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 callerSaves, 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"
53 import CmmExpr hiding (regUsedIn)
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 -- EZY: This code is very dodgy, because callerSaves only ever
344 -- returns true in the current universe for registers NOT in
345 -- system_regs (just do a grep for CALLER_SAVES in
346 -- includes/stg/MachRegs.h). Thus, this is all one giant no-op. What we are
347 -- actually interested in is saving are the non-system registers, which
348 -- we is what the old code generator actually does at this point.
349 -- Unfortunately, we can't do that here either, because we don't
350 -- liveness information, and thus there's not an easy way to tell which
351 -- specific global registers need to be saved (the 'vols' argument in
352 -- the old code generator.) One possible hack is to save all of them
353 -- unconditionally, but unless we have very clever dead /memory/
354 -- elimination (unlikely), this will still leave a dead, unnecessary
355 -- memory assignment. And really, we shouldn't be doing the workaround
356 -- at this point in the pipeline, see Note [Register parameter passing].
357 -- Right now the workaround is to avoid inlining across unsafe foreign
358 -- calls in rewriteAssignments.
359 callerSaveVolatileRegs :: (CmmAGraph, CmmAGraph)
360 callerSaveVolatileRegs = (caller_save, caller_load)
362 caller_save = catAGraphs (map callerSaveGlobalReg regs_to_save)
363 caller_load = catAGraphs (map callerRestoreGlobalReg regs_to_save)
365 system_regs = [ Sp,SpLim,Hp,HpLim,CurrentTSO,CurrentNursery
366 {- ,SparkHd,SparkTl,SparkBase,SparkLim -}
369 regs_to_save = filter callerSaves system_regs
371 callerSaveGlobalReg reg
372 = mkStore (get_GlobalReg_addr reg) (CmmReg (CmmGlobal reg))
374 callerRestoreGlobalReg reg
375 = mkAssign (CmmGlobal reg)
376 (CmmLoad (get_GlobalReg_addr reg) (globalRegType reg))
378 -- -----------------------------------------------------------------------------
381 -- We map STG registers onto appropriate CmmExprs. Either they map
382 -- to real machine registers or stored as offsets from BaseReg. Given
383 -- a GlobalReg, get_GlobalReg_addr always produces the
384 -- register table address for it.
385 -- (See also get_GlobalReg_reg_or_addr in MachRegs)
387 get_GlobalReg_addr :: GlobalReg -> CmmExpr
388 get_GlobalReg_addr BaseReg = regTableOffset 0
389 get_GlobalReg_addr mid = get_Regtable_addr_from_offset
390 (globalRegType mid) (baseRegOffset mid)
392 -- Calculate a literal representing an offset into the register table.
393 -- Used when we don't have an actual BaseReg to offset from.
394 regTableOffset :: Int -> CmmExpr
396 CmmLit (CmmLabelOff mkMainCapabilityLabel (oFFSET_Capability_r + n))
398 get_Regtable_addr_from_offset :: CmmType -> Int -> CmmExpr
399 get_Regtable_addr_from_offset _rep offset =
401 CmmRegOff (CmmGlobal BaseReg) offset
403 regTableOffset offset
407 -- | Returns 'True' if this global register is stored in a caller-saves
410 callerSaves :: GlobalReg -> Bool
412 #ifdef CALLER_SAVES_Base
413 callerSaves BaseReg = True
415 #ifdef CALLER_SAVES_R1
416 callerSaves (VanillaReg 1 _) = True
418 #ifdef CALLER_SAVES_R2
419 callerSaves (VanillaReg 2 _) = True
421 #ifdef CALLER_SAVES_R3
422 callerSaves (VanillaReg 3 _) = True
424 #ifdef CALLER_SAVES_R4
425 callerSaves (VanillaReg 4 _) = True
427 #ifdef CALLER_SAVES_R5
428 callerSaves (VanillaReg 5 _) = True
430 #ifdef CALLER_SAVES_R6
431 callerSaves (VanillaReg 6 _) = True
433 #ifdef CALLER_SAVES_R7
434 callerSaves (VanillaReg 7 _) = True
436 #ifdef CALLER_SAVES_R8
437 callerSaves (VanillaReg 8 _) = True
439 #ifdef CALLER_SAVES_F1
440 callerSaves (FloatReg 1) = True
442 #ifdef CALLER_SAVES_F2
443 callerSaves (FloatReg 2) = True
445 #ifdef CALLER_SAVES_F3
446 callerSaves (FloatReg 3) = True
448 #ifdef CALLER_SAVES_F4
449 callerSaves (FloatReg 4) = True
451 #ifdef CALLER_SAVES_D1
