1 -----------------------------------------------------------------------------
3 -- Code generator utilities; mostly monadic
5 -- (c) The University of Glasgow 2004
7 -----------------------------------------------------------------------------
12 emitDataLits, emitRODataLits, emitIf, emitIfThenElse,
13 emitRtsCall, emitRtsCallWithVols, emitRtsCallWithResult,
16 emitSwitch, emitLitSwitch,
19 cmmAndWord, cmmOrWord, cmmNegate, cmmEqWord, cmmNeWord,
20 cmmOffsetExprW, cmmOffsetExprB,
21 cmmRegOffW, cmmRegOffB,
22 cmmLabelOffW, cmmLabelOffB,
23 cmmOffsetW, cmmOffsetB,
24 cmmOffsetLitW, cmmOffsetLitB,
34 #include "HsVersions.h"
37 import TyCon ( TyCon, tyConName )
39 import Constants ( wORD_SIZE )
40 import SMRep ( CgRep, StgWord, hALF_WORD_SIZE_IN_BITS, ByteOff,
42 import PprCmm ( {- instances -} )
46 import MachOp ( MachRep(..), wordRep, MachOp(..), MachHint(..),
47 mo_wordOr, mo_wordAnd, mo_wordNe, mo_wordEq,
48 mo_wordULt, mo_wordUGt, mo_wordUGe, machRepByteWidth )
49 import ForeignCall ( CCallConv(..) )
50 import Literal ( Literal(..) )
51 import CLabel ( CLabel, mkStringLitLabel )
52 import Digraph ( SCC(..), stronglyConnComp )
53 import ListSetOps ( assocDefault )
54 import Util ( filterOut, sortLe )
55 import DynFlags ( DynFlags(..), HscTarget(..) )
56 import Packages ( HomeModules )
57 import FastString ( LitString, FastString, unpackFS )
62 import Maybe ( isNothing )
64 -------------------------------------------------------------------------
66 -- Random small functions
68 -------------------------------------------------------------------------
70 addIdReps :: [Id] -> [(CgRep, Id)]
71 addIdReps ids = [(idCgRep id, id) | id <- ids]
73 -------------------------------------------------------------------------
77 -------------------------------------------------------------------------
79 cgLit :: Literal -> FCode CmmLit
80 cgLit (MachStr s) = mkStringCLit (unpackFS s)
81 cgLit other_lit = return (mkSimpleLit other_lit)
83 mkSimpleLit :: Literal -> CmmLit
84 mkSimpleLit (MachChar c) = CmmInt (fromIntegral (ord c)) wordRep
85 mkSimpleLit MachNullAddr = zeroCLit
86 mkSimpleLit (MachInt i) = CmmInt i wordRep
87 mkSimpleLit (MachInt64 i) = CmmInt i I64
88 mkSimpleLit (MachWord i) = CmmInt i wordRep
89 mkSimpleLit (MachWord64 i) = CmmInt i I64
90 mkSimpleLit (MachFloat r) = CmmFloat r F32
91 mkSimpleLit (MachDouble r) = CmmFloat r F64
92 mkSimpleLit (MachLabel fs ms) = CmmLabel (mkForeignLabel fs ms is_dyn)
94 is_dyn = False -- ToDo: fix me
96 mkLtOp :: Literal -> MachOp
97 -- On signed literals we must do a signed comparison
98 mkLtOp (MachInt _) = MO_S_Lt wordRep
99 mkLtOp (MachFloat _) = MO_S_Lt F32
100 mkLtOp (MachDouble _) = MO_S_Lt F64
101 mkLtOp lit = MO_U_Lt (cmmLitRep (mkSimpleLit lit))
104 ---------------------------------------------------
106 -- Cmm data type functions
108 ---------------------------------------------------
110 -----------------------
111 -- The "B" variants take byte offsets
112 cmmRegOffB :: CmmReg -> ByteOff -> CmmExpr
113 cmmRegOffB = cmmRegOff
115 cmmOffsetB :: CmmExpr -> ByteOff -> CmmExpr
116 cmmOffsetB = cmmOffset
118 cmmOffsetExprB :: CmmExpr -> CmmExpr -> CmmExpr
119 cmmOffsetExprB = cmmOffsetExpr
121 cmmLabelOffB :: CLabel -> ByteOff -> CmmLit
