1 -----------------------------------------------------------------------------
3 -- Code generator utilities; mostly monadic
5 -- (c) The University of Glasgow 2004-2006
7 -----------------------------------------------------------------------------
11 emitDataLits, mkDataLits,
12 emitRODataLits, mkRODataLits,
13 emitRtsCall, emitRtsCallWithVols, emitRtsCallWithResult,
14 assignTemp, newTemp, withTemp,
18 mkMultiAssign, mkCmmSwitch, mkCmmLitSwitch,
21 tagToClosure, mkTaggedObjectLoad,
23 callerSaveVolatileRegs, get_GlobalReg_addr,
25 cmmAndWord, cmmOrWord, cmmNegate, cmmEqWord, cmmNeWord,
27 cmmOffsetExprW, cmmOffsetExprB,
28 cmmRegOffW, cmmRegOffB,
29 cmmLabelOffW, cmmLabelOffB,
30 cmmOffsetW, cmmOffsetB,
31 cmmOffsetLitW, cmmOffsetLitB,
33 cmmConstrTag, cmmConstrTag1,
35 cmmUntag, cmmIsTagged, cmmGetTag,
37 addToMem, addToMemE, addToMemLbl,
39 mkStringCLit, mkByteStringCLit,
43 getSRTInfo, clHasCafRefs, srt_escape
46 #include "HsVersions.h"
47 #include "../includes/stg/MachRegs.h"
56 import PprCmm ( {- instances -} )
64 import StgSyn ( SRT(..) )
80 -------------------------------------------------------------------------
84 -------------------------------------------------------------------------
86 cgLit :: Literal -> FCode CmmLit
87 cgLit (MachStr s) = mkByteStringCLit (bytesFS s)
88 -- not unpackFS; we want the UTF-8 byte stream.
89 cgLit other_lit = return (mkSimpleLit other_lit)
91 mkSimpleLit :: Literal -> CmmLit
92 mkSimpleLit (MachChar c) = CmmInt (fromIntegral (ord c)) wordWidth
93 mkSimpleLit MachNullAddr = zeroCLit
94 mkSimpleLit (MachInt i) = CmmInt i wordWidth
95 mkSimpleLit (MachInt64 i) = CmmInt i W64
96 mkSimpleLit (MachWord i) = CmmInt i wordWidth
97 mkSimpleLit (MachWord64 i) = CmmInt i W64
98 mkSimpleLit (MachFloat r) = CmmFloat r W32
99 mkSimpleLit (MachDouble r) = CmmFloat r W64
100 mkSimpleLit (MachLabel fs ms fod) = CmmLabel (mkForeignLabel fs ms is_dyn fod)
102 is_dyn = False -- ToDo: fix me
103 mkSimpleLit other = pprPanic "mkSimpleLit" (ppr other)
105 mkLtOp :: Literal -> MachOp
106 -- On signed literals we must do a signed comparison
107 mkLtOp (MachInt _) = MO_S_Lt wordWidth
108 mkLtOp (MachFloat _) = MO_F_Lt W32
109 mkLtOp (MachDouble _) = MO_F_Lt W64
110 mkLtOp lit = MO_U_Lt (typeWidth (cmmLitType (mkSimpleLit lit)))
111 -- ToDo: seems terribly indirect!
114 ---------------------------------------------------
116 -- Cmm data type functions
118 ---------------------------------------------------
120 -- The "B" variants take byte offsets
121 cmmRegOffB :: CmmReg -> ByteOff -> CmmExpr
122 cmmRegOffB = cmmRegOff
124 cmmOffsetB :: CmmExpr -> ByteOff -> CmmExpr
125 cmmOffsetB = cmmOffset
127 cmmOffsetExprB :: CmmExpr -> CmmExpr -> CmmExpr
128 cmmOffsetExprB = cmmOffsetExpr
