2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 % $Id: CgCase.lhs,v 1.43 2000/07/11 16:03:37 simonmar Exp $
6 %********************************************************
8 \section[CgCase]{Converting @StgCase@ expressions}
10 %********************************************************
13 module CgCase ( cgCase, saveVolatileVarsAndRegs, restoreCurrentCostCentre
16 #include "HsVersions.h"
18 import {-# SOURCE #-} CgExpr ( cgExpr )
24 import AbsCUtils ( mkAbstractCs, mkAbsCStmts, mkAlgAltsCSwitch,
25 getAmodeRep, nonemptyAbsC
27 import CgUpdate ( reserveSeqFrame )
28 import CgBindery ( getVolatileRegs, getArgAmodes,
29 bindNewToReg, bindNewToTemp,
31 rebindToStack, getCAddrMode,
32 getCAddrModeAndInfo, getCAddrModeIfVolatile,
33 buildContLivenessMask, nukeDeadBindings,
35 import CgCon ( bindConArgs, bindUnboxedTupleComponents )
36 import CgHeapery ( altHeapCheck, yield )
37 import CgRetConv ( dataReturnConvPrim, ctrlReturnConvAlg,
38 CtrlReturnConvention(..)
40 import CgStackery ( allocPrimStack, allocStackTop,
41 deAllocStackTop, freeStackSlots, dataStackSlots
43 import CgTailCall ( tailCallFun )
44 import CgUsages ( getSpRelOffset, getRealSp )
45 import CLabel ( CLabel, mkVecTblLabel, mkReturnPtLabel,
46 mkDefaultLabel, mkAltLabel, mkReturnInfoLabel,
47 mkErrorStdEntryLabel, mkClosureTblLabel
49 import ClosureInfo ( mkLFArgument )
50 import CmdLineOpts ( opt_SccProfilingOn, opt_GranMacros )
51 import Id ( Id, idPrimRep, isDeadBinder )
52 import DataCon ( DataCon, dataConTag, fIRST_TAG, ConTag,
54 import VarSet ( varSetElems )
55 import Literal ( Literal )
56 import PrimOp ( primOpOutOfLine, PrimOp(..) )
57 import PrimRep ( getPrimRepSize, retPrimRepSize, PrimRep(..)
59 import TyCon ( TyCon, isEnumerationTyCon, isUnboxedTupleTyCon,
60 isNewTyCon, isAlgTyCon, isFunTyCon, isPrimTyCon,
62 import Type ( Type, typePrimRep, splitAlgTyConApp,
63 splitTyConApp_maybe, repType )
64 import Unique ( Unique, Uniquable(..), mkPseudoUnique1 )
65 import Maybes ( maybeToBool )
72 = GCMayHappen -- The scrutinee may involve GC, so everything must be
73 -- tidy before the code for the scrutinee.
75 | NoGC -- The scrutinee is a primitive value, or a call to a
76 -- primitive op which does no GC. Hence the case can
77 -- be done inline, without tidying up first.
80 It is quite interesting to decide whether to put a heap-check
81 at the start of each alternative. Of course we certainly have
82 to do so if the case forces an evaluation, or if there is a primitive
83 op which can trigger GC.
85 A more interesting situation is this:
92 default -> !C!; ...C...
95 where \tr{!x!} indicates a possible heap-check point. The heap checks
96 in the alternatives {\em can} be omitted, in which case the topmost
97 heapcheck will take their worst case into account.
99 In favour of omitting \tr{!B!}, \tr{!C!}:
101 - {\em May} save a heap overflow test,
102 if ...A... allocates anything. The other advantage
103 of this is that we can use relative addressing
104 from a single Hp to get at all the closures so allocated.
106 - No need to save volatile vars etc across the case
110 - May do more allocation than reqd. This sometimes bites us
111 badly. For example, nfib (ha!) allocates about 30\% more space if the
112 worst-casing is done, because many many calls to nfib are leaf calls
113 which don't need to allocate anything.
115 This never hurts us if there is only one alternative.
127 Special case #1: PrimOps returning enumeration types.
129 For enumeration types, we invent a temporary (builtin-unique 1) to
130 hold the tag, and cross our fingers that this doesn't clash with
131 anything else. Builtin-unique 0 is used for a similar reason when
132 compiling enumerated-type primops in CgExpr.lhs. We can't use the
133 unique from the case binder, because this is used to hold the actual
134 closure (when the case binder is live, that is).
