2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 % $Id: CgCase.lhs,v 1.21 1998/12/22 18:03:27 simonm Exp $
6 %********************************************************
8 \section[CgCase]{Converting @StgCase@ expressions}
10 %********************************************************
13 module CgCase ( cgCase, saveVolatileVarsAndRegs, restoreCurrentCostCentre,
14 splitTyConAppThroughNewTypes ) where
16 #include "HsVersions.h"
18 import {-# SOURCE #-} CgExpr ( cgExpr )
24 import AbsCUtils ( mkAbstractCs, mkAbsCStmts, mkAlgAltsCSwitch,
25 getAmodeRep, nonemptyAbsC
27 import CoreSyn ( isDeadBinder )
28 import CgUpdate ( reserveSeqFrame )
29 import CgBindery ( getVolatileRegs, getArgAmodes,
30 bindNewToReg, bindNewToTemp,
32 rebindToStack, getCAddrMode,
33 getCAddrModeAndInfo, getCAddrModeIfVolatile,
34 buildContLivenessMask, nukeDeadBindings
36 import CgCon ( bindConArgs, bindUnboxedTupleComponents )
37 import CgHeapery ( altHeapCheck, yield )
38 import CgRetConv ( dataReturnConvPrim, ctrlReturnConvAlg,
39 CtrlReturnConvention(..)
41 import CgStackery ( allocPrimStack, allocStackTop,
42 deAllocStackTop, freeStackSlots
44 import CgTailCall ( tailCallFun )
45 import CgUsages ( getSpRelOffset, getRealSp )
46 import CLabel ( CLabel, mkVecTblLabel, mkReturnPtLabel,
47 mkDefaultLabel, mkAltLabel, mkReturnInfoLabel,
48 mkErrorStdEntryLabel, mkClosureTblLabel
50 import ClosureInfo ( mkLFArgument )
51 import CmdLineOpts ( opt_SccProfilingOn, opt_GranMacros )
52 import CostCentre ( CostCentre )
53 import Id ( Id, idPrimRep )
54 import DataCon ( DataCon, dataConTag, fIRST_TAG, ConTag,
55 isUnboxedTupleCon, dataConType )
56 import VarSet ( varSetElems )
57 import Const ( Con(..), Literal )
58 import PrimOp ( primOpOutOfLine, PrimOp(..) )
59 import PrimRep ( getPrimRepSize, retPrimRepSize, PrimRep(..)
61 import TyCon ( TyCon, isEnumerationTyCon, isUnboxedTupleTyCon,
62 isNewTyCon, isAlgTyCon, isFunTyCon, isPrimTyCon,
63 tyConDataCons, tyConFamilySize )
64 import Type ( Type, typePrimRep, splitAlgTyConApp, splitTyConApp_maybe,
65 splitFunTys, applyTys )
66 import Unique ( Unique, Uniquable(..) )
67 import Maybes ( maybeToBool )
73 = GCMayHappen -- The scrutinee may involve GC, so everything must be
74 -- tidy before the code for the scrutinee.
76 | NoGC -- The scrutinee is a primitive value, or a call to a
77 -- primitive op which does no GC. Hence the case can
78 -- be done inline, without tidying up first.
81 It is quite interesting to decide whether to put a heap-check
82 at the start of each alternative. Of course we certainly have
83 to do so if the case forces an evaluation, or if there is a primitive
84 op which can trigger GC.
86 A more interesting situation is this:
93 default -> !C!; ...C...
96 where \tr{!x!} indicates a possible heap-check point. The heap checks
97 in the alternatives {\em can} be omitted, in which case the topmost
98 heapcheck will take their worst case into account.
100 In favour of omitting \tr{!B!}, \tr{!C!}:
102 - {\em May} save a heap overflow test,
103 if ...A... allocates anything. The other advantage
104 of this is that we can use relative addressing
105 from a single Hp to get at all the closures so allocated.
107 - No need to save volatile vars etc across the case
111 - May do more allocation than reqd. This sometimes bites us
112 badly. For example, nfib (ha!) allocates about 30\% more space if the
113 worst-casing is done, because many many calls to nfib are leaf calls
114 which don't need to allocate anything.
116 This never hurts us if there is only one alternative.
119 *** NOT YET DONE *** The difficulty is that \tr{!B!}, \tr{!C!} need
120 to take account of what is live, and that includes all live volatile
121 variables, even if they also have stable analogues. Furthermore, the
122 stack pointers must be lined up properly so that GC sees tidy stacks.
