- ---------------------------------------------------------------------------
281 -> LneM (StgExpr, -- Decorated STG expr
282 FreeVarsInfo, -- Its free vars (NB free, not live)
283 EscVarsSet) -- Its escapees, a subset of its free vars;
284 -- also a subset of the domain of the envt
285 -- because we are only interested in the escapees
286 -- for vars which might be turned into
287 -- let-no-escaped ones.
290 The second and third components can be derived in a simple bottom up pass, not
291 dependent on any decisions about which variables will be let-no-escaped or
292 not. The first component, that is, the decorated expression, may then depend
293 on these components, but it in turn is not scrutinised as the basis for any
294 decisions. Hence no black holes.
297 coreToStgExpr (Lit l) = returnLne (StgLit l, emptyFVInfo, emptyVarSet)
298 coreToStgExpr (Var v) = coreToStgApp Nothing v []
300 coreToStgExpr expr@(App _ _)
301 = coreToStgApp Nothing f args
303 (f, args) = myCollectArgs expr
305 coreToStgExpr expr@(Lam _ _)
307 (args, body) = myCollectBinders expr
308 args' = filterStgBinders args
310 extendVarEnvLne [ (a, LambdaBound) | a <- args' ] $
311 coreToStgExpr body `thenLne` \ (body, body_fvs, body_escs) ->
313 fvs = args' `minusFVBinders` body_fvs
314 escs = body_escs `delVarSetList` args'
315 result_expr | null args' = body
316 | otherwise = StgLam (exprType expr) args' body
318 returnLne (result_expr, fvs, escs)
320 coreToStgExpr (Note (SCC cc) expr)
321 = coreToStgExpr expr `thenLne` ( \ (expr2, fvs, escs) ->
322 returnLne (StgSCC cc expr2, fvs, escs) )
325 -- For ILX, convert (__coerce__ to_ty from_ty e)
326 -- into (coerce to_ty from_ty e)
327 -- where coerce is real function
328 coreToStgExpr (Cast expr co)
329 = let (from_ty, ty_ty) = coercionKind co in
330 coreToStgExpr (mkApps (Var unsafeCoerceId)
331 [Type from_ty, Type to_ty, expr])
334 coreToStgExpr (Note other_note expr)
337 coreToStgExpr (Cast expr co)
340 -- Cases require a little more real work.
342 coreToStgExpr (Case scrut bndr _ alts)
343 = extendVarEnvLne [(bndr, LambdaBound)] (
344 mapAndUnzip3Lne vars_alt alts `thenLne` \ (alts2, fvs_s, escs_s) ->
347 unionVarSets escs_s )
348 ) `thenLne` \ (alts2, alts_fvs, alts_escs) ->
350 -- Determine whether the default binder is dead or not
351 -- This helps the code generator to avoid generating an assignment
352 -- for the case binder (is extremely rare cases) ToDo: remove.
353 bndr' | bndr `elementOfFVInfo` alts_fvs = bndr
354 | otherwise = bndr `setIdOccInfo` IAmDead
356 -- Don't consider the default binder as being 'live in alts',
357 -- since this is from the point of view of the case expr, where
358 -- the default binder is not free.
359 alts_fvs_wo_bndr = bndr `minusFVBinder` alts_fvs
360 alts_escs_wo_bndr = alts_escs `delVarSet` bndr
363 freeVarsToLiveVars alts_fvs_wo_bndr `thenLne` \ alts_lv_info ->
365 -- We tell the scrutinee that everything
366 -- live in the alts is live in it, too.
367 setVarsLiveInCont alts_lv_info (
368 coreToStgExpr scrut `thenLne` \ (scrut2, scrut_fvs, scrut_escs) ->
369 freeVarsToLiveVars scrut_fvs `thenLne` \ scrut_lv_info ->
370 returnLne (scrut2, scrut_fvs, scrut_escs, scrut_lv_info)
372 `thenLne` \ (scrut2, scrut_fvs, scrut_escs, scrut_lv_info) ->
375 StgCase scrut2 (getLiveVars scrut_lv_info)
376 (getLiveVars alts_lv_info)
379 (mkStgAltType (idType bndr) alts)
381 scrut_fvs `unionFVInfo` alts_fvs_wo_bndr,
382 alts_escs_wo_bndr `unionVarSet` getFVSet scrut_fvs
383 -- You might think we should have scrut_escs, not
384 -- (getFVSet scrut_fvs), but actually we can't call, and
385 -- then return from, a let-no-escape thing.
