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,
36 stgBindHasCafRefs, stgArgHasCafRefs, stgRhsArity,
37 isDllConApp, isStgTypeArg,
40 pprStgBinding, pprStgBindings, pprStgBindingsWithSRTs
47 #include "HsVersions.h"
49 import CostCentre ( CostCentreStack, CostCentre )
50 import VarSet ( IdSet, isEmptyVarSet )
52 import Id ( Id, idName, idType, idCafInfo )
53 import IdInfo ( mayHaveCafRefs )
54 import Packages ( isDllName )
55 import PackageConfig ( PackageId )
56 import Literal ( Literal, literalType )
57 import ForeignCall ( ForeignCall )
58 import DataCon ( DataCon, dataConName )
59 import CoreSyn ( AltCon )
60 import PprCore ( {- instances -} )
61 import PrimOp ( PrimOp )
65 import TyCon ( TyCon )
66 import UniqSet ( isEmptyUniqSet, uniqSetToList, UniqSet )
67 import Unique ( Unique )
69 import StaticFlags ( opt_SccProfilingOn )
70 import Module ( Module, pprModule )
73 %************************************************************************
75 \subsection{@GenStgBinding@}
77 %************************************************************************
79 As usual, expressions are interesting; other things are boring. Here
80 are the boring things [except note the @GenStgRhs@], parameterised
81 with respect to binder and occurrence information (just as in
84 There is one SRT for each group of bindings.
87 data GenStgBinding bndr occ
88 = StgNonRec bndr (GenStgRhs bndr occ)
89 | StgRec [(bndr, GenStgRhs bndr occ)]
92 %************************************************************************
94 \subsection{@GenStgArg@}
96 %************************************************************************
102 | StgTypeArg Type -- For when we want to preserve all type info
106 isStgTypeArg (StgTypeArg _) = True
107 isStgTypeArg other = False
109 isDllArg :: PackageId -> StgArg -> Bool
110 -- Does this argument refer to something in a different DLL?
111 isDllArg this_pkg (StgTypeArg v) = False
112 isDllArg this_pkg (StgVarArg v) = isDllName this_pkg (idName v)
113 isDllArg this_pkg (StgLitArg lit) = False
115 isDllConApp :: PackageId -> DataCon -> [StgArg] -> Bool
116 -- Does this constructor application refer to
117 -- anything in a different DLL?
118 -- If so, we can't allocate it statically
119 isDllConApp this_pkg con args
120 = isDllName this_pkg (dataConName con) || any (isDllArg this_pkg) args
122 stgArgType :: StgArg -> Type
123 -- Very half baked becase we have lost the type arguments
124 stgArgType (StgVarArg v) = idType v
125 stgArgType (StgLitArg lit) = literalType lit
126 stgArgType (StgTypeArg lit) = panic "stgArgType called on stgTypeArg"
129 %************************************************************************
131 \subsection{STG expressions}
133 %************************************************************************
135 The @GenStgExpr@ data type is parameterised on binder and occurrence
138 %************************************************************************
140 \subsubsection{@GenStgExpr@ application}
142 %************************************************************************
144 An application is of a function to a list of atoms [not expressions].
145 Operationally, we want to push the arguments on the stack and call the
146 function. (If the arguments were expressions, we would have to build
147 their closures first.)
149 There is no constructor for a lone variable; it would appear as
152 type GenStgLiveVars occ = UniqSet occ
154 data GenStgExpr bndr occ
157 [GenStgArg occ] -- arguments; may be empty
160 %************************************************************************
162 \subsubsection{@StgConApp@ and @StgPrimApp@---saturated applications}
164 %************************************************************************
166 There are a specialised forms of application, for
167 constructors, primitives, and literals.