136 There is an extra special case for
141 which generates no code for the primop, unless x is used in the
142 alternatives (in which case we lookup the tag in the relevant closure
143 table to get the closure).
145 Being a bit short of uniques for temporary variables here, we use
146 mkPseudoUnique1 to generate a temporary for the tag. We can't use
147 mkBuiltinUnique, because that occasionally clashes with some
148 temporaries generated for _ccall_GC, amongst others (see CgExpr.lhs).
151 cgCase (StgPrimApp op args res_ty)
152 live_in_whole_case live_in_alts bndr srt (StgAlgAlts ty alts deflt)
153 | isEnumerationTyCon tycon
154 = getArgAmodes args `thenFC` \ arg_amodes ->
156 let tag_amode = case op of
157 TagToEnumOp -> only arg_amodes
158 _ -> CTemp (mkPseudoUnique1{-see above-} 1) IntRep
160 closure = CVal (CIndex (CLbl (mkClosureTblLabel tycon) PtrRep) tag_amode PtrRep) PtrRep
164 TagToEnumOp -> nopC; -- no code!
166 _ -> -- Perform the operation
167 getVolatileRegs live_in_alts `thenFC` \ vol_regs ->
169 absC (COpStmt [tag_amode] op
170 arg_amodes -- note: no liveness arg
174 -- bind the default binder if necessary
175 -- The deadness info is set by StgVarInfo
176 (if (isDeadBinder bndr)
178 else bindNewToTemp bndr `thenFC` \ bndr_amode ->
179 absC (CAssign bndr_amode closure))
183 cgAlgAlts NoGC uniq Nothing{-cc_slot-} False{-no semi-tagging-}
184 False{-not poly case-} alts deflt
185 False{-don't emit yield-} `thenFC` \ (tagged_alts, deflt_c) ->
188 absC (mkAlgAltsCSwitch tag_amode tagged_alts deflt_c)
191 (Just (tycon,_)) = splitTyConApp_maybe res_ty
192 uniq = getUnique bndr
195 Special case #2: inline PrimOps.
198 cgCase (StgPrimApp op args res_ty)
199 live_in_whole_case live_in_alts bndr srt alts
200 | not (primOpOutOfLine op)
202 -- Get amodes for the arguments and results
203 getArgAmodes args `thenFC` \ arg_amodes ->
205 result_amodes = getPrimAppResultAmodes (getUnique bndr) alts
207 -- Perform the operation
208 getVolatileRegs live_in_alts `thenFC` \ vol_regs ->
210 absC (COpStmt result_amodes op
211 arg_amodes -- note: no liveness arg
214 -- Scrutinise the result
215 cgInlineAlts bndr alts
218 TODO: Case-of-case of primop can probably be done inline too (but
219 maybe better to translate it out beforehand). See
220 ghc/lib/misc/PackedString.lhs for examples where this crops up (with
223 Another special case: scrutinising a primitive-typed variable. No
224 evaluation required. We don't save volatile variables, nor do we do a
225 heap-check in the alternatives. Instead, the heap usage of the
226 alternatives is worst-cased and passed upstream. This can result in
227 allocating more heap than strictly necessary, but it will sometimes
228 eliminate a heap check altogether.
231 cgCase (StgApp v []) live_in_whole_case live_in_alts bndr srt
232 (StgPrimAlts ty alts deflt)
235 getCAddrMode v `thenFC` \amode ->
238 Careful! we can't just bind the default binder to the same thing
239 as the scrutinee, since it might be a stack location, and having
240 two bindings pointing at the same stack locn doesn't work (it
241 confuses nukeDeadBindings). Hence, use a new temp.
243 bindNewToTemp bndr `thenFC` \deflt_amode ->
244 absC (CAssign deflt_amode amode) `thenC`
246 cgPrimAlts NoGC amode alts deflt []
249 Special case: scrutinising a non-primitive variable.
250 This can be done a little better than the general case, because
251 we can reuse/trim the stack slot holding the variable (if it is in one).
