2 % (c) The AQUA Project, Glasgow University, 1993-1998
6 module AbsCStixGen ( genCodeAbstractC ) where
8 #include "HsVersions.h"
10 import Ratio ( Rational )
16 import AbsCUtils ( getAmodeRep, mixedTypeLocn,
17 nonemptyAbsC, mkAbsCStmts
19 import PprAbsC ( dumpRealC )
20 import SMRep ( fixedItblSize,
22 rET_VEC_SMALL, rET_VEC_BIG
24 import Constants ( mIN_UPD_SIZE, wORD_SIZE )
25 import CLabel ( CLabel, mkReturnInfoLabel, mkReturnPtLabel,
26 mkClosureTblLabel, mkClosureLabel,
27 labelDynamic, mkSplitMarkerLabel )
28 import ClosureInfo ( infoTableLabelFromCI, entryLabelFromCI,
29 closureLabelFromCI, fastLabelFromCI
31 import Literal ( Literal(..), word2IntLit )
32 import Maybes ( maybeToBool )
33 import StgSyn ( StgOp(..) )
34 import MachOp ( MachOp(..), resultRepOfMachOp )
35 import PrimRep ( isFloatingRep, is64BitRep,
36 PrimRep(..), getPrimRepArrayElemSize )
37 import StixInfo ( genCodeInfoTable, genBitmapInfoTable,
38 livenessIsSmall, bitmapToIntegers )
39 import StixMacro ( macroCode, checkCode )
40 import StixPrim ( foreignCallCode, amodeToStix, amodeToStix' )
41 import Outputable ( pprPanic, ppr )
42 import UniqSupply ( returnUs, thenUs, mapUs, getUniqueUs, UniqSM )
43 import Util ( naturalMergeSortLe )
44 import Panic ( panic )
45 import TyCon ( tyConDataCons )
46 import DataCon ( dataConWrapId )
47 import Name ( NamedThing(..) )
48 import CmdLineOpts ( opt_Static, opt_EnsureSplittableC )
49 import Outputable ( assertPanic )
52 --import IOExts ( trace )
53 --import Outputable ( showSDoc )
54 --import MachOp ( pprMachOp )
58 For each independent chunk of AbstractC code, we generate a list of
59 @StixTree@s, where each tree corresponds to a single Stix instruction.
60 We leave the chunks separated so that register allocation can be
61 performed locally within the chunk.
64 genCodeAbstractC :: AbstractC -> UniqSM [StixStmt]
70 a2stix' = amodeToStix'
71 volsaves = volatileSaves
72 volrestores = volatileRestores
73 macro_code = macroCode
74 -- real code follows... ---------
77 Here we handle top-level things, like @CCodeBlock@s and
87 gentopcode (CCodeBlock lbl absC)
88 = gencode absC `thenUs` \ code ->
89 returnUs (StSegment TextSegment : StFunBegin lbl : code [StFunEnd lbl])
91 gentopcode stmt@(CStaticClosure closure_info _ _)
92 = genCodeStaticClosure stmt `thenUs` \ code ->
95 then StSegment DataSegment
96 : StLabel lbl : code []
97 else StSegment DataSegment
98 : StData PtrRep [StInt 0] -- DLLised world, need extra zero word
99 : StLabel lbl : code []
102 lbl = closureLabelFromCI closure_info
104 gentopcode stmt@(CRetVector lbl _ _ _)
105 = genCodeVecTbl stmt `thenUs` \ code ->
106 returnUs (StSegment TextSegment
107 : code [StLabel lbl, vtbl_post_label_word])
109 -- We put a dummy word after the vtbl label so as to ensure the label
110 -- is in the same (Text) section as the vtbl it labels. This is critical
111 -- for ensuring the GC works correctly, although GC crashes due to
112 -- misclassification are much more likely to show up in the interactive
113 -- system than in compile code. For details see comment near line 1164
114 -- of ghc/driver/mangler/ghc-asm.lprl, which contains an analogous fix
115 -- for the mangled via-C route.