172 [GenStgArg occ] -- Saturated
174 | StgOpApp StgOp -- Primitive op or foreign call
175 [GenStgArg occ] -- Saturated
177 -- We need to know this so that we can
178 -- assign result registers
181 %************************************************************************
183 \subsubsection{@StgLam@}
185 %************************************************************************
187 StgLam is used *only* during CoreToStg's work. Before CoreToStg has finished
188 it encodes (\x -> e) as (let f = \x -> e in f)
192 Type -- Type of whole lambda (useful when making a binder for it)
194 StgExpr -- Body of lambda
198 %************************************************************************
200 \subsubsection{@GenStgExpr@: case-expressions}
202 %************************************************************************
204 This has the same boxed/unboxed business as Core case expressions.
207 (GenStgExpr bndr occ)
208 -- the thing to examine
210 (GenStgLiveVars occ) -- Live vars of whole case expression,
211 -- plus everything that happens after the case
212 -- i.e., those which mustn't be overwritten
214 (GenStgLiveVars occ) -- Live vars of RHSs (plus what happens afterwards)
215 -- i.e., those which must be saved before eval.
217 -- note that an alt's constructor's
218 -- binder-variables are NOT counted in the
219 -- free vars for the alt's RHS
221 bndr -- binds the result of evaluating the scrutinee
223 SRT -- The SRT for the continuation
227 [GenStgAlt bndr occ] -- The DEFAULT case is always *first*
228 -- if it is there at all
231 %************************************************************************
233 \subsubsection{@GenStgExpr@: @let(rec)@-expressions}
235 %************************************************************************
237 The various forms of let(rec)-expression encode most of the
238 interesting things we want to do.
242 let-closure x = [free-vars] expr [args]
247 let x = (\free-vars -> \args -> expr) free-vars
249 \tr{args} may be empty (and is for most closures). It isn't under
250 circumstances like this:
256 let-closure x = [z] [y] (y+z)
258 The idea is that we compile code for @(y+z)@ in an environment in which
259 @z@ is bound to an offset from \tr{Node}, and @y@ is bound to an
260 offset from the stack pointer.
262 (A let-closure is an @StgLet@ with a @StgRhsClosure@ RHS.)
266 let-constructor x = Constructor [args]
270 (A let-constructor is an @StgLet@ with a @StgRhsCon@ RHS.)
273 Letrec-expressions are essentially the same deal as
274 let-closure/let-constructor, so we use a common structure and
275 distinguish between them with an @is_recursive@ boolean flag.
279 let-unboxed u = an arbitrary arithmetic expression in unboxed values
282 All the stuff on the RHS must be fully evaluated. No function calls either!
284 (We've backed away from this toward case-expressions with
285 suitably-magical alts ...)
288 ~[Advanced stuff here! Not to start with, but makes pattern matching
289 generate more efficient code.]
292 let-escapes-not fail = expr
295 Here the idea is that @e'@ guarantees not to put @fail@ in a data structure,
296 or pass it to another function. All @e'@ will ever do is tail-call @fail@.
297 Rather than build a closure for @fail@, all we need do is to record the stack
298 level at the moment of the @let-escapes-not@; then entering @fail@ is just
299 a matter of adjusting the stack pointer back down to that point and entering
304 f x y = let z = huge-expression in
310 (A let-escapes-not is an @StgLetNoEscape@.)
313 We may eventually want:
315 let-literal x = Literal
319 (ToDo: is this obsolete?)
322 And so the code for let(rec)-things:
325 (GenStgBinding bndr occ) -- right hand sides (see below)
326 (GenStgExpr bndr occ) -- body
328 | StgLetNoEscape -- remember: ``advanced stuff''
329 (GenStgLiveVars occ) -- Live in the whole let-expression
330 -- Mustn't overwrite these stack slots
331 -- *Doesn't* include binders of the let(rec).
333 (GenStgLiveVars occ) -- Live in the right hand sides (only)
334 -- These are the ones which must be saved on
335 -- the stack if they aren't there already
336 -- *Does* include binders of the let(rec) if recursive.