130 cmmLabelOffB :: CLabel -> ByteOff -> CmmLit
131 cmmLabelOffB = cmmLabelOff
133 cmmOffsetLitB :: CmmLit -> ByteOff -> CmmLit
134 cmmOffsetLitB = cmmOffsetLit
136 -----------------------
137 -- The "W" variants take word offsets
138 cmmOffsetExprW :: CmmExpr -> CmmExpr -> CmmExpr
139 -- The second arg is a *word* offset; need to change it to bytes
140 cmmOffsetExprW e (CmmLit (CmmInt n _)) = cmmOffsetW e (fromInteger n)
141 cmmOffsetExprW e wd_off = cmmIndexExpr wordWidth e wd_off
143 cmmOffsetW :: CmmExpr -> WordOff -> CmmExpr
144 cmmOffsetW e n = cmmOffsetB e (wORD_SIZE * n)
146 cmmRegOffW :: CmmReg -> WordOff -> CmmExpr
147 cmmRegOffW reg wd_off = cmmRegOffB reg (wd_off * wORD_SIZE)
149 cmmOffsetLitW :: CmmLit -> WordOff -> CmmLit
150 cmmOffsetLitW lit wd_off = cmmOffsetLitB lit (wORD_SIZE * wd_off)
152 cmmLabelOffW :: CLabel -> WordOff -> CmmLit
153 cmmLabelOffW lbl wd_off = cmmLabelOffB lbl (wORD_SIZE * wd_off)
155 cmmLoadIndexW :: CmmExpr -> Int -> CmmType -> CmmExpr
156 cmmLoadIndexW base off ty = CmmLoad (cmmOffsetW base off) ty
158 -----------------------
159 cmmULtWord, cmmUGeWord, cmmUGtWord, cmmSubWord,
160 cmmNeWord, cmmEqWord, cmmOrWord, cmmAndWord
161 :: CmmExpr -> CmmExpr -> CmmExpr
162 cmmOrWord e1 e2 = CmmMachOp mo_wordOr [e1, e2]
163 cmmAndWord e1 e2 = CmmMachOp mo_wordAnd [e1, e2]
164 cmmNeWord e1 e2 = CmmMachOp mo_wordNe [e1, e2]
165 cmmEqWord e1 e2 = CmmMachOp mo_wordEq [e1, e2]
166 cmmULtWord e1 e2 = CmmMachOp mo_wordULt [e1, e2]
167 cmmUGeWord e1 e2 = CmmMachOp mo_wordUGe [e1, e2]
168 cmmUGtWord e1 e2 = CmmMachOp mo_wordUGt [e1, e2]
169 --cmmShlWord e1 e2 = CmmMachOp mo_wordShl [e1, e2]
170 --cmmUShrWord e1 e2 = CmmMachOp mo_wordUShr [e1, e2]
171 cmmSubWord e1 e2 = CmmMachOp mo_wordSub [e1, e2]
173 cmmNegate :: CmmExpr -> CmmExpr
174 cmmNegate (CmmLit (CmmInt n rep)) = CmmLit (CmmInt (-n) rep)
175 cmmNegate e = CmmMachOp (MO_S_Neg (cmmExprWidth e)) [e]
177 blankWord :: CmmStatic
178 blankWord = CmmUninitialised wORD_SIZE
182 --cmmTagBits = CmmLit (mkIntCLit tAG_BITS)
183 cmmTagMask, cmmPointerMask :: CmmExpr
184 cmmTagMask = CmmLit (mkIntCLit tAG_MASK)
185 cmmPointerMask = CmmLit (mkIntCLit (complement tAG_MASK))
187 -- Used to untag a possibly tagged pointer
188 -- A static label need not be untagged
189 cmmUntag, cmmGetTag :: CmmExpr -> CmmExpr
190 cmmUntag e@(CmmLit (CmmLabel _)) = e
192 cmmUntag e = (e `cmmAndWord` cmmPointerMask)
194 cmmGetTag e = (e `cmmAndWord` cmmTagMask)
196 -- Test if a closure pointer is untagged
197 cmmIsTagged :: CmmExpr -> CmmExpr
198 cmmIsTagged e = (e `cmmAndWord` cmmTagMask)
199 `cmmNeWord` CmmLit zeroCLit
201 cmmConstrTag, cmmConstrTag1 :: CmmExpr -> CmmExpr
202 cmmConstrTag e = (e `cmmAndWord` cmmTagMask) `cmmSubWord` (CmmLit (mkIntCLit 1))
203 -- Get constructor tag, but one based.
