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 (\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.
267 | opt_EnsureSplittableC = returnUs (\xs -> StLabel mkSplitMarkerLabel : xs)
268 | otherwise = returnUs id
272 AbstractC instruction sequences are handled individually, and the
273 resulting StixTreeLists are joined together.
277 gencode (AbsCStmts c1 c2)
278 = gencode c1 `thenUs` \ b1 ->
279 gencode c2 `thenUs` \ b2 ->
284 Initialising closure headers in the heap...a fairly complex ordeal if
285 done properly. For now, we just set the info pointer, but we should
286 really take a peek at the flags to determine whether or not there are
287 other things to be done (setting cost centres, age headers, global
292 gencode (CInitHdr cl_info reg_rel _)
295 lbl = infoTableLabelFromCI cl_info
297 returnUs (\xs -> StAssign PtrRep (StInd PtrRep lhs) (StCLbl lbl) : xs)
305 gencode (CCheck macro args assts)
306 = gencode assts `thenUs` \assts_stix ->
307 checkCode macro args assts_stix
311 Assignment, the curse of von Neumann, is the center of the code we
312 produce. In most cases, the type of the assignment is determined
313 by the type of the destination. However, when the destination can
314 have mixed types, the type of the assignment is ``StgWord'' (we use
315 PtrRep for lack of anything better). Think: do we also want a cast
316 of the source? Be careful about floats/doubles.
320 gencode (CAssign lhs rhs)
321 | getAmodeRep lhs == VoidRep = returnUs id
323 = let pk = getAmodeRep lhs
324 pk' = if mixedTypeLocn lhs && not (isFloatingRep pk) then IntRep else pk
328 returnUs (\xs -> StAssign pk' lhs' rhs' : xs)
332 Unconditional jumps, including the special ``enter closure'' operation.
333 Note that the new entry convention requires that we load the InfoPtr (R2)
334 with the address of the info table before jumping to the entry code for Node.
336 For a vectored return, we must subtract the size of the info table to
337 get at the return vector. This depends on the size of the info table,
338 which varies depending on whether we're profiling etc.
343 = returnUs (\xs -> StJump (a2stix dest) : xs)
345 gencode (CFallThrough (CLbl lbl _))
346 = returnUs (\xs -> StFallThrough lbl : xs)
348 gencode (CReturn dest DirectReturn)
349 = returnUs (\xs -> StJump (a2stix dest) : xs)
351 gencode (CReturn table (StaticVectoredReturn n))
352 = returnUs (\xs -> StJump dest : xs)
354 dest = StInd PtrRep (StIndex PtrRep (a2stix table)
355 (StInt (toInteger (-n-fixedItblSize-1))))
357 gencode (CReturn table (DynamicVectoredReturn am))
358 = returnUs (\xs -> StJump dest : xs)
360 dest = StInd PtrRep (StIndex PtrRep (a2stix table) dyn_off)
361 dyn_off = StPrim IntSubOp [StPrim IntNegOp [a2stix am],
362 StInt (toInteger (fixedItblSize+1))]
366 Now the PrimOps, some of which may need caller-saves register wrappers.
370 gencode (COpStmt results op args vols)
371 -- ToDo (ADR?): use that liveness mask
372 | primOpNeedsWrapper op
374 saves = volsaves vols
375 restores = volrestores vols
377 p2stix (nonVoid results) op (nonVoid args)
379 returnUs (\xs -> saves ++ code (restores ++ xs))
381 | otherwise = p2stix (nonVoid results) op (nonVoid args)
383 nonVoid = filter ((/= VoidRep) . getAmodeRep)
387 Now the dreaded conditional jump.
389 Now the if statement. Almost *all* flow of control are of this form.
391 if (am==lit) { absC } else { absCdef }
405 gencode (CSwitch discrim alts deflt)
409 [(tag,alt_code)] -> case maybe_empty_deflt of
410 Nothing -> gencode alt_code
411 Just dc -> mkIfThenElse discrim tag alt_code dc
413 [(tag1@(MachInt i1), alt_code1),
414 (tag2@(MachInt i2), alt_code2)]
415 | deflt_is_empty && i1 == 0 && i2 == 1
416 -> mkIfThenElse discrim tag1 alt_code1 alt_code2
417 | deflt_is_empty && i1 == 1 && i2 == 0
418 -> mkIfThenElse discrim tag2 alt_code2 alt_code1
420 -- If the @discrim@ is simple, then this unfolding is safe.
421 other | simple_discrim -> mkSimpleSwitches discrim alts deflt
423 -- Otherwise, we need to do a bit of work.
424 other -> getUniqueUs `thenUs` \ u ->
426 (CAssign (CTemp u pk) discrim)
427 (CSwitch (CTemp u pk) alts deflt))
430 maybe_empty_deflt = nonemptyAbsC deflt
431 deflt_is_empty = case maybe_empty_deflt of
435 pk = getAmodeRep discrim
437 simple_discrim = case discrim of
445 Finally, all of the disgusting AbstractC macros.
449 gencode (CMacroStmt macro args) = macro_code macro args
451 gencode (CCallProfCtrMacro macro _)
452 = returnUs (\xs -> StComment macro : xs)
454 gencode (CCallProfCCMacro macro _)
455 = returnUs (\xs -> StComment macro : xs)
458 = pprPanic "AbsCStixGen.gencode" (dumpRealC other)
461 Here, we generate a jump table if there are more than four (integer)
462 alternatives and the jump table occupancy is greater than 50%.
