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 )
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 (\amode -> StData (getAmodeRep amode) [a2stix amode]) amodes ++
220 [StData PtrRep (padding_wds ++ static_link)]
222 -- always at least one padding word: this is the static link field
223 -- for the garbage collector.
224 padding_wds = if closureUpdReqd cl_info then
225 take (max 0 (mIN_UPD_SIZE - length amodes)) zeros
229 static_link | staticClosureNeedsLink cl_info = [StInt 0]
232 zeros = StInt 0 : zeros
235 -- Watch out for VoidKinds...cf. PprAbsC
237 | getAmodeRep item == VoidRep = StInt 0
238 | otherwise = a2stix item
243 Now the individual AbstractC statements.
249 -> UniqSM StixTreeList
253 @AbsCNop@s just disappear.
257 gencode AbsCNop = returnUs id
261 Split markers just insert a __stg_split_marker, which is caught by the
262 split-mangler later on and used to split the assembly into chunks.
266 gencode CSplitMarker = returnUs (\xs -> StLabel mkSplitMarkerLabel : xs)
270 AbstractC instruction sequences are handled individually, and the
271 resulting StixTreeLists are joined together.
275 gencode (AbsCStmts c1 c2)
276 = gencode c1 `thenUs` \ b1 ->
277 gencode c2 `thenUs` \ b2 ->
282 Initialising closure headers in the heap...a fairly complex ordeal if
283 done properly. For now, we just set the info pointer, but we should
284 really take a peek at the flags to determine whether or not there are
285 other things to be done (setting cost centres, age headers, global
290 gencode (CInitHdr cl_info reg_rel _)
293 lbl = infoTableLabelFromCI cl_info
295 returnUs (\xs -> StAssign PtrRep (StInd PtrRep lhs) (StCLbl lbl) : xs)
303 gencode (CCheck macro args assts)
304 = gencode assts `thenUs` \assts_stix ->
305 checkCode macro args assts_stix
309 Assignment, the curse of von Neumann, is the center of the code we
310 produce. In most cases, the type of the assignment is determined
311 by the type of the destination. However, when the destination can
312 have mixed types, the type of the assignment is ``StgWord'' (we use
313 PtrRep for lack of anything better). Think: do we also want a cast
314 of the source? Be careful about floats/doubles.
318 gencode (CAssign lhs rhs)
319 | getAmodeRep lhs == VoidRep = returnUs id
321 = let pk = getAmodeRep lhs
322 pk' = if mixedTypeLocn lhs && not (isFloatingRep pk) then IntRep else pk
326 returnUs (\xs -> StAssign pk' lhs' rhs' : xs)
330 Unconditional jumps, including the special ``enter closure'' operation.
331 Note that the new entry convention requires that we load the InfoPtr (R2)
332 with the address of the info table before jumping to the entry code for Node.
334 For a vectored return, we must subtract the size of the info table to
335 get at the return vector. This depends on the size of the info table,
336 which varies depending on whether we're profiling etc.
341 = returnUs (\xs -> StJump (a2stix dest) : xs)
343 gencode (CFallThrough (CLbl lbl _))
344 = returnUs (\xs -> StFallThrough lbl : xs)
346 gencode (CReturn dest DirectReturn)
347 = returnUs (\xs -> StJump (a2stix dest) : xs)
349 gencode (CReturn table (StaticVectoredReturn n))
350 = returnUs (\xs -> StJump dest : xs)
352 dest = StInd PtrRep (StIndex PtrRep (a2stix table)
353 (StInt (toInteger (-n-fixedItblSize-1))))
355 gencode (CReturn table (DynamicVectoredReturn am))
356 = returnUs (\xs -> StJump dest : xs)
358 dest = StInd PtrRep (StIndex PtrRep (a2stix table) dyn_off)