254 cgCase (StgApp fun args)
255 live_in_whole_case live_in_alts bndr srt alts@(StgAlgAlts ty _ _)
257 getCAddrModeAndInfo fun `thenFC` \ (fun_amode, lf_info) ->
258 getArgAmodes args `thenFC` \ arg_amodes ->
260 -- Squish the environment
261 nukeDeadBindings live_in_alts `thenC`
262 saveVolatileVarsAndRegs live_in_alts
263 `thenFC` \ (save_assts, alts_eob_info, maybe_cc_slot) ->
265 allocStackTop retPrimRepSize `thenFC` \_ ->
267 forkEval alts_eob_info nopC (
268 deAllocStackTop retPrimRepSize `thenFC` \_ ->
269 cgEvalAlts maybe_cc_slot bndr srt alts)
270 `thenFC` \ scrut_eob_info ->
272 let real_scrut_eob_info =
274 then reserveSeqFrame scrut_eob_info
278 setEndOfBlockInfo real_scrut_eob_info (
279 tailCallFun fun fun_amode lf_info arg_amodes save_assts
283 not_con_ty = case (getScrutineeTyCon ty) of
288 Note about return addresses: we *always* push a return address, even
289 if because of an optimisation we end up jumping direct to the return
290 code (not through the address itself). The alternatives always assume
291 that the return address is on the stack. The return address is
292 required in case the alternative performs a heap check, since it
293 encodes the liveness of the slots in the activation record.
295 On entry to the case alternative, we can re-use the slot containing
296 the return address immediately after the heap check. That's what the
297 deAllocStackTop call is doing above.
299 Finally, here is the general case.
302 cgCase expr live_in_whole_case live_in_alts bndr srt alts
303 = -- Figure out what volatile variables to save
304 nukeDeadBindings live_in_whole_case `thenC`
306 saveVolatileVarsAndRegs live_in_alts
307 `thenFC` \ (save_assts, alts_eob_info, maybe_cc_slot) ->
309 -- Save those variables right now!
310 absC save_assts `thenC`
312 -- generate code for the alts
313 forkEval alts_eob_info
315 nukeDeadBindings live_in_alts `thenC`
316 allocStackTop retPrimRepSize -- space for retn address
319 (deAllocStackTop retPrimRepSize `thenFC` \_ ->
320 cgEvalAlts maybe_cc_slot bndr srt alts) `thenFC` \ scrut_eob_info ->
322 let real_scrut_eob_info =
324 then reserveSeqFrame scrut_eob_info
328 setEndOfBlockInfo real_scrut_eob_info (cgExpr expr)
331 not_con_ty = case (getScrutineeTyCon (alts_ty alts)) of
336 There's a lot of machinery going on behind the scenes to manage the
337 stack pointer here. forkEval takes the virtual Sp and free list from
338 the first argument, and turns that into the *real* Sp for the second
339 argument. It also uses this virtual Sp as the args-Sp in the EOB info
340 returned, so that the scrutinee will trim the real Sp back to the
341 right place before doing whatever it does.
342 --SDM (who just spent an hour figuring this out, and didn't want to
345 Why don't we push the return address just before evaluating the
346 scrutinee? Because the slot reserved for the return address might
347 contain something useful, so we wait until performing a tail call or
348 return before pushing the return address (see
349 CgTailCall.pushReturnAddress).
351 This also means that the environment doesn't need to know about the
352 free stack slot for the return address (for generating bitmaps),
353 because we don't reserve it until just before the eval.
355 TODO!! Problem: however, we have to save the current cost centre
356 stack somewhere, because at the eval point the current CCS might be
357 different. So we pick a free stack slot and save CCCS in it. The
358 problem with this is that this slot isn't recorded as free/unboxed in
359 the environment, so a case expression in the scrutinee will have the
360 wrong bitmap attached. Fortunately we don't ever seem to see
361 case-of-case at the back end. One solution might be to shift the
362 saved CCS to the correct place in the activation record just before
366 (one consequence of the above is that activation records on the stack
367 don't follow the layout of closures when we're profiling. The CCS
368 could be anywhere within the record).
371 alts_ty (StgAlgAlts ty _ _) = ty
372 alts_ty (StgPrimAlts ty _ _) = ty
375 %************************************************************************
377 \subsection[CgCase-primops]{Primitive applications}
379 %************************************************************************
381 Get result amodes for a primitive operation, in the case wher GC can't happen.
382 The amodes are returned in canonical order, ready for the prim-op!
384 Alg case: temporaries named as in the alternatives,
385 plus (CTemp u) for the tag (if needed)
388 This is all disgusting, because these amodes must be consistent with those
389 invented by CgAlgAlts.
