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 labelDynamic, mkSplitMarkerLabel )
28 import ClosureInfo ( infoTableLabelFromCI, entryLabelFromCI,
29 fastLabelFromCI, closureUpdReqd,
30 staticClosureNeedsLink
32 import Literal ( Literal(..), word2IntLit )
33 import Maybes ( maybeToBool )
34 import PrimOp ( primOpNeedsWrapper, PrimOp(..) )
35 import PrimRep ( isFloatingRep, PrimRep(..) )
36 import StixInfo ( genCodeInfoTable, genBitmapInfoTable )
37 import StixMacro ( macroCode, checkCode )
38 import StixPrim ( primCode, amodeToStix, amodeToStix' )
39 import Outputable ( pprPanic, ppr )
40 import UniqSupply ( returnUs, thenUs, mapUs, getUniqueUs, UniqSM )
41 import Util ( naturalMergeSortLe )
42 import Panic ( panic )
43 import TyCon ( tyConDataCons )
44 import DataCon ( dataConWrapId )
45 import BitSet ( intBS )
46 import Name ( NamedThing(..) )
47 import CmdLineOpts ( opt_Static, opt_EnsureSplittableC )
50 For each independent chunk of AbstractC code, we generate a list of
51 @StixTree@s, where each tree corresponds to a single Stix instruction.
52 We leave the chunks separated so that register allocation can be
53 performed locally within the chunk.
56 genCodeAbstractC :: AbstractC -> UniqSM [StixTree]
62 a2stix' = amodeToStix'
63 volsaves = volatileSaves
64 volrestores = volatileRestores
66 macro_code = macroCode
67 -- real code follows... ---------
70 Here we handle top-level things, like @CCodeBlock@s and
80 gentopcode (CCodeBlock lbl absC)
81 = gencode absC `thenUs` \ code ->
82 returnUs (StSegment TextSegment : StFunBegin lbl : code [StFunEnd lbl])
84 gentopcode stmt@(CStaticClosure lbl _ _ _)
85 = genCodeStaticClosure stmt `thenUs` \ code ->
88 then StSegment DataSegment
89 : StLabel lbl : code []
90 else StSegment DataSegment
91 : StData PtrRep [StInt 0] -- DLLised world, need extra zero word
92 : StLabel lbl : code []
95 gentopcode stmt@(CRetVector lbl _ _ _)
96 = genCodeVecTbl stmt `thenUs` \ code ->
97 returnUs (StSegment TextSegment : code [StLabel lbl])
99 gentopcode stmt@(CRetDirect uniq absC srt liveness)
100 = gencode absC `thenUs` \ code ->
101 genBitmapInfoTable liveness srt closure_type False `thenUs` \ itbl ->
102 returnUs (StSegment TextSegment :
103 itbl (StLabel lbl_info : StLabel lbl_ret : code []))
105 lbl_info = mkReturnInfoLabel uniq
106 lbl_ret = mkReturnPtLabel uniq
107 closure_type = case liveness of
108 LvSmall _ -> rET_SMALL
111 gentopcode stmt@(CClosureInfoAndCode cl_info slow Nothing _)
114 = genCodeInfoTable stmt `thenUs` \ itbl ->
115 returnUs (StSegment TextSegment : itbl [])
118 = genCodeInfoTable stmt `thenUs` \ itbl ->
119 gencode slow `thenUs` \ slow_code ->
120 returnUs (StSegment TextSegment : itbl (StFunBegin slow_lbl :
121 slow_code [StFunEnd slow_lbl]))
123 slow_is_empty = not (maybeToBool (nonemptyAbsC slow))
124 slow_lbl = entryLabelFromCI cl_info
126 gentopcode stmt@(CClosureInfoAndCode cl_info slow (Just fast) _) =
127 -- ToDo: what if this is empty? ------------------------^^^^
