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/Function.h"
33 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
34 #include "llvm/CodeGen/LiveVariables.h"
35 #include "llvm/CodeGen/MachineFunctionPass.h"
36 #include "llvm/CodeGen/MachineInstr.h"
37 #include "llvm/CodeGen/MachineInstrBuilder.h"
38 #include "llvm/CodeGen/MachineRegisterInfo.h"
39 #include "llvm/Analysis/AliasAnalysis.h"
40 #include "llvm/MC/MCInstrItineraries.h"
41 #include "llvm/Target/TargetRegisterInfo.h"
42 #include "llvm/Target/TargetInstrInfo.h"
43 #include "llvm/Target/TargetMachine.h"
44 #include "llvm/Target/TargetOptions.h"
45 #include "llvm/Support/Debug.h"
46 #include "llvm/Support/ErrorHandling.h"
47 #include "llvm/ADT/BitVector.h"
48 #include "llvm/ADT/DenseMap.h"
49 #include "llvm/ADT/SmallSet.h"
50 #include "llvm/ADT/Statistic.h"
51 #include "llvm/ADT/STLExtras.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;
73 CodeGenOpt::Level OptLevel;
75 // DistanceMap - Keep track the distance of a MI from the start of the
76 // current basic block.
77 DenseMap<MachineInstr*, unsigned> DistanceMap;
79 // SrcRegMap - A map from virtual registers to physical registers which
80 // are likely targets to be coalesced to due to copies from physical
81 // registers to virtual registers. e.g. v1024 = move r0.
82 DenseMap<unsigned, unsigned> SrcRegMap;
84 // DstRegMap - A map from virtual registers to physical registers which
85 // are likely targets to be coalesced to due to copies to physical
86 // registers from virtual registers. e.g. r1 = move v1024.
87 DenseMap<unsigned, unsigned> DstRegMap;
89 /// RegSequences - Keep track the list of REG_SEQUENCE instructions seen
90 /// during the initial walk of the machine function.
91 SmallVector<MachineInstr*, 16> RegSequences;
93 bool Sink3AddrInstruction(MachineBasicBlock *MBB, MachineInstr *MI,
95 MachineBasicBlock::iterator OldPos);
97 bool NoUseAfterLastDef(unsigned Reg, MachineBasicBlock *MBB, unsigned Dist,
100 bool isProfitableToCommute(unsigned regA, unsigned regB, unsigned regC,
101 MachineInstr *MI, MachineBasicBlock *MBB,
104 bool CommuteInstruction(MachineBasicBlock::iterator &mi,
105 MachineFunction::iterator &mbbi,
106 unsigned RegB, unsigned RegC, unsigned Dist);
108 bool isProfitableToConv3Addr(unsigned RegA, unsigned RegB);
110 bool ConvertInstTo3Addr(MachineBasicBlock::iterator &mi,
111 MachineBasicBlock::iterator &nmi,
112 MachineFunction::iterator &mbbi,
113 unsigned RegA, unsigned RegB, unsigned Dist);
115 bool isDefTooClose(unsigned Reg, unsigned Dist,
116 MachineInstr *MI, MachineBasicBlock *MBB);
118 bool RescheduleMIBelowKill(MachineBasicBlock *MBB,
119 MachineBasicBlock::iterator &mi,
120 MachineBasicBlock::iterator &nmi,
122 bool RescheduleKillAboveMI(MachineBasicBlock *MBB,
123 MachineBasicBlock::iterator &mi,
124 MachineBasicBlock::iterator &nmi,
127 bool TryInstructionTransform(MachineBasicBlock::iterator &mi,
128 MachineBasicBlock::iterator &nmi,
129 MachineFunction::iterator &mbbi,
130 unsigned SrcIdx, unsigned DstIdx,
132 SmallPtrSet<MachineInstr*, 8> &Processed);
134 void ScanUses(unsigned DstReg, MachineBasicBlock *MBB,
135 SmallPtrSet<MachineInstr*, 8> &Processed);
137 void ProcessCopy(MachineInstr *MI, MachineBasicBlock *MBB,
138 SmallPtrSet<MachineInstr*, 8> &Processed);
140 typedef SmallVector<std::pair<unsigned, unsigned>, 4> TiedPairList;
141 typedef SmallDenseMap<unsigned, TiedPairList> TiedOperandMap;
142 bool collectTiedOperands(MachineInstr *MI, TiedOperandMap&);
143 void processTiedPairs(MachineInstr *MI, TiedPairList&, unsigned &Dist);
145 void CoalesceExtSubRegs(SmallVector<unsigned,4> &Srcs, unsigned DstReg);
147 /// EliminateRegSequences - Eliminate REG_SEQUENCE instructions as part
148 /// of the de-ssa process. This replaces sources of REG_SEQUENCE as
149 /// sub-register references of the register defined by REG_SEQUENCE.
150 bool EliminateRegSequences();
153 static char ID; // Pass identification, replacement for typeid
154 TwoAddressInstructionPass() : MachineFunctionPass(ID) {
155 initializeTwoAddressInstructionPassPass(*PassRegistry::getPassRegistry());
158 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
159 AU.setPreservesCFG();
160 AU.addRequired<AliasAnalysis>();
161 AU.addPreserved<LiveVariables>();
162 AU.addPreserved<SlotIndexes>();
163 AU.addPreserved<LiveIntervals>();
164 AU.addPreservedID(MachineLoopInfoID);
165 AU.addPreservedID(MachineDominatorsID);
166 MachineFunctionPass::getAnalysisUsage(AU);
169 /// runOnMachineFunction - Pass entry point.
170 bool runOnMachineFunction(MachineFunction&);
174 char TwoAddressInstructionPass::ID = 0;
175 INITIALIZE_PASS_BEGIN(TwoAddressInstructionPass, "twoaddressinstruction",
176 "Two-Address instruction pass", false, false)
177 INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
178 INITIALIZE_PASS_END(TwoAddressInstructionPass, "twoaddressinstruction",
179 "Two-Address instruction pass", false, false)
181 char &llvm::TwoAddressInstructionPassID = TwoAddressInstructionPass::ID;
183 /// Sink3AddrInstruction - A two-address instruction has been converted to a
184 /// three-address instruction to avoid clobbering a register. Try to sink it
185 /// past the instruction that would kill the above mentioned register to reduce
186 /// register pressure.
187 bool TwoAddressInstructionPass::Sink3AddrInstruction(MachineBasicBlock *MBB,
188 MachineInstr *MI, unsigned SavedReg,
189 MachineBasicBlock::iterator OldPos) {
190 // FIXME: Shouldn't we be trying to do this before we three-addressify the
191 // instruction? After this transformation is done, we no longer need
192 // the instruction to be in three-address form.
194 // Check if it's safe to move this instruction.
195 bool SeenStore = true; // Be conservative.
196 if (!MI->isSafeToMove(TII, AA, SeenStore))
200 SmallSet<unsigned, 4> UseRegs;
202 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
203 const MachineOperand &MO = MI->getOperand(i);
206 unsigned MOReg = MO.getReg();
209 if (MO.isUse() && MOReg != SavedReg)
210 UseRegs.insert(MO.getReg());
214 // Don't try to move it if it implicitly defines a register.
217 // For now, don't move any instructions that define multiple registers.
219 DefReg = MO.getReg();
222 // Find the instruction that kills SavedReg.
223 MachineInstr *KillMI = NULL;
224 for (MachineRegisterInfo::use_nodbg_iterator
225 UI = MRI->use_nodbg_begin(SavedReg),
226 UE = MRI->use_nodbg_end(); UI != UE; ++UI) {
227 MachineOperand &UseMO = UI.getOperand();
230 KillMI = UseMO.getParent();
234 // If we find the instruction that kills SavedReg, and it is in an
235 // appropriate location, we can try to sink the current instruction
237 if (!KillMI || KillMI->getParent() != MBB || KillMI == MI ||
238 KillMI == OldPos || KillMI->isTerminator())
241 // If any of the definitions are used by another instruction between the
242 // position and the kill use, then it's not safe to sink it.
244 // FIXME: This can be sped up if there is an easy way to query whether an
245 // instruction is before or after another instruction. Then we can use
246 // MachineRegisterInfo def / use instead.
