1 -- -----------------------------------------------------------------------------
3 -- (c) The University of Glasgow 1993-2004
5 -- This is the top-level module in the native code generator.
7 -- -----------------------------------------------------------------------------
11 -- The above warning supression flag is a temporary kludge.
12 -- While working on this module you are encouraged to remove it and fix
13 -- any warnings in the module. See
14 -- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
17 module AsmCodeGen ( nativeCodeGen ) where
19 #include "HsVersions.h"
20 #include "nativeGen/NCG.h"
28 import PositionIndependentCode
31 import qualified RegAllocLinear as Linear
32 import qualified RegAllocColor as Color
33 import qualified RegAllocStats as Color
34 import qualified GraphColor as Color
37 import CmmOpt ( cmmMiniInline, cmmMachOpFold )
44 import Unique ( Unique, getUnique )
46 import List ( groupBy, sortBy )
48 #if powerpc_TARGET_ARCH
49 import StaticFlags ( opt_Static, opt_PIC )
52 import Config ( cProjectVersion )
56 import qualified Pretty
75 The native-code generator has machine-independent and
76 machine-dependent modules.
78 This module ("AsmCodeGen") is the top-level machine-independent
79 module. Before entering machine-dependent land, we do some
80 machine-independent optimisations (defined below) on the
83 We convert to the machine-specific 'Instr' datatype with
84 'cmmCodeGen', assuming an infinite supply of registers. We then use
85 a machine-independent register allocator ('regAlloc') to rejoin
86 reality. Obviously, 'regAlloc' has machine-specific helper
87 functions (see about "RegAllocInfo" below).
89 Finally, we order the basic blocks of the function so as to minimise
90 the number of jumps between blocks, by utilising fallthrough wherever
93 The machine-dependent bits break down as follows:
95 * ["MachRegs"] Everything about the target platform's machine
96 registers (and immediate operands, and addresses, which tend to
97 intermingle/interact with registers).
99 * ["MachInstrs"] Includes the 'Instr' datatype (possibly should
100 have a module of its own), plus a miscellany of other things
101 (e.g., 'targetDoubleSize', 'smStablePtrTable', ...)
103 * ["MachCodeGen"] is where 'Cmm' stuff turns into
104 machine instructions.
106 * ["PprMach"] 'pprInstr' turns an 'Instr' into text (well, really
109 * ["RegAllocInfo"] In the register allocator, we manipulate
110 'MRegsState's, which are 'BitSet's, one bit per machine register.
111 When we want to say something about a specific machine register
112 (e.g., ``it gets clobbered by this instruction''), we set/unset
113 its bit. Obviously, we do this 'BitSet' thing for efficiency
116 The 'RegAllocInfo' module collects together the machine-specific
117 info needed to do register allocation.
119 * ["RegisterAlloc"] The (machine-independent) register allocator.
122 -- -----------------------------------------------------------------------------
123 -- Top-level of the native codegen
126 nativeCodeGen :: DynFlags -> Handle -> UniqSupply -> [RawCmm] -> IO ()
127 nativeCodeGen dflags h us cmms
129 let split_cmms = concat $ map add_split cmms
132 <- cmmNativeGens dflags h us split_cmms [] []
134 let (native, colorStats, linearStats)
139 Opt_D_dump_asm "Asm code"
140 (vcat $ map (docToSDoc . pprNatCmmTop) $ concat native)
142 -- dump global NCG stats for graph coloring allocator
143 (case concat $ catMaybes colorStats of
146 -- build the global register conflict graph
148 = foldl Color.union Color.initGraph
149 $ [ Color.raGraph stat
150 | stat@Color.RegAllocStatsStart{} <- stats]
152 dumpSDoc dflags Opt_D_dump_asm_stats "NCG stats"
153 $ Color.pprStats stats graphGlobal
156 Opt_D_dump_asm_conflicts "Register conflict graph"
157 $ Color.dotGraph Color.regDotColor trivColorable
161 -- dump global NCG stats for linear allocator
162 (case concat $ catMaybes linearStats of
164 stats -> dumpSDoc dflags Opt_D_dump_asm_stats "NCG stats"
165 $ Linear.pprStats (concat native) stats)
167 -- write out the imports
168 Pretty.printDoc Pretty.LeftMode h
169 $ makeImportsDoc (concat imports)
173 where add_split (Cmm tops)
174 | dopt Opt_SplitObjs dflags = split_marker : tops
177 split_marker = CmmProc [] mkSplitMarkerLabel [] (ListGraph [])
180 -- | Do native code generation on all these cmms.