204 cmmConstrTag1 e = e `cmmAndWord` cmmTagMask
206 -----------------------
209 mkWordCLit :: StgWord -> CmmLit
210 mkWordCLit wd = CmmInt (fromIntegral wd) wordWidth
212 packHalfWordsCLit :: (Integral a, Integral b) => a -> b -> CmmLit
213 -- Make a single word literal in which the lower_half_word is
214 -- at the lower address, and the upper_half_word is at the
216 -- ToDo: consider using half-word lits instead
217 -- but be careful: that's vulnerable when reversed
218 packHalfWordsCLit lower_half_word upper_half_word
219 #ifdef WORDS_BIGENDIAN
220 = mkWordCLit ((fromIntegral lower_half_word `shiftL` hALF_WORD_SIZE_IN_BITS)
221 .|. fromIntegral upper_half_word)
223 = mkWordCLit ((fromIntegral lower_half_word)
224 .|. (fromIntegral upper_half_word `shiftL` hALF_WORD_SIZE_IN_BITS))
227 --------------------------------------------------------------------------
229 -- Incrementing a memory location
231 --------------------------------------------------------------------------
233 addToMemLbl :: CmmType -> CLabel -> Int -> CmmAGraph
234 addToMemLbl rep lbl n = addToMem rep (CmmLit (CmmLabel lbl)) n
236 addToMem :: CmmType -- rep of the counter
237 -> CmmExpr -- Address
238 -> Int -- What to add (a word)
240 addToMem rep ptr n = addToMemE rep ptr (CmmLit (CmmInt (toInteger n) (typeWidth rep)))
242 addToMemE :: CmmType -- rep of the counter
243 -> CmmExpr -- Address
244 -> CmmExpr -- What to add (a word-typed expression)
247 = mkStore ptr (CmmMachOp (MO_Add (typeWidth rep)) [CmmLoad ptr rep, n])
250 -------------------------------------------------------------------------
252 -- Loading a field from an object,
253 -- where the object pointer is itself tagged
255 -------------------------------------------------------------------------
257 mkTaggedObjectLoad :: LocalReg -> LocalReg -> WordOff -> DynTag -> CmmAGraph
258 -- (loadTaggedObjectField reg base off tag) generates assignment
259 -- reg = bitsK[ base + off - tag ]
260 -- where K is fixed by 'reg'
261 mkTaggedObjectLoad reg base offset tag
262 = mkAssign (CmmLocal reg)
263 (CmmLoad (cmmOffsetB (CmmReg (CmmLocal base))
264 (wORD_SIZE*offset - tag))
267 -------------------------------------------------------------------------
269 -- Converting a closure tag to a closure for enumeration types
270 -- (this is the implementation of tagToEnum#).
272 -------------------------------------------------------------------------
274 tagToClosure :: TyCon -> CmmExpr -> CmmExpr
275 tagToClosure tycon tag
276 = CmmLoad (cmmOffsetExprW closure_tbl tag) bWord
277 where closure_tbl = CmmLit (CmmLabel lbl)
278 lbl = mkClosureTableLabel (tyConName tycon) NoCafRefs
280 -------------------------------------------------------------------------
282 -- Conditionals and rts calls
284 -------------------------------------------------------------------------
286 emitRtsCall :: LitString -> [(CmmExpr,ForeignHint)] -> Bool -> FCode ()
287 emitRtsCall fun args safe = emitRtsCall' [] fun args Nothing safe
288 -- The 'Nothing' says "save all global registers"
290 emitRtsCallWithVols :: LitString -> [(CmmExpr,ForeignHint)] -> [GlobalReg] -> Bool -> FCode ()
291 emitRtsCallWithVols fun args vols safe
292 = emitRtsCall' [] fun args (Just vols) safe
294 emitRtsCallWithResult :: LocalReg -> ForeignHint -> LitString
295 -> [(CmmExpr,ForeignHint)] -> Bool -> FCode ()
296 emitRtsCallWithResult res hint fun args safe
297 = emitRtsCall' [(res,hint)] fun args Nothing safe
299 -- Make a call to an RTS C procedure
301 :: [(LocalReg,ForeignHint)]
303 -> [(CmmExpr,ForeignHint)]
305 -> Bool -- True <=> CmmSafe call
307 emitRtsCall' res fun args _vols safe
308 = --error "emitRtsCall'"
309 do { updfr_off <- getUpdFrameOff
311 ; emit $ call updfr_off
316 mkCmmCall fun_expr res' args' updfr_off
318 mkUnsafeCall (ForeignTarget fun_expr
319 (ForeignConvention CCallConv arg_hints res_hints)) res' args'
320 (args', arg_hints) = unzip args
321 (res', res_hints) = unzip res
322 (caller_save, caller_load) = callerSaveVolatileRegs
323 fun_expr = mkLblExpr (mkRtsCodeLabel fun)
326 -----------------------------------------------------------------------------
328 -- Caller-Save Registers
330 -----------------------------------------------------------------------------
332 -- Here we generate the sequence of saves/restores required around a
333 -- foreign call instruction.