359 dyn_off = StPrim IntSubOp [StPrim IntNegOp [a2stix am],
360 StInt (toInteger (fixedItblSize+1))]
364 Now the PrimOps, some of which may need caller-saves register wrappers.
368 gencode (COpStmt results op args vols)
369 -- ToDo (ADR?): use that liveness mask
370 | primOpNeedsWrapper op
372 saves = volsaves vols
373 restores = volrestores vols
375 p2stix (nonVoid results) op (nonVoid args)
377 returnUs (\xs -> saves ++ code (restores ++ xs))
379 | otherwise = p2stix (nonVoid results) op (nonVoid args)
381 nonVoid = filter ((/= VoidRep) . getAmodeRep)
385 Now the dreaded conditional jump.
387 Now the if statement. Almost *all* flow of control are of this form.
389 if (am==lit) { absC } else { absCdef }
403 gencode (CSwitch discrim alts deflt)
407 [(tag,alt_code)] -> case maybe_empty_deflt of
408 Nothing -> gencode alt_code
409 Just dc -> mkIfThenElse discrim tag alt_code dc
411 [(tag1@(MachInt i1), alt_code1),
412 (tag2@(MachInt i2), alt_code2)]
413 | deflt_is_empty && i1 == 0 && i2 == 1
414 -> mkIfThenElse discrim tag1 alt_code1 alt_code2
415 | deflt_is_empty && i1 == 1 && i2 == 0
416 -> mkIfThenElse discrim tag2 alt_code2 alt_code1
418 -- If the @discrim@ is simple, then this unfolding is safe.
419 other | simple_discrim -> mkSimpleSwitches discrim alts deflt
421 -- Otherwise, we need to do a bit of work.
422 other -> getUniqueUs `thenUs` \ u ->
424 (CAssign (CTemp u pk) discrim)
425 (CSwitch (CTemp u pk) alts deflt))
428 maybe_empty_deflt = nonemptyAbsC deflt
429 deflt_is_empty = case maybe_empty_deflt of
433 pk = getAmodeRep discrim
435 simple_discrim = case discrim of
443 Finally, all of the disgusting AbstractC macros.
447 gencode (CMacroStmt macro args) = macro_code macro args
449 gencode (CCallProfCtrMacro macro _)
450 = returnUs (\xs -> StComment macro : xs)
452 gencode (CCallProfCCMacro macro _)
453 = returnUs (\xs -> StComment macro : xs)
456 = pprPanic "AbsCStixGen.gencode" (dumpRealC other)
459 Here, we generate a jump table if there are more than four (integer)
460 alternatives and the jump table occupancy is greater than 50%.
461 Otherwise, we generate a binary comparison tree. (Perhaps this could
466 intTag :: Literal -> Integer
467 intTag (MachChar c) = toInteger (ord c)
468 intTag (MachInt i) = i
469 intTag (MachWord w) = intTag (word2IntLit (MachWord w))
470 intTag _ = panic "intTag"
472 fltTag :: Literal -> Rational
474 fltTag (MachFloat f) = f
475 fltTag (MachDouble d) = d
476 fltTag x = pprPanic "fltTag" (ppr x)
480 :: CAddrMode -> [(Literal,AbstractC)] -> AbstractC
481 -> UniqSM StixTreeList
483 mkSimpleSwitches am alts absC
484 = getUniqLabelNCG `thenUs` \ udlbl ->
485 getUniqLabelNCG `thenUs` \ ujlbl ->
487 joinedAlts = map (\ (tag,code) -> (tag, mkJoin code ujlbl)) alts
488 sortedAlts = naturalMergeSortLe leAlt joinedAlts
489 -- naturalMergeSortLe, because we often get sorted alts to begin with
491 lowTag = intTag (fst (head sortedAlts))
492 highTag = intTag (fst (last sortedAlts))
494 -- lowest and highest possible values the discriminant could take
495 lowest = if floating then targetMinDouble else targetMinInt
496 highest = if floating then targetMaxDouble else targetMaxInt
499 if not floating && choices > 4 && highTag - lowTag < toInteger (2 * choices) then
500 mkJumpTable am' sortedAlts lowTag highTag udlbl
502 mkBinaryTree am' floating sortedAlts choices lowest highest udlbl
504 `thenUs` \ alt_code ->
505 gencode absC `thenUs` \ dflt_code ->
507 returnUs (\xs -> alt_code (StLabel udlbl : dflt_code (StLabel ujlbl : xs)))
510 floating = isFloatingRep (getAmodeRep am)
511 choices = length alts
513 (x@(MachChar _),_) `leAlt` (y,_) = intTag x <= intTag y
514 (x@(MachInt _), _) `leAlt` (y,_) = intTag x <= intTag y
515 (x@(MachWord _), _) `leAlt` (y,_) = intTag x <= intTag y
516 (x,_) `leAlt` (y,_) = fltTag x <= fltTag y
520 We use jump tables when doing an integer switch on a relatively dense
521 list of alternatives. We expect to be given a list of alternatives,
522 sorted by tag, and a range of values for which we are to generate a
523 table. Of course, the tags of the alternatives should lie within the
524 indicated range. The alternatives need not cover the range; a default
525 target is provided for the missing alternatives.
