2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[StgSyn]{Shared term graph (STG) syntax for spineless-tagless code generation}
6 This data type represents programs just before code generation
7 (conversion to @AbstractC@): basically, what we have is a stylised
8 form of @CoreSyntax@, the style being one that happens to be ideally
9 suited to spineless tagless code generation.
16 GenStgBinding(..), GenStgExpr(..), GenStgRhs(..),
17 GenStgAlt, AltType(..),
19 UpdateFlag(..), isUpdatable,
22 noBinderInfo, stgSatOcc, stgUnsatOcc, satCallsOnly,
25 -- a set of synonyms for the most common (only :-) parameterisation
27 StgBinding, StgExpr, StgRhs, StgAlt,
33 SRT(..), noSRT, nonEmptySRT,
36 stgBindHasCafRefs, stgArgHasCafRefs, stgRhsArity, getArgPrimRep,
37 isLitLitArg, isDllConApp, isStgTypeArg,
38 stgArgType, stgBinders,
40 pprStgBinding, pprStgBindings, pprStgBindingsWithSRTs
47 #include "HsVersions.h"
49 import CostCentre ( CostCentreStack, CostCentre )
50 import VarSet ( IdSet, isEmptyVarSet )
52 import Id ( Id, idName, idPrimRep, idType, idCafInfo )
53 import IdInfo ( mayHaveCafRefs )
54 import Name ( isDllName )
55 import Literal ( Literal, literalType, isLitLitLit, literalPrimRep )
56 import ForeignCall ( ForeignCall )
57 import DataCon ( DataCon, dataConName )
58 import CoreSyn ( AltCon )
59 import PrimOp ( PrimOp )
63 import TyCon ( TyCon )
64 import UniqSet ( isEmptyUniqSet, uniqSetToList, UniqSet )
65 import Unique ( Unique )
67 import CmdLineOpts ( opt_SccProfilingOn )
70 %************************************************************************
72 \subsection{@GenStgBinding@}
74 %************************************************************************
76 As usual, expressions are interesting; other things are boring. Here
77 are the boring things [except note the @GenStgRhs@], parameterised
78 with respect to binder and occurrence information (just as in
81 There is one SRT for each group of bindings.
84 data GenStgBinding bndr occ
85 = StgNonRec bndr (GenStgRhs bndr occ)
86 | StgRec [(bndr, GenStgRhs bndr occ)]
88 stgBinders :: GenStgBinding bndr occ -> [bndr]
89 stgBinders (StgNonRec b _) = [b]
90 stgBinders (StgRec bs) = map fst bs
93 %************************************************************************
95 \subsection{@GenStgArg@}
97 %************************************************************************
103 | StgTypeArg Type -- For when we want to preserve all type info
107 getArgPrimRep (StgVarArg local) = idPrimRep local
108 getArgPrimRep (StgLitArg lit) = literalPrimRep lit
110 isLitLitArg (StgLitArg lit) = isLitLitLit lit
111 isLitLitArg _ = False
113 isStgTypeArg (StgTypeArg _) = True
114 isStgTypeArg other = False
116 isDllArg :: StgArg -> Bool
117 -- Does this argument refer to something in a different DLL?
118 isDllArg (StgTypeArg v) = False
119 isDllArg (StgVarArg v) = isDllName (idName v)
120 isDllArg (StgLitArg lit) = isLitLitLit lit
122 isDllConApp :: DataCon -> [StgArg] -> Bool
123 -- Does this constructor application refer to
124 -- anything in a different DLL?
125 -- If so, we can't allocate it statically
126 isDllConApp con args = isDllName (dataConName con) || any isDllArg args
128 stgArgType :: StgArg -> Type
129 -- Very half baked becase we have lost the type arguments
130 stgArgType (StgVarArg v) = idType v
131 stgArgType (StgLitArg lit) = literalType lit
132 stgArgType (StgTypeArg lit) = panic "stgArgType called on stgTypeArg"
135 %************************************************************************
137 \subsection{STG expressions}
139 %************************************************************************
141 The @GenStgExpr@ data type is parameterised on binder and occurrence
144 %************************************************************************
146 \subsubsection{@GenStgExpr@ application}
148 %************************************************************************
150 An application is of a function to a list of atoms [not expressions].
151 Operationally, we want to push the arguments on the stack and call the
152 function. (If the arguments were expressions, we would have to build
153 their closures first.)