335 -- TODO: reconcile with includes/Regs.h
336 -- * Regs.h claims that BaseReg should be saved last and loaded first
337 -- * This might not have been tickled before since BaseReg is callee save
338 -- * Regs.h saves SparkHd, ParkT1, SparkBase and SparkLim
339 callerSaveVolatileRegs :: (CmmAGraph, CmmAGraph)
340 callerSaveVolatileRegs = (caller_save, caller_load)
342 caller_save = catAGraphs (map callerSaveGlobalReg regs_to_save)
343 caller_load = catAGraphs (map callerRestoreGlobalReg regs_to_save)
345 system_regs = [ Sp,SpLim,Hp,HpLim,CurrentTSO,CurrentNursery
346 {- ,SparkHd,SparkTl,SparkBase,SparkLim -}
349 regs_to_save = filter callerSaves system_regs
351 callerSaveGlobalReg reg
352 = mkStore (get_GlobalReg_addr reg) (CmmReg (CmmGlobal reg))
354 callerRestoreGlobalReg reg
355 = mkAssign (CmmGlobal reg)
356 (CmmLoad (get_GlobalReg_addr reg) (globalRegType reg))
358 -- -----------------------------------------------------------------------------
361 -- We map STG registers onto appropriate CmmExprs. Either they map
362 -- to real machine registers or stored as offsets from BaseReg. Given
363 -- a GlobalReg, get_GlobalReg_addr always produces the
364 -- register table address for it.
365 -- (See also get_GlobalReg_reg_or_addr in MachRegs)
367 get_GlobalReg_addr :: GlobalReg -> CmmExpr
368 get_GlobalReg_addr BaseReg = regTableOffset 0
369 get_GlobalReg_addr mid = get_Regtable_addr_from_offset
370 (globalRegType mid) (baseRegOffset mid)
372 -- Calculate a literal representing an offset into the register table.
373 -- Used when we don't have an actual BaseReg to offset from.
374 regTableOffset :: Int -> CmmExpr
376 CmmLit (CmmLabelOff mkMainCapabilityLabel (oFFSET_Capability_r + n))
378 get_Regtable_addr_from_offset :: CmmType -> Int -> CmmExpr
379 get_Regtable_addr_from_offset _rep offset =
381 CmmRegOff (CmmGlobal BaseReg) offset
383 regTableOffset offset
387 -- | Returns 'True' if this global register is stored in a caller-saves
390 callerSaves :: GlobalReg -> Bool
392 #ifdef CALLER_SAVES_Base
393 callerSaves BaseReg = True
395 #ifdef CALLER_SAVES_Sp
396 callerSaves Sp = True
398 #ifdef CALLER_SAVES_SpLim
399 callerSaves SpLim = True
401 #ifdef CALLER_SAVES_Hp
402 callerSaves Hp = True
404 #ifdef CALLER_SAVES_HpLim
405 callerSaves HpLim = True
407 #ifdef CALLER_SAVES_CurrentTSO
408 callerSaves CurrentTSO = True
410 #ifdef CALLER_SAVES_CurrentNursery
411 callerSaves CurrentNursery = True
413 callerSaves _ = False
416 -- -----------------------------------------------------------------------------
417 -- Information about global registers
419 baseRegOffset :: GlobalReg -> Int
421 baseRegOffset Sp = oFFSET_StgRegTable_rSp
422 baseRegOffset SpLim = oFFSET_StgRegTable_rSpLim
423 baseRegOffset (LongReg 1) = oFFSET_StgRegTable_rL1
424 baseRegOffset Hp = oFFSET_StgRegTable_rHp
425 baseRegOffset HpLim = oFFSET_StgRegTable_rHpLim
426 baseRegOffset CurrentTSO = oFFSET_StgRegTable_rCurrentTSO
427 baseRegOffset CurrentNursery = oFFSET_StgRegTable_rCurrentNursery
428 baseRegOffset HpAlloc = oFFSET_StgRegTable_rHpAlloc
429 baseRegOffset GCEnter1 = oFFSET_stgGCEnter1
430 baseRegOffset GCFun = oFFSET_stgGCFun
431 baseRegOffset reg = pprPanic "baseRegOffset:" (ppr reg)
433 -------------------------------------------------------------------------
435 -- Strings generate a top-level data block
437 -------------------------------------------------------------------------
439 emitDataLits :: CLabel -> [CmmLit] -> FCode ()
440 -- Emit a data-segment data block
441 emitDataLits lbl lits
442 = emitData Data (CmmDataLabel lbl : map CmmStaticLit lits)
444 mkDataLits :: CLabel -> [CmmLit] -> GenCmmTop CmmStatic info stmt
445 -- Emit a data-segment data block
447 = CmmData Data (CmmDataLabel lbl : map CmmStaticLit lits)
449 emitRODataLits :: CLabel -> [CmmLit] -> FCode ()
450 -- Emit a read-only data block
451 emitRODataLits lbl lits
452 = emitData section (CmmDataLabel lbl : map CmmStaticLit lits)
453 where section | any needsRelocation lits = RelocatableReadOnlyData
