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"
52 import Cmm hiding (regUsedIn)
56 import PprCmm ( {- instances -} )
64 import StgSyn ( SRT(..) )
81 -------------------------------------------------------------------------
85 -------------------------------------------------------------------------
87 cgLit :: Literal -> FCode CmmLit
88 cgLit (MachStr s) = mkByteStringCLit (bytesFS s)
89 -- not unpackFS; we want the UTF-8 byte stream.
90 cgLit other_lit = return (mkSimpleLit other_lit)
92 mkSimpleLit :: Literal -> CmmLit
93 mkSimpleLit (MachChar c) = CmmInt (fromIntegral (ord c)) wordWidth
94 mkSimpleLit MachNullAddr = zeroCLit
95 mkSimpleLit (MachInt i) = CmmInt i wordWidth
96 mkSimpleLit (MachInt64 i) = CmmInt i W64
97 mkSimpleLit (MachWord i) = CmmInt i wordWidth
98 mkSimpleLit (MachWord64 i) = CmmInt i W64
99 mkSimpleLit (MachFloat r) = CmmFloat r W32
100 mkSimpleLit (MachDouble r) = CmmFloat r W64
101 mkSimpleLit (MachLabel fs ms fod)
102 = CmmLabel (mkForeignLabel fs ms labelSrc fod)
104 -- TODO: Literal labels might not actually be in the current package...
105 labelSrc = ForeignLabelInThisPackage
106 mkSimpleLit other = pprPanic "mkSimpleLit" (ppr other)
108 mkLtOp :: Literal -> MachOp
109 -- On signed literals we must do a signed comparison
110 mkLtOp (MachInt _) = MO_S_Lt wordWidth
111 mkLtOp (MachFloat _) = MO_F_Lt W32
112 mkLtOp (MachDouble _) = MO_F_Lt W64
113 mkLtOp lit = MO_U_Lt (typeWidth (cmmLitType (mkSimpleLit lit)))
114 -- ToDo: seems terribly indirect!
117 ---------------------------------------------------
119 -- Cmm data type functions
121 ---------------------------------------------------
123 -- The "B" variants take byte offsets
124 cmmRegOffB :: CmmReg -> ByteOff -> CmmExpr
125 cmmRegOffB = cmmRegOff
127 cmmOffsetB :: CmmExpr -> ByteOff -> CmmExpr
128 cmmOffsetB = cmmOffset
130 cmmOffsetExprB :: CmmExpr -> CmmExpr -> CmmExpr
131 cmmOffsetExprB = cmmOffsetExpr
133 cmmLabelOffB :: CLabel -> ByteOff -> CmmLit
134 cmmLabelOffB = cmmLabelOff
136 cmmOffsetLitB :: CmmLit -> ByteOff -> CmmLit
137 cmmOffsetLitB = cmmOffsetLit
139 -----------------------
140 -- The "W" variants take word offsets
141 cmmOffsetExprW :: CmmExpr -> CmmExpr -> CmmExpr
142 -- The second arg is a *word* offset; need to change it to bytes
143 cmmOffsetExprW e (CmmLit (CmmInt n _)) = cmmOffsetW e (fromInteger n)
144 cmmOffsetExprW e wd_off = cmmIndexExpr wordWidth e wd_off
146 cmmOffsetW :: CmmExpr -> WordOff -> CmmExpr
147 cmmOffsetW e n = cmmOffsetB e (wORD_SIZE * n)
149 cmmRegOffW :: CmmReg -> WordOff -> CmmExpr
150 cmmRegOffW reg wd_off = cmmRegOffB reg (wd_off * wORD_SIZE)
152 cmmOffsetLitW :: CmmLit -> WordOff -> CmmLit
153 cmmOffsetLitW lit wd_off = cmmOffsetLitB lit (wORD_SIZE * wd_off)
155 cmmLabelOffW :: CLabel -> WordOff -> CmmLit
156 cmmLabelOffW lbl wd_off = cmmLabelOffB lbl (wORD_SIZE * wd_off)
158 cmmLoadIndexW :: CmmExpr -> Int -> CmmType -> CmmExpr
159 cmmLoadIndexW base off ty = CmmLoad (cmmOffsetW base off) ty
161 -----------------------
162 cmmULtWord, cmmUGeWord, cmmUGtWord, cmmSubWord,
163 cmmNeWord, cmmEqWord, cmmOrWord, cmmAndWord
164 :: CmmExpr -> CmmExpr -> CmmExpr
165 cmmOrWord e1 e2 = CmmMachOp mo_wordOr [e1, e2]
166 cmmAndWord e1 e2 = CmmMachOp mo_wordAnd [e1, e2]
167 cmmNeWord e1 e2 = CmmMachOp mo_wordNe [e1, e2]
168 cmmEqWord e1 e2 = CmmMachOp mo_wordEq [e1, e2]
169 cmmULtWord e1 e2 = CmmMachOp mo_wordULt [e1, e2]
170 cmmUGeWord e1 e2 = CmmMachOp mo_wordUGe [e1, e2]
171 cmmUGtWord e1 e2 = CmmMachOp mo_wordUGt [e1, e2]