388 vars_alt (con, binders, rhs)
389 = let -- Remove type variables
390 binders' = filterStgBinders binders
392 extendVarEnvLne [(b, LambdaBound) | b <- binders'] $
393 coreToStgExpr rhs `thenLne` \ (rhs2, rhs_fvs, rhs_escs) ->
395 -- Records whether each param is used in the RHS
396 good_use_mask = [ b `elementOfFVInfo` rhs_fvs | b <- binders' ]
398 returnLne ( (con, binders', good_use_mask, rhs2),
399 binders' `minusFVBinders` rhs_fvs,
400 rhs_escs `delVarSetList` binders' )
401 -- ToDo: remove the delVarSet;
402 -- since escs won't include any of these binders
405 Lets not only take quite a bit of work, but this is where we convert
406 then to let-no-escapes, if we wish.
408 (Meanwhile, we don't expect to see let-no-escapes...)
410 coreToStgExpr (Let bind body)
411 = fixLne (\ ~(_, _, _, no_binder_escapes) ->
412 coreToStgLet no_binder_escapes bind body
413 ) `thenLne` \ (new_let, fvs, escs, _) ->
415 returnLne (new_let, fvs, escs)
419 mkStgAltType scrut_ty alts
420 = case splitTyConApp_maybe (repType scrut_ty) of
421 Just (tc,_) | isUnboxedTupleTyCon tc -> UbxTupAlt tc
422 | isPrimTyCon tc -> PrimAlt tc
423 | isHiBootTyCon tc -> look_for_better_tycon
424 | isAlgTyCon tc -> AlgAlt tc
425 | isFunTyCon tc -> PolyAlt
426 | otherwise -> pprPanic "mkStgAlts" (ppr tc)
430 -- Sometimes, the TyCon in the type of the scrutinee is an HiBootTyCon,
431 -- which may not have any constructors inside it. If so, then we
432 -- can get a better TyCon by grabbing the one from a constructor alternative
434 look_for_better_tycon
435 | ((DataAlt con, _, _) : _) <- data_alts =
436 AlgAlt (dataConTyCon con)
438 ASSERT(null data_alts)
441 (data_alts, _deflt) = findDefault alts
445 -- ---------------------------------------------------------------------------
447 -- ---------------------------------------------------------------------------
451 :: Maybe UpdateFlag -- Just upd <=> this application is
452 -- the rhs of a thunk binding
453 -- x = [...] \upd [] -> the_app
454 -- with specified update flag
456 -> [CoreArg] -- Arguments
457 -> LneM (StgExpr, FreeVarsInfo, EscVarsSet)
459 coreToStgApp maybe_thunk_body f args
460 = coreToStgArgs args `thenLne` \ (args', args_fvs) ->
461 lookupVarLne f `thenLne` \ how_bound ->
464 n_val_args = valArgCount args
465 not_letrec_bound = not (isLetBound how_bound)
467 = let fvs = singletonFVInfo f how_bound fun_occ in
468 -- e.g. (f :: a -> int) (x :: a)
469 -- Here the free variables are "f", "x" AND the type variable "a"
470 -- coreToStgArgs will deal with the arguments recursively
471 if opt_RuntimeTypes then
472 fvs `unionFVInfo` tyvarFVInfo (tyVarsOfType (idType f))
475 -- Mostly, the arity info of a function is in the fn's IdInfo
476 -- But new bindings introduced by CoreSat may not have no
477 -- arity info; it would do us no good anyway. For example:
478 -- let f = \ab -> e in f
479 -- No point in having correct arity info for f!
480 -- Hence the hasArity stuff below.