454 | otherwise = ReadOnlyData
455 needsRelocation (CmmLabel _) = True
456 needsRelocation (CmmLabelOff _ _) = True
457 needsRelocation _ = False
459 mkRODataLits :: CLabel -> [CmmLit] -> GenCmmTop CmmStatic info stmt
460 mkRODataLits lbl lits
461 = CmmData section (CmmDataLabel lbl : map CmmStaticLit lits)
462 where section | any needsRelocation lits = RelocatableReadOnlyData
463 | otherwise = ReadOnlyData
464 needsRelocation (CmmLabel _) = True
465 needsRelocation (CmmLabelOff _ _) = True
466 needsRelocation _ = False
468 mkStringCLit :: String -> FCode CmmLit
469 -- Make a global definition for the string,
470 -- and return its label
471 mkStringCLit str = mkByteStringCLit (map (fromIntegral . ord) str)
473 mkByteStringCLit :: [Word8] -> FCode CmmLit
474 mkByteStringCLit bytes
475 = do { uniq <- newUnique
476 ; let lbl = mkStringLitLabel uniq
477 ; emitData ReadOnlyData [CmmDataLabel lbl, CmmString bytes]
478 ; return (CmmLabel lbl) }
480 -------------------------------------------------------------------------
482 -- Assigning expressions to temporaries
484 -------------------------------------------------------------------------
486 assignTemp :: CmmExpr -> FCode LocalReg
487 -- Make sure the argument is in a local register
488 assignTemp (CmmReg (CmmLocal reg)) = return reg
489 assignTemp e = do { uniq <- newUnique
490 ; let reg = LocalReg uniq (cmmExprType e)
491 ; emit (mkAssign (CmmLocal reg) e)
494 newTemp :: CmmType -> FCode LocalReg
495 newTemp rep = do { uniq <- newUnique
496 ; return (LocalReg uniq rep) }
498 newUnboxedTupleRegs :: Type -> FCode ([LocalReg], [ForeignHint])
499 -- Choose suitable local regs to use for the components
500 -- of an unboxed tuple that we are about to return to
501 -- the Sequel. If the Sequel is a joint point, using the
502 -- regs it wants will save later assignments.
503 newUnboxedTupleRegs res_ty
504 = ASSERT( isUnboxedTupleType res_ty )
505 do { sequel <- getSequel
506 ; regs <- choose_regs sequel
507 ; ASSERT( regs `equalLength` reps )
508 return (regs, map primRepForeignHint reps) }
510 ty_args = tyConAppArgs (repType res_ty)
513 , let rep = typePrimRep ty
514 , not (isVoidRep rep) ]
515 choose_regs (AssignTo regs _) = return regs
516 choose_regs _other = mapM (newTemp . primRepCmmType) reps
520 -------------------------------------------------------------------------
522 -------------------------------------------------------------------------
524 mkMultiAssign :: [LocalReg] -> [CmmExpr] -> CmmAGraph
525 -- Emit code to perform the assignments in the
526 -- input simultaneously, using temporary variables when necessary.
529 type Vrtx = (Key, Stmt) -- Give each vertex a unique number,
530 -- for fast comparison
531 type Stmt = (LocalReg, CmmExpr) -- r := e
533 -- We use the strongly-connected component algorithm, in which
534 -- * the vertices are the statements
535 -- * an edge goes from s1 to s2 iff
536 -- s1 assigns to something s2 uses
537 -- that is, if s1 should *follow* s2 in the final order
539 mkMultiAssign [] [] = mkNop
540 mkMultiAssign [reg] [rhs] = mkAssign (CmmLocal reg) rhs
541 mkMultiAssign regs rhss = ASSERT( equalLength regs rhss )
542 unscramble ([1..] `zip` (regs `zip` rhss))
544 unscramble :: [Vrtx] -> CmmAGraph
546 = catAGraphs (map do_component components)
548 edges :: [ (Vrtx, Key, [Key]) ]
549 edges = [ (vertex, key1, edges_from stmt1)
550 | vertex@(key1, stmt1) <- vertices ]
552 edges_from :: Stmt -> [Key]
553 edges_from stmt1 = [ key2 | (key2, stmt2) <- vertices,
554 stmt1 `mustFollow` stmt2 ]
556 components :: [SCC Vrtx]
557 components = stronglyConnCompFromEdgedVertices edges
559 -- do_components deal with one strongly-connected component
560 -- Not cyclic, or singleton? Just do it
561 do_component :: SCC Vrtx -> CmmAGraph
562 do_component (AcyclicSCC (_,stmt)) = mk_graph stmt
563 do_component (CyclicSCC []) = panic "do_component"
564 do_component (CyclicSCC [(_,stmt)]) = mk_graph stmt
566 -- Cyclic? Then go via temporaries. Pick one to
567 -- break the loop and try again with the rest.
