1 //===-- TwoAddressInstructionPass.cpp - Two-Address instruction pass ------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the TwoAddress instruction pass which is used
11 // by most register allocators. Two-Address instructions are rewritten
21 // Note that if a register allocator chooses to use this pass, that it
22 // has to be capable of handling the non-SSA nature of these rewritten
25 // It is also worth noting that the duplicate operand of the two
26 // address instruction is removed.
28 //===----------------------------------------------------------------------===//
30 #define DEBUG_TYPE "twoaddrinstr"
31 #include "llvm/CodeGen/Passes.h"
32 #include "llvm/ADT/BitVector.h"
33 #include "llvm/ADT/DenseMap.h"
34 #include "llvm/ADT/STLExtras.h"
35 #include "llvm/ADT/SmallSet.h"
36 #include "llvm/ADT/Statistic.h"
37 #include "llvm/Analysis/AliasAnalysis.h"
38 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
39 #include "llvm/CodeGen/LiveVariables.h"
40 #include "llvm/CodeGen/MachineFunctionPass.h"
41 #include "llvm/CodeGen/MachineInstr.h"
42 #include "llvm/CodeGen/MachineInstrBuilder.h"
43 #include "llvm/CodeGen/MachineRegisterInfo.h"
44 #include "llvm/IR/Function.h"
45 #include "llvm/MC/MCInstrItineraries.h"
46 #include "llvm/Support/Debug.h"
47 #include "llvm/Support/ErrorHandling.h"
48 #include "llvm/Target/TargetInstrInfo.h"
49 #include "llvm/Target/TargetMachine.h"
50 #include "llvm/Target/TargetOptions.h"
51 #include "llvm/Target/TargetRegisterInfo.h"
54 STATISTIC(NumTwoAddressInstrs, "Number of two-address instructions");
55 STATISTIC(NumCommuted , "Number of instructions commuted to coalesce");
56 STATISTIC(NumAggrCommuted , "Number of instructions aggressively commuted");
57 STATISTIC(NumConvertedTo3Addr, "Number of instructions promoted to 3-address");
58 STATISTIC(Num3AddrSunk, "Number of 3-address instructions sunk");
59 STATISTIC(NumReSchedUps, "Number of instructions re-scheduled up");
60 STATISTIC(NumReSchedDowns, "Number of instructions re-scheduled down");
63 class TwoAddressInstructionPass : public MachineFunctionPass {
65 const TargetInstrInfo *TII;
66 const TargetRegisterInfo *TRI;
67 const InstrItineraryData *InstrItins;
68 MachineRegisterInfo *MRI;
72 CodeGenOpt::Level OptLevel;
74 // The current basic block being processed.
75 MachineBasicBlock *MBB;
77 // DistanceMap - Keep track the distance of a MI from the start of the
78 // current basic block.
79 DenseMap<MachineInstr*, unsigned> DistanceMap;
81 // Set of already processed instructions in the current block.
82 SmallPtrSet<MachineInstr*, 8> Processed;
84 // SrcRegMap - A map from virtual registers to physical registers which are
85 // likely targets to be coalesced to due to copies from physical registers to
86 // virtual registers. e.g. v1024 = move r0.
87 DenseMap<unsigned, unsigned> SrcRegMap;
89 // DstRegMap - A map from virtual registers to physical registers which are
90 // likely targets to be coalesced to due to copies to physical registers from
91 // virtual registers. e.g. r1 = move v1024.
92 DenseMap<unsigned, unsigned> DstRegMap;
94 bool sink3AddrInstruction(MachineInstr *MI, unsigned Reg,
95 MachineBasicBlock::iterator OldPos);
97 bool noUseAfterLastDef(unsigned Reg, unsigned Dist, unsigned &LastDef);
99 bool isProfitableToCommute(unsigned regA, unsigned regB, unsigned regC,
100 MachineInstr *MI, unsigned Dist);
102 bool commuteInstruction(MachineBasicBlock::iterator &mi,
103 unsigned RegB, unsigned RegC, unsigned Dist);
105 bool isProfitableToConv3Addr(unsigned RegA, unsigned RegB);
107 bool convertInstTo3Addr(MachineBasicBlock::iterator &mi,
108 MachineBasicBlock::iterator &nmi,
109 unsigned RegA, unsigned RegB, unsigned Dist);
111 bool isDefTooClose(unsigned Reg, unsigned Dist, MachineInstr *MI);
113 bool rescheduleMIBelowKill(MachineBasicBlock::iterator &mi,
114 MachineBasicBlock::iterator &nmi,
116 bool rescheduleKillAboveMI(MachineBasicBlock::iterator &mi,
117 MachineBasicBlock::iterator &nmi,
120 bool tryInstructionTransform(MachineBasicBlock::iterator &mi,
121 MachineBasicBlock::iterator &nmi,
122 unsigned SrcIdx, unsigned DstIdx,
125 void scanUses(unsigned DstReg);
127 void processCopy(MachineInstr *MI);
129 typedef SmallVector<std::pair<unsigned, unsigned>, 4> TiedPairList;
130 typedef SmallDenseMap<unsigned, TiedPairList> TiedOperandMap;
131 bool collectTiedOperands(MachineInstr *MI, TiedOperandMap&);
132 void processTiedPairs(MachineInstr *MI, TiedPairList&, unsigned &Dist);
133 void eliminateRegSequence(MachineBasicBlock::iterator&);
136 static char ID; // Pass identification, replacement for typeid
137 TwoAddressInstructionPass() : MachineFunctionPass(ID) {
138 initializeTwoAddressInstructionPassPass(*PassRegistry::getPassRegistry());
141 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
142 AU.setPreservesCFG();
143 AU.addRequired<AliasAnalysis>();
144 AU.addPreserved<LiveVariables>();
145 AU.addPreserved<SlotIndexes>();
146 AU.addPreserved<LiveIntervals>();
147 AU.addPreservedID(MachineLoopInfoID);
148 AU.addPreservedID(MachineDominatorsID);
149 MachineFunctionPass::getAnalysisUsage(AU);
152 /// runOnMachineFunction - Pass entry point.
153 bool runOnMachineFunction(MachineFunction&);
155 } // end anonymous namespace
157 char TwoAddressInstructionPass::ID = 0;
158 INITIALIZE_PASS_BEGIN(TwoAddressInstructionPass, "twoaddressinstruction",
159 "Two-Address instruction pass", false, false)
160 INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
161 INITIALIZE_PASS_END(TwoAddressInstructionPass, "twoaddressinstruction",
162 "Two-Address instruction pass", false, false)
164 char &llvm::TwoAddressInstructionPassID = TwoAddressInstructionPass::ID;
166 /// sink3AddrInstruction - A two-address instruction has been converted to a
167 /// three-address instruction to avoid clobbering a register. Try to sink it
168 /// past the instruction that would kill the above mentioned register to reduce
169 /// register pressure.
170 bool TwoAddressInstructionPass::
171 sink3AddrInstruction(MachineInstr *MI, unsigned SavedReg,
172 MachineBasicBlock::iterator OldPos) {
173 // FIXME: Shouldn't we be trying to do this before we three-addressify the
174 // instruction? After this transformation is done, we no longer need
175 // the instruction to be in three-address form.
177 // Check if it's safe to move this instruction.
178 bool SeenStore = true; // Be conservative.