172 --cmmShlWord e1 e2 = CmmMachOp mo_wordShl [e1, e2]
173 --cmmUShrWord e1 e2 = CmmMachOp mo_wordUShr [e1, e2]
174 cmmSubWord e1 e2 = CmmMachOp mo_wordSub [e1, e2]
176 cmmNegate :: CmmExpr -> CmmExpr
177 cmmNegate (CmmLit (CmmInt n rep)) = CmmLit (CmmInt (-n) rep)
178 cmmNegate e = CmmMachOp (MO_S_Neg (cmmExprWidth e)) [e]
180 blankWord :: CmmStatic
181 blankWord = CmmUninitialised wORD_SIZE
185 --cmmTagBits = CmmLit (mkIntCLit tAG_BITS)
186 cmmTagMask, cmmPointerMask :: CmmExpr
187 cmmTagMask = CmmLit (mkIntCLit tAG_MASK)
188 cmmPointerMask = CmmLit (mkIntCLit (complement tAG_MASK))
190 -- Used to untag a possibly tagged pointer
191 -- A static label need not be untagged
192 cmmUntag, cmmGetTag :: CmmExpr -> CmmExpr
193 cmmUntag e@(CmmLit (CmmLabel _)) = e
195 cmmUntag e = (e `cmmAndWord` cmmPointerMask)
197 cmmGetTag e = (e `cmmAndWord` cmmTagMask)
199 -- Test if a closure pointer is untagged
200 cmmIsTagged :: CmmExpr -> CmmExpr
201 cmmIsTagged e = (e `cmmAndWord` cmmTagMask)
202 `cmmNeWord` CmmLit zeroCLit
204 cmmConstrTag, cmmConstrTag1 :: CmmExpr -> CmmExpr
205 cmmConstrTag e = (e `cmmAndWord` cmmTagMask) `cmmSubWord` (CmmLit (mkIntCLit 1))
206 -- Get constructor tag, but one based.
207 cmmConstrTag1 e = e `cmmAndWord` cmmTagMask
209 -----------------------
212 mkWordCLit :: StgWord -> CmmLit
213 mkWordCLit wd = CmmInt (fromIntegral wd) wordWidth
215 packHalfWordsCLit :: (Integral a, Integral b) => a -> b -> CmmLit
216 -- Make a single word literal in which the lower_half_word is
217 -- at the lower address, and the upper_half_word is at the
219 -- ToDo: consider using half-word lits instead
220 -- but be careful: that's vulnerable when reversed
221 packHalfWordsCLit lower_half_word upper_half_word
222 #ifdef WORDS_BIGENDIAN
223 = mkWordCLit ((fromIntegral lower_half_word `shiftL` hALF_WORD_SIZE_IN_BITS)
224 .|. fromIntegral upper_half_word)
226 = mkWordCLit ((fromIntegral lower_half_word)
227 .|. (fromIntegral upper_half_word `shiftL` hALF_WORD_SIZE_IN_BITS))
230 --------------------------------------------------------------------------
232 -- Incrementing a memory location
234 --------------------------------------------------------------------------
236 addToMemLbl :: CmmType -> CLabel -> Int -> CmmAGraph
237 addToMemLbl rep lbl n = addToMem rep (CmmLit (CmmLabel lbl)) n
239 addToMem :: CmmType -- rep of the counter
240 -> CmmExpr -- Address
241 -> Int -- What to add (a word)
243 addToMem rep ptr n = addToMemE rep ptr (CmmLit (CmmInt (toInteger n) (typeWidth rep)))
245 addToMemE :: CmmType -- rep of the counter
246 -> CmmExpr -- Address
247 -> CmmExpr -- What to add (a word-typed expression)
250 = mkStore ptr (CmmMachOp (MO_Add (typeWidth rep)) [CmmLoad ptr rep, n])
253 -------------------------------------------------------------------------
255 -- Loading a field from an object,
256 -- where the object pointer is itself tagged
258 -------------------------------------------------------------------------
260 mkTaggedObjectLoad :: LocalReg -> LocalReg -> WordOff -> DynTag -> CmmAGraph
261 -- (loadTaggedObjectField reg base off tag) generates assignment
262 -- reg = bitsK[ base + off - tag ]
263 -- where K is fixed by 'reg'
264 mkTaggedObjectLoad reg base offset tag
265 = mkAssign (CmmLocal reg)
266 (CmmLoad (cmmOffsetB (CmmReg (CmmLocal base))
267 (wORD_SIZE*offset - tag))
270 -------------------------------------------------------------------------
272 -- Converting a closure tag to a closure for enumeration types
273 -- (this is the implementation of tagToEnum#).
