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, 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 )
56 import FastString ( LitString, FastString, unpackFS )
60 import Maybe ( isNothing )
62 #include "../includes/ghcconfig.h"
63 -- For WORDS_BIGENDIAN
65 -------------------------------------------------------------------------
67 -- Random small functions
69 -------------------------------------------------------------------------
71 addIdReps :: [Id] -> [(CgRep, Id)]
72 addIdReps ids = [(idCgRep id, id) | id <- ids]
74 -------------------------------------------------------------------------
78 -------------------------------------------------------------------------
80 cgLit :: Literal -> FCode CmmLit
81 cgLit (MachStr s) = mkStringCLit (unpackFS s)
82 cgLit other_lit = return (mkSimpleLit other_lit)
84 mkSimpleLit :: Literal -> CmmLit
85 mkSimpleLit (MachChar c) = CmmInt (fromIntegral (ord c)) wordRep
86 mkSimpleLit MachNullAddr = zeroCLit
87 mkSimpleLit (MachInt i) = CmmInt i wordRep
88 mkSimpleLit (MachInt64 i) = CmmInt i I64
89 mkSimpleLit (MachWord i) = CmmInt i wordRep
90 mkSimpleLit (MachWord64 i) = CmmInt i I64
91 mkSimpleLit (MachFloat r) = CmmFloat r F32
92 mkSimpleLit (MachDouble r) = CmmFloat r F64
93 mkSimpleLit (MachLabel fs ms) = CmmLabel (mkForeignLabel fs ms is_dyn)
95 is_dyn = False -- ToDo: fix me
97 mkLtOp :: Literal -> MachOp
98 -- On signed literals we must do a signed comparison
99 mkLtOp (MachInt _) = MO_S_Lt wordRep
100 mkLtOp (MachFloat _) = MO_S_Lt F32
101 mkLtOp (MachDouble _) = MO_S_Lt F64
102 mkLtOp lit = MO_U_Lt (cmmLitRep (mkSimpleLit lit))
105 ---------------------------------------------------
107 -- Cmm data type functions
109 ---------------------------------------------------
111 -----------------------
112 -- The "B" variants take byte offsets
113 cmmRegOffB :: CmmReg -> ByteOff -> CmmExpr
114 cmmRegOffB = cmmRegOff
116 cmmOffsetB :: CmmExpr -> ByteOff -> CmmExpr
117 cmmOffsetB = cmmOffset
119 cmmOffsetExprB :: CmmExpr -> CmmExpr -> CmmExpr
120 cmmOffsetExprB = cmmOffsetExpr
122 cmmLabelOffB :: CLabel -> ByteOff -> CmmLit
123 cmmLabelOffB = cmmLabelOff
125 cmmOffsetLitB :: CmmLit -> ByteOff -> CmmLit
126 cmmOffsetLitB = cmmOffsetLit
128 -----------------------
129 -- The "W" variants take word offsets
130 cmmOffsetExprW :: CmmExpr -> CmmExpr -> CmmExpr
131 -- The second arg is a *word* offset; need to change it to bytes
132 cmmOffsetExprW e (CmmLit (CmmInt n _)) = cmmOffsetW e (fromInteger n)
133 cmmOffsetExprW e wd_off = cmmIndexExpr wordRep e wd_off
135 cmmOffsetW :: CmmExpr -> WordOff -> CmmExpr
136 cmmOffsetW e n = cmmOffsetB e (wORD_SIZE * n)
138 cmmRegOffW :: CmmReg -> WordOff -> CmmExpr
139 cmmRegOffW reg wd_off = cmmRegOffB reg (wd_off * wORD_SIZE)
141 cmmOffsetLitW :: CmmLit -> WordOff -> CmmLit
142 cmmOffsetLitW lit wd_off = cmmOffsetLitB lit (wORD_SIZE * wd_off)
144 cmmLabelOffW :: CLabel -> WordOff -> CmmLit
145 cmmLabelOffW lbl wd_off = cmmLabelOffB lbl (wORD_SIZE * wd_off)
147 cmmLoadIndexW :: CmmExpr -> Int -> CmmExpr
148 cmmLoadIndexW base off
149 = CmmLoad (cmmOffsetW base off) wordRep
151 -----------------------
152 cmmNeWord, cmmEqWord, cmmOrWord, cmmAndWord :: CmmExpr -> CmmExpr -> CmmExpr
153 cmmOrWord e1 e2 = CmmMachOp mo_wordOr [e1, e2]
154 cmmAndWord e1 e2 = CmmMachOp mo_wordAnd [e1, e2]
155 cmmNeWord e1 e2 = CmmMachOp mo_wordNe [e1, e2]
156 cmmEqWord e1 e2 = CmmMachOp mo_wordEq [e1, e2]
157 cmmULtWord e1 e2 = CmmMachOp mo_wordULt [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 :: TyCon -> CmmExpr -> CmmExpr
215 tagToClosure tycon tag
216 = CmmLoad (cmmOffsetExprW closure_tbl tag) wordRep
217 where closure_tbl = CmmLit (CmmLabel (mkClosureTblLabel (tyConName tycon)))
219 -------------------------------------------------------------------------
221 -- Conditionals and rts calls
223 -------------------------------------------------------------------------
225 emitIf :: CmmExpr -- Boolean
228 -- Emit (if e then x)
229 -- ToDo: reverse the condition to avoid the extra branch instruction if possible
230 -- (some conditionals aren't reversible. eg. floating point comparisons cannot
231 -- be inverted because there exist some values for which both comparisons
232 -- return False, such as NaN.)