179 if (!MI->isSafeToMove(TII, AA, SeenStore))
183 SmallSet<unsigned, 4> UseRegs;
185 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
186 const MachineOperand &MO = MI->getOperand(i);
189 unsigned MOReg = MO.getReg();
192 if (MO.isUse() && MOReg != SavedReg)
193 UseRegs.insert(MO.getReg());
197 // Don't try to move it if it implicitly defines a register.
200 // For now, don't move any instructions that define multiple registers.
202 DefReg = MO.getReg();
205 // Find the instruction that kills SavedReg.
206 MachineInstr *KillMI = NULL;
207 for (MachineRegisterInfo::use_nodbg_iterator
208 UI = MRI->use_nodbg_begin(SavedReg),
209 UE = MRI->use_nodbg_end(); UI != UE; ++UI) {
210 MachineOperand &UseMO = UI.getOperand();
213 KillMI = UseMO.getParent();
217 // If we find the instruction that kills SavedReg, and it is in an
218 // appropriate location, we can try to sink the current instruction
220 if (!KillMI || KillMI->getParent() != MBB || KillMI == MI ||
221 KillMI == OldPos || KillMI->isTerminator())
224 // If any of the definitions are used by another instruction between the
225 // position and the kill use, then it's not safe to sink it.
227 // FIXME: This can be sped up if there is an easy way to query whether an
228 // instruction is before or after another instruction. Then we can use
229 // MachineRegisterInfo def / use instead.
230 MachineOperand *KillMO = NULL;
231 MachineBasicBlock::iterator KillPos = KillMI;
234 unsigned NumVisited = 0;
235 for (MachineBasicBlock::iterator I = llvm::next(OldPos); I != KillPos; ++I) {
236 MachineInstr *OtherMI = I;
237 // DBG_VALUE cannot be counted against the limit.
238 if (OtherMI->isDebugValue())
240 if (NumVisited > 30) // FIXME: Arbitrary limit to reduce compile time cost.
243 for (unsigned i = 0, e = OtherMI->getNumOperands(); i != e; ++i) {
244 MachineOperand &MO = OtherMI->getOperand(i);
247 unsigned MOReg = MO.getReg();
254 if (OtherMI == KillMI && MOReg == SavedReg)
255 // Save the operand that kills the register. We want to unset the kill
256 // marker if we can sink MI past it.
258 else if (UseRegs.count(MOReg))
259 // One of the uses is killed before the destination.
264 assert(KillMO && "Didn't find kill");
266 // Update kill and LV information.
267 KillMO->setIsKill(false);
268 KillMO = MI->findRegisterUseOperand(SavedReg, false, TRI);
269 KillMO->setIsKill(true);
272 LV->replaceKillInstruction(SavedReg, KillMI, MI);
274 // Move instruction to its destination.
276 MBB->insert(KillPos, MI);
285 /// noUseAfterLastDef - Return true if there are no intervening uses between the
286 /// last instruction in the MBB that defines the specified register and the
287 /// two-address instruction which is being processed. It also returns the last
288 /// def location by reference
289 bool TwoAddressInstructionPass::noUseAfterLastDef(unsigned Reg, unsigned Dist,
292 unsigned LastUse = Dist;
293 for (MachineRegisterInfo::reg_iterator I = MRI->reg_begin(Reg),
294 E = MRI->reg_end(); I != E; ++I) {
295 MachineOperand &MO = I.getOperand();
296 MachineInstr *MI = MO.getParent();
297 if (MI->getParent() != MBB || MI->isDebugValue())
299 DenseMap<MachineInstr*, unsigned>::iterator DI = DistanceMap.find(MI);
300 if (DI == DistanceMap.end())
302 if (MO.isUse() && DI->second < LastUse)
303 LastUse = DI->second;
304 if (MO.isDef() && DI->second > LastDef)
305 LastDef = DI->second;
308 return !(LastUse > LastDef && LastUse < Dist);
311 /// isCopyToReg - Return true if the specified MI is a copy instruction or
312 /// a extract_subreg instruction. It also returns the source and destination
313 /// registers and whether they are physical registers by reference.
314 static bool isCopyToReg(MachineInstr &MI, const TargetInstrInfo *TII,
315 unsigned &SrcReg, unsigned &DstReg,
316 bool &IsSrcPhys, bool &IsDstPhys) {
320 DstReg = MI.getOperand(0).getReg();
321 SrcReg = MI.getOperand(1).getReg();
322 } else if (MI.isInsertSubreg() || MI.isSubregToReg()) {
323 DstReg = MI.getOperand(0).getReg();
324 SrcReg = MI.getOperand(2).getReg();
328 IsSrcPhys = TargetRegisterInfo::isPhysicalRegister(SrcReg);
329 IsDstPhys = TargetRegisterInfo::isPhysicalRegister(DstReg);
333 /// isPLainlyKilled - Test if the given register value, which is used by the
334 // given instruction, is killed by the given instruction.
335 static bool isPlainlyKilled(MachineInstr *MI, unsigned Reg,
336 LiveIntervals *LIS) {
337 if (LIS && TargetRegisterInfo::isVirtualRegister(Reg) &&
338 !LIS->isNotInMIMap(MI)) {
339 // FIXME: Sometimes tryInstructionTransform() will add instructions and
340 // test whether they can be folded before keeping them. In this case it
341 // sets a kill before recursively calling tryInstructionTransform() again.
342 // If there is no interval available, we assume that this instruction is
343 // one of those. A kill flag is manually inserted on the operand so the
344 // check below will handle it.
345 LiveInterval &LI = LIS->getInterval(Reg);
346 // This is to match the kill flag version where undefs don't have kill
348 if (!LI.hasAtLeastOneValue())
351 SlotIndex useIdx = LIS->getInstructionIndex(MI);
352 LiveInterval::const_iterator I = LI.find(useIdx);
353 assert(I != LI.end() && "Reg must be live-in to use.");
354 return SlotIndex::isSameInstr(I->end, useIdx);
357 return MI->killsRegister(Reg);
360 /// isKilled - Test if the given register value, which is used by the given
361 /// instruction, is killed by the given instruction. This looks through
362 /// coalescable copies to see if the original value is potentially not killed.
364 /// For example, in this code:
366 /// %reg1034 = copy %reg1024
367 /// %reg1035 = copy %reg1025<kill>
368 /// %reg1036 = add %reg1034<kill>, %reg1035<kill>
370 /// %reg1034 is not considered to be killed, since it is copied from a
371 /// register which is not killed. Treating it as not killed lets the
372 /// normal heuristics commute the (two-address) add, which lets
373 /// coalescing eliminate the extra copy.
375 static bool isKilled(MachineInstr &MI, unsigned Reg,
376 const MachineRegisterInfo *MRI,
377 const TargetInstrInfo *TII,
378 LiveIntervals *LIS) {
379 MachineInstr *DefMI = &MI;
381 if (!isPlainlyKilled(DefMI, Reg, LIS))
383 if (TargetRegisterInfo::isPhysicalRegister(Reg))
385 MachineRegisterInfo::def_iterator Begin = MRI->def_begin(Reg);
386 // If there are multiple defs, we can't do a simple analysis, so just
387 // go with what the kill flag says.
388 if (llvm::next(Begin) != MRI->def_end())
391 bool IsSrcPhys, IsDstPhys;
392 unsigned SrcReg, DstReg;
393 // If the def is something other than a copy, then it isn't going to
394 // be coalesced, so follow the kill flag.
395 if (!isCopyToReg(*DefMI, TII, SrcReg, DstReg, IsSrcPhys, IsDstPhys))
401 /// isTwoAddrUse - Return true if the specified MI uses the specified register
402 /// as a two-address use. If so, return the destination register by reference.