155 There is no constructor for a lone variable; it would appear as
158 type GenStgLiveVars occ = UniqSet occ
160 data GenStgExpr bndr occ
163 [GenStgArg occ] -- arguments; may be empty
166 %************************************************************************
168 \subsubsection{@StgConApp@ and @StgPrimApp@---saturated applications}
170 %************************************************************************
172 There are a specialised forms of application, for
173 constructors, primitives, and literals.
178 [GenStgArg occ] -- Saturated
180 | StgOpApp StgOp -- Primitive op or foreign call
181 [GenStgArg occ] -- Saturated
182 Type -- Result type; we need to know the result type
183 -- so that we can assign result registers.
186 %************************************************************************
188 \subsubsection{@StgLam@}
190 %************************************************************************
192 StgLam is used *only* during CoreToStg's work. Before CoreToStg has finished
193 it encodes (\x -> e) as (let f = \x -> e in f)
197 Type -- Type of whole lambda (useful when making a binder for it)
199 StgExpr -- Body of lambda
203 %************************************************************************
205 \subsubsection{@GenStgExpr@: case-expressions}
207 %************************************************************************
209 This has the same boxed/unboxed business as Core case expressions.
212 (GenStgExpr bndr occ)
213 -- the thing to examine
215 (GenStgLiveVars occ) -- Live vars of whole case expression,
216 -- plus everything that happens after the case
217 -- i.e., those which mustn't be overwritten
219 (GenStgLiveVars occ) -- Live vars of RHSs (plus what happens afterwards)
220 -- i.e., those which must be saved before eval.
222 -- note that an alt's constructor's
223 -- binder-variables are NOT counted in the
224 -- free vars for the alt's RHS
226 bndr -- binds the result of evaluating the scrutinee
228 SRT -- The SRT for the continuation
232 [GenStgAlt bndr occ] -- The DEFAULT case is always *first*
233 -- if it is there at all
236 %************************************************************************
238 \subsubsection{@GenStgExpr@: @let(rec)@-expressions}
240 %************************************************************************
242 The various forms of let(rec)-expression encode most of the
243 interesting things we want to do.
247 let-closure x = [free-vars] expr [args]
252 let x = (\free-vars -> \args -> expr) free-vars
254 \tr{args} may be empty (and is for most closures). It isn't under
255 circumstances like this:
261 let-closure x = [z] [y] (y+z)
263 The idea is that we compile code for @(y+z)@ in an environment in which
264 @z@ is bound to an offset from \tr{Node}, and @y@ is bound to an
265 offset from the stack pointer.
267 (A let-closure is an @StgLet@ with a @StgRhsClosure@ RHS.)
271 let-constructor x = Constructor [args]
275 (A let-constructor is an @StgLet@ with a @StgRhsCon@ RHS.)
278 Letrec-expressions are essentially the same deal as
279 let-closure/let-constructor, so we use a common structure and
280 distinguish between them with an @is_recursive@ boolean flag.
284 let-unboxed u = an arbitrary arithmetic expression in unboxed values
287 All the stuff on the RHS must be fully evaluated. No function calls either!
289 (We've backed away from this toward case-expressions with
290 suitably-magical alts ...)
293 ~[Advanced stuff here! Not to start with, but makes pattern matching
294 generate more efficient code.]
297 let-escapes-not fail = expr
300 Here the idea is that @e'@ guarantees not to put @fail@ in a data structure,
301 or pass it to another function. All @e'@ will ever do is tail-call @fail@.
302 Rather than build a closure for @fail@, all we need do is to record the stack
303 level at the moment of the @let-escapes-not@; then entering @fail@ is just
304 a matter of adjusting the stack pointer back down to that point and entering
309 f x y = let z = huge-expression in
315 (A let-escapes-not is an @StgLetNoEscape@.)
318 We may eventually want:
320 let-literal x = Literal
324 (ToDo: is this obsolete?)