463 Otherwise, we generate a binary comparison tree. (Perhaps this could
468 intTag :: Literal -> Integer
469 intTag (MachChar c) = toInteger (ord c)
470 intTag (MachInt i) = i
471 intTag (MachWord w) = intTag (word2IntLit (MachWord w))
472 intTag _ = panic "intTag"
474 fltTag :: Literal -> Rational
476 fltTag (MachFloat f) = f
477 fltTag (MachDouble d) = d
478 fltTag x = pprPanic "fltTag" (ppr x)
482 :: CAddrMode -> [(Literal,AbstractC)] -> AbstractC
483 -> UniqSM StixTreeList
485 mkSimpleSwitches am alts absC
486 = getUniqLabelNCG `thenUs` \ udlbl ->
487 getUniqLabelNCG `thenUs` \ ujlbl ->
489 joinedAlts = map (\ (tag,code) -> (tag, mkJoin code ujlbl)) alts
490 sortedAlts = naturalMergeSortLe leAlt joinedAlts
491 -- naturalMergeSortLe, because we often get sorted alts to begin with
493 lowTag = intTag (fst (head sortedAlts))
494 highTag = intTag (fst (last sortedAlts))
496 -- lowest and highest possible values the discriminant could take
497 lowest = if floating then targetMinDouble else targetMinInt
498 highest = if floating then targetMaxDouble else targetMaxInt
501 if not floating && choices > 4 && highTag - lowTag < toInteger (2 * choices) then
502 mkJumpTable am' sortedAlts lowTag highTag udlbl
504 mkBinaryTree am' floating sortedAlts choices lowest highest udlbl
506 `thenUs` \ alt_code ->
507 gencode absC `thenUs` \ dflt_code ->
509 returnUs (\xs -> alt_code (StLabel udlbl : dflt_code (StLabel ujlbl : xs)))
512 floating = isFloatingRep (getAmodeRep am)
513 choices = length alts
515 (x@(MachChar _),_) `leAlt` (y,_) = intTag x <= intTag y
516 (x@(MachInt _), _) `leAlt` (y,_) = intTag x <= intTag y
517 (x@(MachWord _), _) `leAlt` (y,_) = intTag x <= intTag y
518 (x,_) `leAlt` (y,_) = fltTag x <= fltTag y
522 We use jump tables when doing an integer switch on a relatively dense
523 list of alternatives. We expect to be given a list of alternatives,
524 sorted by tag, and a range of values for which we are to generate a
525 table. Of course, the tags of the alternatives should lie within the
526 indicated range. The alternatives need not cover the range; a default
527 target is provided for the missing alternatives.
529 If a join is necessary after the switch, the alternatives should
530 already finish with a jump to the join point.
535 :: StixTree -- discriminant
536 -> [(Literal, AbstractC)] -- alternatives
537 -> Integer -- low tag
538 -> Integer -- high tag
539 -> CLabel -- default label
540 -> UniqSM StixTreeList
543 mkJumpTable am alts lowTag highTag dflt
544 = getUniqLabelNCG `thenUs` \ utlbl ->
545 mapUs genLabel alts `thenUs` \ branches ->
546 let cjmpLo = StCondJump dflt (StPrim IntLtOp [am, StInt (toInteger lowTag)])
547 cjmpHi = StCondJump dflt (StPrim IntGtOp [am, StInt (toInteger highTag)])
549 offset = StPrim IntSubOp [am, StInt lowTag]
551 jump = StJump (StInd PtrRep (StIndex PtrRep (StCLbl utlbl) offset))
553 table = StData PtrRep (mkTable branches [lowTag..highTag] [])
555 mapUs mkBranch branches `thenUs` \ alts ->
557 returnUs (\xs -> cjmpLo : cjmpHi : jump :
558 StSegment DataSegment : tlbl : table :
559 StSegment TextSegment : foldr1 (.) alts xs)
562 genLabel x = getUniqLabelNCG `thenUs` \ lbl -> returnUs (lbl, x)
564 mkBranch (lbl,(_,alt)) =
565 gencode alt `thenUs` \ alt_code ->
566 returnUs (\xs -> StLabel lbl : alt_code xs)
568 mkTable _ [] tbl = reverse tbl
569 mkTable [] (x:xs) tbl = mkTable [] xs (StCLbl dflt : tbl)
570 mkTable alts@((lbl,(tag,_)):rest) (x:xs) tbl
571 | intTag tag == x = mkTable rest xs (StCLbl lbl : tbl)
572 | otherwise = mkTable alts xs (StCLbl dflt : tbl)
576 We generate binary comparison trees when a jump table is inappropriate.
577 We expect to be given a list of alternatives, sorted by tag, and for
578 convenience, the length of the alternative list. We recursively break
579 the list in half and do a comparison on the first tag of the second half
580 of the list. (Odd lists are broken so that the second half of the list
581 is longer.) We can handle either integer or floating kind alternatives,
582 so long as they are not mixed. (We assume that the type of the discriminant
583 determines the type of the alternatives.)
