1 //===- RegisterCoalescer.cpp - Generic Register Coalescing Interface -------==//
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 generic RegisterCoalescer interface which
11 // is used as the common interface used by all clients and
12 // implementations of register coalescing.
14 //===----------------------------------------------------------------------===//
16 #define DEBUG_TYPE "regalloc"
17 #include "RegisterCoalescer.h"
18 #include "LiveDebugVariables.h"
19 #include "RegisterClassInfo.h"
20 #include "VirtRegMap.h"
22 #include "llvm/Pass.h"
23 #include "llvm/Value.h"
24 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
25 #include "llvm/CodeGen/MachineInstr.h"
26 #include "llvm/CodeGen/MachineRegisterInfo.h"
27 #include "llvm/Target/TargetInstrInfo.h"
28 #include "llvm/Target/TargetRegisterInfo.h"
29 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
30 #include "llvm/Analysis/AliasAnalysis.h"
31 #include "llvm/CodeGen/MachineFrameInfo.h"
32 #include "llvm/CodeGen/MachineInstr.h"
33 #include "llvm/CodeGen/MachineLoopInfo.h"
34 #include "llvm/CodeGen/MachineRegisterInfo.h"
35 #include "llvm/CodeGen/Passes.h"
36 #include "llvm/Target/TargetInstrInfo.h"
37 #include "llvm/Target/TargetMachine.h"
38 #include "llvm/Target/TargetOptions.h"
39 #include "llvm/Support/CommandLine.h"
40 #include "llvm/Support/Debug.h"
41 #include "llvm/Support/ErrorHandling.h"
42 #include "llvm/Support/raw_ostream.h"
43 #include "llvm/ADT/OwningPtr.h"
44 #include "llvm/ADT/SmallSet.h"
45 #include "llvm/ADT/Statistic.h"
46 #include "llvm/ADT/STLExtras.h"
51 STATISTIC(numJoins , "Number of interval joins performed");
52 STATISTIC(numCrossRCs , "Number of cross class joins performed");
53 STATISTIC(numCommutes , "Number of instruction commuting performed");
54 STATISTIC(numExtends , "Number of copies extended");
55 STATISTIC(NumReMats , "Number of instructions re-materialized");
56 STATISTIC(numPeep , "Number of identity moves eliminated after coalescing");
57 STATISTIC(numAborts , "Number of times interval joining aborted");
58 STATISTIC(NumInflated , "Number of register classes inflated");
61 EnableJoining("join-liveintervals",
62 cl::desc("Coalesce copies (default=true)"),
66 DisableCrossClassJoin("disable-cross-class-join",
67 cl::desc("Avoid coalescing cross register class copies"),
68 cl::init(false), cl::Hidden);
71 EnablePhysicalJoin("join-physregs",
72 cl::desc("Join physical register copies"),
73 cl::init(false), cl::Hidden);
76 VerifyCoalescing("verify-coalescing",
77 cl::desc("Verify machine instrs before and after register coalescing"),
81 class RegisterCoalescer : public MachineFunctionPass {
83 MachineRegisterInfo* MRI;
84 const TargetMachine* TM;
85 const TargetRegisterInfo* TRI;
86 const TargetInstrInfo* TII;
88 LiveDebugVariables *LDV;
89 const MachineLoopInfo* Loops;
91 RegisterClassInfo RegClassInfo;
93 /// JoinedCopies - Keep track of copies eliminated due to coalescing.
95 SmallPtrSet<MachineInstr*, 32> JoinedCopies;
97 /// ReMatCopies - Keep track of copies eliminated due to remat.
99 SmallPtrSet<MachineInstr*, 32> ReMatCopies;
101 /// ReMatDefs - Keep track of definition instructions which have
103 SmallPtrSet<MachineInstr*, 8> ReMatDefs;
105 /// joinIntervals - join compatible live intervals
106 void joinIntervals();
108 /// CopyCoalesceInMBB - Coalesce copies in the specified MBB, putting
109 /// copies that cannot yet be coalesced into the "TryAgain" list.
110 void CopyCoalesceInMBB(MachineBasicBlock *MBB,
111 std::vector<MachineInstr*> &TryAgain);
113 /// JoinCopy - Attempt to join intervals corresponding to SrcReg/DstReg,
114 /// which are the src/dst of the copy instruction CopyMI. This returns
115 /// true if the copy was successfully coalesced away. If it is not
116 /// currently possible to coalesce this interval, but it may be possible if
117 /// other things get coalesced, then it returns true by reference in
119 bool JoinCopy(MachineInstr *TheCopy, bool &Again);
121 /// JoinIntervals - Attempt to join these two intervals. On failure, this
122 /// returns false. The output "SrcInt" will not have been modified, so we
123 /// can use this information below to update aliases.