481 -- NB: f_arity is only consulted for LetBound things
482 f_arity = stgArity f how_bound
483 saturated = f_arity <= n_val_args
486 | not_letrec_bound = noBinderInfo -- Uninteresting variable
487 | f_arity > 0 && saturated = stgSatOcc -- Saturated or over-saturated function call
488 | otherwise = stgUnsatOcc -- Unsaturated function or thunk
491 | not_letrec_bound = emptyVarSet -- Only letrec-bound escapees are interesting
492 | f_arity == n_val_args = emptyVarSet -- A function *or thunk* with an exactly
493 -- saturated call doesn't escape
494 -- (let-no-escape applies to 'thunks' too)
496 | otherwise = unitVarSet f -- Inexact application; it does escape
498 -- At the moment of the call:
500 -- either the function is *not* let-no-escaped, in which case
501 -- nothing is live except live_in_cont
502 -- or the function *is* let-no-escaped in which case the
503 -- variables it uses are live, but still the function
504 -- itself is not. PS. In this case, the function's
505 -- live vars should already include those of the
506 -- continuation, but it does no harm to just union the
509 res_ty = exprType (mkApps (Var f) args)
510 app = case globalIdDetails f of
511 DataConWorkId dc | saturated -> StgConApp dc args'
512 PrimOpId op -> ASSERT( saturated )
513 StgOpApp (StgPrimOp op) args' res_ty
514 FCallId call -> ASSERT( saturated )
515 StgOpApp (StgFCallOp call (idUnique f)) args' res_ty
516 _other -> StgApp f args'
521 fun_fvs `unionFVInfo` args_fvs,
522 fun_escs `unionVarSet` (getFVSet args_fvs)
523 -- All the free vars of the args are disqualified
524 -- from being let-no-escaped.
529 -- ---------------------------------------------------------------------------
531 -- This is the guy that turns applications into A-normal form
532 -- ---------------------------------------------------------------------------
534 coreToStgArgs :: [CoreArg] -> LneM ([StgArg], FreeVarsInfo)
536 = returnLne ([], emptyFVInfo)
538 coreToStgArgs (Type ty : args) -- Type argument
539 = coreToStgArgs args `thenLne` \ (args', fvs) ->
540 if opt_RuntimeTypes then
541 returnLne (StgTypeArg ty : args', fvs `unionFVInfo` tyvarFVInfo (tyVarsOfType ty))
543 returnLne (args', fvs)
545 coreToStgArgs (arg : args) -- Non-type argument
546 = coreToStgArgs args `thenLne` \ (stg_args, args_fvs) ->
547 coreToStgExpr arg `thenLne` \ (arg', arg_fvs, escs) ->
549 fvs = args_fvs `unionFVInfo` arg_fvs
550 stg_arg = case arg' of
551 StgApp v [] -> StgVarArg v
552 StgConApp con [] -> StgVarArg (dataConWorkId con)
553 StgLit lit -> StgLitArg lit
554 _ -> pprPanic "coreToStgArgs" (ppr arg)
556 returnLne (stg_arg : stg_args, fvs)
559 -- ---------------------------------------------------------------------------
560 -- The magic for lets:
561 -- ---------------------------------------------------------------------------
564 :: Bool -- True <=> yes, we are let-no-escaping this let
565 -> CoreBind -- bindings
567 -> LneM (StgExpr, -- new let
568 FreeVarsInfo, -- variables free in the whole let
569 EscVarsSet, -- variables that escape from the whole let
570 Bool) -- True <=> none of the binders in the bindings
571 -- is among the escaping vars
573 coreToStgLet let_no_escape bind body
574 = fixLne (\ ~(_, _, _, _, _, rec_body_fvs, _, _) ->
576 -- Do the bindings, setting live_in_cont to empty if
577 -- we ain't in a let-no-escape world
578 getVarsLiveInCont `thenLne` \ live_in_cont ->
579 setVarsLiveInCont (if let_no_escape
582 (vars_bind rec_body_fvs bind)
583 `thenLne` \ ( bind2, bind_fvs, bind_escs, bind_lv_info, env_ext) ->
586 extendVarEnvLne env_ext (
587 coreToStgExpr body `thenLne` \(body2, body_fvs, body_escs) ->
588 freeVarsToLiveVars body_fvs `thenLne` \ body_lv_info ->
590 returnLne (bind2, bind_fvs, bind_escs, getLiveVars bind_lv_info,
591 body2, body_fvs, body_escs, getLiveVars body_lv_info)