275 -------------------------------------------------------------------------
277 tagToClosure :: TyCon -> CmmExpr -> CmmExpr
278 tagToClosure tycon tag
279 = CmmLoad (cmmOffsetExprW closure_tbl tag) bWord
280 where closure_tbl = CmmLit (CmmLabel lbl)
281 lbl = mkClosureTableLabel (tyConName tycon) NoCafRefs
283 -------------------------------------------------------------------------
285 -- Conditionals and rts calls
287 -------------------------------------------------------------------------
289 emitRtsCall :: PackageId -> FastString -> [(CmmExpr,ForeignHint)] -> Bool -> FCode ()
290 emitRtsCall pkg fun args safe = emitRtsCall' [] pkg fun args Nothing safe
291 -- The 'Nothing' says "save all global registers"
293 emitRtsCallWithVols :: PackageId -> FastString -> [(CmmExpr,ForeignHint)] -> [GlobalReg] -> Bool -> FCode ()
294 emitRtsCallWithVols pkg fun args vols safe
295 = emitRtsCall' [] pkg fun args (Just vols) safe
297 emitRtsCallWithResult :: LocalReg -> ForeignHint -> PackageId -> FastString
298 -> [(CmmExpr,ForeignHint)] -> Bool -> FCode ()
299 emitRtsCallWithResult res hint pkg fun args safe
300 = emitRtsCall' [(res,hint)] pkg fun args Nothing safe
302 -- Make a call to an RTS C procedure
304 :: [(LocalReg,ForeignHint)]
307 -> [(CmmExpr,ForeignHint)]
309 -> Bool -- True <=> CmmSafe call
311 emitRtsCall' res pkg fun args _vols safe
312 = --error "emitRtsCall'"
313 do { updfr_off <- getUpdFrameOff
315 ; emit $ call updfr_off
320 mkCmmCall fun_expr res' args' updfr_off
322 mkUnsafeCall (ForeignTarget fun_expr
323 (ForeignConvention CCallConv arg_hints res_hints)) res' args'
324 (args', arg_hints) = unzip args
325 (res', res_hints) = unzip res
326 (caller_save, caller_load) = callerSaveVolatileRegs
327 fun_expr = mkLblExpr (mkCmmCodeLabel pkg fun)
330 -----------------------------------------------------------------------------
332 -- Caller-Save Registers
334 -----------------------------------------------------------------------------
336 -- Here we generate the sequence of saves/restores required around a
337 -- foreign call instruction.
339 -- TODO: reconcile with includes/Regs.h
340 -- * Regs.h claims that BaseReg should be saved last and loaded first
341 -- * This might not have been tickled before since BaseReg is callee save
342 -- * Regs.h saves SparkHd, ParkT1, SparkBase and SparkLim
343 callerSaveVolatileRegs :: (CmmAGraph, CmmAGraph)
344 callerSaveVolatileRegs = (caller_save, caller_load)
346 caller_save = catAGraphs (map callerSaveGlobalReg regs_to_save)
347 caller_load = catAGraphs (map callerRestoreGlobalReg regs_to_save)
349 system_regs = [ Sp,SpLim,Hp,HpLim,CurrentTSO,CurrentNursery
350 {- ,SparkHd,SparkTl,SparkBase,SparkLim -}
353 regs_to_save = filter callerSaves system_regs
355 callerSaveGlobalReg reg
356 = mkStore (get_GlobalReg_addr reg) (CmmReg (CmmGlobal reg))
358 callerRestoreGlobalReg reg
359 = mkAssign (CmmGlobal reg)
360 (CmmLoad (get_GlobalReg_addr reg) (globalRegType reg))
362 -- -----------------------------------------------------------------------------
365 -- We map STG registers onto appropriate CmmExprs. Either they map
366 -- to real machine registers or stored as offsets from BaseReg. Given
367 -- a GlobalReg, get_GlobalReg_addr always produces the
368 -- register table address for it.
