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"
57 import PprCmm ( {- instances -} )
65 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) = CmmLabel (mkForeignLabel fs ms is_dyn fod)
103 is_dyn = False -- ToDo: fix me
104 mkSimpleLit other = pprPanic "mkSimpleLit" (ppr other)
106 mkLtOp :: Literal -> MachOp
107 -- On signed literals we must do a signed comparison
108 mkLtOp (MachInt _) = MO_S_Lt wordWidth
109 mkLtOp (MachFloat _) = MO_F_Lt W32
110 mkLtOp (MachDouble _) = MO_F_Lt W64
111 mkLtOp lit = MO_U_Lt (typeWidth (cmmLitType (mkSimpleLit lit)))
112 -- ToDo: seems terribly indirect!
115 ---------------------------------------------------
117 -- Cmm data type functions
119 ---------------------------------------------------
121 -- The "B" variants take byte offsets
122 cmmRegOffB :: CmmReg -> ByteOff -> CmmExpr
123 cmmRegOffB = cmmRegOff
125 cmmOffsetB :: CmmExpr -> ByteOff -> CmmExpr
126 cmmOffsetB = cmmOffset
128 cmmOffsetExprB :: CmmExpr -> CmmExpr -> CmmExpr
129 cmmOffsetExprB = cmmOffsetExpr
131 cmmLabelOffB :: CLabel -> ByteOff -> CmmLit
132 cmmLabelOffB = cmmLabelOff
134 cmmOffsetLitB :: CmmLit -> ByteOff -> CmmLit
135 cmmOffsetLitB = cmmOffsetLit
137 -----------------------
138 -- The "W" variants take word offsets
139 cmmOffsetExprW :: CmmExpr -> CmmExpr -> CmmExpr
140 -- The second arg is a *word* offset; need to change it to bytes
141 cmmOffsetExprW e (CmmLit (CmmInt n _)) = cmmOffsetW e (fromInteger n)
142 cmmOffsetExprW e wd_off = cmmIndexExpr wordWidth e wd_off
144 cmmOffsetW :: CmmExpr -> WordOff -> CmmExpr
145 cmmOffsetW e n = cmmOffsetB e (wORD_SIZE * n)
147 cmmRegOffW :: CmmReg -> WordOff -> CmmExpr
148 cmmRegOffW reg wd_off = cmmRegOffB reg (wd_off * wORD_SIZE)
150 cmmOffsetLitW :: CmmLit -> WordOff -> CmmLit
151 cmmOffsetLitW lit wd_off = cmmOffsetLitB lit (wORD_SIZE * wd_off)
153 cmmLabelOffW :: CLabel -> WordOff -> CmmLit
154 cmmLabelOffW lbl wd_off = cmmLabelOffB lbl (wORD_SIZE * wd_off)
156 cmmLoadIndexW :: CmmExpr -> Int -> CmmType -> CmmExpr
157 cmmLoadIndexW base off ty = CmmLoad (cmmOffsetW base off) ty
159 -----------------------
160 cmmULtWord, cmmUGeWord, cmmUGtWord, cmmSubWord,
161 cmmNeWord, cmmEqWord, cmmOrWord, cmmAndWord
162 :: CmmExpr -> CmmExpr -> CmmExpr
163 cmmOrWord e1 e2 = CmmMachOp mo_wordOr [e1, e2]
164 cmmAndWord e1 e2 = CmmMachOp mo_wordAnd [e1, e2]
165 cmmNeWord e1 e2 = CmmMachOp mo_wordNe [e1, e2]
166 cmmEqWord e1 e2 = CmmMachOp mo_wordEq [e1, e2]
167 cmmULtWord e1 e2 = CmmMachOp mo_wordULt [e1, e2]
168 cmmUGeWord e1 e2 = CmmMachOp mo_wordUGe [e1, e2]
169 cmmUGtWord e1 e2 = CmmMachOp mo_wordUGt [e1, e2]
170 --cmmShlWord e1 e2 = CmmMachOp mo_wordShl [e1, e2]
171 --cmmUShrWord e1 e2 = CmmMachOp mo_wordUShr [e1, e2]
172 cmmSubWord e1 e2 = CmmMachOp mo_wordSub [e1, e2]
174 cmmNegate :: CmmExpr -> CmmExpr
175 cmmNegate (CmmLit (CmmInt n rep)) = CmmLit (CmmInt (-n) rep)
176 cmmNegate e = CmmMachOp (MO_S_Neg (cmmExprWidth e)) [e]
178 blankWord :: CmmStatic
179 blankWord = CmmUninitialised wORD_SIZE
183 --cmmTagBits = CmmLit (mkIntCLit tAG_BITS)