392 getPrimAppResultAmodes
397 getPrimAppResultAmodes uniq (StgAlgAlts ty alts some_default)
399 | isUnboxedTupleTyCon tycon =
401 [(con, args, use_mask, rhs)] ->
402 [ CTemp (getUnique arg) (idPrimRep arg) | arg <- args ]
403 _ -> panic "getPrimAppResultAmodes: case of unboxed tuple has multiple branches"
405 | otherwise = panic ("getPrimAppResultAmodes: case of primop has strange type: " ++ showSDoc (ppr ty))
407 where (tycon, _, _) = splitAlgTyConApp ty
409 -- The situation is simpler for primitive results, because there is only
412 getPrimAppResultAmodes uniq (StgPrimAlts ty _ _)
413 = [CTemp uniq (typePrimRep ty)]
417 %************************************************************************
419 \subsection[CgCase-alts]{Alternatives}
421 %************************************************************************
423 @cgEvalAlts@ returns an addressing mode for a continuation for the
424 alternatives of a @case@, used in a context when there
425 is some evaluation to be done.
428 cgEvalAlts :: Maybe VirtualSpOffset -- Offset of cost-centre to be restored, if any
430 -> SRT -- SRT for the continuation
432 -> FCode Sequel -- Any addr modes inside are guaranteed
433 -- to be a label so that we can duplicate it
434 -- without risk of duplicating code
436 cgEvalAlts cc_slot bndr srt alts
438 let uniq = getUnique bndr in
440 buildContLivenessMask uniq `thenFC` \ liveness_mask ->
444 -- algebraic alts ...
445 (StgAlgAlts ty alts deflt) ->
447 -- bind the default binder (it covers all the alternatives)
448 bindNewToReg bndr node mkLFArgument `thenC`
450 -- Generate sequel info for use downstream
451 -- At the moment, we only do it if the type is vector-returnable.
452 -- Reason: if not, then it costs extra to label the
453 -- alternatives, because we'd get return code like:
455 -- switch TagReg { 0 : JMP(alt_1); 1 : JMP(alt_2) ..etc }
457 -- which is worse than having the alt code in the switch statement
459 let tycon_info = getScrutineeTyCon ty
460 is_alg = maybeToBool tycon_info
461 Just spec_tycon = tycon_info
464 -- deal with the unboxed tuple case
465 if is_alg && isUnboxedTupleTyCon spec_tycon then
467 [alt] -> let lbl = mkReturnInfoLabel uniq in
468 cgUnboxedTupleAlt uniq cc_slot True alt
470 getSRTLabel `thenFC` \srt_label ->
471 absC (CRetDirect uniq abs_c (srt_label, srt)
472 liveness_mask) `thenC`
473 returnFC (CaseAlts (CLbl lbl RetRep) Nothing)
474 _ -> panic "cgEvalAlts: dodgy case of unboxed tuple type"
476 -- normal algebraic (or polymorphic) case alternatives
478 ret_conv | is_alg = ctrlReturnConvAlg spec_tycon
479 | otherwise = UnvectoredReturn 0
481 use_labelled_alts = case ret_conv of
482 VectoredReturn _ -> True
486 = if use_labelled_alts then
487 cgSemiTaggedAlts bndr alts deflt -- Just <something>
489 Nothing -- no semi-tagging info
492 cgAlgAlts GCMayHappen uniq cc_slot use_labelled_alts (not is_alg)
493 alts deflt True `thenFC` \ (tagged_alt_absCs, deflt_absC) ->
495 mkReturnVector uniq tagged_alt_absCs deflt_absC srt liveness_mask
496 ret_conv `thenFC` \ return_vec ->
498 returnFC (CaseAlts return_vec semi_tagged_stuff)
501 (StgPrimAlts ty alts deflt) ->
503 -- Restore the cost centre
504 restoreCurrentCostCentre cc_slot `thenFC` \ cc_restore ->
506 -- Generate the switch
507 getAbsC (cgPrimEvalAlts bndr ty alts deflt) `thenFC` \ abs_c ->
509 -- Generate the labelled block, starting with restore-cost-centre
510 getSRTLabel `thenFC` \srt_label ->
511 absC (CRetDirect uniq (cc_restore `mkAbsCStmts` abs_c)
512 (srt_label,srt) liveness_mask) `thenC`
514 -- Return an amode for the block
515 returnFC (CaseAlts (CLbl (mkReturnInfoLabel uniq) RetRep) Nothing)
525 HWL comment on {\em GrAnSim\/} (adding GRAN_YIELDs for context switch): If
526 we do an inlining of the case no separate functions for returning are
527 created, so we don't have to generate a GRAN_YIELD in that case. This info
528 must be propagated to cgAlgAltRhs (where the GRAN_YIELD macro might be
529 emitted). Hence, the new Bool arg to cgAlgAltRhs.