452 callerSaves (DoubleReg 1) = True
454 #ifdef CALLER_SAVES_D2
455 callerSaves (DoubleReg 2) = True
457 #ifdef CALLER_SAVES_L1
458 callerSaves (LongReg 1) = True
460 #ifdef CALLER_SAVES_Sp
461 callerSaves Sp = True
463 #ifdef CALLER_SAVES_SpLim
464 callerSaves SpLim = True
466 #ifdef CALLER_SAVES_Hp
467 callerSaves Hp = True
469 #ifdef CALLER_SAVES_HpLim
470 callerSaves HpLim = True
472 #ifdef CALLER_SAVES_CurrentTSO
473 callerSaves CurrentTSO = True
475 #ifdef CALLER_SAVES_CurrentNursery
476 callerSaves CurrentNursery = True
478 callerSaves _ = False
481 -- -----------------------------------------------------------------------------
482 -- Information about global registers
484 baseRegOffset :: GlobalReg -> Int
486 baseRegOffset Sp = oFFSET_StgRegTable_rSp
487 baseRegOffset SpLim = oFFSET_StgRegTable_rSpLim
488 baseRegOffset (LongReg 1) = oFFSET_StgRegTable_rL1
489 baseRegOffset Hp = oFFSET_StgRegTable_rHp
490 baseRegOffset HpLim = oFFSET_StgRegTable_rHpLim
491 baseRegOffset CurrentTSO = oFFSET_StgRegTable_rCurrentTSO
492 baseRegOffset CurrentNursery = oFFSET_StgRegTable_rCurrentNursery
493 baseRegOffset HpAlloc = oFFSET_StgRegTable_rHpAlloc
494 baseRegOffset GCEnter1 = oFFSET_stgGCEnter1
495 baseRegOffset GCFun = oFFSET_stgGCFun
496 baseRegOffset reg = pprPanic "baseRegOffset:" (ppr reg)
498 -------------------------------------------------------------------------
500 -- Strings generate a top-level data block
502 -------------------------------------------------------------------------
504 emitDataLits :: CLabel -> [CmmLit] -> FCode ()
505 -- Emit a data-segment data block
506 emitDataLits lbl lits
507 = emitData Data (CmmDataLabel lbl : map CmmStaticLit lits)
509 mkDataLits :: CLabel -> [CmmLit] -> GenCmmTop CmmStatic info stmt
510 -- Emit a data-segment data block
512 = CmmData Data (CmmDataLabel lbl : map CmmStaticLit lits)
514 emitRODataLits :: CLabel -> [CmmLit] -> FCode ()
515 -- Emit a read-only data block
516 emitRODataLits lbl lits
517 = emitData section (CmmDataLabel lbl : map CmmStaticLit lits)
518 where section | any needsRelocation lits = RelocatableReadOnlyData
519 | otherwise = ReadOnlyData
520 needsRelocation (CmmLabel _) = True
521 needsRelocation (CmmLabelOff _ _) = True
522 needsRelocation _ = False
524 mkRODataLits :: CLabel -> [CmmLit] -> GenCmmTop CmmStatic info stmt
525 mkRODataLits lbl lits
526 = CmmData section (CmmDataLabel lbl : map CmmStaticLit lits)
527 where section | any needsRelocation lits = RelocatableReadOnlyData
528 | otherwise = ReadOnlyData
529 needsRelocation (CmmLabel _) = True
530 needsRelocation (CmmLabelOff _ _) = True
531 needsRelocation _ = False
533 mkStringCLit :: String -> FCode CmmLit
534 -- Make a global definition for the string,
535 -- and return its label
536 mkStringCLit str = mkByteStringCLit (map (fromIntegral . ord) str)
538 mkByteStringCLit :: [Word8] -> FCode CmmLit
539 mkByteStringCLit bytes
540 = do { uniq <- newUnique
541 ; let lbl = mkStringLitLabel uniq
542 ; emitData ReadOnlyData [CmmDataLabel lbl, CmmString bytes]
543 ; return (CmmLabel lbl) }
545 -------------------------------------------------------------------------
547 -- Assigning expressions to temporaries
549 -------------------------------------------------------------------------
551 assignTemp :: CmmExpr -> FCode LocalReg
552 -- Make sure the argument is in a local register
553 assignTemp (CmmReg (CmmLocal reg)) = return reg
554 assignTemp e = do { uniq <- newUnique
555 ; let reg = LocalReg uniq (cmmExprType e)
556 ; emit (mkAssign (CmmLocal reg) e)
559 newTemp :: CmmType -> FCode LocalReg
560 newTemp rep = do { uniq <- newUnique
561 ; return (LocalReg uniq rep) }
563 newUnboxedTupleRegs :: Type -> FCode ([LocalReg], [ForeignHint])
564 -- Choose suitable local regs to use for the components
565 -- of an unboxed tuple that we are about to return to
566 -- the Sequel. If the Sequel is a join point, using the
567 -- regs it wants will save later assignments.
