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 )
25 import CLabel ( CLabel, mkReturnInfoLabel, mkReturnPtLabel,
26 mkClosureTblLabel, mkClosureLabel,
27 moduleRegdLabel, labelDynamic,
29 import ClosureInfo ( infoTableLabelFromCI, entryLabelFromCI,
30 fastLabelFromCI, closureUpdReqd,
31 staticClosureNeedsLink
33 import Literal ( Literal(..), word2IntLit )
34 import Maybes ( maybeToBool )
35 import PrimOp ( primOpNeedsWrapper, PrimOp(..) )
36 import PrimRep ( isFloatingRep, PrimRep(..) )
37 import StixInfo ( genCodeInfoTable, genBitmapInfoTable )
38 import StixMacro ( macroCode, checkCode )
39 import StixPrim ( primCode, amodeToStix, amodeToStix' )
40 import Outputable ( pprPanic, ppr )
41 import UniqSupply ( returnUs, thenUs, mapUs, getUniqueUs, UniqSM )
42 import Util ( naturalMergeSortLe )
43 import Panic ( panic )
44 import TyCon ( tyConDataCons )
45 import DataCon ( dataConWrapId )
46 import BitSet ( intBS )
47 import Name ( NamedThing(..) )
49 import CmdLineOpts ( opt_Static, opt_EnsureSplittableC )
52 For each independent chunk of AbstractC code, we generate a list of
53 @StixTree@s, where each tree corresponds to a single Stix instruction.
54 We leave the chunks separated so that register allocation can be
55 performed locally within the chunk.
58 genCodeAbstractC :: AbstractC -> UniqSM [StixTree]
64 a2stix' = amodeToStix'
65 volsaves = volatileSaves
66 volrestores = volatileRestores
68 macro_code = macroCode
69 -- real code follows... ---------
72 Here we handle top-level things, like @CCodeBlock@s and
82 gentopcode (CCodeBlock lbl absC)
83 = gencode absC `thenUs` \ code ->
84 returnUs (StSegment TextSegment : StFunBegin lbl : code [StFunEnd lbl])
86 gentopcode stmt@(CStaticClosure lbl _ _ _)
87 = genCodeStaticClosure stmt `thenUs` \ code ->
90 then StSegment DataSegment
91 : StLabel lbl : code []
92 else StSegment DataSegment
93 : StData PtrRep [StInt 0] -- DLLised world, need extra zero word
94 : StLabel lbl : code []
97 gentopcode stmt@(CRetVector lbl _ _ _)
98 = genCodeVecTbl stmt `thenUs` \ code ->
99 returnUs (StSegment TextSegment : code [StLabel lbl])
101 gentopcode stmt@(CRetDirect uniq absC srt liveness)
102 = gencode absC `thenUs` \ code ->
103 genBitmapInfoTable liveness srt closure_type False `thenUs` \ itbl ->
104 returnUs (StSegment TextSegment :
105 itbl (StLabel lbl_info : StLabel lbl_ret : code []))
107 lbl_info = mkReturnInfoLabel uniq
108 lbl_ret = mkReturnPtLabel uniq
109 closure_type = case liveness of
110 LvSmall _ -> rET_SMALL
113 gentopcode stmt@(CClosureInfoAndCode cl_info slow Nothing _)
116 = genCodeInfoTable stmt `thenUs` \ itbl ->
117 returnUs (StSegment TextSegment : itbl [])
120 = genCodeInfoTable stmt `thenUs` \ itbl ->
121 gencode slow `thenUs` \ slow_code ->
122 returnUs (StSegment TextSegment : itbl (StFunBegin slow_lbl :
123 slow_code [StFunEnd slow_lbl]))
125 slow_is_empty = not (maybeToBool (nonemptyAbsC slow))
126 slow_lbl = entryLabelFromCI cl_info
128 gentopcode stmt@(CClosureInfoAndCode cl_info slow (Just fast) _) =