531 First case: primitive op returns an unboxed tuple.
534 cgInlineAlts bndr (StgAlgAlts ty [alt@(con,args,use_mask,rhs)] StgNoDefault)
535 | isUnboxedTupleCon con
536 = -- no heap check, no yield, just get in there and do it.
537 mapFCs bindNewToTemp args `thenFC` \ _ ->
541 = panic "cgInlineAlts: single alternative, not an unboxed tuple"
544 Third (real) case: primitive result type.
547 cgInlineAlts bndr (StgPrimAlts ty alts deflt)
548 = cgPrimInlineAlts bndr ty alts deflt
551 %************************************************************************
553 \subsection[CgCase-alg-alts]{Algebraic alternatives}
555 %************************************************************************
557 In @cgAlgAlts@, none of the binders in the alternatives are
558 assumed to be yet bound.
560 HWL comment on {\em GrAnSim\/} (adding GRAN_YIELDs for context switch): The
561 last arg of cgAlgAlts indicates if we want a context switch at the
562 beginning of each alternative. Normally we want that. The only exception
563 are inlined alternatives.
568 -> Maybe VirtualSpOffset
569 -> Bool -- True <=> branches must be labelled
570 -> Bool -- True <=> polymorphic case
571 -> [(DataCon, [Id], [Bool], StgExpr)] -- The alternatives
572 -> StgCaseDefault -- The default
573 -> Bool -- Context switch at alts?
574 -> FCode ([(ConTag, AbstractC)], -- The branches
575 AbstractC -- The default case
578 cgAlgAlts gc_flag uniq restore_cc must_label_branches is_fun alts deflt
579 emit_yield{-should a yield macro be emitted?-}
581 = forkAlts (map (cgAlgAlt gc_flag uniq restore_cc must_label_branches emit_yield) alts)
582 (cgAlgDefault gc_flag is_fun uniq restore_cc must_label_branches deflt emit_yield)
586 cgAlgDefault :: GCFlag
587 -> Bool -- could be a function-typed result?
588 -> Unique -> Maybe VirtualSpOffset -> Bool -- turgid state...
589 -> StgCaseDefault -- input
591 -> FCode AbstractC -- output
593 cgAlgDefault gc_flag is_fun uniq cc_slot must_label_branch StgNoDefault _
596 cgAlgDefault gc_flag is_fun uniq cc_slot must_label_branch
598 emit_yield{-should a yield macro be emitted?-}
600 = -- We have arranged that Node points to the thing
601 restoreCurrentCostCentre cc_slot `thenFC` \restore_cc ->
602 getAbsC (absC restore_cc `thenC`
603 -- HWL: maybe need yield here
605 -- then yield [node] True
606 -- else absC AbsCNop) `thenC`
607 possibleHeapCheck gc_flag is_fun [node] [] Nothing (cgExpr rhs)
608 -- Node is live, but doesn't need to point at the thing itself;
609 -- it's ok for Node to point to an indirection or FETCH_ME
610 -- Hence no need to re-enter Node.
611 ) `thenFC` \ abs_c ->
614 final_abs_c | must_label_branch = CCodeBlock lbl abs_c
619 lbl = mkDefaultLabel uniq
621 -- HWL comment on GrAnSim: GRAN_YIELDs needed; emitted in cgAlgAltRhs
624 -> Unique -> Maybe VirtualSpOffset -> Bool -- turgid state
625 -> Bool -- Context switch at alts?