327 And so the code for let(rec)-things:
330 (GenStgBinding bndr occ) -- right hand sides (see below)
331 (GenStgExpr bndr occ) -- body
333 | StgLetNoEscape -- remember: ``advanced stuff''
334 (GenStgLiveVars occ) -- Live in the whole let-expression
335 -- Mustn't overwrite these stack slots
336 -- *Doesn't* include binders of the let(rec).
338 (GenStgLiveVars occ) -- Live in the right hand sides (only)
339 -- These are the ones which must be saved on
340 -- the stack if they aren't there already
341 -- *Does* include binders of the let(rec) if recursive.
343 (GenStgBinding bndr occ) -- right hand sides (see below)
344 (GenStgExpr bndr occ) -- body
347 %************************************************************************
349 \subsubsection{@GenStgExpr@: @scc@ expressions}
351 %************************************************************************
353 Finally for @scc@ expressions we introduce a new STG construct.
357 CostCentre -- label of SCC expression
358 (GenStgExpr bndr occ) -- scc expression
362 %************************************************************************
364 \subsection{STG right-hand sides}
366 %************************************************************************
368 Here's the rest of the interesting stuff for @StgLet@s; the first
369 flavour is for closures:
371 data GenStgRhs bndr occ
373 CostCentreStack -- CCS to be attached (default is CurrentCCS)
374 StgBinderInfo -- Info about how this binder is used (see below)
375 [occ] -- non-global free vars; a list, rather than
376 -- a set, because order is important
377 !UpdateFlag -- ReEntrant | Updatable | SingleEntry
378 SRT -- The SRT reference
379 [bndr] -- arguments; if empty, then not a function;
380 -- as above, order is important.
381 (GenStgExpr bndr occ) -- body
383 An example may be in order. Consider:
385 let t = \x -> \y -> ... x ... y ... p ... q in e
387 Pulling out the free vars and stylising somewhat, we get the equivalent:
389 let t = (\[p,q] -> \[x,y] -> ... x ... y ... p ...q) p q
391 Stg-operationally, the @[x,y]@ are on the stack, the @[p,q]@ are
392 offsets from @Node@ into the closure, and the code ptr for the closure
393 will be exactly that in parentheses above.
395 The second flavour of right-hand-side is for constructors (simple but important):
398 CostCentreStack -- CCS to be attached (default is CurrentCCS).
399 -- Top-level (static) ones will end up with
400 -- DontCareCCS, because we don't count static
401 -- data in heap profiles, and we don't set CCCS
402 -- from static closure.
403 DataCon -- constructor
404 [GenStgArg occ] -- args
408 stgRhsArity :: StgRhs -> Int
409 stgRhsArity (StgRhsClosure _ _ _ _ _ bndrs _) = count isId bndrs
410 -- The arity never includes type parameters, so
411 -- when keeping type arguments and binders in the Stg syntax
412 -- (opt_RuntimeTypes) we have to fliter out the type binders.
413 stgRhsArity (StgRhsCon _ _ _) = 0
417 stgBindHasCafRefs :: GenStgBinding bndr Id -> Bool
418 stgBindHasCafRefs (StgNonRec _ rhs) = rhsHasCafRefs rhs
419 stgBindHasCafRefs (StgRec binds) = any rhsHasCafRefs (map snd binds)
421 rhsHasCafRefs (StgRhsClosure _ _ _ upd srt _ _)
422 = isUpdatable upd || nonEmptySRT srt
423 rhsHasCafRefs (StgRhsCon _ _ args)
424 = any stgArgHasCafRefs args
426 stgArgHasCafRefs (StgVarArg id) = mayHaveCafRefs (idCafInfo id)
427 stgArgHasCafRefs _ = False
430 Here's the @StgBinderInfo@ type, and its combining op:
434 | SatCallsOnly -- All occurrences are *saturated* *function* calls
435 -- This means we don't need to build an info table and
436 -- slow entry code for the thing
437 -- Thunks never get this value
439 noBinderInfo = NoStgBinderInfo
440 stgUnsatOcc = NoStgBinderInfo
441 stgSatOcc = SatCallsOnly
443 satCallsOnly :: StgBinderInfo -> Bool
444 satCallsOnly SatCallsOnly = True
445 satCallsOnly NoStgBinderInfo = False
447 combineStgBinderInfo :: StgBinderInfo -> StgBinderInfo -> StgBinderInfo
448 combineStgBinderInfo SatCallsOnly SatCallsOnly = SatCallsOnly
449 combineStgBinderInfo info1 info2 = NoStgBinderInfo
452 pp_binder_info NoStgBinderInfo = empty
453 pp_binder_info SatCallsOnly = ptext SLIT("sat-only")