116 vtbl_post_label_word = StData PtrRep [StInt 0]
118 gentopcode stmt@(CRetDirect uniq absC srt liveness)
119 = gencode absC `thenUs` \ code ->
120 genBitmapInfoTable liveness srt closure_type False `thenUs` \ itbl ->
121 returnUs (StSegment TextSegment :
122 itbl (StLabel lbl_info : StLabel lbl_ret : code []))
124 lbl_info = mkReturnInfoLabel uniq
125 lbl_ret = mkReturnPtLabel uniq
126 closure_type = if livenessIsSmall liveness then rET_SMALL else rET_BIG
128 gentopcode stmt@(CClosureInfoAndCode cl_info slow Nothing _)
131 = genCodeInfoTable stmt `thenUs` \ itbl ->
132 returnUs (StSegment TextSegment : itbl [])
135 = genCodeInfoTable stmt `thenUs` \ itbl ->
136 gencode slow `thenUs` \ slow_code ->
137 returnUs (StSegment TextSegment : itbl (StFunBegin slow_lbl :
138 slow_code [StFunEnd slow_lbl]))
140 slow_is_empty = not (maybeToBool (nonemptyAbsC slow))
141 slow_lbl = entryLabelFromCI cl_info
143 gentopcode stmt@(CClosureInfoAndCode cl_info slow (Just fast) _) =
144 -- ToDo: what if this is empty? ------------------------^^^^
145 genCodeInfoTable stmt `thenUs` \ itbl ->
146 gencode slow `thenUs` \ slow_code ->
147 gencode fast `thenUs` \ fast_code ->
148 returnUs (StSegment TextSegment : itbl (StFunBegin slow_lbl :
149 slow_code (StFunEnd slow_lbl : StFunBegin fast_lbl :
150 fast_code [StFunEnd fast_lbl])))
152 slow_lbl = entryLabelFromCI cl_info
153 fast_lbl = fastLabelFromCI cl_info
155 gentopcode stmt@(CSRT lbl closures)
156 = returnUs [ StSegment TextSegment
158 , StData DataPtrRep (map mk_StCLbl_for_SRT closures)
161 mk_StCLbl_for_SRT :: CLabel -> StixExpr
162 mk_StCLbl_for_SRT label
164 = StIndex Int8Rep (StCLbl label) (StInt 1)
168 gentopcode stmt@(CBitmap lbl mask)
169 = returnUs $ case bitmapToIntegers mask of
171 [ StSegment TextSegment
173 , StData WordRep (map StInt (toInteger (length mask') : mask'))
177 gentopcode stmt@(CClosureTbl tycon)
178 = returnUs [ StSegment TextSegment
179 , StLabel (mkClosureTblLabel tycon)
180 , StData DataPtrRep (map (StCLbl . mkClosureLabel . getName . dataConWrapId)
181 (tyConDataCons tycon) )
184 gentopcode stmt@(CModuleInitBlock lbl absC)
185 = gencode absC `thenUs` \ code ->
186 getUniqLabelNCG `thenUs` \ tmp_lbl ->
187 getUniqLabelNCG `thenUs` \ flag_lbl ->
188 returnUs ( StSegment DataSegment
190 : StData IntRep [StInt 0]
191 : StSegment TextSegment
193 : StCondJump tmp_lbl (StMachOp MO_Nat_Ne
194 [StInd IntRep (StCLbl flag_lbl),
196 : StAssignMem IntRep (StCLbl flag_lbl) (StInt 1)
199 , StAssignReg PtrRep stgSp
200 (StIndex PtrRep (StReg stgSp) (StInt (-1)))
201 , StJump NoDestInfo (StInd WordRep (StReg stgSp))
205 = gencode absC `thenUs` \ code ->
206 returnUs (StSegment TextSegment : code [])
213 -> UniqSM StixTreeList
215 genCodeVecTbl (CRetVector lbl amodes srt liveness)
216 = genBitmapInfoTable liveness srt closure_type True `thenUs` \itbl ->
217 returnUs (\xs -> vectbl : itbl xs)
219 vectbl = StData PtrRep (reverse (map a2stix amodes))
220 closure_type = if livenessIsSmall liveness then rET_VEC_SMALL else rET_VEC_BIG
228 -> UniqSM StixTreeList
230 genCodeStaticClosure (CStaticClosure cl_info cost_centre amodes)
231 = returnUs (\xs -> table ++ xs)
233 table = StData PtrRep [StCLbl (infoTableLabelFromCI cl_info)] :