568 newUnboxedTupleRegs res_ty
569 = ASSERT( isUnboxedTupleType res_ty )
570 do { sequel <- getSequel
571 ; regs <- choose_regs sequel
572 ; ASSERT( regs `equalLength` reps )
573 return (regs, map primRepForeignHint reps) }
575 ty_args = tyConAppArgs (repType res_ty)
578 , let rep = typePrimRep ty
579 , not (isVoidRep rep) ]
580 choose_regs (AssignTo regs _) = return regs
581 choose_regs _other = mapM (newTemp . primRepCmmType) reps
585 -------------------------------------------------------------------------
587 -------------------------------------------------------------------------
589 mkMultiAssign :: [LocalReg] -> [CmmExpr] -> CmmAGraph
590 -- Emit code to perform the assignments in the
591 -- input simultaneously, using temporary variables when necessary.
594 type Vrtx = (Key, Stmt) -- Give each vertex a unique number,
595 -- for fast comparison
596 type Stmt = (LocalReg, CmmExpr) -- r := e
598 -- We use the strongly-connected component algorithm, in which
599 -- * the vertices are the statements
600 -- * an edge goes from s1 to s2 iff
601 -- s1 assigns to something s2 uses
602 -- that is, if s1 should *follow* s2 in the final order
604 mkMultiAssign [] [] = mkNop
605 mkMultiAssign [reg] [rhs] = mkAssign (CmmLocal reg) rhs
606 mkMultiAssign regs rhss = ASSERT( equalLength regs rhss )
607 unscramble ([1..] `zip` (regs `zip` rhss))
609 unscramble :: [Vrtx] -> CmmAGraph
611 = catAGraphs (map do_component components)
613 edges :: [ (Vrtx, Key, [Key]) ]
614 edges = [ (vertex, key1, edges_from stmt1)
615 | vertex@(key1, stmt1) <- vertices ]
617 edges_from :: Stmt -> [Key]
618 edges_from stmt1 = [ key2 | (key2, stmt2) <- vertices,
619 stmt1 `mustFollow` stmt2 ]
621 components :: [SCC Vrtx]
622 components = stronglyConnCompFromEdgedVertices edges
624 -- do_components deal with one strongly-connected component
625 -- Not cyclic, or singleton? Just do it
626 do_component :: SCC Vrtx -> CmmAGraph
627 do_component (AcyclicSCC (_,stmt)) = mk_graph stmt
628 do_component (CyclicSCC []) = panic "do_component"
629 do_component (CyclicSCC [(_,stmt)]) = mk_graph stmt
631 -- Cyclic? Then go via temporaries. Pick one to
632 -- break the loop and try again with the rest.