233 emitIf cond then_part
234 = do { then_id <- newLabelC
235 ; join_id <- newLabelC
236 ; stmtC (CmmCondBranch cond then_id)
237 ; stmtC (CmmBranch join_id)
243 emitIfThenElse :: CmmExpr -- Boolean
247 -- Emit (if e then x else y)
248 emitIfThenElse cond then_part else_part
249 = do { then_id <- newLabelC
250 ; else_id <- newLabelC
251 ; join_id <- newLabelC
252 ; stmtC (CmmCondBranch cond then_id)
254 ; stmtC (CmmBranch join_id)
260 emitRtsCall :: LitString -> [(CmmExpr,MachHint)] -> Code
261 emitRtsCall fun args = emitRtsCall' [] fun args Nothing
262 -- The 'Nothing' says "save all global registers"
264 emitRtsCallWithVols :: LitString -> [(CmmExpr,MachHint)] -> [GlobalReg] -> Code
265 emitRtsCallWithVols fun args vols
266 = emitRtsCall' [] fun args (Just vols)
268 emitRtsCallWithResult :: CmmReg -> MachHint -> LitString
269 -> [(CmmExpr,MachHint)] -> Code
270 emitRtsCallWithResult res hint fun args
271 = emitRtsCall' [(res,hint)] fun args Nothing
273 -- Make a call to an RTS C procedure
275 :: [(CmmReg,MachHint)]
277 -> [(CmmExpr,MachHint)]
280 emitRtsCall' res fun args vols = stmtC (CmmCall target res args vols)
282 target = CmmForeignCall fun_expr CCallConv
283 fun_expr = mkLblExpr (mkRtsCodeLabel fun)
286 -------------------------------------------------------------------------
288 -- Strings gnerate a top-level data block
290 -------------------------------------------------------------------------
292 emitDataLits :: CLabel -> [CmmLit] -> Code
293 -- Emit a data-segment data block
294 emitDataLits lbl lits
295 = emitData Data (CmmDataLabel lbl : map CmmStaticLit lits)
297 emitRODataLits :: CLabel -> [CmmLit] -> Code
298 -- Emit a read-only data block
299 emitRODataLits lbl lits
300 = emitData ReadOnlyData (CmmDataLabel lbl : map CmmStaticLit lits)
302 mkStringCLit :: String -> FCode CmmLit
303 -- Make a global definition for the string,
304 -- and return its label
306 = do { uniq <- newUnique
307 ; let lbl = mkStringLitLabel uniq
308 ; emitData ReadOnlyData [CmmDataLabel lbl, CmmString str]
309 ; return (CmmLabel lbl) }
311 -------------------------------------------------------------------------
313 -- Assigning expressions to temporaries
315 -------------------------------------------------------------------------
317 assignTemp :: CmmExpr -> FCode CmmExpr
318 -- For a non-trivial expression, e, create a local
319 -- variable and assign the expression to it
321 | isTrivialCmmExpr e = return e
322 | otherwise = do { reg <- newTemp (cmmExprRep e)
323 ; stmtC (CmmAssign reg e)
324 ; return (CmmReg reg) }
327 newTemp :: MachRep -> FCode CmmReg
328 newTemp rep = do { uniq <- newUnique; return (CmmLocal (LocalReg uniq rep)) }
331 -------------------------------------------------------------------------
333 -- Building case analysis
335 -------------------------------------------------------------------------
338 :: CmmExpr -- Tag to switch on
339 -> [(ConTagZ, CgStmts)] -- Tagged branches
340 -> Maybe CgStmts -- Default branch (if any)
341 -> ConTagZ -> ConTagZ -- Min and Max possible values; behaviour
342 -- outside this range is undefined
345 -- ONLY A DEFAULT BRANCH: no case analysis to do
346 emitSwitch tag_expr [] (Just stmts) _ _
350 emitSwitch tag_expr branches mb_deflt lo_tag hi_tag