122 cmmLabelOffB = cmmLabelOff
124 cmmOffsetLitB :: CmmLit -> ByteOff -> CmmLit
125 cmmOffsetLitB = cmmOffsetLit
127 -----------------------
128 -- The "W" variants take word offsets
129 cmmOffsetExprW :: CmmExpr -> CmmExpr -> CmmExpr
130 -- The second arg is a *word* offset; need to change it to bytes
131 cmmOffsetExprW e (CmmLit (CmmInt n _)) = cmmOffsetW e (fromInteger n)
132 cmmOffsetExprW e wd_off = cmmIndexExpr wordRep e wd_off
134 cmmOffsetW :: CmmExpr -> WordOff -> CmmExpr
135 cmmOffsetW e n = cmmOffsetB e (wORD_SIZE * n)
137 cmmRegOffW :: CmmReg -> WordOff -> CmmExpr
138 cmmRegOffW reg wd_off = cmmRegOffB reg (wd_off * wORD_SIZE)
140 cmmOffsetLitW :: CmmLit -> WordOff -> CmmLit
141 cmmOffsetLitW lit wd_off = cmmOffsetLitB lit (wORD_SIZE * wd_off)
143 cmmLabelOffW :: CLabel -> WordOff -> CmmLit
144 cmmLabelOffW lbl wd_off = cmmLabelOffB lbl (wORD_SIZE * wd_off)
146 cmmLoadIndexW :: CmmExpr -> Int -> CmmExpr
147 cmmLoadIndexW base off
148 = CmmLoad (cmmOffsetW base off) wordRep
150 -----------------------
151 cmmNeWord, cmmEqWord, cmmOrWord, cmmAndWord :: CmmExpr -> CmmExpr -> CmmExpr
152 cmmOrWord e1 e2 = CmmMachOp mo_wordOr [e1, e2]
153 cmmAndWord e1 e2 = CmmMachOp mo_wordAnd [e1, e2]
154 cmmNeWord e1 e2 = CmmMachOp mo_wordNe [e1, e2]
155 cmmEqWord e1 e2 = CmmMachOp mo_wordEq [e1, e2]
156 cmmULtWord e1 e2 = CmmMachOp mo_wordULt [e1, e2]
157 cmmUGeWord e1 e2 = CmmMachOp mo_wordUGe [e1, e2]
158 cmmUGtWord e1 e2 = CmmMachOp mo_wordUGt [e1, e2]
160 cmmNegate :: CmmExpr -> CmmExpr
161 cmmNegate (CmmLit (CmmInt n rep)) = CmmLit (CmmInt (-n) rep)
162 cmmNegate e = CmmMachOp (MO_S_Neg (cmmExprRep e)) [e]
164 blankWord :: CmmStatic
165 blankWord = CmmUninitialised wORD_SIZE
167 -----------------------
170 mkWordCLit :: StgWord -> CmmLit
171 mkWordCLit wd = CmmInt (fromIntegral wd) wordRep
173 packHalfWordsCLit :: (Integral a, Integral b) => a -> b -> CmmLit
174 -- Make a single word literal in which the lower_half_word is
175 -- at the lower address, and the upper_half_word is at the
177 -- ToDo: consider using half-word lits instead
178 -- but be careful: that's vulnerable when reversed
179 packHalfWordsCLit lower_half_word upper_half_word
180 #ifdef WORDS_BIGENDIAN
181 = mkWordCLit ((fromIntegral lower_half_word `shiftL` hALF_WORD_SIZE_IN_BITS)
182 .|. fromIntegral upper_half_word)
184 = mkWordCLit ((fromIntegral lower_half_word)
185 .|. (fromIntegral upper_half_word `shiftL` hALF_WORD_SIZE_IN_BITS))
188 --------------------------------------------------------------------------
190 -- Incrementing a memory location
192 --------------------------------------------------------------------------
194 addToMem :: MachRep -- rep of the counter
195 -> CmmExpr -- Address
196 -> Int -- What to add (a word)
198 addToMem rep ptr n = addToMemE rep ptr (CmmLit (CmmInt (toInteger n) rep))
200 addToMemE :: MachRep -- rep of the counter
201 -> CmmExpr -- Address
202 -> CmmExpr -- What to add (a word-typed expression)
205 = CmmStore ptr (CmmMachOp (MO_Add rep) [CmmLoad ptr rep, n])
207 -------------------------------------------------------------------------
209 -- Converting a closure tag to a closure for enumeration types
210 -- (this is the implementation of tagToEnum#).