369 -- (See also get_GlobalReg_reg_or_addr in MachRegs)
371 get_GlobalReg_addr :: GlobalReg -> CmmExpr
372 get_GlobalReg_addr BaseReg = regTableOffset 0
373 get_GlobalReg_addr mid = get_Regtable_addr_from_offset
374 (globalRegType mid) (baseRegOffset mid)
376 -- Calculate a literal representing an offset into the register table.
377 -- Used when we don't have an actual BaseReg to offset from.
378 regTableOffset :: Int -> CmmExpr
380 CmmLit (CmmLabelOff mkMainCapabilityLabel (oFFSET_Capability_r + n))
382 get_Regtable_addr_from_offset :: CmmType -> Int -> CmmExpr
383 get_Regtable_addr_from_offset _rep offset =
385 CmmRegOff (CmmGlobal BaseReg) offset
387 regTableOffset offset
391 -- | Returns 'True' if this global register is stored in a caller-saves
394 callerSaves :: GlobalReg -> Bool
396 #ifdef CALLER_SAVES_Base
397 callerSaves BaseReg = True
399 #ifdef CALLER_SAVES_Sp
400 callerSaves Sp = True
402 #ifdef CALLER_SAVES_SpLim
403 callerSaves SpLim = True
405 #ifdef CALLER_SAVES_Hp
406 callerSaves Hp = True
408 #ifdef CALLER_SAVES_HpLim
409 callerSaves HpLim = True
411 #ifdef CALLER_SAVES_CurrentTSO
412 callerSaves CurrentTSO = True
414 #ifdef CALLER_SAVES_CurrentNursery
415 callerSaves CurrentNursery = True
417 callerSaves _ = False
420 -- -----------------------------------------------------------------------------
421 -- Information about global registers
423 baseRegOffset :: GlobalReg -> Int
425 baseRegOffset Sp = oFFSET_StgRegTable_rSp
426 baseRegOffset SpLim = oFFSET_StgRegTable_rSpLim
427 baseRegOffset (LongReg 1) = oFFSET_StgRegTable_rL1
428 baseRegOffset Hp = oFFSET_StgRegTable_rHp
429 baseRegOffset HpLim = oFFSET_StgRegTable_rHpLim
430 baseRegOffset CurrentTSO = oFFSET_StgRegTable_rCurrentTSO
431 baseRegOffset CurrentNursery = oFFSET_StgRegTable_rCurrentNursery
432 baseRegOffset HpAlloc = oFFSET_StgRegTable_rHpAlloc
433 baseRegOffset GCEnter1 = oFFSET_stgGCEnter1
434 baseRegOffset GCFun = oFFSET_stgGCFun
435 baseRegOffset reg = pprPanic "baseRegOffset:" (ppr reg)
437 -------------------------------------------------------------------------
439 -- Strings generate a top-level data block
441 -------------------------------------------------------------------------
443 emitDataLits :: CLabel -> [CmmLit] -> FCode ()
444 -- Emit a data-segment data block
445 emitDataLits lbl lits
446 = emitData Data (CmmDataLabel lbl : map CmmStaticLit lits)
448 mkDataLits :: CLabel -> [CmmLit] -> GenCmmTop CmmStatic info stmt
449 -- Emit a data-segment data block
451 = CmmData Data (CmmDataLabel lbl : map CmmStaticLit lits)
453 emitRODataLits :: CLabel -> [CmmLit] -> FCode ()
454 -- Emit a read-only data block
455 emitRODataLits lbl lits
456 = emitData section (CmmDataLabel lbl : map CmmStaticLit lits)
457 where section | any needsRelocation lits = RelocatableReadOnlyData
458 | otherwise = ReadOnlyData
459 needsRelocation (CmmLabel _) = True
460 needsRelocation (CmmLabelOff _ _) = True
461 needsRelocation _ = False
463 mkRODataLits :: CLabel -> [CmmLit] -> GenCmmTop CmmStatic info stmt
464 mkRODataLits lbl lits
465 = CmmData section (CmmDataLabel lbl : map CmmStaticLit lits)
466 where section | any needsRelocation lits = RelocatableReadOnlyData
467 | otherwise = ReadOnlyData
468 needsRelocation (CmmLabel _) = True
469 needsRelocation (CmmLabelOff _ _) = True
470 needsRelocation _ = False
472 mkStringCLit :: String -> FCode CmmLit
473 -- Make a global definition for the string,