338 (GenStgBinding bndr occ) -- right hand sides (see below)
339 (GenStgExpr bndr occ) -- body
342 %************************************************************************
344 \subsubsection{@GenStgExpr@: @scc@ expressions}
346 %************************************************************************
348 Finally for @scc@ expressions we introduce a new STG construct.
352 CostCentre -- label of SCC expression
353 (GenStgExpr bndr occ) -- scc expression
356 %************************************************************************
358 \subsubsection{@GenStgExpr@: @hpc@ expressions}
360 %************************************************************************
362 Finally for @scc@ expressions we introduce a new STG construct.
366 Module -- the module of the source of this tick
368 (GenStgExpr bndr occ) -- sub expression
372 %************************************************************************
374 \subsection{STG right-hand sides}
376 %************************************************************************
378 Here's the rest of the interesting stuff for @StgLet@s; the first
379 flavour is for closures:
381 data GenStgRhs bndr occ
383 CostCentreStack -- CCS to be attached (default is CurrentCCS)
384 StgBinderInfo -- Info about how this binder is used (see below)
385 [occ] -- non-global free vars; a list, rather than
386 -- a set, because order is important
387 !UpdateFlag -- ReEntrant | Updatable | SingleEntry
388 SRT -- The SRT reference
389 [bndr] -- arguments; if empty, then not a function;
390 -- as above, order is important.
391 (GenStgExpr bndr occ) -- body
393 An example may be in order. Consider:
395 let t = \x -> \y -> ... x ... y ... p ... q in e
397 Pulling out the free vars and stylising somewhat, we get the equivalent:
399 let t = (\[p,q] -> \[x,y] -> ... x ... y ... p ...q) p q
401 Stg-operationally, the @[x,y]@ are on the stack, the @[p,q]@ are
402 offsets from @Node@ into the closure, and the code ptr for the closure
403 will be exactly that in parentheses above.
405 The second flavour of right-hand-side is for constructors (simple but important):
408 CostCentreStack -- CCS to be attached (default is CurrentCCS).
409 -- Top-level (static) ones will end up with
410 -- DontCareCCS, because we don't count static
411 -- data in heap profiles, and we don't set CCCS
412 -- from static closure.
413 DataCon -- constructor
414 [GenStgArg occ] -- args
418 stgRhsArity :: StgRhs -> Int
419 stgRhsArity (StgRhsClosure _ _ _ _ _ bndrs _) = count isId bndrs
420 -- The arity never includes type parameters, so
421 -- when keeping type arguments and binders in the Stg syntax
422 -- (opt_RuntimeTypes) we have to fliter out the type binders.
423 stgRhsArity (StgRhsCon _ _ _) = 0
427 stgBindHasCafRefs :: GenStgBinding bndr Id -> Bool
428 stgBindHasCafRefs (StgNonRec _ rhs) = rhsHasCafRefs rhs
429 stgBindHasCafRefs (StgRec binds) = any rhsHasCafRefs (map snd binds)
431 rhsHasCafRefs (StgRhsClosure _ _ _ upd srt _ _)
432 = isUpdatable upd || nonEmptySRT srt
433 rhsHasCafRefs (StgRhsCon _ _ args)
434 = any stgArgHasCafRefs args
436 stgArgHasCafRefs (StgVarArg id) = mayHaveCafRefs (idCafInfo id)
437 stgArgHasCafRefs _ = False
440 Here's the @StgBinderInfo@ type, and its combining op:
444 | SatCallsOnly -- All occurrences are *saturated* *function* calls
445 -- This means we don't need to build an info table and
446 -- slow entry code for the thing
447 -- Thunks never get this value
449 noBinderInfo = NoStgBinderInfo
450 stgUnsatOcc = NoStgBinderInfo
451 stgSatOcc = SatCallsOnly
453 satCallsOnly :: StgBinderInfo -> Bool
454 satCallsOnly SatCallsOnly = True
455 satCallsOnly NoStgBinderInfo = False
457 combineStgBinderInfo :: StgBinderInfo -> StgBinderInfo -> StgBinderInfo
458 combineStgBinderInfo SatCallsOnly SatCallsOnly = SatCallsOnly
459 combineStgBinderInfo info1 info2 = NoStgBinderInfo
462 pp_binder_info NoStgBinderInfo = empty
463 pp_binder_info SatCallsOnly = ptext SLIT("sat-only")
