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)
177 (stg_rhs, fvs', lv_info) =
179 coreToTopStgRhs body_fvs (id,rhs) `thenLne` \ (stg_rhs, fvs') ->
180 freeVarsToLiveVars fvs' `thenLne` \ lv_info ->
181 returnLne (stg_rhs, fvs', lv_info)
184 bind = StgNonRec (mkSRT lv_info) id stg_rhs
186 ASSERT2(manifestArity rhs == stgRhsArity stg_rhs, ppr id)
187 ASSERT2(consistentCafInfo id bind, ppr id)
188 -- WARN(not (consistent caf_info bind), ppr id <+> ppr cafs <+> ppCafInfo caf_info)
189 (env', fvs' `unionFVInfo` body_fvs, bind)
191 coreTopBindToStg env body_fvs (Rec pairs)
193 (binders, rhss) = unzip pairs
195 extra_env' = [ (b, LetBound TopLet (manifestArity rhs))
196 | (b, rhs) <- pairs ]
197 env' = extendVarEnvList env extra_env'
199 (stg_rhss, fvs', lv_info)
201 mapAndUnzipLne (coreToTopStgRhs body_fvs) pairs
202 `thenLne` \ (stg_rhss, fvss') ->
203 let fvs' = unionFVInfos fvss' in
204 freeVarsToLiveVars fvs' `thenLne` \ lv_info ->
205 returnLne (stg_rhss, fvs', lv_info)
208 bind = StgRec (mkSRT lv_info) (zip binders stg_rhss)
210 ASSERT2(and [manifestArity rhs == stgRhsArity stg_rhs | (rhs,stg_rhs) <- rhss `zip` stg_rhss], ppr binders)
211 ASSERT2(consistentCafInfo (head binders) bind, ppr binders)
212 (env', fvs' `unionFVInfo` body_fvs, bind)
215 -- Assertion helper: this checks that the CafInfo on the Id matches
216 -- what CoreToStg has figured out about the binding's SRT. The
217 -- CafInfo will be exact in all cases except when CorePrep has
218 -- floated out a binding, in which case it will be approximate.
219 consistentCafInfo id bind
220 | occNameFS (nameOccName (idName id)) == FSLIT("sat")
223 = WARN (not exact, ppr id) safe
225 safe = id_marked_caffy || not binding_is_caffy
226 exact = id_marked_caffy == binding_is_caffy
227 id_marked_caffy = mayHaveCafRefs (idCafInfo id)
228 binding_is_caffy = stgBindHasCafRefs bind
234 :: FreeVarsInfo -- Free var info for the scope of the binding
236 -> LneM (StgRhs, FreeVarsInfo)
238 coreToTopStgRhs scope_fv_info (bndr, rhs)
239 = coreToStgExpr rhs `thenLne` \ (new_rhs, rhs_fvs, _) ->
240 returnLne (mkTopStgRhs upd rhs_fvs bndr_info new_rhs, rhs_fvs)
242 bndr_info = lookupFVInfo scope_fv_info bndr
244 upd | rhsIsNonUpd rhs = SingleEntry
245 | otherwise = Updatable
247 mkTopStgRhs :: UpdateFlag -> FreeVarsInfo -> StgBinderInfo -> StgExpr -> StgRhs
249 mkTopStgRhs upd rhs_fvs binder_info (StgLam _ bndrs body)
250 = StgRhsClosure noCCS binder_info
255 mkTopStgRhs upd rhs_fvs binder_info (StgConApp con args)
256 | not (isUpdatable upd) -- StgConApps can be updatable (see isCrossDllConApp)
257 = StgRhsCon noCCS con args
259 mkTopStgRhs upd rhs_fvs binder_info rhs
260 = StgRhsClosure noCCS binder_info
267 -- ---------------------------------------------------------------------------
269 -- ---------------------------------------------------------------------------
274 -> LneM (StgExpr, -- Decorated STG expr
275 FreeVarsInfo, -- Its free vars (NB free, not live)
276 EscVarsSet) -- Its escapees, a subset of its free vars;
277 -- also a subset of the domain of the envt
278 -- because we are only interested in the escapees
279 -- for vars which might be turned into
280 -- let-no-escaped ones.
