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"
55 import ZipCfg hiding (last, unzip, zip)
58 import PprCmm ( {- instances -} )
66 import StgSyn ( SRT(..) )
82 -------------------------------------------------------------------------
86 -------------------------------------------------------------------------
88 cgLit :: Literal -> FCode CmmLit
89 cgLit (MachStr s) = mkByteStringCLit (bytesFS s)
90 -- not unpackFS; we want the UTF-8 byte stream.
91 cgLit other_lit = return (mkSimpleLit other_lit)
93 mkSimpleLit :: Literal -> CmmLit
94 mkSimpleLit (MachChar c) = CmmInt (fromIntegral (ord c)) wordWidth
95 mkSimpleLit MachNullAddr = zeroCLit
96 mkSimpleLit (MachInt i) = CmmInt i wordWidth
97 mkSimpleLit (MachInt64 i) = CmmInt i W64
98 mkSimpleLit (MachWord i) = CmmInt i wordWidth
99 mkSimpleLit (MachWord64 i) = CmmInt i W64
100 mkSimpleLit (MachFloat r) = CmmFloat r W32
101 mkSimpleLit (MachDouble r) = CmmFloat r W64
102 mkSimpleLit (MachLabel fs ms) = CmmLabel (mkForeignLabel fs ms is_dyn)
104 is_dyn = False -- ToDo: fix me
105 mkSimpleLit other = pprPanic "mkSimpleLit" (ppr other)
107 mkLtOp :: Literal -> MachOp
108 -- On signed literals we must do a signed comparison
109 mkLtOp (MachInt _) = MO_S_Lt wordWidth
110 mkLtOp (MachFloat _) = MO_F_Lt W32
111 mkLtOp (MachDouble _) = MO_F_Lt W64
112 mkLtOp lit = MO_U_Lt (typeWidth (cmmLitType (mkSimpleLit lit)))
113 -- ToDo: seems terribly indirect!
116 ---------------------------------------------------
118 -- Cmm data type functions
120 ---------------------------------------------------
122 -- The "B" variants take byte offsets
123 cmmRegOffB :: CmmReg -> ByteOff -> CmmExpr
124 cmmRegOffB = cmmRegOff
126 cmmOffsetB :: CmmExpr -> ByteOff -> CmmExpr
127 cmmOffsetB = cmmOffset
129 cmmOffsetExprB :: CmmExpr -> CmmExpr -> CmmExpr
130 cmmOffsetExprB = cmmOffsetExpr
132 cmmLabelOffB :: CLabel -> ByteOff -> CmmLit
133 cmmLabelOffB = cmmLabelOff
135 cmmOffsetLitB :: CmmLit -> ByteOff -> CmmLit
136 cmmOffsetLitB = cmmOffsetLit
138 -----------------------
139 -- The "W" variants take word offsets
140 cmmOffsetExprW :: CmmExpr -> CmmExpr -> CmmExpr
141 -- The second arg is a *word* offset; need to change it to bytes
142 cmmOffsetExprW e (CmmLit (CmmInt n _)) = cmmOffsetW e (fromInteger n)
143 cmmOffsetExprW e wd_off = cmmIndexExpr wordWidth e wd_off
145 cmmOffsetW :: CmmExpr -> WordOff -> CmmExpr
146 cmmOffsetW e n = cmmOffsetB e (wORD_SIZE * n)
148 cmmRegOffW :: CmmReg -> WordOff -> CmmExpr
149 cmmRegOffW reg wd_off = cmmRegOffB reg (wd_off * wORD_SIZE)
151 cmmOffsetLitW :: CmmLit -> WordOff -> CmmLit
152 cmmOffsetLitW lit wd_off = cmmOffsetLitB lit (wORD_SIZE * wd_off)
154 cmmLabelOffW :: CLabel -> WordOff -> CmmLit
155 cmmLabelOffW lbl wd_off = cmmLabelOffB lbl (wORD_SIZE * wd_off)
157 cmmLoadIndexW :: CmmExpr -> Int -> CmmType -> CmmExpr
158 cmmLoadIndexW base off ty = CmmLoad (cmmOffsetW base off) ty
160 -----------------------
161 cmmULtWord, cmmUGeWord, cmmUGtWord, cmmSubWord,
162 cmmNeWord, cmmEqWord, cmmOrWord, cmmAndWord
163 :: CmmExpr -> CmmExpr -> CmmExpr
164 cmmOrWord e1 e2 = CmmMachOp mo_wordOr [e1, e2]
165 cmmAndWord e1 e2 = CmmMachOp mo_wordAnd [e1, e2]
166 cmmNeWord e1 e2 = CmmMachOp mo_wordNe [e1, e2]
167 cmmEqWord e1 e2 = CmmMachOp mo_wordEq [e1, e2]
168 cmmULtWord e1 e2 = CmmMachOp mo_wordULt [e1, e2]
169 cmmUGeWord e1 e2 = CmmMachOp mo_wordUGe [e1, e2]
170 cmmUGtWord e1 e2 = CmmMachOp mo_wordUGt [e1, e2]
171 --cmmShlWord e1 e2 = CmmMachOp mo_wordShl [e1, e2]