456 %************************************************************************
458 \subsection[Stg-case-alternatives]{STG case alternatives}
460 %************************************************************************
462 Very like in @CoreSyntax@ (except no type-world stuff).
464 The type constructor is guaranteed not to be abstract; that is, we can
465 see its representation. This is important because the code generator
466 uses it to determine return conventions etc. But it's not trivial
467 where there's a moduule loop involved, because some versions of a type
468 constructor might not have all the constructors visible. So
469 mkStgAlgAlts (in CoreToStg) ensures that it gets the TyCon from the
470 constructors or literals (which are guaranteed to have the Real McCoy)
471 rather than from the scrutinee type.
474 type GenStgAlt bndr occ
475 = (AltCon, -- alts: data constructor,
476 [bndr], -- constructor's parameters,
477 [Bool], -- "use mask", same length as
478 -- parameters; a True in a
479 -- param's position if it is
481 GenStgExpr bndr occ) -- ...right-hand side.
484 = PolyAlt -- Polymorphic (a type variable)
485 | UbxTupAlt TyCon -- Unboxed tuple
486 | AlgAlt TyCon -- Algebraic data type; the AltCons will be DataAlts
487 | PrimAlt TyCon -- Primitive data type; the AltCons will be LitAlts
490 %************************************************************************
492 \subsection[Stg]{The Plain STG parameterisation}
494 %************************************************************************
496 This happens to be the only one we use at the moment.
499 type StgBinding = GenStgBinding Id Id
500 type StgArg = GenStgArg Id
501 type StgLiveVars = GenStgLiveVars Id
502 type StgExpr = GenStgExpr Id Id
503 type StgRhs = GenStgRhs Id Id
504 type StgAlt = GenStgAlt Id Id
507 %************************************************************************
509 \subsubsection[UpdateFlag-datatype]{@UpdateFlag@}
511 %************************************************************************
513 This is also used in @LambdaFormInfo@ in the @ClosureInfo@ module.
515 A @ReEntrant@ closure may be entered multiple times, but should not be
516 updated or blackholed. An @Updatable@ closure should be updated after
517 evaluation (and may be blackholed during evaluation). A @SingleEntry@
518 closure will only be entered once, and so need not be updated but may
519 safely be blackholed.
522 data UpdateFlag = ReEntrant | Updatable | SingleEntry
524 instance Outputable UpdateFlag where
526 = char (case u of { ReEntrant -> 'r'; Updatable -> 'u'; SingleEntry -> 's' })
528 isUpdatable ReEntrant = False
529 isUpdatable SingleEntry = False
530 isUpdatable Updatable = True
533 %************************************************************************
535 \subsubsection{StgOp}
537 %************************************************************************
539 An StgOp allows us to group together PrimOps and ForeignCalls.
540 It's quite useful to move these around together, notably
541 in StgOpApp and COpStmt.
544 data StgOp = StgPrimOp PrimOp
546 | StgFCallOp ForeignCall Unique
547 -- The Unique is occasionally needed by the C pretty-printer
548 -- (which lacks a unique supply), notably when generating a
549 -- typedef for foreign-export-dynamic
553 %************************************************************************
555 \subsubsection[Static Reference Tables]{@SRT@}
557 %************************************************************************
559 There is one SRT per top-level function group. Each local binding and
560 case expression within this binding group has a subrange of the whole
561 SRT, expressed as an offset and length.
563 In CoreToStg we collect the list of CafRefs at each SRT site, which is later
564 converted into the length and offset form by the SRT pass.