182 cmmNativeGens dflags h us [] impAcc profAcc
183 = return (reverse impAcc, reverse profAcc)
185 cmmNativeGens dflags h us (cmm : cmms) impAcc profAcc
187 (us', native, imports, colorStats, linearStats)
188 <- cmmNativeGen dflags us cmm
190 Pretty.printDoc Pretty.LeftMode h
191 $ {-# SCC "pprNativeCode" #-} Pretty.vcat $ map pprNatCmmTop native
194 if dopt Opt_D_dump_asm dflags
195 || dopt Opt_D_dump_asm_stats dflags
199 -- force evaulation all this stuff to avoid space leaks
200 seqString (showSDoc $ vcat $ map ppr imports) `seq` return ()
201 lsPprNative `seq` return ()
203 cmmNativeGens dflags h us' cmms
205 ((lsPprNative, colorStats, linearStats) : profAcc)
207 where seqString [] = ()
208 seqString (x:xs) = x `seq` seqString xs `seq` ()
211 -- | Complete native code generation phase for a single top-level chunk of Cmm.
212 -- Dumping the output of each stage along the way.
213 -- Global conflict graph and NGC stats
217 -> RawCmmTop -- ^ the cmm to generate code for
219 , [NatCmmTop] -- native code
220 , [CLabel] -- things imported by this cmm
221 , Maybe [Color.RegAllocStats] -- stats for the coloring register allocator
222 , Maybe [Linear.RegAllocStats]) -- stats for the linear register allocators
224 cmmNativeGen dflags us cmm
227 -- rewrite assignments to global regs
228 let (fixed_cmm, usFix) =
229 {-# SCC "fixAssignsTop" #-}
230 initUs us $ fixAssignsTop cmm
232 -- cmm to cmm optimisations
233 let (opt_cmm, imports) =
234 {-# SCC "cmmToCmm" #-}
235 cmmToCmm dflags fixed_cmm
238 Opt_D_dump_opt_cmm "Optimised Cmm"
239 (pprCmm $ Cmm [opt_cmm])
241 -- generate native code from cmm
242 let ((native, lastMinuteImports), usGen) =
243 {-# SCC "genMachCode" #-}
244 initUs usFix $ genMachCode dflags opt_cmm
247 Opt_D_dump_asm_native "Native code"
248 (vcat $ map (docToSDoc . pprNatCmmTop) native)
251 -- tag instructions with register liveness information
252 let (withLiveness, usLive) =
253 {-# SCC "regLiveness" #-}
254 initUs usGen $ mapUs regLiveness native
257 Opt_D_dump_asm_liveness "Liveness annotations added"
258 (vcat $ map ppr withLiveness)
261 -- allocate registers
262 (alloced, usAlloc, ppr_raStatsColor, ppr_raStatsLinear) <-
263 if ( dopt Opt_RegsGraph dflags
264 || dopt Opt_RegsIterative dflags)
266 -- the regs usable for allocation
268 = foldr (\r -> plusUFM_C unionUniqSets
269 $ unitUFM (regClass r) (unitUniqSet r))
271 $ map RealReg allocatableRegs
273 -- graph coloring register allocation
274 let ((alloced, regAllocStats), usAlloc)
275 = {-# SCC "RegAlloc" #-}
280 (mkUniqSet [0..maxSpillSlots])
283 -- dump out what happened during register allocation
285 Opt_D_dump_asm_regalloc "Registers allocated"
286 (vcat $ map (docToSDoc . pprNatCmmTop) alloced)
289 Opt_D_dump_asm_regalloc_stages "Build/spill stages"
290 (vcat $ map (\(stage, stats)
291 -> text " Stage " <> int stage
293 $ zip [0..] regAllocStats)
296 if dopt Opt_D_dump_asm_stats dflags
297 then Just regAllocStats else Nothing
299 -- force evaluation of the Maybe to avoid space leak
300 mPprStats `seq` return ()
302 return ( alloced, usAlloc
307 -- do linear register allocation