172 --cmmUShrWord e1 e2 = CmmMachOp mo_wordUShr [e1, e2]
173 cmmSubWord e1 e2 = CmmMachOp mo_wordSub [e1, e2]
175 cmmNegate :: CmmExpr -> CmmExpr
176 cmmNegate (CmmLit (CmmInt n rep)) = CmmLit (CmmInt (-n) rep)
177 cmmNegate e = CmmMachOp (MO_S_Neg (cmmExprWidth e)) [e]
179 blankWord :: CmmStatic
180 blankWord = CmmUninitialised wORD_SIZE
184 --cmmTagBits = CmmLit (mkIntCLit tAG_BITS)
185 cmmTagMask, cmmPointerMask :: CmmExpr
186 cmmTagMask = CmmLit (mkIntCLit tAG_MASK)
187 cmmPointerMask = CmmLit (mkIntCLit (complement tAG_MASK))
189 -- Used to untag a possibly tagged pointer
190 -- A static label need not be untagged
191 cmmUntag, cmmGetTag :: CmmExpr -> CmmExpr
192 cmmUntag e@(CmmLit (CmmLabel _)) = e
194 cmmUntag e = (e `cmmAndWord` cmmPointerMask)
196 cmmGetTag e = (e `cmmAndWord` cmmTagMask)
198 -- Test if a closure pointer is untagged
199 cmmIsTagged :: CmmExpr -> CmmExpr
200 cmmIsTagged e = (e `cmmAndWord` cmmTagMask)
201 `cmmNeWord` CmmLit zeroCLit
203 cmmConstrTag, cmmConstrTag1 :: CmmExpr -> CmmExpr
204 cmmConstrTag e = (e `cmmAndWord` cmmTagMask) `cmmSubWord` (CmmLit (mkIntCLit 1))
205 -- Get constructor tag, but one based.
206 cmmConstrTag1 e = e `cmmAndWord` cmmTagMask
208 -----------------------
211 mkWordCLit :: StgWord -> CmmLit
212 mkWordCLit wd = CmmInt (fromIntegral wd) wordWidth
214 packHalfWordsCLit :: (Integral a, Integral b) => a -> b -> CmmLit
215 -- Make a single word literal in which the lower_half_word is
216 -- at the lower address, and the upper_half_word is at the
218 -- ToDo: consider using half-word lits instead
219 -- but be careful: that's vulnerable when reversed
220 packHalfWordsCLit lower_half_word upper_half_word
221 #ifdef WORDS_BIGENDIAN
222 = mkWordCLit ((fromIntegral lower_half_word `shiftL` hALF_WORD_SIZE_IN_BITS)
223 .|. fromIntegral upper_half_word)
225 = mkWordCLit ((fromIntegral lower_half_word)
226 .|. (fromIntegral upper_half_word `shiftL` hALF_WORD_SIZE_IN_BITS))
229 --------------------------------------------------------------------------
231 -- Incrementing a memory location
233 --------------------------------------------------------------------------
235 addToMemLbl :: CmmType -> CLabel -> Int -> CmmAGraph
236 addToMemLbl rep lbl n = addToMem rep (CmmLit (CmmLabel lbl)) n
238 addToMem :: CmmType -- rep of the counter
239 -> CmmExpr -- Address
240 -> Int -- What to add (a word)
242 addToMem rep ptr n = addToMemE rep ptr (CmmLit (CmmInt (toInteger n) (typeWidth rep)))
244 addToMemE :: CmmType -- rep of the counter
245 -> CmmExpr -- Address
246 -> CmmExpr -- What to add (a word-typed expression)
249 = mkStore ptr (CmmMachOp (MO_Add (typeWidth rep)) [CmmLoad ptr rep, n])
252 -------------------------------------------------------------------------
254 -- Loading a field from an object,
255 -- where the object pointer is itself tagged
257 -------------------------------------------------------------------------
259 mkTaggedObjectLoad :: LocalReg -> LocalReg -> WordOff -> DynTag -> CmmAGraph
260 -- (loadTaggedObjectField reg base off tag) generates assignment
261 -- reg = bitsK[ base + off - tag ]
262 -- where K is fixed by 'reg'
263 mkTaggedObjectLoad reg base offset tag
264 = mkAssign (CmmLocal reg)
265 (CmmLoad (cmmOffsetB (CmmReg (CmmLocal base))
266 (wORD_SIZE*offset - tag))
269 -------------------------------------------------------------------------
271 -- Converting a closure tag to a closure for enumeration types
272 -- (this is the implementation of tagToEnum#).