594 ) `thenLne` (\ (bind2, bind_fvs, bind_escs, bind_lvs,
595 body2, body_fvs, body_escs, body_lvs) ->
598 -- Compute the new let-expression
600 new_let | let_no_escape = StgLetNoEscape live_in_whole_let bind_lvs bind2 body2
601 | otherwise = StgLet bind2 body2
604 = binders `minusFVBinders` (bind_fvs `unionFVInfo` body_fvs)
607 = bind_lvs `unionVarSet` (body_lvs `delVarSetList` binders)
609 real_bind_escs = if let_no_escape then
613 -- Everything escapes which is free in the bindings
615 let_escs = (real_bind_escs `unionVarSet` body_escs) `delVarSetList` binders
617 all_escs = bind_escs `unionVarSet` body_escs -- Still includes binders of
620 no_binder_escapes = isEmptyVarSet (set_of_binders `intersectVarSet` all_escs)
623 -- Debugging code as requested by Andrew Kennedy
624 checked_no_binder_escapes
625 | not no_binder_escapes && any is_join_var binders
626 = pprTrace "Interesting! A join var that isn't let-no-escaped" (ppr binders)
628 | otherwise = no_binder_escapes
630 checked_no_binder_escapes = no_binder_escapes
633 -- Mustn't depend on the passed-in let_no_escape flag, since
634 -- no_binder_escapes is used by the caller to derive the flag!
640 checked_no_binder_escapes
643 set_of_binders = mkVarSet binders
644 binders = bindersOf bind
646 mk_binding bind_lv_info binder rhs
647 = (binder, LetBound (NestedLet live_vars) (manifestArity rhs))
649 live_vars | let_no_escape = addLiveVar bind_lv_info binder
650 | otherwise = unitLiveVar binder
651 -- c.f. the invariant on NestedLet
653 vars_bind :: FreeVarsInfo -- Free var info for body of binding
657 EscVarsSet, -- free vars; escapee vars
658 LiveInfo, -- Vars and CAFs live in binding
659 [(Id, HowBound)]) -- extension to environment
662 vars_bind body_fvs (NonRec binder rhs)
663 = coreToStgRhs body_fvs [] (binder,rhs)
664 `thenLne` \ (rhs2, bind_fvs, bind_lv_info, escs) ->
666 env_ext_item = mk_binding bind_lv_info binder rhs
668 returnLne (StgNonRec binder rhs2,
669 bind_fvs, escs, bind_lv_info, [env_ext_item])
672 vars_bind body_fvs (Rec pairs)
673 = fixLne (\ ~(_, rec_rhs_fvs, _, bind_lv_info, _) ->
675 rec_scope_fvs = unionFVInfo body_fvs rec_rhs_fvs
676 binders = map fst pairs
677 env_ext = [ mk_binding bind_lv_info b rhs
680 extendVarEnvLne env_ext (
681 mapAndUnzip4Lne (coreToStgRhs rec_scope_fvs binders) pairs
682 `thenLne` \ (rhss2, fvss, lv_infos, escss) ->
684 bind_fvs = unionFVInfos fvss
685 bind_lv_info = foldr unionLiveInfo emptyLiveInfo lv_infos
686 escs = unionVarSets escss
688 returnLne (StgRec (binders `zip` rhss2),
689 bind_fvs, escs, bind_lv_info, env_ext)
693 is_join_var :: Id -> Bool
694 -- A hack (used only for compiler debuggging) to tell if
695 -- a variable started life as a join point ($j)
696 is_join_var j = occNameString (getOccName j) == "$j"
700 coreToStgRhs :: FreeVarsInfo -- Free var info for the scope of the binding
703 -> LneM (StgRhs, FreeVarsInfo, LiveInfo, EscVarsSet)
705 coreToStgRhs scope_fv_info binders (bndr, rhs)
706 = coreToStgExpr rhs `thenLne` \ (new_rhs, rhs_fvs, rhs_escs) ->
707 getEnvLne `thenLne` \ env ->
708 freeVarsToLiveVars (binders `minusFVBinders` rhs_fvs) `thenLne` \ lv_info ->
709 returnLne (mkStgRhs rhs_fvs (mkSRT lv_info) bndr_info new_rhs,
710 rhs_fvs, lv_info, rhs_escs)
712 bndr_info = lookupFVInfo scope_fv_info bndr
714 mkStgRhs :: FreeVarsInfo -> SRT -> StgBinderInfo -> StgExpr -> StgRhs
716 mkStgRhs rhs_fvs srt binder_info (StgConApp con args)
717 = StgRhsCon noCCS con args
719 mkStgRhs rhs_fvs srt binder_info (StgLam _ bndrs body)
720 = StgRhsClosure noCCS binder_info
725 mkStgRhs rhs_fvs srt binder_info rhs
726 = StgRhsClosure noCCS binder_info
732 SDM: disabled. Eval/Apply can't handle functions with arity zero very
733 well; and making these into simple non-updatable thunks breaks other
734 assumptions (namely that they will be entered only once).