234 foldr do_one_amode [] amodes
236 do_one_amode amode rest
237 | rep == VoidRep = rest
238 | otherwise = StData (promote_to_word rep) [a2stix amode] : rest
240 rep = getAmodeRep amode
242 -- We need to promote any item smaller than a word to a word
244 | getPrimRepArrayElemSize pk >= getPrimRepArrayElemSize IntRep = pk
248 Now the individual AbstractC statements.
254 -> UniqSM StixTreeList
258 @AbsCNop@s just disappear.
262 gencode AbsCNop = returnUs id
266 Split markers just insert a __stg_split_marker, which is caught by the
267 split-mangler later on and used to split the assembly into chunks.
272 | opt_EnsureSplittableC = returnUs (\xs -> StLabel mkSplitMarkerLabel : xs)
273 | otherwise = returnUs id
277 AbstractC instruction sequences are handled individually, and the
278 resulting StixTreeLists are joined together.
282 gencode (AbsCStmts c1 c2)
283 = gencode c1 `thenUs` \ b1 ->
284 gencode c2 `thenUs` \ b2 ->
287 gencode (CSequential stuff)
291 foo (s:ss) = gencode s `thenUs` \ stix ->
292 foo ss `thenUs` \ stixes ->
293 returnUs (stix . stixes)
297 Initialising closure headers in the heap...a fairly complex ordeal if
298 done properly. For now, we just set the info pointer, but we should
299 really take a peek at the flags to determine whether or not there are
300 other things to be done (setting cost centres, age headers, global
305 gencode (CInitHdr cl_info reg_rel _ _)
308 lbl = infoTableLabelFromCI cl_info
310 returnUs (\xs -> StAssignMem PtrRep lhs (StCLbl lbl) : xs)
318 gencode (CCheck macro args assts)
319 = gencode assts `thenUs` \assts_stix ->
320 checkCode macro args assts_stix
324 Assignment, the curse of von Neumann, is the center of the code we
325 produce. In most cases, the type of the assignment is determined
326 by the type of the destination. However, when the destination can
327 have mixed types, the type of the assignment is ``StgWord'' (we use
328 PtrRep for lack of anything better). Think: do we also want a cast
329 of the source? Be careful about floats/doubles.
333 gencode (CAssign lhs rhs)
337 = let -- This is a Hack. Should be cleaned up.
339 pk' | ncg_target_is_32bit && is64BitRep lhs_rep
342 = if mixedTypeLocn lhs && not (isFloatingRep lhs_rep)
348 returnUs (\xs -> mkStAssign pk' lhs' rhs' : xs)
350 lhs_rep = getAmodeRep lhs
354 Unconditional jumps, including the special ``enter closure'' operation.
355 Note that the new entry convention requires that we load the InfoPtr (R2)
356 with the address of the info table before jumping to the entry code for Node.
358 For a vectored return, we must subtract the size of the info table to
359 get at the return vector. This depends on the size of the info table,
360 which varies depending on whether we're profiling etc.
365 = returnUs (\xs -> StJump NoDestInfo (a2stix dest) : xs)
367 gencode (CFallThrough (CLbl lbl _))
368 = returnUs (\xs -> StFallThrough lbl : xs)
370 gencode (CReturn dest DirectReturn)
371 = returnUs (\xs -> StJump NoDestInfo (a2stix dest) : xs)
373 gencode (CReturn table (StaticVectoredReturn n))
374 = returnUs (\xs -> StJump NoDestInfo dest : xs)
376 dest = StInd PtrRep (StIndex PtrRep (a2stix table)
377 (StInt (toInteger (-n-fixedItblSize-1))))
379 gencode (CReturn table (DynamicVectoredReturn am))
380 = returnUs (\xs -> StJump NoDestInfo dest : xs)
382 dest = StInd PtrRep (StIndex PtrRep (a2stix table) dyn_off)