129 -- ToDo: what if this is empty? ------------------------^^^^
130 genCodeInfoTable stmt `thenUs` \ itbl ->
131 gencode slow `thenUs` \ slow_code ->
132 gencode fast `thenUs` \ fast_code ->
133 returnUs (StSegment TextSegment : itbl (StFunBegin slow_lbl :
134 slow_code (StFunEnd slow_lbl : StFunBegin fast_lbl :
135 fast_code [StFunEnd fast_lbl])))
137 slow_lbl = entryLabelFromCI cl_info
138 fast_lbl = fastLabelFromCI cl_info
140 gentopcode stmt@(CSRT lbl closures)
141 = returnUs [ StSegment TextSegment
143 , StData DataPtrRep (map mk_StCLbl_for_SRT closures)
146 mk_StCLbl_for_SRT :: CLabel -> StixTree
147 mk_StCLbl_for_SRT label
149 = StIndex CharRep (StCLbl label) (StInt 1)
153 gentopcode stmt@(CBitmap lbl mask)
154 = returnUs [ StSegment TextSegment
156 , StData WordRep (StInt (toInteger (length mask)) :
157 map (StInt . toInteger . intBS) mask)
160 gentopcode stmt@(CClosureTbl tycon)
161 = returnUs [ StSegment TextSegment
162 , StLabel (mkClosureTblLabel tycon)
163 , StData DataPtrRep (map (StCLbl . mkClosureLabel . getName . dataConWrapId)
164 (tyConDataCons tycon) )
167 gentopcode stmt@(CModuleInitBlock lbl absC)
168 = gencode absC `thenUs` \ code ->
169 getUniqLabelNCG `thenUs` \ tmp_lbl ->
170 getUniqLabelNCG `thenUs` \ flag_lbl ->
171 returnUs ( StSegment DataSegment
173 : StData IntRep [StInt 0]
174 : StSegment TextSegment
176 : StCondJump tmp_lbl (StPrim IntNeOp
177 [StInd IntRep (StCLbl flag_lbl),
179 : StAssign IntRep (StInd IntRep (StCLbl flag_lbl)) (StInt 1)
182 , StAssign PtrRep stgSp
183 (StIndex PtrRep stgSp (StInt (-1)))
184 , StJump (StInd WordRep stgSp)
188 = gencode absC `thenUs` \ code ->
189 returnUs (StSegment TextSegment : code [])
196 -> UniqSM StixTreeList
198 genCodeVecTbl (CRetVector lbl amodes srt liveness)
199 = genBitmapInfoTable liveness srt closure_type True `thenUs` \itbl ->
200 returnUs (\xs -> vectbl : itbl xs)
202 vectbl = StData PtrRep (reverse (map a2stix amodes))
203 closure_type = case liveness of
204 LvSmall _ -> rET_VEC_SMALL
205 LvLarge _ -> rET_VEC_BIG
213 -> UniqSM StixTreeList
215 genCodeStaticClosure (CStaticClosure _ cl_info cost_centre amodes)
216 = returnUs (\xs -> table ++ xs)
218 table = StData PtrRep [StCLbl (infoTableLabelFromCI cl_info)] :
219 map do_one_amode amodes ++
220 [StData PtrRep (padding_wds ++ static_link)]
223 = StData (promote_to_word (getAmodeRep amode)) [a2stix amode]
225 -- We need to promote any item smaller than a word to a word
226 promote_to_word CharRep = WordRep
227 promote_to_word other = other
229 -- always at least one padding word: this is the static link field
230 -- for the garbage collector.
231 padding_wds = if closureUpdReqd cl_info then
232 take (max 0 (mIN_UPD_SIZE - length amodes)) zeros
236 static_link | staticClosureNeedsLink cl_info = [StInt 0]
239 zeros = StInt 0 : zeros
242 -- Watch out for VoidKinds...cf. PprAbsC
244 | getAmodeRep item == VoidRep = StInt 0
245 | otherwise = a2stix item
250 Now the individual AbstractC statements.
256 -> UniqSM StixTreeList
260 @AbsCNop@s just disappear.