633 do_component (CyclicSCC ((_,first_stmt) : rest))
635 let (to_tmp, from_tmp) = split u first_stmt
638 <*> mk_graph from_tmp
640 split :: Unique -> Stmt -> (Stmt, Stmt)
641 split uniq (reg, rhs)
642 = ((tmp, rhs), (reg, CmmReg (CmmLocal tmp)))
644 rep = cmmExprType rhs
645 tmp = LocalReg uniq rep
647 mk_graph :: Stmt -> CmmAGraph
648 mk_graph (reg, rhs) = mkAssign (CmmLocal reg) rhs
650 mustFollow :: Stmt -> Stmt -> Bool
651 (reg, _) `mustFollow` (_, rhs) = reg `regUsedIn` rhs
653 regUsedIn :: LocalReg -> CmmExpr -> Bool
654 reg `regUsedIn` CmmLoad e _ = reg `regUsedIn` e
655 reg `regUsedIn` CmmReg (CmmLocal reg') = reg == reg'
656 reg `regUsedIn` CmmRegOff (CmmLocal reg') _ = reg == reg'
657 reg `regUsedIn` CmmMachOp _ es = any (reg `regUsedIn`) es
658 _reg `regUsedIn` _other = False -- The CmmGlobal cases
660 -------------------------------------------------------------------------
662 -------------------------------------------------------------------------
665 emitSwitch :: CmmExpr -- Tag to switch on
666 -> [(ConTagZ, CmmAGraph)] -- Tagged branches
667 -> Maybe CmmAGraph -- Default branch (if any)
668 -> ConTagZ -> ConTagZ -- Min and Max possible values; behaviour
669 -- outside this range is undefined
671 emitSwitch tag_expr branches mb_deflt lo_tag hi_tag
672 = do { dflags <- getDynFlags
673 ; emit (mkCmmSwitch (via_C dflags) tag_expr branches mb_deflt lo_tag hi_tag) }
675 via_C dflags | HscC <- hscTarget dflags = True
679 mkCmmSwitch :: Bool -- True <=> never generate a conditional tree
680 -> CmmExpr -- Tag to switch on
681 -> [(ConTagZ, CmmAGraph)] -- Tagged branches
682 -> Maybe CmmAGraph -- Default branch (if any)
683 -> ConTagZ -> ConTagZ -- Min and Max possible values; behaviour
684 -- outside this range is undefined
687 -- First, two rather common cases in which there is no work to do
688 mkCmmSwitch _ _ [] (Just code) _ _ = code
689 mkCmmSwitch _ _ [(_,code)] Nothing _ _ = code
692 mkCmmSwitch via_C tag_expr branches mb_deflt lo_tag hi_tag
693 = withFreshLabel "switch join" $ \ join_lbl ->
694 label_default join_lbl mb_deflt $ \ mb_deflt ->
695 label_branches join_lbl branches $ \ branches ->
696 assignTemp' tag_expr $ \tag_expr' ->
698 mk_switch tag_expr' (sortLe le branches) mb_deflt
700 -- Sort the branches before calling mk_switch
704 (t1,_) `le` (t2,_) = t1 <= t2
706 mk_switch :: CmmExpr -> [(ConTagZ, BlockId)]
708 -> ConTagZ -> ConTagZ -> Bool
711 -- SINGLETON TAG RANGE: no case analysis to do
712 mk_switch _tag_expr [(tag, lbl)] _ lo_tag hi_tag _via_C
714 = ASSERT( tag == lo_tag )
717 -- SINGLETON BRANCH, NO DEFAULT: no case analysis to do
718 mk_switch _tag_expr [(_tag,lbl)] Nothing _ _ _
720 -- The simplifier might have eliminated a case
721 -- so we may have e.g. case xs of
723 -- In that situation we can be sure the (:) case
724 -- can't happen, so no need to test
726 -- SINGLETON BRANCH: one equality check to do
727 mk_switch tag_expr [(tag,lbl)] (Just deflt) _ _ _
728 = mkCbranch cond deflt lbl
730 cond = cmmNeWord tag_expr (CmmLit (mkIntCLit tag))
731 -- We have lo_tag < hi_tag, but there's only one branch,
732 -- so there must be a default
734 -- ToDo: we might want to check for the two branch case, where one of
735 -- the branches is the tag 0, because comparing '== 0' is likely to be
736 -- more efficient than other kinds of comparison.
738 -- DENSE TAG RANGE: use a switch statment.
740 -- We also use a switch uncoditionally when compiling via C, because
741 -- this will get emitted as a C switch statement and the C compiler
742 -- should do a good job of optimising it. Also, older GCC versions
743 -- (2.95 in particular) have problems compiling the complicated
744 -- if-trees generated by this code, so compiling to a switch every
745 -- time works around that problem.
747 mk_switch tag_expr branches mb_deflt lo_tag hi_tag via_C
748 | use_switch -- Use a switch
750 find_branch :: ConTagZ -> Maybe BlockId
751 find_branch i = case (assocMaybe branches i) of
755 -- NB. we have eliminated impossible branches at
756 -- either end of the range (see below), so the first
757 -- tag of a real branch is real_lo_tag (not lo_tag).