626 -> (DataCon, [Id], [Bool], StgExpr)
627 -> FCode (ConTag, AbstractC)
629 cgAlgAlt gc_flag uniq cc_slot must_label_branch
630 emit_yield{-should a yield macro be emitted?-}
631 (con, args, use_mask, rhs)
633 restoreCurrentCostCentre cc_slot `thenFC` \restore_cc ->
634 getAbsC (absC restore_cc `thenC`
635 -- HWL: maybe need yield here
637 -- then yield [node] True -- XXX live regs wrong
638 -- else absC AbsCNop) `thenC`
640 NoGC -> mapFCs bindNewToTemp args `thenFC` \_ -> nopC
641 GCMayHappen -> bindConArgs con args
643 possibleHeapCheck gc_flag False [node] [] Nothing (
645 ) `thenFC` \ abs_c ->
647 final_abs_c | must_label_branch = CCodeBlock lbl abs_c
650 returnFC (tag, final_abs_c)
653 lbl = mkAltLabel uniq tag
656 :: Unique -- unique for label of the alternative
657 -> Maybe VirtualSpOffset -- Restore cost centre
658 -> Bool -- ctxt switch
659 -> (DataCon, [Id], [Bool], StgExpr) -- alternative
662 cgUnboxedTupleAlt lbl cc_slot emit_yield (con,args,use_mask,rhs)
664 bindUnboxedTupleComponents args
665 `thenFC` \ (live_regs,tags,stack_res) ->
667 restoreCurrentCostCentre cc_slot `thenFC` \restore_cc ->
668 absC restore_cc `thenC`
670 -- HWL: maybe need yield here
672 -- then yield live_regs True -- XXX live regs wrong?
673 -- else absC AbsCNop) `thenC`
675 -- ToDo: could maybe use Nothing here if stack_res is False
676 -- since the heap-check can just return to the top of the
681 -- free up stack slots containing tags,
682 freeStackSlots (map fst tags) `thenC`
684 -- generate a heap check if necessary
685 possibleHeapCheck GCMayHappen False live_regs tags ret_addr (
687 -- and finally the code for the alternative
692 %************************************************************************
694 \subsection[CgCase-semi-tagged-alts]{The code to deal with sem-tagging}
696 %************************************************************************
698 Turgid-but-non-monadic code to conjure up the required info from
699 algebraic case alternatives for semi-tagging.
702 cgSemiTaggedAlts :: Id
703 -> [(DataCon, [Id], [Bool], StgExpr)]
704 -> GenStgCaseDefault Id Id
707 cgSemiTaggedAlts binder alts deflt
708 = Just (map st_alt alts, st_deflt deflt)
710 uniq = getUnique binder
712 st_deflt StgNoDefault = Nothing
714 st_deflt (StgBindDefault _)
716 (CCallProfCtrMacro SLIT("RET_SEMI_BY_DEFAULT") [], -- ToDo: monadise?
720 st_alt (con, args, use_mask, _)
721 = -- Ha! Nothing to do; Node already points to the thing
723 (CCallProfCtrMacro SLIT("RET_SEMI_IN_HEAP") -- ToDo: monadise?
724 [mkIntCLit (length args)], -- how big the thing in the heap is
728 con_tag = dataConTag con
729 join_label = mkAltLabel uniq con_tag
732 %************************************************************************
734 \subsection[CgCase-prim-alts]{Primitive alternatives}
736 %************************************************************************
738 @cgPrimEvalAlts@ and @cgPrimInlineAlts@ generate suitable @CSwitch@es
739 for dealing with the alternatives of a primitive @case@, given an
740 addressing mode for the thing to scrutinise. It also keeps track of
741 the maximum stack depth encountered down any branch.