274 -------------------------------------------------------------------------
276 tagToClosure :: TyCon -> CmmExpr -> CmmExpr
277 tagToClosure tycon tag
278 = CmmLoad (cmmOffsetExprW closure_tbl tag) bWord
279 where closure_tbl = CmmLit (CmmLabel lbl)
280 lbl = mkClosureTableLabel (tyConName tycon) NoCafRefs
282 -------------------------------------------------------------------------
284 -- Conditionals and rts calls
286 -------------------------------------------------------------------------
288 emitRtsCall :: LitString -> [(CmmExpr,ForeignHint)] -> Bool -> FCode ()
289 emitRtsCall fun args safe = emitRtsCall' [] fun args Nothing safe
290 -- The 'Nothing' says "save all global registers"
292 emitRtsCallWithVols :: LitString -> [(CmmExpr,ForeignHint)] -> [GlobalReg] -> Bool -> FCode ()
293 emitRtsCallWithVols fun args vols safe
294 = emitRtsCall' [] fun args (Just vols) safe
296 emitRtsCallWithResult :: LocalReg -> ForeignHint -> LitString
297 -> [(CmmExpr,ForeignHint)] -> Bool -> FCode ()
298 emitRtsCallWithResult res hint fun args safe
299 = emitRtsCall' [(res,hint)] fun args Nothing safe
301 -- Make a call to an RTS C procedure
303 :: [(LocalReg,ForeignHint)]
305 -> [(CmmExpr,ForeignHint)]
307 -> Bool -- True <=> CmmSafe call
309 emitRtsCall' res fun args _vols safe
310 = --error "emitRtsCall'"
311 do { updfr_off <- getUpdFrameOff
313 ; emit $ call updfr_off
318 mkCall fun_expr Native res' args' updfr_off
320 mkUnsafeCall (ForeignTarget fun_expr
321 (ForeignConvention CCallConv arg_hints res_hints)) res' args'
322 (args', arg_hints) = unzip args
323 (res', res_hints) = unzip res
324 (caller_save, caller_load) = callerSaveVolatileRegs
325 fun_expr = mkLblExpr (mkRtsCodeLabel fun)
328 -----------------------------------------------------------------------------
330 -- Caller-Save Registers
332 -----------------------------------------------------------------------------
334 -- Here we generate the sequence of saves/restores required around a
335 -- foreign call instruction.
337 -- TODO: reconcile with includes/Regs.h
338 -- * Regs.h claims that BaseReg should be saved last and loaded first
339 -- * This might not have been tickled before since BaseReg is callee save
340 -- * Regs.h saves SparkHd, ParkT1, SparkBase and SparkLim
341 callerSaveVolatileRegs :: (CmmAGraph, CmmAGraph)
342 callerSaveVolatileRegs = (caller_save, caller_load)
344 caller_save = catAGraphs (map callerSaveGlobalReg regs_to_save)
345 caller_load = catAGraphs (map callerRestoreGlobalReg regs_to_save)
347 system_regs = [ Sp,SpLim,Hp,HpLim,CurrentTSO,CurrentNursery
348 {- ,SparkHd,SparkTl,SparkBase,SparkLim -}
351 regs_to_save = filter callerSaves system_regs
353 callerSaveGlobalReg reg
354 = mkStore (get_GlobalReg_addr reg) (CmmReg (CmmGlobal reg))
356 callerRestoreGlobalReg reg
357 = mkAssign (CmmGlobal reg)
358 (CmmLoad (get_GlobalReg_addr reg) (globalRegType reg))
360 -- -----------------------------------------------------------------------------
363 -- We map STG registers onto appropriate CmmExprs. Either they map
364 -- to real machine registers or stored as offsets from BaseReg. Given
365 -- a GlobalReg, get_GlobalReg_addr always produces the
366 -- register table address for it.