124 bool JoinIntervals(CoalescerPair &CP);
126 /// AdjustCopiesBackFrom - We found a non-trivially-coalescable copy. If
127 /// the source value number is defined by a copy from the destination reg
128 /// see if we can merge these two destination reg valno# into a single
129 /// value number, eliminating a copy.
130 bool AdjustCopiesBackFrom(const CoalescerPair &CP, MachineInstr *CopyMI);
132 /// HasOtherReachingDefs - Return true if there are definitions of IntB
133 /// other than BValNo val# that can reach uses of AValno val# of IntA.
134 bool HasOtherReachingDefs(LiveInterval &IntA, LiveInterval &IntB,
135 VNInfo *AValNo, VNInfo *BValNo);
137 /// RemoveCopyByCommutingDef - We found a non-trivially-coalescable copy.
138 /// If the source value number is defined by a commutable instruction and
139 /// its other operand is coalesced to the copy dest register, see if we
140 /// can transform the copy into a noop by commuting the definition.
141 bool RemoveCopyByCommutingDef(const CoalescerPair &CP,MachineInstr *CopyMI);
143 /// ReMaterializeTrivialDef - If the source of a copy is defined by a
144 /// trivial computation, replace the copy by rematerialize the definition.
145 /// If PreserveSrcInt is true, make sure SrcInt is valid after the call.
146 bool ReMaterializeTrivialDef(LiveInterval &SrcInt, bool PreserveSrcInt,
147 unsigned DstReg, MachineInstr *CopyMI);
149 /// shouldJoinPhys - Return true if a physreg copy should be joined.
150 bool shouldJoinPhys(CoalescerPair &CP);
152 /// isWinToJoinCrossClass - Return true if it's profitable to coalesce
153 /// two virtual registers from different register classes.
154 bool isWinToJoinCrossClass(unsigned SrcReg,
156 const TargetRegisterClass *SrcRC,
157 const TargetRegisterClass *DstRC,
158 const TargetRegisterClass *NewRC);
160 /// UpdateRegDefsUses - Replace all defs and uses of SrcReg to DstReg and
161 /// update the subregister number if it is not zero. If DstReg is a
162 /// physical register and the existing subregister number of the def / use
163 /// being updated is not zero, make sure to set it to the correct physical
165 void UpdateRegDefsUses(const CoalescerPair &CP);
167 /// RemoveDeadDef - If a def of a live interval is now determined dead,
168 /// remove the val# it defines. If the live interval becomes empty, remove
170 bool RemoveDeadDef(LiveInterval &li, MachineInstr *DefMI);
172 /// markAsJoined - Remember that CopyMI has already been joined.
173 void markAsJoined(MachineInstr *CopyMI);
175 /// eliminateUndefCopy - Handle copies of undef values.
176 bool eliminateUndefCopy(MachineInstr *CopyMI, const CoalescerPair &CP);
179 static char ID; // Class identification, replacement for typeinfo
180 RegisterCoalescer() : MachineFunctionPass(ID) {
181 initializeRegisterCoalescerPass(*PassRegistry::getPassRegistry());
184 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
186 virtual void releaseMemory();
188 /// runOnMachineFunction - pass entry point
189 virtual bool runOnMachineFunction(MachineFunction&);
191 /// print - Implement the dump method.
192 virtual void print(raw_ostream &O, const Module* = 0) const;
194 } /// end anonymous namespace
196 char &llvm::RegisterCoalescerID = RegisterCoalescer::ID;
198 INITIALIZE_PASS_BEGIN(RegisterCoalescer, "simple-register-coalescing",
199 "Simple Register Coalescing", false, false)
200 INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
201 INITIALIZE_PASS_DEPENDENCY(LiveDebugVariables)
202 INITIALIZE_PASS_DEPENDENCY(SlotIndexes)
203 INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
204 INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
205 INITIALIZE_PASS_END(RegisterCoalescer, "simple-register-coalescing",
206 "Simple Register Coalescing", false, false)
208 char RegisterCoalescer::ID = 0;
210 static unsigned compose(const TargetRegisterInfo &tri, unsigned a, unsigned b) {
213 return tri.composeSubRegIndices(a, b);
216 static bool isMoveInstr(const TargetRegisterInfo &tri, const MachineInstr *MI,
217 unsigned &Src, unsigned &Dst,
218 unsigned &SrcSub, unsigned &DstSub) {
220 Dst = MI->getOperand(0).getReg();
221 DstSub = MI->getOperand(0).getSubReg();
222 Src = MI->getOperand(1).getReg();
223 SrcSub = MI->getOperand(1).getSubReg();
224 } else if (MI->isSubregToReg()) {
225 Dst = MI->getOperand(0).getReg();
226 DstSub = compose(tri, MI->getOperand(0).getSubReg(),
227 MI->getOperand(3).getImm());
228 Src = MI->getOperand(2).getReg();
229 SrcSub = MI->getOperand(2).getSubReg();
235 bool CoalescerPair::setRegisters(const MachineInstr *MI) {
236 SrcReg = DstReg = SubIdx = 0;
238 Flipped = CrossClass = false;
240 unsigned Src, Dst, SrcSub, DstSub;
241 if (!isMoveInstr(TRI, MI, Src, Dst, SrcSub, DstSub))
243 Partial = SrcSub || DstSub;
245 // If one register is a physreg, it must be Dst.