123 If these things are done, then the heap checks can be done at \tr{!B!} and
124 \tr{!C!} without a full save-volatile-vars sequence.
136 Several special cases for inline primitive operations.
139 cgCase (StgCon (PrimOp op) args res_ty) live_in_whole_case live_in_alts bndr srt alts
140 | not (primOpOutOfLine op)
142 -- Get amodes for the arguments and results
143 getArgAmodes args `thenFC` \ arg_amodes ->
145 result_amodes = getPrimAppResultAmodes (getUnique bndr) alts
147 -- Perform the operation
148 getVolatileRegs live_in_alts `thenFC` \ vol_regs ->
150 absC (COpStmt result_amodes op
151 arg_amodes -- note: no liveness arg
154 -- Scrutinise the result
155 cgInlineAlts bndr alts
158 TODO: Case-of-case of primop can probably be done inline too (but
159 maybe better to translate it out beforehand). See
160 ghc/lib/misc/PackedString.lhs for examples where this crops up (with
163 Another special case: scrutinising a primitive-typed variable. No
164 evaluation required. We don't save volatile variables, nor do we do a
165 heap-check in the alternatives. Instead, the heap usage of the
166 alternatives is worst-cased and passed upstream. This can result in
167 allocating more heap than strictly necessary, but it will sometimes
168 eliminate a heap check altogether.
171 cgCase (StgApp v []) live_in_whole_case live_in_alts bndr srt
172 (StgPrimAlts ty alts deflt)
175 getCAddrMode v `thenFC` \amode ->
178 Careful! we can't just bind the default binder to the same thing
179 as the scrutinee, since it might be a stack location, and having
180 two bindings pointing at the same stack locn doesn't work (it
181 confuses nukeDeadBindings). Hence, use a new temp.
183 (if (isDeadBinder bndr)
185 else bindNewToTemp bndr `thenFC` \deflt_amode ->
186 absC (CAssign deflt_amode amode)) `thenC`
188 cgPrimAlts NoGC amode alts deflt []
191 Special case: scrutinising a non-primitive variable.
192 This can be done a little better than the general case, because
193 we can reuse/trim the stack slot holding the variable (if it is in one).
196 cgCase (StgApp fun args)
197 live_in_whole_case live_in_alts bndr srt alts@(StgAlgAlts ty _ _)
199 getCAddrModeAndInfo fun `thenFC` \ (fun_amode, lf_info) ->
200 getArgAmodes args `thenFC` \ arg_amodes ->
202 -- Squish the environment
203 nukeDeadBindings live_in_alts `thenC`
204 saveVolatileVarsAndRegs live_in_alts
205 `thenFC` \ (save_assts, alts_eob_info, maybe_cc_slot) ->
207 allocStackTop retPrimRepSize `thenFC` \_ ->
209 forkEval alts_eob_info nopC (
210 deAllocStackTop retPrimRepSize `thenFC` \_ ->
211 cgEvalAlts maybe_cc_slot bndr srt alts)
212 `thenFC` \ scrut_eob_info ->
214 let real_scrut_eob_info =
216 then reserveSeqFrame scrut_eob_info
220 setEndOfBlockInfo real_scrut_eob_info (
221 tailCallFun fun fun_amode lf_info arg_amodes save_assts
225 not_con_ty = case (getScrutineeTyCon ty) of
230 Note about return addresses: we *always* push a return address, even
231 if because of an optimisation we end up jumping direct to the return
232 code (not through the address itself). The alternatives always assume
233 that the return address is on the stack. The return address is
234 required in case the alternative performs a heap check, since it
235 encodes the liveness of the slots in the activation record.
237 On entry to the case alternative, we can re-use the slot containing
238 the return address immediately after the heap check. That's what the
239 deAllocStackTop call is doing above.
241 Finally, here is the general case.
244 cgCase expr live_in_whole_case live_in_alts bndr srt alts
245 = -- Figure out what volatile variables to save
246 nukeDeadBindings live_in_whole_case `thenC`
248 saveVolatileVarsAndRegs live_in_alts
249 `thenFC` \ (save_assts, alts_eob_info, maybe_cc_slot) ->
251 -- Save those variables right now!