367 -- (See also get_GlobalReg_reg_or_addr in MachRegs)
369 get_GlobalReg_addr :: GlobalReg -> CmmExpr
370 get_GlobalReg_addr BaseReg = regTableOffset 0
371 get_GlobalReg_addr mid = get_Regtable_addr_from_offset
372 (globalRegType mid) (baseRegOffset mid)
374 -- Calculate a literal representing an offset into the register table.
375 -- Used when we don't have an actual BaseReg to offset from.
376 regTableOffset :: Int -> CmmExpr
378 CmmLit (CmmLabelOff mkMainCapabilityLabel (oFFSET_Capability_r + n))
380 get_Regtable_addr_from_offset :: CmmType -> Int -> CmmExpr
381 get_Regtable_addr_from_offset _rep offset =
383 CmmRegOff (CmmGlobal BaseReg) offset
385 regTableOffset offset
389 -- | Returns 'True' if this global register is stored in a caller-saves
392 callerSaves :: GlobalReg -> Bool
394 #ifdef CALLER_SAVES_Base
395 callerSaves BaseReg = True
397 #ifdef CALLER_SAVES_Sp
398 callerSaves Sp = True
400 #ifdef CALLER_SAVES_SpLim
401 callerSaves SpLim = True
403 #ifdef CALLER_SAVES_Hp
404 callerSaves Hp = True
406 #ifdef CALLER_SAVES_HpLim
407 callerSaves HpLim = True
409 #ifdef CALLER_SAVES_CurrentTSO
410 callerSaves CurrentTSO = True
412 #ifdef CALLER_SAVES_CurrentNursery
413 callerSaves CurrentNursery = True
415 callerSaves _ = False
418 -- -----------------------------------------------------------------------------
419 -- Information about global registers
421 baseRegOffset :: GlobalReg -> Int
423 baseRegOffset Sp = oFFSET_StgRegTable_rSp
424 baseRegOffset SpLim = oFFSET_StgRegTable_rSpLim
425 baseRegOffset (LongReg 1) = oFFSET_StgRegTable_rL1
426 baseRegOffset Hp = oFFSET_StgRegTable_rHp
427 baseRegOffset HpLim = oFFSET_StgRegTable_rHpLim
428 baseRegOffset CurrentTSO = oFFSET_StgRegTable_rCurrentTSO
429 baseRegOffset CurrentNursery = oFFSET_StgRegTable_rCurrentNursery
430 baseRegOffset HpAlloc = oFFSET_StgRegTable_rHpAlloc
431 baseRegOffset GCEnter1 = oFFSET_stgGCEnter1
432 baseRegOffset GCFun = oFFSET_stgGCFun
433 baseRegOffset reg = pprPanic "baseRegOffset:" (ppr reg)
435 -------------------------------------------------------------------------
437 -- Strings generate a top-level data block
439 -------------------------------------------------------------------------
441 emitDataLits :: CLabel -> [CmmLit] -> FCode ()
442 -- Emit a data-segment data block
443 emitDataLits lbl lits
444 = emitData Data (CmmDataLabel lbl : map CmmStaticLit lits)
446 mkDataLits :: CLabel -> [CmmLit] -> GenCmmTop CmmStatic info stmt
447 -- Emit a data-segment data block
449 = CmmData Data (CmmDataLabel lbl : map CmmStaticLit lits)
451 emitRODataLits :: CLabel -> [CmmLit] -> FCode ()
452 -- Emit a read-only data block
453 emitRODataLits lbl lits
454 = emitData section (CmmDataLabel lbl : map CmmStaticLit lits)
455 where section | any needsRelocation lits = RelocatableReadOnlyData
456 | otherwise = ReadOnlyData
457 needsRelocation (CmmLabel _) = True
458 needsRelocation (CmmLabelOff _ _) = True
459 needsRelocation _ = False
461 mkRODataLits :: CLabel -> [CmmLit] -> GenCmmTop CmmStatic info stmt
462 mkRODataLits lbl lits
463 = CmmData section (CmmDataLabel lbl : map CmmStaticLit lits)
464 where section | any needsRelocation lits = RelocatableReadOnlyData
465 | otherwise = ReadOnlyData
466 needsRelocation (CmmLabel _) = True
467 needsRelocation (CmmLabelOff _ _) = True
468 needsRelocation _ = False
470 mkStringCLit :: String -> FCode CmmLit
471 -- Make a global definition for the string,
472 -- and return its label
473 mkStringCLit str = mkByteStringCLit (map (fromIntegral . ord) str)
475 mkByteStringCLit :: [Word8] -> FCode CmmLit
476 mkByteStringCLit bytes
477 = do { uniq <- newUnique
478 ; let lbl = mkStringLitLabel uniq
479 ; emitData ReadOnlyData [CmmDataLabel lbl, CmmString bytes]
480 ; return (CmmLabel lbl) }
482 -------------------------------------------------------------------------
484 -- Assigning expressions to temporaries
486 -------------------------------------------------------------------------
488 assignTemp :: CmmExpr -> FCode LocalReg
489 -- Make sure the argument is in a local register
490 assignTemp (CmmReg (CmmLocal reg)) = return reg
491 assignTemp e = do { uniq <- newUnique
492 ; let reg = LocalReg uniq (cmmExprType e)
493 ; emit (mkAssign (CmmLocal reg) e)
496 newTemp :: CmmType -> FCode LocalReg
497 newTemp rep = do { uniq <- newUnique
498 ; return (LocalReg uniq rep) }
500 newUnboxedTupleRegs :: Type -> FCode ([LocalReg], [ForeignHint])
501 -- Choose suitable local regs to use for the components
502 -- of an unboxed tuple that we are about to return to
503 -- the Sequel. If the Sequel is a joint point, using the
504 -- regs it wants will save later assignments.