758 arms :: [Maybe BlockId]
759 arms = [ find_branch i | i <- [real_lo_tag..real_hi_tag]]
761 mkSwitch (cmmOffset tag_expr (- real_lo_tag)) arms
763 -- if we can knock off a bunch of default cases with one if, then do so
764 | Just deflt <- mb_deflt, (lowest_branch - lo_tag) >= n_branches
766 (cmmULtWord tag_expr (CmmLit (mkIntCLit lowest_branch)))
768 (mk_switch tag_expr branches mb_deflt
769 lowest_branch hi_tag via_C)
771 | Just deflt <- mb_deflt, (hi_tag - highest_branch) >= n_branches
773 (cmmUGtWord tag_expr (CmmLit (mkIntCLit highest_branch)))
775 (mk_switch tag_expr branches mb_deflt
776 lo_tag highest_branch via_C)
778 | otherwise -- Use an if-tree
780 (cmmUGeWord tag_expr (CmmLit (mkIntCLit mid_tag)))
781 (mk_switch tag_expr hi_branches mb_deflt
782 mid_tag hi_tag via_C)
783 (mk_switch tag_expr lo_branches mb_deflt
784 lo_tag (mid_tag-1) via_C)
785 -- we test (e >= mid_tag) rather than (e < mid_tag), because
786 -- the former works better when e is a comparison, and there
787 -- are two tags 0 & 1 (mid_tag == 1). In this case, the code
788 -- generator can reduce the condition to e itself without
789 -- having to reverse the sense of the comparison: comparisons
790 -- can't always be easily reversed (eg. floating
793 use_switch = {- pprTrace "mk_switch" (
794 ppr tag_expr <+> text "n_tags:" <+> int n_tags <+>
795 text "branches:" <+> ppr (map fst branches) <+>
796 text "n_branches:" <+> int n_branches <+>
797 text "lo_tag:" <+> int lo_tag <+>
798 text "hi_tag:" <+> int hi_tag <+>
799 text "real_lo_tag:" <+> int real_lo_tag <+>
800 text "real_hi_tag:" <+> int real_hi_tag) $ -}
801 ASSERT( n_branches > 1 && n_tags > 1 )
802 n_tags > 2 && (via_C || (dense && big_enough))
803 -- up to 4 branches we use a decision tree, otherwise
804 -- a switch (== jump table in the NCG). This seems to be
805 -- optimal, and corresponds with what gcc does.
806 big_enough = n_branches > 4
807 dense = n_branches > (n_tags `div` 2)
808 n_branches = length branches
810 -- ignore default slots at each end of the range if there's
811 -- no default branch defined.
812 lowest_branch = fst (head branches)
813 highest_branch = fst (last branches)
816 | isNothing mb_deflt = lowest_branch
820 | isNothing mb_deflt = highest_branch
823 n_tags = real_hi_tag - real_lo_tag + 1
825 -- INVARIANT: Provided hi_tag > lo_tag (which is true)
826 -- lo_tag <= mid_tag < hi_tag
827 -- lo_branches have tags < mid_tag
828 -- hi_branches have tags >= mid_tag
830 (mid_tag,_) = branches !! (n_branches `div` 2)
831 -- 2 branches => n_branches `div` 2 = 1
832 -- => branches !! 1 give the *second* tag
833 -- There are always at least 2 branches here
835 (lo_branches, hi_branches) = span is_lo branches
836 is_lo (t,_) = t < mid_tag
839 mkCmmLitSwitch :: CmmExpr -- Tag to switch on
840 -> [(Literal, CmmAGraph)] -- Tagged branches
841 -> CmmAGraph -- Default branch (always)
842 -> CmmAGraph -- Emit the code
843 -- Used for general literals, whose size might not be a word,
844 -- where there is always a default case, and where we don't know
845 -- the range of values for certain. For simplicity we always generate a tree.