308 let ((alloced, regAllocStats), usAlloc)
309 = {-# SCC "RegAlloc" #-}
312 $ mapUs Linear.regAlloc withLiveness
315 Opt_D_dump_asm_regalloc "Registers allocated"
316 (vcat $ map (docToSDoc . pprNatCmmTop) alloced)
319 if dopt Opt_D_dump_asm_stats dflags
320 then Just (catMaybes regAllocStats) else Nothing
322 -- force evaluation of the Maybe to avoid space leak
323 mPprStats `seq` return ()
325 return ( alloced, usAlloc
329 ---- shortcut branches
331 {-# SCC "shortcutBranches" #-}
332 shortcutBranches dflags alloced
336 {-# SCC "sequenceBlocks" #-}
337 map sequenceTop shorted
340 let final_mach_code =
342 {-# SCC "x86fp_kludge" #-}
343 map x86fp_kludge sequenced
350 , lastMinuteImports ++ imports
356 x86fp_kludge :: NatCmmTop -> NatCmmTop
357 x86fp_kludge top@(CmmData _ _) = top
358 x86fp_kludge top@(CmmProc info lbl params (ListGraph code)) =
359 CmmProc info lbl params (ListGraph $ map bb_i386_insert_ffrees code)
361 bb_i386_insert_ffrees (BasicBlock id instrs) =
362 BasicBlock id (i386_insert_ffrees instrs)
366 -- | Build a doc for all the imports.
368 makeImportsDoc :: [CLabel] -> Pretty.Doc
369 makeImportsDoc imports
372 #if HAVE_SUBSECTIONS_VIA_SYMBOLS
373 -- On recent versions of Darwin, the linker supports
374 -- dead-stripping of code and data on a per-symbol basis.
375 -- There's a hack to make this work in PprMach.pprNatCmmTop.
376 Pretty.$$ Pretty.text ".subsections_via_symbols"
378 #if HAVE_GNU_NONEXEC_STACK
379 -- On recent GNU ELF systems one can mark an object file
380 -- as not requiring an executable stack. If all objects
381 -- linked into a program have this note then the program
382 -- will not use an executable stack, which is good for
383 -- security. GHC generated code does not need an executable
384 -- stack so add the note in:
385 Pretty.$$ Pretty.text ".section .note.GNU-stack,\"\",@progbits"
387 #if !defined(darwin_TARGET_OS)
388 -- And just because every other compiler does, lets stick in
389 -- an identifier directive: .ident "GHC x.y.z"
390 Pretty.$$ let compilerIdent = Pretty.text "GHC" Pretty.<+>
391 Pretty.text cProjectVersion
392 in Pretty.text ".ident" Pretty.<+>
393 Pretty.doubleQuotes compilerIdent
397 -- Generate "symbol stubs" for all external symbols that might
398 -- come from a dynamic library.
399 dyld_stubs :: [CLabel] -> Pretty.Doc
400 {- dyld_stubs imps = Pretty.vcat $ map pprDyldSymbolStub $
401 map head $ group $ sort imps-}
403 -- (Hack) sometimes two Labels pretty-print the same, but have
404 -- different uniques; so we compare their text versions...
406 | needImportedSymbols
408 (pprGotDeclaration :) $
409 map (pprImportedSymbol . fst . head) $
410 groupBy (\(_,a) (_,b) -> a == b) $
411 sortBy (\(_,a) (_,b) -> compare a b) $
417 doPpr lbl = (lbl, Pretty.render $ pprCLabel lbl astyle)
418 astyle = mkCodeStyle AsmStyle
421 -- -----------------------------------------------------------------------------
422 -- Sequencing the basic blocks
424 -- Cmm BasicBlocks are self-contained entities: they always end in a
425 -- jump, either non-local or to another basic block in the same proc.