212 -------------------------------------------------------------------------
214 tagToClosure :: HomeModules -> TyCon -> CmmExpr -> CmmExpr
215 tagToClosure hmods tycon tag
216 = CmmLoad (cmmOffsetExprW closure_tbl tag) wordRep
217 where closure_tbl = CmmLit (CmmLabel lbl)
218 lbl = mkClosureTableLabel hmods (tyConName tycon)
220 -------------------------------------------------------------------------
222 -- Conditionals and rts calls
224 -------------------------------------------------------------------------
226 emitIf :: CmmExpr -- Boolean
229 -- Emit (if e then x)
230 -- ToDo: reverse the condition to avoid the extra branch instruction if possible
231 -- (some conditionals aren't reversible. eg. floating point comparisons cannot
232 -- be inverted because there exist some values for which both comparisons
233 -- return False, such as NaN.)
234 emitIf cond then_part
235 = do { then_id <- newLabelC
236 ; join_id <- newLabelC
237 ; stmtC (CmmCondBranch cond then_id)
238 ; stmtC (CmmBranch join_id)
244 emitIfThenElse :: CmmExpr -- Boolean
248 -- Emit (if e then x else y)
249 emitIfThenElse cond then_part else_part
250 = do { then_id <- newLabelC
251 ; else_id <- newLabelC
252 ; join_id <- newLabelC
253 ; stmtC (CmmCondBranch cond then_id)
255 ; stmtC (CmmBranch join_id)
261 emitRtsCall :: LitString -> [(CmmExpr,MachHint)] -> Code
262 emitRtsCall fun args = emitRtsCall' [] fun args Nothing
263 -- The 'Nothing' says "save all global registers"
265 emitRtsCallWithVols :: LitString -> [(CmmExpr,MachHint)] -> [GlobalReg] -> Code
266 emitRtsCallWithVols fun args vols
267 = emitRtsCall' [] fun args (Just vols)
269 emitRtsCallWithResult :: CmmReg -> MachHint -> LitString
270 -> [(CmmExpr,MachHint)] -> Code
271 emitRtsCallWithResult res hint fun args
272 = emitRtsCall' [(res,hint)] fun args Nothing
274 -- Make a call to an RTS C procedure
276 :: [(CmmReg,MachHint)]
278 -> [(CmmExpr,MachHint)]
281 emitRtsCall' res fun args vols = stmtC (CmmCall target res args vols)
283 target = CmmForeignCall fun_expr CCallConv
284 fun_expr = mkLblExpr (mkRtsCodeLabel fun)
287 -------------------------------------------------------------------------
289 -- Strings gnerate a top-level data block
291 -------------------------------------------------------------------------
293 emitDataLits :: CLabel -> [CmmLit] -> Code
294 -- Emit a data-segment data block
295 emitDataLits lbl lits
296 = emitData Data (CmmDataLabel lbl : map CmmStaticLit lits)
298 emitRODataLits :: CLabel -> [CmmLit] -> Code
299 -- Emit a read-only data block
300 emitRODataLits lbl lits
301 = emitData section (CmmDataLabel lbl : map CmmStaticLit lits)
302 where section | any needsRelocation lits = RelocatableReadOnlyData
303 | otherwise = ReadOnlyData
304 needsRelocation (CmmLabel _) = True
305 needsRelocation (CmmLabelOff _ _) = True
306 needsRelocation _ = False
308 mkStringCLit :: String -> FCode CmmLit
309 -- Make a global definition for the string,
310 -- and return its label
312 = do { uniq <- newUnique
313 ; let lbl = mkStringLitLabel uniq
314 ; emitData ReadOnlyData [CmmDataLabel lbl, CmmString str]
315 ; return (CmmLabel lbl) }
317 -------------------------------------------------------------------------
319 -- Assigning expressions to temporaries
321 -------------------------------------------------------------------------