403 static bool isTwoAddrUse(MachineInstr &MI, unsigned Reg, unsigned &DstReg) {
404 const MCInstrDesc &MCID = MI.getDesc();
405 unsigned NumOps = MI.isInlineAsm()
406 ? MI.getNumOperands() : MCID.getNumOperands();
407 for (unsigned i = 0; i != NumOps; ++i) {
408 const MachineOperand &MO = MI.getOperand(i);
409 if (!MO.isReg() || !MO.isUse() || MO.getReg() != Reg)
412 if (MI.isRegTiedToDefOperand(i, &ti)) {
413 DstReg = MI.getOperand(ti).getReg();
420 /// findOnlyInterestingUse - Given a register, if has a single in-basic block
421 /// use, return the use instruction if it's a copy or a two-address use.
423 MachineInstr *findOnlyInterestingUse(unsigned Reg, MachineBasicBlock *MBB,
424 MachineRegisterInfo *MRI,
425 const TargetInstrInfo *TII,
427 unsigned &DstReg, bool &IsDstPhys) {
428 if (!MRI->hasOneNonDBGUse(Reg))
429 // None or more than one use.
431 MachineInstr &UseMI = *MRI->use_nodbg_begin(Reg);
432 if (UseMI.getParent() != MBB)
436 if (isCopyToReg(UseMI, TII, SrcReg, DstReg, IsSrcPhys, IsDstPhys)) {
441 if (isTwoAddrUse(UseMI, Reg, DstReg)) {
442 IsDstPhys = TargetRegisterInfo::isPhysicalRegister(DstReg);
448 /// getMappedReg - Return the physical register the specified virtual register
449 /// might be mapped to.
451 getMappedReg(unsigned Reg, DenseMap<unsigned, unsigned> &RegMap) {
452 while (TargetRegisterInfo::isVirtualRegister(Reg)) {
453 DenseMap<unsigned, unsigned>::iterator SI = RegMap.find(Reg);
454 if (SI == RegMap.end())
458 if (TargetRegisterInfo::isPhysicalRegister(Reg))
463 /// regsAreCompatible - Return true if the two registers are equal or aliased.
466 regsAreCompatible(unsigned RegA, unsigned RegB, const TargetRegisterInfo *TRI) {
471 return TRI->regsOverlap(RegA, RegB);
475 /// isProfitableToCommute - Return true if it's potentially profitable to commute
476 /// the two-address instruction that's being processed.
478 TwoAddressInstructionPass::
479 isProfitableToCommute(unsigned regA, unsigned regB, unsigned regC,
480 MachineInstr *MI, unsigned Dist) {
481 if (OptLevel == CodeGenOpt::None)
484 // Determine if it's profitable to commute this two address instruction. In
485 // general, we want no uses between this instruction and the definition of
486 // the two-address register.
488 // %reg1028<def> = EXTRACT_SUBREG %reg1027<kill>, 1
489 // %reg1029<def> = MOV8rr %reg1028
490 // %reg1029<def> = SHR8ri %reg1029, 7, %EFLAGS<imp-def,dead>
491 // insert => %reg1030<def> = MOV8rr %reg1028
492 // %reg1030<def> = ADD8rr %reg1028<kill>, %reg1029<kill>, %EFLAGS<imp-def,dead>
493 // In this case, it might not be possible to coalesce the second MOV8rr
494 // instruction if the first one is coalesced. So it would be profitable to
496 // %reg1028<def> = EXTRACT_SUBREG %reg1027<kill>, 1
497 // %reg1029<def> = MOV8rr %reg1028
498 // %reg1029<def> = SHR8ri %reg1029, 7, %EFLAGS<imp-def,dead>
499 // insert => %reg1030<def> = MOV8rr %reg1029
500 // %reg1030<def> = ADD8rr %reg1029<kill>, %reg1028<kill>, %EFLAGS<imp-def,dead>
502 if (!isPlainlyKilled(MI, regC, LIS))
505 // Ok, we have something like:
506 // %reg1030<def> = ADD8rr %reg1028<kill>, %reg1029<kill>, %EFLAGS<imp-def,dead>
507 // let's see if it's worth commuting it.
509 // Look for situations like this:
510 // %reg1024<def> = MOV r1
511 // %reg1025<def> = MOV r0
512 // %reg1026<def> = ADD %reg1024, %reg1025
514 // Commute the ADD to hopefully eliminate an otherwise unavoidable copy.
515 unsigned ToRegA = getMappedReg(regA, DstRegMap);
517 unsigned FromRegB = getMappedReg(regB, SrcRegMap);
518 unsigned FromRegC = getMappedReg(regC, SrcRegMap);
519 bool BComp = !FromRegB || regsAreCompatible(FromRegB, ToRegA, TRI);
520 bool CComp = !FromRegC || regsAreCompatible(FromRegC, ToRegA, TRI);
522 return !BComp && CComp;
525 // If there is a use of regC between its last def (could be livein) and this
526 // instruction, then bail.
527 unsigned LastDefC = 0;
528 if (!noUseAfterLastDef(regC, Dist, LastDefC))
531 // If there is a use of regB between its last def (could be livein) and this
532 // instruction, then go ahead and make this transformation.
533 unsigned LastDefB = 0;
534 if (!noUseAfterLastDef(regB, Dist, LastDefB))
537 // Since there are no intervening uses for both registers, then commute
538 // if the def of regC is closer. Its live interval is shorter.
539 return LastDefB && LastDefC && LastDefC > LastDefB;
542 /// commuteInstruction - Commute a two-address instruction and update the basic
543 /// block, distance map, and live variables if needed. Return true if it is
545 bool TwoAddressInstructionPass::
546 commuteInstruction(MachineBasicBlock::iterator &mi,
547 unsigned RegB, unsigned RegC, unsigned Dist) {
548 MachineInstr *MI = mi;
549 DEBUG(dbgs() << "2addr: COMMUTING : " << *MI);
550 MachineInstr *NewMI = TII->commuteInstruction(MI);
553 DEBUG(dbgs() << "2addr: COMMUTING FAILED!\n");
557 DEBUG(dbgs() << "2addr: COMMUTED TO: " << *NewMI);
558 // If the instruction changed to commute it, update livevar.
561 // Update live variables
562 LV->replaceKillInstruction(RegC, MI, NewMI);
564 LIS->ReplaceMachineInstrInMaps(MI, NewMI);
566 MBB->insert(mi, NewMI); // Insert the new inst
567 MBB->erase(mi); // Nuke the old inst.
569 DistanceMap.insert(std::make_pair(NewMI, Dist));
572 // Update source register map.
573 unsigned FromRegC = getMappedReg(RegC, SrcRegMap);
575 unsigned RegA = MI->getOperand(0).getReg();
576 SrcRegMap[RegA] = FromRegC;
582 /// isProfitableToConv3Addr - Return true if it is profitable to convert the
583 /// given 2-address instruction to a 3-address one.
585 TwoAddressInstructionPass::isProfitableToConv3Addr(unsigned RegA,unsigned RegB){
586 // Look for situations like this:
587 // %reg1024<def> = MOV r1
588 // %reg1025<def> = MOV r0
589 // %reg1026<def> = ADD %reg1024, %reg1025
591 // Turn ADD into a 3-address instruction to avoid a copy.