426 -- In this phase, we attempt to place the basic blocks in a sequence
427 -- such that as many of the local jumps as possible turn into
430 sequenceTop :: NatCmmTop -> NatCmmTop
431 sequenceTop top@(CmmData _ _) = top
432 sequenceTop (CmmProc info lbl params (ListGraph blocks)) =
433 CmmProc info lbl params (ListGraph $ makeFarBranches $ sequenceBlocks blocks)
435 -- The algorithm is very simple (and stupid): we make a graph out of
436 -- the blocks where there is an edge from one block to another iff the
437 -- first block ends by jumping to the second. Then we topologically
438 -- sort this graph. Then traverse the list: for each block, we first
439 -- output the block, then if it has an out edge, we move the
440 -- destination of the out edge to the front of the list, and continue.
442 -- FYI, the classic layout for basic blocks uses postorder DFS; this
443 -- algorithm is implemented in cmm/ZipCfg.hs (NR 6 Sep 2007).
445 sequenceBlocks :: [NatBasicBlock] -> [NatBasicBlock]
446 sequenceBlocks [] = []
447 sequenceBlocks (entry:blocks) =
448 seqBlocks (mkNode entry : reverse (flattenSCCs (sccBlocks blocks)))
449 -- the first block is the entry point ==> it must remain at the start.
451 sccBlocks :: [NatBasicBlock] -> [SCC (NatBasicBlock,Unique,[Unique])]
452 sccBlocks blocks = stronglyConnCompR (map mkNode blocks)
454 getOutEdges :: [Instr] -> [Unique]
455 getOutEdges instrs = case jumpDests (last instrs) [] of
456 [one] -> [getUnique one]
458 -- we're only interested in the last instruction of
459 -- the block, and only if it has a single destination.
461 mkNode block@(BasicBlock id instrs) = (block, getUnique id, getOutEdges instrs)
464 seqBlocks ((block,_,[]) : rest)
465 = block : seqBlocks rest
466 seqBlocks ((block@(BasicBlock id instrs),_,[next]) : rest)
467 | can_fallthrough = BasicBlock id (init instrs) : seqBlocks rest'
468 | otherwise = block : seqBlocks rest'
470 (can_fallthrough, rest') = reorder next [] rest
471 -- TODO: we should do a better job for cycles; try to maximise the
472 -- fallthroughs within a loop.
473 seqBlocks _ = panic "AsmCodegen:seqBlocks"
475 reorder id accum [] = (False, reverse accum)
476 reorder id accum (b@(block,id',out) : rest)
477 | id == id' = (True, (block,id,out) : reverse accum ++ rest)
478 | otherwise = reorder id (b:accum) rest
481 -- -----------------------------------------------------------------------------
482 -- Making far branches
484 -- Conditional branches on PowerPC are limited to +-32KB; if our Procs get too
485 -- big, we have to work around this limitation.
487 makeFarBranches :: [NatBasicBlock] -> [NatBasicBlock]
489 #if powerpc_TARGET_ARCH
490 makeFarBranches blocks
491 | last blockAddresses < nearLimit = blocks
492 | otherwise = zipWith handleBlock blockAddresses blocks
494 blockAddresses = scanl (+) 0 $ map blockLen blocks
495 blockLen (BasicBlock _ instrs) = length instrs
497 handleBlock addr (BasicBlock id instrs)
498 = BasicBlock id (zipWith makeFar [addr..] instrs)
500 makeFar addr (BCC ALWAYS tgt) = BCC ALWAYS tgt
501 makeFar addr (BCC cond tgt)
502 | abs (addr - targetAddr) >= nearLimit
506 where Just targetAddr = lookupUFM blockAddressMap tgt
507 makeFar addr other = other
509 nearLimit = 7000 -- 8192 instructions are allowed; let's keep some
510 -- distance, as we have a few pseudo-insns that are
511 -- pretty-printed as multiple instructions,
512 -- and it's just not worth the effort to calculate
515 blockAddressMap = listToUFM $ zip (map blockId blocks) blockAddresses
520 -- -----------------------------------------------------------------------------
523 shortcutBranches :: DynFlags -> [NatCmmTop] -> [NatCmmTop]
524 shortcutBranches dflags tops
525 | optLevel dflags < 1 = tops -- only with -O or higher
526 | otherwise = map (apply_mapping mapping) tops'
528 (tops', mappings) = mapAndUnzip build_mapping tops
529 mapping = foldr plusUFM emptyUFM mappings
531 build_mapping top@(CmmData _ _) = (top, emptyUFM)
532 build_mapping (CmmProc info lbl params (ListGraph []))
533 = (CmmProc info lbl params (ListGraph []), emptyUFM)
534 build_mapping (CmmProc info lbl params (ListGraph (head:blocks)))
535 = (CmmProc info lbl params (ListGraph (head:others)), mapping)
536 -- drop the shorted blocks, but don't ever drop the first one,
537 -- because it is pointed to by a global label.