283 The second and third components can be derived in a simple bottom up pass, not
284 dependent on any decisions about which variables will be let-no-escaped or
285 not. The first component, that is, the decorated expression, may then depend
286 on these components, but it in turn is not scrutinised as the basis for any
287 decisions. Hence no black holes.
290 coreToStgExpr (Lit l) = returnLne (StgLit l, emptyFVInfo, emptyVarSet)
291 coreToStgExpr (Var v) = coreToStgApp Nothing v []
293 coreToStgExpr expr@(App _ _)
294 = coreToStgApp Nothing f args
296 (f, args) = myCollectArgs expr
298 coreToStgExpr expr@(Lam _ _)
300 (args, body) = myCollectBinders expr
301 args' = filterStgBinders args
303 extendVarEnvLne [ (a, LambdaBound) | a <- args' ] $
304 coreToStgExpr body `thenLne` \ (body, body_fvs, body_escs) ->
306 fvs = args' `minusFVBinders` body_fvs
307 escs = body_escs `delVarSetList` args'
308 result_expr | null args' = body
309 | otherwise = StgLam (exprType expr) args' body
311 returnLne (result_expr, fvs, escs)
313 coreToStgExpr (Note (SCC cc) expr)
314 = coreToStgExpr expr `thenLne` ( \ (expr2, fvs, escs) ->
315 returnLne (StgSCC cc expr2, fvs, escs) )
318 -- For ILX, convert (__coerce__ to_ty from_ty e)
319 -- into (coerce to_ty from_ty e)
320 -- where coerce is real function
321 coreToStgExpr (Note (Coerce to_ty from_ty) expr)
322 = coreToStgExpr (mkApps (Var unsafeCoerceId)
323 [Type from_ty, Type to_ty, expr])
326 coreToStgExpr (Note other_note expr)
329 -- Cases require a little more real work.
331 coreToStgExpr (Case scrut bndr alts)
332 = extendVarEnvLne [(bndr, LambdaBound)] (
333 mapAndUnzip3Lne vars_alt alts `thenLne` \ (alts2, fvs_s, escs_s) ->
334 returnLne ( mkStgAlts (idType bndr) alts2,
336 unionVarSets escs_s )
337 ) `thenLne` \ (alts2, alts_fvs, alts_escs) ->
339 -- Determine whether the default binder is dead or not
340 -- This helps the code generator to avoid generating an assignment
341 -- for the case binder (is extremely rare cases) ToDo: remove.
342 bndr' | bndr `elementOfFVInfo` alts_fvs = bndr
343 | otherwise = bndr `setIdOccInfo` IAmDead
345 -- Don't consider the default binder as being 'live in alts',
346 -- since this is from the point of view of the case expr, where
347 -- the default binder is not free.
348 alts_fvs_wo_bndr = bndr `minusFVBinder` alts_fvs
349 alts_escs_wo_bndr = alts_escs `delVarSet` bndr
352 freeVarsToLiveVars alts_fvs_wo_bndr `thenLne` \ alts_lv_info ->
354 -- We tell the scrutinee that everything
355 -- live in the alts is live in it, too.
356 setVarsLiveInCont alts_lv_info (
357 coreToStgExpr scrut `thenLne` \ (scrut2, scrut_fvs, scrut_escs) ->
358 freeVarsToLiveVars scrut_fvs `thenLne` \ scrut_lv_info ->
359 returnLne (scrut2, scrut_fvs, scrut_escs, scrut_lv_info)
361 `thenLne` \ (scrut2, scrut_fvs, scrut_escs, scrut_lv_info) ->
364 StgCase scrut2 (getLiveVars scrut_lv_info)
365 (getLiveVars alts_lv_info)
369 scrut_fvs `unionFVInfo` alts_fvs_wo_bndr,
370 alts_escs_wo_bndr `unionVarSet` getFVSet scrut_fvs
371 -- You might think we should have scrut_escs, not
372 -- (getFVSet scrut_fvs), but actually we can't call, and
373 -- then return from, a let-no-escape thing.