323 assignTemp :: CmmExpr -> FCode CmmExpr
324 -- For a non-trivial expression, e, create a local
325 -- variable and assign the expression to it
327 | isTrivialCmmExpr e = return e
328 | otherwise = do { reg <- newTemp (cmmExprRep e)
329 ; stmtC (CmmAssign reg e)
330 ; return (CmmReg reg) }
333 newTemp :: MachRep -> FCode CmmReg
334 newTemp rep = do { uniq <- newUnique; return (CmmLocal (LocalReg uniq rep)) }
337 -------------------------------------------------------------------------
339 -- Building case analysis
341 -------------------------------------------------------------------------
344 :: CmmExpr -- Tag to switch on
345 -> [(ConTagZ, CgStmts)] -- Tagged branches
346 -> Maybe CgStmts -- Default branch (if any)
347 -> ConTagZ -> ConTagZ -- Min and Max possible values; behaviour
348 -- outside this range is undefined
351 -- ONLY A DEFAULT BRANCH: no case analysis to do
352 emitSwitch tag_expr [] (Just stmts) _ _
356 emitSwitch tag_expr branches mb_deflt lo_tag hi_tag
357 = -- Just sort the branches before calling mk_sritch
360 Nothing -> return Nothing
361 Just stmts -> do id <- forkCgStmts stmts; return (Just id)
363 ; dflags <- getDynFlags
364 ; let via_C | HscC <- hscTarget dflags = True
367 ; stmts <- mk_switch tag_expr (sortLe le branches)
368 mb_deflt_id lo_tag hi_tag via_C
372 (t1,_) `le` (t2,_) = t1 <= t2
375 mk_switch :: CmmExpr -> [(ConTagZ, CgStmts)]
376 -> Maybe BlockId -> ConTagZ -> ConTagZ -> Bool
379 -- SINGLETON TAG RANGE: no case analysis to do
380 mk_switch tag_expr [(tag,stmts)] _ lo_tag hi_tag via_C
382 = ASSERT( tag == lo_tag )
385 -- SINGLETON BRANCH, NO DEFUALT: no case analysis to do
386 mk_switch tag_expr [(tag,stmts)] Nothing lo_tag hi_tag via_C
388 -- The simplifier might have eliminated a case
389 -- so we may have e.g. case xs of
391 -- In that situation we can be sure the (:) case
392 -- can't happen, so no need to test
394 -- SINGLETON BRANCH: one equality check to do
395 mk_switch tag_expr [(tag,stmts)] (Just deflt) lo_tag hi_tag via_C
396 = return (CmmCondBranch cond deflt `consCgStmt` stmts)
398 cond = cmmNeWord tag_expr (CmmLit (mkIntCLit tag))
399 -- We have lo_tag < hi_tag, but there's only one branch,
400 -- so there must be a default
402 -- ToDo: we might want to check for the two branch case, where one of
403 -- the branches is the tag 0, because comparing '== 0' is likely to be
404 -- more efficient than other kinds of comparison.
406 -- DENSE TAG RANGE: use a switch statment.
408 -- We also use a switch uncoditionally when compiling via C, because
409 -- this will get emitted as a C switch statement and the C compiler
410 -- should do a good job of optimising it. Also, older GCC versions
411 -- (2.95 in particular) have problems compiling the complicated
412 -- if-trees generated by this code, so compiling to a switch every
413 -- time works around that problem.
415 mk_switch tag_expr branches mb_deflt lo_tag hi_tag via_C
416 | use_switch -- Use a switch
417 = do { branch_ids <- mapM forkCgStmts (map snd branches)
419 tagged_blk_ids = zip (map fst branches) (map Just branch_ids)
421 find_branch :: ConTagZ -> Maybe BlockId
422 find_branch i = assocDefault mb_deflt tagged_blk_ids i
424 -- NB. we have eliminated impossible branches at
425 -- either end of the range (see below), so the first
426 -- tag of a real branch is real_lo_tag (not lo_tag).