505 newUnboxedTupleRegs res_ty
506 = ASSERT( isUnboxedTupleType res_ty )
507 do { sequel <- getSequel
508 ; regs <- choose_regs sequel
509 ; ASSERT( regs `equalLength` reps )
510 return (regs, map primRepForeignHint reps) }
512 ty_args = tyConAppArgs (repType res_ty)
515 , let rep = typePrimRep ty
516 , not (isVoidRep rep) ]
517 choose_regs (AssignTo regs _) = return regs
518 choose_regs _other = mapM (newTemp . primRepCmmType) reps
522 -------------------------------------------------------------------------
524 -------------------------------------------------------------------------
526 mkMultiAssign :: [LocalReg] -> [CmmExpr] -> CmmAGraph
527 -- Emit code to perform the assignments in the
528 -- input simultaneously, using temporary variables when necessary.
531 type Vrtx = (Key, Stmt) -- Give each vertex a unique number,
532 -- for fast comparison
533 type Stmt = (LocalReg, CmmExpr) -- r := e
535 -- We use the strongly-connected component algorithm, in which
536 -- * the vertices are the statements
537 -- * an edge goes from s1 to s2 iff
538 -- s1 assigns to something s2 uses
539 -- that is, if s1 should *follow* s2 in the final order
541 mkMultiAssign [] [] = mkNop
542 mkMultiAssign [reg] [rhs] = mkAssign (CmmLocal reg) rhs
543 mkMultiAssign regs rhss = ASSERT( equalLength regs rhss )
544 unscramble ([1..] `zip` (regs `zip` rhss))
546 unscramble :: [Vrtx] -> CmmAGraph
548 = catAGraphs (map do_component components)
550 edges :: [ (Vrtx, Key, [Key]) ]
551 edges = [ (vertex, key1, edges_from stmt1)
552 | vertex@(key1, stmt1) <- vertices ]
554 edges_from :: Stmt -> [Key]
555 edges_from stmt1 = [ key2 | (key2, stmt2) <- vertices,
556 stmt1 `mustFollow` stmt2 ]
558 components :: [SCC Vrtx]
559 components = stronglyConnCompFromEdgedVertices edges
561 -- do_components deal with one strongly-connected component
562 -- Not cyclic, or singleton? Just do it
563 do_component :: SCC Vrtx -> CmmAGraph
564 do_component (AcyclicSCC (_,stmt)) = mk_graph stmt
565 do_component (CyclicSCC []) = panic "do_component"
566 do_component (CyclicSCC [(_,stmt)]) = mk_graph stmt
568 -- Cyclic? Then go via temporaries. Pick one to
569 -- break the loop and try again with the rest.