376 vars_alt (con, binders, rhs)
377 = let -- Remove type variables
378 binders' = filterStgBinders binders
380 extendVarEnvLne [(b, LambdaBound) | b <- binders'] $
381 coreToStgExpr rhs `thenLne` \ (rhs2, rhs_fvs, rhs_escs) ->
383 -- Records whether each param is used in the RHS
384 good_use_mask = [ b `elementOfFVInfo` rhs_fvs | b <- binders' ]
386 returnLne ( (con, binders', good_use_mask, rhs2),
387 binders' `minusFVBinders` rhs_fvs,
388 rhs_escs `delVarSetList` binders' )
389 -- ToDo: remove the delVarSet;
390 -- since escs won't include any of these binders
393 Lets not only take quite a bit of work, but this is where we convert
394 then to let-no-escapes, if we wish.
396 (Meanwhile, we don't expect to see let-no-escapes...)
398 coreToStgExpr (Let bind body)
399 = fixLne (\ ~(_, _, _, no_binder_escapes) ->
400 coreToStgLet no_binder_escapes bind body
401 ) `thenLne` \ (new_let, fvs, escs, _) ->
403 returnLne (new_let, fvs, escs)
407 mkStgAlts scrut_ty orig_alts
408 | is_prim_case = StgPrimAlts (tyConAppTyCon scrut_ty) prim_alts deflt
409 | otherwise = StgAlgAlts maybe_tycon alg_alts deflt
411 is_prim_case = isUnLiftedType scrut_ty && not (isUnboxedTupleType scrut_ty)
413 prim_alts = [(lit, rhs) | (LitAlt lit, _, _, rhs) <- other_alts]
414 alg_alts = [(con, bndrs, use, rhs) | (DataAlt con, bndrs, use, rhs) <- other_alts]
417 = case orig_alts of -- DEFAULT is always first if it's there at all
418 (DEFAULT, _, _, rhs) : other_alts -> (other_alts, StgBindDefault rhs)
419 other -> (orig_alts, StgNoDefault)
421 maybe_tycon = case alg_alts of
422 -- Get the tycon from the data con
423 (dc, _, _, _) : _rest -> Just (dataConTyCon dc)
425 -- Otherwise just do your best
426 [] -> case splitTyConApp_maybe (repType scrut_ty) of
427 Just (tc,_) | isAlgTyCon tc -> Just tc
432 -- ---------------------------------------------------------------------------
434 -- ---------------------------------------------------------------------------
438 :: Maybe UpdateFlag -- Just upd <=> this application is
439 -- the rhs of a thunk binding
440 -- x = [...] \upd [] -> the_app
441 -- with specified update flag
443 -> [CoreArg] -- Arguments
444 -> LneM (StgExpr, FreeVarsInfo, EscVarsSet)
446 coreToStgApp maybe_thunk_body f args
447 = coreToStgArgs args `thenLne` \ (args', args_fvs) ->
448 lookupVarLne f `thenLne` \ how_bound ->
451 n_val_args = valArgCount args
452 not_letrec_bound = not (isLetBound how_bound)
454 = let fvs = singletonFVInfo f how_bound fun_occ in
455 -- e.g. (f :: a -> int) (x :: a)
456 -- Here the free variables are "f", "x" AND the type variable "a"
457 -- coreToStgArgs will deal with the arguments recursively
458 if opt_RuntimeTypes then
459 fvs `unionFVInfo` tyvarFVInfo (tyVarsOfType (varType f))
462 -- Mostly, the arity info of a function is in the fn's IdInfo
463 -- But new bindings introduced by CoreSat may not have no
464 -- arity info; it would do us no good anyway. For example:
465 -- let f = \ab -> e in f
466 -- No point in having correct arity info for f!
467 -- Hence the hasArity stuff below.