466 %************************************************************************
468 \subsection[Stg-case-alternatives]{STG case alternatives}
470 %************************************************************************
472 Very like in @CoreSyntax@ (except no type-world stuff).
474 The type constructor is guaranteed not to be abstract; that is, we can
475 see its representation. This is important because the code generator
476 uses it to determine return conventions etc. But it's not trivial
477 where there's a moduule loop involved, because some versions of a type
478 constructor might not have all the constructors visible. So
479 mkStgAlgAlts (in CoreToStg) ensures that it gets the TyCon from the
480 constructors or literals (which are guaranteed to have the Real McCoy)
481 rather than from the scrutinee type.
484 type GenStgAlt bndr occ
485 = (AltCon, -- alts: data constructor,
486 [bndr], -- constructor's parameters,
487 [Bool], -- "use mask", same length as
488 -- parameters; a True in a
489 -- param's position if it is
491 GenStgExpr bndr occ) -- ...right-hand side.
494 = PolyAlt -- Polymorphic (a type variable)
495 | UbxTupAlt TyCon -- Unboxed tuple
496 | AlgAlt TyCon -- Algebraic data type; the AltCons will be DataAlts
497 | PrimAlt TyCon -- Primitive data type; the AltCons will be LitAlts
500 %************************************************************************
502 \subsection[Stg]{The Plain STG parameterisation}
504 %************************************************************************
506 This happens to be the only one we use at the moment.
509 type StgBinding = GenStgBinding Id Id
510 type StgArg = GenStgArg Id
511 type StgLiveVars = GenStgLiveVars Id
512 type StgExpr = GenStgExpr Id Id
513 type StgRhs = GenStgRhs Id Id
514 type StgAlt = GenStgAlt Id Id
517 %************************************************************************
519 \subsubsection[UpdateFlag-datatype]{@UpdateFlag@}
521 %************************************************************************
523 This is also used in @LambdaFormInfo@ in the @ClosureInfo@ module.
525 A @ReEntrant@ closure may be entered multiple times, but should not be
526 updated or blackholed. An @Updatable@ closure should be updated after
527 evaluation (and may be blackholed during evaluation). A @SingleEntry@
528 closure will only be entered once, and so need not be updated but may
529 safely be blackholed.
532 data UpdateFlag = ReEntrant | Updatable | SingleEntry
534 instance Outputable UpdateFlag where
536 = char (case u of { ReEntrant -> 'r'; Updatable -> 'u'; SingleEntry -> 's' })
538 isUpdatable ReEntrant = False
539 isUpdatable SingleEntry = False
540 isUpdatable Updatable = True
543 %************************************************************************
545 \subsubsection{StgOp}
547 %************************************************************************
549 An StgOp allows us to group together PrimOps and ForeignCalls.
550 It's quite useful to move these around together, notably
551 in StgOpApp and COpStmt.
554 data StgOp = StgPrimOp PrimOp
556 | StgFCallOp ForeignCall Unique
557 -- The Unique is occasionally needed by the C pretty-printer
558 -- (which lacks a unique supply), notably when generating a
559 -- typedef for foreign-export-dynamic
563 %************************************************************************
565 \subsubsection[Static Reference Tables]{@SRT@}
567 %************************************************************************
569 There is one SRT per top-level function group. Each local binding and
570 case expression within this binding group has a subrange of the whole
571 SRT, expressed as an offset and length.
573 In CoreToStg we collect the list of CafRefs at each SRT site, which is later
574 converted into the length and offset form by the SRT pass.
579 -- generated by CoreToStg
580 | SRT !Int{-offset-} !Int{-length-} !Bitmap{-bitmap-}
581 -- generated by computeSRTs
586 nonEmptySRT NoSRT = False
587 nonEmptySRT (SRTEntries vs) = not (isEmptyVarSet vs)
590 pprSRT (NoSRT) = ptext SLIT("_no_srt_")
591 pprSRT (SRTEntries ids) = text "SRT:" <> ppr ids
592 pprSRT (SRT off length bitmap) = parens (ppr off <> comma <> text "*bitmap*")
595 %************************************************************************
597 \subsection[Stg-pretty-printing]{Pretty-printing}
599 %************************************************************************
601 Robin Popplestone asked for semi-colon separators on STG binds; here's
602 hoping he likes terminators instead... Ditto for case alternatives.