128 genCodeInfoTable stmt `thenUs` \ itbl ->
129 gencode slow `thenUs` \ slow_code ->
130 gencode fast `thenUs` \ fast_code ->
131 returnUs (StSegment TextSegment : itbl (StFunBegin slow_lbl :
132 slow_code (StFunEnd slow_lbl : StFunBegin fast_lbl :
133 fast_code [StFunEnd fast_lbl])))
135 slow_lbl = entryLabelFromCI cl_info
136 fast_lbl = fastLabelFromCI cl_info
138 gentopcode stmt@(CSRT lbl closures)
139 = returnUs [ StSegment TextSegment
141 , StData DataPtrRep (map mk_StCLbl_for_SRT closures)
144 mk_StCLbl_for_SRT :: CLabel -> StixTree
145 mk_StCLbl_for_SRT label
147 = StIndex Int8Rep (StCLbl label) (StInt 1)
151 gentopcode stmt@(CBitmap lbl mask)
152 = returnUs [ StSegment TextSegment
154 , StData WordRep (StInt (toInteger (length mask)) :
155 map (StInt . toInteger . intBS) mask)
158 gentopcode stmt@(CClosureTbl tycon)
159 = returnUs [ StSegment TextSegment
160 , StLabel (mkClosureTblLabel tycon)
161 , StData DataPtrRep (map (StCLbl . mkClosureLabel . getName . dataConWrapId)
162 (tyConDataCons tycon) )
165 gentopcode stmt@(CModuleInitBlock lbl absC)
166 = gencode absC `thenUs` \ code ->
167 getUniqLabelNCG `thenUs` \ tmp_lbl ->
168 getUniqLabelNCG `thenUs` \ flag_lbl ->
169 returnUs ( StSegment DataSegment
171 : StData IntRep [StInt 0]
172 : StSegment TextSegment
174 : StCondJump tmp_lbl (StPrim IntNeOp
175 [StInd IntRep (StCLbl flag_lbl),
177 : StAssign IntRep (StInd IntRep (StCLbl flag_lbl)) (StInt 1)
180 , StAssign PtrRep stgSp
181 (StIndex PtrRep stgSp (StInt (-1)))
182 , StJump NoDestInfo (StInd WordRep stgSp)
186 = gencode absC `thenUs` \ code ->
187 returnUs (StSegment TextSegment : code [])
194 -> UniqSM StixTreeList
196 genCodeVecTbl (CRetVector lbl amodes srt liveness)
197 = genBitmapInfoTable liveness srt closure_type True `thenUs` \itbl ->
198 returnUs (\xs -> vectbl : itbl xs)
200 vectbl = StData PtrRep (reverse (map a2stix amodes))
201 closure_type = case liveness of
202 LvSmall _ -> rET_VEC_SMALL
203 LvLarge _ -> rET_VEC_BIG
211 -> UniqSM StixTreeList
213 genCodeStaticClosure (CStaticClosure _ cl_info cost_centre amodes)
214 = returnUs (\xs -> table ++ xs)
216 table = StData PtrRep [StCLbl (infoTableLabelFromCI cl_info)] :
217 map do_one_amode amodes ++
218 [StData PtrRep (padding_wds ++ static_link)]
221 = StData (promote_to_word (getAmodeRep amode)) [a2stix amode]
223 -- We need to promote any item smaller than a word to a word
224 promote_to_word Int8Rep = IntRep
225 promote_to_word CharRep = IntRep
226 promote_to_word other = other
228 -- always at least one padding word: this is the static link field
229 -- for the garbage collector.
230 padding_wds = if closureUpdReqd cl_info then
231 take (max 0 (mIN_UPD_SIZE - length amodes)) zeros
235 static_link | staticClosureNeedsLink cl_info = [StInt 0]
238 zeros = StInt 0 : zeros
241 -- Watch out for VoidKinds...cf. PprAbsC
243 | getAmodeRep item == VoidRep = StInt 0
244 | otherwise = a2stix item
249 Now the individual AbstractC statements.
255 -> UniqSM StixTreeList
259 @AbsCNop@s just disappear.