247 MachineOperand *KillMO = NULL;
248 MachineBasicBlock::iterator KillPos = KillMI;
251 unsigned NumVisited = 0;
252 for (MachineBasicBlock::iterator I = llvm::next(OldPos); I != KillPos; ++I) {
253 MachineInstr *OtherMI = I;
254 // DBG_VALUE cannot be counted against the limit.
255 if (OtherMI->isDebugValue())
257 if (NumVisited > 30) // FIXME: Arbitrary limit to reduce compile time cost.
260 for (unsigned i = 0, e = OtherMI->getNumOperands(); i != e; ++i) {
261 MachineOperand &MO = OtherMI->getOperand(i);
264 unsigned MOReg = MO.getReg();
271 if (OtherMI == KillMI && MOReg == SavedReg)
272 // Save the operand that kills the register. We want to unset the kill
273 // marker if we can sink MI past it.
275 else if (UseRegs.count(MOReg))
276 // One of the uses is killed before the destination.
281 assert(KillMO && "Didn't find kill");
283 // Update kill and LV information.
284 KillMO->setIsKill(false);
285 KillMO = MI->findRegisterUseOperand(SavedReg, false, TRI);
286 KillMO->setIsKill(true);
289 LV->replaceKillInstruction(SavedReg, KillMI, MI);
291 // Move instruction to its destination.
293 MBB->insert(KillPos, MI);
302 /// NoUseAfterLastDef - Return true if there are no intervening uses between the
303 /// last instruction in the MBB that defines the specified register and the
304 /// two-address instruction which is being processed. It also returns the last
305 /// def location by reference
306 bool TwoAddressInstructionPass::NoUseAfterLastDef(unsigned Reg,
307 MachineBasicBlock *MBB, unsigned Dist,
310 unsigned LastUse = Dist;
311 for (MachineRegisterInfo::reg_iterator I = MRI->reg_begin(Reg),
312 E = MRI->reg_end(); I != E; ++I) {
313 MachineOperand &MO = I.getOperand();
314 MachineInstr *MI = MO.getParent();
315 if (MI->getParent() != MBB || MI->isDebugValue())
317 DenseMap<MachineInstr*, unsigned>::iterator DI = DistanceMap.find(MI);
318 if (DI == DistanceMap.end())
320 if (MO.isUse() && DI->second < LastUse)
321 LastUse = DI->second;
322 if (MO.isDef() && DI->second > LastDef)
323 LastDef = DI->second;
326 return !(LastUse > LastDef && LastUse < Dist);
329 /// isCopyToReg - Return true if the specified MI is a copy instruction or
330 /// a extract_subreg instruction. It also returns the source and destination
331 /// registers and whether they are physical registers by reference.
332 static bool isCopyToReg(MachineInstr &MI, const TargetInstrInfo *TII,
333 unsigned &SrcReg, unsigned &DstReg,
334 bool &IsSrcPhys, bool &IsDstPhys) {
338 DstReg = MI.getOperand(0).getReg();
339 SrcReg = MI.getOperand(1).getReg();
340 } else if (MI.isInsertSubreg() || MI.isSubregToReg()) {
341 DstReg = MI.getOperand(0).getReg();
342 SrcReg = MI.getOperand(2).getReg();
346 IsSrcPhys = TargetRegisterInfo::isPhysicalRegister(SrcReg);
347 IsDstPhys = TargetRegisterInfo::isPhysicalRegister(DstReg);
351 /// isKilled - Test if the given register value, which is used by the given
352 /// instruction, is killed by the given instruction. This looks through
353 /// coalescable copies to see if the original value is potentially not killed.
355 /// For example, in this code:
357 /// %reg1034 = copy %reg1024
358 /// %reg1035 = copy %reg1025<kill>
359 /// %reg1036 = add %reg1034<kill>, %reg1035<kill>
361 /// %reg1034 is not considered to be killed, since it is copied from a
362 /// register which is not killed. Treating it as not killed lets the
363 /// normal heuristics commute the (two-address) add, which lets
364 /// coalescing eliminate the extra copy.
366 static bool isKilled(MachineInstr &MI, unsigned Reg,
367 const MachineRegisterInfo *MRI,
368 const TargetInstrInfo *TII) {
369 MachineInstr *DefMI = &MI;
371 if (!DefMI->killsRegister(Reg))
373 if (TargetRegisterInfo::isPhysicalRegister(Reg))
375 MachineRegisterInfo::def_iterator Begin = MRI->def_begin(Reg);
376 // If there are multiple defs, we can't do a simple analysis, so just
377 // go with what the kill flag says.
378 if (llvm::next(Begin) != MRI->def_end())
381 bool IsSrcPhys, IsDstPhys;
382 unsigned SrcReg, DstReg;
383 // If the def is something other than a copy, then it isn't going to
384 // be coalesced, so follow the kill flag.
385 if (!isCopyToReg(*DefMI, TII, SrcReg, DstReg, IsSrcPhys, IsDstPhys))
391 /// isTwoAddrUse - Return true if the specified MI uses the specified register
392 /// as a two-address use. If so, return the destination register by reference.
393 static bool isTwoAddrUse(MachineInstr &MI, unsigned Reg, unsigned &DstReg) {
394 const MCInstrDesc &MCID = MI.getDesc();
395 unsigned NumOps = MI.isInlineAsm()
396 ? MI.getNumOperands() : MCID.getNumOperands();
397 for (unsigned i = 0; i != NumOps; ++i) {
398 const MachineOperand &MO = MI.getOperand(i);
399 if (!MO.isReg() || !MO.isUse() || MO.getReg() != Reg)
402 if (MI.isRegTiedToDefOperand(i, &ti)) {
403 DstReg = MI.getOperand(ti).getReg();
410 /// findOnlyInterestingUse - Given a register, if has a single in-basic block
411 /// use, return the use instruction if it's a copy or a two-address use.
413 MachineInstr *findOnlyInterestingUse(unsigned Reg, MachineBasicBlock *MBB,
414 MachineRegisterInfo *MRI,
415 const TargetInstrInfo *TII,
417 unsigned &DstReg, bool &IsDstPhys) {
418 if (!MRI->hasOneNonDBGUse(Reg))
419 // None or more than one use.
421 MachineInstr &UseMI = *MRI->use_nodbg_begin(Reg);
422 if (UseMI.getParent() != MBB)
426 if (isCopyToReg(UseMI, TII, SrcReg, DstReg, IsSrcPhys, IsDstPhys)) {
431 if (isTwoAddrUse(UseMI, Reg, DstReg)) {
432 IsDstPhys = TargetRegisterInfo::isPhysicalRegister(DstReg);
438 /// getMappedReg - Return the physical register the specified virtual register
439 /// might be mapped to.
441 getMappedReg(unsigned Reg, DenseMap<unsigned, unsigned> &RegMap) {
442 while (TargetRegisterInfo::isVirtualRegister(Reg)) {
443 DenseMap<unsigned, unsigned>::iterator SI = RegMap.find(Reg);
444 if (SI == RegMap.end())
448 if (TargetRegisterInfo::isPhysicalRegister(Reg))
453 /// regsAreCompatible - Return true if the two registers are equal or aliased.
456 regsAreCompatible(unsigned RegA, unsigned RegB, const TargetRegisterInfo *TRI) {
461 return TRI->regsOverlap(RegA, RegB);
465 /// isProfitableToCommute - Return true if it's potentially profitable to commute
466 /// the two-address instruction that's being processed.
468 TwoAddressInstructionPass::isProfitableToCommute(unsigned regA, unsigned regB,
470 MachineInstr *MI, MachineBasicBlock *MBB,
472 if (OptLevel == CodeGenOpt::None)
475 // Determine if it's profitable to commute this two address instruction. In
476 // general, we want no uses between this instruction and the definition of
477 // the two-address register.