527 If a join is necessary after the switch, the alternatives should
528 already finish with a jump to the join point.
533 :: StixTree -- discriminant
534 -> [(Literal, AbstractC)] -- alternatives
535 -> Integer -- low tag
536 -> Integer -- high tag
537 -> CLabel -- default label
538 -> UniqSM StixTreeList
541 mkJumpTable am alts lowTag highTag dflt
542 = getUniqLabelNCG `thenUs` \ utlbl ->
543 mapUs genLabel alts `thenUs` \ branches ->
544 let cjmpLo = StCondJump dflt (StPrim IntLtOp [am, StInt (toInteger lowTag)])
545 cjmpHi = StCondJump dflt (StPrim IntGtOp [am, StInt (toInteger highTag)])
547 offset = StPrim IntSubOp [am, StInt lowTag]
549 jump = StJump (StInd PtrRep (StIndex PtrRep (StCLbl utlbl) offset))
551 table = StData PtrRep (mkTable branches [lowTag..highTag] [])
553 mapUs mkBranch branches `thenUs` \ alts ->
555 returnUs (\xs -> cjmpLo : cjmpHi : jump :
556 StSegment DataSegment : tlbl : table :
557 StSegment TextSegment : foldr1 (.) alts xs)
560 genLabel x = getUniqLabelNCG `thenUs` \ lbl -> returnUs (lbl, x)
562 mkBranch (lbl,(_,alt)) =
563 gencode alt `thenUs` \ alt_code ->
564 returnUs (\xs -> StLabel lbl : alt_code xs)
566 mkTable _ [] tbl = reverse tbl
567 mkTable [] (x:xs) tbl = mkTable [] xs (StCLbl dflt : tbl)
568 mkTable alts@((lbl,(tag,_)):rest) (x:xs) tbl
569 | intTag tag == x = mkTable rest xs (StCLbl lbl : tbl)
570 | otherwise = mkTable alts xs (StCLbl dflt : tbl)
574 We generate binary comparison trees when a jump table is inappropriate.
575 We expect to be given a list of alternatives, sorted by tag, and for
576 convenience, the length of the alternative list. We recursively break
577 the list in half and do a comparison on the first tag of the second half
578 of the list. (Odd lists are broken so that the second half of the list
579 is longer.) We can handle either integer or floating kind alternatives,
580 so long as they are not mixed. (We assume that the type of the discriminant
581 determines the type of the alternatives.)
583 As with the jump table approach, if a join is necessary after the switch, the
584 alternatives should already finish with a jump to the join point.
589 :: StixTree -- discriminant
590 -> Bool -- floating point?
