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
11 -- The above warning supression flag is a temporary kludge.
12 -- While working on this module you are encouraged to remove it and fix
13 -- any warnings in the module. See
14 -- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
17 module CoreToStg ( coreToStg, coreExprToStg ) where
19 #include "HsVersions.h"
22 import CoreUtils ( rhsIsStatic, manifestArity, exprType, findDefault )
28 import Var ( Var, globalIdDetails, idType )
31 import CostCentre ( noCCS )
34 import Maybes ( maybeToBool )
35 import Name ( getOccName, isExternalName, nameOccName )
36 import OccName ( occNameString, occNameFS )
37 import BasicTypes ( Arity )
38 import StaticFlags ( opt_RuntimeTypes )
45 %************************************************************************
47 \subsection[live-vs-free-doc]{Documentation}
49 %************************************************************************
51 (There is other relevant documentation in codeGen/CgLetNoEscape.)
53 The actual Stg datatype is decorated with {\em live variable}
54 information, as well as {\em free variable} information. The two are
55 {\em not} the same. Liveness is an operational property rather than a
56 semantic one. A variable is live at a particular execution point if
57 it can be referred to {\em directly} again. In particular, a dead
58 variable's stack slot (if it has one):
61 should be stubbed to avoid space leaks, and
63 may be reused for something else.
66 There ought to be a better way to say this. Here are some examples:
73 Just after the `in', v is live, but q is dead. If the whole of that
74 let expression was enclosed in a case expression, thus:
76 case (let v = [q] \[x] -> e in ...v...) of
79 (ie @alts@ mention @q@), then @q@ is live even after the `in'; because
80 we'll return later to the @alts@ and need it.
82 Let-no-escapes make this a bit more interesting:
84 let-no-escape v = [q] \ [x] -> e
88 Here, @q@ is still live at the `in', because @v@ is represented not by
89 a closure but by the current stack state. In other words, if @v@ is
90 live then so is @q@. Furthermore, if @e@ mentions an enclosing
91 let-no-escaped variable, then {\em its} free variables are also live
94 %************************************************************************
96 \subsection[caf-info]{Collecting live CAF info}
98 %************************************************************************
100 In this pass we also collect information on which CAFs are live for
101 constructing SRTs (see SRT.lhs).
103 A top-level Id has CafInfo, which is
105 - MayHaveCafRefs, if it may refer indirectly to
107 - NoCafRefs if it definitely doesn't
109 The CafInfo has already been calculated during the CoreTidy pass.
111 During CoreToStg, we then pin onto each binding and case expression, a
112 list of Ids which represents the "live" CAFs at that point. The meaning
113 of "live" here is the same as for live variables, see above (which is
114 why it's convenient to collect CAF information here rather than elsewhere).
116 The later SRT pass takes these lists of Ids and uses them to construct
117 the actual nested SRTs, and replaces the lists of Ids with (offset,length)
121 Interaction of let-no-escape with SRTs [Sept 01]
122 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
125 let-no-escape x = ...caf1...caf2...
129 where caf1,caf2 are CAFs. Since x doesn't have a closure, we
130 build SRTs just as if x's defn was inlined at each call site, and
131 that means that x's CAF refs get duplicated in the overall SRT.
133 This is unlike ordinary lets, in which the CAF refs are not duplicated.
135 We could fix this loss of (static) sharing by making a sort of pseudo-closure
136 for x, solely to put in the SRTs lower down.
139 %************************************************************************
141 \subsection[binds-StgVarInfo]{Setting variable info: top-level, binds, RHSs}
143 %************************************************************************
146 coreToStg :: PackageId -> [CoreBind] -> IO [StgBinding]
147 coreToStg this_pkg pgm
149 where (_, _, pgm') = coreTopBindsToStg this_pkg emptyVarEnv pgm
151 coreExprToStg :: CoreExpr -> StgExpr
153 = new_expr where (new_expr,_,_) = initLne emptyVarEnv (coreToStgExpr expr)