184 cmmTagMask, cmmPointerMask :: CmmExpr
185 cmmTagMask = CmmLit (mkIntCLit tAG_MASK)
186 cmmPointerMask = CmmLit (mkIntCLit (complement tAG_MASK))
188 -- Used to untag a possibly tagged pointer
189 -- A static label need not be untagged
190 cmmUntag, cmmGetTag :: CmmExpr -> CmmExpr
191 cmmUntag e@(CmmLit (CmmLabel _)) = e
193 cmmUntag e = (e `cmmAndWord` cmmPointerMask)
195 cmmGetTag e = (e `cmmAndWord` cmmTagMask)
197 -- Test if a closure pointer is untagged
198 cmmIsTagged :: CmmExpr -> CmmExpr
199 cmmIsTagged e = (e `cmmAndWord` cmmTagMask)
200 `cmmNeWord` CmmLit zeroCLit
202 cmmConstrTag, cmmConstrTag1 :: CmmExpr -> CmmExpr
203 cmmConstrTag e = (e `cmmAndWord` cmmTagMask) `cmmSubWord` (CmmLit (mkIntCLit 1))
204 -- Get constructor tag, but one based.
205 cmmConstrTag1 e = e `cmmAndWord` cmmTagMask
207 -----------------------
210 mkWordCLit :: StgWord -> CmmLit
211 mkWordCLit wd = CmmInt (fromIntegral wd) wordWidth
213 packHalfWordsCLit :: (Integral a, Integral b) => a -> b -> CmmLit
214 -- Make a single word literal in which the lower_half_word is
215 -- at the lower address, and the upper_half_word is at the
217 -- ToDo: consider using half-word lits instead
218 -- but be careful: that's vulnerable when reversed
219 packHalfWordsCLit lower_half_word upper_half_word
220 #ifdef WORDS_BIGENDIAN
221 = mkWordCLit ((fromIntegral lower_half_word `shiftL` hALF_WORD_SIZE_IN_BITS)
222 .|. fromIntegral upper_half_word)
224 = mkWordCLit ((fromIntegral lower_half_word)
225 .|. (fromIntegral upper_half_word `shiftL` hALF_WORD_SIZE_IN_BITS))
228 --------------------------------------------------------------------------
230 -- Incrementing a memory location
232 --------------------------------------------------------------------------
234 addToMemLbl :: CmmType -> CLabel -> Int -> CmmAGraph
235 addToMemLbl rep lbl n = addToMem rep (CmmLit (CmmLabel lbl)) n
237 addToMem :: CmmType -- rep of the counter
238 -> CmmExpr -- Address
239 -> Int -- What to add (a word)
241 addToMem rep ptr n = addToMemE rep ptr (CmmLit (CmmInt (toInteger n) (typeWidth rep)))
243 addToMemE :: CmmType -- rep of the counter
244 -> CmmExpr -- Address
245 -> CmmExpr -- What to add (a word-typed expression)
248 = mkStore ptr (CmmMachOp (MO_Add (typeWidth rep)) [CmmLoad ptr rep, n])
251 -------------------------------------------------------------------------
253 -- Loading a field from an object,
254 -- where the object pointer is itself tagged
256 -------------------------------------------------------------------------
258 mkTaggedObjectLoad :: LocalReg -> LocalReg -> WordOff -> DynTag -> CmmAGraph
259 -- (loadTaggedObjectField reg base off tag) generates assignment
260 -- reg = bitsK[ base + off - tag ]
261 -- where K is fixed by 'reg'
262 mkTaggedObjectLoad reg base offset tag
263 = mkAssign (CmmLocal reg)
264 (CmmLoad (cmmOffsetB (CmmReg (CmmLocal base))
265 (wORD_SIZE*offset - tag))
268 -------------------------------------------------------------------------
270 -- Converting a closure tag to a closure for enumeration types
271 -- (this is the implementation of tagToEnum#).