383 dyn_off = StMachOp MO_Nat_Sub [StMachOp MO_NatS_Neg [a2stix am],
384 StInt (toInteger (fixedItblSize+1))]
388 Now the PrimOps, some of which may need caller-saves register wrappers.
391 gencode (COpStmt results (StgFCallOp fcall _) args vols)
392 = ASSERT( null vols )
393 foreignCallCode (nonVoid results) fcall (nonVoid args)
395 gencode (COpStmt results (StgPrimOp op) args vols)
396 = panic "AbsCStixGen.gencode: un-translated PrimOp"
398 gencode (CMachOpStmt res mop args vols)
399 = returnUs (\xs -> mkStAssign (resultRepOfMachOp mop) (a2stix res)
400 (StMachOp mop (map a2stix args))
405 Now the dreaded conditional jump.
407 Now the if statement. Almost *all* flow of control are of this form.
409 if (am==lit) { absC } else { absCdef }
423 gencode (CSwitch discrim alts deflt)
427 [(tag,alt_code)] -> case maybe_empty_deflt of
428 Nothing -> gencode alt_code
429 Just dc -> mkIfThenElse discrim tag alt_code dc
431 [(tag1@(MachInt i1), alt_code1),
432 (tag2@(MachInt i2), alt_code2)]
433 | deflt_is_empty && i1 == 0 && i2 == 1
434 -> mkIfThenElse discrim tag1 alt_code1 alt_code2
435 | deflt_is_empty && i1 == 1 && i2 == 0
436 -> mkIfThenElse discrim tag2 alt_code2 alt_code1
438 -- If the @discrim@ is simple, then this unfolding is safe.
439 other | simple_discrim -> mkSimpleSwitches discrim alts deflt
441 -- Otherwise, we need to do a bit of work.
442 other -> getUniqueUs `thenUs` \ u ->
444 (CAssign (CTemp u pk) discrim)
445 (CSwitch (CTemp u pk) alts deflt))
448 maybe_empty_deflt = nonemptyAbsC deflt
449 deflt_is_empty = case maybe_empty_deflt of
453 pk = getAmodeRep discrim
455 simple_discrim = case discrim of
463 Finally, all of the disgusting AbstractC macros.
467 gencode (CMacroStmt macro args) = macro_code macro args
469 gencode (CCallProfCtrMacro macro _)
470 = returnUs (\xs -> StComment macro : xs)
472 gencode (CCallProfCCMacro macro _)
473 = returnUs (\xs -> StComment macro : xs)
475 gencode CCallTypedef{} = returnUs id
478 = pprPanic "AbsCStixGen.gencode" (dumpRealC other)
480 nonVoid = filter ((/= VoidRep) . getAmodeRep)
483 Here, we generate a jump table if there are more than four (integer)
484 alternatives and the jump table occupancy is greater than 50%.
485 Otherwise, we generate a binary comparison tree. (Perhaps this could
490 intTag :: Literal -> Integer
491 intTag (MachChar c) = toInteger c
492 intTag (MachInt i) = i
493 intTag (MachWord w) = intTag (word2IntLit (MachWord w))
494 intTag _ = panic "intTag"
496 fltTag :: Literal -> Rational
498 fltTag (MachFloat f) = f
499 fltTag (MachDouble d) = d
500 fltTag x = pprPanic "fltTag" (ppr x)
504 :: CAddrMode -> [(Literal,AbstractC)] -> AbstractC
505 -> UniqSM StixTreeList
507 mkSimpleSwitches am alts absC
508 = getUniqLabelNCG `thenUs` \ udlbl ->
509 getUniqLabelNCG `thenUs` \ ujlbl ->
511 joinedAlts = map (\ (tag,code) -> (tag, mkJoin code ujlbl)) alts
512 sortedAlts = naturalMergeSortLe leAlt joinedAlts
513 -- naturalMergeSortLe, because we often get sorted alts to begin with
515 lowTag = intTag (fst (head sortedAlts))
516 highTag = intTag (fst (last sortedAlts))
518 -- lowest and highest possible values the discriminant could take
519 lowest = if floating then targetMinDouble else targetMinInt
520 highest = if floating then targetMaxDouble else targetMaxInt
523 if not floating && choices > 4
524 && highTag - lowTag < toInteger (2 * choices)
526 mkJumpTable am' sortedAlts lowTag highTag udlbl
528 mkBinaryTree am' floating sortedAlts choices lowest highest udlbl
530 `thenUs` \ alt_code ->
531 gencode absC `thenUs` \ dflt_code ->
533 returnUs (\xs -> alt_code (StLabel udlbl : dflt_code (StLabel ujlbl : xs)))
536 floating = isFloatingRep (getAmodeRep am)
537 choices = length alts
539 (x@(MachChar _),_) `leAlt` (y,_) = intTag x <= intTag y
540 (x@(MachInt _), _) `leAlt` (y,_) = intTag x <= intTag y
541 (x@(MachWord _), _) `leAlt` (y,_) = intTag x <= intTag y
542 (x,_) `leAlt` (y,_) = fltTag x <= fltTag y
546 We use jump tables when doing an integer switch on a relatively dense
547 list of alternatives. We expect to be given a list of alternatives,
548 sorted by tag, and a range of values for which we are to generate a
549 table. Of course, the tags of the alternatives should lie within the
550 indicated range. The alternatives need not cover the range; a default
551 target is provided for the missing alternatives.