264 gencode AbsCNop = returnUs id
268 Split markers just insert a __stg_split_marker, which is caught by the
269 split-mangler later on and used to split the assembly into chunks.
274 | opt_EnsureSplittableC = returnUs (\xs -> StLabel mkSplitMarkerLabel : xs)
275 | otherwise = returnUs id
279 AbstractC instruction sequences are handled individually, and the
280 resulting StixTreeLists are joined together.
284 gencode (AbsCStmts c1 c2)
285 = gencode c1 `thenUs` \ b1 ->
286 gencode c2 `thenUs` \ b2 ->
291 Initialising closure headers in the heap...a fairly complex ordeal if
292 done properly. For now, we just set the info pointer, but we should
293 really take a peek at the flags to determine whether or not there are
294 other things to be done (setting cost centres, age headers, global
299 gencode (CInitHdr cl_info reg_rel _)
302 lbl = infoTableLabelFromCI cl_info
304 returnUs (\xs -> StAssign PtrRep (StInd PtrRep lhs) (StCLbl lbl) : xs)
312 gencode (CCheck macro args assts)
313 = gencode assts `thenUs` \assts_stix ->
314 checkCode macro args assts_stix
318 Assignment, the curse of von Neumann, is the center of the code we
319 produce. In most cases, the type of the assignment is determined
320 by the type of the destination. However, when the destination can
321 have mixed types, the type of the assignment is ``StgWord'' (we use
322 PtrRep for lack of anything better). Think: do we also want a cast
323 of the source? Be careful about floats/doubles.
327 gencode (CAssign lhs rhs)
328 | getAmodeRep lhs == VoidRep = returnUs id
330 = let pk = getAmodeRep lhs
331 pk' = if mixedTypeLocn lhs && not (isFloatingRep pk) then IntRep else pk
335 returnUs (\xs -> StAssign pk' lhs' rhs' : xs)
339 Unconditional jumps, including the special ``enter closure'' operation.
340 Note that the new entry convention requires that we load the InfoPtr (R2)
341 with the address of the info table before jumping to the entry code for Node.
343 For a vectored return, we must subtract the size of the info table to
344 get at the return vector. This depends on the size of the info table,
345 which varies depending on whether we're profiling etc.
350 = returnUs (\xs -> StJump (a2stix dest) : xs)
352 gencode (CFallThrough (CLbl lbl _))
353 = returnUs (\xs -> StFallThrough lbl : xs)
355 gencode (CReturn dest DirectReturn)
356 = returnUs (\xs -> StJump (a2stix dest) : xs)
358 gencode (CReturn table (StaticVectoredReturn n))
359 = returnUs (\xs -> StJump dest : xs)
361 dest = StInd PtrRep (StIndex PtrRep (a2stix table)
362 (StInt (toInteger (-n-fixedItblSize-1))))
364 gencode (CReturn table (DynamicVectoredReturn am))
365 = returnUs (\xs -> StJump dest : xs)
367 dest = StInd PtrRep (StIndex PtrRep (a2stix table) dyn_off)
368 dyn_off = StPrim IntSubOp [StPrim IntNegOp [a2stix am],
369 StInt (toInteger (fixedItblSize+1))]
373 Now the PrimOps, some of which may need caller-saves register wrappers.
377 gencode (COpStmt results op args vols)
378 -- ToDo (ADR?): use that liveness mask
379 | primOpNeedsWrapper op
381 saves = volsaves vols
382 restores = volrestores vols
384 p2stix (nonVoid results) op (nonVoid args)
386 returnUs (\xs -> saves ++ code (restores ++ xs))
388 | otherwise = p2stix (nonVoid results) op (nonVoid args)
390 nonVoid = filter ((/= VoidRep) . getAmodeRep)