570 do_component (CyclicSCC ((_,first_stmt) : rest))
572 let (to_tmp, from_tmp) = split u first_stmt
575 <*> mk_graph from_tmp
577 split :: Unique -> Stmt -> (Stmt, Stmt)
578 split uniq (reg, rhs)
579 = ((tmp, rhs), (reg, CmmReg (CmmLocal tmp)))
581 rep = cmmExprType rhs
582 tmp = LocalReg uniq rep
584 mk_graph :: Stmt -> CmmAGraph
585 mk_graph (reg, rhs) = mkAssign (CmmLocal reg) rhs
587 mustFollow :: Stmt -> Stmt -> Bool
588 (reg, _) `mustFollow` (_, rhs) = reg `regUsedIn` rhs
590 regUsedIn :: LocalReg -> CmmExpr -> Bool
591 reg `regUsedIn` CmmLoad e _ = reg `regUsedIn` e
592 reg `regUsedIn` CmmReg (CmmLocal reg') = reg == reg'
593 reg `regUsedIn` CmmRegOff (CmmLocal reg') _ = reg == reg'
594 reg `regUsedIn` CmmMachOp _ es = any (reg `regUsedIn`) es
595 _reg `regUsedIn` _other = False -- The CmmGlobal cases
598 -------------------------------------------------------------------------
600 -------------------------------------------------------------------------
603 emitSwitch :: CmmExpr -- Tag to switch on
604 -> [(ConTagZ, CmmAGraph)] -- Tagged branches
605 -> Maybe CmmAGraph -- Default branch (if any)
606 -> ConTagZ -> ConTagZ -- Min and Max possible values; behaviour
607 -- outside this range is undefined
609 emitSwitch tag_expr branches mb_deflt lo_tag hi_tag
610 = do { dflags <- getDynFlags
611 ; emit (mkCmmSwitch (via_C dflags) tag_expr branches mb_deflt lo_tag hi_tag) }
613 via_C dflags | HscC <- hscTarget dflags = True
617 mkCmmSwitch :: Bool -- True <=> never generate a conditional tree
618 -> CmmExpr -- Tag to switch on
619 -> [(ConTagZ, CmmAGraph)] -- Tagged branches
620 -> Maybe CmmAGraph -- Default branch (if any)
621 -> ConTagZ -> ConTagZ -- Min and Max possible values; behaviour
622 -- outside this range is undefined
625 -- First, two rather common cases in which there is no work to do
626 mkCmmSwitch _ _ [] (Just code) _ _ = code
627 mkCmmSwitch _ _ [(_,code)] Nothing _ _ = code
630 mkCmmSwitch via_C tag_expr branches mb_deflt lo_tag hi_tag
631 = withFreshLabel "switch join" $ \ join_lbl ->
632 label_default join_lbl mb_deflt $ \ mb_deflt ->
633 label_branches join_lbl branches $ \ branches ->
634 assignTemp' tag_expr $ \tag_expr' ->
636 mk_switch tag_expr' (sortLe le branches) mb_deflt
638 -- Sort the branches before calling mk_switch
639 <*> mkLabel join_lbl emptyStackInfo
642 (t1,_) `le` (t2,_) = t1 <= t2
644 mk_switch :: CmmExpr -> [(ConTagZ, BlockId)]
646 -> ConTagZ -> ConTagZ -> Bool
649 -- SINGLETON TAG RANGE: no case analysis to do
650 mk_switch _tag_expr [(tag, lbl)] _ lo_tag hi_tag _via_C
652 = ASSERT( tag == lo_tag )
655 -- SINGLETON BRANCH, NO DEFAULT: no case analysis to do
656 mk_switch _tag_expr [(_tag,lbl)] Nothing _ _ _
658 -- The simplifier might have eliminated a case
659 -- so we may have e.g. case xs of
661 -- In that situation we can be sure the (:) case
662 -- can't happen, so no need to test
664 -- SINGLETON BRANCH: one equality check to do
665 mk_switch tag_expr [(tag,lbl)] (Just deflt) _ _ _
666 = mkCbranch cond deflt lbl
668 cond = cmmNeWord tag_expr (CmmLit (mkIntCLit tag))
669 -- We have lo_tag < hi_tag, but there's only one branch,
670 -- so there must be a default
672 -- ToDo: we might want to check for the two branch case, where one of
673 -- the branches is the tag 0, because comparing '== 0' is likely to be
674 -- more efficient than other kinds of comparison.
676 -- DENSE TAG RANGE: use a switch statment.
678 -- We also use a switch uncoditionally when compiling via C, because
679 -- this will get emitted as a C switch statement and the C compiler
680 -- should do a good job of optimising it. Also, older GCC versions
681 -- (2.95 in particular) have problems compiling the complicated
682 -- if-trees generated by this code, so compiling to a switch every
683 -- time works around that problem.
685 mk_switch tag_expr branches mb_deflt lo_tag hi_tag via_C
686 | use_switch -- Use a switch
688 find_branch :: ConTagZ -> Maybe BlockId
689 find_branch i = case (assocMaybe branches i) of
693 -- NB. we have eliminated impossible branches at
694 -- either end of the range (see below), so the first
695 -- tag of a real branch is real_lo_tag (not lo_tag).