474 -- and return its label
475 mkStringCLit str = mkByteStringCLit (map (fromIntegral . ord) str)
477 mkByteStringCLit :: [Word8] -> FCode CmmLit
478 mkByteStringCLit bytes
479 = do { uniq <- newUnique
480 ; let lbl = mkStringLitLabel uniq
481 ; emitData ReadOnlyData [CmmDataLabel lbl, CmmString bytes]
482 ; return (CmmLabel lbl) }
484 -------------------------------------------------------------------------
486 -- Assigning expressions to temporaries
488 -------------------------------------------------------------------------
490 assignTemp :: CmmExpr -> FCode LocalReg
491 -- Make sure the argument is in a local register
492 assignTemp (CmmReg (CmmLocal reg)) = return reg
493 assignTemp e = do { uniq <- newUnique
494 ; let reg = LocalReg uniq (cmmExprType e)
495 ; emit (mkAssign (CmmLocal reg) e)
498 newTemp :: CmmType -> FCode LocalReg
499 newTemp rep = do { uniq <- newUnique
500 ; return (LocalReg uniq rep) }
502 newUnboxedTupleRegs :: Type -> FCode ([LocalReg], [ForeignHint])
503 -- Choose suitable local regs to use for the components
504 -- of an unboxed tuple that we are about to return to
505 -- the Sequel. If the Sequel is a join point, using the
506 -- regs it wants will save later assignments.
507 newUnboxedTupleRegs res_ty
508 = ASSERT( isUnboxedTupleType res_ty )
509 do { sequel <- getSequel
510 ; regs <- choose_regs sequel
511 ; ASSERT( regs `equalLength` reps )
512 return (regs, map primRepForeignHint reps) }
514 ty_args = tyConAppArgs (repType res_ty)
517 , let rep = typePrimRep ty
518 , not (isVoidRep rep) ]
519 choose_regs (AssignTo regs _) = return regs
520 choose_regs _other = mapM (newTemp . primRepCmmType) reps
524 -------------------------------------------------------------------------
526 -------------------------------------------------------------------------
528 mkMultiAssign :: [LocalReg] -> [CmmExpr] -> CmmAGraph
529 -- Emit code to perform the assignments in the
530 -- input simultaneously, using temporary variables when necessary.
533 type Vrtx = (Key, Stmt) -- Give each vertex a unique number,
534 -- for fast comparison
535 type Stmt = (LocalReg, CmmExpr) -- r := e
537 -- We use the strongly-connected component algorithm, in which
538 -- * the vertices are the statements
539 -- * an edge goes from s1 to s2 iff
540 -- s1 assigns to something s2 uses
541 -- that is, if s1 should *follow* s2 in the final order
543 mkMultiAssign [] [] = mkNop
544 mkMultiAssign [reg] [rhs] = mkAssign (CmmLocal reg) rhs
545 mkMultiAssign regs rhss = ASSERT( equalLength regs rhss )
546 unscramble ([1..] `zip` (regs `zip` rhss))
548 unscramble :: [Vrtx] -> CmmAGraph
550 = catAGraphs (map do_component components)
552 edges :: [ (Vrtx, Key, [Key]) ]
553 edges = [ (vertex, key1, edges_from stmt1)
554 | vertex@(key1, stmt1) <- vertices ]
556 edges_from :: Stmt -> [Key]
557 edges_from stmt1 = [ key2 | (key2, stmt2) <- vertices,
558 stmt1 `mustFollow` stmt2 ]
560 components :: [SCC Vrtx]
561 components = stronglyConnCompFromEdgedVertices edges
563 -- do_components deal with one strongly-connected component
564 -- Not cyclic, or singleton? Just do it
565 do_component :: SCC Vrtx -> CmmAGraph
566 do_component (AcyclicSCC (_,stmt)) = mk_graph stmt
567 do_component (CyclicSCC []) = panic "do_component"
568 do_component (CyclicSCC [(_,stmt)]) = mk_graph stmt
570 -- Cyclic? Then go via temporaries. Pick one to
571 -- break the loop and try again with the rest.