263 gencode AbsCNop = returnUs id
267 Split markers just insert a __stg_split_marker, which is caught by the
268 split-mangler later on and used to split the assembly into chunks.
273 | opt_EnsureSplittableC = returnUs (\xs -> StLabel mkSplitMarkerLabel : xs)
274 | otherwise = returnUs id
278 AbstractC instruction sequences are handled individually, and the
279 resulting StixTreeLists are joined together.
283 gencode (AbsCStmts c1 c2)
284 = gencode c1 `thenUs` \ b1 ->
285 gencode c2 `thenUs` \ b2 ->
290 Initialising closure headers in the heap...a fairly complex ordeal if
291 done properly. For now, we just set the info pointer, but we should
292 really take a peek at the flags to determine whether or not there are
293 other things to be done (setting cost centres, age headers, global
298 gencode (CInitHdr cl_info reg_rel _)
301 lbl = infoTableLabelFromCI cl_info
303 returnUs (\xs -> StAssign PtrRep (StInd PtrRep lhs) (StCLbl lbl) : xs)
311 gencode (CCheck macro args assts)
312 = gencode assts `thenUs` \assts_stix ->
313 checkCode macro args assts_stix
317 Assignment, the curse of von Neumann, is the center of the code we
318 produce. In most cases, the type of the assignment is determined
319 by the type of the destination. However, when the destination can
320 have mixed types, the type of the assignment is ``StgWord'' (we use
321 PtrRep for lack of anything better). Think: do we also want a cast
322 of the source? Be careful about floats/doubles.
326 gencode (CAssign lhs rhs)
327 | getAmodeRep lhs == VoidRep = returnUs id
329 = let pk = getAmodeRep lhs
330 pk' = if mixedTypeLocn lhs && not (isFloatingRep pk) then IntRep else pk
334 returnUs (\xs -> StAssign pk' lhs' rhs' : xs)
338 Unconditional jumps, including the special ``enter closure'' operation.
339 Note that the new entry convention requires that we load the InfoPtr (R2)
340 with the address of the info table before jumping to the entry code for Node.
342 For a vectored return, we must subtract the size of the info table to
343 get at the return vector. This depends on the size of the info table,
344 which varies depending on whether we're profiling etc.
349 = returnUs (\xs -> StJump NoDestInfo (a2stix dest) : xs)
351 gencode (CFallThrough (CLbl lbl _))
352 = returnUs (\xs -> StFallThrough lbl : xs)
354 gencode (CReturn dest DirectReturn)
355 = returnUs (\xs -> StJump NoDestInfo (a2stix dest) : xs)
357 gencode (CReturn table (StaticVectoredReturn n))
358 = returnUs (\xs -> StJump NoDestInfo dest : xs)
360 dest = StInd PtrRep (StIndex PtrRep (a2stix table)
361 (StInt (toInteger (-n-fixedItblSize-1))))
363 gencode (CReturn table (DynamicVectoredReturn am))
364 = returnUs (\xs -> StJump NoDestInfo dest : xs)
366 dest = StInd PtrRep (StIndex PtrRep (a2stix table) dyn_off)
367 dyn_off = StPrim IntSubOp [StPrim IntNegOp [a2stix am],
368 StInt (toInteger (fixedItblSize+1))]
372 Now the PrimOps, some of which may need caller-saves register wrappers.
376 gencode (COpStmt results op args vols)
377 -- ToDo (ADR?): use that liveness mask
378 | primOpNeedsWrapper op
380 saves = volsaves vols
381 restores = volrestores vols
383 p2stix (nonVoid results) op (nonVoid args)
385 returnUs (\xs -> saves ++ code (restores ++ xs))
387 | otherwise = p2stix (nonVoid results) op (nonVoid args)
389 nonVoid = filter ((/= VoidRep) . getAmodeRep)