696 arms :: [Maybe BlockId]
697 arms = [ find_branch i | i <- [real_lo_tag..real_hi_tag]]
699 mkSwitch (cmmOffset tag_expr (- real_lo_tag)) arms
701 -- if we can knock off a bunch of default cases with one if, then do so
702 | Just deflt <- mb_deflt, (lowest_branch - lo_tag) >= n_branches
704 (cmmULtWord tag_expr (CmmLit (mkIntCLit lowest_branch)))
706 (mk_switch tag_expr branches mb_deflt
707 lowest_branch hi_tag via_C)
709 | Just deflt <- mb_deflt, (hi_tag - highest_branch) >= n_branches
711 (cmmUGtWord tag_expr (CmmLit (mkIntCLit highest_branch)))
713 (mk_switch tag_expr branches mb_deflt
714 lo_tag highest_branch via_C)
716 | otherwise -- Use an if-tree
718 (cmmUGeWord tag_expr (CmmLit (mkIntCLit mid_tag)))
719 (mk_switch tag_expr hi_branches mb_deflt
720 mid_tag hi_tag via_C)
721 (mk_switch tag_expr lo_branches mb_deflt
722 lo_tag (mid_tag-1) via_C)
723 -- we test (e >= mid_tag) rather than (e < mid_tag), because
724 -- the former works better when e is a comparison, and there
725 -- are two tags 0 & 1 (mid_tag == 1). In this case, the code
726 -- generator can reduce the condition to e itself without
727 -- having to reverse the sense of the comparison: comparisons
728 -- can't always be easily reversed (eg. floating
731 use_switch = {- pprTrace "mk_switch" (
732 ppr tag_expr <+> text "n_tags:" <+> int n_tags <+>
733 text "branches:" <+> ppr (map fst branches) <+>
734 text "n_branches:" <+> int n_branches <+>
735 text "lo_tag:" <+> int lo_tag <+>
736 text "hi_tag:" <+> int hi_tag <+>
737 text "real_lo_tag:" <+> int real_lo_tag <+>
738 text "real_hi_tag:" <+> int real_hi_tag) $ -}
739 ASSERT( n_branches > 1 && n_tags > 1 )
740 n_tags > 2 && (via_C || (dense && big_enough))
741 -- up to 4 branches we use a decision tree, otherwise
742 -- a switch (== jump table in the NCG). This seems to be
743 -- optimal, and corresponds with what gcc does.
744 big_enough = n_branches > 4
745 dense = n_branches > (n_tags `div` 2)
746 n_branches = length branches
748 -- ignore default slots at each end of the range if there's
749 -- no default branch defined.
750 lowest_branch = fst (head branches)
751 highest_branch = fst (last branches)
754 | isNothing mb_deflt = lowest_branch
758 | isNothing mb_deflt = highest_branch
761 n_tags = real_hi_tag - real_lo_tag + 1
763 -- INVARIANT: Provided hi_tag > lo_tag (which is true)
764 -- lo_tag <= mid_tag < hi_tag
765 -- lo_branches have tags < mid_tag
766 -- hi_branches have tags >= mid_tag
768 (mid_tag,_) = branches !! (n_branches `div` 2)
769 -- 2 branches => n_branches `div` 2 = 1
770 -- => branches !! 1 give the *second* tag
771 -- There are always at least 2 branches here
773 (lo_branches, hi_branches) = span is_lo branches
774 is_lo (t,_) = t < mid_tag
777 mkCmmLitSwitch :: CmmExpr -- Tag to switch on
778 -> [(Literal, CmmAGraph)] -- Tagged branches
779 -> CmmAGraph -- Default branch (always)
780 -> CmmAGraph -- Emit the code
781 -- Used for general literals, whose size might not be a word,
782 -- where there is always a default case, and where we don't know
783 -- the range of values for certain. For simplicity we always generate a tree.