158 -> IdEnv HowBound -- environment for the bindings
160 -> (IdEnv HowBound, FreeVarsInfo, [StgBinding])
162 coreTopBindsToStg this_pkg env [] = (env, emptyFVInfo, [])
163 coreTopBindsToStg this_pkg env (b:bs)
164 = (env2, fvs2, b':bs')
166 -- env accumulates down the list of binds, fvs accumulates upwards
167 (env1, fvs2, b' ) = coreTopBindToStg this_pkg env fvs1 b
168 (env2, fvs1, bs') = coreTopBindsToStg this_pkg env1 bs
174 -> FreeVarsInfo -- Info about the body
176 -> (IdEnv HowBound, FreeVarsInfo, StgBinding)
178 coreTopBindToStg this_pkg env body_fvs (NonRec id rhs)
180 env' = extendVarEnv env id how_bound
181 how_bound = LetBound TopLet $! manifestArity rhs
185 coreToTopStgRhs this_pkg body_fvs (id,rhs) `thenLne` \ (stg_rhs, fvs') ->
186 returnLne (stg_rhs, fvs')
189 bind = StgNonRec id stg_rhs
191 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) )
192 ASSERT2(consistentCafInfo id bind, ppr id)
193 -- WARN(not (consistent caf_info bind), ppr id <+> ppr cafs <+> ppCafInfo caf_info)
194 (env', fvs' `unionFVInfo` body_fvs, bind)
196 coreTopBindToStg this_pkg env body_fvs (Rec pairs)
198 (binders, rhss) = unzip pairs
200 extra_env' = [ (b, LetBound TopLet $! manifestArity rhs)
201 | (b, rhs) <- pairs ]
202 env' = extendVarEnvList env extra_env'
206 mapAndUnzipLne (coreToTopStgRhs this_pkg body_fvs) pairs
207 `thenLne` \ (stg_rhss, fvss') ->
208 let fvs' = unionFVInfos fvss' in
209 returnLne (stg_rhss, fvs')
212 bind = StgRec (zip binders stg_rhss)
214 ASSERT2(and [manifestArity rhs == stgRhsArity stg_rhs | (rhs,stg_rhs) <- rhss `zip` stg_rhss], ppr binders)
215 ASSERT2(consistentCafInfo (head binders) bind, ppr binders)
216 (env', fvs' `unionFVInfo` body_fvs, bind)
218 -- Assertion helper: this checks that the CafInfo on the Id matches
219 -- what CoreToStg has figured out about the binding's SRT. The
220 -- CafInfo will be exact in all cases except when CorePrep has
221 -- floated out a binding, in which case it will be approximate.
222 consistentCafInfo id bind
223 | occNameFS (nameOccName (idName id)) == FSLIT("sat")
226 = WARN (not exact, ppr id) safe
228 safe = id_marked_caffy || not binding_is_caffy
229 exact = id_marked_caffy == binding_is_caffy
230 id_marked_caffy = mayHaveCafRefs (idCafInfo id)
231 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) )
324 coreToStgExpr (Case (Var id) _bndr ty [(DEFAULT,[],expr)])
325 | Just (TickBox m n) <- isTickBoxOp_maybe id
326 = coreToStgExpr expr `thenLne` ( \ (expr2, fvs, escs) ->
327 returnLne (StgTick m n expr2, fvs, escs) )
329 coreToStgExpr (Note other_note expr)
332 coreToStgExpr (Cast expr co)
335 -- Cases require a little more real work.
337 coreToStgExpr (Case scrut bndr _ alts)
338 = extendVarEnvLne [(bndr, LambdaBound)] (
339 mapAndUnzip3Lne vars_alt alts `thenLne` \ (alts2, fvs_s, escs_s) ->
342 unionVarSets escs_s )
343 ) `thenLne` \ (alts2, alts_fvs, alts_escs) ->
345 -- Determine whether the default binder is dead or not
346 -- This helps the code generator to avoid generating an assignment
347 -- for the case binder (is extremely rare cases) ToDo: remove.
348 bndr' | bndr `elementOfFVInfo` alts_fvs = bndr
349 | otherwise = bndr `setIdOccInfo` IAmDead
351 -- Don't consider the default binder as being 'live in alts',
352 -- since this is from the point of view of the case expr, where
353 -- the default binder is not free.
354 alts_fvs_wo_bndr = bndr `minusFVBinder` alts_fvs
355 alts_escs_wo_bndr = alts_escs `delVarSet` bndr
358 freeVarsToLiveVars alts_fvs_wo_bndr `thenLne` \ alts_lv_info ->
360 -- We tell the scrutinee that everything
361 -- live in the alts is live in it, too.
362 setVarsLiveInCont alts_lv_info (
363 coreToStgExpr scrut `thenLne` \ (scrut2, scrut_fvs, scrut_escs) ->
364 freeVarsToLiveVars scrut_fvs `thenLne` \ scrut_lv_info ->
365 returnLne (scrut2, scrut_fvs, scrut_escs, scrut_lv_info)
367 `thenLne` \ (scrut2, scrut_fvs, scrut_escs, scrut_lv_info) ->
370 StgCase scrut2 (getLiveVars scrut_lv_info)
371 (getLiveVars alts_lv_info)
374 (mkStgAltType (idType bndr) alts)
376 scrut_fvs `unionFVInfo` alts_fvs_wo_bndr,
377 alts_escs_wo_bndr `unionVarSet` getFVSet scrut_fvs
378 -- You might think we should have scrut_escs, not
379 -- (getFVSet scrut_fvs), but actually we can't call, and
380 -- then return from, a let-no-escape thing.