743 As usual, no binders in the alternatives are yet bound.
746 cgPrimInlineAlts bndr ty alts deflt
747 = cgPrimAltsWithDefault bndr NoGC (CTemp uniq kind) alts deflt []
749 uniq = getUnique bndr
750 kind = typePrimRep ty
752 cgPrimEvalAlts bndr ty alts deflt
753 = cgPrimAltsWithDefault bndr GCMayHappen (CReg reg) alts deflt [reg]
755 reg = WARN( case kind of { PtrRep -> True; other -> False }, text "cgPrimEE" <+> ppr bndr <+> ppr ty )
756 dataReturnConvPrim kind
757 kind = typePrimRep ty
759 cgPrimAltsWithDefault bndr gc_flag scrutinee alts deflt regs
760 = -- first bind the default if necessary
761 bindNewPrimToAmode bndr scrutinee `thenC`
762 cgPrimAlts gc_flag scrutinee alts deflt regs
764 cgPrimAlts gc_flag scrutinee alts deflt regs
765 = forkAlts (map (cgPrimAlt gc_flag regs) alts)
766 (cgPrimDefault gc_flag regs deflt)
767 `thenFC` \ (alt_absCs, deflt_absC) ->
769 absC (CSwitch scrutinee alt_absCs deflt_absC)
770 -- CSwitch does sensible things with one or zero alternatives
774 -> [MagicId] -- live registers
775 -> (Literal, StgExpr) -- The alternative
776 -> FCode (Literal, AbstractC) -- Its compiled form
778 cgPrimAlt gc_flag regs (lit, rhs)
779 = getAbsC rhs_code `thenFC` \ absC ->
782 rhs_code = possibleHeapCheck gc_flag False regs [] Nothing (cgExpr rhs)
784 cgPrimDefault :: GCFlag
785 -> [MagicId] -- live registers
789 cgPrimDefault gc_flag regs StgNoDefault
790 = panic "cgPrimDefault: No default in prim case"
792 cgPrimDefault gc_flag regs (StgBindDefault rhs)
793 = getAbsC (possibleHeapCheck gc_flag False regs [] Nothing (cgExpr rhs))
797 %************************************************************************
799 \subsection[CgCase-tidy]{Code for tidying up prior to an eval}
801 %************************************************************************
804 saveVolatileVarsAndRegs
805 :: StgLiveVars -- Vars which should be made safe
806 -> FCode (AbstractC, -- Assignments to do the saves
807 EndOfBlockInfo, -- sequel for the alts
808 Maybe VirtualSpOffset) -- Slot for current cost centre
811 saveVolatileVarsAndRegs vars
812 = saveVolatileVars vars `thenFC` \ var_saves ->
813 saveCurrentCostCentre `thenFC` \ (maybe_cc_slot, cc_save) ->
814 getEndOfBlockInfo `thenFC` \ eob_info ->
815 returnFC (mkAbstractCs [var_saves, cc_save],
820 saveVolatileVars :: StgLiveVars -- Vars which should be made safe
821 -> FCode AbstractC -- Assignments to to the saves
823 saveVolatileVars vars
824 = save_em (varSetElems vars)
826 save_em [] = returnFC AbsCNop
829 = getCAddrModeIfVolatile var `thenFC` \ v ->
831 Nothing -> save_em vars -- Non-volatile, so carry on
834 Just vol_amode -> -- Aha! It's volatile
835 save_var var vol_amode `thenFC` \ abs_c ->
836 save_em vars `thenFC` \ abs_cs ->
837 returnFC (abs_c `mkAbsCStmts` abs_cs)
839 save_var var vol_amode
840 = allocPrimStack (getPrimRepSize kind) `thenFC` \ slot ->
841 rebindToStack var slot `thenC`
842 getSpRelOffset slot `thenFC` \ sp_rel ->
843 returnFC (CAssign (CVal sp_rel kind) vol_amode)
845 kind = getAmodeRep vol_amode
848 ---------------------------------------------------------------------------
850 When we save the current cost centre (which is done for lexical
851 scoping), we allocate a free stack location, and return (a)~the
852 virtual offset of the location, to pass on to the alternatives, and
853 (b)~the assignment to do the save (just as for @saveVolatileVars@).
856 saveCurrentCostCentre ::
857 FCode (Maybe VirtualSpOffset, -- Where we decide to store it
858 AbstractC) -- Assignment to save it
860 saveCurrentCostCentre
861 = if not opt_SccProfilingOn then
862 returnFC (Nothing, AbsCNop)
864 allocPrimStack (getPrimRepSize CostCentreRep) `thenFC` \ slot ->
865 dataStackSlots [slot] `thenC`
866 getSpRelOffset slot `thenFC` \ sp_rel ->
868 CAssign (CVal sp_rel CostCentreRep) (CReg CurCostCentre))
870 restoreCurrentCostCentre :: Maybe VirtualSpOffset -> FCode AbstractC
871 restoreCurrentCostCentre Nothing = returnFC AbsCNop
872 restoreCurrentCostCentre (Just slot)
873 = getSpRelOffset slot `thenFC` \ sp_rel ->
874 freeStackSlots [slot] `thenC`
875 returnFC (CCallProfCCMacro SLIT("RESTORE_CCCS") [CVal sp_rel CostCentreRep])
876 -- we use the RESTORE_CCCS macro, rather than just
877 -- assigning into CurCostCentre, in case RESTORE_CCC
878 -- has some sanity-checking in it.