479 // %reg1028<def> = EXTRACT_SUBREG %reg1027<kill>, 1
480 // %reg1029<def> = MOV8rr %reg1028
481 // %reg1029<def> = SHR8ri %reg1029, 7, %EFLAGS<imp-def,dead>
482 // insert => %reg1030<def> = MOV8rr %reg1028
483 // %reg1030<def> = ADD8rr %reg1028<kill>, %reg1029<kill>, %EFLAGS<imp-def,dead>
484 // In this case, it might not be possible to coalesce the second MOV8rr
485 // instruction if the first one is coalesced. So it would be profitable to
487 // %reg1028<def> = EXTRACT_SUBREG %reg1027<kill>, 1
488 // %reg1029<def> = MOV8rr %reg1028
489 // %reg1029<def> = SHR8ri %reg1029, 7, %EFLAGS<imp-def,dead>
490 // insert => %reg1030<def> = MOV8rr %reg1029
491 // %reg1030<def> = ADD8rr %reg1029<kill>, %reg1028<kill>, %EFLAGS<imp-def,dead>
493 if (!MI->killsRegister(regC))
496 // Ok, we have something like:
497 // %reg1030<def> = ADD8rr %reg1028<kill>, %reg1029<kill>, %EFLAGS<imp-def,dead>
498 // let's see if it's worth commuting it.
500 // Look for situations like this:
501 // %reg1024<def> = MOV r1
502 // %reg1025<def> = MOV r0
503 // %reg1026<def> = ADD %reg1024, %reg1025
505 // Commute the ADD to hopefully eliminate an otherwise unavoidable copy.
506 unsigned ToRegA = getMappedReg(regA, DstRegMap);
508 unsigned FromRegB = getMappedReg(regB, SrcRegMap);
509 unsigned FromRegC = getMappedReg(regC, SrcRegMap);
510 bool BComp = !FromRegB || regsAreCompatible(FromRegB, ToRegA, TRI);
511 bool CComp = !FromRegC || regsAreCompatible(FromRegC, ToRegA, TRI);
513 return !BComp && CComp;
516 // If there is a use of regC between its last def (could be livein) and this
517 // instruction, then bail.
518 unsigned LastDefC = 0;
519 if (!NoUseAfterLastDef(regC, MBB, Dist, LastDefC))
522 // If there is a use of regB between its last def (could be livein) and this
523 // instruction, then go ahead and make this transformation.
524 unsigned LastDefB = 0;
525 if (!NoUseAfterLastDef(regB, MBB, Dist, LastDefB))
528 // Since there are no intervening uses for both registers, then commute
529 // if the def of regC is closer. Its live interval is shorter.
530 return LastDefB && LastDefC && LastDefC > LastDefB;
533 /// CommuteInstruction - Commute a two-address instruction and update the basic
534 /// block, distance map, and live variables if needed. Return true if it is
537 TwoAddressInstructionPass::CommuteInstruction(MachineBasicBlock::iterator &mi,
538 MachineFunction::iterator &mbbi,
539 unsigned RegB, unsigned RegC, unsigned Dist) {
540 MachineInstr *MI = mi;
541 DEBUG(dbgs() << "2addr: COMMUTING : " << *MI);
542 MachineInstr *NewMI = TII->commuteInstruction(MI);
545 DEBUG(dbgs() << "2addr: COMMUTING FAILED!\n");
549 DEBUG(dbgs() << "2addr: COMMUTED TO: " << *NewMI);
550 // If the instruction changed to commute it, update livevar.
553 // Update live variables
554 LV->replaceKillInstruction(RegC, MI, NewMI);
556 Indexes->replaceMachineInstrInMaps(MI, NewMI);
558 mbbi->insert(mi, NewMI); // Insert the new inst
559 mbbi->erase(mi); // Nuke the old inst.
561 DistanceMap.insert(std::make_pair(NewMI, Dist));
564 // Update source register map.
565 unsigned FromRegC = getMappedReg(RegC, SrcRegMap);
567 unsigned RegA = MI->getOperand(0).getReg();
568 SrcRegMap[RegA] = FromRegC;
574 /// isProfitableToConv3Addr - Return true if it is profitable to convert the
575 /// given 2-address instruction to a 3-address one.
577 TwoAddressInstructionPass::isProfitableToConv3Addr(unsigned RegA,unsigned RegB){
578 // Look for situations like this:
579 // %reg1024<def> = MOV r1
580 // %reg1025<def> = MOV r0
581 // %reg1026<def> = ADD %reg1024, %reg1025
583 // Turn ADD into a 3-address instruction to avoid a copy.
584 unsigned FromRegB = getMappedReg(RegB, SrcRegMap);
587 unsigned ToRegA = getMappedReg(RegA, DstRegMap);
588 return (ToRegA && !regsAreCompatible(FromRegB, ToRegA, TRI));
591 /// ConvertInstTo3Addr - Convert the specified two-address instruction into a
592 /// three address one. Return true if this transformation was successful.
594 TwoAddressInstructionPass::ConvertInstTo3Addr(MachineBasicBlock::iterator &mi,
595 MachineBasicBlock::iterator &nmi,
596 MachineFunction::iterator &mbbi,
597 unsigned RegA, unsigned RegB,
599 MachineInstr *NewMI = TII->convertToThreeAddress(mbbi, mi, LV);
601 DEBUG(dbgs() << "2addr: CONVERTING 2-ADDR: " << *mi);
602 DEBUG(dbgs() << "2addr: TO 3-ADDR: " << *NewMI);
606 Indexes->replaceMachineInstrInMaps(mi, NewMI);
608 if (NewMI->findRegisterUseOperand(RegB, false, TRI))
609 // FIXME: Temporary workaround. If the new instruction doesn't
610 // uses RegB, convertToThreeAddress must have created more
611 // then one instruction.
612 Sunk = Sink3AddrInstruction(mbbi, NewMI, RegB, mi);
614 mbbi->erase(mi); // Nuke the old inst.
617 DistanceMap.insert(std::make_pair(NewMI, Dist));
619 nmi = llvm::next(mi);
622 // Update source and destination register maps.
623 SrcRegMap.erase(RegA);
624 DstRegMap.erase(RegB);
631 /// ScanUses - Scan forward recursively for only uses, update maps if the use
632 /// is a copy or a two-address instruction.
634 TwoAddressInstructionPass::ScanUses(unsigned DstReg, MachineBasicBlock *MBB,
635 SmallPtrSet<MachineInstr*, 8> &Processed) {
636 SmallVector<unsigned, 4> VirtRegPairs;
640 unsigned Reg = DstReg;
641 while (MachineInstr *UseMI = findOnlyInterestingUse(Reg, MBB, MRI, TII,IsCopy,
642 NewReg, IsDstPhys)) {
643 if (IsCopy && !Processed.insert(UseMI))
646 DenseMap<MachineInstr*, unsigned>::iterator DI = DistanceMap.find(UseMI);
647 if (DI != DistanceMap.end())
648 // Earlier in the same MBB.Reached via a back edge.
652 VirtRegPairs.push_back(NewReg);
655 bool isNew = SrcRegMap.insert(std::make_pair(NewReg, Reg)).second;
657 assert(SrcRegMap[NewReg] == Reg && "Can't map to two src registers!");
658 VirtRegPairs.push_back(NewReg);
662 if (!VirtRegPairs.empty()) {
663 unsigned ToReg = VirtRegPairs.back();
664 VirtRegPairs.pop_back();
665 while (!VirtRegPairs.empty()) {
666 unsigned FromReg = VirtRegPairs.back();
667 VirtRegPairs.pop_back();
668 bool isNew = DstRegMap.insert(std::make_pair(FromReg, ToReg)).second;
670 assert(DstRegMap[FromReg] == ToReg &&"Can't map to two dst registers!");
673 bool isNew = DstRegMap.insert(std::make_pair(DstReg, ToReg)).second;
675 assert(DstRegMap[DstReg] == ToReg && "Can't map to two dst registers!");
679 /// ProcessCopy - If the specified instruction is not yet processed, process it
680 /// if it's a copy. For a copy instruction, we find the physical registers the
681 /// source and destination registers might be mapped to. These are kept in
682 /// point-to maps used to determine future optimizations. e.g.
685 /// v1026 = add v1024, v1025
687 /// If 'add' is a two-address instruction, v1024, v1026 are both potentially
688 /// coalesced to r0 (from the input side). v1025 is mapped to r1. v1026 is
689 /// potentially joined with r1 on the output side. It's worthwhile to commute
690 /// 'add' to eliminate a copy.