273 -------------------------------------------------------------------------
275 tagToClosure :: TyCon -> CmmExpr -> CmmExpr
276 tagToClosure tycon tag
277 = CmmLoad (cmmOffsetExprW closure_tbl tag) bWord
278 where closure_tbl = CmmLit (CmmLabel lbl)
279 lbl = mkClosureTableLabel (tyConName tycon) NoCafRefs
281 -------------------------------------------------------------------------
283 -- Conditionals and rts calls
285 -------------------------------------------------------------------------
287 emitRtsCall :: LitString -> [(CmmExpr,ForeignHint)] -> Bool -> FCode ()
288 emitRtsCall fun args safe = emitRtsCall' [] fun args Nothing safe
289 -- The 'Nothing' says "save all global registers"
291 emitRtsCallWithVols :: LitString -> [(CmmExpr,ForeignHint)] -> [GlobalReg] -> Bool -> FCode ()
292 emitRtsCallWithVols fun args vols safe
293 = emitRtsCall' [] fun args (Just vols) safe
295 emitRtsCallWithResult :: LocalReg -> ForeignHint -> LitString
296 -> [(CmmExpr,ForeignHint)] -> Bool -> FCode ()
297 emitRtsCallWithResult res hint fun args safe
298 = emitRtsCall' [(res,hint)] fun args Nothing safe
300 -- Make a call to an RTS C procedure
302 :: [(LocalReg,ForeignHint)]
304 -> [(CmmExpr,ForeignHint)]
306 -> Bool -- True <=> CmmSafe call
308 emitRtsCall' res fun args _vols safe
309 = --error "emitRtsCall'"
310 do { updfr_off <- getUpdFrameOff
312 ; emit $ call updfr_off
317 mkCall fun_expr Native res' args' updfr_off
319 mkUnsafeCall (ForeignTarget fun_expr
320 (ForeignConvention CCallConv arg_hints res_hints)) res' args'
321 (args', arg_hints) = unzip args
322 (res', res_hints) = unzip res
323 (caller_save, caller_load) = callerSaveVolatileRegs
324 fun_expr = mkLblExpr (mkRtsCodeLabel fun)
327 -----------------------------------------------------------------------------
329 -- Caller-Save Registers
331 -----------------------------------------------------------------------------
333 -- Here we generate the sequence of saves/restores required around a
334 -- foreign call instruction.
336 -- TODO: reconcile with includes/Regs.h
337 -- * Regs.h claims that BaseReg should be saved last and loaded first
338 -- * This might not have been tickled before since BaseReg is callee save
339 -- * Regs.h saves SparkHd, ParkT1, SparkBase and SparkLim
340 callerSaveVolatileRegs :: (CmmAGraph, CmmAGraph)
341 callerSaveVolatileRegs = (caller_save, caller_load)
343 caller_save = catAGraphs (map callerSaveGlobalReg regs_to_save)
344 caller_load = catAGraphs (map callerRestoreGlobalReg regs_to_save)
346 system_regs = [ Sp,SpLim,Hp,HpLim,CurrentTSO,CurrentNursery
347 {- ,SparkHd,SparkTl,SparkBase,SparkLim -}
350 regs_to_save = filter callerSaves system_regs
352 callerSaveGlobalReg reg
353 = mkStore (get_GlobalReg_addr reg) (CmmReg (CmmGlobal reg))
355 callerRestoreGlobalReg reg
356 = mkAssign (CmmGlobal reg)
357 (CmmLoad (get_GlobalReg_addr reg) (globalRegType reg))
359 -- -----------------------------------------------------------------------------
362 -- We map STG registers onto appropriate CmmExprs. Either they map
363 -- to real machine registers or stored as offsets from BaseReg. Given
364 -- a GlobalReg, get_GlobalReg_addr always produces the
365 -- register table address for it.
366 -- (See also get_GlobalReg_reg_or_addr in MachRegs)
368 get_GlobalReg_addr :: GlobalReg -> CmmExpr
369 get_GlobalReg_addr BaseReg = regTableOffset 0
370 get_GlobalReg_addr mid = get_Regtable_addr_from_offset
371 (globalRegType mid) (baseRegOffset mid)
373 -- Calculate a literal representing an offset into the register table.
374 -- Used when we don't have an actual BaseReg to offset from.