468 -- NB: f_arity is only consulted for LetBound things
469 f_arity = stgArity f how_bound
470 saturated = f_arity <= n_val_args
473 | not_letrec_bound = noBinderInfo -- Uninteresting variable
474 | f_arity > 0 && saturated = stgSatOcc -- Saturated or over-saturated function call
475 | otherwise = stgUnsatOcc -- Unsaturated function or thunk
478 | not_letrec_bound = emptyVarSet -- Only letrec-bound escapees are interesting
479 | f_arity == n_val_args = emptyVarSet -- A function *or thunk* with an exactly
480 -- saturated call doesn't escape
481 -- (let-no-escape applies to 'thunks' too)
483 | otherwise = unitVarSet f -- Inexact application; it does escape
485 -- At the moment of the call:
487 -- either the function is *not* let-no-escaped, in which case
488 -- nothing is live except live_in_cont
489 -- or the function *is* let-no-escaped in which case the
490 -- variables it uses are live, but still the function
491 -- itself is not. PS. In this case, the function's
492 -- live vars should already include those of the
493 -- continuation, but it does no harm to just union the
496 res_ty = exprType (mkApps (Var f) args)
497 app = case globalIdDetails f of
498 DataConWorkId dc | saturated -> StgConApp dc args'
499 PrimOpId op -> ASSERT( saturated )
500 StgOpApp (StgPrimOp op) args' res_ty
501 FCallId call -> ASSERT( saturated )
502 StgOpApp (StgFCallOp call (idUnique f)) args' res_ty
503 _other -> StgApp f args'
508 fun_fvs `unionFVInfo` args_fvs,
509 fun_escs `unionVarSet` (getFVSet args_fvs)
510 -- All the free vars of the args are disqualified
511 -- from being let-no-escaped.
516 -- ---------------------------------------------------------------------------
518 -- This is the guy that turns applications into A-normal form
519 -- ---------------------------------------------------------------------------
521 coreToStgArgs :: [CoreArg] -> LneM ([StgArg], FreeVarsInfo)
523 = returnLne ([], emptyFVInfo)
525 coreToStgArgs (Type ty : args) -- Type argument
526 = coreToStgArgs args `thenLne` \ (args', fvs) ->
527 if opt_RuntimeTypes then
528 returnLne (StgTypeArg ty : args', fvs `unionFVInfo` tyvarFVInfo (tyVarsOfType ty))
530 returnLne (args', fvs)
532 coreToStgArgs (arg : args) -- Non-type argument
533 = coreToStgArgs args `thenLne` \ (stg_args, args_fvs) ->
534 coreToStgExpr arg `thenLne` \ (arg', arg_fvs, escs) ->
536 fvs = args_fvs `unionFVInfo` arg_fvs
537 stg_arg = case arg' of
538 StgApp v [] -> StgVarArg v
539 StgConApp con [] -> StgVarArg (dataConWorkId con)
540 StgLit lit -> StgLitArg lit
541 _ -> pprPanic "coreToStgArgs" (ppr arg)
543 returnLne (stg_arg : stg_args, fvs)
546 -- ---------------------------------------------------------------------------
547 -- The magic for lets:
548 -- ---------------------------------------------------------------------------
551 :: Bool -- True <=> yes, we are let-no-escaping this let
552 -> CoreBind -- bindings
554 -> LneM (StgExpr, -- new let
555 FreeVarsInfo, -- variables free in the whole let
556 EscVarsSet, -- variables that escape from the whole let
557 Bool) -- True <=> none of the binders in the bindings
558 -- is among the escaping vars
560 coreToStgLet let_no_escape bind body
561 = fixLne (\ ~(_, _, _, _, _, rec_body_fvs, _, _) ->
563 -- Do the bindings, setting live_in_cont to empty if
564 -- we ain't in a let-no-escape world
565 getVarsLiveInCont `thenLne` \ live_in_cont ->
566 setVarsLiveInCont (if let_no_escape
569 (vars_bind rec_body_fvs bind)
570 `thenLne` \ ( bind2, bind_fvs, bind_escs, bind_lv_info, env_ext) ->
573 extendVarEnvLne env_ext (
574 coreToStgExpr body `thenLne` \(body2, body_fvs, body_escs) ->
575 freeVarsToLiveVars body_fvs `thenLne` \ body_lv_info ->
577 returnLne (bind2, bind_fvs, bind_escs, getLiveVars bind_lv_info,
578 body2, body_fvs, body_escs, getLiveVars body_lv_info)
581 ) `thenLne` (\ (bind2, bind_fvs, bind_escs, bind_lvs,
582 body2, body_fvs, body_escs, body_lvs) ->
585 -- Compute the new let-expression
587 new_let | let_no_escape = StgLetNoEscape live_in_whole_let bind_lvs bind2 body2
588 | otherwise = StgLet bind2 body2
591 = binders `minusFVBinders` (bind_fvs `unionFVInfo` body_fvs)
594 = bind_lvs `unionVarSet` (body_lvs `delVarSetList` binders)
596 real_bind_escs = if let_no_escape then
600 -- Everything escapes which is free in the bindings
602 let_escs = (real_bind_escs `unionVarSet` body_escs) `delVarSetList` binders
604 all_escs = bind_escs `unionVarSet` body_escs -- Still includes binders of
607 no_binder_escapes = isEmptyVarSet (set_of_binders `intersectVarSet` all_escs)
610 -- Debugging code as requested by Andrew Kennedy
611 checked_no_binder_escapes
612 | not no_binder_escapes && any is_join_var binders
613 = pprTrace "Interesting! A join var that isn't let-no-escaped" (ppr binders)
615 | otherwise = no_binder_escapes
617 checked_no_binder_escapes = no_binder_escapes
620 -- Mustn't depend on the passed-in let_no_escape flag, since
621 -- no_binder_escapes is used by the caller to derive the flag!