605 pprGenStgBinding :: (Outputable bndr, Outputable bdee, Ord bdee)
606 => GenStgBinding bndr bdee -> SDoc
608 pprGenStgBinding (StgNonRec bndr rhs)
609 = hang (hsep [ppr bndr, equals])
610 4 ((<>) (ppr rhs) semi)
612 pprGenStgBinding (StgRec pairs)
613 = vcat ((ifPprDebug (ptext SLIT("{- StgRec (begin) -}"))) :
614 (map (ppr_bind) pairs) ++ [(ifPprDebug (ptext SLIT("{- StgRec (end) -}")))])
616 ppr_bind (bndr, expr)
617 = hang (hsep [ppr bndr, equals])
618 4 ((<>) (ppr expr) semi)
620 pprStgBinding :: StgBinding -> SDoc
621 pprStgBinding bind = pprGenStgBinding bind
623 pprStgBindings :: [StgBinding] -> SDoc
624 pprStgBindings binds = vcat (map pprGenStgBinding binds)
626 pprGenStgBindingWithSRT
627 :: (Outputable bndr, Outputable bdee, Ord bdee)
628 => (GenStgBinding bndr bdee,[(Id,[Id])]) -> SDoc
630 pprGenStgBindingWithSRT (bind,srts)
631 = vcat (pprGenStgBinding bind : map pprSRT srts)
632 where pprSRT (id,srt) =
633 ptext SLIT("SRT") <> parens (ppr id) <> ptext SLIT(": ") <> ppr srt
635 pprStgBindingsWithSRTs :: [(StgBinding,[(Id,[Id])])] -> SDoc
636 pprStgBindingsWithSRTs binds = vcat (map pprGenStgBindingWithSRT binds)
640 instance (Outputable bdee) => Outputable (GenStgArg bdee) where
643 instance (Outputable bndr, Outputable bdee, Ord bdee)
644 => Outputable (GenStgBinding bndr bdee) where
645 ppr = pprGenStgBinding
647 instance (Outputable bndr, Outputable bdee, Ord bdee)
648 => Outputable (GenStgExpr bndr bdee) where
651 instance (Outputable bndr, Outputable bdee, Ord bdee)
652 => Outputable (GenStgRhs bndr bdee) where
653 ppr rhs = pprStgRhs rhs
657 pprStgArg :: (Outputable bdee) => GenStgArg bdee -> SDoc
659 pprStgArg (StgVarArg var) = ppr var
660 pprStgArg (StgLitArg con) = ppr con
661 pprStgArg (StgTypeArg ty) = char '@' <+> ppr ty
665 pprStgExpr :: (Outputable bndr, Outputable bdee, Ord bdee)
666 => GenStgExpr bndr bdee -> SDoc
668 pprStgExpr (StgLit lit) = ppr lit
671 pprStgExpr (StgApp func args)
673 4 (sep (map (ppr) args))
677 pprStgExpr (StgConApp con args)
678 = hsep [ ppr con, brackets (interppSP args)]
680 pprStgExpr (StgOpApp op args _)
681 = hsep [ pprStgOp op, brackets (interppSP args)]
683 pprStgExpr (StgLam _ bndrs body)
684 =sep [ char '\\' <+> ppr bndrs <+> ptext SLIT("->"),
689 -- special case: let v = <very specific thing>
695 -- Very special! Suspicious! (SLPJ)
698 pprStgExpr (StgLet srt (StgNonRec bndr (StgRhsClosure cc bi free_vars upd_flag args rhs))
701 (hang (hcat [ptext SLIT("let { "), ppr bndr, ptext SLIT(" = "),
704 ptext SLIT(" ["), ifPprDebug (interppSP free_vars), ptext SLIT("] \\"),
705 ppr upd_flag, ptext SLIT(" ["),
706 interppSP args, char ']'])
707 8 (sep [hsep [ppr rhs, ptext SLIT("} in")]]))
711 -- special case: let ... in let ...