351 = -- Just sort the branches before calling mk_sritch
354 Nothing -> return Nothing
355 Just stmts -> do id <- forkCgStmts stmts; return (Just id)
357 ; stmts <- mk_switch tag_expr (sortLe le branches)
358 mb_deflt_id lo_tag hi_tag
362 (t1,_) `le` (t2,_) = t1 <= t2
365 mk_switch :: CmmExpr -> [(ConTagZ, CgStmts)]
366 -> Maybe BlockId -> ConTagZ -> ConTagZ
369 -- SINGLETON TAG RANGE: no case analysis to do
370 mk_switch tag_expr [(tag,stmts)] _ lo_tag hi_tag
372 = ASSERT( tag == lo_tag )
375 -- SINGLETON BRANCH, NO DEFUALT: no case analysis to do
376 mk_switch tag_expr [(tag,stmts)] Nothing lo_tag hi_tag
378 -- The simplifier might have eliminated a case
379 -- so we may have e.g. case xs of
381 -- In that situation we can be sure the (:) case
382 -- can't happen, so no need to test
384 -- SINGLETON BRANCH: one equality check to do
385 mk_switch tag_expr [(tag,stmts)] (Just deflt) lo_tag hi_tag
386 = return (CmmCondBranch cond deflt `consCgStmt` stmts)
388 cond = cmmNeWord tag_expr (CmmLit (mkIntCLit tag))
389 -- We have lo_tag < hi_tag, but there's only one branch,
390 -- so there must be a default
392 -- ToDo: we might want to check for the two branch case, where one of
393 -- the branches is the tag 0, because comparing '== 0' is likely to be
394 -- more efficient than other kinds of comparison.
396 -- DENSE TAG RANGE: use a switch statment
397 mk_switch tag_expr branches mb_deflt lo_tag hi_tag
398 | use_switch -- Use a switch
399 = do { branch_ids <- mapM forkCgStmts (map snd branches)
401 tagged_blk_ids = zip (map fst branches) (map Just branch_ids)
403 find_branch :: ConTagZ -> Maybe BlockId
404 find_branch i = assocDefault mb_deflt tagged_blk_ids i
406 arms = [ find_branch (i+lo_tag) | i <- [0..n_tags-1]]
408 switch_stmt = CmmSwitch (cmmOffset tag_expr (- lo_tag)) arms
410 ; return (oneCgStmt switch_stmt)
413 -- if we can knock off a bunch of default cases with one if, then do so
414 | Just deflt <- mb_deflt, (lowest_branch - lo_tag) >= n_branches
415 = do { (assign_tag, tag_expr') <- assignTemp' tag_expr
416 ; let cond = cmmULtWord tag_expr' (CmmLit (mkIntCLit lowest_branch))
417 ; stmtC (CmmCondBranch cond deflt)
418 ; mk_switch tag_expr' branches mb_deflt lowest_branch hi_tag
421 | Just deflt <- mb_deflt, (hi_tag - highest_branch) >= n_branches
422 = do { (assign_tag, tag_expr') <- assignTemp' tag_expr
423 ; let cond = cmmUGtWord tag_expr' (CmmLit (mkIntCLit highest_branch))
424 ; stmtC (CmmCondBranch cond deflt)
425 ; mk_switch tag_expr' branches mb_deflt lo_tag highest_branch
428 | otherwise -- Use an if-tree
429 = do { (assign_tag, tag_expr') <- assignTemp' tag_expr
430 -- To avoid duplication
431 ; lo_stmts <- mk_switch tag_expr' lo_branches mb_deflt lo_tag (mid_tag-1)
432 ; hi_stmts <- mk_switch tag_expr' hi_branches mb_deflt mid_tag hi_tag
433 ; lo_id <- forkCgStmts lo_stmts
434 ; let cond = cmmULtWord tag_expr' (CmmLit (mkIntCLit mid_tag))
435 branch_stmt = CmmCondBranch cond lo_id
436 ; return (assign_tag `consCgStmt` (branch_stmt `consCgStmt` hi_stmts))
439 use_switch = ASSERT( n_branches > 1 && n_tags > 1 )
440 {- pprTrace "mk_switch" (ppr tag_expr <+> text "n_tags: "
441 <+> int n_tags <+> text "dense: "
442 <+> int n_branches) $ -}
443 n_tags > 2 && (small || dense)
444 -- a 2-branch switch always turns into an if.