572 do_component (CyclicSCC ((_,first_stmt) : rest))
574 let (to_tmp, from_tmp) = split u first_stmt
577 <*> mk_graph from_tmp
579 split :: Unique -> Stmt -> (Stmt, Stmt)
580 split uniq (reg, rhs)
581 = ((tmp, rhs), (reg, CmmReg (CmmLocal tmp)))
583 rep = cmmExprType rhs
584 tmp = LocalReg uniq rep
586 mk_graph :: Stmt -> CmmAGraph
587 mk_graph (reg, rhs) = mkAssign (CmmLocal reg) rhs
589 mustFollow :: Stmt -> Stmt -> Bool
590 (reg, _) `mustFollow` (_, rhs) = reg `regUsedIn` rhs
592 regUsedIn :: LocalReg -> CmmExpr -> Bool
593 reg `regUsedIn` CmmLoad e _ = reg `regUsedIn` e
594 reg `regUsedIn` CmmReg (CmmLocal reg') = reg == reg'
595 reg `regUsedIn` CmmRegOff (CmmLocal reg') _ = reg == reg'
596 reg `regUsedIn` CmmMachOp _ es = any (reg `regUsedIn`) es
597 _reg `regUsedIn` _other = False -- The CmmGlobal cases
599 -------------------------------------------------------------------------
601 -------------------------------------------------------------------------
604 emitSwitch :: CmmExpr -- Tag to switch on
605 -> [(ConTagZ, CmmAGraph)] -- Tagged branches
606 -> Maybe CmmAGraph -- Default branch (if any)
607 -> ConTagZ -> ConTagZ -- Min and Max possible values; behaviour
608 -- outside this range is undefined
610 emitSwitch tag_expr branches mb_deflt lo_tag hi_tag
611 = do { dflags <- getDynFlags
612 ; emit (mkCmmSwitch (via_C dflags) tag_expr branches mb_deflt lo_tag hi_tag) }
614 via_C dflags | HscC <- hscTarget dflags = True
618 mkCmmSwitch :: Bool -- True <=> never generate a conditional tree
619 -> CmmExpr -- Tag to switch on
620 -> [(ConTagZ, CmmAGraph)] -- Tagged branches
621 -> Maybe CmmAGraph -- Default branch (if any)
622 -> ConTagZ -> ConTagZ -- Min and Max possible values; behaviour
623 -- outside this range is undefined
626 -- First, two rather common cases in which there is no work to do
627 mkCmmSwitch _ _ [] (Just code) _ _ = code
628 mkCmmSwitch _ _ [(_,code)] Nothing _ _ = code
631 mkCmmSwitch via_C tag_expr branches mb_deflt lo_tag hi_tag
632 = withFreshLabel "switch join" $ \ join_lbl ->
633 label_default join_lbl mb_deflt $ \ mb_deflt ->
634 label_branches join_lbl branches $ \ branches ->
635 assignTemp' tag_expr $ \tag_expr' ->
637 mk_switch tag_expr' (sortLe le branches) mb_deflt
639 -- Sort the branches before calling mk_switch
643 (t1,_) `le` (t2,_) = t1 <= t2
645 mk_switch :: CmmExpr -> [(ConTagZ, BlockId)]
647 -> ConTagZ -> ConTagZ -> Bool
650 -- SINGLETON TAG RANGE: no case analysis to do
651 mk_switch _tag_expr [(tag, lbl)] _ lo_tag hi_tag _via_C
653 = ASSERT( tag == lo_tag )
656 -- SINGLETON BRANCH, NO DEFAULT: no case analysis to do
657 mk_switch _tag_expr [(_tag,lbl)] Nothing _ _ _
659 -- The simplifier might have eliminated a case
660 -- so we may have e.g. case xs of
662 -- In that situation we can be sure the (:) case
663 -- can't happen, so no need to test
665 -- SINGLETON BRANCH: one equality check to do
666 mk_switch tag_expr [(tag,lbl)] (Just deflt) _ _ _
667 = mkCbranch cond deflt lbl
669 cond = cmmNeWord tag_expr (CmmLit (mkIntCLit tag))
670 -- We have lo_tag < hi_tag, but there's only one branch,
671 -- so there must be a default
673 -- ToDo: we might want to check for the two branch case, where one of
674 -- the branches is the tag 0, because comparing '== 0' is likely to be
675 -- more efficient than other kinds of comparison.
677 -- DENSE TAG RANGE: use a switch statment.
679 -- We also use a switch uncoditionally when compiling via C, because
680 -- this will get emitted as a C switch statement and the C compiler
681 -- should do a good job of optimising it. Also, older GCC versions
682 -- (2.95 in particular) have problems compiling the complicated
683 -- if-trees generated by this code, so compiling to a switch every
684 -- time works around that problem.
686 mk_switch tag_expr branches mb_deflt lo_tag hi_tag via_C
687 | use_switch -- Use a switch
689 find_branch :: ConTagZ -> Maybe BlockId
690 find_branch i = case (assocMaybe branches i) of
694 -- NB. we have eliminated impossible branches at
695 -- either end of the range (see below), so the first
696 -- tag of a real branch is real_lo_tag (not lo_tag).