713 pprStgExpr (StgLet bind expr@(StgLet _ _))
715 (sep [hang (ptext SLIT("let {"))
716 2 (hsep [pprGenStgBinding bind, ptext SLIT("} in")])])
720 pprStgExpr (StgLet bind expr)
721 = sep [hang (ptext SLIT("let {")) 2 (pprGenStgBinding bind),
722 hang (ptext SLIT("} in ")) 2 (ppr expr)]
724 pprStgExpr (StgLetNoEscape lvs_whole lvs_rhss bind expr)
725 = sep [hang (ptext SLIT("let-no-escape {"))
726 2 (pprGenStgBinding bind),
727 hang ((<>) (ptext SLIT("} in "))
730 hcat [ptext SLIT("-- lvs: ["), interppSP (uniqSetToList lvs_whole),
731 ptext SLIT("]; rhs lvs: ["), interppSP (uniqSetToList lvs_rhss),
735 pprStgExpr (StgSCC cc expr)
736 = sep [ hsep [ptext SLIT("_scc_"), ppr cc],
739 pprStgExpr (StgTick m n expr)
740 = sep [ hsep [ptext SLIT("_tick_"), pprModule m,text (show n)],
743 pprStgExpr (StgCase expr lvs_whole lvs_rhss bndr srt alt_type alts)
744 = sep [sep [ptext SLIT("case"),
745 nest 4 (hsep [pprStgExpr expr,
746 ifPprDebug (dcolon <+> ppr alt_type)]),
747 ptext SLIT("of"), ppr bndr, char '{'],
750 hcat [ptext SLIT("-- lvs: ["), interppSP (uniqSetToList lvs_whole),
751 ptext SLIT("]; rhs lvs: ["), interppSP (uniqSetToList lvs_rhss),
754 nest 2 (vcat (map pprStgAlt alts)),
757 pprStgAlt (con, params, use_mask, expr)
758 = hang (hsep [ppr con, interppSP params, ptext SLIT("->")])
761 pprStgOp (StgPrimOp op) = ppr op
762 pprStgOp (StgFCallOp op _) = ppr op
764 instance Outputable AltType where
765 ppr PolyAlt = ptext SLIT("Polymorphic")
766 ppr (UbxTupAlt tc) = ptext SLIT("UbxTup") <+> ppr tc
767 ppr (AlgAlt tc) = ptext SLIT("Alg") <+> ppr tc
768 ppr (PrimAlt tc) = ptext SLIT("Prim") <+> ppr tc
772 pprStgLVs :: Outputable occ => GenStgLiveVars occ -> SDoc
774 = getPprStyle $ \ sty ->
775 if userStyle sty || isEmptyUniqSet lvs then
778 hcat [text "{-lvs:", interpp'SP (uniqSetToList lvs), text "-}"]
782 pprStgRhs :: (Outputable bndr, Outputable bdee, Ord bdee)
783 => GenStgRhs bndr bdee -> SDoc
786 pprStgRhs (StgRhsClosure cc bi [free_var] upd_flag srt [{-no args-}] (StgApp func []))
789 brackets (ifPprDebug (ppr free_var)),
790 ptext SLIT(" \\"), ppr upd_flag, pprMaybeSRT srt, ptext SLIT(" [] "), ppr func ]
793 pprStgRhs (StgRhsClosure cc bi free_vars upd_flag srt args body)
794 = hang (hsep [if opt_SccProfilingOn then ppr cc else empty,
796 ifPprDebug (brackets (interppSP free_vars)),
797 char '\\' <> ppr upd_flag, pprMaybeSRT srt, brackets (interppSP args)])
800 pprStgRhs (StgRhsCon cc con args)
802 space, ppr con, ptext SLIT("! "), brackets (interppSP args)]
804 pprMaybeSRT (NoSRT) = empty
805 pprMaybeSRT srt = ptext SLIT("srt:") <> pprSRT srt