383 vars_alt (con, binders, rhs)
384 = let -- Remove type variables
385 binders' = filterStgBinders binders
387 extendVarEnvLne [(b, LambdaBound) | b <- binders'] $
388 coreToStgExpr rhs `thenLne` \ (rhs2, rhs_fvs, rhs_escs) ->
390 -- Records whether each param is used in the RHS
391 good_use_mask = [ b `elementOfFVInfo` rhs_fvs | b <- binders' ]
393 returnLne ( (con, binders', good_use_mask, rhs2),
394 binders' `minusFVBinders` rhs_fvs,
395 rhs_escs `delVarSetList` binders' )
396 -- ToDo: remove the delVarSet;
397 -- since escs won't include any of these binders
400 Lets not only take quite a bit of work, but this is where we convert
401 then to let-no-escapes, if we wish.
403 (Meanwhile, we don't expect to see let-no-escapes...)
405 coreToStgExpr (Let bind body)
406 = fixLne (\ ~(_, _, _, no_binder_escapes) ->
407 coreToStgLet no_binder_escapes bind body
408 ) `thenLne` \ (new_let, fvs, escs, _) ->
410 returnLne (new_let, fvs, escs)
414 mkStgAltType scrut_ty alts
415 = case splitTyConApp_maybe (repType scrut_ty) of
416 Just (tc,_) | isUnboxedTupleTyCon tc -> UbxTupAlt tc
417 | isUnLiftedTyCon tc -> PrimAlt tc
418 | isHiBootTyCon tc -> look_for_better_tycon
419 | isAlgTyCon tc -> AlgAlt tc
420 | isFunTyCon tc -> PolyAlt
421 | isPrimTyCon tc -> PolyAlt -- for "Any"
422 | otherwise -> pprPanic "mkStgAlts" (ppr tc)
426 -- Sometimes, the TyCon in the type of the scrutinee is an HiBootTyCon,
427 -- which may not have any constructors inside it. If so, then we
428 -- can get a better TyCon by grabbing the one from a constructor alternative
430 look_for_better_tycon
431 | ((DataAlt con, _, _) : _) <- data_alts =
432 AlgAlt (dataConTyCon con)
434 ASSERT(null data_alts)
437 (data_alts, _deflt) = findDefault alts
441 -- ---------------------------------------------------------------------------
443 -- ---------------------------------------------------------------------------
447 :: Maybe UpdateFlag -- Just upd <=> this application is
448 -- the rhs of a thunk binding
449 -- x = [...] \upd [] -> the_app
450 -- with specified update flag
452 -> [CoreArg] -- Arguments
453 -> LneM (StgExpr, FreeVarsInfo, EscVarsSet)
456 coreToStgApp maybe_thunk_body f args
457 = coreToStgArgs args `thenLne` \ (args', args_fvs) ->
458 lookupVarLne f `thenLne` \ how_bound ->
461 n_val_args = valArgCount args
462 not_letrec_bound = not (isLetBound how_bound)
464 = let fvs = singletonFVInfo f how_bound fun_occ in
465 -- e.g. (f :: a -> int) (x :: a)
466 -- Here the free variables are "f", "x" AND the type variable "a"
467 -- coreToStgArgs will deal with the arguments recursively
468 if opt_RuntimeTypes then
469 fvs `unionFVInfo` tyvarFVInfo (tyVarsOfType (idType f))
472 -- Mostly, the arity info of a function is in the fn's IdInfo
473 -- But new bindings introduced by CoreSat may not have no
474 -- arity info; it would do us no good anyway. For example:
475 -- let f = \ab -> e in f
476 -- No point in having correct arity info for f!
477 -- Hence the hasArity stuff below.
478 -- NB: f_arity is only consulted for LetBound things
479 f_arity = stgArity f how_bound
480 saturated = f_arity <= n_val_args
483 | not_letrec_bound = noBinderInfo -- Uninteresting variable
484 | f_arity > 0 && saturated = stgSatOcc -- Saturated or over-saturated function call
485 | otherwise = stgUnsatOcc -- Unsaturated function or thunk
488 | not_letrec_bound = emptyVarSet -- Only letrec-bound escapees are interesting
489 | f_arity == n_val_args = emptyVarSet -- A function *or thunk* with an exactly
490 -- saturated call doesn't escape
491 -- (let-no-escape applies to 'thunks' too)
493 | otherwise = unitVarSet f -- Inexact application; it does escape
495 -- At the moment of the call:
497 -- either the function is *not* let-no-escaped, in which case
498 -- nothing is live except live_in_cont
499 -- or the function *is* let-no-escaped in which case the
500 -- variables it uses are live, but still the function
501 -- itself is not. PS. In this case, the function's
502 -- live vars should already include those of the
503 -- continuation, but it does no harm to just union the
506 res_ty = exprType (mkApps (Var f) args)
507 app = case globalIdDetails f of
508 DataConWorkId dc | saturated -> StgConApp dc args'
509 PrimOpId op -> ASSERT( saturated )
510 StgOpApp (StgPrimOp op) args' res_ty
511 FCallId call -> ASSERT( saturated )
512 StgOpApp (StgFCallOp call (idUnique f)) args' res_ty
513 TickBoxOpId {} -> pprPanic "coreToStg TickBox" $ ppr (f,args')
514 _other -> StgApp f args'
519 fun_fvs `unionFVInfo` args_fvs,
520 fun_escs `unionVarSet` (getFVSet args_fvs)
521 -- All the free vars of the args are disqualified
522 -- from being let-no-escaped.