246 if (TargetRegisterInfo::isPhysicalRegister(Src)) {
247 if (TargetRegisterInfo::isPhysicalRegister(Dst))
250 std::swap(SrcSub, DstSub);
254 const MachineRegisterInfo &MRI = MI->getParent()->getParent()->getRegInfo();
256 if (TargetRegisterInfo::isPhysicalRegister(Dst)) {
257 // Eliminate DstSub on a physreg.
259 Dst = TRI.getSubReg(Dst, DstSub);
260 if (!Dst) return false;
264 // Eliminate SrcSub by picking a corresponding Dst superregister.
266 Dst = TRI.getMatchingSuperReg(Dst, SrcSub, MRI.getRegClass(Src));
267 if (!Dst) return false;
269 } else if (!MRI.getRegClass(Src)->contains(Dst)) {
273 // Both registers are virtual.
275 // Both registers have subreg indices.
276 if (SrcSub && DstSub) {
277 // For now we only handle the case of identical indices in commensurate
278 // registers: Dreg:ssub_1 + Dreg:ssub_1 -> Dreg
279 // FIXME: Handle Qreg:ssub_3 + Dreg:ssub_1 as QReg:dsub_1 + Dreg.
280 if (SrcSub != DstSub)
282 const TargetRegisterClass *SrcRC = MRI.getRegClass(Src);
283 const TargetRegisterClass *DstRC = MRI.getRegClass(Dst);
284 if (!TRI.getCommonSubClass(DstRC, SrcRC))
289 // There can be no SrcSub.
294 assert(!Flipped && "Unexpected flip");
298 // Find the new register class.
299 const TargetRegisterClass *SrcRC = MRI.getRegClass(Src);
300 const TargetRegisterClass *DstRC = MRI.getRegClass(Dst);
302 NewRC = TRI.getMatchingSuperRegClass(DstRC, SrcRC, DstSub);
304 NewRC = TRI.getCommonSubClass(DstRC, SrcRC);
307 CrossClass = NewRC != DstRC || NewRC != SrcRC;
309 // Check our invariants
310 assert(TargetRegisterInfo::isVirtualRegister(Src) && "Src must be virtual");
311 assert(!(TargetRegisterInfo::isPhysicalRegister(Dst) && DstSub) &&
312 "Cannot have a physical SubIdx");
319 bool CoalescerPair::flip() {
320 if (SubIdx || TargetRegisterInfo::isPhysicalRegister(DstReg))
322 std::swap(SrcReg, DstReg);
327 bool CoalescerPair::isCoalescable(const MachineInstr *MI) const {
330 unsigned Src, Dst, SrcSub, DstSub;
331 if (!isMoveInstr(TRI, MI, Src, Dst, SrcSub, DstSub))
334 // Find the virtual register that is SrcReg.
337 std::swap(SrcSub, DstSub);
338 } else if (Src != SrcReg) {
342 // Now check that Dst matches DstReg.
343 if (TargetRegisterInfo::isPhysicalRegister(DstReg)) {
344 if (!TargetRegisterInfo::isPhysicalRegister(Dst))
346 assert(!SubIdx && "Inconsistent CoalescerPair state.");
347 // DstSub could be set for a physreg from INSERT_SUBREG.
349 Dst = TRI.getSubReg(Dst, DstSub);
352 return DstReg == Dst;
353 // This is a partial register copy. Check that the parts match.
354 return TRI.getSubReg(DstReg, SrcSub) == Dst;
356 // DstReg is virtual.
359 // Registers match, do the subregisters line up?