252 absC save_assts `thenC`
254 -- generate code for the alts
255 forkEval alts_eob_info
257 nukeDeadBindings live_in_alts `thenC`
258 allocStackTop retPrimRepSize -- space for retn address
261 (deAllocStackTop retPrimRepSize `thenFC` \_ ->
262 cgEvalAlts maybe_cc_slot bndr srt alts) `thenFC` \ scrut_eob_info ->
264 let real_scrut_eob_info =
266 then reserveSeqFrame scrut_eob_info
270 setEndOfBlockInfo real_scrut_eob_info (cgExpr expr)
273 not_con_ty = case (getScrutineeTyCon (alts_ty alts)) of
278 There's a lot of machinery going on behind the scenes to manage the
279 stack pointer here. forkEval takes the virtual Sp and free list from
280 the first argument, and turns that into the *real* Sp for the second
281 argument. It also uses this virtual Sp as the args-Sp in the EOB info
282 returned, so that the scrutinee will trim the real Sp back to the
283 right place before doing whatever it does.
284 --SDM (who just spent an hour figuring this out, and didn't want to
287 Why don't we push the return address just before evaluating the
288 scrutinee? Because the slot reserved for the return address might
289 contain something useful, so we wait until performing a tail call or
290 return before pushing the return address (see
291 CgTailCall.pushReturnAddress).
293 This also means that the environment doesn't need to know about the
294 free stack slot for the return address (for generating bitmaps),
295 because we don't reserve it until just before the eval.
297 TODO!! Problem: however, we have to save the current cost centre
298 stack somewhere, because at the eval point the current CCS might be
299 different. So we pick a free stack slot and save CCCS in it. The
300 problem with this is that this slot isn't recorded as free/unboxed in
301 the environment, so a case expression in the scrutinee will have the
302 wrong bitmap attached. Fortunately we don't ever seem to see
303 case-of-case at the back end. One solution might be to shift the
304 saved CCS to the correct place in the activation record just before
308 (one consequence of the above is that activation records on the stack
309 don't follow the layout of closures when we're profiling. The CCS
310 could be anywhere within the record).
313 alts_ty (StgAlgAlts ty _ _) = ty
314 alts_ty (StgPrimAlts ty _ _) = ty
317 %************************************************************************
319 \subsection[CgCase-primops]{Primitive applications}
321 %************************************************************************
323 Get result amodes for a primitive operation, in the case wher GC can't happen.
324 The amodes are returned in canonical order, ready for the prim-op!
326 Alg case: temporaries named as in the alternatives,
327 plus (CTemp u) for the tag (if needed)
330 This is all disgusting, because these amodes must be consistent with those
331 invented by CgAlgAlts.
334 getPrimAppResultAmodes
341 -- If there's an StgBindDefault which does use the bound
342 -- variable, then we can only handle it if the type involved is
343 -- an enumeration type. That's important in the case
349 -- The only reason for the restriction to *enumeration* types is our
350 -- inability to invent suitable temporaries to hold the results;
351 -- Elaborating the CTemp addr mode to have a second uniq field
352 -- (which would simply count from 1) would solve the problem.
353 -- Anyway, cgInlineAlts is now capable of handling all cases;
354 -- it's only this function which is being wimpish.
356 getPrimAppResultAmodes uniq (StgAlgAlts ty alts
357 (StgBindDefault rhs))
358 | isEnumerationTyCon spec_tycon = [tag_amode]
359 | otherwise = pprPanic "getPrimAppResultAmodes: non-enumeration algebraic alternatives with default" (ppr uniq <+> ppr rhs)
361 -- A temporary variable to hold the tag; this is unaffected by GC because
362 -- the heap-checks in the branches occur after the switch
363 tag_amode = CTemp uniq IntRep
364 (spec_tycon, _, _) = splitAlgTyConApp ty
367 If we don't have a default case, we could be scrutinising an unboxed
368 tuple, or an enumeration type...
371 getPrimAppResultAmodes uniq (StgAlgAlts ty alts other_default)
372 -- Default is either StgNoDefault or StgBindDefault with unused binder
374 | isEnumerationTyCon tycon = [CTemp uniq IntRep]
376 | isUnboxedTupleTyCon tycon =
378 [(con, args, use_mask, rhs)] ->
379 [ CTemp (getUnique arg) (idPrimRep arg) | arg <- args ]
380 _ -> panic "getPrimAppResultAmodes: case of unboxed tuple has multiple branches"
382 | otherwise = panic ("getPrimAppResultAmodes: case of primop has strange type: " ++ showSDoc (ppr ty))
384 where (tycon, _, _) = splitAlgTyConApp ty
387 The situation is simpler for primitive results, because there is only
391 getPrimAppResultAmodes uniq (StgPrimAlts ty _ _)
392 = [CTemp uniq (typePrimRep ty)]
396 %************************************************************************
398 \subsection[CgCase-alts]{Alternatives}
400 %************************************************************************
402 @cgEvalAlts@ returns an addressing mode for a continuation for the
403 alternatives of a @case@, used in a context when there
404 is some evaluation to be done.