375 regTableOffset :: Int -> CmmExpr
377 CmmLit (CmmLabelOff mkMainCapabilityLabel (oFFSET_Capability_r + n))
379 get_Regtable_addr_from_offset :: CmmType -> Int -> CmmExpr
380 get_Regtable_addr_from_offset _rep offset =
382 CmmRegOff (CmmGlobal BaseReg) offset
384 regTableOffset offset
388 -- | Returns 'True' if this global register is stored in a caller-saves
391 callerSaves :: GlobalReg -> Bool
393 #ifdef CALLER_SAVES_Base
394 callerSaves BaseReg = True
396 #ifdef CALLER_SAVES_Sp
397 callerSaves Sp = True
399 #ifdef CALLER_SAVES_SpLim
400 callerSaves SpLim = True
402 #ifdef CALLER_SAVES_Hp
403 callerSaves Hp = True
405 #ifdef CALLER_SAVES_HpLim
406 callerSaves HpLim = True
408 #ifdef CALLER_SAVES_CurrentTSO
409 callerSaves CurrentTSO = True
411 #ifdef CALLER_SAVES_CurrentNursery
412 callerSaves CurrentNursery = True
414 callerSaves _ = False
417 -- -----------------------------------------------------------------------------
418 -- Information about global registers
420 baseRegOffset :: GlobalReg -> Int
422 baseRegOffset Sp = oFFSET_StgRegTable_rSp
423 baseRegOffset SpLim = oFFSET_StgRegTable_rSpLim
424 baseRegOffset (LongReg 1) = oFFSET_StgRegTable_rL1
425 baseRegOffset Hp = oFFSET_StgRegTable_rHp
426 baseRegOffset HpLim = oFFSET_StgRegTable_rHpLim
427 baseRegOffset CurrentTSO = oFFSET_StgRegTable_rCurrentTSO
428 baseRegOffset CurrentNursery = oFFSET_StgRegTable_rCurrentNursery
429 baseRegOffset HpAlloc = oFFSET_StgRegTable_rHpAlloc
430 baseRegOffset GCEnter1 = oFFSET_stgGCEnter1
431 baseRegOffset GCFun = oFFSET_stgGCFun
432 baseRegOffset reg = pprPanic "baseRegOffset:" (ppr reg)
434 -------------------------------------------------------------------------
436 -- Strings generate a top-level data block
438 -------------------------------------------------------------------------
440 emitDataLits :: CLabel -> [CmmLit] -> FCode ()
441 -- Emit a data-segment data block
442 emitDataLits lbl lits
443 = emitData Data (CmmDataLabel lbl : map CmmStaticLit lits)
445 mkDataLits :: CLabel -> [CmmLit] -> GenCmmTop CmmStatic info stmt
446 -- Emit a data-segment data block
448 = CmmData Data (CmmDataLabel lbl : map CmmStaticLit lits)
450 emitRODataLits :: CLabel -> [CmmLit] -> FCode ()
451 -- Emit a read-only data block
452 emitRODataLits lbl lits
453 = emitData section (CmmDataLabel lbl : map CmmStaticLit lits)
454 where section | any needsRelocation lits = RelocatableReadOnlyData
455 | otherwise = ReadOnlyData
456 needsRelocation (CmmLabel _) = True
457 needsRelocation (CmmLabelOff _ _) = True
458 needsRelocation _ = False
460 mkRODataLits :: CLabel -> [CmmLit] -> GenCmmTop CmmStatic info stmt
461 mkRODataLits lbl lits
462 = CmmData section (CmmDataLabel lbl : map CmmStaticLit lits)
463 where section | any needsRelocation lits = RelocatableReadOnlyData
464 | otherwise = ReadOnlyData
465 needsRelocation (CmmLabel _) = True
466 needsRelocation (CmmLabelOff _ _) = True
467 needsRelocation _ = False
469 mkStringCLit :: String -> FCode CmmLit
470 -- Make a global definition for the string,
471 -- and return its label
472 mkStringCLit str = mkByteStringCLit (map (fromIntegral . ord) str)
474 mkByteStringCLit :: [Word8] -> FCode CmmLit
475 mkByteStringCLit bytes
476 = do { uniq <- newUnique
477 ; let lbl = mkStringLitLabel uniq
478 ; emitData ReadOnlyData [CmmDataLabel lbl, CmmString bytes]
479 ; return (CmmLabel lbl) }
481 -------------------------------------------------------------------------
483 -- Assigning expressions to temporaries
485 -------------------------------------------------------------------------
487 assignTemp :: CmmExpr -> FCode LocalReg
488 -- Make sure the argument is in a local register
489 assignTemp (CmmReg (CmmLocal reg)) = return reg
490 assignTemp e = do { uniq <- newUnique
491 ; let reg = LocalReg uniq (cmmExprType e)
492 ; emit (mkAssign (CmmLocal reg) e)
495 newTemp :: CmmType -> FCode LocalReg
496 newTemp rep = do { uniq <- newUnique
497 ; return (LocalReg uniq rep) }
499 newUnboxedTupleRegs :: Type -> FCode ([LocalReg], [ForeignHint])
500 -- Choose suitable local regs to use for the components
501 -- of an unboxed tuple that we are about to return to
502 -- the Sequel. If the Sequel is a joint point, using the
503 -- regs it wants will save later assignments.