527 -- ---------------------------------------------------------------------------
529 -- This is the guy that turns applications into A-normal form
530 -- ---------------------------------------------------------------------------
532 coreToStgArgs :: [CoreArg] -> LneM ([StgArg], FreeVarsInfo)
534 = returnLne ([], emptyFVInfo)
536 coreToStgArgs (Type ty : args) -- Type argument
537 = coreToStgArgs args `thenLne` \ (args', fvs) ->
538 if opt_RuntimeTypes then
539 returnLne (StgTypeArg ty : args', fvs `unionFVInfo` tyvarFVInfo (tyVarsOfType ty))
541 returnLne (args', fvs)
543 coreToStgArgs (arg : args) -- Non-type argument
544 = coreToStgArgs args `thenLne` \ (stg_args, args_fvs) ->
545 coreToStgExpr arg `thenLne` \ (arg', arg_fvs, escs) ->
547 fvs = args_fvs `unionFVInfo` arg_fvs
548 stg_arg = case arg' of
549 StgApp v [] -> StgVarArg v
550 StgConApp con [] -> StgVarArg (dataConWorkId con)
551 StgLit lit -> StgLitArg lit
552 _ -> pprPanic "coreToStgArgs" (ppr arg)
554 -- WARNING: what if we have an argument like (v `cast` co)
555 -- where 'co' changes the representation type?
556 -- (This really only happens if co is unsafe.)
557 -- Then all the getArgAmode stuff in CgBindery will set the
558 -- cg_rep of the CgIdInfo based on the type of v, rather
559 -- than the type of 'co'.
560 -- This matters particularly when the function is a primop
562 -- Wanted: a better solution than this hacky warning
564 arg_ty = exprType arg
565 stg_arg_ty = stgArgType stg_arg
566 bad_args = (isUnLiftedType arg_ty && not (isUnLiftedType stg_arg_ty))
567 || (typePrimRep arg_ty /= typePrimRep stg_arg_ty)
568 -- In GHCi we coerce an argument of type BCO# (unlifted) to HValue (lifted),
569 -- and pass it to a function expecting an HValue (arg_ty). This is ok because
570 -- we can treat an unlifted value as lifted. But the other way round
572 -- We also want to check if a pointer is cast to a non-ptr etc
574 WARN( bad_args, ptext SLIT("Dangerous-looking argument. Probable cause: bad unsafeCoerce#") $$ ppr arg )
575 returnLne (stg_arg : stg_args, fvs)
578 -- ---------------------------------------------------------------------------
579 -- The magic for lets:
580 -- ---------------------------------------------------------------------------
583 :: Bool -- True <=> yes, we are let-no-escaping this let
584 -> CoreBind -- bindings
586 -> LneM (StgExpr, -- new let
587 FreeVarsInfo, -- variables free in the whole let
588 EscVarsSet, -- variables that escape from the whole let
589 Bool) -- True <=> none of the binders in the bindings
590 -- is among the escaping vars
592 coreToStgLet let_no_escape bind body
593 = fixLne (\ ~(_, _, _, _, _, rec_body_fvs, _, _) ->
595 -- Do the bindings, setting live_in_cont to empty if
596 -- we ain't in a let-no-escape world
597 getVarsLiveInCont `thenLne` \ live_in_cont ->
598 setVarsLiveInCont (if let_no_escape
601 (vars_bind rec_body_fvs bind)
602 `thenLne` \ ( bind2, bind_fvs, bind_escs, bind_lv_info, env_ext) ->
605 extendVarEnvLne env_ext (
606 coreToStgExpr body `thenLne` \(body2, body_fvs, body_escs) ->
607 freeVarsToLiveVars body_fvs `thenLne` \ body_lv_info ->
609 returnLne (bind2, bind_fvs, bind_escs, getLiveVars bind_lv_info,
610 body2, body_fvs, body_escs, getLiveVars body_lv_info)
613 ) `thenLne` (\ (bind2, bind_fvs, bind_escs, bind_lvs,
614 body2, body_fvs, body_escs, body_lvs) ->
617 -- Compute the new let-expression
619 new_let | let_no_escape = StgLetNoEscape live_in_whole_let bind_lvs bind2 body2
620 | otherwise = StgLet bind2 body2
623 = binders `minusFVBinders` (bind_fvs `unionFVInfo` body_fvs)
626 = bind_lvs `unionVarSet` (body_lvs `delVarSetList` binders)
628 real_bind_escs = if let_no_escape then
632 -- Everything escapes which is free in the bindings
634 let_escs = (real_bind_escs `unionVarSet` body_escs) `delVarSetList` binders
636 all_escs = bind_escs `unionVarSet` body_escs -- Still includes binders of
639 no_binder_escapes = isEmptyVarSet (set_of_binders `intersectVarSet` all_escs)
642 -- Debugging code as requested by Andrew Kennedy
643 checked_no_binder_escapes
644 | not no_binder_escapes && any is_join_var binders
645 = pprTrace "Interesting! A join var that isn't let-no-escaped" (ppr binders)
647 | otherwise = no_binder_escapes
649 checked_no_binder_escapes = no_binder_escapes
652 -- Mustn't depend on the passed-in let_no_escape flag, since
653 -- no_binder_escapes is used by the caller to derive the flag!