592 unsigned FromRegB = getMappedReg(RegB, SrcRegMap);
595 unsigned ToRegA = getMappedReg(RegA, DstRegMap);
596 return (ToRegA && !regsAreCompatible(FromRegB, ToRegA, TRI));
599 /// convertInstTo3Addr - Convert the specified two-address instruction into a
600 /// three address one. Return true if this transformation was successful.
602 TwoAddressInstructionPass::convertInstTo3Addr(MachineBasicBlock::iterator &mi,
603 MachineBasicBlock::iterator &nmi,
604 unsigned RegA, unsigned RegB,
606 // FIXME: Why does convertToThreeAddress() need an iterator reference?
607 MachineFunction::iterator MFI = MBB;
608 MachineInstr *NewMI = TII->convertToThreeAddress(MFI, mi, LV);
609 assert(MBB == MFI && "convertToThreeAddress changed iterator reference");
613 DEBUG(dbgs() << "2addr: CONVERTING 2-ADDR: " << *mi);
614 DEBUG(dbgs() << "2addr: TO 3-ADDR: " << *NewMI);
618 LIS->ReplaceMachineInstrInMaps(mi, NewMI);
620 if (NewMI->findRegisterUseOperand(RegB, false, TRI))
621 // FIXME: Temporary workaround. If the new instruction doesn't
622 // uses RegB, convertToThreeAddress must have created more
623 // then one instruction.
624 Sunk = sink3AddrInstruction(NewMI, RegB, mi);
626 MBB->erase(mi); // Nuke the old inst.
629 DistanceMap.insert(std::make_pair(NewMI, Dist));
631 nmi = llvm::next(mi);
634 // Update source and destination register maps.
635 SrcRegMap.erase(RegA);
636 DstRegMap.erase(RegB);
640 /// scanUses - Scan forward recursively for only uses, update maps if the use
641 /// is a copy or a two-address instruction.
643 TwoAddressInstructionPass::scanUses(unsigned DstReg) {
644 SmallVector<unsigned, 4> VirtRegPairs;
648 unsigned Reg = DstReg;
649 while (MachineInstr *UseMI = findOnlyInterestingUse(Reg, MBB, MRI, TII,IsCopy,
650 NewReg, IsDstPhys)) {
651 if (IsCopy && !Processed.insert(UseMI))
654 DenseMap<MachineInstr*, unsigned>::iterator DI = DistanceMap.find(UseMI);
655 if (DI != DistanceMap.end())
656 // Earlier in the same MBB.Reached via a back edge.
660 VirtRegPairs.push_back(NewReg);
663 bool isNew = SrcRegMap.insert(std::make_pair(NewReg, Reg)).second;
665 assert(SrcRegMap[NewReg] == Reg && "Can't map to two src registers!");
666 VirtRegPairs.push_back(NewReg);
670 if (!VirtRegPairs.empty()) {
671 unsigned ToReg = VirtRegPairs.back();
672 VirtRegPairs.pop_back();
673 while (!VirtRegPairs.empty()) {
674 unsigned FromReg = VirtRegPairs.back();
675 VirtRegPairs.pop_back();
676 bool isNew = DstRegMap.insert(std::make_pair(FromReg, ToReg)).second;
678 assert(DstRegMap[FromReg] == ToReg &&"Can't map to two dst registers!");
681 bool isNew = DstRegMap.insert(std::make_pair(DstReg, ToReg)).second;
683 assert(DstRegMap[DstReg] == ToReg && "Can't map to two dst registers!");
687 /// processCopy - If the specified instruction is not yet processed, process it
688 /// if it's a copy. For a copy instruction, we find the physical registers the
689 /// source and destination registers might be mapped to. These are kept in
690 /// point-to maps used to determine future optimizations. e.g.
693 /// v1026 = add v1024, v1025
695 /// If 'add' is a two-address instruction, v1024, v1026 are both potentially
696 /// coalesced to r0 (from the input side). v1025 is mapped to r1. v1026 is
697 /// potentially joined with r1 on the output side. It's worthwhile to commute
698 /// 'add' to eliminate a copy.
699 void TwoAddressInstructionPass::processCopy(MachineInstr *MI) {
700 if (Processed.count(MI))
703 bool IsSrcPhys, IsDstPhys;
704 unsigned SrcReg, DstReg;
705 if (!isCopyToReg(*MI, TII, SrcReg, DstReg, IsSrcPhys, IsDstPhys))
708 if (IsDstPhys && !IsSrcPhys)
709 DstRegMap.insert(std::make_pair(SrcReg, DstReg));
710 else if (!IsDstPhys && IsSrcPhys) {
711 bool isNew = SrcRegMap.insert(std::make_pair(DstReg, SrcReg)).second;
713 assert(SrcRegMap[DstReg] == SrcReg &&
714 "Can't map to two src physical registers!");
719 Processed.insert(MI);
723 /// rescheduleMIBelowKill - If there is one more local instruction that reads
724 /// 'Reg' and it kills 'Reg, consider moving the instruction below the kill
725 /// instruction in order to eliminate the need for the copy.
726 bool TwoAddressInstructionPass::
727 rescheduleMIBelowKill(MachineBasicBlock::iterator &mi,
728 MachineBasicBlock::iterator &nmi,
730 // Bail immediately if we don't have LV available. We use it to find kills
735 MachineInstr *MI = &*mi;
736 DenseMap<MachineInstr*, unsigned>::iterator DI = DistanceMap.find(MI);
737 if (DI == DistanceMap.end())
738 // Must be created from unfolded load. Don't waste time trying this.
741 MachineInstr *KillMI = LV->getVarInfo(Reg).findKill(MBB);
742 if (!KillMI || MI == KillMI || KillMI->isCopy() || KillMI->isCopyLike())
743 // Don't mess with copies, they may be coalesced later.
746 if (KillMI->hasUnmodeledSideEffects() || KillMI->isCall() ||
747 KillMI->isBranch() || KillMI->isTerminator())
748 // Don't move pass calls, etc.
752 if (isTwoAddrUse(*KillMI, Reg, DstReg))
755 bool SeenStore = true;
756 if (!MI->isSafeToMove(TII, AA, SeenStore))
759 if (TII->getInstrLatency(InstrItins, MI) > 1)
760 // FIXME: Needs more sophisticated heuristics.
763 SmallSet<unsigned, 2> Uses;
764 SmallSet<unsigned, 2> Kills;
765 SmallSet<unsigned, 2> Defs;
766 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
767 const MachineOperand &MO = MI->getOperand(i);
770 unsigned MOReg = MO.getReg();
777 if (MO.isKill() && MOReg != Reg)
782 // Move the copies connected to MI down as well.
783 MachineBasicBlock::iterator From = MI;
784 MachineBasicBlock::iterator To = llvm::next(From);
785 while (To->isCopy() && Defs.count(To->getOperand(1).getReg())) {
786 Defs.insert(To->getOperand(0).getReg());
790 // Check if the reschedule will not break depedencies.
791 unsigned NumVisited = 0;
792 MachineBasicBlock::iterator KillPos = KillMI;
794 for (MachineBasicBlock::iterator I = To; I != KillPos; ++I) {
795 MachineInstr *OtherMI = I;
796 // DBG_VALUE cannot be counted against the limit.
797 if (OtherMI->isDebugValue())
799 if (NumVisited > 10) // FIXME: Arbitrary limit to reduce compile time cost.
802 if (OtherMI->hasUnmodeledSideEffects() || OtherMI->isCall() ||
803 OtherMI->isBranch() || OtherMI->isTerminator())
804 // Don't move pass calls, etc.