504 newUnboxedTupleRegs res_ty
505 = ASSERT( isUnboxedTupleType res_ty )
506 do { sequel <- getSequel
507 ; regs <- choose_regs sequel
508 ; ASSERT( regs `equalLength` reps )
509 return (regs, map primRepForeignHint reps) }
511 ty_args = tyConAppArgs (repType res_ty)
514 , let rep = typePrimRep ty
515 , not (isVoidRep rep) ]
516 choose_regs (AssignTo regs _) = return regs
517 choose_regs _other = mapM (newTemp . primRepCmmType) reps
521 -------------------------------------------------------------------------
523 -------------------------------------------------------------------------
525 mkMultiAssign :: [LocalReg] -> [CmmExpr] -> CmmAGraph
526 -- Emit code to perform the assignments in the
527 -- input simultaneously, using temporary variables when necessary.
530 type Vrtx = (Key, Stmt) -- Give each vertex a unique number,
531 -- for fast comparison
532 type Stmt = (LocalReg, CmmExpr) -- r := e
534 -- We use the strongly-connected component algorithm, in which
535 -- * the vertices are the statements
536 -- * an edge goes from s1 to s2 iff
537 -- s1 assigns to something s2 uses
538 -- that is, if s1 should *follow* s2 in the final order
540 mkMultiAssign [] [] = mkNop
541 mkMultiAssign [reg] [rhs] = mkAssign (CmmLocal reg) rhs
542 mkMultiAssign regs rhss = ASSERT( equalLength regs rhss )
543 unscramble ([1..] `zip` (regs `zip` rhss))
545 unscramble :: [Vrtx] -> CmmAGraph
547 = catAGraphs (map do_component components)
549 edges :: [ (Vrtx, Key, [Key]) ]
550 edges = [ (vertex, key1, edges_from stmt1)
551 | vertex@(key1, stmt1) <- vertices ]
553 edges_from :: Stmt -> [Key]
554 edges_from stmt1 = [ key2 | (key2, stmt2) <- vertices,
555 stmt1 `mustFollow` stmt2 ]
557 components :: [SCC Vrtx]
558 components = stronglyConnCompFromEdgedVertices edges
560 -- do_components deal with one strongly-connected component
561 -- Not cyclic, or singleton? Just do it
562 do_component :: SCC Vrtx -> CmmAGraph
563 do_component (AcyclicSCC (_,stmt)) = mk_graph stmt
564 do_component (CyclicSCC []) = panic "do_component"
565 do_component (CyclicSCC [(_,stmt)]) = mk_graph stmt
567 -- Cyclic? Then go via temporaries. Pick one to
568 -- break the loop and try again with the rest.