394 Now the dreaded conditional jump.
396 Now the if statement. Almost *all* flow of control are of this form.
398 if (am==lit) { absC } else { absCdef }
412 gencode (CSwitch discrim alts deflt)
416 [(tag,alt_code)] -> case maybe_empty_deflt of
417 Nothing -> gencode alt_code
418 Just dc -> mkIfThenElse discrim tag alt_code dc
420 [(tag1@(MachInt i1), alt_code1),
421 (tag2@(MachInt i2), alt_code2)]
422 | deflt_is_empty && i1 == 0 && i2 == 1
423 -> mkIfThenElse discrim tag1 alt_code1 alt_code2
424 | deflt_is_empty && i1 == 1 && i2 == 0
425 -> mkIfThenElse discrim tag2 alt_code2 alt_code1
427 -- If the @discrim@ is simple, then this unfolding is safe.
428 other | simple_discrim -> mkSimpleSwitches discrim alts deflt
430 -- Otherwise, we need to do a bit of work.
431 other -> getUniqueUs `thenUs` \ u ->
433 (CAssign (CTemp u pk) discrim)
434 (CSwitch (CTemp u pk) alts deflt))
437 maybe_empty_deflt = nonemptyAbsC deflt
438 deflt_is_empty = case maybe_empty_deflt of
442 pk = getAmodeRep discrim
444 simple_discrim = case discrim of
452 Finally, all of the disgusting AbstractC macros.
456 gencode (CMacroStmt macro args) = macro_code macro args
458 gencode (CCallProfCtrMacro macro _)
459 = returnUs (\xs -> StComment macro : xs)
461 gencode (CCallProfCCMacro macro _)
462 = returnUs (\xs -> StComment macro : xs)
465 = pprPanic "AbsCStixGen.gencode" (dumpRealC other)
468 Here, we generate a jump table if there are more than four (integer)
469 alternatives and the jump table occupancy is greater than 50%.
470 Otherwise, we generate a binary comparison tree. (Perhaps this could
475 intTag :: Literal -> Integer
476 intTag (MachChar c) = toInteger (ord c)
477 intTag (MachInt i) = i
478 intTag (MachWord w) = intTag (word2IntLit (MachWord w))
479 intTag _ = panic "intTag"
481 fltTag :: Literal -> Rational
483 fltTag (MachFloat f) = f
484 fltTag (MachDouble d) = d
485 fltTag x = pprPanic "fltTag" (ppr x)
489 :: CAddrMode -> [(Literal,AbstractC)] -> AbstractC
490 -> UniqSM StixTreeList
492 mkSimpleSwitches am alts absC
493 = getUniqLabelNCG `thenUs` \ udlbl ->
494 getUniqLabelNCG `thenUs` \ ujlbl ->
496 joinedAlts = map (\ (tag,code) -> (tag, mkJoin code ujlbl)) alts
497 sortedAlts = naturalMergeSortLe leAlt joinedAlts
498 -- naturalMergeSortLe, because we often get sorted alts to begin with
500 lowTag = intTag (fst (head sortedAlts))
501 highTag = intTag (fst (last sortedAlts))
503 -- lowest and highest possible values the discriminant could take
504 lowest = if floating then targetMinDouble else targetMinInt
505 highest = if floating then targetMaxDouble else targetMaxInt
508 if not floating && choices > 4 && highTag - lowTag < toInteger (2 * choices) then
509 mkJumpTable am' sortedAlts lowTag highTag udlbl
511 mkBinaryTree am' floating sortedAlts choices lowest highest udlbl
513 `thenUs` \ alt_code ->
514 gencode absC `thenUs` \ dflt_code ->
516 returnUs (\xs -> alt_code (StLabel udlbl : dflt_code (StLabel ujlbl : xs)))
519 floating = isFloatingRep (getAmodeRep am)
520 choices = length alts
522 (x@(MachChar _),_) `leAlt` (y,_) = intTag x <= intTag y
523 (x@(MachInt _), _) `leAlt` (y,_) = intTag x <= intTag y
524 (x@(MachWord _), _) `leAlt` (y,_) = intTag x <= intTag y
525 (x,_) `leAlt` (y,_) = fltTag x <= fltTag y
529 We use jump tables when doing an integer switch on a relatively dense
530 list of alternatives. We expect to be given a list of alternatives,
531 sorted by tag, and a range of values for which we are to generate a
532 table. Of course, the tags of the alternatives should lie within the
533 indicated range. The alternatives need not cover the range; a default
534 target is provided for the missing alternatives.