659 checked_no_binder_escapes
662 set_of_binders = mkVarSet binders
663 binders = bindersOf bind
665 mk_binding bind_lv_info binder rhs
666 = (binder, LetBound (NestedLet live_vars) (manifestArity rhs))
668 live_vars | let_no_escape = addLiveVar bind_lv_info binder
669 | otherwise = unitLiveVar binder
670 -- c.f. the invariant on NestedLet
672 vars_bind :: FreeVarsInfo -- Free var info for body of binding
676 EscVarsSet, -- free vars; escapee vars
677 LiveInfo, -- Vars and CAFs live in binding
678 [(Id, HowBound)]) -- extension to environment
681 vars_bind body_fvs (NonRec binder rhs)
682 = coreToStgRhs body_fvs [] (binder,rhs)
683 `thenLne` \ (rhs2, bind_fvs, bind_lv_info, escs) ->
685 env_ext_item = mk_binding bind_lv_info binder rhs
687 returnLne (StgNonRec binder rhs2,
688 bind_fvs, escs, bind_lv_info, [env_ext_item])
691 vars_bind body_fvs (Rec pairs)
692 = fixLne (\ ~(_, rec_rhs_fvs, _, bind_lv_info, _) ->
694 rec_scope_fvs = unionFVInfo body_fvs rec_rhs_fvs
695 binders = map fst pairs
696 env_ext = [ mk_binding bind_lv_info b rhs
699 extendVarEnvLne env_ext (
700 mapAndUnzip4Lne (coreToStgRhs rec_scope_fvs binders) pairs
701 `thenLne` \ (rhss2, fvss, lv_infos, escss) ->
703 bind_fvs = unionFVInfos fvss
704 bind_lv_info = foldr unionLiveInfo emptyLiveInfo lv_infos
705 escs = unionVarSets escss
707 returnLne (StgRec (binders `zip` rhss2),
708 bind_fvs, escs, bind_lv_info, env_ext)
712 is_join_var :: Id -> Bool
713 -- A hack (used only for compiler debuggging) to tell if
714 -- a variable started life as a join point ($j)
715 is_join_var j = occNameString (getOccName j) == "$j"
719 coreToStgRhs :: FreeVarsInfo -- Free var info for the scope of the binding
722 -> LneM (StgRhs, FreeVarsInfo, LiveInfo, EscVarsSet)
724 coreToStgRhs scope_fv_info binders (bndr, rhs)
725 = coreToStgExpr rhs `thenLne` \ (new_rhs, rhs_fvs, rhs_escs) ->
726 getEnvLne `thenLne` \ env ->
727 freeVarsToLiveVars (binders `minusFVBinders` rhs_fvs) `thenLne` \ lv_info ->
728 returnLne (mkStgRhs rhs_fvs (mkSRT lv_info) bndr_info new_rhs,
729 rhs_fvs, lv_info, rhs_escs)
731 bndr_info = lookupFVInfo scope_fv_info bndr
733 mkStgRhs :: FreeVarsInfo -> SRT -> StgBinderInfo -> StgExpr -> StgRhs
735 mkStgRhs rhs_fvs srt binder_info (StgConApp con args)
736 = StgRhsCon noCCS con args
738 mkStgRhs rhs_fvs srt binder_info (StgLam _ bndrs body)
739 = StgRhsClosure noCCS binder_info
744 mkStgRhs rhs_fvs srt binder_info rhs
745 = StgRhsClosure noCCS binder_info
751 SDM: disabled. Eval/Apply can't handle functions with arity zero very
752 well; and making these into simple non-updatable thunks breaks other
753 assumptions (namely that they will be entered only once).
755 upd_flag | isPAP env rhs = ReEntrant
756 | otherwise = Updatable
760 upd = if isOnceDem dem
761 then (if isNotTop toplev
762 then SingleEntry -- HA! Paydirt for "dem"
765 trace "WARNING: SE CAFs unsupported, forcing UPD instead" $
769 -- For now we forbid SingleEntry CAFs; they tickle the
770 -- ASSERT in rts/Storage.c line 215 at newCAF() re mut_link,
771 -- and I don't understand why. There's only one SE_CAF (well,
772 -- only one that tickled a great gaping bug in an earlier attempt
773 -- at ClosureInfo.getEntryConvention) in the whole of nofib,
774 -- specifically Main.lvl6 in spectral/cryptarithm2.