691 void TwoAddressInstructionPass::ProcessCopy(MachineInstr *MI,
692 MachineBasicBlock *MBB,
693 SmallPtrSet<MachineInstr*, 8> &Processed) {
694 if (Processed.count(MI))
697 bool IsSrcPhys, IsDstPhys;
698 unsigned SrcReg, DstReg;
699 if (!isCopyToReg(*MI, TII, SrcReg, DstReg, IsSrcPhys, IsDstPhys))
702 if (IsDstPhys && !IsSrcPhys)
703 DstRegMap.insert(std::make_pair(SrcReg, DstReg));
704 else if (!IsDstPhys && IsSrcPhys) {
705 bool isNew = SrcRegMap.insert(std::make_pair(DstReg, SrcReg)).second;
707 assert(SrcRegMap[DstReg] == SrcReg &&
708 "Can't map to two src physical registers!");
710 ScanUses(DstReg, MBB, Processed);
713 Processed.insert(MI);
717 /// RescheduleMIBelowKill - If there is one more local instruction that reads
718 /// 'Reg' and it kills 'Reg, consider moving the instruction below the kill
719 /// instruction in order to eliminate the need for the copy.
721 TwoAddressInstructionPass::RescheduleMIBelowKill(MachineBasicBlock *MBB,
722 MachineBasicBlock::iterator &mi,
723 MachineBasicBlock::iterator &nmi,
725 // Bail immediately if we don't have LV available. We use it to find kills
730 MachineInstr *MI = &*mi;
731 DenseMap<MachineInstr*, unsigned>::iterator DI = DistanceMap.find(MI);
732 if (DI == DistanceMap.end())
733 // Must be created from unfolded load. Don't waste time trying this.
736 MachineInstr *KillMI = LV->getVarInfo(Reg).findKill(MBB);
737 if (!KillMI || MI == KillMI || KillMI->isCopy() || KillMI->isCopyLike())
738 // Don't mess with copies, they may be coalesced later.
741 if (KillMI->hasUnmodeledSideEffects() || KillMI->isCall() ||
742 KillMI->isBranch() || KillMI->isTerminator())
743 // Don't move pass calls, etc.
747 if (isTwoAddrUse(*KillMI, Reg, DstReg))
750 bool SeenStore = true;
751 if (!MI->isSafeToMove(TII, AA, SeenStore))
754 if (TII->getInstrLatency(InstrItins, MI) > 1)
755 // FIXME: Needs more sophisticated heuristics.
758 SmallSet<unsigned, 2> Uses;
759 SmallSet<unsigned, 2> Kills;
760 SmallSet<unsigned, 2> Defs;
761 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
762 const MachineOperand &MO = MI->getOperand(i);
765 unsigned MOReg = MO.getReg();
772 if (MO.isKill() && MOReg != Reg)
777 // Move the copies connected to MI down as well.
778 MachineBasicBlock::iterator From = MI;
779 MachineBasicBlock::iterator To = llvm::next(From);
780 while (To->isCopy() && Defs.count(To->getOperand(1).getReg())) {
781 Defs.insert(To->getOperand(0).getReg());
785 // Check if the reschedule will not break depedencies.
786 unsigned NumVisited = 0;
787 MachineBasicBlock::iterator KillPos = KillMI;
789 for (MachineBasicBlock::iterator I = To; I != KillPos; ++I) {
790 MachineInstr *OtherMI = I;
791 // DBG_VALUE cannot be counted against the limit.
792 if (OtherMI->isDebugValue())
794 if (NumVisited > 10) // FIXME: Arbitrary limit to reduce compile time cost.
797 if (OtherMI->hasUnmodeledSideEffects() || OtherMI->isCall() ||
798 OtherMI->isBranch() || OtherMI->isTerminator())
799 // Don't move pass calls, etc.
801 for (unsigned i = 0, e = OtherMI->getNumOperands(); i != e; ++i) {
802 const MachineOperand &MO = OtherMI->getOperand(i);
805 unsigned MOReg = MO.getReg();
809 if (Uses.count(MOReg))
810 // Physical register use would be clobbered.
812 if (!MO.isDead() && Defs.count(MOReg))
813 // May clobber a physical register def.
814 // FIXME: This may be too conservative. It's ok if the instruction
815 // is sunken completely below the use.
818 if (Defs.count(MOReg))
821 ((MO.isKill() && Uses.count(MOReg)) || Kills.count(MOReg)))
822 // Don't want to extend other live ranges and update kills.
824 if (MOReg == Reg && !MO.isKill())
825 // We can't schedule across a use of the register in question.
827 // Ensure that if this is register in question, its the kill we expect.
828 assert((MOReg != Reg || OtherMI == KillMI) &&
829 "Found multiple kills of a register in a basic block");
834 // Move debug info as well.
835 while (From != MBB->begin() && llvm::prior(From)->isDebugValue())
838 // Copies following MI may have been moved as well.
840 MBB->splice(KillPos, MBB, From, To);
841 DistanceMap.erase(DI);
843 // Update live variables
844 LV->removeVirtualRegisterKilled(Reg, KillMI);
845 LV->addVirtualRegisterKilled(Reg, MI);
849 DEBUG(dbgs() << "\trescheduled below kill: " << *KillMI);
853 /// isDefTooClose - Return true if the re-scheduling will put the given
854 /// instruction too close to the defs of its register dependencies.
855 bool TwoAddressInstructionPass::isDefTooClose(unsigned Reg, unsigned Dist,
857 MachineBasicBlock *MBB) {
858 for (MachineRegisterInfo::def_iterator DI = MRI->def_begin(Reg),
859 DE = MRI->def_end(); DI != DE; ++DI) {
860 MachineInstr *DefMI = &*DI;
861 if (DefMI->getParent() != MBB || DefMI->isCopy() || DefMI->isCopyLike())
864 return true; // MI is defining something KillMI uses
865 DenseMap<MachineInstr*, unsigned>::iterator DDI = DistanceMap.find(DefMI);
866 if (DDI == DistanceMap.end())
867 return true; // Below MI
868 unsigned DefDist = DDI->second;
869 assert(Dist > DefDist && "Visited def already?");
870 if (TII->getInstrLatency(InstrItins, DefMI) > (Dist - DefDist))
876 /// RescheduleKillAboveMI - If there is one more local instruction that reads
877 /// 'Reg' and it kills 'Reg, consider moving the kill instruction above the
878 /// current two-address instruction in order to eliminate the need for the
881 TwoAddressInstructionPass::RescheduleKillAboveMI(MachineBasicBlock *MBB,
882 MachineBasicBlock::iterator &mi,
883 MachineBasicBlock::iterator &nmi,
885 // Bail immediately if we don't have LV available. We use it to find kills
890 MachineInstr *MI = &*mi;
891 DenseMap<MachineInstr*, unsigned>::iterator DI = DistanceMap.find(MI);
892 if (DI == DistanceMap.end())
893 // Must be created from unfolded load. Don't waste time trying this.
896 MachineInstr *KillMI = LV->getVarInfo(Reg).findKill(MBB);
897 if (!KillMI || MI == KillMI || KillMI->isCopy() || KillMI->isCopyLike())
898 // Don't mess with copies, they may be coalesced later.
902 if (isTwoAddrUse(*KillMI, Reg, DstReg))
905 bool SeenStore = true;
906 if (!KillMI->isSafeToMove(TII, AA, SeenStore))
909 SmallSet<unsigned, 2> Uses;
910 SmallSet<unsigned, 2> Kills;
911 SmallSet<unsigned, 2> Defs;
912 SmallSet<unsigned, 2> LiveDefs;
913 for (unsigned i = 0, e = KillMI->getNumOperands(); i != e; ++i) {
914 const MachineOperand &MO = KillMI->getOperand(i);
917 unsigned MOReg = MO.getReg();
921 if (isDefTooClose(MOReg, DI->second, MI, MBB))
923 if (MOReg == Reg && !MO.isKill())
926 if (MO.isKill() && MOReg != Reg)
928 } else if (TargetRegisterInfo::isPhysicalRegister(MOReg)) {
931 LiveDefs.insert(MOReg);
935 // Check if the reschedule will not break depedencies.
936 unsigned NumVisited = 0;
937 MachineBasicBlock::iterator KillPos = KillMI;
938 for (MachineBasicBlock::iterator I = mi; I != KillPos; ++I) {
939 MachineInstr *OtherMI = I;
940 // DBG_VALUE cannot be counted against the limit.