569 do_component (CyclicSCC ((_,first_stmt) : rest))
571 let (to_tmp, from_tmp) = split u first_stmt
574 <*> mk_graph from_tmp
576 split :: Unique -> Stmt -> (Stmt, Stmt)
577 split uniq (reg, rhs)
578 = ((tmp, rhs), (reg, CmmReg (CmmLocal tmp)))
580 rep = cmmExprType rhs
581 tmp = LocalReg uniq rep
583 mk_graph :: Stmt -> CmmAGraph
584 mk_graph (reg, rhs) = mkAssign (CmmLocal reg) rhs
586 mustFollow :: Stmt -> Stmt -> Bool
587 (reg, _) `mustFollow` (_, rhs) = reg `regUsedIn` rhs
589 regUsedIn :: LocalReg -> CmmExpr -> Bool
590 reg `regUsedIn` CmmLoad e _ = reg `regUsedIn` e
591 reg `regUsedIn` CmmReg (CmmLocal reg') = reg == reg'
592 reg `regUsedIn` CmmRegOff (CmmLocal reg') _ = reg == reg'
593 reg `regUsedIn` CmmMachOp _ es = any (reg `regUsedIn`) es
594 _reg `regUsedIn` _other = False -- The CmmGlobal cases
597 -------------------------------------------------------------------------
599 -------------------------------------------------------------------------
602 emitSwitch :: CmmExpr -- Tag to switch on
603 -> [(ConTagZ, CmmAGraph)] -- Tagged branches
604 -> Maybe CmmAGraph -- Default branch (if any)
605 -> ConTagZ -> ConTagZ -- Min and Max possible values; behaviour
606 -- outside this range is undefined
608 emitSwitch tag_expr branches mb_deflt lo_tag hi_tag
609 = do { dflags <- getDynFlags
610 ; emit (mkCmmSwitch (via_C dflags) tag_expr branches mb_deflt lo_tag hi_tag) }
612 via_C dflags | HscC <- hscTarget dflags = True
616 mkCmmSwitch :: Bool -- True <=> never generate a conditional tree
617 -> CmmExpr -- Tag to switch on
618 -> [(ConTagZ, CmmAGraph)] -- Tagged branches
619 -> Maybe CmmAGraph -- Default branch (if any)
620 -> ConTagZ -> ConTagZ -- Min and Max possible values; behaviour
621 -- outside this range is undefined
624 -- First, two rather common cases in which there is no work to do
625 mkCmmSwitch _ _ [] (Just code) _ _ = code
626 mkCmmSwitch _ _ [(_,code)] Nothing _ _ = code
629 mkCmmSwitch via_C tag_expr branches mb_deflt lo_tag hi_tag
630 = withFreshLabel "switch join" $ \ join_lbl ->
631 label_default join_lbl mb_deflt $ \ mb_deflt ->
632 label_branches join_lbl branches $ \ branches ->
633 assignTemp' tag_expr $ \tag_expr' ->
635 mk_switch tag_expr' (sortLe le branches) mb_deflt
637 -- Sort the branches before calling mk_switch
641 (t1,_) `le` (t2,_) = t1 <= t2
643 mk_switch :: CmmExpr -> [(ConTagZ, BlockId)]
645 -> ConTagZ -> ConTagZ -> Bool
648 -- SINGLETON TAG RANGE: no case analysis to do
649 mk_switch _tag_expr [(tag, lbl)] _ lo_tag hi_tag _via_C
651 = ASSERT( tag == lo_tag )
654 -- SINGLETON BRANCH, NO DEFAULT: no case analysis to do
655 mk_switch _tag_expr [(_tag,lbl)] Nothing _ _ _
657 -- The simplifier might have eliminated a case
658 -- so we may have e.g. case xs of
660 -- In that situation we can be sure the (:) case
661 -- can't happen, so no need to test
663 -- SINGLETON BRANCH: one equality check to do
664 mk_switch tag_expr [(tag,lbl)] (Just deflt) _ _ _
665 = mkCbranch cond deflt lbl
667 cond = cmmNeWord tag_expr (CmmLit (mkIntCLit tag))
668 -- We have lo_tag < hi_tag, but there's only one branch,
669 -- so there must be a default
671 -- ToDo: we might want to check for the two branch case, where one of
672 -- the branches is the tag 0, because comparing '== 0' is likely to be
673 -- more efficient than other kinds of comparison.
675 -- DENSE TAG RANGE: use a switch statment.
677 -- We also use a switch uncoditionally when compiling via C, because
678 -- this will get emitted as a C switch statement and the C compiler
679 -- should do a good job of optimising it. Also, older GCC versions
680 -- (2.95 in particular) have problems compiling the complicated
681 -- if-trees generated by this code, so compiling to a switch every
682 -- time works around that problem.
684 mk_switch tag_expr branches mb_deflt lo_tag hi_tag via_C
685 | use_switch -- Use a switch
687 find_branch :: ConTagZ -> Maybe BlockId
688 find_branch i = case (assocMaybe branches i) of
692 -- NB. we have eliminated impossible branches at
693 -- either end of the range (see below), so the first
694 -- tag of a real branch is real_lo_tag (not lo_tag).