627 checked_no_binder_escapes
630 set_of_binders = mkVarSet binders
631 binders = bindersOf bind
633 mk_binding bind_lv_info binder rhs
634 = (binder, LetBound (NestedLet live_vars) (manifestArity rhs))
636 live_vars | let_no_escape = addLiveVar bind_lv_info binder
637 | otherwise = unitLiveVar binder
638 -- c.f. the invariant on NestedLet
640 vars_bind :: FreeVarsInfo -- Free var info for body of binding
644 EscVarsSet, -- free vars; escapee vars
645 LiveInfo, -- Vars and CAFs live in binding
646 [(Id, HowBound)]) -- extension to environment
649 vars_bind body_fvs (NonRec binder rhs)
650 = coreToStgRhs body_fvs (binder,rhs)
651 `thenLne` \ (rhs2, bind_fvs, escs) ->
653 freeVarsToLiveVars bind_fvs `thenLne` \ bind_lv_info ->
655 env_ext_item = mk_binding bind_lv_info binder rhs
657 returnLne (StgNonRec (mkSRT bind_lv_info) 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 mapAndUnzip3Lne (coreToStgRhs rec_scope_fvs) pairs
671 `thenLne` \ (rhss2, fvss, escss) ->
673 bind_fvs = unionFVInfos fvss
674 escs = unionVarSets escss
676 freeVarsToLiveVars (binders `minusFVBinders` bind_fvs)
677 `thenLne` \ bind_lv_info ->
679 returnLne (StgRec (mkSRT bind_lv_info) (binders `zip` rhss2),
680 bind_fvs, escs, bind_lv_info, env_ext)
684 is_join_var :: Id -> Bool
685 -- A hack (used only for compiler debuggging) to tell if
686 -- a variable started life as a join point ($j)
687 is_join_var j = occNameUserString (getOccName j) == "$j"
691 coreToStgRhs :: FreeVarsInfo -- Free var info for the scope of the binding
693 -> LneM (StgRhs, FreeVarsInfo, EscVarsSet)
695 coreToStgRhs scope_fv_info (bndr, rhs)
696 = coreToStgExpr rhs `thenLne` \ (new_rhs, rhs_fvs, rhs_escs) ->
697 getEnvLne `thenLne` \ env ->
698 returnLne (mkStgRhs env rhs_fvs bndr_info new_rhs,
701 bndr_info = lookupFVInfo scope_fv_info bndr
703 mkStgRhs :: IdEnv HowBound -> FreeVarsInfo -> StgBinderInfo -> StgExpr -> StgRhs
705 mkStgRhs env rhs_fvs binder_info (StgConApp con args)
706 = StgRhsCon noCCS con args
708 mkStgRhs env rhs_fvs binder_info (StgLam _ bndrs body)
709 = StgRhsClosure noCCS binder_info
714 mkStgRhs env rhs_fvs 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 fixLne :: (a -> LneM a) -> LneM a
900 fixLne expr env lvs_cont
903 result = expr result env lvs_cont
906 Functions specific to this monad:
909 getVarsLiveInCont :: LneM LiveInfo
910 getVarsLiveInCont env lvs_cont = lvs_cont
912 setVarsLiveInCont :: LiveInfo -> LneM a -> LneM a
913 setVarsLiveInCont new_lvs_cont expr env lvs_cont
914 = expr env new_lvs_cont
916 extendVarEnvLne :: [(Id, HowBound)] -> LneM a -> LneM a
917 extendVarEnvLne ids_w_howbound expr env lvs_cont
918 = expr (extendVarEnvList env ids_w_howbound) lvs_cont
920 lookupVarLne :: Id -> LneM HowBound
921 lookupVarLne v env lvs_cont = returnLne (lookupBinding env v) env lvs_cont
923 getEnvLne :: LneM (IdEnv HowBound)
924 getEnvLne env lvs_cont = returnLne env env lvs_cont
926 lookupBinding :: IdEnv HowBound -> Id -> HowBound
927 lookupBinding env v = case lookupVarEnv env v of
929 Nothing -> ASSERT2( isGlobalId v, ppr v ) ImportBound
932 -- The result of lookupLiveVarsForSet, a set of live variables, is
933 -- only ever tacked onto a decorated expression. It is never used as
934 -- the basis of a control decision, which might give a black hole.