941 if (OtherMI->isDebugValue())
943 if (NumVisited > 10) // FIXME: Arbitrary limit to reduce compile time cost.
946 if (OtherMI->hasUnmodeledSideEffects() || OtherMI->isCall() ||
947 OtherMI->isBranch() || OtherMI->isTerminator())
948 // Don't move pass calls, etc.
950 SmallVector<unsigned, 2> OtherDefs;
951 for (unsigned i = 0, e = OtherMI->getNumOperands(); i != e; ++i) {
952 const MachineOperand &MO = OtherMI->getOperand(i);
955 unsigned MOReg = MO.getReg();
959 if (Defs.count(MOReg))
960 // Moving KillMI can clobber the physical register if the def has
963 if (Kills.count(MOReg))
964 // Don't want to extend other live ranges and update kills.
966 if (OtherMI != MI && MOReg == Reg && !MO.isKill())
967 // We can't schedule across a use of the register in question.
970 OtherDefs.push_back(MOReg);
974 for (unsigned i = 0, e = OtherDefs.size(); i != e; ++i) {
975 unsigned MOReg = OtherDefs[i];
976 if (Uses.count(MOReg))
978 if (TargetRegisterInfo::isPhysicalRegister(MOReg) &&
979 LiveDefs.count(MOReg))
981 // Physical register def is seen.
986 // Move the old kill above MI, don't forget to move debug info as well.
987 MachineBasicBlock::iterator InsertPos = mi;
988 while (InsertPos != MBB->begin() && llvm::prior(InsertPos)->isDebugValue())
990 MachineBasicBlock::iterator From = KillMI;
991 MachineBasicBlock::iterator To = llvm::next(From);
992 while (llvm::prior(From)->isDebugValue())
994 MBB->splice(InsertPos, MBB, From, To);
996 nmi = llvm::prior(InsertPos); // Backtrack so we process the moved instr.
997 DistanceMap.erase(DI);
999 // Update live variables
1000 LV->removeVirtualRegisterKilled(Reg, KillMI);
1001 LV->addVirtualRegisterKilled(Reg, MI);
1003 LIS->handleMove(KillMI);
1005 DEBUG(dbgs() << "\trescheduled kill: " << *KillMI);
1009 /// TryInstructionTransform - For the case where an instruction has a single
1010 /// pair of tied register operands, attempt some transformations that may
1011 /// either eliminate the tied operands or improve the opportunities for
1012 /// coalescing away the register copy. Returns true if no copy needs to be
1013 /// inserted to untie mi's operands (either because they were untied, or
1014 /// because mi was rescheduled, and will be visited again later).
1015 bool TwoAddressInstructionPass::
1016 TryInstructionTransform(MachineBasicBlock::iterator &mi,
1017 MachineBasicBlock::iterator &nmi,
1018 MachineFunction::iterator &mbbi,
1019 unsigned SrcIdx, unsigned DstIdx, unsigned Dist,
1020 SmallPtrSet<MachineInstr*, 8> &Processed) {
1021 if (OptLevel == CodeGenOpt::None)
1024 MachineInstr &MI = *mi;
1025 unsigned regA = MI.getOperand(DstIdx).getReg();
1026 unsigned regB = MI.getOperand(SrcIdx).getReg();
1028 assert(TargetRegisterInfo::isVirtualRegister(regB) &&
1029 "cannot make instruction into two-address form");
1030 bool regBKilled = isKilled(MI, regB, MRI, TII);
1032 if (TargetRegisterInfo::isVirtualRegister(regA))
1033 ScanUses(regA, &*mbbi, Processed);
1035 // Check if it is profitable to commute the operands.
1036 unsigned SrcOp1, SrcOp2;
1038 unsigned regCIdx = ~0U;
1039 bool TryCommute = false;
1040 bool AggressiveCommute = false;
1041 if (MI.isCommutable() && MI.getNumOperands() >= 3 &&
1042 TII->findCommutedOpIndices(&MI, SrcOp1, SrcOp2)) {
1043 if (SrcIdx == SrcOp1)
1045 else if (SrcIdx == SrcOp2)
1048 if (regCIdx != ~0U) {
1049 regC = MI.getOperand(regCIdx).getReg();
1050 if (!regBKilled && isKilled(MI, regC, MRI, TII))
1051 // If C dies but B does not, swap the B and C operands.
1052 // This makes the live ranges of A and C joinable.
1054 else if (isProfitableToCommute(regA, regB, regC, &MI, mbbi, Dist)) {
1056 AggressiveCommute = true;
1061 // If it's profitable to commute, try to do so.
1062 if (TryCommute && CommuteInstruction(mi, mbbi, regB, regC, Dist)) {
1064 if (AggressiveCommute)
1069 // If there is one more use of regB later in the same MBB, consider
1070 // re-schedule this MI below it.
1071 if (RescheduleMIBelowKill(mbbi, mi, nmi, regB)) {
1076 if (MI.isConvertibleTo3Addr()) {
1077 // This instruction is potentially convertible to a true
1078 // three-address instruction. Check if it is profitable.
1079 if (!regBKilled || isProfitableToConv3Addr(regA, regB)) {
1080 // Try to convert it.
1081 if (ConvertInstTo3Addr(mi, nmi, mbbi, regA, regB, Dist)) {
1082 ++NumConvertedTo3Addr;
1083 return true; // Done with this instruction.
1088 // If there is one more use of regB later in the same MBB, consider
1089 // re-schedule it before this MI if it's legal.
1090 if (RescheduleKillAboveMI(mbbi, mi, nmi, regB)) {
1095 // If this is an instruction with a load folded into it, try unfolding
1096 // the load, e.g. avoid this:
1098 // addq (%rax), %rcx
1099 // in favor of this:
1100 // movq (%rax), %rcx
1102 // because it's preferable to schedule a load than a register copy.
1103 if (MI.mayLoad() && !regBKilled) {
1104 // Determine if a load can be unfolded.
1105 unsigned LoadRegIndex;
1107 TII->getOpcodeAfterMemoryUnfold(MI.getOpcode(),
1108 /*UnfoldLoad=*/true,
1109 /*UnfoldStore=*/false,
1112 const MCInstrDesc &UnfoldMCID = TII->get(NewOpc);
1113 if (UnfoldMCID.getNumDefs() == 1) {
1115 DEBUG(dbgs() << "2addr: UNFOLDING: " << MI);
1116 const TargetRegisterClass *RC =
1117 TRI->getAllocatableClass(
1118 TII->getRegClass(UnfoldMCID, LoadRegIndex, TRI, *MF));
1119 unsigned Reg = MRI->createVirtualRegister(RC);
1120 SmallVector<MachineInstr *, 2> NewMIs;
1121 if (!TII->unfoldMemoryOperand(*MF, &MI, Reg,
1122 /*UnfoldLoad=*/true,/*UnfoldStore=*/false,
1124 DEBUG(dbgs() << "2addr: ABANDONING UNFOLD\n");
1127 assert(NewMIs.size() == 2 &&
1128 "Unfolded a load into multiple instructions!");
1129 // The load was previously folded, so this is the only use.
1130 NewMIs[1]->addRegisterKilled(Reg, TRI);
1132 // Tentatively insert the instructions into the block so that they
1133 // look "normal" to the transformation logic.
1134 mbbi->insert(mi, NewMIs[0]);
1135 mbbi->insert(mi, NewMIs[1]);
1137 DEBUG(dbgs() << "2addr: NEW LOAD: " << *NewMIs[0]
1138 << "2addr: NEW INST: " << *NewMIs[1]);
1140 // Transform the instruction, now that it no longer has a load.
1141 unsigned NewDstIdx = NewMIs[1]->findRegisterDefOperandIdx(regA);
1142 unsigned NewSrcIdx = NewMIs[1]->findRegisterUseOperandIdx(regB);
1143 MachineBasicBlock::iterator NewMI = NewMIs[1];
1144 bool TransformSuccess =
1145 TryInstructionTransform(NewMI, mi, mbbi,
1146 NewSrcIdx, NewDstIdx, Dist, Processed);
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]);
1179 MI.eraseFromParent();
1181 if (TransformSuccess)
1184 // Transforming didn't eliminate the tie and didn't lead to an
1185 // improvement. Clean up the unfolded instructions and keep the
1187 DEBUG(dbgs() << "2addr: ABANDONING UNFOLD\n");
1188 NewMIs[0]->eraseFromParent();
1189 NewMIs[1]->eraseFromParent();
1198 // Collect tied operands of MI that need to be handled.