736 upd_flag | isPAP env rhs = ReEntrant
737 | otherwise = Updatable
741 upd = if isOnceDem dem
742 then (if isNotTop toplev
743 then SingleEntry -- HA! Paydirt for "dem"
746 trace "WARNING: SE CAFs unsupported, forcing UPD instead" $
750 -- For now we forbid SingleEntry CAFs; they tickle the
751 -- ASSERT in rts/Storage.c line 215 at newCAF() re mut_link,
752 -- and I don't understand why. There's only one SE_CAF (well,
753 -- only one that tickled a great gaping bug in an earlier attempt
754 -- at ClosureInfo.getEntryConvention) in the whole of nofib,
755 -- specifically Main.lvl6 in spectral/cryptarithm2.
756 -- So no great loss. KSW 2000-07.
760 Detect thunks which will reduce immediately to PAPs, and make them
761 non-updatable. This has several advantages:
763 - the non-updatable thunk behaves exactly like the PAP,
765 - the thunk is more efficient to enter, because it is
766 specialised to the task.
768 - we save one update frame, one stg_update_PAP, one update
769 and lots of PAP_enters.
771 - in the case where the thunk is top-level, we save building
772 a black hole and futhermore the thunk isn't considered to
773 be a CAF any more, so it doesn't appear in any SRTs.
775 We do it here, because the arity information is accurate, and we need
776 to do it before the SRT pass to save the SRT entries associated with
779 isPAP env (StgApp f args) = listLengthCmp args arity == LT -- idArity f > length args
781 arity = stgArity f (lookupBinding env f)
785 %************************************************************************
787 \subsection[LNE-monad]{A little monad for this let-no-escaping pass}
789 %************************************************************************
791 There's a lot of stuff to pass around, so we use this @LneM@ monad to
792 help. All the stuff here is only passed *down*.
795 type LneM a = IdEnv HowBound
796 -> LiveInfo -- Vars and CAFs live in continuation
799 type LiveInfo = (StgLiveVars, -- Dynamic live variables;
800 -- i.e. ones with a nested (non-top-level) binding
801 CafSet) -- Static live variables;
802 -- i.e. top-level variables that are CAFs or refer to them
804 type EscVarsSet = IdSet
808 = ImportBound -- Used only as a response to lookupBinding; never
809 -- exists in the range of the (IdEnv HowBound)
811 | LetBound -- A let(rec) in this module
812 LetInfo -- Whether top level or nested
813 Arity -- Its arity (local Ids don't have arity info at this point)
815 | LambdaBound -- Used for both lambda and case
818 = TopLet -- top level things
819 | NestedLet LiveInfo -- For nested things, what is live if this
820 -- thing is live? Invariant: the binder
821 -- itself is always a member of
822 -- the dynamic set of its own LiveInfo
824 isLetBound (LetBound _ _) = True
825 isLetBound other = False
827 topLevelBound ImportBound = True
828 topLevelBound (LetBound TopLet _) = True
829 topLevelBound other = False
832 For a let(rec)-bound variable, x, we record LiveInfo, the set of
833 variables that are live if x is live. This LiveInfo comprises
834 (a) dynamic live variables (ones with a non-top-level binding)
835 (b) static live variabes (CAFs or things that refer to CAFs)