427 arms = [ find_branch i | i <- [real_lo_tag..real_hi_tag]]
429 switch_stmt = CmmSwitch (cmmOffset tag_expr (- real_lo_tag)) arms
431 ; ASSERT(not (all isNothing arms))
432 return (oneCgStmt switch_stmt)
435 -- if we can knock off a bunch of default cases with one if, then do so
436 | Just deflt <- mb_deflt, (lowest_branch - lo_tag) >= n_branches
437 = do { (assign_tag, tag_expr') <- assignTemp' tag_expr
438 ; let cond = cmmULtWord tag_expr' (CmmLit (mkIntCLit lowest_branch))
439 branch = CmmCondBranch cond deflt
440 ; stmts <- mk_switch tag_expr' branches mb_deflt
441 lowest_branch hi_tag via_C
442 ; return (assign_tag `consCgStmt` (branch `consCgStmt` stmts))
445 | Just deflt <- mb_deflt, (hi_tag - highest_branch) >= n_branches
446 = do { (assign_tag, tag_expr') <- assignTemp' tag_expr
447 ; let cond = cmmUGtWord tag_expr' (CmmLit (mkIntCLit highest_branch))
448 branch = CmmCondBranch cond deflt
449 ; stmts <- mk_switch tag_expr' branches mb_deflt
450 lo_tag highest_branch via_C
451 ; return (assign_tag `consCgStmt` (branch `consCgStmt` stmts))
454 | otherwise -- Use an if-tree
455 = do { (assign_tag, tag_expr') <- assignTemp' tag_expr
456 -- To avoid duplication
457 ; lo_stmts <- mk_switch tag_expr' lo_branches mb_deflt
458 lo_tag (mid_tag-1) via_C
459 ; hi_stmts <- mk_switch tag_expr' hi_branches mb_deflt
461 ; hi_id <- forkCgStmts hi_stmts
462 ; let cond = cmmUGeWord tag_expr' (CmmLit (mkIntCLit mid_tag))
463 branch_stmt = CmmCondBranch cond hi_id
464 ; return (assign_tag `consCgStmt` (branch_stmt `consCgStmt` lo_stmts))
466 -- we test (e >= mid_tag) rather than (e < mid_tag), because
467 -- the former works better when e is a comparison, and there
468 -- are two tags 0 & 1 (mid_tag == 1). In this case, the code
469 -- generator can reduce the condition to e itself without
470 -- having to reverse the sense of the comparison: comparisons
471 -- can't always be easily reversed (eg. floating
474 use_switch = {- pprTrace "mk_switch" (
475 ppr tag_expr <+> text "n_tags:" <+> int n_tags <+>
476 text "n_branches:" <+> int n_branches <+>
477 text "lo_tag: " <+> int lo_tag <+>
478 text "hi_tag: " <+> int hi_tag <+>
479 text "real_lo_tag: " <+> int real_lo_tag <+>
480 text "real_hi_tag: " <+> int real_hi_tag) $ -}
481 ASSERT( n_branches > 1 && n_tags > 1 )
482 n_tags > 2 && (small || dense || via_C)
483 -- a 2-branch switch always turns into an if.
485 dense = n_branches > (n_tags `div` 2)
486 exhaustive = n_tags == n_branches
487 n_branches = length branches
489 -- ignore default slots at each end of the range if there's
490 -- no default branch defined.