553 If a join is necessary after the switch, the alternatives should
554 already finish with a jump to the join point.
559 :: StixTree -- discriminant
560 -> [(Literal, AbstractC)] -- alternatives
561 -> Integer -- low tag
562 -> Integer -- high tag
563 -> CLabel -- default label
564 -> UniqSM StixTreeList
567 mkJumpTable am alts lowTag highTag dflt
568 = getUniqLabelNCG `thenUs` \ utlbl ->
569 mapUs genLabel alts `thenUs` \ branches ->
570 let cjmpLo = StCondJump dflt (StMachOp MO_NatS_Lt [am, StInt (toInteger lowTag)])
571 cjmpHi = StCondJump dflt (StMachOp MO_NatS_Gt [am, StInt (toInteger highTag)])
573 offset = StMachOp MO_Nat_Sub [am, StInt lowTag]
574 dsts = DestInfo (dflt : map fst branches)
576 jump = StJump dsts (StInd PtrRep (StIndex PtrRep (StCLbl utlbl) offset))
578 table = StData PtrRep (mkTable branches [lowTag..highTag] [])
580 mapUs mkBranch branches `thenUs` \ alts ->
582 returnUs (\xs -> cjmpLo : cjmpHi : jump :
583 StSegment DataSegment : tlbl : table :
584 StSegment TextSegment : foldr1 (.) alts xs)
587 genLabel x = getUniqLabelNCG `thenUs` \ lbl -> returnUs (lbl, x)
589 mkBranch (lbl,(_,alt)) =
590 gencode alt `thenUs` \ alt_code ->
591 returnUs (\xs -> StLabel lbl : alt_code xs)
593 mkTable _ [] tbl = reverse tbl
594 mkTable [] (x:xs) tbl = mkTable [] xs (StCLbl dflt : tbl)
595 mkTable alts@((lbl,(tag,_)):rest) (x:xs) tbl
596 | intTag tag == x = mkTable rest xs (StCLbl lbl : tbl)
597 | otherwise = mkTable alts xs (StCLbl dflt : tbl)
601 We generate binary comparison trees when a jump table is inappropriate.
602 We expect to be given a list of alternatives, sorted by tag, and for
603 convenience, the length of the alternative list. We recursively break
604 the list in half and do a comparison on the first tag of the second half
605 of the list. (Odd lists are broken so that the second half of the list
606 is longer.) We can handle either integer or floating kind alternatives,
607 so long as they are not mixed. (We assume that the type of the discriminant
608 determines the type of the alternatives.)
610 As with the jump table approach, if a join is necessary after the switch, the
611 alternatives should already finish with a jump to the join point.
616 :: StixTree -- discriminant
617 -> Bool -- floating point?