407 cgEvalAlts :: Maybe VirtualSpOffset -- Offset of cost-centre to be restored, if any
409 -> SRT -- SRT for the continuation
411 -> FCode Sequel -- Any addr modes inside are guaranteed
412 -- to be a label so that we can duplicate it
413 -- without risk of duplicating code
415 cgEvalAlts cc_slot bndr srt alts
417 let uniq = getUnique bndr in
419 -- Generate the instruction to restore cost centre, if any
420 restoreCurrentCostCentre cc_slot `thenFC` \ cc_restore ->
422 -- get the stack liveness for the info table (after the CC slot has
423 -- been freed - this is important).
424 buildContLivenessMask uniq `thenFC` \ liveness_mask ->
428 -- algebraic alts ...
429 (StgAlgAlts ty alts deflt) ->
431 -- bind the default binder (it covers all the alternatives)
432 (if (isDeadBinder bndr)
434 else bindNewToReg bndr node mkLFArgument) `thenC`
436 -- Generate sequel info for use downstream
437 -- At the moment, we only do it if the type is vector-returnable.
438 -- Reason: if not, then it costs extra to label the
439 -- alternatives, because we'd get return code like:
441 -- switch TagReg { 0 : JMP(alt_1); 1 : JMP(alt_2) ..etc }
443 -- which is worse than having the alt code in the switch statement
445 let tycon_info = getScrutineeTyCon ty
446 is_alg = maybeToBool tycon_info
447 Just spec_tycon = tycon_info
450 -- deal with the unboxed tuple case
451 if is_alg && isUnboxedTupleTyCon spec_tycon then
453 [alt] -> let lbl = mkReturnInfoLabel uniq in
454 cgUnboxedTupleAlt lbl cc_restore True alt
456 getSRTLabel `thenFC` \srt_label ->
457 absC (CRetDirect uniq abs_c (srt_label, srt)
458 liveness_mask) `thenC`
459 returnFC (CaseAlts (CLbl lbl RetRep) Nothing)
460 _ -> panic "cgEvalAlts: dodgy case of unboxed tuple type"
462 -- normal algebraic (or polymorphic) case alternatives
464 ret_conv | is_alg = ctrlReturnConvAlg spec_tycon
465 | otherwise = UnvectoredReturn 0
467 use_labelled_alts = case ret_conv of
468 VectoredReturn _ -> True
472 = if use_labelled_alts then
473 cgSemiTaggedAlts bndr alts deflt -- Just <something>
475 Nothing -- no semi-tagging info
478 cgAlgAlts GCMayHappen uniq cc_restore use_labelled_alts (not is_alg)
479 alts deflt True `thenFC` \ (tagged_alt_absCs, deflt_absC) ->
481 mkReturnVector uniq tagged_alt_absCs deflt_absC srt liveness_mask
482 ret_conv `thenFC` \ return_vec ->
484 returnFC (CaseAlts return_vec semi_tagged_stuff)
487 (StgPrimAlts ty alts deflt) ->
489 -- Generate the switch
490 getAbsC (cgPrimEvalAlts bndr ty alts deflt) `thenFC` \ abs_c ->
492 -- Generate the labelled block, starting with restore-cost-centre
493 getSRTLabel `thenFC` \srt_label ->
494 absC (CRetDirect uniq (cc_restore `mkAbsCStmts` abs_c)
495 (srt_label,srt) liveness_mask) `thenC`
497 -- Return an amode for the block
498 returnFC (CaseAlts (CLbl (mkReturnPtLabel uniq) RetRep) Nothing)
508 HWL comment on {\em GrAnSim\/} (adding GRAN_YIELDs for context switch): If
509 we do an inlining of the case no separate functions for returning are
510 created, so we don't have to generate a GRAN_YIELD in that case. This info
511 must be propagated to cgAlgAltRhs (where the GRAN_YIELD macro might be
512 emitted). Hence, the new Bool arg to cgAlgAltRhs.
514 First case: primitive op returns an unboxed tuple.
517 cgInlineAlts bndr (StgAlgAlts ty [alt@(con,args,use_mask,rhs)] StgNoDefault)
518 | isUnboxedTupleCon con
519 = -- no heap check, no yield, just get in there and do it.