491 lowest_branch = fst (head branches)
492 highest_branch = fst (last branches)
495 | isNothing mb_deflt = lowest_branch
499 | isNothing mb_deflt = highest_branch
502 n_tags = real_hi_tag - real_lo_tag + 1
504 -- INVARIANT: Provided hi_tag > lo_tag (which is true)
505 -- lo_tag <= mid_tag < hi_tag
506 -- lo_branches have tags < mid_tag
507 -- hi_branches have tags >= mid_tag
509 (mid_tag,_) = branches !! (n_branches `div` 2)
510 -- 2 branches => n_branches `div` 2 = 1
511 -- => branches !! 1 give the *second* tag
512 -- There are always at least 2 branches here
514 (lo_branches, hi_branches) = span is_lo branches
515 is_lo (t,_) = t < mid_tag
519 | isTrivialCmmExpr e = return (CmmNop, e)
520 | otherwise = do { reg <- newTemp (cmmExprRep e)
521 ; return (CmmAssign reg e, CmmReg reg) }
524 emitLitSwitch :: CmmExpr -- Tag to switch on
525 -> [(Literal, CgStmts)] -- Tagged branches
526 -> CgStmts -- Default branch (always)
527 -> Code -- Emit the code
528 -- Used for general literals, whose size might not be a word,
529 -- where there is always a default case, and where we don't know
530 -- the range of values for certain. For simplicity we always generate a tree.
532 -- ToDo: for integers we could do better here, perhaps by generalising
533 -- mk_switch and using that. --SDM 15/09/2004
534 emitLitSwitch scrut [] deflt
536 emitLitSwitch scrut branches deflt_blk
537 = do { scrut' <- assignTemp scrut
538 ; deflt_blk_id <- forkCgStmts deflt_blk
539 ; blk <- mk_lit_switch scrut' deflt_blk_id (sortLe le branches)
542 le (t1,_) (t2,_) = t1 <= t2
544 mk_lit_switch :: CmmExpr -> BlockId
545 -> [(Literal,CgStmts)]
547 mk_lit_switch scrut deflt_blk_id [(lit,blk)]
548 = return (consCgStmt if_stmt blk)
550 cmm_lit = mkSimpleLit lit
551 rep = cmmLitRep cmm_lit
552 cond = CmmMachOp (MO_Ne rep) [scrut, CmmLit cmm_lit]
553 if_stmt = CmmCondBranch cond deflt_blk_id
555 mk_lit_switch scrut deflt_blk_id branches
556 = do { hi_blk <- mk_lit_switch scrut deflt_blk_id hi_branches
557 ; lo_blk <- mk_lit_switch scrut deflt_blk_id lo_branches
558 ; lo_blk_id <- forkCgStmts lo_blk
559 ; let if_stmt = CmmCondBranch cond lo_blk_id
560 ; return (if_stmt `consCgStmt` hi_blk) }
562 n_branches = length branches
563 (mid_lit,_) = branches !! (n_branches `div` 2)
564 -- See notes above re mid_tag
566 (lo_branches, hi_branches) = span is_lo branches
567 is_lo (t,_) = t < mid_lit
569 cond = CmmMachOp (mkLtOp mid_lit)
570 [scrut, CmmLit (mkSimpleLit mid_lit)]
572 -------------------------------------------------------------------------
574 -- Simultaneous assignment
576 -------------------------------------------------------------------------
579 emitSimultaneously :: CmmStmts -> Code
580 -- Emit code to perform the assignments in the
581 -- input simultaneously, using temporary variables when necessary.
583 -- The Stmts must be:
584 -- CmmNop, CmmComment, CmmAssign, CmmStore
588 -- We use the strongly-connected component algorithm, in which
589 -- * the vertices are the statements
590 -- * an edge goes from s1 to s2 iff
591 -- s1 assigns to something s2 uses
592 -- that is, if s1 should *follow* s2 in the final order
594 type CVertex = (Int, CmmStmt) -- Give each vertex a unique number,
595 -- for fast comparison
597 emitSimultaneously stmts
599 case filterOut isNopStmt (stmtList stmts) of
602 [stmt] -> stmtC stmt -- It's often just one stmt
603 stmt_list -> doSimultaneously1 (zip [(1::Int)..] stmt_list)
605 doSimultaneously1 :: [CVertex] -> Code
606 doSimultaneously1 vertices
608 edges = [ (vertex, key1, edges_from stmt1)
609 | vertex@(key1, stmt1) <- vertices
611 edges_from stmt1 = [ key2 | (key2, stmt2) <- vertices,
612 stmt1 `mustFollow` stmt2
614 components = stronglyConnComp edges
616 -- do_components deal with one strongly-connected component
617 -- Not cyclic, or singleton? Just do it
618 do_component (AcyclicSCC (n,stmt)) = stmtC stmt
619 do_component (CyclicSCC [(n,stmt)]) = stmtC stmt
621 -- Cyclic? Then go via temporaries. Pick one to
622 -- break the loop and try again with the rest.