881 %************************************************************************
883 \subsection[CgCase-return-vec]{Building a return vector}
885 %************************************************************************
887 Build a return vector, and return a suitable label addressing
891 mkReturnVector :: Unique
892 -> [(ConTag, AbstractC)] -- Branch codes
893 -> AbstractC -- Default case
894 -> SRT -- continuation's SRT
895 -> Liveness -- stack liveness
896 -> CtrlReturnConvention
899 mkReturnVector uniq tagged_alt_absCs deflt_absC srt liveness ret_conv
900 = getSRTLabel `thenFC` \srt_label ->
902 srt_info = (srt_label, srt)
904 (return_vec_amode, vtbl_body) = case ret_conv of {
906 -- might be a polymorphic case...
907 UnvectoredReturn 0 ->
908 ASSERT(null tagged_alt_absCs)
909 (CLbl ret_label RetRep,
910 absC (CRetDirect uniq deflt_absC (srt_label, srt) liveness));
912 UnvectoredReturn n ->
913 -- find the tag explicitly rather than using tag_reg for now.
914 -- on architectures with lots of regs the tag will be loaded
915 -- into tag_reg by the code doing the returning.
917 tag = CMacroExpr WordRep GET_TAG [CVal (nodeRel 0) DataPtrRep]
919 (CLbl ret_label RetRep,
920 absC (CRetDirect uniq
921 (mkAlgAltsCSwitch tag tagged_alt_absCs deflt_absC)
925 VectoredReturn table_size ->
927 (vector_table, alts_absC) =
928 unzip (map mk_vector_entry [fIRST_TAG .. (table_size+fIRST_TAG-1)])
930 ret_vector = CRetVector vtbl_label
932 (srt_label, srt) liveness
934 (CLbl vtbl_label DataPtrRep,
935 -- alts come first, because we don't want to declare all the symbols
936 absC (mkAbstractCs (mkAbstractCs alts_absC : [deflt_absC,ret_vector]))
941 returnFC return_vec_amode
945 vtbl_label = mkVecTblLabel uniq
946 ret_label = mkReturnInfoLabel uniq
949 case nonemptyAbsC deflt_absC of
950 -- the simplifier might have eliminated a case
951 Nothing -> CLbl mkErrorStdEntryLabel CodePtrRep
952 Just absC@(CCodeBlock lbl _) -> CLbl lbl CodePtrRep
954 mk_vector_entry :: ConTag -> (CAddrMode, AbstractC)
956 = case [ absC | (t, absC) <- tagged_alt_absCs, t == tag ] of
957 [] -> (deflt_lbl, AbsCNop)
958 [absC@(CCodeBlock lbl _)] -> (CLbl lbl CodePtrRep,absC)
959 _ -> panic "mkReturnVector: too many"
962 %************************************************************************
964 \subsection[CgCase-utils]{Utilities for handling case expressions}
966 %************************************************************************
968 @possibleHeapCheck@ tests a flag passed in to decide whether to do a
969 heap check or not. These heap checks are always in a case
970 alternative, so we use altHeapCheck.
975 -> Bool -- True <=> algebraic case
976 -> [MagicId] -- live registers
977 -> [(VirtualSpOffset,Int)] -- stack slots to tag
978 -> Maybe Unique -- return address unique
979 -> Code -- continuation
982 possibleHeapCheck GCMayHappen is_alg regs tags lbl code
983 = altHeapCheck is_alg regs tags AbsCNop lbl code
984 possibleHeapCheck NoGC _ _ tags lbl code
989 getScrutineeTyCon :: Type -> Maybe TyCon
990 getScrutineeTyCon ty =
991 case splitTyConApp_maybe (repType ty) of
994 if isFunTyCon tc then Nothing else -- not interested in funs
995 if isPrimTyCon tc then Just tc else -- return primitive tycons
996 -- otherwise (algebraic tycons) check the no. of constructors