520 mapFCs bindNewToTemp args `thenFC` \ _ ->
524 = panic "cgInlineAlts: single alternative, not an unboxed tuple"
534 cgInlineAlts bndr (StgAlgAlts ty [] (StgBindDefault rhs))
535 = bindNewToTemp bndr `thenFC` \amode ->
537 (tycon, _, _) = splitAlgTyConApp ty
538 closure_lbl = CTableEntry (CLbl (mkClosureTblLabel tycon) PtrRep) amode PtrRep
540 absC (CAssign amode closure_lbl) `thenC`
544 Second case: algebraic case, several alternatives.
545 Tag is held in a temporary.
548 cgInlineAlts bndr (StgAlgAlts ty alts deflt)
549 = cgAlgAlts NoGC uniq AbsCNop{-restore_cc-} False{-no semi-tagging-}
550 False{-not poly case-} alts deflt
551 False{-don't emit yield-} `thenFC` \ (tagged_alts, deflt_c) ->
554 absC (mkAlgAltsCSwitch tag_amode tagged_alts deflt_c)
556 -- A temporary variable to hold the tag; this is unaffected by GC because
557 -- the heap-checks in the branches occur after the switch
558 tag_amode = CTemp uniq IntRep
559 uniq = getUnique bndr
562 Third (real) case: primitive result type.
565 cgInlineAlts bndr (StgPrimAlts ty alts deflt)
566 = cgPrimInlineAlts bndr ty alts deflt
570 %************************************************************************
572 \subsection[CgCase-alg-alts]{Algebraic alternatives}
574 %************************************************************************
576 In @cgAlgAlts@, none of the binders in the alternatives are
577 assumed to be yet bound.
579 HWL comment on {\em GrAnSim\/} (adding GRAN_YIELDs for context switch): The
580 last arg of cgAlgAlts indicates if we want a context switch at the
581 beginning of each alternative. Normally we want that. The only exception
582 are inlined alternatives.
587 -> AbstractC -- Restore-cost-centre instruction
588 -> Bool -- True <=> branches must be labelled
589 -> Bool -- True <=> polymorphic case
590 -> [(DataCon, [Id], [Bool], StgExpr)] -- The alternatives
591 -> StgCaseDefault -- The default
592 -> Bool -- Context switch at alts?
593 -> FCode ([(ConTag, AbstractC)], -- The branches
594 AbstractC -- The default case
597 cgAlgAlts gc_flag uniq restore_cc must_label_branches is_fun alts deflt
598 emit_yield{-should a yield macro be emitted?-}
600 = forkAlts (map (cgAlgAlt gc_flag uniq restore_cc must_label_branches emit_yield) alts)
601 (cgAlgDefault gc_flag is_fun uniq restore_cc must_label_branches deflt emit_yield)
605 cgAlgDefault :: GCFlag
606 -> Bool -- could be a function-typed result?
607 -> Unique -> AbstractC -> Bool -- turgid state...
608 -> StgCaseDefault -- input
610 -> FCode AbstractC -- output
612 cgAlgDefault gc_flag is_fun uniq restore_cc must_label_branch StgNoDefault _
615 cgAlgDefault gc_flag is_fun uniq restore_cc must_label_branch
617 emit_yield{-should a yield macro be emitted?-}
619 = -- We have arranged that Node points to the thing
620 getAbsC (absC restore_cc `thenC`
621 (if opt_GranMacros && emit_yield
622 then yield [node] False
623 else absC AbsCNop) `thenC`
624 possibleHeapCheck gc_flag is_fun [node] [] Nothing (cgExpr rhs)
625 -- Node is live, but doesn't need to point at the thing itself;
626 -- it's ok for Node to point to an indirection or FETCH_ME
627 -- Hence no need to re-enter Node.
628 ) `thenFC` \ abs_c ->
631 final_abs_c | must_label_branch = CCodeBlock lbl abs_c
636 lbl = mkDefaultLabel uniq
638 -- HWL comment on GrAnSim: GRAN_YIELDs needed; emitted in cgAlgAltRhs
641 -> Unique -> AbstractC -> Bool -- turgid state
642 -> Bool -- Context switch at alts?