393 Now the dreaded conditional jump.
395 Now the if statement. Almost *all* flow of control are of this form.
397 if (am==lit) { absC } else { absCdef }
411 gencode (CSwitch discrim alts deflt)
415 [(tag,alt_code)] -> case maybe_empty_deflt of
416 Nothing -> gencode alt_code
417 Just dc -> mkIfThenElse discrim tag alt_code dc
419 [(tag1@(MachInt i1), alt_code1),
420 (tag2@(MachInt i2), alt_code2)]
421 | deflt_is_empty && i1 == 0 && i2 == 1
422 -> mkIfThenElse discrim tag1 alt_code1 alt_code2
423 | deflt_is_empty && i1 == 1 && i2 == 0
424 -> mkIfThenElse discrim tag2 alt_code2 alt_code1
426 -- If the @discrim@ is simple, then this unfolding is safe.
427 other | simple_discrim -> mkSimpleSwitches discrim alts deflt
429 -- Otherwise, we need to do a bit of work.
430 other -> getUniqueUs `thenUs` \ u ->
432 (CAssign (CTemp u pk) discrim)
433 (CSwitch (CTemp u pk) alts deflt))
436 maybe_empty_deflt = nonemptyAbsC deflt
437 deflt_is_empty = case maybe_empty_deflt of
441 pk = getAmodeRep discrim
443 simple_discrim = case discrim of
451 Finally, all of the disgusting AbstractC macros.
455 gencode (CMacroStmt macro args) = macro_code macro args
457 gencode (CCallProfCtrMacro macro _)
458 = returnUs (\xs -> StComment macro : xs)
460 gencode (CCallProfCCMacro macro _)
461 = returnUs (\xs -> StComment macro : xs)
464 = pprPanic "AbsCStixGen.gencode" (dumpRealC other)
467 Here, we generate a jump table if there are more than four (integer)
468 alternatives and the jump table occupancy is greater than 50%.
469 Otherwise, we generate a binary comparison tree. (Perhaps this could
474 intTag :: Literal -> Integer
475 intTag (MachChar c) = toInteger c
476 intTag (MachInt i) = i
477 intTag (MachWord w) = intTag (word2IntLit (MachWord w))
478 intTag _ = panic "intTag"
480 fltTag :: Literal -> Rational
482 fltTag (MachFloat f) = f
483 fltTag (MachDouble d) = d
484 fltTag x = pprPanic "fltTag" (ppr x)
488 :: CAddrMode -> [(Literal,AbstractC)] -> AbstractC
489 -> UniqSM StixTreeList
491 mkSimpleSwitches am alts absC
492 = getUniqLabelNCG `thenUs` \ udlbl ->
493 getUniqLabelNCG `thenUs` \ ujlbl ->
495 joinedAlts = map (\ (tag,code) -> (tag, mkJoin code ujlbl)) alts
496 sortedAlts = naturalMergeSortLe leAlt joinedAlts
497 -- naturalMergeSortLe, because we often get sorted alts to begin with
499 lowTag = intTag (fst (head sortedAlts))
500 highTag = intTag (fst (last sortedAlts))
502 -- lowest and highest possible values the discriminant could take
503 lowest = if floating then targetMinDouble else targetMinInt
504 highest = if floating then targetMaxDouble else targetMaxInt
507 if not floating && choices > 4
508 && highTag - lowTag < toInteger (2 * choices)
510 mkJumpTable am' sortedAlts lowTag highTag udlbl
512 mkBinaryTree am' floating sortedAlts choices lowest highest udlbl
514 `thenUs` \ alt_code ->
515 gencode absC `thenUs` \ dflt_code ->
517 returnUs (\xs -> alt_code (StLabel udlbl : dflt_code (StLabel ujlbl : xs)))
520 floating = isFloatingRep (getAmodeRep am)
521 choices = length alts
523 (x@(MachChar _),_) `leAlt` (y,_) = intTag x <= intTag y
524 (x@(MachInt _), _) `leAlt` (y,_) = intTag x <= intTag y
525 (x@(MachWord _), _) `leAlt` (y,_) = intTag x <= intTag y
526 (x,_) `leAlt` (y,_) = fltTag x <= fltTag y
530 We use jump tables when doing an integer switch on a relatively dense
531 list of alternatives. We expect to be given a list of alternatives,
532 sorted by tag, and a range of values for which we are to generate a
533 table. Of course, the tags of the alternatives should lie within the
534 indicated range. The alternatives need not cover the range; a default
535 target is provided for the missing alternatives.