806 for (unsigned i = 0, e = OtherMI->getNumOperands(); i != e; ++i) {
807 const MachineOperand &MO = OtherMI->getOperand(i);
810 unsigned MOReg = MO.getReg();
814 if (Uses.count(MOReg))
815 // Physical register use would be clobbered.
817 if (!MO.isDead() && Defs.count(MOReg))
818 // May clobber a physical register def.
819 // FIXME: This may be too conservative. It's ok if the instruction
820 // is sunken completely below the use.
823 if (Defs.count(MOReg))
826 ((MO.isKill() && Uses.count(MOReg)) || Kills.count(MOReg)))
827 // Don't want to extend other live ranges and update kills.
829 if (MOReg == Reg && !MO.isKill())
830 // We can't schedule across a use of the register in question.
832 // Ensure that if this is register in question, its the kill we expect.
833 assert((MOReg != Reg || OtherMI == KillMI) &&
834 "Found multiple kills of a register in a basic block");
839 // Move debug info as well.
840 while (From != MBB->begin() && llvm::prior(From)->isDebugValue())
843 // Copies following MI may have been moved as well.
845 MBB->splice(KillPos, MBB, From, To);
846 DistanceMap.erase(DI);
848 // Update live variables
849 LV->removeVirtualRegisterKilled(Reg, KillMI);
850 LV->addVirtualRegisterKilled(Reg, MI);
854 DEBUG(dbgs() << "\trescheduled below kill: " << *KillMI);
858 /// isDefTooClose - Return true if the re-scheduling will put the given
859 /// instruction too close to the defs of its register dependencies.
860 bool TwoAddressInstructionPass::isDefTooClose(unsigned Reg, unsigned Dist,
862 for (MachineRegisterInfo::def_iterator DI = MRI->def_begin(Reg),
863 DE = MRI->def_end(); DI != DE; ++DI) {
864 MachineInstr *DefMI = &*DI;
865 if (DefMI->getParent() != MBB || DefMI->isCopy() || DefMI->isCopyLike())
868 return true; // MI is defining something KillMI uses
869 DenseMap<MachineInstr*, unsigned>::iterator DDI = DistanceMap.find(DefMI);
870 if (DDI == DistanceMap.end())
871 return true; // Below MI
872 unsigned DefDist = DDI->second;
873 assert(Dist > DefDist && "Visited def already?");
874 if (TII->getInstrLatency(InstrItins, DefMI) > (Dist - DefDist))
880 /// rescheduleKillAboveMI - If there is one more local instruction that reads
881 /// 'Reg' and it kills 'Reg, consider moving the kill instruction above the
882 /// current two-address instruction in order to eliminate the need for the
884 bool TwoAddressInstructionPass::
885 rescheduleKillAboveMI(MachineBasicBlock::iterator &mi,
886 MachineBasicBlock::iterator &nmi,
888 // Bail immediately if we don't have LV available. We use it to find kills
893 MachineInstr *MI = &*mi;
894 DenseMap<MachineInstr*, unsigned>::iterator DI = DistanceMap.find(MI);
895 if (DI == DistanceMap.end())
896 // Must be created from unfolded load. Don't waste time trying this.
899 MachineInstr *KillMI = LV->getVarInfo(Reg).findKill(MBB);
900 if (!KillMI || MI == KillMI || KillMI->isCopy() || KillMI->isCopyLike())
901 // Don't mess with copies, they may be coalesced later.
905 if (isTwoAddrUse(*KillMI, Reg, DstReg))
908 bool SeenStore = true;
909 if (!KillMI->isSafeToMove(TII, AA, SeenStore))
912 SmallSet<unsigned, 2> Uses;
913 SmallSet<unsigned, 2> Kills;
914 SmallSet<unsigned, 2> Defs;
915 SmallSet<unsigned, 2> LiveDefs;
916 for (unsigned i = 0, e = KillMI->getNumOperands(); i != e; ++i) {
917 const MachineOperand &MO = KillMI->getOperand(i);
920 unsigned MOReg = MO.getReg();
924 if (isDefTooClose(MOReg, DI->second, MI))
926 if (MOReg == Reg && !MO.isKill())
929 if (MO.isKill() && MOReg != Reg)
931 } else if (TargetRegisterInfo::isPhysicalRegister(MOReg)) {
934 LiveDefs.insert(MOReg);
938 // Check if the reschedule will not break depedencies.
939 unsigned NumVisited = 0;
940 MachineBasicBlock::iterator KillPos = KillMI;
941 for (MachineBasicBlock::iterator I = mi; I != KillPos; ++I) {
942 MachineInstr *OtherMI = I;
943 // DBG_VALUE cannot be counted against the limit.
944 if (OtherMI->isDebugValue())
946 if (NumVisited > 10) // FIXME: Arbitrary limit to reduce compile time cost.
949 if (OtherMI->hasUnmodeledSideEffects() || OtherMI->isCall() ||
950 OtherMI->isBranch() || OtherMI->isTerminator())
951 // Don't move pass calls, etc.
953 SmallVector<unsigned, 2> OtherDefs;
954 for (unsigned i = 0, e = OtherMI->getNumOperands(); i != e; ++i) {
955 const MachineOperand &MO = OtherMI->getOperand(i);
958 unsigned MOReg = MO.getReg();
962 if (Defs.count(MOReg))
963 // Moving KillMI can clobber the physical register if the def has
966 if (Kills.count(MOReg))
967 // Don't want to extend other live ranges and update kills.
969 if (OtherMI != MI && MOReg == Reg && !MO.isKill())
970 // We can't schedule across a use of the register in question.
973 OtherDefs.push_back(MOReg);
977 for (unsigned i = 0, e = OtherDefs.size(); i != e; ++i) {
978 unsigned MOReg = OtherDefs[i];
979 if (Uses.count(MOReg))
981 if (TargetRegisterInfo::isPhysicalRegister(MOReg) &&
982 LiveDefs.count(MOReg))
984 // Physical register def is seen.
989 // Move the old kill above MI, don't forget to move debug info as well.
990 MachineBasicBlock::iterator InsertPos = mi;
991 while (InsertPos != MBB->begin() && llvm::prior(InsertPos)->isDebugValue())
993 MachineBasicBlock::iterator From = KillMI;
994 MachineBasicBlock::iterator To = llvm::next(From);
995 while (llvm::prior(From)->isDebugValue())
997 MBB->splice(InsertPos, MBB, From, To);
999 nmi = llvm::prior(InsertPos); // Backtrack so we process the moved instr.
1000 DistanceMap.erase(DI);
1002 // Update live variables
1003 LV->removeVirtualRegisterKilled(Reg, KillMI);
1004 LV->addVirtualRegisterKilled(Reg, MI);
1006 LIS->handleMove(KillMI);
1008 DEBUG(dbgs() << "\trescheduled kill: " << *KillMI);
1012 /// tryInstructionTransform - For the case where an instruction has a single
1013 /// pair of tied register operands, attempt some transformations that may
1014 /// either eliminate the tied operands or improve the opportunities for
1015 /// coalescing away the register copy. Returns true if no copy needs to be
1016 /// inserted to untie mi's operands (either because they were untied, or
1017 /// because mi was rescheduled, and will be visited again later).