1199 // Rewrite trivial cases immediately.
1200 // Return true if any tied operands where found, including the trivial ones.
1201 bool TwoAddressInstructionPass::
1202 collectTiedOperands(MachineInstr *MI, TiedOperandMap &TiedOperands) {
1203 const MCInstrDesc &MCID = MI->getDesc();
1204 bool AnyOps = false;
1205 unsigned NumOps = MI->getNumOperands();
1207 for (unsigned SrcIdx = 0; SrcIdx < NumOps; ++SrcIdx) {
1208 unsigned DstIdx = 0;
1209 if (!MI->isRegTiedToDefOperand(SrcIdx, &DstIdx))
1212 MachineOperand &SrcMO = MI->getOperand(SrcIdx);
1213 MachineOperand &DstMO = MI->getOperand(DstIdx);
1214 unsigned SrcReg = SrcMO.getReg();
1215 unsigned DstReg = DstMO.getReg();
1216 // Tied constraint already satisfied?
1217 if (SrcReg == DstReg)
1220 assert(SrcReg && SrcMO.isUse() && "two address instruction invalid");
1222 // Deal with <undef> uses immediately - simply rewrite the src operand.
1223 if (SrcMO.isUndef()) {
1224 // Constrain the DstReg register class if required.
1225 if (TargetRegisterInfo::isVirtualRegister(DstReg))
1226 if (const TargetRegisterClass *RC = TII->getRegClass(MCID, SrcIdx,
1228 MRI->constrainRegClass(DstReg, RC);
1229 SrcMO.setReg(DstReg);
1230 DEBUG(dbgs() << "\t\trewrite undef:\t" << *MI);
1233 TiedOperands[SrcReg].push_back(std::make_pair(SrcIdx, DstIdx));
1238 // Process a list of tied MI operands that all use the same source register.
1239 // The tied pairs are of the form (SrcIdx, DstIdx).
1241 TwoAddressInstructionPass::processTiedPairs(MachineInstr *MI,
1242 TiedPairList &TiedPairs,
1244 bool IsEarlyClobber = false;
1245 bool RemovedKillFlag = false;
1246 bool AllUsesCopied = true;
1247 unsigned LastCopiedReg = 0;
1249 for (unsigned tpi = 0, tpe = TiedPairs.size(); tpi != tpe; ++tpi) {
1250 unsigned SrcIdx = TiedPairs[tpi].first;
1251 unsigned DstIdx = TiedPairs[tpi].second;
1253 const MachineOperand &DstMO = MI->getOperand(DstIdx);
1254 unsigned RegA = DstMO.getReg();
1255 IsEarlyClobber |= DstMO.isEarlyClobber();
1257 // Grab RegB from the instruction because it may have changed if the
1258 // instruction was commuted.
1259 RegB = MI->getOperand(SrcIdx).getReg();
1262 // The register is tied to multiple destinations (or else we would
1263 // not have continued this far), but this use of the register
1264 // already matches the tied destination. Leave it.
1265 AllUsesCopied = false;
1268 LastCopiedReg = RegA;
1270 assert(TargetRegisterInfo::isVirtualRegister(RegB) &&
1271 "cannot make instruction into two-address form");
1274 // First, verify that we don't have a use of "a" in the instruction
1275 // (a = b + a for example) because our transformation will not
1276 // work. This should never occur because we are in SSA form.
1277 for (unsigned i = 0; i != MI->getNumOperands(); ++i)
1278 assert(i == DstIdx ||
1279 !MI->getOperand(i).isReg() ||
1280 MI->getOperand(i).getReg() != RegA);
1284 BuildMI(*MI->getParent(), MI, MI->getDebugLoc(),
1285 TII->get(TargetOpcode::COPY), RegA).addReg(RegB);
1287 // Update DistanceMap.
1288 MachineBasicBlock::iterator PrevMI = MI;
1290 DistanceMap.insert(std::make_pair(PrevMI, Dist));
1291 DistanceMap[MI] = ++Dist;
1295 CopyIdx = Indexes->insertMachineInstrInMaps(PrevMI).getRegSlot();
1297 DEBUG(dbgs() << "\t\tprepend:\t" << *PrevMI);
1299 MachineOperand &MO = MI->getOperand(SrcIdx);
1300 assert(MO.isReg() && MO.getReg() == RegB && MO.isUse() &&
1301 "inconsistent operand info for 2-reg pass");
1303 MO.setIsKill(false);
1304 RemovedKillFlag = true;
1307 // Make sure regA is a legal regclass for the SrcIdx operand.
1308 if (TargetRegisterInfo::isVirtualRegister(RegA) &&
1309 TargetRegisterInfo::isVirtualRegister(RegB))
1310 MRI->constrainRegClass(RegA, MRI->getRegClass(RegB));
1314 // Propagate SrcRegMap.
1315 SrcRegMap[RegA] = RegB;
1319 if (AllUsesCopied) {
1320 if (!IsEarlyClobber) {
1321 // Replace other (un-tied) uses of regB with LastCopiedReg.
1322 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
1323 MachineOperand &MO = MI->getOperand(i);
1324 if (MO.isReg() && MO.getReg() == RegB && MO.isUse()) {
1326 MO.setIsKill(false);
1327 RemovedKillFlag = true;
1329 MO.setReg(LastCopiedReg);
1334 // Update live variables for regB.
1335 if (RemovedKillFlag && LV && LV->getVarInfo(RegB).removeKill(MI)) {
1336 MachineBasicBlock::iterator PrevMI = MI;
1338 LV->addVirtualRegisterKilled(RegB, PrevMI);
1341 } else if (RemovedKillFlag) {
1342 // Some tied uses of regB matched their destination registers, so
1343 // regB is still used in this instruction, but a kill flag was
1344 // removed from a different tied use of regB, so now we need to add
1345 // a kill flag to one of the remaining uses of regB.
1346 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
1347 MachineOperand &MO = MI->getOperand(i);
1348 if (MO.isReg() && MO.getReg() == RegB && MO.isUse()) {
1356 /// runOnMachineFunction - Reduce two-address instructions to two operands.
1358 bool TwoAddressInstructionPass::runOnMachineFunction(MachineFunction &Func) {
1360 const TargetMachine &TM = MF->getTarget();
1361 MRI = &MF->getRegInfo();
1362 TII = TM.getInstrInfo();
1363 TRI = TM.getRegisterInfo();
1364 InstrItins = TM.getInstrItineraryData();
1365 Indexes = getAnalysisIfAvailable<SlotIndexes>();
1366 LV = getAnalysisIfAvailable<LiveVariables>();
1367 LIS = getAnalysisIfAvailable<LiveIntervals>();
1368 AA = &getAnalysis<AliasAnalysis>();
1369 OptLevel = TM.getOptLevel();
1371 bool MadeChange = false;
1373 DEBUG(dbgs() << "********** REWRITING TWO-ADDR INSTRS **********\n");
1374 DEBUG(dbgs() << "********** Function: "
1375 << MF->getName() << '\n');
1377 // This pass takes the function out of SSA form.
1380 TiedOperandMap TiedOperands;
1382 SmallPtrSet<MachineInstr*, 8> Processed;
1383 for (MachineFunction::iterator mbbi = MF->begin(), mbbe = MF->end();
1384 mbbi != mbbe; ++mbbi) {
1386 DistanceMap.clear();
1390 for (MachineBasicBlock::iterator mi = mbbi->begin(), me = mbbi->end();
1392 MachineBasicBlock::iterator nmi = llvm::next(mi);
1393 if (mi->isDebugValue()) {
1398 // Remember REG_SEQUENCE instructions, we'll deal with them later.
1399 if (mi->isRegSequence())
1400 RegSequences.push_back(&*mi);
1402 DistanceMap.insert(std::make_pair(mi, ++Dist));
1404 ProcessCopy(&*mi, &*mbbi, Processed);
1406 // First scan through all the tied register uses in this instruction
1407 // and record a list of pairs of tied operands for each register.