643 -> (DataCon, [Id], [Bool], StgExpr)
644 -> FCode (ConTag, AbstractC)
646 cgAlgAlt gc_flag uniq restore_cc must_label_branch
647 emit_yield{-should a yield macro be emitted?-}
648 (con, args, use_mask, rhs)
649 = getAbsC (absC restore_cc `thenC`
650 (if opt_GranMacros && emit_yield
651 then yield [node] True -- XXX live regs wrong
652 else absC AbsCNop) `thenC`
654 NoGC -> mapFCs bindNewToTemp args `thenFC` \_ -> nopC
655 GCMayHappen -> bindConArgs con args
657 possibleHeapCheck gc_flag False [node] [] Nothing (
659 ) `thenFC` \ abs_c ->
661 final_abs_c | must_label_branch = CCodeBlock lbl abs_c
664 returnFC (tag, final_abs_c)
667 lbl = mkAltLabel uniq tag
670 :: CLabel -- label of the alternative
672 -> Bool -- ctxt switch
673 -> (DataCon, [Id], [Bool], StgExpr) -- alternative
676 cgUnboxedTupleAlt lbl restore_cc emit_yield (con,args,use_mask,rhs)
678 absC restore_cc `thenC`
680 bindUnboxedTupleComponents args
681 `thenFC` \ (live_regs,tags,stack_res) ->
682 (if opt_GranMacros && emit_yield
683 then yield live_regs True -- XXX live regs wrong?
684 else absC AbsCNop) `thenC`
686 -- ToDo: could maybe use Nothing here if stack_res is False
687 -- since the heap-check can just return to the top of the
692 -- free up stack slots containing tags,
693 freeStackSlots (map fst tags) `thenC`
695 -- generate a heap check if necessary
696 possibleHeapCheck GCMayHappen False live_regs tags ret_addr (
698 -- and finally the code for the alternative
703 %************************************************************************
705 \subsection[CgCase-semi-tagged-alts]{The code to deal with sem-tagging}
707 %************************************************************************
709 Turgid-but-non-monadic code to conjure up the required info from
710 algebraic case alternatives for semi-tagging.
713 cgSemiTaggedAlts :: Id
714 -> [(DataCon, [Id], [Bool], StgExpr)]
715 -> GenStgCaseDefault Id Id
718 cgSemiTaggedAlts binder alts deflt
719 = Just (map st_alt alts, st_deflt deflt)
721 uniq = getUnique binder
723 st_deflt StgNoDefault = Nothing
725 st_deflt (StgBindDefault _)
727 (CCallProfCtrMacro SLIT("RET_SEMI_BY_DEFAULT") [], -- ToDo: monadise?
731 st_alt (con, args, use_mask, _)
732 = -- Ha! Nothing to do; Node already points to the thing
734 (CCallProfCtrMacro SLIT("RET_SEMI_IN_HEAP") -- ToDo: monadise?
735 [mkIntCLit (length args)], -- how big the thing in the heap is
739 con_tag = dataConTag con
740 join_label = mkAltLabel uniq con_tag
743 %************************************************************************
745 \subsection[CgCase-prim-alts]{Primitive alternatives}
747 %************************************************************************
749 @cgPrimEvalAlts@ and @cgPrimInlineAlts@ generate suitable @CSwitch@es
750 for dealing with the alternatives of a primitive @case@, given an
751 addressing mode for the thing to scrutinise. It also keeps track of
752 the maximum stack depth encountered down any branch.