1018 bool TwoAddressInstructionPass::
1019 tryInstructionTransform(MachineBasicBlock::iterator &mi,
1020 MachineBasicBlock::iterator &nmi,
1021 unsigned SrcIdx, unsigned DstIdx, unsigned Dist) {
1022 if (OptLevel == CodeGenOpt::None)
1025 MachineInstr &MI = *mi;
1026 unsigned regA = MI.getOperand(DstIdx).getReg();
1027 unsigned regB = MI.getOperand(SrcIdx).getReg();
1029 assert(TargetRegisterInfo::isVirtualRegister(regB) &&
1030 "cannot make instruction into two-address form");
1031 bool regBKilled = isKilled(MI, regB, MRI, TII, LIS);
1033 if (TargetRegisterInfo::isVirtualRegister(regA))
1036 // Check if it is profitable to commute the operands.
1037 unsigned SrcOp1, SrcOp2;
1039 unsigned regCIdx = ~0U;
1040 bool TryCommute = false;
1041 bool AggressiveCommute = false;
1042 if (MI.isCommutable() && MI.getNumOperands() >= 3 &&
1043 TII->findCommutedOpIndices(&MI, SrcOp1, SrcOp2)) {
1044 if (SrcIdx == SrcOp1)
1046 else if (SrcIdx == SrcOp2)
1049 if (regCIdx != ~0U) {
1050 regC = MI.getOperand(regCIdx).getReg();
1051 if (!regBKilled && isKilled(MI, regC, MRI, TII, LIS))
1052 // If C dies but B does not, swap the B and C operands.
1053 // This makes the live ranges of A and C joinable.
1055 else if (isProfitableToCommute(regA, regB, regC, &MI, Dist)) {
1057 AggressiveCommute = true;
1062 // If it's profitable to commute, try to do so.
1063 if (TryCommute && commuteInstruction(mi, regB, regC, Dist)) {
1065 if (AggressiveCommute)
1070 // If there is one more use of regB later in the same MBB, consider
1071 // re-schedule this MI below it.
1072 if (rescheduleMIBelowKill(mi, nmi, regB)) {
1077 if (MI.isConvertibleTo3Addr()) {
1078 // This instruction is potentially convertible to a true
1079 // three-address instruction. Check if it is profitable.
1080 if (!regBKilled || isProfitableToConv3Addr(regA, regB)) {
1081 // Try to convert it.
1082 if (convertInstTo3Addr(mi, nmi, regA, regB, Dist)) {
1083 ++NumConvertedTo3Addr;
1084 return true; // Done with this instruction.
1089 // If there is one more use of regB later in the same MBB, consider
1090 // re-schedule it before this MI if it's legal.
1091 if (rescheduleKillAboveMI(mi, nmi, regB)) {
1096 // If this is an instruction with a load folded into it, try unfolding
1097 // the load, e.g. avoid this:
1099 // addq (%rax), %rcx
1100 // in favor of this:
1101 // movq (%rax), %rcx
1103 // because it's preferable to schedule a load than a register copy.
1104 if (MI.mayLoad() && !regBKilled) {
1105 // Determine if a load can be unfolded.
1106 unsigned LoadRegIndex;
1108 TII->getOpcodeAfterMemoryUnfold(MI.getOpcode(),
1109 /*UnfoldLoad=*/true,
1110 /*UnfoldStore=*/false,
1113 const MCInstrDesc &UnfoldMCID = TII->get(NewOpc);
1114 if (UnfoldMCID.getNumDefs() == 1) {
1116 DEBUG(dbgs() << "2addr: UNFOLDING: " << MI);
1117 const TargetRegisterClass *RC =
1118 TRI->getAllocatableClass(
1119 TII->getRegClass(UnfoldMCID, LoadRegIndex, TRI, *MF));
1120 unsigned Reg = MRI->createVirtualRegister(RC);
1121 SmallVector<MachineInstr *, 2> NewMIs;
1122 if (!TII->unfoldMemoryOperand(*MF, &MI, Reg,
1123 /*UnfoldLoad=*/true,/*UnfoldStore=*/false,
1125 DEBUG(dbgs() << "2addr: ABANDONING UNFOLD\n");
1128 assert(NewMIs.size() == 2 &&
1129 "Unfolded a load into multiple instructions!");
1130 // The load was previously folded, so this is the only use.
1131 NewMIs[1]->addRegisterKilled(Reg, TRI);
1133 // Tentatively insert the instructions into the block so that they
1134 // look "normal" to the transformation logic.
1135 MBB->insert(mi, NewMIs[0]);
1136 MBB->insert(mi, NewMIs[1]);
1138 DEBUG(dbgs() << "2addr: NEW LOAD: " << *NewMIs[0]
1139 << "2addr: NEW INST: " << *NewMIs[1]);
1141 // Transform the instruction, now that it no longer has a load.
1142 unsigned NewDstIdx = NewMIs[1]->findRegisterDefOperandIdx(regA);
1143 unsigned NewSrcIdx = NewMIs[1]->findRegisterUseOperandIdx(regB);
1144 MachineBasicBlock::iterator NewMI = NewMIs[1];
1145 bool TransformSuccess =
1146 tryInstructionTransform(NewMI, mi, NewSrcIdx, NewDstIdx, Dist);
1147 if (TransformSuccess ||
1148 NewMIs[1]->getOperand(NewSrcIdx).isKill()) {
1149 // Success, or at least we made an improvement. Keep the unfolded
1150 // instructions and discard the original.
1152 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
1153 MachineOperand &MO = MI.getOperand(i);
1155 TargetRegisterInfo::isVirtualRegister(MO.getReg())) {
1158 if (NewMIs[0]->killsRegister(MO.getReg()))
1159 LV->replaceKillInstruction(MO.getReg(), &MI, NewMIs[0]);
1161 assert(NewMIs[1]->killsRegister(MO.getReg()) &&
1162 "Kill missing after load unfold!");
1163 LV->replaceKillInstruction(MO.getReg(), &MI, NewMIs[1]);
1166 } else if (LV->removeVirtualRegisterDead(MO.getReg(), &MI)) {
1167 if (NewMIs[1]->registerDefIsDead(MO.getReg()))
1168 LV->addVirtualRegisterDead(MO.getReg(), NewMIs[1]);
1170 assert(NewMIs[0]->registerDefIsDead(MO.getReg()) &&
1171 "Dead flag missing after load unfold!");
1172 LV->addVirtualRegisterDead(MO.getReg(), NewMIs[0]);
1177 LV->addVirtualRegisterKilled(Reg, NewMIs[1]);
1180 SmallVector<unsigned, 4> OrigRegs;
1182 for (MachineInstr::const_mop_iterator MOI = MI.operands_begin(),
1183 MOE = MI.operands_end(); MOI != MOE; ++MOI) {
1185 OrigRegs.push_back(MOI->getReg());
1189 MI.eraseFromParent();
1191 // Update LiveIntervals.
1193 MachineBasicBlock::iterator Begin(NewMIs[0]);
1194 MachineBasicBlock::iterator End(NewMIs[1]);
1195 LIS->repairIntervalsInRange(MBB, Begin, End, OrigRegs);
1199 if (TransformSuccess)
1202 // Transforming didn't eliminate the tie and didn't lead to an
1203 // improvement. Clean up the unfolded instructions and keep the
1205 DEBUG(dbgs() << "2addr: ABANDONING UNFOLD\n");
1206 NewMIs[0]->eraseFromParent();
1207 NewMIs[1]->eraseFromParent();
1216 // Collect tied operands of MI that need to be handled.
1217 // Rewrite trivial cases immediately.
1218 // Return true if any tied operands where found, including the trivial ones.