568 do_component (CyclicSCC ((_,first_stmt) : rest))
570 let (to_tmp, from_tmp) = split u first_stmt
573 <*> mk_graph from_tmp
575 split :: Unique -> Stmt -> (Stmt, Stmt)
576 split uniq (reg, rhs)
577 = ((tmp, rhs), (reg, CmmReg (CmmLocal tmp)))
579 rep = cmmExprType rhs
580 tmp = LocalReg uniq rep
582 mk_graph :: Stmt -> CmmAGraph
583 mk_graph (reg, rhs) = mkAssign (CmmLocal reg) rhs
585 mustFollow :: Stmt -> Stmt -> Bool
586 (reg, _) `mustFollow` (_, rhs) = reg `regUsedIn` rhs
588 regUsedIn :: LocalReg -> CmmExpr -> Bool
589 reg `regUsedIn` CmmLoad e _ = reg `regUsedIn` e
590 reg `regUsedIn` CmmReg (CmmLocal reg') = reg == reg'
591 reg `regUsedIn` CmmRegOff (CmmLocal reg') _ = reg == reg'
592 reg `regUsedIn` CmmMachOp _ es = any (reg `regUsedIn`) es
593 _reg `regUsedIn` _other = False -- The CmmGlobal cases
596 -------------------------------------------------------------------------
598 -------------------------------------------------------------------------
601 emitSwitch :: CmmExpr -- Tag to switch on
602 -> [(ConTagZ, CmmAGraph)] -- Tagged branches
603 -> Maybe CmmAGraph -- Default branch (if any)
604 -> ConTagZ -> ConTagZ -- Min and Max possible values; behaviour
605 -- outside this range is undefined
607 emitSwitch tag_expr branches mb_deflt lo_tag hi_tag
608 = do { dflags <- getDynFlags
609 ; emit (mkCmmSwitch (via_C dflags) tag_expr branches mb_deflt lo_tag hi_tag) }
611 via_C dflags | HscC <- hscTarget dflags = True
615 mkCmmSwitch :: Bool -- True <=> never generate a conditional tree
616 -> CmmExpr -- Tag to switch on
617 -> [(ConTagZ, CmmAGraph)] -- Tagged branches
618 -> Maybe CmmAGraph -- Default branch (if any)
619 -> ConTagZ -> ConTagZ -- Min and Max possible values; behaviour
620 -- outside this range is undefined
623 -- First, two rather common cases in which there is no work to do
624 mkCmmSwitch _ _ [] (Just code) _ _ = code
625 mkCmmSwitch _ _ [(_,code)] Nothing _ _ = code
628 mkCmmSwitch via_C tag_expr branches mb_deflt lo_tag hi_tag
629 = withFreshLabel "switch join" $ \ join_lbl ->
630 label_default join_lbl mb_deflt $ \ mb_deflt ->
631 label_branches join_lbl branches $ \ branches ->
632 assignTemp' tag_expr $ \tag_expr' ->
634 mk_switch tag_expr' (sortLe le branches) mb_deflt
636 -- Sort the branches before calling mk_switch
640 (t1,_) `le` (t2,_) = t1 <= t2
642 mk_switch :: CmmExpr -> [(ConTagZ, BlockId)]
644 -> ConTagZ -> ConTagZ -> Bool
647 -- SINGLETON TAG RANGE: no case analysis to do
648 mk_switch _tag_expr [(tag, lbl)] _ lo_tag hi_tag _via_C
650 = ASSERT( tag == lo_tag )
653 -- SINGLETON BRANCH, NO DEFAULT: no case analysis to do
654 mk_switch _tag_expr [(_tag,lbl)] Nothing _ _ _
656 -- The simplifier might have eliminated a case
657 -- so we may have e.g. case xs of
659 -- In that situation we can be sure the (:) case
660 -- can't happen, so no need to test
662 -- SINGLETON BRANCH: one equality check to do
663 mk_switch tag_expr [(tag,lbl)] (Just deflt) _ _ _
664 = mkCbranch cond deflt lbl
666 cond = cmmNeWord tag_expr (CmmLit (mkIntCLit tag))
667 -- We have lo_tag < hi_tag, but there's only one branch,
668 -- so there must be a default
670 -- ToDo: we might want to check for the two branch case, where one of
671 -- the branches is the tag 0, because comparing '== 0' is likely to be
672 -- more efficient than other kinds of comparison.
674 -- DENSE TAG RANGE: use a switch statment.
676 -- We also use a switch uncoditionally when compiling via C, because
677 -- this will get emitted as a C switch statement and the C compiler
678 -- should do a good job of optimising it. Also, older GCC versions
679 -- (2.95 in particular) have problems compiling the complicated
680 -- if-trees generated by this code, so compiling to a switch every
681 -- time works around that problem.