754 As usual, no binders in the alternatives are yet bound.
757 cgPrimInlineAlts bndr ty alts deflt
758 = cgPrimAltsWithDefault bndr NoGC (CTemp uniq kind) alts deflt []
760 uniq = getUnique bndr
761 kind = typePrimRep ty
763 cgPrimEvalAlts bndr ty alts deflt
764 = cgPrimAltsWithDefault bndr GCMayHappen (CReg reg) alts deflt [reg]
766 reg = dataReturnConvPrim kind
767 kind = typePrimRep ty
769 cgPrimAltsWithDefault bndr gc_flag scrutinee alts deflt regs
770 = -- first bind the default if necessary
771 (if isDeadBinder bndr
773 else bindNewPrimToAmode bndr scrutinee) `thenC`
774 cgPrimAlts gc_flag scrutinee alts deflt regs
776 cgPrimAlts gc_flag scrutinee alts deflt regs
777 = forkAlts (map (cgPrimAlt gc_flag regs) alts)
778 (cgPrimDefault gc_flag regs deflt)
779 `thenFC` \ (alt_absCs, deflt_absC) ->
781 absC (CSwitch scrutinee alt_absCs deflt_absC)
782 -- CSwitch does sensible things with one or zero alternatives
786 -> [MagicId] -- live registers
787 -> (Literal, StgExpr) -- The alternative
788 -> FCode (Literal, AbstractC) -- Its compiled form
790 cgPrimAlt gc_flag regs (lit, rhs)
791 = getAbsC rhs_code `thenFC` \ absC ->
794 rhs_code = possibleHeapCheck gc_flag False regs [] Nothing (cgExpr rhs)
796 cgPrimDefault :: GCFlag
797 -> [MagicId] -- live registers
801 cgPrimDefault gc_flag regs StgNoDefault
802 = panic "cgPrimDefault: No default in prim case"
804 cgPrimDefault gc_flag regs (StgBindDefault rhs)
805 = getAbsC (possibleHeapCheck gc_flag False regs [] Nothing (cgExpr rhs))
809 %************************************************************************
811 \subsection[CgCase-tidy]{Code for tidying up prior to an eval}
813 %************************************************************************
816 saveVolatileVarsAndRegs
817 :: StgLiveVars -- Vars which should be made safe
818 -> FCode (AbstractC, -- Assignments to do the saves
819 EndOfBlockInfo, -- sequel for the alts
820 Maybe VirtualSpOffset) -- Slot for current cost centre
823 saveVolatileVarsAndRegs vars
824 = saveVolatileVars vars `thenFC` \ var_saves ->
825 saveCurrentCostCentre `thenFC` \ (maybe_cc_slot, cc_save) ->
826 getEndOfBlockInfo `thenFC` \ eob_info ->
827 returnFC (mkAbstractCs [var_saves, cc_save],
832 saveVolatileVars :: StgLiveVars -- Vars which should be made safe
833 -> FCode AbstractC -- Assignments to to the saves
835 saveVolatileVars vars
836 = save_em (varSetElems vars)
838 save_em [] = returnFC AbsCNop
841 = getCAddrModeIfVolatile var `thenFC` \ v ->
843 Nothing -> save_em vars -- Non-volatile, so carry on
846 Just vol_amode -> -- Aha! It's volatile
847 save_var var vol_amode `thenFC` \ abs_c ->
848 save_em vars `thenFC` \ abs_cs ->
849 returnFC (abs_c `mkAbsCStmts` abs_cs)
851 save_var var vol_amode
852 = allocPrimStack (getPrimRepSize kind) `thenFC` \ slot ->
853 rebindToStack var slot `thenC`
854 getSpRelOffset slot `thenFC` \ sp_rel ->
855 returnFC (CAssign (CVal sp_rel kind) vol_amode)
857 kind = getAmodeRep vol_amode
860 ---------------------------------------------------------------------------
862 When we save the current cost centre (which is done for lexical
863 scoping), we allocate a free stack location, and return (a)~the
864 virtual offset of the location, to pass on to the alternatives, and
865 (b)~the assignment to do the save (just as for @saveVolatileVars@).
868 saveCurrentCostCentre ::
869 FCode (Maybe VirtualSpOffset, -- Where we decide to store it
870 AbstractC) -- Assignment to save it
872 saveCurrentCostCentre
873 = if not opt_SccProfilingOn then
874 returnFC (Nothing, AbsCNop)
876 allocPrimStack (getPrimRepSize CostCentreRep) `thenFC` \ slot ->
877 getSpRelOffset slot `thenFC` \ sp_rel ->
879 CAssign (CVal sp_rel CostCentreRep) (CReg CurCostCentre))
881 restoreCurrentCostCentre :: Maybe VirtualSpOffset -> FCode AbstractC
883 restoreCurrentCostCentre Nothing
885 restoreCurrentCostCentre (Just slot)
886 = getSpRelOffset slot `thenFC` \ sp_rel ->
887 freeStackSlots [slot] `thenC`
888 returnFC (CCallProfCCMacro SLIT("RESTORE_CCCS") [CVal sp_rel CostCentreRep])
889 -- we use the RESTORE_CCCS macro, rather than just
890 -- assigning into CurCostCentre, in case RESTORE_CCC
891 -- has some sanity-checking in it.
894 %************************************************************************
896 \subsection[CgCase-return-vec]{Building a return vector}
898 %************************************************************************
900 Build a return vector, and return a suitable label addressing
904 mkReturnVector :: Unique
905 -> [(ConTag, AbstractC)] -- Branch codes
906 -> AbstractC -- Default case
907 -> SRT -- continuation's SRT
908 -> Liveness -- stack liveness
909 -> CtrlReturnConvention
912 mkReturnVector uniq tagged_alt_absCs deflt_absC srt liveness ret_conv
913 = getSRTLabel `thenFC` \srt_label ->
915 srt_info = (srt_label, srt)
917 (return_vec_amode, vtbl_body) = case ret_conv of {
919 -- might be a polymorphic case...