537 If a join is necessary after the switch, the alternatives should
538 already finish with a jump to the join point.
543 :: StixTree -- discriminant
544 -> [(Literal, AbstractC)] -- alternatives
545 -> Integer -- low tag
546 -> Integer -- high tag
547 -> CLabel -- default label
548 -> UniqSM StixTreeList
551 mkJumpTable am alts lowTag highTag dflt
552 = getUniqLabelNCG `thenUs` \ utlbl ->
553 mapUs genLabel alts `thenUs` \ branches ->
554 let cjmpLo = StCondJump dflt (StPrim IntLtOp [am, StInt (toInteger lowTag)])
555 cjmpHi = StCondJump dflt (StPrim IntGtOp [am, StInt (toInteger highTag)])
557 offset = StPrim IntSubOp [am, StInt lowTag]
558 dsts = DestInfo (dflt : map fst branches)
560 jump = StJump dsts (StInd PtrRep (StIndex PtrRep (StCLbl utlbl) offset))
562 table = StData PtrRep (mkTable branches [lowTag..highTag] [])
564 mapUs mkBranch branches `thenUs` \ alts ->
566 returnUs (\xs -> cjmpLo : cjmpHi : jump :
567 StSegment DataSegment : tlbl : table :
568 StSegment TextSegment : foldr1 (.) alts xs)
571 genLabel x = getUniqLabelNCG `thenUs` \ lbl -> returnUs (lbl, x)
573 mkBranch (lbl,(_,alt)) =
574 gencode alt `thenUs` \ alt_code ->
575 returnUs (\xs -> StLabel lbl : alt_code xs)
577 mkTable _ [] tbl = reverse tbl
578 mkTable [] (x:xs) tbl = mkTable [] xs (StCLbl dflt : tbl)
579 mkTable alts@((lbl,(tag,_)):rest) (x:xs) tbl
580 | intTag tag == x = mkTable rest xs (StCLbl lbl : tbl)
581 | otherwise = mkTable alts xs (StCLbl dflt : tbl)
585 We generate binary comparison trees when a jump table is inappropriate.
586 We expect to be given a list of alternatives, sorted by tag, and for
587 convenience, the length of the alternative list. We recursively break
588 the list in half and do a comparison on the first tag of the second half
589 of the list. (Odd lists are broken so that the second half of the list
590 is longer.) We can handle either integer or floating kind alternatives,
591 so long as they are not mixed. (We assume that the type of the discriminant
592 determines the type of the alternatives.)
594 As with the jump table approach, if a join is necessary after the switch, the
595 alternatives should already finish with a jump to the join point.
600 :: StixTree -- discriminant
601 -> Bool -- floating point?