618 -> [(Literal, AbstractC)] -- alternatives
619 -> Int -- number of choices
620 -> Literal -- low tag
621 -> Literal -- high tag
622 -> CLabel -- default code label
623 -> UniqSM StixTreeList
626 mkBinaryTree am floating [(tag,alt)] _ lowTag highTag udlbl
627 | rangeOfOne = gencode alt
629 = let tag' = a2stix (CLit tag)
630 cmpOp = if floating then MO_Dbl_Ne else MO_Nat_Ne
631 test = StMachOp cmpOp [am, tag']
632 cjmp = StCondJump udlbl test
634 gencode alt `thenUs` \ alt_code ->
635 returnUs (\xs -> cjmp : alt_code xs)
638 rangeOfOne = not floating && intTag lowTag + 1 >= intTag highTag
639 -- When there is only one possible tag left in range, we skip the comparison
641 mkBinaryTree am floating alts choices lowTag highTag udlbl
642 = getUniqLabelNCG `thenUs` \ uhlbl ->
643 let tag' = a2stix (CLit splitTag)
644 cmpOp = if floating then MO_Dbl_Ge else MO_NatS_Ge
645 test = StMachOp cmpOp [am, tag']
646 cjmp = StCondJump uhlbl test
648 mkBinaryTree am floating alts_lo half lowTag splitTag udlbl
649 `thenUs` \ lo_code ->
650 mkBinaryTree am floating alts_hi (choices - half) splitTag highTag udlbl
651 `thenUs` \ hi_code ->
653 returnUs (\xs -> cjmp : lo_code (StLabel uhlbl : hi_code xs))
656 half = choices `div` 2
657 (alts_lo, alts_hi) = splitAt half alts
658 splitTag = fst (head alts_hi)
665 :: CAddrMode -- discriminant
667 -> AbstractC -- if-part
668 -> AbstractC -- else-part
669 -> UniqSM StixTreeList
672 mkIfThenElse discrim tag alt deflt
673 = getUniqLabelNCG `thenUs` \ ujlbl ->
674 getUniqLabelNCG `thenUs` \ utlbl ->
675 let discrim' = a2stix discrim
676 tag' = a2stix (CLit tag)
677 cmpOp = if (isFloatingRep (getAmodeRep discrim)) then MO_Dbl_Ne else MO_Nat_Ne
678 test = StMachOp cmpOp [discrim', tag']
679 cjmp = StCondJump utlbl test
683 gencode (mkJoin alt ujlbl) `thenUs` \ alt_code ->
684 gencode deflt `thenUs` \ dflt_code ->
685 returnUs (\xs -> cjmp : alt_code (dest : dflt_code (join : xs)))
688 mkJoin :: AbstractC -> CLabel -> AbstractC
690 | mightFallThrough code = mkAbsCStmts code (CJump (CLbl lbl PtrRep))
694 %---------------------------------------------------------------------------
696 This answers the question: Can the code fall through to the next
697 line(s) of code? This errs towards saying True if it can't choose,
698 because it is used for eliminating needless jumps. In other words, if
699 you might possibly {\em not} jump, then say yes to falling through.
702 mightFallThrough :: AbstractC -> Bool
704 mightFallThrough absC = ft absC True
706 ft AbsCNop if_empty = if_empty
708 ft (CJump _) if_empty = False
709 ft (CReturn _ _) if_empty = False
710 ft (CSwitch _ alts deflt) if_empty
711 = ft deflt if_empty ||
712 or [ft alt if_empty | (_,alt) <- alts]
714 ft (AbsCStmts c1 c2) if_empty = ft c2 (ft c1 if_empty)
715 ft _ if_empty = if_empty
717 {- Old algorithm, which called nonemptyAbsC for every subexpression! =========
718 fallThroughAbsC (AbsCStmts c1 c2)
719 = case nonemptyAbsC c2 of
720 Nothing -> fallThroughAbsC c1
721 Just x -> fallThroughAbsC x
722 fallThroughAbsC (CJump _) = False
723 fallThroughAbsC (CReturn _ _) = False
724 fallThroughAbsC (CSwitch _ choices deflt)
725 = (not (isEmptyAbsC deflt) && fallThroughAbsC deflt)
726 || or (map (fallThroughAbsC . snd) choices)
727 fallThroughAbsC other = True
729 isEmptyAbsC :: AbstractC -> Bool
730 isEmptyAbsC = not . maybeToBool . nonemptyAbsC
731 ================= End of old, quadratic, algorithm -}