569 -- generated by CoreToStg
570 | SRT !Int{-offset-} !Int{-length-} !Bitmap{-bitmap-}
571 -- generated by computeSRTs
576 nonEmptySRT NoSRT = False
577 nonEmptySRT (SRTEntries vs) = not (isEmptyVarSet vs)
580 pprSRT (NoSRT) = ptext SLIT("_no_srt_")
581 pprSRT (SRTEntries ids) = text "SRT:" <> ppr ids
582 pprSRT (SRT off length bitmap) = parens (ppr off <> comma <> text "*bitmap*")
585 %************************************************************************
587 \subsection[Stg-pretty-printing]{Pretty-printing}
589 %************************************************************************
591 Robin Popplestone asked for semi-colon separators on STG binds; here's
592 hoping he likes terminators instead... Ditto for case alternatives.
595 pprGenStgBinding :: (Outputable bndr, Outputable bdee, Ord bdee)
596 => GenStgBinding bndr bdee -> SDoc
598 pprGenStgBinding (StgNonRec bndr rhs)
599 = hang (hsep [ppr bndr, equals])
600 4 ((<>) (ppr rhs) semi)
602 pprGenStgBinding (StgRec pairs)
603 = vcat ((ifPprDebug (ptext SLIT("{- StgRec (begin) -}"))) :
604 (map (ppr_bind) pairs) ++ [(ifPprDebug (ptext SLIT("{- StgRec (end) -}")))])
606 ppr_bind (bndr, expr)
607 = hang (hsep [ppr bndr, equals])
608 4 ((<>) (ppr expr) semi)
610 pprStgBinding :: StgBinding -> SDoc
611 pprStgBinding bind = pprGenStgBinding bind
613 pprStgBindings :: [StgBinding] -> SDoc
614 pprStgBindings binds = vcat (map pprGenStgBinding binds)
616 pprGenStgBindingWithSRT
617 :: (Outputable bndr, Outputable bdee, Ord bdee)
618 => (GenStgBinding bndr bdee,[(Id,[Id])]) -> SDoc
620 pprGenStgBindingWithSRT (bind,srts)
621 = vcat (pprGenStgBinding bind : map pprSRT srts)
622 where pprSRT (id,srt) =
623 ptext SLIT("SRT") <> parens (ppr id) <> ptext SLIT(": ") <> ppr srt
625 pprStgBindingsWithSRTs :: [(StgBinding,[(Id,[Id])])] -> SDoc
626 pprStgBindingsWithSRTs binds = vcat (map pprGenStgBindingWithSRT binds)
630 instance (Outputable bdee) => Outputable (GenStgArg bdee) where
633 instance (Outputable bndr, Outputable bdee, Ord bdee)
634 => Outputable (GenStgBinding bndr bdee) where
635 ppr = pprGenStgBinding
637 instance (Outputable bndr, Outputable bdee, Ord bdee)
638 => Outputable (GenStgExpr bndr bdee) where
641 instance (Outputable bndr, Outputable bdee, Ord bdee)
642 => Outputable (GenStgRhs bndr bdee) where
643 ppr rhs = pprStgRhs rhs
647 pprStgArg :: (Outputable bdee) => GenStgArg bdee -> SDoc
649 pprStgArg (StgVarArg var) = ppr var
650 pprStgArg (StgLitArg con) = ppr con
651 pprStgArg (StgTypeArg ty) = char '@' <+> ppr ty
655 pprStgExpr :: (Outputable bndr, Outputable bdee, Ord bdee)
656 => GenStgExpr bndr bdee -> SDoc
658 pprStgExpr (StgLit lit) = ppr lit
661 pprStgExpr (StgApp func args)
663 4 (sep (map (ppr) args))
667 pprStgExpr (StgConApp con args)
668 = hsep [ ppr con, brackets (interppSP args)]
670 pprStgExpr (StgOpApp op args _)
671 = hsep [ pprStgOp op, brackets (interppSP args)]
673 pprStgExpr (StgLam _ bndrs body)
674 =sep [ char '\\' <+> ppr bndrs <+> ptext SLIT("->"),
679 -- special case: let v = <very specific thing>
685 -- Very special! Suspicious! (SLPJ)
688 pprStgExpr (StgLet srt (StgNonRec bndr (StgRhsClosure cc bi free_vars upd_flag args rhs))
691 (hang (hcat [ptext SLIT("let { "), ppr bndr, ptext SLIT(" = "),
694 ptext SLIT(" ["), ifPprDebug (interppSP free_vars), ptext SLIT("] \\"),
695 ppr upd_flag, ptext SLIT(" ["),
696 interppSP args, char ']'])
697 8 (sep [hsep [ppr rhs, ptext SLIT("} in")]]))
701 -- special case: let ... in let ...