591 -> [(Literal, AbstractC)] -- alternatives
592 -> Int -- number of choices
593 -> Literal -- low tag
594 -> Literal -- high tag
595 -> CLabel -- default code label
596 -> UniqSM StixTreeList
599 mkBinaryTree am floating [(tag,alt)] _ lowTag highTag udlbl
600 | rangeOfOne = gencode alt
602 = let tag' = a2stix (CLit tag)
603 cmpOp = if floating then DoubleNeOp else IntNeOp
604 test = StPrim cmpOp [am, tag']
605 cjmp = StCondJump udlbl test
607 gencode alt `thenUs` \ alt_code ->
608 returnUs (\xs -> cjmp : alt_code xs)
611 rangeOfOne = not floating && intTag lowTag + 1 >= intTag highTag
612 -- When there is only one possible tag left in range, we skip the comparison
614 mkBinaryTree am floating alts choices lowTag highTag udlbl
615 = getUniqLabelNCG `thenUs` \ uhlbl ->
616 let tag' = a2stix (CLit splitTag)
617 cmpOp = if floating then DoubleGeOp else IntGeOp
618 test = StPrim cmpOp [am, tag']
619 cjmp = StCondJump uhlbl test
621 mkBinaryTree am floating alts_lo half lowTag splitTag udlbl
622 `thenUs` \ lo_code ->
623 mkBinaryTree am floating alts_hi (choices - half) splitTag highTag udlbl
624 `thenUs` \ hi_code ->
626 returnUs (\xs -> cjmp : lo_code (StLabel uhlbl : hi_code xs))
629 half = choices `div` 2
630 (alts_lo, alts_hi) = splitAt half alts
631 splitTag = fst (head alts_hi)
638 :: CAddrMode -- discriminant
640 -> AbstractC -- if-part
641 -> AbstractC -- else-part
642 -> UniqSM StixTreeList
645 mkIfThenElse discrim tag alt deflt
646 = getUniqLabelNCG `thenUs` \ ujlbl ->
647 getUniqLabelNCG `thenUs` \ utlbl ->
648 let discrim' = a2stix discrim
649 tag' = a2stix (CLit tag)
650 cmpOp = if (isFloatingRep (getAmodeRep discrim)) then DoubleNeOp else IntNeOp
651 test = StPrim cmpOp [discrim', tag']
652 cjmp = StCondJump utlbl test
656 gencode (mkJoin alt ujlbl) `thenUs` \ alt_code ->
657 gencode deflt `thenUs` \ dflt_code ->
658 returnUs (\xs -> cjmp : alt_code (dest : dflt_code (join : xs)))
660 mkJoin :: AbstractC -> CLabel -> AbstractC
663 | mightFallThrough code = mkAbsCStmts code (CJump (CLbl lbl PtrRep))
667 %---------------------------------------------------------------------------
669 This answers the question: Can the code fall through to the next
670 line(s) of code? This errs towards saying True if it can't choose,
671 because it is used for eliminating needless jumps. In other words, if
672 you might possibly {\em not} jump, then say yes to falling through.
675 mightFallThrough :: AbstractC -> Bool
677 mightFallThrough absC = ft absC True
679 ft AbsCNop if_empty = if_empty
681 ft (CJump _) if_empty = False
682 ft (CReturn _ _) if_empty = False
683 ft (CSwitch _ alts deflt) if_empty
684 = ft deflt if_empty ||
685 or [ft alt if_empty | (_,alt) <- alts]
687 ft (AbsCStmts c1 c2) if_empty = ft c2 (ft c1 if_empty)
688 ft _ if_empty = if_empty
690 {- Old algorithm, which called nonemptyAbsC for every subexpression! =========
691 fallThroughAbsC (AbsCStmts c1 c2)
692 = case nonemptyAbsC c2 of
693 Nothing -> fallThroughAbsC c1
694 Just x -> fallThroughAbsC x
695 fallThroughAbsC (CJump _) = False
696 fallThroughAbsC (CReturn _ _) = False
697 fallThroughAbsC (CSwitch _ choices deflt)
698 = (not (isEmptyAbsC deflt) && fallThroughAbsC deflt)
699 || or (map (fallThroughAbsC . snd) choices)
700 fallThroughAbsC other = True
702 isEmptyAbsC :: AbstractC -> Bool
703 isEmptyAbsC = not . maybeToBool . nonemptyAbsC
704 ================= End of old, quadratic, algorithm -}