683 mk_switch tag_expr branches mb_deflt lo_tag hi_tag via_C
684 | use_switch -- Use a switch
686 find_branch :: ConTagZ -> Maybe BlockId
687 find_branch i = case (assocMaybe branches i) of
691 -- NB. we have eliminated impossible branches at
692 -- either end of the range (see below), so the first
693 -- tag of a real branch is real_lo_tag (not lo_tag).
694 arms :: [Maybe BlockId]
695 arms = [ find_branch i | i <- [real_lo_tag..real_hi_tag]]
697 mkSwitch (cmmOffset tag_expr (- real_lo_tag)) arms
699 -- if we can knock off a bunch of default cases with one if, then do so
700 | Just deflt <- mb_deflt, (lowest_branch - lo_tag) >= n_branches
702 (cmmULtWord tag_expr (CmmLit (mkIntCLit lowest_branch)))
704 (mk_switch tag_expr branches mb_deflt
705 lowest_branch hi_tag via_C)
707 | Just deflt <- mb_deflt, (hi_tag - highest_branch) >= n_branches
709 (cmmUGtWord tag_expr (CmmLit (mkIntCLit highest_branch)))
711 (mk_switch tag_expr branches mb_deflt
712 lo_tag highest_branch via_C)
714 | otherwise -- Use an if-tree
716 (cmmUGeWord tag_expr (CmmLit (mkIntCLit mid_tag)))
717 (mk_switch tag_expr hi_branches mb_deflt
718 mid_tag hi_tag via_C)
719 (mk_switch tag_expr lo_branches mb_deflt
720 lo_tag (mid_tag-1) via_C)
721 -- we test (e >= mid_tag) rather than (e < mid_tag), because
722 -- the former works better when e is a comparison, and there
723 -- are two tags 0 & 1 (mid_tag == 1). In this case, the code
724 -- generator can reduce the condition to e itself without
725 -- having to reverse the sense of the comparison: comparisons
726 -- can't always be easily reversed (eg. floating
729 use_switch = {- pprTrace "mk_switch" (
730 ppr tag_expr <+> text "n_tags:" <+> int n_tags <+>
731 text "branches:" <+> ppr (map fst branches) <+>
732 text "n_branches:" <+> int n_branches <+>
733 text "lo_tag:" <+> int lo_tag <+>
734 text "hi_tag:" <+> int hi_tag <+>
735 text "real_lo_tag:" <+> int real_lo_tag <+>
736 text "real_hi_tag:" <+> int real_hi_tag) $ -}
737 ASSERT( n_branches > 1 && n_tags > 1 )
738 n_tags > 2 && (via_C || (dense && big_enough))
739 -- up to 4 branches we use a decision tree, otherwise
740 -- a switch (== jump table in the NCG). This seems to be
741 -- optimal, and corresponds with what gcc does.
742 big_enough = n_branches > 4
743 dense = n_branches > (n_tags `div` 2)
744 n_branches = length branches
746 -- ignore default slots at each end of the range if there's
747 -- no default branch defined.
748 lowest_branch = fst (head branches)
749 highest_branch = fst (last branches)
752 | isNothing mb_deflt = lowest_branch
756 | isNothing mb_deflt = highest_branch
759 n_tags = real_hi_tag - real_lo_tag + 1
761 -- INVARIANT: Provided hi_tag > lo_tag (which is true)
762 -- lo_tag <= mid_tag < hi_tag
763 -- lo_branches have tags < mid_tag
764 -- hi_branches have tags >= mid_tag
766 (mid_tag,_) = branches !! (n_branches `div` 2)
767 -- 2 branches => n_branches `div` 2 = 1
768 -- => branches !! 1 give the *second* tag
769 -- There are always at least 2 branches here
771 (lo_branches, hi_branches) = span is_lo branches
772 is_lo (t,_) = t < mid_tag
775 mkCmmLitSwitch :: CmmExpr -- Tag to switch on
776 -> [(Literal, CmmAGraph)] -- Tagged branches
777 -> CmmAGraph -- Default branch (always)
778 -> CmmAGraph -- Emit the code
779 -- Used for general literals, whose size might not be a word,
780 -- where there is always a default case, and where we don't know
781 -- the range of values for certain. For simplicity we always generate a tree.