1408 if (!collectTiedOperands(mi, TiedOperands)) {
1413 ++NumTwoAddressInstrs;
1415 DEBUG(dbgs() << '\t' << *mi);
1417 // If the instruction has a single pair of tied operands, try some
1418 // transformations that may either eliminate the tied operands or
1419 // improve the opportunities for coalescing away the register copy.
1420 if (TiedOperands.size() == 1) {
1421 SmallVector<std::pair<unsigned, unsigned>, 4> &TiedPairs
1422 = TiedOperands.begin()->second;
1423 if (TiedPairs.size() == 1) {
1424 unsigned SrcIdx = TiedPairs[0].first;
1425 unsigned DstIdx = TiedPairs[0].second;
1426 unsigned SrcReg = mi->getOperand(SrcIdx).getReg();
1427 unsigned DstReg = mi->getOperand(DstIdx).getReg();
1428 if (SrcReg != DstReg &&
1429 TryInstructionTransform(mi, nmi, mbbi, SrcIdx, DstIdx, Dist,
1431 // The tied operands have been eliminated or shifted further down the
1432 // block to ease elimination. Continue processing with 'nmi'.
1433 TiedOperands.clear();
1440 // Now iterate over the information collected above.
1441 for (TiedOperandMap::iterator OI = TiedOperands.begin(),
1442 OE = TiedOperands.end(); OI != OE; ++OI) {
1443 processTiedPairs(mi, OI->second, Dist);
1444 DEBUG(dbgs() << "\t\trewrite to:\t" << *mi);
1447 // Rewrite INSERT_SUBREG as COPY now that we no longer need SSA form.
1448 if (mi->isInsertSubreg()) {
1449 // From %reg = INSERT_SUBREG %reg, %subreg, subidx
1450 // To %reg:subidx = COPY %subreg
1451 unsigned SubIdx = mi->getOperand(3).getImm();
1452 mi->RemoveOperand(3);
1453 assert(mi->getOperand(0).getSubReg() == 0 && "Unexpected subreg idx");
1454 mi->getOperand(0).setSubReg(SubIdx);
1455 mi->getOperand(0).setIsUndef(mi->getOperand(1).isUndef());
1456 mi->RemoveOperand(1);
1457 mi->setDesc(TII->get(TargetOpcode::COPY));
1458 DEBUG(dbgs() << "\t\tconvert to:\t" << *mi);
1461 // Clear TiedOperands here instead of at the top of the loop
1462 // since most instructions do not have tied operands.
1463 TiedOperands.clear();
1468 // Eliminate REG_SEQUENCE instructions. Their whole purpose was to preseve
1469 // SSA form. It's now safe to de-SSA.
1470 MadeChange |= EliminateRegSequences();
1475 static void UpdateRegSequenceSrcs(unsigned SrcReg,
1476 unsigned DstReg, unsigned SubIdx,
1477 MachineRegisterInfo *MRI,
1478 const TargetRegisterInfo &TRI) {
1479 for (MachineRegisterInfo::reg_iterator RI = MRI->reg_begin(SrcReg),
1480 RE = MRI->reg_end(); RI != RE; ) {
1481 MachineOperand &MO = RI.getOperand();
1483 MO.substVirtReg(DstReg, SubIdx, TRI);
1487 // Find the first def of Reg, assuming they are all in the same basic block.
1488 static MachineInstr *findFirstDef(unsigned Reg, MachineRegisterInfo *MRI) {
1489 SmallPtrSet<MachineInstr*, 8> Defs;
1490 MachineInstr *First = 0;
1491 for (MachineRegisterInfo::def_iterator RI = MRI->def_begin(Reg);
1492 MachineInstr *MI = RI.skipInstruction(); Defs.insert(MI))
1497 MachineBasicBlock *MBB = First->getParent();
1498 MachineBasicBlock::iterator A = First, B = First;
1502 if (A != MBB->begin()) {
1505 if (Defs.erase(A)) First = A;
1507 if (B != MBB->end()) {
1512 } while (Moving && !Defs.empty());
1513 assert(Defs.empty() && "Instructions outside basic block!");
1517 /// CoalesceExtSubRegs - If a number of sources of the REG_SEQUENCE are
1518 /// EXTRACT_SUBREG from the same register and to the same virtual register
1519 /// with different sub-register indices, attempt to combine the
1520 /// EXTRACT_SUBREGs and pre-coalesce them. e.g.
1521 /// %reg1026<def> = VLDMQ %reg1025<kill>, 260, pred:14, pred:%reg0
1522 /// %reg1029:6<def> = EXTRACT_SUBREG %reg1026, 6
1523 /// %reg1029:5<def> = EXTRACT_SUBREG %reg1026<kill>, 5
1524 /// Since D subregs 5, 6 can combine to a Q register, we can coalesce
1525 /// reg1026 to reg1029.
1527 TwoAddressInstructionPass::CoalesceExtSubRegs(SmallVector<unsigned,4> &Srcs,
1529 SmallSet<unsigned, 4> Seen;
1530 for (unsigned i = 0, e = Srcs.size(); i != e; ++i) {
1531 unsigned SrcReg = Srcs[i];
1532 if (!Seen.insert(SrcReg))
1535 // Check that the instructions are all in the same basic block.
1536 MachineInstr *SrcDefMI = MRI->getUniqueVRegDef(SrcReg);
1537 MachineInstr *DstDefMI = MRI->getUniqueVRegDef(DstReg);
1538 if (!SrcDefMI || !DstDefMI ||
1539 SrcDefMI->getParent() != DstDefMI->getParent())
1542 // If there are no other uses than copies which feed into
1543 // the reg_sequence, then we might be able to coalesce them.
1544 bool CanCoalesce = true;
1545 SmallVector<unsigned, 4> SrcSubIndices, DstSubIndices;
1546 for (MachineRegisterInfo::use_nodbg_iterator
1547 UI = MRI->use_nodbg_begin(SrcReg),
1548 UE = MRI->use_nodbg_end(); UI != UE; ++UI) {
1549 MachineInstr *UseMI = &*UI;
1550 if (!UseMI->isCopy() || UseMI->getOperand(0).getReg() != DstReg) {
1551 CanCoalesce = false;
1554 SrcSubIndices.push_back(UseMI->getOperand(1).getSubReg());
1555 DstSubIndices.push_back(UseMI->getOperand(0).getSubReg());
1558 if (!CanCoalesce || SrcSubIndices.size() < 2)
1561 // Check that the source subregisters can be combined.
1562 std::sort(SrcSubIndices.begin(), SrcSubIndices.end());
1563 unsigned NewSrcSubIdx = 0;
1564 if (!TRI->canCombineSubRegIndices(MRI->getRegClass(SrcReg), SrcSubIndices,
1568 // Check that the destination subregisters can also be combined.
1569 std::sort(DstSubIndices.begin(), DstSubIndices.end());
1570 unsigned NewDstSubIdx = 0;
1571 if (!TRI->canCombineSubRegIndices(MRI->getRegClass(DstReg), DstSubIndices,
1575 // If neither source nor destination can be combined to the full register,
1576 // just give up. This could be improved if it ever matters.
1577 if (NewSrcSubIdx != 0 && NewDstSubIdx != 0)
1580 // Now that we know that all the uses are extract_subregs and that those
1581 // subregs can somehow be combined, scan all the extract_subregs again to
1582 // make sure the subregs are in the right order and can be composed.
1583 MachineInstr *SomeMI = 0;
1585 for (MachineRegisterInfo::use_nodbg_iterator
1586 UI = MRI->use_nodbg_begin(SrcReg),
1587 UE = MRI->use_nodbg_end(); UI != UE; ++UI) {
1588 MachineInstr *UseMI = &*UI;
1589 assert(UseMI->isCopy());
1590 unsigned DstSubIdx = UseMI->getOperand(0).getSubReg();
1591 unsigned SrcSubIdx = UseMI->getOperand(1).getSubReg();
1592 assert(DstSubIdx != 0 && "missing subreg from RegSequence elimination");
1593 if ((NewDstSubIdx == 0 &&
1594 TRI->composeSubRegIndices(NewSrcSubIdx, DstSubIdx) != SrcSubIdx) ||
1595 (NewSrcSubIdx == 0 &&
1596 TRI->composeSubRegIndices(NewDstSubIdx, SrcSubIdx) != DstSubIdx)) {
1597 CanCoalesce = false;
1600 // Keep track of one of the uses. Preferably the first one which has a
1601 // <def,undef> flag.