536 If a join is necessary after the switch, the alternatives should
537 already finish with a jump to the join point.
542 :: StixTree -- discriminant
543 -> [(Literal, AbstractC)] -- alternatives
544 -> Integer -- low tag
545 -> Integer -- high tag
546 -> CLabel -- default label
547 -> UniqSM StixTreeList
550 mkJumpTable am alts lowTag highTag dflt
551 = getUniqLabelNCG `thenUs` \ utlbl ->
552 mapUs genLabel alts `thenUs` \ branches ->
553 let cjmpLo = StCondJump dflt (StPrim IntLtOp [am, StInt (toInteger lowTag)])
554 cjmpHi = StCondJump dflt (StPrim IntGtOp [am, StInt (toInteger highTag)])
556 offset = StPrim IntSubOp [am, StInt lowTag]
558 jump = StJump (StInd PtrRep (StIndex PtrRep (StCLbl utlbl) offset))
560 table = StData PtrRep (mkTable branches [lowTag..highTag] [])
562 mapUs mkBranch branches `thenUs` \ alts ->
564 returnUs (\xs -> cjmpLo : cjmpHi : jump :
565 StSegment DataSegment : tlbl : table :
566 StSegment TextSegment : foldr1 (.) alts xs)
569 genLabel x = getUniqLabelNCG `thenUs` \ lbl -> returnUs (lbl, x)
571 mkBranch (lbl,(_,alt)) =
572 gencode alt `thenUs` \ alt_code ->
573 returnUs (\xs -> StLabel lbl : alt_code xs)
575 mkTable _ [] tbl = reverse tbl
576 mkTable [] (x:xs) tbl = mkTable [] xs (StCLbl dflt : tbl)
577 mkTable alts@((lbl,(tag,_)):rest) (x:xs) tbl
578 | intTag tag == x = mkTable rest xs (StCLbl lbl : tbl)
579 | otherwise = mkTable alts xs (StCLbl dflt : tbl)
583 We generate binary comparison trees when a jump table is inappropriate.
584 We expect to be given a list of alternatives, sorted by tag, and for
585 convenience, the length of the alternative list. We recursively break
586 the list in half and do a comparison on the first tag of the second half
587 of the list. (Odd lists are broken so that the second half of the list
588 is longer.) We can handle either integer or floating kind alternatives,
589 so long as they are not mixed. (We assume that the type of the discriminant
590 determines the type of the alternatives.)
592 As with the jump table approach, if a join is necessary after the switch, the
593 alternatives should already finish with a jump to the join point.
598 :: StixTree -- discriminant
599 -> Bool -- floating point?