360 return compose(TRI, SubIdx, SrcSub) == DstSub;
364 void RegisterCoalescer::getAnalysisUsage(AnalysisUsage &AU) const {
365 AU.setPreservesCFG();
366 AU.addRequired<AliasAnalysis>();
367 AU.addRequired<LiveIntervals>();
368 AU.addPreserved<LiveIntervals>();
369 AU.addRequired<LiveDebugVariables>();
370 AU.addPreserved<LiveDebugVariables>();
371 AU.addPreserved<SlotIndexes>();
372 AU.addRequired<MachineLoopInfo>();
373 AU.addPreserved<MachineLoopInfo>();
374 AU.addPreservedID(MachineDominatorsID);
375 MachineFunctionPass::getAnalysisUsage(AU);
378 void RegisterCoalescer::markAsJoined(MachineInstr *CopyMI) {
379 /// Joined copies are not deleted immediately, but kept in JoinedCopies.
380 JoinedCopies.insert(CopyMI);
382 /// Mark all register operands of CopyMI as <undef> so they won't affect dead
383 /// code elimination.
384 for (MachineInstr::mop_iterator I = CopyMI->operands_begin(),
385 E = CopyMI->operands_end(); I != E; ++I)
390 /// AdjustCopiesBackFrom - We found a non-trivially-coalescable copy with IntA
391 /// being the source and IntB being the dest, thus this defines a value number
392 /// in IntB. If the source value number (in IntA) is defined by a copy from B,
393 /// see if we can merge these two pieces of B into a single value number,
394 /// eliminating a copy. For example:
398 /// B1 = A3 <- this copy
400 /// In this case, B0 can be extended to where the B1 copy lives, allowing the B1
401 /// value number to be replaced with B0 (which simplifies the B liveinterval).
403 /// This returns true if an interval was modified.
405 bool RegisterCoalescer::AdjustCopiesBackFrom(const CoalescerPair &CP,
406 MachineInstr *CopyMI) {
407 // Bail if there is no dst interval - can happen when merging physical subreg
409 if (!LIS->hasInterval(CP.getDstReg()))
413 LIS->getInterval(CP.isFlipped() ? CP.getDstReg() : CP.getSrcReg());
415 LIS->getInterval(CP.isFlipped() ? CP.getSrcReg() : CP.getDstReg());
416 SlotIndex CopyIdx = LIS->getInstructionIndex(CopyMI).getRegSlot();
418 // BValNo is a value number in B that is defined by a copy from A. 'B3' in
419 // the example above.
420 LiveInterval::iterator BLR = IntB.FindLiveRangeContaining(CopyIdx);
421 if (BLR == IntB.end()) return false;
422 VNInfo *BValNo = BLR->valno;
424 // Get the location that B is defined at. Two options: either this value has
425 // an unknown definition point or it is defined at CopyIdx. If unknown, we
427 if (BValNo->def != CopyIdx) return false;
429 // AValNo is the value number in A that defines the copy, A3 in the example.
430 SlotIndex CopyUseIdx = CopyIdx.getRegSlot(true);
431 LiveInterval::iterator ALR = IntA.FindLiveRangeContaining(CopyUseIdx);
432 // The live range might not exist after fun with physreg coalescing.
433 if (ALR == IntA.end()) return false;
434 VNInfo *AValNo = ALR->valno;
436 // If AValNo is defined as a copy from IntB, we can potentially process this.
437 // Get the instruction that defines this value number.
438 MachineInstr *ACopyMI = LIS->getInstructionFromIndex(AValNo->def);
439 if (!CP.isCoalescable(ACopyMI))
442 // Get the LiveRange in IntB that this value number starts with.
443 LiveInterval::iterator ValLR =
444 IntB.FindLiveRangeContaining(AValNo->def.getPrevSlot());
445 if (ValLR == IntB.end())
448 // Make sure that the end of the live range is inside the same block as
450 MachineInstr *ValLREndInst =
451 LIS->getInstructionFromIndex(ValLR->end.getPrevSlot());
452 if (!ValLREndInst || ValLREndInst->getParent() != CopyMI->getParent())
455 // Okay, we now know that ValLR ends in the same block that the CopyMI
456 // live-range starts. If there are no intervening live ranges between them in
457 // IntB, we can merge them.
458 if (ValLR+1 != BLR) return false;
460 // If a live interval is a physical register, conservatively check if any
461 // of its aliases is overlapping the live interval of the virtual register.
462 // If so, do not coalesce.