539 -- find all the blocks that just consist of a jump that can be
541 (shortcut_blocks, others) = partitionWith split blocks
542 split (BasicBlock id [insn]) | Just dest <- canShortcut insn
544 split other = Right other
546 -- build a mapping from BlockId to JumpDest for shorting branches
547 mapping = foldl add emptyUFM shortcut_blocks
548 add ufm (id,dest) = addToUFM ufm id dest
550 apply_mapping ufm (CmmData sec statics)
551 = CmmData sec (map (shortcutStatic (lookupUFM ufm)) statics)
552 -- we need to get the jump tables, so apply the mapping to the entries
554 apply_mapping ufm (CmmProc info lbl params (ListGraph blocks))
555 = CmmProc info lbl params (ListGraph $ map short_bb blocks)
557 short_bb (BasicBlock id insns) = BasicBlock id $! map short_insn insns
558 short_insn i = shortcutJump (lookupUFM ufm) i
559 -- shortcutJump should apply the mapping repeatedly,
560 -- just in case we can short multiple branches.
562 -- -----------------------------------------------------------------------------
563 -- Instruction selection
565 -- Native code instruction selection for a chunk of stix code. For
566 -- this part of the computation, we switch from the UniqSM monad to
567 -- the NatM monad. The latter carries not only a Unique, but also an
568 -- Int denoting the current C stack pointer offset in the generated
569 -- code; this is needed for creating correct spill offsets on
570 -- architectures which don't offer, or for which it would be
571 -- prohibitively expensive to employ, a frame pointer register. Viz,
574 -- The offset is measured in bytes, and indicates the difference
575 -- between the current (simulated) C stack-ptr and the value it was at
576 -- the beginning of the block. For stacks which grow down, this value
577 -- should be either zero or negative.
579 -- Switching between the two monads whilst carrying along the same
580 -- Unique supply breaks abstraction. Is that bad?
582 genMachCode :: DynFlags -> RawCmmTop -> UniqSM ([NatCmmTop], [CLabel])
584 genMachCode dflags cmm_top
585 = do { initial_us <- getUs
586 ; let initial_st = mkNatM_State initial_us 0 dflags
587 (new_tops, final_st) = initNat initial_st (cmmTopCodeGen cmm_top)
588 final_delta = natm_delta final_st
589 final_imports = natm_imports final_st
590 ; if final_delta == 0
591 then return (new_tops, final_imports)
592 else pprPanic "genMachCode: nonzero final delta" (int final_delta)
595 -- -----------------------------------------------------------------------------
596 -- Fixup assignments to global registers so that they assign to
597 -- locations within the RegTable, if appropriate.