600 -> [(Literal, AbstractC)] -- alternatives
601 -> Int -- number of choices
602 -> Literal -- low tag
603 -> Literal -- high tag
604 -> CLabel -- default code label
605 -> UniqSM StixTreeList
608 mkBinaryTree am floating [(tag,alt)] _ lowTag highTag udlbl
609 | rangeOfOne = gencode alt
611 = let tag' = a2stix (CLit tag)
612 cmpOp = if floating then DoubleNeOp else IntNeOp
613 test = StPrim cmpOp [am, tag']
614 cjmp = StCondJump udlbl test
616 gencode alt `thenUs` \ alt_code ->
617 returnUs (\xs -> cjmp : alt_code xs)
620 rangeOfOne = not floating && intTag lowTag + 1 >= intTag highTag
621 -- When there is only one possible tag left in range, we skip the comparison
623 mkBinaryTree am floating alts choices lowTag highTag udlbl
624 = getUniqLabelNCG `thenUs` \ uhlbl ->
625 let tag' = a2stix (CLit splitTag)
626 cmpOp = if floating then DoubleGeOp else IntGeOp
627 test = StPrim cmpOp [am, tag']
628 cjmp = StCondJump uhlbl test
630 mkBinaryTree am floating alts_lo half lowTag splitTag udlbl
631 `thenUs` \ lo_code ->
632 mkBinaryTree am floating alts_hi (choices - half) splitTag highTag udlbl
633 `thenUs` \ hi_code ->
635 returnUs (\xs -> cjmp : lo_code (StLabel uhlbl : hi_code xs))
638 half = choices `div` 2
639 (alts_lo, alts_hi) = splitAt half alts
640 splitTag = fst (head alts_hi)
647 :: CAddrMode -- discriminant
649 -> AbstractC -- if-part
650 -> AbstractC -- else-part
651 -> UniqSM StixTreeList
654 mkIfThenElse discrim tag alt deflt
655 = getUniqLabelNCG `thenUs` \ ujlbl ->
656 getUniqLabelNCG `thenUs` \ utlbl ->
657 let discrim' = a2stix discrim
658 tag' = a2stix (CLit tag)
659 cmpOp = if (isFloatingRep (getAmodeRep discrim)) then DoubleNeOp else IntNeOp
660 test = StPrim cmpOp [discrim', tag']
661 cjmp = StCondJump utlbl test
665 gencode (mkJoin alt ujlbl) `thenUs` \ alt_code ->
666 gencode deflt `thenUs` \ dflt_code ->
667 returnUs (\xs -> cjmp : alt_code (dest : dflt_code (join : xs)))
669 mkJoin :: AbstractC -> CLabel -> AbstractC
672 | mightFallThrough code = mkAbsCStmts code (CJump (CLbl lbl PtrRep))
676 %---------------------------------------------------------------------------
678 This answers the question: Can the code fall through to the next
679 line(s) of code? This errs towards saying True if it can't choose,
680 because it is used for eliminating needless jumps. In other words, if
681 you might possibly {\em not} jump, then say yes to falling through.
684 mightFallThrough :: AbstractC -> Bool
686 mightFallThrough absC = ft absC True
688 ft AbsCNop if_empty = if_empty
690 ft (CJump _) if_empty = False
691 ft (CReturn _ _) if_empty = False
692 ft (CSwitch _ alts deflt) if_empty
693 = ft deflt if_empty ||
694 or [ft alt if_empty | (_,alt) <- alts]
696 ft (AbsCStmts c1 c2) if_empty = ft c2 (ft c1 if_empty)
697 ft _ if_empty = if_empty
699 {- Old algorithm, which called nonemptyAbsC for every subexpression! =========
700 fallThroughAbsC (AbsCStmts c1 c2)
701 = case nonemptyAbsC c2 of
702 Nothing -> fallThroughAbsC c1
703 Just x -> fallThroughAbsC x
704 fallThroughAbsC (CJump _) = False
705 fallThroughAbsC (CReturn _ _) = False
706 fallThroughAbsC (CSwitch _ choices deflt)
707 = (not (isEmptyAbsC deflt) && fallThroughAbsC deflt)
708 || or (map (fallThroughAbsC . snd) choices)
709 fallThroughAbsC other = True
711 isEmptyAbsC :: AbstractC -> Bool
712 isEmptyAbsC = not . maybeToBool . nonemptyAbsC
713 ================= End of old, quadratic, algorithm -}