695 arms :: [Maybe BlockId]
696 arms = [ find_branch i | i <- [real_lo_tag..real_hi_tag]]
698 mkSwitch (cmmOffset tag_expr (- real_lo_tag)) arms
700 -- if we can knock off a bunch of default cases with one if, then do so
701 | Just deflt <- mb_deflt, (lowest_branch - lo_tag) >= n_branches
703 (cmmULtWord tag_expr (CmmLit (mkIntCLit lowest_branch)))
705 (mk_switch tag_expr branches mb_deflt
706 lowest_branch hi_tag via_C)
708 | Just deflt <- mb_deflt, (hi_tag - highest_branch) >= n_branches
710 (cmmUGtWord tag_expr (CmmLit (mkIntCLit highest_branch)))
712 (mk_switch tag_expr branches mb_deflt
713 lo_tag highest_branch via_C)
715 | otherwise -- Use an if-tree
717 (cmmUGeWord tag_expr (CmmLit (mkIntCLit mid_tag)))
718 (mk_switch tag_expr hi_branches mb_deflt
719 mid_tag hi_tag via_C)
720 (mk_switch tag_expr lo_branches mb_deflt
721 lo_tag (mid_tag-1) via_C)
722 -- we test (e >= mid_tag) rather than (e < mid_tag), because
723 -- the former works better when e is a comparison, and there
724 -- are two tags 0 & 1 (mid_tag == 1). In this case, the code
725 -- generator can reduce the condition to e itself without
726 -- having to reverse the sense of the comparison: comparisons
727 -- can't always be easily reversed (eg. floating
730 use_switch = {- pprTrace "mk_switch" (
731 ppr tag_expr <+> text "n_tags:" <+> int n_tags <+>
732 text "branches:" <+> ppr (map fst branches) <+>
733 text "n_branches:" <+> int n_branches <+>
734 text "lo_tag:" <+> int lo_tag <+>
735 text "hi_tag:" <+> int hi_tag <+>
736 text "real_lo_tag:" <+> int real_lo_tag <+>
737 text "real_hi_tag:" <+> int real_hi_tag) $ -}
738 ASSERT( n_branches > 1 && n_tags > 1 )
739 n_tags > 2 && (via_C || (dense && big_enough))
740 -- up to 4 branches we use a decision tree, otherwise
741 -- a switch (== jump table in the NCG). This seems to be
742 -- optimal, and corresponds with what gcc does.
743 big_enough = n_branches > 4
744 dense = n_branches > (n_tags `div` 2)
745 n_branches = length branches
747 -- ignore default slots at each end of the range if there's
748 -- no default branch defined.
749 lowest_branch = fst (head branches)
750 highest_branch = fst (last branches)
753 | isNothing mb_deflt = lowest_branch
757 | isNothing mb_deflt = highest_branch
760 n_tags = real_hi_tag - real_lo_tag + 1
762 -- INVARIANT: Provided hi_tag > lo_tag (which is true)
763 -- lo_tag <= mid_tag < hi_tag
764 -- lo_branches have tags < mid_tag
765 -- hi_branches have tags >= mid_tag
767 (mid_tag,_) = branches !! (n_branches `div` 2)
768 -- 2 branches => n_branches `div` 2 = 1
769 -- => branches !! 1 give the *second* tag
770 -- There are always at least 2 branches here
772 (lo_branches, hi_branches) = span is_lo branches
773 is_lo (t,_) = t < mid_tag
776 mkCmmLitSwitch :: CmmExpr -- Tag to switch on
777 -> [(Literal, CmmAGraph)] -- Tagged branches
778 -> CmmAGraph -- Default branch (always)
779 -> CmmAGraph -- Emit the code
780 -- Used for general literals, whose size might not be a word,
781 -- where there is always a default case, and where we don't know
782 -- the range of values for certain. For simplicity we always generate a tree.