1219 bool TwoAddressInstructionPass::
1220 collectTiedOperands(MachineInstr *MI, TiedOperandMap &TiedOperands) {
1221 const MCInstrDesc &MCID = MI->getDesc();
1222 bool AnyOps = false;
1223 unsigned NumOps = MI->getNumOperands();
1225 for (unsigned SrcIdx = 0; SrcIdx < NumOps; ++SrcIdx) {
1226 unsigned DstIdx = 0;
1227 if (!MI->isRegTiedToDefOperand(SrcIdx, &DstIdx))
1230 MachineOperand &SrcMO = MI->getOperand(SrcIdx);
1231 MachineOperand &DstMO = MI->getOperand(DstIdx);
1232 unsigned SrcReg = SrcMO.getReg();
1233 unsigned DstReg = DstMO.getReg();
1234 // Tied constraint already satisfied?
1235 if (SrcReg == DstReg)
1238 assert(SrcReg && SrcMO.isUse() && "two address instruction invalid");
1240 // Deal with <undef> uses immediately - simply rewrite the src operand.
1241 if (SrcMO.isUndef()) {
1242 // Constrain the DstReg register class if required.
1243 if (TargetRegisterInfo::isVirtualRegister(DstReg))
1244 if (const TargetRegisterClass *RC = TII->getRegClass(MCID, SrcIdx,
1246 MRI->constrainRegClass(DstReg, RC);
1247 SrcMO.setReg(DstReg);
1248 DEBUG(dbgs() << "\t\trewrite undef:\t" << *MI);
1251 TiedOperands[SrcReg].push_back(std::make_pair(SrcIdx, DstIdx));
1256 // Process a list of tied MI operands that all use the same source register.
1257 // The tied pairs are of the form (SrcIdx, DstIdx).
1259 TwoAddressInstructionPass::processTiedPairs(MachineInstr *MI,
1260 TiedPairList &TiedPairs,
1262 bool IsEarlyClobber = false;
1263 for (unsigned tpi = 0, tpe = TiedPairs.size(); tpi != tpe; ++tpi) {
1264 const MachineOperand &DstMO = MI->getOperand(TiedPairs[tpi].second);
1265 IsEarlyClobber |= DstMO.isEarlyClobber();
1268 bool RemovedKillFlag = false;
1269 bool AllUsesCopied = true;
1270 unsigned LastCopiedReg = 0;
1271 SlotIndex LastCopyIdx;
1273 for (unsigned tpi = 0, tpe = TiedPairs.size(); tpi != tpe; ++tpi) {
1274 unsigned SrcIdx = TiedPairs[tpi].first;
1275 unsigned DstIdx = TiedPairs[tpi].second;
1277 const MachineOperand &DstMO = MI->getOperand(DstIdx);
1278 unsigned RegA = DstMO.getReg();
1280 // Grab RegB from the instruction because it may have changed if the
1281 // instruction was commuted.
1282 RegB = MI->getOperand(SrcIdx).getReg();
1285 // The register is tied to multiple destinations (or else we would
1286 // not have continued this far), but this use of the register
1287 // already matches the tied destination. Leave it.
1288 AllUsesCopied = false;
1291 LastCopiedReg = RegA;
1293 assert(TargetRegisterInfo::isVirtualRegister(RegB) &&
1294 "cannot make instruction into two-address form");
1297 // First, verify that we don't have a use of "a" in the instruction
1298 // (a = b + a for example) because our transformation will not
1299 // work. This should never occur because we are in SSA form.
1300 for (unsigned i = 0; i != MI->getNumOperands(); ++i)
1301 assert(i == DstIdx ||
1302 !MI->getOperand(i).isReg() ||
1303 MI->getOperand(i).getReg() != RegA);
1307 BuildMI(*MI->getParent(), MI, MI->getDebugLoc(),
1308 TII->get(TargetOpcode::COPY), RegA).addReg(RegB);
1310 // Update DistanceMap.
1311 MachineBasicBlock::iterator PrevMI = MI;
1313 DistanceMap.insert(std::make_pair(PrevMI, Dist));
1314 DistanceMap[MI] = ++Dist;
1317 LastCopyIdx = LIS->InsertMachineInstrInMaps(PrevMI).getRegSlot();
1319 if (TargetRegisterInfo::isVirtualRegister(RegA)) {
1320 LiveInterval &LI = LIS->getInterval(RegA);
1321 VNInfo *VNI = LI.getNextValue(LastCopyIdx, LIS->getVNInfoAllocator());
1323 LIS->getInstructionIndex(MI).getRegSlot(IsEarlyClobber);
1324 LI.addRange(LiveRange(LastCopyIdx, endIdx, VNI));
1328 DEBUG(dbgs() << "\t\tprepend:\t" << *PrevMI);
1330 MachineOperand &MO = MI->getOperand(SrcIdx);
1331 assert(MO.isReg() && MO.getReg() == RegB && MO.isUse() &&
1332 "inconsistent operand info for 2-reg pass");
1334 MO.setIsKill(false);
1335 RemovedKillFlag = true;
1338 // Make sure regA is a legal regclass for the SrcIdx operand.
1339 if (TargetRegisterInfo::isVirtualRegister(RegA) &&
1340 TargetRegisterInfo::isVirtualRegister(RegB))
1341 MRI->constrainRegClass(RegA, MRI->getRegClass(RegB));
1345 // Propagate SrcRegMap.
1346 SrcRegMap[RegA] = RegB;
1350 if (AllUsesCopied) {
1351 if (!IsEarlyClobber) {
1352 // Replace other (un-tied) uses of regB with LastCopiedReg.
1353 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
1354 MachineOperand &MO = MI->getOperand(i);
1355 if (MO.isReg() && MO.getReg() == RegB && MO.isUse()) {
1357 MO.setIsKill(false);
1358 RemovedKillFlag = true;
1360 MO.setReg(LastCopiedReg);
1365 // Update live variables for regB.
1366 if (RemovedKillFlag && LV && LV->getVarInfo(RegB).removeKill(MI)) {
1367 MachineBasicBlock::iterator PrevMI = MI;
1369 LV->addVirtualRegisterKilled(RegB, PrevMI);
1372 // Update LiveIntervals.
1374 LiveInterval &LI = LIS->getInterval(RegB);
1375 SlotIndex MIIdx = LIS->getInstructionIndex(MI);
1376 LiveInterval::const_iterator I = LI.find(MIIdx);
1377 assert(I != LI.end() && "RegB must be live-in to use.");
1379 SlotIndex UseIdx = MIIdx.getRegSlot(IsEarlyClobber);
1380 if (I->end == UseIdx)
1381 LI.removeRange(LastCopyIdx, UseIdx);
1384 } else if (RemovedKillFlag) {
1385 // Some tied uses of regB matched their destination registers, so
1386 // regB is still used in this instruction, but a kill flag was
1387 // removed from a different tied use of regB, so now we need to add
1388 // a kill flag to one of the remaining uses of regB.
1389 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
1390 MachineOperand &MO = MI->getOperand(i);
1391 if (MO.isReg() && MO.getReg() == RegB && MO.isUse()) {
1399 /// runOnMachineFunction - Reduce two-address instructions to two operands.