837 For "normal" variables (a) is just x alone. If x is a let-no-escaped
838 variable then x is represented by a code pointer and a stack pointer
839 (well, one for each stack). So all of the variables needed in the
840 execution of x are live if x is, and are therefore recorded in the
841 LetBound constructor; x itself *is* included.
843 The set of dynamic live variables is guaranteed ot have no further let-no-escaped
847 emptyLiveInfo :: LiveInfo
848 emptyLiveInfo = (emptyVarSet,emptyVarSet)
850 unitLiveVar :: Id -> LiveInfo
851 unitLiveVar lv = (unitVarSet lv, emptyVarSet)
853 unitLiveCaf :: Id -> LiveInfo
854 unitLiveCaf caf = (emptyVarSet, unitVarSet caf)
856 addLiveVar :: LiveInfo -> Id -> LiveInfo
857 addLiveVar (lvs, cafs) id = (lvs `extendVarSet` id, cafs)
859 unionLiveInfo :: LiveInfo -> LiveInfo -> LiveInfo
860 unionLiveInfo (lv1,caf1) (lv2,caf2) = (lv1 `unionVarSet` lv2, caf1 `unionVarSet` caf2)
862 mkSRT :: LiveInfo -> SRT
863 mkSRT (_, cafs) = SRTEntries cafs
865 getLiveVars :: LiveInfo -> StgLiveVars
866 getLiveVars (lvs, _) = lvs
870 The std monad functions:
872 initLne :: IdEnv HowBound -> LneM a -> a
873 initLne env m = m env emptyLiveInfo
877 {-# INLINE thenLne #-}
878 {-# INLINE returnLne #-}
880 returnLne :: a -> LneM a
881 returnLne e env lvs_cont = e
883 thenLne :: LneM a -> (a -> LneM b) -> LneM b
884 thenLne m k env lvs_cont
885 = k (m env lvs_cont) env lvs_cont
887 mapAndUnzipLne :: (a -> LneM (b,c)) -> [a] -> LneM ([b],[c])
888 mapAndUnzipLne f [] = returnLne ([],[])
889 mapAndUnzipLne f (x:xs)
890 = f x `thenLne` \ (r1, r2) ->
891 mapAndUnzipLne f xs `thenLne` \ (rs1, rs2) ->
892 returnLne (r1:rs1, r2:rs2)
894 mapAndUnzip3Lne :: (a -> LneM (b,c,d)) -> [a] -> LneM ([b],[c],[d])
895 mapAndUnzip3Lne f [] = returnLne ([],[],[])
896 mapAndUnzip3Lne f (x:xs)
897 = f x `thenLne` \ (r1, r2, r3) ->
898 mapAndUnzip3Lne f xs `thenLne` \ (rs1, rs2, rs3) ->
899 returnLne (r1:rs1, r2:rs2, r3:rs3)
901 mapAndUnzip4Lne :: (a -> LneM (b,c,d,e)) -> [a] -> LneM ([b],[c],[d],[e])
902 mapAndUnzip4Lne f [] = returnLne ([],[],[],[])
903 mapAndUnzip4Lne f (x:xs)
904 = f x `thenLne` \ (r1, r2, r3, r4) ->
905 mapAndUnzip4Lne f xs `thenLne` \ (rs1, rs2, rs3, rs4) ->
906 returnLne (r1:rs1, r2:rs2, r3:rs3, r4:rs4)
908 fixLne :: (a -> LneM a) -> LneM a
909 fixLne expr env lvs_cont
912 result = expr result env lvs_cont
915 Functions specific to this monad:
918 getVarsLiveInCont :: LneM LiveInfo
919 getVarsLiveInCont env lvs_cont = lvs_cont
921 setVarsLiveInCont :: LiveInfo -> LneM a -> LneM a
922 setVarsLiveInCont new_lvs_cont expr env lvs_cont
923 = expr env new_lvs_cont
925 extendVarEnvLne :: [(Id, HowBound)] -> LneM a -> LneM a
926 extendVarEnvLne ids_w_howbound expr env lvs_cont
927 = expr (extendVarEnvList env ids_w_howbound) lvs_cont
929 lookupVarLne :: Id -> LneM HowBound
930 lookupVarLne v env lvs_cont = returnLne (lookupBinding env v) env lvs_cont
932 getEnvLne :: LneM (IdEnv HowBound)
933 getEnvLne env lvs_cont = returnLne env env lvs_cont
935 lookupBinding :: IdEnv HowBound -> Id -> HowBound
936 lookupBinding env v = case lookupVarEnv env v of
938 Nothing -> ASSERT2( isGlobalId v, ppr v ) ImportBound
941 -- The result of lookupLiveVarsForSet, a set of live variables, is
942 -- only ever tacked onto a decorated expression. It is never used as
943 -- the basis of a control decision, which might give a black hole.