585 As with the jump table approach, if a join is necessary after the switch, the
586 alternatives should already finish with a jump to the join point.
591 :: StixTree -- discriminant
592 -> Bool -- floating point?
593 -> [(Literal, AbstractC)] -- alternatives
594 -> Int -- number of choices
595 -> Literal -- low tag
596 -> Literal -- high tag
597 -> CLabel -- default code label
598 -> UniqSM StixTreeList
601 mkBinaryTree am floating [(tag,alt)] _ lowTag highTag udlbl
602 | rangeOfOne = gencode alt
604 = let tag' = a2stix (CLit tag)
605 cmpOp = if floating then DoubleNeOp else IntNeOp
606 test = StPrim cmpOp [am, tag']
607 cjmp = StCondJump udlbl test
609 gencode alt `thenUs` \ alt_code ->
610 returnUs (\xs -> cjmp : alt_code xs)
613 rangeOfOne = not floating && intTag lowTag + 1 >= intTag highTag
614 -- When there is only one possible tag left in range, we skip the comparison
616 mkBinaryTree am floating alts choices lowTag highTag udlbl
617 = getUniqLabelNCG `thenUs` \ uhlbl ->
618 let tag' = a2stix (CLit splitTag)
619 cmpOp = if floating then DoubleGeOp else IntGeOp
620 test = StPrim cmpOp [am, tag']
621 cjmp = StCondJump uhlbl test
623 mkBinaryTree am floating alts_lo half lowTag splitTag udlbl
624 `thenUs` \ lo_code ->
625 mkBinaryTree am floating alts_hi (choices - half) splitTag highTag udlbl
626 `thenUs` \ hi_code ->
628 returnUs (\xs -> cjmp : lo_code (StLabel uhlbl : hi_code xs))
631 half = choices `div` 2
632 (alts_lo, alts_hi) = splitAt half alts
633 splitTag = fst (head alts_hi)
640 :: CAddrMode -- discriminant
642 -> AbstractC -- if-part
643 -> AbstractC -- else-part
644 -> UniqSM StixTreeList
647 mkIfThenElse discrim tag alt deflt
648 = getUniqLabelNCG `thenUs` \ ujlbl ->
649 getUniqLabelNCG `thenUs` \ utlbl ->
650 let discrim' = a2stix discrim
651 tag' = a2stix (CLit tag)
652 cmpOp = if (isFloatingRep (getAmodeRep discrim)) then DoubleNeOp else IntNeOp
653 test = StPrim cmpOp [discrim', tag']
654 cjmp = StCondJump utlbl test
658 gencode (mkJoin alt ujlbl) `thenUs` \ alt_code ->
659 gencode deflt `thenUs` \ dflt_code ->
660 returnUs (\xs -> cjmp : alt_code (dest : dflt_code (join : xs)))
662 mkJoin :: AbstractC -> CLabel -> AbstractC
665 | mightFallThrough code = mkAbsCStmts code (CJump (CLbl lbl PtrRep))
669 %---------------------------------------------------------------------------
671 This answers the question: Can the code fall through to the next
672 line(s) of code? This errs towards saying True if it can't choose,
673 because it is used for eliminating needless jumps. In other words, if
674 you might possibly {\em not} jump, then say yes to falling through.
677 mightFallThrough :: AbstractC -> Bool
679 mightFallThrough absC = ft absC True
681 ft AbsCNop if_empty = if_empty
683 ft (CJump _) if_empty = False
684 ft (CReturn _ _) if_empty = False
685 ft (CSwitch _ alts deflt) if_empty
686 = ft deflt if_empty ||
687 or [ft alt if_empty | (_,alt) <- alts]
689 ft (AbsCStmts c1 c2) if_empty = ft c2 (ft c1 if_empty)
690 ft _ if_empty = if_empty
692 {- Old algorithm, which called nonemptyAbsC for every subexpression! =========
693 fallThroughAbsC (AbsCStmts c1 c2)
694 = case nonemptyAbsC c2 of
695 Nothing -> fallThroughAbsC c1
696 Just x -> fallThroughAbsC x
697 fallThroughAbsC (CJump _) = False
698 fallThroughAbsC (CReturn _ _) = False
699 fallThroughAbsC (CSwitch _ choices deflt)
700 = (not (isEmptyAbsC deflt) && fallThroughAbsC deflt)
701 || or (map (fallThroughAbsC . snd) choices)
702 fallThroughAbsC other = True
704 isEmptyAbsC :: AbstractC -> Bool
705 isEmptyAbsC = not . maybeToBool . nonemptyAbsC
706 ================= End of old, quadratic, algorithm -}