936 freeVarsToLiveVars :: FreeVarsInfo -> LneM LiveInfo
937 freeVarsToLiveVars fvs env live_in_cont
938 = returnLne live_info env live_in_cont
940 live_info = foldr unionLiveInfo live_in_cont lvs_from_fvs
941 lvs_from_fvs = map do_one (allFreeIds fvs)
943 do_one (v, how_bound)
945 ImportBound -> unitLiveCaf v -- Only CAF imports are
948 | mayHaveCafRefs (idCafInfo v) -> unitLiveCaf v
949 | otherwise -> emptyLiveInfo
951 LetBound (NestedLet lvs) _ -> lvs -- lvs already contains v
952 -- (see the invariant on NestedLet)
954 _lambda_or_case_binding -> unitLiveVar v -- Bound by lambda or case
957 %************************************************************************
959 \subsection[Free-var info]{Free variable information}
961 %************************************************************************
964 type FreeVarsInfo = VarEnv (Var, HowBound, StgBinderInfo)
965 -- The Var is so we can gather up the free variables
968 -- The HowBound info just saves repeated lookups;
969 -- we look up just once when we encounter the occurrence.
970 -- INVARIANT: Any ImportBound Ids are HaveCafRef Ids
971 -- Imported Ids without CAF refs are simply
972 -- not put in the FreeVarsInfo for an expression.
973 -- See singletonFVInfo and freeVarsToLiveVars
975 -- StgBinderInfo records how it occurs; notably, we
976 -- are interested in whether it only occurs in saturated
977 -- applications, because then we don't need to build a
979 -- If f is mapped to noBinderInfo, that means
980 -- that f *is* mentioned (else it wouldn't be in the
981 -- IdEnv at all), but perhaps in an unsaturated applications.