775 -- So no great loss. KSW 2000-07.
779 Detect thunks which will reduce immediately to PAPs, and make them
780 non-updatable. This has several advantages:
782 - the non-updatable thunk behaves exactly like the PAP,
784 - the thunk is more efficient to enter, because it is
785 specialised to the task.
787 - we save one update frame, one stg_update_PAP, one update
788 and lots of PAP_enters.
790 - in the case where the thunk is top-level, we save building
791 a black hole and futhermore the thunk isn't considered to
792 be a CAF any more, so it doesn't appear in any SRTs.
794 We do it here, because the arity information is accurate, and we need
795 to do it before the SRT pass to save the SRT entries associated with
798 isPAP env (StgApp f args) = listLengthCmp args arity == LT -- idArity f > length args
800 arity = stgArity f (lookupBinding env f)
804 %************************************************************************
806 \subsection[LNE-monad]{A little monad for this let-no-escaping pass}
808 %************************************************************************
810 There's a lot of stuff to pass around, so we use this @LneM@ monad to
811 help. All the stuff here is only passed *down*.
814 type LneM a = IdEnv HowBound
815 -> LiveInfo -- Vars and CAFs live in continuation
818 type LiveInfo = (StgLiveVars, -- Dynamic live variables;
819 -- i.e. ones with a nested (non-top-level) binding
820 CafSet) -- Static live variables;
821 -- i.e. top-level variables that are CAFs or refer to them
823 type EscVarsSet = IdSet
827 = ImportBound -- Used only as a response to lookupBinding; never
828 -- exists in the range of the (IdEnv HowBound)
830 | LetBound -- A let(rec) in this module
831 LetInfo -- Whether top level or nested
832 Arity -- Its arity (local Ids don't have arity info at this point)
834 | LambdaBound -- Used for both lambda and case
837 = TopLet -- top level things
838 | NestedLet LiveInfo -- For nested things, what is live if this
839 -- thing is live? Invariant: the binder
840 -- itself is always a member of
841 -- the dynamic set of its own LiveInfo
843 isLetBound (LetBound _ _) = True
844 isLetBound other = False
846 topLevelBound ImportBound = True
847 topLevelBound (LetBound TopLet _) = True
848 topLevelBound other = False
851 For a let(rec)-bound variable, x, we record LiveInfo, the set of
852 variables that are live if x is live. This LiveInfo comprises
853 (a) dynamic live variables (ones with a non-top-level binding)
854 (b) static live variabes (CAFs or things that refer to CAFs)
856 For "normal" variables (a) is just x alone. If x is a let-no-escaped
857 variable then x is represented by a code pointer and a stack pointer
858 (well, one for each stack). So all of the variables needed in the
859 execution of x are live if x is, and are therefore recorded in the
860 LetBound constructor; x itself *is* included.
862 The set of dynamic live variables is guaranteed ot have no further let-no-escaped
866 emptyLiveInfo :: LiveInfo
867 emptyLiveInfo = (emptyVarSet,emptyVarSet)
869 unitLiveVar :: Id -> LiveInfo
870 unitLiveVar lv = (unitVarSet lv, emptyVarSet)
872 unitLiveCaf :: Id -> LiveInfo
873 unitLiveCaf caf = (emptyVarSet, unitVarSet caf)
875 addLiveVar :: LiveInfo -> Id -> LiveInfo
876 addLiveVar (lvs, cafs) id = (lvs `extendVarSet` id, cafs)
878 unionLiveInfo :: LiveInfo -> LiveInfo -> LiveInfo
879 unionLiveInfo (lv1,caf1) (lv2,caf2) = (lv1 `unionVarSet` lv2, caf1 `unionVarSet` caf2)
881 mkSRT :: LiveInfo -> SRT
882 mkSRT (_, cafs) = SRTEntries cafs
884 getLiveVars :: LiveInfo -> StgLiveVars
885 getLiveVars (lvs, _) = lvs
889 The std monad functions:
891 initLne :: IdEnv HowBound -> LneM a -> a
892 initLne env m = m env emptyLiveInfo
896 {-# INLINE thenLne #-}
897 {-# INLINE returnLne #-}