784 -- ToDo: for integers we could do better here, perhaps by generalising
785 -- mk_switch and using that. --SDM 15/09/2004
786 mkCmmLitSwitch _scrut [] deflt = deflt
787 mkCmmLitSwitch scrut branches deflt
788 = assignTemp' scrut $ \ scrut' ->
789 withFreshLabel "switch join" $ \ join_lbl ->
790 label_code join_lbl deflt $ \ deflt ->
791 label_branches join_lbl branches $ \ branches ->
792 mk_lit_switch scrut' deflt (sortLe le branches)
795 le (t1,_) (t2,_) = t1 <= t2
797 mk_lit_switch :: CmmExpr -> BlockId
798 -> [(Literal,BlockId)]
800 mk_lit_switch scrut deflt [(lit,blk)]
801 = mkCbranch (CmmMachOp ne [scrut, CmmLit cmm_lit]) deflt blk
803 cmm_lit = mkSimpleLit lit
804 cmm_ty = cmmLitType cmm_lit
805 rep = typeWidth cmm_ty
806 ne = if isFloatType cmm_ty then MO_F_Ne rep else MO_Ne rep
808 mk_lit_switch scrut deflt_blk_id branches
809 = mkCmmIfThenElse cond
810 (mk_lit_switch scrut deflt_blk_id lo_branches)
811 (mk_lit_switch scrut deflt_blk_id hi_branches)
813 n_branches = length branches
814 (mid_lit,_) = branches !! (n_branches `div` 2)
815 -- See notes above re mid_tag
817 (lo_branches, hi_branches) = span is_lo branches
818 is_lo (t,_) = t < mid_lit
820 cond = CmmMachOp (mkLtOp mid_lit)
821 [scrut, CmmLit (mkSimpleLit mid_lit)]
825 label_default :: BlockId -> Maybe CmmAGraph
826 -> (Maybe BlockId -> CmmAGraph)
828 label_default _ Nothing thing_inside
829 = thing_inside Nothing
830 label_default join_lbl (Just code) thing_inside
831 = label_code join_lbl code $ \ lbl ->
832 thing_inside (Just lbl)
835 label_branches :: BlockId -> [(a,CmmAGraph)]
836 -> ([(a,BlockId)] -> CmmAGraph)
838 label_branches _join_lbl [] thing_inside
840 label_branches join_lbl ((tag,code):branches) thing_inside
841 = label_code join_lbl code $ \ lbl ->
842 label_branches join_lbl branches $ \ branches' ->
843 thing_inside ((tag,lbl):branches')
846 label_code :: BlockId -> CmmAGraph -> (BlockId -> CmmAGraph) -> CmmAGraph
847 -- (label_code J code fun)
849 -- [L: code; goto J] fun L
850 label_code join_lbl code thing_inside
851 = withFreshLabel "switch" $ \lbl ->
852 outOfLine (mkLabel lbl <*> code <*> mkBranch join_lbl)
857 assignTemp' :: CmmExpr -> (CmmExpr -> CmmAGraph) -> CmmAGraph
858 assignTemp' e thing_inside
859 | isTrivialCmmExpr e = thing_inside e
860 | otherwise = withTemp (cmmExprType e) $ \ lreg ->
861 let reg = CmmLocal lreg in
862 mkAssign reg e <*> thing_inside (CmmReg reg)
864 withTemp :: CmmType -> (LocalReg -> CmmAGraph) -> CmmAGraph
865 withTemp rep thing_inside
866 = withUnique $ \uniq -> thing_inside (LocalReg uniq rep)
869 -------------------------------------------------------------------------
871 -- Static Reference Tables
873 -------------------------------------------------------------------------
875 -- There is just one SRT for each top level binding; all the nested
876 -- bindings use sub-sections of this SRT. The label is passed down to
877 -- the nested bindings via the monad.
879 getSRTInfo :: SRT -> FCode C_SRT
880 getSRTInfo (SRTEntries {}) = panic "getSRTInfo"
882 getSRTInfo (SRT off len bmp)
883 | len > hALF_WORD_SIZE_IN_BITS || bmp == [fromIntegral srt_escape]
884 = do { id <- newUnique
885 -- ; top_srt <- getSRTLabel
886 ; let srt_desc_lbl = mkLargeSRTLabel id
887 -- JD: We're not constructing and emitting SRTs in the back end,
888 -- which renders this code wrong (it now names a now-non-existent label).
889 -- ; emitRODataLits srt_desc_lbl
890 -- ( cmmLabelOffW top_srt off
891 -- : mkWordCLit (fromIntegral len)
892 -- : map mkWordCLit bmp)
893 ; return (C_SRT srt_desc_lbl 0 srt_escape) }
896 = do { top_srt <- getSRTLabel
897 ; return (C_SRT top_srt off (fromIntegral (head bmp))) }
898 -- The fromIntegral converts to StgHalfWord
901 = -- TODO: Should we panic in this case?
902 -- Someone obviously thinks there should be an SRT
906 srt_escape :: StgHalfWord