920 UnvectoredReturn 0 ->
921 ASSERT(null tagged_alt_absCs)
922 (CLbl ret_label RetRep,
923 absC (CRetDirect uniq deflt_absC (srt_label, srt) liveness));
925 UnvectoredReturn n ->
926 -- find the tag explicitly rather than using tag_reg for now.
927 -- on architectures with lots of regs the tag will be loaded
928 -- into tag_reg by the code doing the returning.
930 tag = CMacroExpr WordRep GET_TAG [CVal (nodeRel 0) DataPtrRep]
932 (CLbl ret_label RetRep,
933 absC (CRetDirect uniq
934 (mkAlgAltsCSwitch tag tagged_alt_absCs deflt_absC)
938 VectoredReturn table_size ->
940 (vector_table, alts_absC) =
941 unzip (map mk_vector_entry [fIRST_TAG .. (table_size+fIRST_TAG-1)])
943 ret_vector = CRetVector vtbl_label
945 (srt_label, srt) liveness
947 (CLbl vtbl_label DataPtrRep,
948 -- alts come first, because we don't want to declare all the symbols
949 absC (mkAbstractCs (mkAbstractCs alts_absC : [deflt_absC,ret_vector]))
954 returnFC return_vec_amode
958 vtbl_label = mkVecTblLabel uniq
959 ret_label = mkReturnInfoLabel uniq
962 case nonemptyAbsC deflt_absC of
963 -- the simplifier might have eliminated a case
964 Nothing -> CLbl mkErrorStdEntryLabel CodePtrRep
965 Just absC@(CCodeBlock lbl _) -> CLbl lbl CodePtrRep
967 mk_vector_entry :: ConTag -> (CAddrMode, AbstractC)
969 = case [ absC | (t, absC) <- tagged_alt_absCs, t == tag ] of
970 [] -> (deflt_lbl, AbsCNop)
971 [absC@(CCodeBlock lbl _)] -> (CLbl lbl CodePtrRep,absC)
972 _ -> panic "mkReturnVector: too many"
975 %************************************************************************
977 \subsection[CgCase-utils]{Utilities for handling case expressions}
979 %************************************************************************
981 @possibleHeapCheck@ tests a flag passed in to decide whether to do a
982 heap check or not. These heap checks are always in a case
983 alternative, so we use altHeapCheck.
988 -> Bool -- True <=> algebraic case
989 -> [MagicId] -- live registers
990 -> [(VirtualSpOffset,Int)] -- stack slots to tag
991 -> Maybe CLabel -- return address
992 -> Code -- continuation
995 possibleHeapCheck GCMayHappen is_alg regs tags lbl code
996 = altHeapCheck is_alg regs tags AbsCNop lbl code
997 possibleHeapCheck NoGC _ _ tags lbl code
1001 splitTyConAppThroughNewTypes is like splitTyConApp_maybe except
1002 that it looks through newtypes in addition to synonyms. It's
1003 useful in the back end where we're not interested in newtypes
1006 Sometimes, we've thrown away the constructors during pruning in the
1007 renamer. In these cases, we emit a warning and fall back to using a
1008 SEQ_FRAME to evaluate the case scrutinee.
1011 getScrutineeTyCon :: Type -> Maybe TyCon
1012 getScrutineeTyCon ty =
1013 case (splitTyConAppThroughNewTypes ty) of
1016 if isFunTyCon tc then Nothing else -- not interested in funs
1017 if isPrimTyCon tc then Just tc else -- return primitive tycons
1018 -- otherwise (algebraic tycons) check the no. of constructors
1019 case (tyConFamilySize tc) of
1020 0 -> pprTrace "Warning" (hcat [
1021 text "constructors for ",
1023 text " not available.\n\tUse -fno-prune-tydecls to fix."
1027 splitTyConAppThroughNewTypes :: Type -> Maybe (TyCon, [Type])
1028 splitTyConAppThroughNewTypes ty
1029 = case splitTyConApp_maybe ty of
1031 | isNewTyCon tc -> splitTyConAppThroughNewTypes ty
1032 | otherwise -> Just (tc, tys)
1034 ([ty], _) = splitFunTys (applyTys (dataConType (head (tyConDataCons tc))) tys)