599 -- Note that we currently don't fixup reads here: they're done by
600 -- the generic optimiser below, to avoid having two separate passes
603 fixAssignsTop :: RawCmmTop -> UniqSM RawCmmTop
604 fixAssignsTop top@(CmmData _ _) = returnUs top
605 fixAssignsTop (CmmProc info lbl params (ListGraph blocks)) =
606 mapUs fixAssignsBlock blocks `thenUs` \ blocks' ->
607 returnUs (CmmProc info lbl params (ListGraph blocks'))
609 fixAssignsBlock :: CmmBasicBlock -> UniqSM CmmBasicBlock
610 fixAssignsBlock (BasicBlock id stmts) =
611 fixAssigns stmts `thenUs` \ stmts' ->
612 returnUs (BasicBlock id stmts')
614 fixAssigns :: [CmmStmt] -> UniqSM [CmmStmt]
616 mapUs fixAssign stmts `thenUs` \ stmtss ->
617 returnUs (concat stmtss)
619 fixAssign :: CmmStmt -> UniqSM [CmmStmt]
620 fixAssign (CmmAssign (CmmGlobal reg) src)
621 | Left realreg <- reg_or_addr
622 = returnUs [CmmAssign (CmmGlobal reg) src]
623 | Right baseRegAddr <- reg_or_addr
624 = returnUs [CmmStore baseRegAddr src]
625 -- Replace register leaves with appropriate StixTrees for
626 -- the given target. GlobalRegs which map to a reg on this
627 -- arch are left unchanged. Assigning to BaseReg is always
628 -- illegal, so we check for that.
630 reg_or_addr = get_GlobalReg_reg_or_addr reg
632 fixAssign other_stmt = returnUs [other_stmt]
634 -- -----------------------------------------------------------------------------
635 -- Generic Cmm optimiser
641 (b) Simple inlining: a temporary which is assigned to and then
642 used, once, can be shorted.
643 (c) Replacement of references to GlobalRegs which do not have
644 machine registers by the appropriate memory load (eg.
645 Hp ==> *(BaseReg + 34) ).
646 (d) Position independent code and dynamic linking
647 (i) introduce the appropriate indirections
648 and position independent refs
649 (ii) compile a list of imported symbols
651 Ideas for other things we could do (ToDo):
653 - shortcut jumps-to-jumps
654 - eliminate dead code blocks
655 - simple CSE: if an expr is assigned to a temp, then replace later occs of
656 that expr with the temp, until the expr is no longer valid (can push through
657 temp assignments, and certain assigns to mem...)
660 cmmToCmm :: DynFlags -> RawCmmTop -> (RawCmmTop, [CLabel])
661 cmmToCmm _ top@(CmmData _ _) = (top, [])
662 cmmToCmm dflags (CmmProc info lbl params (ListGraph blocks)) = runCmmOpt dflags $ do
663 blocks' <- mapM cmmBlockConFold (cmmMiniInline blocks)
664 return $ CmmProc info lbl params (ListGraph blocks')
666 newtype CmmOptM a = CmmOptM (([CLabel], DynFlags) -> (# a, [CLabel] #))
668 instance Monad CmmOptM where
669 return x = CmmOptM $ \(imports, _) -> (# x,imports #)
671 CmmOptM $ \(imports, dflags) ->
672 case f (imports, dflags) of
675 CmmOptM g' -> g' (imports', dflags)
677 addImportCmmOpt :: CLabel -> CmmOptM ()
678 addImportCmmOpt lbl = CmmOptM $ \(imports, dflags) -> (# (), lbl:imports #)
680 getDynFlagsCmmOpt :: CmmOptM DynFlags
681 getDynFlagsCmmOpt = CmmOptM $ \(imports, dflags) -> (# dflags, imports #)
683 runCmmOpt :: DynFlags -> CmmOptM a -> (a, [CLabel])
684 runCmmOpt dflags (CmmOptM f) = case f ([], dflags) of
685 (# result, imports #) -> (result, imports)
687 cmmBlockConFold :: CmmBasicBlock -> CmmOptM CmmBasicBlock
688 cmmBlockConFold (BasicBlock id stmts) = do
689 stmts' <- mapM cmmStmtConFold stmts
690 return $ BasicBlock id stmts'
695 -> do src' <- cmmExprConFold DataReference src