446 dense = n_branches > (n_tags `div` 2)
447 exhaustive = n_tags == n_branches
448 n_branches = length branches
450 -- ignore default slots at each end of the range if there's
451 -- no default branch defined.
452 lowest_branch = fst (head branches)
453 highest_branch = fst (last branches)
456 | isNothing mb_deflt = lowest_branch
460 | isNothing mb_deflt = highest_branch
463 n_tags = real_hi_tag - real_lo_tag + 1
465 -- INVARIANT: Provided hi_tag > lo_tag (which is true)
466 -- lo_tag <= mid_tag < hi_tag
467 -- lo_branches have tags < mid_tag
468 -- hi_branches have tags >= mid_tag
470 (mid_tag,_) = branches !! (n_branches `div` 2)
471 -- 2 branches => n_branches `div` 2 = 1
472 -- => branches !! 1 give the *second* tag
473 -- There are always at least 2 branches here
475 (lo_branches, hi_branches) = span is_lo branches
476 is_lo (t,_) = t < mid_tag
480 | isTrivialCmmExpr e = return (CmmNop, e)
481 | otherwise = do { reg <- newTemp (cmmExprRep e)
482 ; return (CmmAssign reg e, CmmReg reg) }
485 emitLitSwitch :: CmmExpr -- Tag to switch on
486 -> [(Literal, CgStmts)] -- Tagged branches
487 -> CgStmts -- Default branch (always)
488 -> Code -- Emit the code
489 -- Used for general literals, whose size might not be a word,
490 -- where there is always a default case, and where we don't know
491 -- the range of values for certain. For simplicity we always generate a tree.
493 -- ToDo: for integers we could do better here, perhaps by generalising
494 -- mk_switch and using that. --SDM 15/09/2004
495 emitLitSwitch scrut [] deflt
497 emitLitSwitch scrut branches deflt_blk
498 = do { scrut' <- assignTemp scrut
499 ; deflt_blk_id <- forkCgStmts deflt_blk
500 ; blk <- mk_lit_switch scrut' deflt_blk_id (sortLe le branches)
503 le (t1,_) (t2,_) = t1 <= t2
505 mk_lit_switch :: CmmExpr -> BlockId
506 -> [(Literal,CgStmts)]
508 mk_lit_switch scrut deflt_blk_id [(lit,blk)]
509 = return (consCgStmt if_stmt blk)
511 cmm_lit = mkSimpleLit lit
512 rep = cmmLitRep cmm_lit
513 cond = CmmMachOp (MO_Ne rep) [scrut, CmmLit cmm_lit]
514 if_stmt = CmmCondBranch cond deflt_blk_id
516 mk_lit_switch scrut deflt_blk_id branches
517 = do { hi_blk <- mk_lit_switch scrut deflt_blk_id hi_branches
518 ; lo_blk <- mk_lit_switch scrut deflt_blk_id lo_branches
519 ; lo_blk_id <- forkCgStmts lo_blk
520 ; let if_stmt = CmmCondBranch cond lo_blk_id
521 ; return (if_stmt `consCgStmt` hi_blk) }
523 n_branches = length branches
524 (mid_lit,_) = branches !! (n_branches `div` 2)
525 -- See notes above re mid_tag
527 (lo_branches, hi_branches) = span is_lo branches
528 is_lo (t,_) = t < mid_lit
530 cond = CmmMachOp (mkLtOp mid_lit)
531 [scrut, CmmLit (mkSimpleLit mid_lit)]
533 -------------------------------------------------------------------------
535 -- Simultaneous assignment
537 -------------------------------------------------------------------------
540 emitSimultaneously :: CmmStmts -> Code
541 -- Emit code to perform the assignments in the
542 -- input simultaneously, using temporary variables when necessary.