602 -> [(Literal, AbstractC)] -- alternatives
603 -> Int -- number of choices
604 -> Literal -- low tag
605 -> Literal -- high tag
606 -> CLabel -- default code label
607 -> UniqSM StixTreeList
610 mkBinaryTree am floating [(tag,alt)] _ lowTag highTag udlbl
611 | rangeOfOne = gencode alt
613 = let tag' = a2stix (CLit tag)
614 cmpOp = if floating then DoubleNeOp else IntNeOp
615 test = StPrim cmpOp [am, tag']
616 cjmp = StCondJump udlbl test
618 gencode alt `thenUs` \ alt_code ->
619 returnUs (\xs -> cjmp : alt_code xs)
622 rangeOfOne = not floating && intTag lowTag + 1 >= intTag highTag
623 -- When there is only one possible tag left in range, we skip the comparison
625 mkBinaryTree am floating alts choices lowTag highTag udlbl
626 = getUniqLabelNCG `thenUs` \ uhlbl ->
627 let tag' = a2stix (CLit splitTag)
628 cmpOp = if floating then DoubleGeOp else IntGeOp
629 test = StPrim cmpOp [am, tag']
630 cjmp = StCondJump uhlbl test
632 mkBinaryTree am floating alts_lo half lowTag splitTag udlbl
633 `thenUs` \ lo_code ->
634 mkBinaryTree am floating alts_hi (choices - half) splitTag highTag udlbl
635 `thenUs` \ hi_code ->
637 returnUs (\xs -> cjmp : lo_code (StLabel uhlbl : hi_code xs))
640 half = choices `div` 2
641 (alts_lo, alts_hi) = splitAt half alts
642 splitTag = fst (head alts_hi)
649 :: CAddrMode -- discriminant
651 -> AbstractC -- if-part
652 -> AbstractC -- else-part
653 -> UniqSM StixTreeList
656 mkIfThenElse discrim tag alt deflt
657 = getUniqLabelNCG `thenUs` \ ujlbl ->
658 getUniqLabelNCG `thenUs` \ utlbl ->
659 let discrim' = a2stix discrim
660 tag' = a2stix (CLit tag)
661 cmpOp = if (isFloatingRep (getAmodeRep discrim)) then DoubleNeOp else IntNeOp
662 test = StPrim cmpOp [discrim', tag']
663 cjmp = StCondJump utlbl test
667 gencode (mkJoin alt ujlbl) `thenUs` \ alt_code ->
668 gencode deflt `thenUs` \ dflt_code ->
669 returnUs (\xs -> cjmp : alt_code (dest : dflt_code (join : xs)))
671 mkJoin :: AbstractC -> CLabel -> AbstractC
674 | mightFallThrough code = mkAbsCStmts code (CJump (CLbl lbl PtrRep))
678 %---------------------------------------------------------------------------
680 This answers the question: Can the code fall through to the next
681 line(s) of code? This errs towards saying True if it can't choose,
682 because it is used for eliminating needless jumps. In other words, if
683 you might possibly {\em not} jump, then say yes to falling through.
686 mightFallThrough :: AbstractC -> Bool
688 mightFallThrough absC = ft absC True
690 ft AbsCNop if_empty = if_empty
692 ft (CJump _) if_empty = False
693 ft (CReturn _ _) if_empty = False
694 ft (CSwitch _ alts deflt) if_empty
695 = ft deflt if_empty ||
696 or [ft alt if_empty | (_,alt) <- alts]
698 ft (AbsCStmts c1 c2) if_empty = ft c2 (ft c1 if_empty)
699 ft _ if_empty = if_empty
701 {- Old algorithm, which called nonemptyAbsC for every subexpression! =========
702 fallThroughAbsC (AbsCStmts c1 c2)
703 = case nonemptyAbsC c2 of
704 Nothing -> fallThroughAbsC c1
705 Just x -> fallThroughAbsC x
706 fallThroughAbsC (CJump _) = False
707 fallThroughAbsC (CReturn _ _) = False
708 fallThroughAbsC (CSwitch _ choices deflt)
709 = (not (isEmptyAbsC deflt) && fallThroughAbsC deflt)
710 || or (map (fallThroughAbsC . snd) choices)
711 fallThroughAbsC other = True
713 isEmptyAbsC :: AbstractC -> Bool
714 isEmptyAbsC = not . maybeToBool . nonemptyAbsC
715 ================= End of old, quadratic, algorithm -}