696 return $ case src' of
697 CmmReg reg' | reg == reg' -> CmmNop
698 new_src -> CmmAssign reg new_src
701 -> do addr' <- cmmExprConFold DataReference addr
702 src' <- cmmExprConFold DataReference src
703 return $ CmmStore addr' src'
706 -> do addr' <- cmmExprConFold JumpReference addr
707 return $ CmmJump addr' regs
709 CmmCall target regs args srt returns
710 -> do target' <- case target of
711 CmmCallee e conv -> do
712 e' <- cmmExprConFold CallReference e
713 return $ CmmCallee e' conv
714 other -> return other
715 args' <- mapM (\(arg, hint) -> do
716 arg' <- cmmExprConFold DataReference arg
717 return (arg', hint)) args
718 return $ CmmCall target' regs args' srt returns
720 CmmCondBranch test dest
721 -> do test' <- cmmExprConFold DataReference test
722 return $ case test' of
723 CmmLit (CmmInt 0 _) ->
724 CmmComment (mkFastString ("deleted: " ++
725 showSDoc (pprStmt stmt)))
727 CmmLit (CmmInt n _) -> CmmBranch dest
728 other -> CmmCondBranch test' dest
731 -> do expr' <- cmmExprConFold DataReference expr
732 return $ CmmSwitch expr' ids
738 cmmExprConFold referenceKind expr
741 -> do addr' <- cmmExprConFold DataReference addr
742 return $ CmmLoad addr' rep
745 -- For MachOps, we first optimize the children, and then we try
746 -- our hand at some constant-folding.
747 -> do args' <- mapM (cmmExprConFold DataReference) args
748 return $ cmmMachOpFold mop args'
750 CmmLit (CmmLabel lbl)
752 dflags <- getDynFlagsCmmOpt
753 cmmMakeDynamicReference dflags addImportCmmOpt referenceKind lbl
754 CmmLit (CmmLabelOff lbl off)
756 dflags <- getDynFlagsCmmOpt
757 dynRef <- cmmMakeDynamicReference dflags addImportCmmOpt referenceKind lbl
758 return $ cmmMachOpFold (MO_Add wordRep) [
760 (CmmLit $ CmmInt (fromIntegral off) wordRep)
763 #if powerpc_TARGET_ARCH
764 -- On powerpc (non-PIC), it's easier to jump directly to a label than
765 -- to use the register table, so we replace these registers
766 -- with the corresponding labels:
767 CmmReg (CmmGlobal GCEnter1)
769 -> cmmExprConFold referenceKind $
770 CmmLit (CmmLabel (mkRtsCodeLabel SLIT( "__stg_gc_enter_1")))
771 CmmReg (CmmGlobal GCFun)
773 -> cmmExprConFold referenceKind $
774 CmmLit (CmmLabel (mkRtsCodeLabel SLIT( "__stg_gc_fun")))
777 CmmReg (CmmGlobal mid)
778 -- Replace register leaves with appropriate StixTrees for
779 -- the given target. MagicIds which map to a reg on this
780 -- arch are left unchanged. For the rest, BaseReg is taken
781 -- to mean the address of the reg table in MainCapability,
782 -- and for all others we generate an indirection to its
783 -- location in the register table.
784 -> case get_GlobalReg_reg_or_addr mid of
785 Left realreg -> return expr
788 BaseReg -> cmmExprConFold DataReference baseRegAddr
789 other -> cmmExprConFold DataReference
790 (CmmLoad baseRegAddr (globalRegRep mid))
791 -- eliminate zero offsets
793 -> cmmExprConFold referenceKind (CmmReg reg)
795 CmmRegOff (CmmGlobal mid) offset
796 -- RegOf leaves are just a shorthand form. If the reg maps
797 -- to a real reg, we keep the shorthand, otherwise, we just
798 -- expand it and defer to the above code.
799 -> case get_GlobalReg_reg_or_addr mid of
800 Left realreg -> return expr
802 -> cmmExprConFold DataReference (CmmMachOp (MO_Add wordRep) [
803 CmmReg (CmmGlobal mid),
804 CmmLit (CmmInt (fromIntegral offset)
809 -- -----------------------------------------------------------------------------