785 -- ToDo: for integers we could do better here, perhaps by generalising
786 -- mk_switch and using that. --SDM 15/09/2004
787 mkCmmLitSwitch _scrut [] deflt = deflt
788 mkCmmLitSwitch scrut branches deflt
789 = assignTemp' scrut $ \ scrut' ->
790 withFreshLabel "switch join" $ \ join_lbl ->
791 label_code join_lbl deflt $ \ deflt ->
792 label_branches join_lbl branches $ \ branches ->
793 mk_lit_switch scrut' deflt (sortLe le branches)
794 <*> mkLabel join_lbl emptyStackInfo
796 le (t1,_) (t2,_) = t1 <= t2
798 mk_lit_switch :: CmmExpr -> BlockId
799 -> [(Literal,BlockId)]
801 mk_lit_switch scrut deflt [(lit,blk)]
802 = mkCbranch (CmmMachOp ne [scrut, CmmLit cmm_lit]) deflt blk
804 cmm_lit = mkSimpleLit lit
805 cmm_ty = cmmLitType cmm_lit
806 rep = typeWidth cmm_ty
807 ne = if isFloatType cmm_ty then MO_F_Ne rep else MO_Ne rep
809 mk_lit_switch scrut deflt_blk_id branches
810 = mkCmmIfThenElse cond
811 (mk_lit_switch scrut deflt_blk_id lo_branches)
812 (mk_lit_switch scrut deflt_blk_id hi_branches)
814 n_branches = length branches
815 (mid_lit,_) = branches !! (n_branches `div` 2)
816 -- See notes above re mid_tag
818 (lo_branches, hi_branches) = span is_lo branches
819 is_lo (t,_) = t < mid_lit
821 cond = CmmMachOp (mkLtOp mid_lit)
822 [scrut, CmmLit (mkSimpleLit mid_lit)]
826 label_default :: BlockId -> Maybe CmmAGraph
827 -> (Maybe BlockId -> CmmAGraph)
829 label_default _ Nothing thing_inside
830 = thing_inside Nothing
831 label_default join_lbl (Just code) thing_inside
832 = label_code join_lbl code $ \ lbl ->
833 thing_inside (Just lbl)
836 label_branches :: BlockId -> [(a,CmmAGraph)]
837 -> ([(a,BlockId)] -> CmmAGraph)
839 label_branches _join_lbl [] thing_inside
841 label_branches join_lbl ((tag,code):branches) thing_inside
842 = label_code join_lbl code $ \ lbl ->
843 label_branches join_lbl branches $ \ branches' ->
844 thing_inside ((tag,lbl):branches')
847 label_code :: BlockId -> CmmAGraph -> (BlockId -> CmmAGraph) -> CmmAGraph
848 -- (label_code J code fun)
850 -- [L: code; goto J] fun L
851 label_code join_lbl code thing_inside
852 = withFreshLabel "switch" $ \lbl ->
853 outOfLine (mkLabel lbl emptyStackInfo <*> code <*> mkBranch join_lbl)
858 assignTemp' :: CmmExpr -> (CmmExpr -> CmmAGraph) -> CmmAGraph
859 assignTemp' e thing_inside
860 | isTrivialCmmExpr e = thing_inside e
861 | otherwise = withTemp (cmmExprType e) $ \ lreg ->
862 let reg = CmmLocal lreg in
863 mkAssign reg e <*> thing_inside (CmmReg reg)
865 withTemp :: CmmType -> (LocalReg -> CmmAGraph) -> CmmAGraph
866 withTemp rep thing_inside
867 = withUnique $ \uniq -> thing_inside (LocalReg uniq rep)
870 -------------------------------------------------------------------------
872 -- Static Reference Tables
874 -------------------------------------------------------------------------
876 -- There is just one SRT for each top level binding; all the nested
877 -- bindings use sub-sections of this SRT. The label is passed down to
878 -- the nested bindings via the monad.
880 getSRTInfo :: SRT -> FCode C_SRT
881 getSRTInfo (SRTEntries {}) = panic "getSRTInfo"
883 getSRTInfo (SRT off len bmp)
884 | len > hALF_WORD_SIZE_IN_BITS || bmp == [fromIntegral srt_escape]
885 = do { id <- newUnique
886 -- ; top_srt <- getSRTLabel
887 ; let srt_desc_lbl = mkLargeSRTLabel id
888 -- JD: We're not constructing and emitting SRTs in the back end,
889 -- which renders this code wrong (it now names a now-non-existent label).
890 -- ; emitRODataLits srt_desc_lbl
891 -- ( cmmLabelOffW top_srt off
892 -- : mkWordCLit (fromIntegral len)
893 -- : map mkWordCLit bmp)
894 ; return (C_SRT srt_desc_lbl 0 srt_escape) }
897 = do { top_srt <- getSRTLabel
898 ; return (C_SRT top_srt off (fromIntegral (head bmp))) }
899 -- The fromIntegral converts to StgHalfWord
902 = -- TODO: Should we panic in this case?
903 -- Someone obviously thinks there should be an SRT
907 srt_escape :: StgHalfWord