983 -- All case/lambda-bound things are also mapped to
984 -- noBinderInfo, since we aren't interested in their
987 -- For ILX we track free var info for type variables too;
988 -- hence VarEnv not IdEnv
992 emptyFVInfo :: FreeVarsInfo
993 emptyFVInfo = emptyVarEnv
995 singletonFVInfo :: Id -> HowBound -> StgBinderInfo -> FreeVarsInfo
996 -- Don't record non-CAF imports at all, to keep free-var sets small
997 singletonFVInfo id ImportBound info
998 | mayHaveCafRefs (idCafInfo id) = unitVarEnv id (id, ImportBound, info)
999 | otherwise = emptyVarEnv
1000 singletonFVInfo id how_bound info = unitVarEnv id (id, how_bound, info)
1002 tyvarFVInfo :: TyVarSet -> FreeVarsInfo
1003 tyvarFVInfo tvs = foldVarSet add emptyFVInfo tvs
1005 add tv fvs = extendVarEnv fvs tv (tv, LambdaBound, noBinderInfo)
1006 -- Type variables must be lambda-bound
1008 unionFVInfo :: FreeVarsInfo -> FreeVarsInfo -> FreeVarsInfo
1009 unionFVInfo fv1 fv2 = plusVarEnv_C plusFVInfo fv1 fv2
1011 unionFVInfos :: [FreeVarsInfo] -> FreeVarsInfo
1012 unionFVInfos fvs = foldr unionFVInfo emptyFVInfo fvs
1014 minusFVBinders :: [Id] -> FreeVarsInfo -> FreeVarsInfo
1015 minusFVBinders vs fv = foldr minusFVBinder fv vs
1017 minusFVBinder :: Id -> FreeVarsInfo -> FreeVarsInfo
1018 minusFVBinder v fv | isId v && opt_RuntimeTypes
1019 = (fv `delVarEnv` v) `unionFVInfo`
1020 tyvarFVInfo (tyVarsOfType (idType v))
1021 | otherwise = fv `delVarEnv` v
1022 -- When removing a binder, remember to add its type variables
1023 -- c.f. CoreFVs.delBinderFV
1025 elementOfFVInfo :: Id -> FreeVarsInfo -> Bool
1026 elementOfFVInfo id fvs = maybeToBool (lookupVarEnv fvs id)
1028 lookupFVInfo :: FreeVarsInfo -> Id -> StgBinderInfo
1029 -- Find how the given Id is used.
1030 -- Externally visible things may be used any old how
1032 | isExternalName (idName id) = noBinderInfo
1033 | otherwise = case lookupVarEnv fvs id of
1034 Nothing -> noBinderInfo
1035 Just (_,_,info) -> info
1037 allFreeIds :: FreeVarsInfo -> [(Id,HowBound)] -- Both top level and non-top-level Ids
1038 allFreeIds fvs = [(id,how_bound) | (id,how_bound,_) <- rngVarEnv fvs, isId id]
1040 -- Non-top-level things only, both type variables and ids
1041 -- (type variables only if opt_RuntimeTypes)
1042 getFVs :: FreeVarsInfo -> [Var]
1043 getFVs fvs = [id | (id, how_bound, _) <- rngVarEnv fvs,
1044 not (topLevelBound how_bound) ]
1046 getFVSet :: FreeVarsInfo -> VarSet
1047 getFVSet fvs = mkVarSet (getFVs fvs)
1049 plusFVInfo (id1,hb1,info1) (id2,hb2,info2)
1050 = ASSERT (id1 == id2 && hb1 `check_eq_how_bound` hb2)
1051 (id1, hb1, combineStgBinderInfo info1 info2)
1054 -- The HowBound info for a variable in the FVInfo should be consistent
1055 check_eq_how_bound ImportBound ImportBound = True
1056 check_eq_how_bound LambdaBound LambdaBound = True
1057 check_eq_how_bound (LetBound li1 ar1) (LetBound li2 ar2) = ar1 == ar2 && check_eq_li li1 li2
1058 check_eq_how_bound hb1 hb2 = False
1060 check_eq_li (NestedLet _) (NestedLet _) = True
1061 check_eq_li TopLet TopLet = True
1062 check_eq_li li1 li2 = False
1068 filterStgBinders :: [Var] -> [Var]
1069 filterStgBinders bndrs
1070 | opt_RuntimeTypes = bndrs
1071 | otherwise = filter isId bndrs
1076 -- Ignore all notes except SCC
1077 myCollectBinders expr
1080 go bs (Lam b e) = go (b:bs) e
1081 go bs e@(Note (SCC _) _) = (reverse bs, e)
1082 go bs (Note _ e) = go bs e
1083 go bs e = (reverse bs, e)
1085 myCollectArgs :: CoreExpr -> (Id, [CoreArg])
1086 -- We assume that we only have variables
1087 -- in the function position by now
1091 go (Var v) as = (v, as)
1092 go (App f a) as = go f (a:as)
1093 go (Note (SCC _) e) as = pprPanic "CoreToStg.myCollectArgs" (ppr expr)
1094 go (Note n e) as = go e as
1095 go _ as = pprPanic "CoreToStg.myCollectArgs" (ppr expr)
1099 stgArity :: Id -> HowBound -> Arity
1100 stgArity f (LetBound _ arity) = arity
1101 stgArity f ImportBound = idArity f
1102 stgArity f LambdaBound = 0