945 freeVarsToLiveVars :: FreeVarsInfo -> LneM LiveInfo
946 freeVarsToLiveVars fvs env live_in_cont
947 = returnLne live_info env live_in_cont
949 live_info = foldr unionLiveInfo live_in_cont lvs_from_fvs
950 lvs_from_fvs = map do_one (allFreeIds fvs)
952 do_one (v, how_bound)
954 ImportBound -> unitLiveCaf v -- Only CAF imports are
957 | mayHaveCafRefs (idCafInfo v) -> unitLiveCaf v
958 | otherwise -> emptyLiveInfo
960 LetBound (NestedLet lvs) _ -> lvs -- lvs already contains v
961 -- (see the invariant on NestedLet)
963 _lambda_or_case_binding -> unitLiveVar v -- Bound by lambda or case
966 %************************************************************************
968 \subsection[Free-var info]{Free variable information}
970 %************************************************************************
973 type FreeVarsInfo = VarEnv (Var, HowBound, StgBinderInfo)
974 -- The Var is so we can gather up the free variables
977 -- The HowBound info just saves repeated lookups;
978 -- we look up just once when we encounter the occurrence.
979 -- INVARIANT: Any ImportBound Ids are HaveCafRef Ids
980 -- Imported Ids without CAF refs are simply
981 -- not put in the FreeVarsInfo for an expression.
982 -- See singletonFVInfo and freeVarsToLiveVars
984 -- StgBinderInfo records how it occurs; notably, we
985 -- are interested in whether it only occurs in saturated
986 -- applications, because then we don't need to build a
988 -- If f is mapped to noBinderInfo, that means
989 -- that f *is* mentioned (else it wouldn't be in the
990 -- IdEnv at all), but perhaps in an unsaturated applications.
992 -- All case/lambda-bound things are also mapped to
993 -- noBinderInfo, since we aren't interested in their
996 -- For ILX we track free var info for type variables too;
997 -- hence VarEnv not IdEnv
1001 emptyFVInfo :: FreeVarsInfo
1002 emptyFVInfo = emptyVarEnv
1004 singletonFVInfo :: Id -> HowBound -> StgBinderInfo -> FreeVarsInfo
1005 -- Don't record non-CAF imports at all, to keep free-var sets small
1006 singletonFVInfo id ImportBound info
1007 | mayHaveCafRefs (idCafInfo id) = unitVarEnv id (id, ImportBound, info)
1008 | otherwise = emptyVarEnv
1009 singletonFVInfo id how_bound info = unitVarEnv id (id, how_bound, info)
1011 tyvarFVInfo :: TyVarSet -> FreeVarsInfo
1012 tyvarFVInfo tvs = foldVarSet add emptyFVInfo tvs
1014 add tv fvs = extendVarEnv fvs tv (tv, LambdaBound, noBinderInfo)
1015 -- Type variables must be lambda-bound
1017 unionFVInfo :: FreeVarsInfo -> FreeVarsInfo -> FreeVarsInfo
1018 unionFVInfo fv1 fv2 = plusVarEnv_C plusFVInfo fv1 fv2
1020 unionFVInfos :: [FreeVarsInfo] -> FreeVarsInfo
1021 unionFVInfos fvs = foldr unionFVInfo emptyFVInfo fvs
1023 minusFVBinders :: [Id] -> FreeVarsInfo -> FreeVarsInfo
1024 minusFVBinders vs fv = foldr minusFVBinder fv vs
1026 minusFVBinder :: Id -> FreeVarsInfo -> FreeVarsInfo
1027 minusFVBinder v fv | isId v && opt_RuntimeTypes
1028 = (fv `delVarEnv` v) `unionFVInfo`
1029 tyvarFVInfo (tyVarsOfType (idType v))
1030 | otherwise = fv `delVarEnv` v
1031 -- When removing a binder, remember to add its type variables
1032 -- c.f. CoreFVs.delBinderFV
1034 elementOfFVInfo :: Id -> FreeVarsInfo -> Bool
1035 elementOfFVInfo id fvs = maybeToBool (lookupVarEnv fvs id)
1037 lookupFVInfo :: FreeVarsInfo -> Id -> StgBinderInfo
1038 -- Find how the given Id is used.