783 -- ToDo: for integers we could do better here, perhaps by generalising
784 -- mk_switch and using that. --SDM 15/09/2004
785 mkCmmLitSwitch _scrut [] deflt = deflt
786 mkCmmLitSwitch scrut branches deflt
787 = assignTemp' scrut $ \ scrut' ->
788 withFreshLabel "switch join" $ \ join_lbl ->
789 label_code join_lbl deflt $ \ deflt ->
790 label_branches join_lbl branches $ \ branches ->
791 mk_lit_switch scrut' deflt (sortLe le branches)
794 le (t1,_) (t2,_) = t1 <= t2
796 mk_lit_switch :: CmmExpr -> BlockId
797 -> [(Literal,BlockId)]
799 mk_lit_switch scrut deflt [(lit,blk)]
800 = mkCbranch (CmmMachOp ne [scrut, CmmLit cmm_lit]) deflt blk
802 cmm_lit = mkSimpleLit lit
803 cmm_ty = cmmLitType cmm_lit
804 rep = typeWidth cmm_ty
805 ne = if isFloatType cmm_ty then MO_F_Ne rep else MO_Ne rep
807 mk_lit_switch scrut deflt_blk_id branches
808 = mkCmmIfThenElse cond
809 (mk_lit_switch scrut deflt_blk_id lo_branches)
810 (mk_lit_switch scrut deflt_blk_id hi_branches)
812 n_branches = length branches
813 (mid_lit,_) = branches !! (n_branches `div` 2)
814 -- See notes above re mid_tag
816 (lo_branches, hi_branches) = span is_lo branches
817 is_lo (t,_) = t < mid_lit
819 cond = CmmMachOp (mkLtOp mid_lit)
820 [scrut, CmmLit (mkSimpleLit mid_lit)]
824 label_default :: BlockId -> Maybe CmmAGraph
825 -> (Maybe BlockId -> CmmAGraph)
827 label_default _ Nothing thing_inside
828 = thing_inside Nothing
829 label_default join_lbl (Just code) thing_inside
830 = label_code join_lbl code $ \ lbl ->
831 thing_inside (Just lbl)
834 label_branches :: BlockId -> [(a,CmmAGraph)]
835 -> ([(a,BlockId)] -> CmmAGraph)
837 label_branches _join_lbl [] thing_inside
839 label_branches join_lbl ((tag,code):branches) thing_inside
840 = label_code join_lbl code $ \ lbl ->
841 label_branches join_lbl branches $ \ branches' ->
842 thing_inside ((tag,lbl):branches')
845 label_code :: BlockId -> CmmAGraph -> (BlockId -> CmmAGraph) -> CmmAGraph
846 -- (label_code J code fun)
848 -- [L: code; goto J] fun L
849 label_code join_lbl code thing_inside
850 = withFreshLabel "switch" $ \lbl ->
851 outOfLine (mkLabel lbl <*> code <*> mkBranch join_lbl)
856 assignTemp' :: CmmExpr -> (CmmExpr -> CmmAGraph) -> CmmAGraph
857 assignTemp' e thing_inside
858 | isTrivialCmmExpr e = thing_inside e
859 | otherwise = withTemp (cmmExprType e) $ \ lreg ->
860 let reg = CmmLocal lreg in
861 mkAssign reg e <*> thing_inside (CmmReg reg)
863 withTemp :: CmmType -> (LocalReg -> CmmAGraph) -> CmmAGraph
864 withTemp rep thing_inside
865 = withUnique $ \uniq -> thing_inside (LocalReg uniq rep)
868 -------------------------------------------------------------------------
870 -- Static Reference Tables
872 -------------------------------------------------------------------------
874 -- There is just one SRT for each top level binding; all the nested
875 -- bindings use sub-sections of this SRT. The label is passed down to
876 -- the nested bindings via the monad.
878 getSRTInfo :: SRT -> FCode C_SRT
879 getSRTInfo (SRTEntries {}) = panic "getSRTInfo"
881 getSRTInfo (SRT off len bmp)
882 | len > hALF_WORD_SIZE_IN_BITS || bmp == [fromIntegral srt_escape]
883 = do { id <- newUnique
884 -- ; top_srt <- getSRTLabel
885 ; let srt_desc_lbl = mkLargeSRTLabel id
886 -- JD: We're not constructing and emitting SRTs in the back end,
887 -- which renders this code wrong (it now names a now-non-existent label).
888 -- ; emitRODataLits srt_desc_lbl
889 -- ( cmmLabelOffW top_srt off
890 -- : mkWordCLit (fromIntegral len)
891 -- : map mkWordCLit bmp)
892 ; return (C_SRT srt_desc_lbl 0 srt_escape) }
895 = do { top_srt <- getSRTLabel
896 ; return (C_SRT top_srt off (fromIntegral (head bmp))) }
897 -- The fromIntegral converts to StgHalfWord
900 = -- TODO: Should we panic in this case?
901 -- Someone obviously thinks there should be an SRT
905 srt_escape :: StgHalfWord