1401 bool TwoAddressInstructionPass::runOnMachineFunction(MachineFunction &Func) {
1403 const TargetMachine &TM = MF->getTarget();
1404 MRI = &MF->getRegInfo();
1405 TII = TM.getInstrInfo();
1406 TRI = TM.getRegisterInfo();
1407 InstrItins = TM.getInstrItineraryData();
1408 LV = getAnalysisIfAvailable<LiveVariables>();
1409 LIS = getAnalysisIfAvailable<LiveIntervals>();
1410 AA = &getAnalysis<AliasAnalysis>();
1411 OptLevel = TM.getOptLevel();
1413 bool MadeChange = false;
1415 DEBUG(dbgs() << "********** REWRITING TWO-ADDR INSTRS **********\n");
1416 DEBUG(dbgs() << "********** Function: "
1417 << MF->getName() << '\n');
1419 // This pass takes the function out of SSA form.
1422 TiedOperandMap TiedOperands;
1423 for (MachineFunction::iterator MBBI = MF->begin(), MBBE = MF->end();
1424 MBBI != MBBE; ++MBBI) {
1427 DistanceMap.clear();
1431 for (MachineBasicBlock::iterator mi = MBB->begin(), me = MBB->end();
1433 MachineBasicBlock::iterator nmi = llvm::next(mi);
1434 if (mi->isDebugValue()) {
1439 // Expand REG_SEQUENCE instructions. This will position mi at the first
1440 // expanded instruction.
1441 if (mi->isRegSequence())
1442 eliminateRegSequence(mi);
1444 DistanceMap.insert(std::make_pair(mi, ++Dist));
1448 // First scan through all the tied register uses in this instruction
1449 // and record a list of pairs of tied operands for each register.
1450 if (!collectTiedOperands(mi, TiedOperands)) {
1455 ++NumTwoAddressInstrs;
1457 DEBUG(dbgs() << '\t' << *mi);
1459 // If the instruction has a single pair of tied operands, try some
1460 // transformations that may either eliminate the tied operands or
1461 // improve the opportunities for coalescing away the register copy.
1462 if (TiedOperands.size() == 1) {
1463 SmallVector<std::pair<unsigned, unsigned>, 4> &TiedPairs
1464 = TiedOperands.begin()->second;
1465 if (TiedPairs.size() == 1) {
1466 unsigned SrcIdx = TiedPairs[0].first;
1467 unsigned DstIdx = TiedPairs[0].second;
1468 unsigned SrcReg = mi->getOperand(SrcIdx).getReg();
1469 unsigned DstReg = mi->getOperand(DstIdx).getReg();
1470 if (SrcReg != DstReg &&
1471 tryInstructionTransform(mi, nmi, SrcIdx, DstIdx, Dist)) {
1472 // The tied operands have been eliminated or shifted further down the
1473 // block to ease elimination. Continue processing with 'nmi'.
1474 TiedOperands.clear();
1481 // Now iterate over the information collected above.
1482 for (TiedOperandMap::iterator OI = TiedOperands.begin(),
1483 OE = TiedOperands.end(); OI != OE; ++OI) {
1484 processTiedPairs(mi, OI->second, Dist);
1485 DEBUG(dbgs() << "\t\trewrite to:\t" << *mi);
1488 // Rewrite INSERT_SUBREG as COPY now that we no longer need SSA form.
1489 if (mi->isInsertSubreg()) {
1490 // From %reg = INSERT_SUBREG %reg, %subreg, subidx
1491 // To %reg:subidx = COPY %subreg
1492 unsigned SubIdx = mi->getOperand(3).getImm();
1493 mi->RemoveOperand(3);
1494 assert(mi->getOperand(0).getSubReg() == 0 && "Unexpected subreg idx");
1495 mi->getOperand(0).setSubReg(SubIdx);
1496 mi->getOperand(0).setIsUndef(mi->getOperand(1).isUndef());
1497 mi->RemoveOperand(1);
1498 mi->setDesc(TII->get(TargetOpcode::COPY));
1499 DEBUG(dbgs() << "\t\tconvert to:\t" << *mi);
1502 // Clear TiedOperands here instead of at the top of the loop
1503 // since most instructions do not have tied operands.
1504 TiedOperands.clear();
1510 MF->verify(this, "After two-address instruction pass");
1515 /// Eliminate a REG_SEQUENCE instruction as part of the de-ssa process.
1517 /// The instruction is turned into a sequence of sub-register copies:
1519 /// %dst = REG_SEQUENCE %v1, ssub0, %v2, ssub1
1523 /// %dst:ssub0<def,undef> = COPY %v1
1524 /// %dst:ssub1<def> = COPY %v2
1526 void TwoAddressInstructionPass::
1527 eliminateRegSequence(MachineBasicBlock::iterator &MBBI) {
1528 MachineInstr *MI = MBBI;
1529 unsigned DstReg = MI->getOperand(0).getReg();
1530 if (MI->getOperand(0).getSubReg() ||
1531 TargetRegisterInfo::isPhysicalRegister(DstReg) ||
1532 !(MI->getNumOperands() & 1)) {
1533 DEBUG(dbgs() << "Illegal REG_SEQUENCE instruction:" << *MI);
1534 llvm_unreachable(0);
1537 SmallVector<unsigned, 4> OrigRegs;
1539 OrigRegs.push_back(MI->getOperand(0).getReg());
1540 for (unsigned i = 1, e = MI->getNumOperands(); i < e; i += 2)
1541 OrigRegs.push_back(MI->getOperand(i).getReg());
1544 bool DefEmitted = false;
1545 for (unsigned i = 1, e = MI->getNumOperands(); i < e; i += 2) {
1546 MachineOperand &UseMO = MI->getOperand(i);
1547 unsigned SrcReg = UseMO.getReg();
1548 unsigned SubIdx = MI->getOperand(i+1).getImm();
1549 // Nothing needs to be inserted for <undef> operands.
1550 if (UseMO.isUndef())
1553 // Defer any kill flag to the last operand using SrcReg. Otherwise, we
1554 // might insert a COPY that uses SrcReg after is was killed.
1555 bool isKill = UseMO.isKill();
1557 for (unsigned j = i + 2; j < e; j += 2)
1558 if (MI->getOperand(j).getReg() == SrcReg) {
1559 MI->getOperand(j).setIsKill();
1560 UseMO.setIsKill(false);
1565 // Insert the sub-register copy.
1566 MachineInstr *CopyMI = BuildMI(*MI->getParent(), MI, MI->getDebugLoc(),
1567 TII->get(TargetOpcode::COPY))
1568 .addReg(DstReg, RegState::Define, SubIdx)
1571 // The first def needs an <undef> flag because there is no live register
1574 CopyMI->getOperand(0).setIsUndef(true);
1575 // Return an iterator pointing to the first inserted instr.
1580 // Update LiveVariables' kill info.
1581 if (LV && isKill && !TargetRegisterInfo::isPhysicalRegister(SrcReg))
1582 LV->replaceKillInstruction(SrcReg, MI, CopyMI);
1584 DEBUG(dbgs() << "Inserted: " << *CopyMI);
1587 MachineBasicBlock::iterator EndMBBI =
1588 llvm::next(MachineBasicBlock::iterator(MI));
1591 DEBUG(dbgs() << "Turned: " << *MI << " into an IMPLICIT_DEF");
1592 MI->setDesc(TII->get(TargetOpcode::IMPLICIT_DEF));
1593 for (int j = MI->getNumOperands() - 1, ee = 0; j > ee; --j)
1594 MI->RemoveOperand(j);
1596 DEBUG(dbgs() << "Eliminated: " << *MI);
1597 MI->eraseFromParent();
1600 // Udpate LiveIntervals.
1602 LIS->repairIntervalsInRange(MBB, MBBI, EndMBBI, OrigRegs);