847 -- ToDo: for integers we could do better here, perhaps by generalising
848 -- mk_switch and using that. --SDM 15/09/2004
849 mkCmmLitSwitch _scrut [] deflt = deflt
850 mkCmmLitSwitch scrut branches deflt
851 = assignTemp' scrut $ \ scrut' ->
852 withFreshLabel "switch join" $ \ join_lbl ->
853 label_code join_lbl deflt $ \ deflt ->
854 label_branches join_lbl branches $ \ branches ->
855 mk_lit_switch scrut' deflt (sortLe le branches)
858 le (t1,_) (t2,_) = t1 <= t2
860 mk_lit_switch :: CmmExpr -> BlockId
861 -> [(Literal,BlockId)]
863 mk_lit_switch scrut deflt [(lit,blk)]
864 = mkCbranch (CmmMachOp ne [scrut, CmmLit cmm_lit]) deflt blk
866 cmm_lit = mkSimpleLit lit
867 cmm_ty = cmmLitType cmm_lit
868 rep = typeWidth cmm_ty
869 ne = if isFloatType cmm_ty then MO_F_Ne rep else MO_Ne rep
871 mk_lit_switch scrut deflt_blk_id branches
872 = mkCmmIfThenElse cond
873 (mk_lit_switch scrut deflt_blk_id lo_branches)
874 (mk_lit_switch scrut deflt_blk_id hi_branches)
876 n_branches = length branches
877 (mid_lit,_) = branches !! (n_branches `div` 2)
878 -- See notes above re mid_tag
880 (lo_branches, hi_branches) = span is_lo branches
881 is_lo (t,_) = t < mid_lit
883 cond = CmmMachOp (mkLtOp mid_lit)
884 [scrut, CmmLit (mkSimpleLit mid_lit)]
888 label_default :: BlockId -> Maybe CmmAGraph
889 -> (Maybe BlockId -> CmmAGraph)
891 label_default _ Nothing thing_inside
892 = thing_inside Nothing
893 label_default join_lbl (Just code) thing_inside
894 = label_code join_lbl code $ \ lbl ->
895 thing_inside (Just lbl)
898 label_branches :: BlockId -> [(a,CmmAGraph)]
899 -> ([(a,BlockId)] -> CmmAGraph)
901 label_branches _join_lbl [] thing_inside
903 label_branches join_lbl ((tag,code):branches) thing_inside
904 = label_code join_lbl code $ \ lbl ->
905 label_branches join_lbl branches $ \ branches' ->
906 thing_inside ((tag,lbl):branches')
909 label_code :: BlockId -> CmmAGraph -> (BlockId -> CmmAGraph) -> CmmAGraph
910 -- (label_code J code fun)
912 -- [L: code; goto J] fun L
913 label_code join_lbl code thing_inside
914 = withFreshLabel "switch" $ \lbl ->
915 outOfLine (mkLabel lbl <*> code <*> mkBranch join_lbl)
920 assignTemp' :: CmmExpr -> (CmmExpr -> CmmAGraph) -> CmmAGraph
921 assignTemp' e thing_inside
922 | isTrivialCmmExpr e = thing_inside e
923 | otherwise = withTemp (cmmExprType e) $ \ lreg ->
924 let reg = CmmLocal lreg in
925 mkAssign reg e <*> thing_inside (CmmReg reg)
927 withTemp :: CmmType -> (LocalReg -> CmmAGraph) -> CmmAGraph
928 withTemp rep thing_inside
929 = withUnique $ \uniq -> thing_inside (LocalReg uniq rep)
932 -------------------------------------------------------------------------
934 -- Static Reference Tables
936 -------------------------------------------------------------------------
938 -- There is just one SRT for each top level binding; all the nested
939 -- bindings use sub-sections of this SRT. The label is passed down to
940 -- the nested bindings via the monad.
942 getSRTInfo :: SRT -> FCode C_SRT
943 getSRTInfo (SRTEntries {}) = panic "getSRTInfo"
945 getSRTInfo (SRT off len bmp)
946 | len > hALF_WORD_SIZE_IN_BITS || bmp == [fromIntegral srt_escape]
947 = do { id <- newUnique
948 -- ; top_srt <- getSRTLabel
949 ; let srt_desc_lbl = mkLargeSRTLabel id
950 -- JD: We're not constructing and emitting SRTs in the back end,
951 -- which renders this code wrong (it now names a now-non-existent label).
952 -- ; emitRODataLits srt_desc_lbl
953 -- ( cmmLabelOffW top_srt off
954 -- : mkWordCLit (fromIntegral len)
955 -- : map mkWordCLit bmp)
956 ; return (C_SRT srt_desc_lbl 0 srt_escape) }
959 = do { top_srt <- getSRTLabel
960 ; return (C_SRT top_srt off (fromIntegral (head bmp))) }
961 -- The fromIntegral converts to StgHalfWord
964 = -- TODO: Should we panic in this case?
965 -- Someone obviously thinks there should be an SRT
969 srt_escape :: StgHalfWord