899 returnLne :: a -> LneM a
900 returnLne e env lvs_cont = e
902 thenLne :: LneM a -> (a -> LneM b) -> LneM b
903 thenLne m k env lvs_cont
904 = k (m env lvs_cont) env lvs_cont
906 mapAndUnzipLne :: (a -> LneM (b,c)) -> [a] -> LneM ([b],[c])
907 mapAndUnzipLne f [] = returnLne ([],[])
908 mapAndUnzipLne f (x:xs)
909 = f x `thenLne` \ (r1, r2) ->
910 mapAndUnzipLne f xs `thenLne` \ (rs1, rs2) ->
911 returnLne (r1:rs1, r2:rs2)
913 mapAndUnzip3Lne :: (a -> LneM (b,c,d)) -> [a] -> LneM ([b],[c],[d])
914 mapAndUnzip3Lne f [] = returnLne ([],[],[])
915 mapAndUnzip3Lne f (x:xs)
916 = f x `thenLne` \ (r1, r2, r3) ->
917 mapAndUnzip3Lne f xs `thenLne` \ (rs1, rs2, rs3) ->
918 returnLne (r1:rs1, r2:rs2, r3:rs3)
920 mapAndUnzip4Lne :: (a -> LneM (b,c,d,e)) -> [a] -> LneM ([b],[c],[d],[e])
921 mapAndUnzip4Lne f [] = returnLne ([],[],[],[])
922 mapAndUnzip4Lne f (x:xs)
923 = f x `thenLne` \ (r1, r2, r3, r4) ->
924 mapAndUnzip4Lne f xs `thenLne` \ (rs1, rs2, rs3, rs4) ->
925 returnLne (r1:rs1, r2:rs2, r3:rs3, r4:rs4)
927 fixLne :: (a -> LneM a) -> LneM a
928 fixLne expr env lvs_cont
931 result = expr result env lvs_cont
934 Functions specific to this monad:
937 getVarsLiveInCont :: LneM LiveInfo
938 getVarsLiveInCont env lvs_cont = lvs_cont
940 setVarsLiveInCont :: LiveInfo -> LneM a -> LneM a
941 setVarsLiveInCont new_lvs_cont expr env lvs_cont
942 = expr env new_lvs_cont
944 extendVarEnvLne :: [(Id, HowBound)] -> LneM a -> LneM a
945 extendVarEnvLne ids_w_howbound expr env lvs_cont
946 = expr (extendVarEnvList env ids_w_howbound) lvs_cont
948 lookupVarLne :: Id -> LneM HowBound
949 lookupVarLne v env lvs_cont = returnLne (lookupBinding env v) env lvs_cont
951 getEnvLne :: LneM (IdEnv HowBound)
952 getEnvLne env lvs_cont = returnLne env env lvs_cont
954 lookupBinding :: IdEnv HowBound -> Id -> HowBound
955 lookupBinding env v = case lookupVarEnv env v of
957 Nothing -> ASSERT2( isGlobalId v, ppr v ) ImportBound
960 -- The result of lookupLiveVarsForSet, a set of live variables, is
961 -- only ever tacked onto a decorated expression. It is never used as
962 -- the basis of a control decision, which might give a black hole.
964 freeVarsToLiveVars :: FreeVarsInfo -> LneM LiveInfo
965 freeVarsToLiveVars fvs env live_in_cont
966 = returnLne live_info env live_in_cont
968 live_info = foldr unionLiveInfo live_in_cont lvs_from_fvs
969 lvs_from_fvs = map do_one (allFreeIds fvs)
971 do_one (v, how_bound)
973 ImportBound -> unitLiveCaf v -- Only CAF imports are
976 | mayHaveCafRefs (idCafInfo v) -> unitLiveCaf v
977 | otherwise -> emptyLiveInfo
979 LetBound (NestedLet lvs) _ -> lvs -- lvs already contains v
980 -- (see the invariant on NestedLet)
982 _lambda_or_case_binding -> unitLiveVar v -- Bound by lambda or case
985 %************************************************************************
987 \subsection[Free-var info]{Free variable information}
989 %************************************************************************
992 type FreeVarsInfo = VarEnv (Var, HowBound, StgBinderInfo)
993 -- The Var is so we can gather up the free variables
996 -- The HowBound info just saves repeated lookups;
997 -- we look up just once when we encounter the occurrence.
998 -- INVARIANT: Any ImportBound Ids are HaveCafRef Ids
999 -- Imported Ids without CAF refs are simply
1000 -- not put in the FreeVarsInfo for an expression.
1001 -- See singletonFVInfo and freeVarsToLiveVars
1003 -- StgBinderInfo records how it occurs; notably, we
1004 -- are interested in whether it only occurs in saturated
1005 -- applications, because then we don't need to build a
1007 -- If f is mapped to noBinderInfo, that means
1008 -- that f *is* mentioned (else it wouldn't be in the
1009 -- IdEnv at all), but perhaps in an unsaturated applications.