703 pprStgExpr (StgLet bind expr@(StgLet _ _))
705 (sep [hang (ptext SLIT("let {"))
706 2 (hsep [pprGenStgBinding bind, ptext SLIT("} in")])])
710 pprStgExpr (StgLet bind expr)
711 = sep [hang (ptext SLIT("let {")) 2 (pprGenStgBinding bind),
712 hang (ptext SLIT("} in ")) 2 (ppr expr)]
714 pprStgExpr (StgLetNoEscape lvs_whole lvs_rhss bind expr)
715 = sep [hang (ptext SLIT("let-no-escape {"))
716 2 (pprGenStgBinding bind),
717 hang ((<>) (ptext SLIT("} in "))
720 hcat [ptext SLIT("-- lvs: ["), interppSP (uniqSetToList lvs_whole),
721 ptext SLIT("]; rhs lvs: ["), interppSP (uniqSetToList lvs_rhss),
725 pprStgExpr (StgSCC cc expr)
726 = sep [ hsep [ptext SLIT("_scc_"), ppr cc],
729 pprStgExpr (StgCase expr lvs_whole lvs_rhss bndr srt alt_type alts)
730 = sep [sep [ptext SLIT("case"),
731 nest 4 (hsep [pprStgExpr expr,
732 ifPprDebug (dcolon <+> ppr alt_type)]),
733 ptext SLIT("of"), ppr bndr, char '{'],
736 hcat [ptext SLIT("-- lvs: ["), interppSP (uniqSetToList lvs_whole),
737 ptext SLIT("]; rhs lvs: ["), interppSP (uniqSetToList lvs_rhss),
740 nest 2 (vcat (map pprStgAlt alts)),
743 pprStgAlt (con, params, use_mask, expr)
744 = hang (hsep [ppr con, interppSP params, ptext SLIT("->")])
747 pprStgOp (StgPrimOp op) = ppr op
748 pprStgOp (StgFCallOp op _) = ppr op
750 instance Outputable AltType where
751 ppr PolyAlt = ptext SLIT("Polymorphic")
752 ppr (UbxTupAlt tc) = ptext SLIT("UbxTup") <+> ppr tc
753 ppr (AlgAlt tc) = ptext SLIT("Alg") <+> ppr tc
754 ppr (PrimAlt tc) = ptext SLIT("Prim") <+> ppr tc
758 pprStgLVs :: Outputable occ => GenStgLiveVars occ -> SDoc
760 = getPprStyle $ \ sty ->
761 if userStyle sty || isEmptyUniqSet lvs then
764 hcat [text "{-lvs:", interpp'SP (uniqSetToList lvs), text "-}"]
768 pprStgRhs :: (Outputable bndr, Outputable bdee, Ord bdee)
769 => GenStgRhs bndr bdee -> SDoc
772 pprStgRhs (StgRhsClosure cc bi [free_var] upd_flag srt [{-no args-}] (StgApp func []))
775 brackets (ifPprDebug (ppr free_var)),
776 ptext SLIT(" \\"), ppr upd_flag, pprMaybeSRT srt, ptext SLIT(" [] "), ppr func ]
779 pprStgRhs (StgRhsClosure cc bi free_vars upd_flag srt args body)
780 = hang (hsep [if opt_SccProfilingOn then ppr cc else empty,
782 ifPprDebug (brackets (interppSP free_vars)),
783 char '\\' <> ppr upd_flag, pprMaybeSRT srt, brackets (interppSP args)])
786 pprStgRhs (StgRhsCon cc con args)
788 space, ppr con, ptext SLIT("! "), brackets (interppSP args)]
790 pprMaybeSRT (NoSRT) = empty
791 pprMaybeSRT srt = ptext SLIT("srt:") <> pprSRT srt