1039 -- Externally visible things may be used any old how
1041 | isExternalName (idName id) = noBinderInfo
1042 | otherwise = case lookupVarEnv fvs id of
1043 Nothing -> noBinderInfo
1044 Just (_,_,info) -> info
1046 allFreeIds :: FreeVarsInfo -> [(Id,HowBound)] -- Both top level and non-top-level Ids
1047 allFreeIds fvs = [(id,how_bound) | (id,how_bound,_) <- varEnvElts fvs, isId id]
1049 -- Non-top-level things only, both type variables and ids
1050 -- (type variables only if opt_RuntimeTypes)
1051 getFVs :: FreeVarsInfo -> [Var]
1052 getFVs fvs = [id | (id, how_bound, _) <- varEnvElts fvs,
1053 not (topLevelBound how_bound) ]
1055 getFVSet :: FreeVarsInfo -> VarSet
1056 getFVSet fvs = mkVarSet (getFVs fvs)
1058 plusFVInfo (id1,hb1,info1) (id2,hb2,info2)
1059 = ASSERT (id1 == id2 && hb1 `check_eq_how_bound` hb2)
1060 (id1, hb1, combineStgBinderInfo info1 info2)
1063 -- The HowBound info for a variable in the FVInfo should be consistent
1064 check_eq_how_bound ImportBound ImportBound = True
1065 check_eq_how_bound LambdaBound LambdaBound = True
1066 check_eq_how_bound (LetBound li1 ar1) (LetBound li2 ar2) = ar1 == ar2 && check_eq_li li1 li2
1067 check_eq_how_bound hb1 hb2 = False
1069 check_eq_li (NestedLet _) (NestedLet _) = True
1070 check_eq_li TopLet TopLet = True
1071 check_eq_li li1 li2 = False
1077 filterStgBinders :: [Var] -> [Var]
1078 filterStgBinders bndrs
1079 | opt_RuntimeTypes = bndrs
1080 | otherwise = filter isId bndrs
1085 -- Ignore all notes except SCC
1086 myCollectBinders expr
1089 go bs (Lam b e) = go (b:bs) e
1090 go bs e@(Note (SCC _) _) = (reverse bs, e)
1091 go bs (Cast e co) = go bs e
1092 go bs (Note _ e) = go bs e
1093 go bs e = (reverse bs, e)
1095 myCollectArgs :: CoreExpr -> (Id, [CoreArg])
1096 -- We assume that we only have variables
1097 -- in the function position by now
1101 go (Var v) as = (v, as)
1102 go (App f a) as = go f (a:as)
1103 go (Note (SCC _) e) as = pprPanic "CoreToStg.myCollectArgs" (ppr expr)
1104 go (Cast e co) as = go e as
1105 go (Note n e) as = go e as
1106 go _ as = pprPanic "CoreToStg.myCollectArgs" (ppr expr)
1110 stgArity :: Id -> HowBound -> Arity
1111 stgArity f (LetBound _ arity) = arity
1112 stgArity f ImportBound = idArity f
1113 stgArity f LambdaBound = 0