697 arms :: [Maybe BlockId]
698 arms = [ find_branch i | i <- [real_lo_tag..real_hi_tag]]
700 mkSwitch (cmmOffset tag_expr (- real_lo_tag)) arms
702 -- if we can knock off a bunch of default cases with one if, then do so
703 | Just deflt <- mb_deflt, (lowest_branch - lo_tag) >= n_branches
705 (cmmULtWord tag_expr (CmmLit (mkIntCLit lowest_branch)))
707 (mk_switch tag_expr branches mb_deflt
708 lowest_branch hi_tag via_C)
710 | Just deflt <- mb_deflt, (hi_tag - highest_branch) >= n_branches
712 (cmmUGtWord tag_expr (CmmLit (mkIntCLit highest_branch)))
714 (mk_switch tag_expr branches mb_deflt
715 lo_tag highest_branch via_C)
717 | otherwise -- Use an if-tree
719 (cmmUGeWord tag_expr (CmmLit (mkIntCLit mid_tag)))
720 (mk_switch tag_expr hi_branches mb_deflt
721 mid_tag hi_tag via_C)
722 (mk_switch tag_expr lo_branches mb_deflt
723 lo_tag (mid_tag-1) via_C)
724 -- we test (e >= mid_tag) rather than (e < mid_tag), because
725 -- the former works better when e is a comparison, and there
726 -- are two tags 0 & 1 (mid_tag == 1). In this case, the code
727 -- generator can reduce the condition to e itself without
728 -- having to reverse the sense of the comparison: comparisons
729 -- can't always be easily reversed (eg. floating
732 use_switch = {- pprTrace "mk_switch" (
733 ppr tag_expr <+> text "n_tags:" <+> int n_tags <+>
734 text "branches:" <+> ppr (map fst branches) <+>
735 text "n_branches:" <+> int n_branches <+>
736 text "lo_tag:" <+> int lo_tag <+>
737 text "hi_tag:" <+> int hi_tag <+>
738 text "real_lo_tag:" <+> int real_lo_tag <+>
739 text "real_hi_tag:" <+> int real_hi_tag) $ -}
740 ASSERT( n_branches > 1 && n_tags > 1 )
741 n_tags > 2 && (via_C || (dense && big_enough))
742 -- up to 4 branches we use a decision tree, otherwise
743 -- a switch (== jump table in the NCG). This seems to be
744 -- optimal, and corresponds with what gcc does.
745 big_enough = n_branches > 4
746 dense = n_branches > (n_tags `div` 2)
747 n_branches = length branches
749 -- ignore default slots at each end of the range if there's
750 -- no default branch defined.
751 lowest_branch = fst (head branches)
752 highest_branch = fst (last branches)
755 | isNothing mb_deflt = lowest_branch
759 | isNothing mb_deflt = highest_branch
762 n_tags = real_hi_tag - real_lo_tag + 1
764 -- INVARIANT: Provided hi_tag > lo_tag (which is true)
765 -- lo_tag <= mid_tag < hi_tag
766 -- lo_branches have tags < mid_tag
767 -- hi_branches have tags >= mid_tag
769 (mid_tag,_) = branches !! (n_branches `div` 2)
770 -- 2 branches => n_branches `div` 2 = 1
771 -- => branches !! 1 give the *second* tag
772 -- There are always at least 2 branches here
774 (lo_branches, hi_branches) = span is_lo branches
775 is_lo (t,_) = t < mid_tag
778 mkCmmLitSwitch :: CmmExpr -- Tag to switch on
779 -> [(Literal, CmmAGraph)] -- Tagged branches
780 -> CmmAGraph -- Default branch (always)
781 -> CmmAGraph -- Emit the code
782 -- Used for general literals, whose size might not be a word,
783 -- where there is always a default case, and where we don't know
784 -- the range of values for certain. For simplicity we always generate a tree.