623 do_component (CyclicSCC ((n,first_stmt) : rest))
624 = do { from_temp <- go_via_temp first_stmt
625 ; doSimultaneously1 rest
628 go_via_temp (CmmAssign dest src)
629 = do { tmp <- newTemp (cmmRegRep dest)
630 ; stmtC (CmmAssign tmp src)
631 ; return (CmmAssign dest (CmmReg tmp)) }
632 go_via_temp (CmmStore dest src)
633 = do { tmp <- newTemp (cmmExprRep src)
634 ; stmtC (CmmAssign tmp src)
635 ; return (CmmStore dest (CmmReg tmp)) }
637 mapCs do_component components
639 mustFollow :: CmmStmt -> CmmStmt -> Bool
640 CmmAssign reg _ `mustFollow` stmt = anySrc (reg `regUsedIn`) stmt
641 CmmStore loc e `mustFollow` stmt = anySrc (locUsedIn loc (cmmExprRep e)) stmt
642 CmmNop `mustFollow` stmt = False
643 CmmComment _ `mustFollow` stmt = False
646 anySrc :: (CmmExpr -> Bool) -> CmmStmt -> Bool
647 -- True if the fn is true of any input of the stmt
648 anySrc p (CmmAssign _ e) = p e
649 anySrc p (CmmStore e1 e2) = p e1 || p e2 -- Might be used in either side
650 anySrc p (CmmComment _) = False
651 anySrc p CmmNop = False
652 anySrc p other = True -- Conservative
654 regUsedIn :: CmmReg -> CmmExpr -> Bool
655 reg `regUsedIn` CmmLit _ = False
656 reg `regUsedIn` CmmLoad e _ = reg `regUsedIn` e
657 reg `regUsedIn` CmmReg reg' = reg == reg'
658 reg `regUsedIn` CmmRegOff reg' _ = reg == reg'
659 reg `regUsedIn` CmmMachOp _ es = any (reg `regUsedIn`) es
661 locUsedIn :: CmmExpr -> MachRep -> CmmExpr -> Bool
662 -- (locUsedIn a r e) checks whether writing to r[a] could affect the value of
663 -- 'e'. Returns True if it's not sure.
664 locUsedIn loc rep (CmmLit _) = False
665 locUsedIn loc rep (CmmLoad e ld_rep) = possiblySameLoc loc rep e ld_rep
666 locUsedIn loc rep (CmmReg reg') = False
667 locUsedIn loc rep (CmmRegOff reg' _) = False
668 locUsedIn loc rep (CmmMachOp _ es) = any (locUsedIn loc rep) es
670 possiblySameLoc :: CmmExpr -> MachRep -> CmmExpr -> MachRep -> Bool
671 -- Assumes that distinct registers (eg Hp, Sp) do not
672 -- point to the same location, nor any offset thereof.
673 possiblySameLoc (CmmReg r1) rep1 (CmmReg r2) rep2 = r1==r2
674 possiblySameLoc (CmmReg r1) rep1 (CmmRegOff r2 0) rep2 = r1==r2
675 possiblySameLoc (CmmRegOff r1 0) rep1 (CmmReg r2) rep2 = r1==r2
676 possiblySameLoc (CmmRegOff r1 start1) rep1 (CmmRegOff r2 start2) rep2
677 = r1==r2 && end1 > start2 && end2 > start1
679 end1 = start1 + machRepByteWidth rep1
680 end2 = start2 + machRepByteWidth rep2
682 possiblySameLoc l1 rep1 (CmmLit _) rep2 = False
683 possiblySameLoc l1 rep1 l2 rep2 = True -- Conservative