544 -- The Stmts must be:
545 -- CmmNop, CmmComment, CmmAssign, CmmStore
549 -- We use the strongly-connected component algorithm, in which
550 -- * the vertices are the statements
551 -- * an edge goes from s1 to s2 iff
552 -- s1 assigns to something s2 uses
553 -- that is, if s1 should *follow* s2 in the final order
555 type CVertex = (Int, CmmStmt) -- Give each vertex a unique number,
556 -- for fast comparison
558 emitSimultaneously stmts
560 case filterOut isNopStmt (stmtList stmts) of
563 [stmt] -> stmtC stmt -- It's often just one stmt
564 stmt_list -> doSimultaneously1 (zip [(1::Int)..] stmt_list)
566 doSimultaneously1 :: [CVertex] -> Code
567 doSimultaneously1 vertices
569 edges = [ (vertex, key1, edges_from stmt1)
570 | vertex@(key1, stmt1) <- vertices
572 edges_from stmt1 = [ key2 | (key2, stmt2) <- vertices,
573 stmt1 `mustFollow` stmt2
575 components = stronglyConnComp edges
577 -- do_components deal with one strongly-connected component
578 -- Not cyclic, or singleton? Just do it
579 do_component (AcyclicSCC (n,stmt)) = stmtC stmt
580 do_component (CyclicSCC [(n,stmt)]) = stmtC stmt
582 -- Cyclic? Then go via temporaries. Pick one to
583 -- break the loop and try again with the rest.
584 do_component (CyclicSCC ((n,first_stmt) : rest))
585 = do { from_temp <- go_via_temp first_stmt
586 ; doSimultaneously1 rest
589 go_via_temp (CmmAssign dest src)
590 = do { tmp <- newTemp (cmmRegRep dest)
591 ; stmtC (CmmAssign tmp src)
592 ; return (CmmAssign dest (CmmReg tmp)) }
593 go_via_temp (CmmStore dest src)
594 = do { tmp <- newTemp (cmmExprRep src)
595 ; stmtC (CmmAssign tmp src)
596 ; return (CmmStore dest (CmmReg tmp)) }
598 mapCs do_component components
600 mustFollow :: CmmStmt -> CmmStmt -> Bool
601 CmmAssign reg _ `mustFollow` stmt = anySrc (reg `regUsedIn`) stmt
602 CmmStore loc e `mustFollow` stmt = anySrc (locUsedIn loc (cmmExprRep e)) stmt
603 CmmNop `mustFollow` stmt = False
604 CmmComment _ `mustFollow` stmt = False
607 anySrc :: (CmmExpr -> Bool) -> CmmStmt -> Bool
608 -- True if the fn is true of any input of the stmt
609 anySrc p (CmmAssign _ e) = p e
610 anySrc p (CmmStore e1 e2) = p e1 || p e2 -- Might be used in either side
611 anySrc p (CmmComment _) = False
612 anySrc p CmmNop = False
613 anySrc p other = True -- Conservative
615 regUsedIn :: CmmReg -> CmmExpr -> Bool
616 reg `regUsedIn` CmmLit _ = False
617 reg `regUsedIn` CmmLoad e _ = reg `regUsedIn` e
618 reg `regUsedIn` CmmReg reg' = reg == reg'
619 reg `regUsedIn` CmmRegOff reg' _ = reg == reg'
620 reg `regUsedIn` CmmMachOp _ es = any (reg `regUsedIn`) es
622 locUsedIn :: CmmExpr -> MachRep -> CmmExpr -> Bool
623 -- (locUsedIn a r e) checks whether writing to r[a] could affect the value of
624 -- 'e'. Returns True if it's not sure.
625 locUsedIn loc rep (CmmLit _) = False
626 locUsedIn loc rep (CmmLoad e ld_rep) = possiblySameLoc loc rep e ld_rep
627 locUsedIn loc rep (CmmReg reg') = False
628 locUsedIn loc rep (CmmRegOff reg' _) = False
629 locUsedIn loc rep (CmmMachOp _ es) = any (locUsedIn loc rep) es
631 possiblySameLoc :: CmmExpr -> MachRep -> CmmExpr -> MachRep -> Bool
632 -- Assumes that distinct registers (eg Hp, Sp) do not
633 -- point to the same location, nor any offset thereof.
634 possiblySameLoc (CmmReg r1) rep1 (CmmReg r2) rep2 = r1==r2
635 possiblySameLoc (CmmReg r1) rep1 (CmmRegOff r2 0) rep2 = r1==r2
636 possiblySameLoc (CmmRegOff r1 0) rep1 (CmmReg r2) rep2 = r1==r2
637 possiblySameLoc (CmmRegOff r1 start1) rep1 (CmmRegOff r2 start2) rep2
638 = r1==r2 && end1 > start2 && end2 > start1
640 end1 = start1 + machRepByteWidth rep1
641 end2 = start2 + machRepByteWidth rep2
643 possiblySameLoc l1 rep1 (CmmLit _) rep2 = False
644 possiblySameLoc l1 rep1 l2 rep2 = True -- Conservative