786 -- ToDo: for integers we could do better here, perhaps by generalising
787 -- mk_switch and using that. --SDM 15/09/2004
788 mkCmmLitSwitch _scrut [] deflt = deflt
789 mkCmmLitSwitch scrut branches deflt
790 = assignTemp' scrut $ \ scrut' ->
791 withFreshLabel "switch join" $ \ join_lbl ->
792 label_code join_lbl deflt $ \ deflt ->
793 label_branches join_lbl branches $ \ branches ->
794 mk_lit_switch scrut' deflt (sortLe le branches)
797 le (t1,_) (t2,_) = t1 <= t2
799 mk_lit_switch :: CmmExpr -> BlockId
800 -> [(Literal,BlockId)]
802 mk_lit_switch scrut deflt [(lit,blk)]
803 = mkCbranch (CmmMachOp ne [scrut, CmmLit cmm_lit]) deflt blk
805 cmm_lit = mkSimpleLit lit
806 cmm_ty = cmmLitType cmm_lit
807 rep = typeWidth cmm_ty
808 ne = if isFloatType cmm_ty then MO_F_Ne rep else MO_Ne rep
810 mk_lit_switch scrut deflt_blk_id branches
811 = mkCmmIfThenElse cond
812 (mk_lit_switch scrut deflt_blk_id lo_branches)
813 (mk_lit_switch scrut deflt_blk_id hi_branches)
815 n_branches = length branches
816 (mid_lit,_) = branches !! (n_branches `div` 2)
817 -- See notes above re mid_tag
819 (lo_branches, hi_branches) = span is_lo branches
820 is_lo (t,_) = t < mid_lit
822 cond = CmmMachOp (mkLtOp mid_lit)
823 [scrut, CmmLit (mkSimpleLit mid_lit)]
827 label_default :: BlockId -> Maybe CmmAGraph
828 -> (Maybe BlockId -> CmmAGraph)
830 label_default _ Nothing thing_inside
831 = thing_inside Nothing
832 label_default join_lbl (Just code) thing_inside
833 = label_code join_lbl code $ \ lbl ->
834 thing_inside (Just lbl)
837 label_branches :: BlockId -> [(a,CmmAGraph)]
838 -> ([(a,BlockId)] -> CmmAGraph)
840 label_branches _join_lbl [] thing_inside
842 label_branches join_lbl ((tag,code):branches) thing_inside
843 = label_code join_lbl code $ \ lbl ->
844 label_branches join_lbl branches $ \ branches' ->
845 thing_inside ((tag,lbl):branches')
848 label_code :: BlockId -> CmmAGraph -> (BlockId -> CmmAGraph) -> CmmAGraph
849 -- (label_code J code fun)
851 -- [L: code; goto J] fun L
852 label_code join_lbl code thing_inside
853 = withFreshLabel "switch" $ \lbl ->
854 outOfLine (mkLabel lbl <*> code <*> mkBranch join_lbl)
859 assignTemp' :: CmmExpr -> (CmmExpr -> CmmAGraph) -> CmmAGraph
860 assignTemp' e thing_inside
861 | isTrivialCmmExpr e = thing_inside e
862 | otherwise = withTemp (cmmExprType e) $ \ lreg ->
863 let reg = CmmLocal lreg in
864 mkAssign reg e <*> thing_inside (CmmReg reg)
866 withTemp :: CmmType -> (LocalReg -> CmmAGraph) -> CmmAGraph
867 withTemp rep thing_inside
868 = withUnique $ \uniq -> thing_inside (LocalReg uniq rep)
871 -------------------------------------------------------------------------
873 -- Static Reference Tables
875 -------------------------------------------------------------------------
877 -- There is just one SRT for each top level binding; all the nested
878 -- bindings use sub-sections of this SRT. The label is passed down to
879 -- the nested bindings via the monad.
881 getSRTInfo :: SRT -> FCode C_SRT
882 getSRTInfo (SRTEntries {}) = panic "getSRTInfo"
884 getSRTInfo (SRT off len bmp)
885 | len > hALF_WORD_SIZE_IN_BITS || bmp == [fromIntegral srt_escape]
886 = do { id <- newUnique
887 -- ; top_srt <- getSRTLabel
888 ; let srt_desc_lbl = mkLargeSRTLabel id
889 -- JD: We're not constructing and emitting SRTs in the back end,
890 -- which renders this code wrong (it now names a now-non-existent label).
891 -- ; emitRODataLits srt_desc_lbl
892 -- ( cmmLabelOffW top_srt off
893 -- : mkWordCLit (fromIntegral len)
894 -- : map mkWordCLit bmp)
895 ; return (C_SRT srt_desc_lbl 0 srt_escape) }
898 = do { top_srt <- getSRTLabel
899 ; return (C_SRT top_srt off (fromIntegral (head bmp))) }
900 -- The fromIntegral converts to StgHalfWord
903 = -- TODO: Should we panic in this case?
904 -- Someone obviously thinks there should be an SRT
908 srt_escape :: StgHalfWord