1602 if (!SomeMI || UseMI->getOperand(0).isUndef())
1608 // Insert a copy to replace the original.
1609 MachineInstr *CopyMI = BuildMI(*SomeMI->getParent(), SomeMI,
1610 SomeMI->getDebugLoc(),
1611 TII->get(TargetOpcode::COPY))
1612 .addReg(DstReg, RegState::Define |
1613 getUndefRegState(SomeMI->getOperand(0).isUndef()),
1615 .addReg(SrcReg, 0, NewSrcSubIdx);
1617 // Remove all the old extract instructions.
1618 for (MachineRegisterInfo::use_nodbg_iterator
1619 UI = MRI->use_nodbg_begin(SrcReg),
1620 UE = MRI->use_nodbg_end(); UI != UE; ) {
1621 MachineInstr *UseMI = &*UI;
1623 if (UseMI == CopyMI)
1625 assert(UseMI->isCopy());
1626 // Move any kills to the new copy or extract instruction.
1627 if (UseMI->getOperand(1).isKill()) {
1628 CopyMI->getOperand(1).setIsKill();
1630 // Update live variables
1631 LV->replaceKillInstruction(SrcReg, UseMI, &*CopyMI);
1633 UseMI->eraseFromParent();
1638 static bool HasOtherRegSequenceUses(unsigned Reg, MachineInstr *RegSeq,
1639 MachineRegisterInfo *MRI) {
1640 for (MachineRegisterInfo::use_iterator UI = MRI->use_begin(Reg),
1641 UE = MRI->use_end(); UI != UE; ++UI) {
1642 MachineInstr *UseMI = &*UI;
1643 if (UseMI != RegSeq && UseMI->isRegSequence())
1649 /// EliminateRegSequences - Eliminate REG_SEQUENCE instructions as part
1650 /// of the de-ssa process. This replaces sources of REG_SEQUENCE as
1651 /// sub-register references of the register defined by REG_SEQUENCE. e.g.
1653 /// %reg1029<def>, %reg1030<def> = VLD1q16 %reg1024<kill>, ...
1654 /// %reg1031<def> = REG_SEQUENCE %reg1029<kill>, 5, %reg1030<kill>, 6
1656 /// %reg1031:5<def>, %reg1031:6<def> = VLD1q16 %reg1024<kill>, ...
1657 bool TwoAddressInstructionPass::EliminateRegSequences() {
1658 if (RegSequences.empty())
1661 for (unsigned i = 0, e = RegSequences.size(); i != e; ++i) {
1662 MachineInstr *MI = RegSequences[i];
1663 unsigned DstReg = MI->getOperand(0).getReg();
1664 if (MI->getOperand(0).getSubReg() ||
1665 TargetRegisterInfo::isPhysicalRegister(DstReg) ||
1666 !(MI->getNumOperands() & 1)) {
1667 DEBUG(dbgs() << "Illegal REG_SEQUENCE instruction:" << *MI);
1668 llvm_unreachable(0);
1671 bool IsImpDef = true;
1672 SmallVector<unsigned, 4> RealSrcs;
1673 SmallSet<unsigned, 4> Seen;
1674 for (unsigned i = 1, e = MI->getNumOperands(); i < e; i += 2) {
1675 // Nothing needs to be inserted for <undef> operands.
1676 if (MI->getOperand(i).isUndef()) {
1677 MI->getOperand(i).setReg(0);
1680 unsigned SrcReg = MI->getOperand(i).getReg();
1681 unsigned SrcSubIdx = MI->getOperand(i).getSubReg();
1682 unsigned SubIdx = MI->getOperand(i+1).getImm();
1683 // DefMI of NULL means the value does not have a vreg in this block
1684 // i.e., its a physical register or a subreg.
1685 // In either case we force a copy to be generated.
1686 MachineInstr *DefMI = NULL;
1687 if (!MI->getOperand(i).getSubReg() &&
1688 !TargetRegisterInfo::isPhysicalRegister(SrcReg)) {
1689 DefMI = MRI->getUniqueVRegDef(SrcReg);
1692 if (DefMI && DefMI->isImplicitDef()) {
1693 DefMI->eraseFromParent();
1698 // Remember COPY sources. These might be candidate for coalescing.
1699 if (DefMI && DefMI->isCopy() && DefMI->getOperand(1).getSubReg())
1700 RealSrcs.push_back(DefMI->getOperand(1).getReg());
1702 bool isKill = MI->getOperand(i).isKill();
1703 if (!DefMI || !Seen.insert(SrcReg) ||
1704 MI->getParent() != DefMI->getParent() ||
1705 !isKill || HasOtherRegSequenceUses(SrcReg, MI, MRI) ||
1706 !TRI->getMatchingSuperRegClass(MRI->getRegClass(DstReg),
1707 MRI->getRegClass(SrcReg), SubIdx)) {
1708 // REG_SEQUENCE cannot have duplicated operands, add a copy.
1709 // Also add an copy if the source is live-in the block. We don't want
1710 // to end up with a partial-redef of a livein, e.g.
1712 // reg1051:10<def> =
1718 // LiveIntervalAnalysis won't like it.
1720 // If the REG_SEQUENCE doesn't kill its source, keeping live variables
1721 // correctly up to date becomes very difficult. Insert a copy.
1723 // Defer any kill flag to the last operand using SrcReg. Otherwise, we
1724 // might insert a COPY that uses SrcReg after is was killed.
1726 for (unsigned j = i + 2; j < e; j += 2)
1727 if (MI->getOperand(j).getReg() == SrcReg) {
1728 MI->getOperand(j).setIsKill();
1733 MachineBasicBlock::iterator InsertLoc = MI;
1734 MachineInstr *CopyMI = BuildMI(*MI->getParent(), InsertLoc,
1735 MI->getDebugLoc(), TII->get(TargetOpcode::COPY))
1736 .addReg(DstReg, RegState::Define, SubIdx)
1737 .addReg(SrcReg, getKillRegState(isKill), SrcSubIdx);
1738 MI->getOperand(i).setReg(0);
1739 if (LV && isKill && !TargetRegisterInfo::isPhysicalRegister(SrcReg))
1740 LV->replaceKillInstruction(SrcReg, MI, CopyMI);
1741 DEBUG(dbgs() << "Inserted: " << *CopyMI);
1745 for (unsigned i = 1, e = MI->getNumOperands(); i < e; i += 2) {
1746 unsigned SrcReg = MI->getOperand(i).getReg();
1747 if (!SrcReg) continue;
1748 unsigned SubIdx = MI->getOperand(i+1).getImm();
1749 UpdateRegSequenceSrcs(SrcReg, DstReg, SubIdx, MRI, *TRI);
1752 // Set <def,undef> flags on the first DstReg def in the basic block.
1753 // It marks the beginning of the live range. All the other defs are
1754 // read-modify-write.
1755 if (MachineInstr *Def = findFirstDef(DstReg, MRI)) {
1756 for (unsigned i = 0, e = Def->getNumOperands(); i != e; ++i) {
1757 MachineOperand &MO = Def->getOperand(i);
1758 if (MO.isReg() && MO.isDef() && MO.getReg() == DstReg)
1761 // Make sure there is a full non-subreg imp-def operand on the
1762 // instruction. This shouldn't be necessary, but it seems that at least
1763 // RAFast requires it.
1764 Def->addRegisterDefined(DstReg, TRI);
1765 DEBUG(dbgs() << "First def: " << *Def);
1769 DEBUG(dbgs() << "Turned: " << *MI << " into an IMPLICIT_DEF");
1770 MI->setDesc(TII->get(TargetOpcode::IMPLICIT_DEF));
1771 for (int j = MI->getNumOperands() - 1, ee = 0; j > ee; --j)
1772 MI->RemoveOperand(j);
1774 DEBUG(dbgs() << "Eliminated: " << *MI);
1775 MI->eraseFromParent();
1778 // Try coalescing some EXTRACT_SUBREG instructions. This can create
1779 // INSERT_SUBREG instructions that must have <undef> flags added by
1780 // LiveIntervalAnalysis, so only run it when LiveVariables is available.
1782 CoalesceExtSubRegs(RealSrcs, DstReg);
1785 RegSequences.clear();