1011 -- All case/lambda-bound things are also mapped to
1012 -- noBinderInfo, since we aren't interested in their
1015 -- For ILX we track free var info for type variables too;
1016 -- hence VarEnv not IdEnv
1020 emptyFVInfo :: FreeVarsInfo
1021 emptyFVInfo = emptyVarEnv
1023 singletonFVInfo :: Id -> HowBound -> StgBinderInfo -> FreeVarsInfo
1024 -- Don't record non-CAF imports at all, to keep free-var sets small
1025 singletonFVInfo id ImportBound info
1026 | mayHaveCafRefs (idCafInfo id) = unitVarEnv id (id, ImportBound, info)
1027 | otherwise = emptyVarEnv
1028 singletonFVInfo id how_bound info = unitVarEnv id (id, how_bound, info)
1030 tyvarFVInfo :: TyVarSet -> FreeVarsInfo
1031 tyvarFVInfo tvs = foldVarSet add emptyFVInfo tvs
1033 add tv fvs = extendVarEnv fvs tv (tv, LambdaBound, noBinderInfo)
1034 -- Type variables must be lambda-bound
1036 unionFVInfo :: FreeVarsInfo -> FreeVarsInfo -> FreeVarsInfo
1037 unionFVInfo fv1 fv2 = plusVarEnv_C plusFVInfo fv1 fv2
1039 unionFVInfos :: [FreeVarsInfo] -> FreeVarsInfo
1040 unionFVInfos fvs = foldr unionFVInfo emptyFVInfo fvs
1042 minusFVBinders :: [Id] -> FreeVarsInfo -> FreeVarsInfo
1043 minusFVBinders vs fv = foldr minusFVBinder fv vs
1045 minusFVBinder :: Id -> FreeVarsInfo -> FreeVarsInfo
1046 minusFVBinder v fv | isId v && opt_RuntimeTypes
1047 = (fv `delVarEnv` v) `unionFVInfo`
1048 tyvarFVInfo (tyVarsOfType (idType v))
1049 | otherwise = fv `delVarEnv` v
1050 -- When removing a binder, remember to add its type variables
1051 -- c.f. CoreFVs.delBinderFV
1053 elementOfFVInfo :: Id -> FreeVarsInfo -> Bool
1054 elementOfFVInfo id fvs = maybeToBool (lookupVarEnv fvs id)
1056 lookupFVInfo :: FreeVarsInfo -> Id -> StgBinderInfo
1057 -- Find how the given Id is used.
1058 -- Externally visible things may be used any old how
1060 | isExternalName (idName id) = noBinderInfo
1061 | otherwise = case lookupVarEnv fvs id of
1062 Nothing -> noBinderInfo
1063 Just (_,_,info) -> info
1065 allFreeIds :: FreeVarsInfo -> [(Id,HowBound)] -- Both top level and non-top-level Ids
1066 allFreeIds fvs = [(id,how_bound) | (id,how_bound,_) <- varEnvElts fvs, isId id]
1068 -- Non-top-level things only, both type variables and ids
1069 -- (type variables only if opt_RuntimeTypes)
1070 getFVs :: FreeVarsInfo -> [Var]
1071 getFVs fvs = [id | (id, how_bound, _) <- varEnvElts fvs,
1072 not (topLevelBound how_bound) ]
1074 getFVSet :: FreeVarsInfo -> VarSet
1075 getFVSet fvs = mkVarSet (getFVs fvs)
1077 plusFVInfo (id1,hb1,info1) (id2,hb2,info2)
1078 = ASSERT (id1 == id2 && hb1 `check_eq_how_bound` hb2)
1079 (id1, hb1, combineStgBinderInfo info1 info2)
1081 -- The HowBound info for a variable in the FVInfo should be consistent
1082 check_eq_how_bound ImportBound ImportBound = True
1083 check_eq_how_bound LambdaBound LambdaBound = True
1084 check_eq_how_bound (LetBound li1 ar1) (LetBound li2 ar2) = ar1 == ar2 && check_eq_li li1 li2
1085 check_eq_how_bound hb1 hb2 = False
1087 check_eq_li (NestedLet _) (NestedLet _) = True
1088 check_eq_li TopLet TopLet = True
1089 check_eq_li li1 li2 = False
1094 filterStgBinders :: [Var] -> [Var]
1095 filterStgBinders bndrs
1096 | opt_RuntimeTypes = bndrs
1097 | otherwise = filter isId bndrs
1102 -- Ignore all notes except SCC
1103 myCollectBinders expr
1106 go bs (Lam b e) = go (b:bs) e
1107 go bs e@(Note (SCC _) _) = (reverse bs, e)
1108 go bs (Cast e co) = go bs e
1109 go bs (Note _ e) = go bs e
1110 go bs e = (reverse bs, e)
1112 myCollectArgs :: CoreExpr -> (Id, [CoreArg])
1113 -- We assume that we only have variables
1114 -- in the function position by now
1118 go (Var v) as = (v, as)
1119 go (App f a) as = go f (a:as)
1120 go (Note (SCC _) e) as = pprPanic "CoreToStg.myCollectArgs" (ppr expr)
1121 go (Cast e co) as = go e as
1122 go (Note n e) as = go e as
1123 go _ as = pprPanic "CoreToStg.myCollectArgs" (ppr expr)
1127 stgArity :: Id -> HowBound -> Arity
1128 stgArity f (LetBound _ arity) = arity
1129 stgArity f ImportBound = idArity f
1130 stgArity f LambdaBound = 0