463 if (TargetRegisterInfo::isPhysicalRegister(IntB.reg)) {
464 for (const uint16_t *AS = TRI->getAliasSet(IntB.reg); *AS; ++AS)
465 if (LIS->hasInterval(*AS) && IntA.overlaps(LIS->getInterval(*AS))) {
467 dbgs() << "\t\tInterfere with alias ";
468 LIS->getInterval(*AS).print(dbgs(), TRI);
475 dbgs() << "Extending: ";
476 IntB.print(dbgs(), TRI);
479 SlotIndex FillerStart = ValLR->end, FillerEnd = BLR->start;
480 // We are about to delete CopyMI, so need to remove it as the 'instruction
481 // that defines this value #'. Update the valnum with the new defining
483 BValNo->def = FillerStart;
485 // Okay, we can merge them. We need to insert a new liverange:
486 // [ValLR.end, BLR.begin) of either value number, then we merge the
487 // two value numbers.
488 IntB.addRange(LiveRange(FillerStart, FillerEnd, BValNo));
490 // If the IntB live range is assigned to a physical register, and if that
491 // physreg has sub-registers, update their live intervals as well.
492 if (TargetRegisterInfo::isPhysicalRegister(IntB.reg)) {
493 for (const unsigned *SR = TRI->getSubRegisters(IntB.reg); *SR; ++SR) {
494 if (!LIS->hasInterval(*SR))
496 LiveInterval &SRLI = LIS->getInterval(*SR);
497 SRLI.addRange(LiveRange(FillerStart, FillerEnd,
498 SRLI.getNextValue(FillerStart,
499 LIS->getVNInfoAllocator())));
503 // Okay, merge "B1" into the same value number as "B0".
504 if (BValNo != ValLR->valno) {
505 // If B1 is killed by a PHI, then the merged live range must also be killed
506 // by the same PHI, as B0 and B1 can not overlap.
507 bool HasPHIKill = BValNo->hasPHIKill();
508 IntB.MergeValueNumberInto(BValNo, ValLR->valno);
510 ValLR->valno->setHasPHIKill(true);
513 dbgs() << " result = ";
514 IntB.print(dbgs(), TRI);
518 // If the source instruction was killing the source register before the
519 // merge, unset the isKill marker given the live range has been extended.
520 int UIdx = ValLREndInst->findRegisterUseOperandIdx(IntB.reg, true);
522 ValLREndInst->getOperand(UIdx).setIsKill(false);
525 // Rewrite the copy. If the copy instruction was killing the destination
526 // register before the merge, find the last use and trim the live range. That
527 // will also add the isKill marker.
528 CopyMI->substituteRegister(IntA.reg, IntB.reg, CP.getSubIdx(),
530 if (ALR->end == CopyIdx)
531 LIS->shrinkToUses(&IntA);
537 /// HasOtherReachingDefs - Return true if there are definitions of IntB
538 /// other than BValNo val# that can reach uses of AValno val# of IntA.
539 bool RegisterCoalescer::HasOtherReachingDefs(LiveInterval &IntA,
543 for (LiveInterval::iterator AI = IntA.begin(), AE = IntA.end();
545 if (AI->valno != AValNo) continue;
546 LiveInterval::Ranges::iterator BI =
547 std::upper_bound(IntB.ranges.begin(), IntB.ranges.end(), AI->start);
548 if (BI != IntB.ranges.begin())
550 for (; BI != IntB.ranges.end() && AI->end >= BI->start; ++BI) {
551 if (BI->valno == BValNo)
553 if (BI->start <= AI->start && BI->end > AI->start)
555 if (BI->start > AI->start && BI->start < AI->end)
562 /// RemoveCopyByCommutingDef - We found a non-trivially-coalescable copy with
563 /// IntA being the source and IntB being the dest, thus this defines a value
564 /// number in IntB. If the source value number (in IntA) is defined by a
565 /// commutable instruction and its other operand is coalesced to the copy dest
566 /// register, see if we can transform the copy into a noop by commuting the
567 /// definition. For example,
569 /// A3 = op A2 B0<kill>
571 /// B1 = A3 <- this copy
573 /// = op A3 <- more uses
577 /// B2 = op B0 A2<kill>
579 /// B1 = B2 <- now an identify copy
581 /// = op B2 <- more uses
583 /// This returns true if an interval was modified.
585 bool RegisterCoalescer::RemoveCopyByCommutingDef(const CoalescerPair &CP,
586 MachineInstr *CopyMI) {
587 // FIXME: For now, only eliminate the copy by commuting its def when the
588 // source register is a virtual register. We want to guard against cases
589 // where the copy is a back edge copy and commuting the def lengthen the
590 // live interval of the source register to the entire loop.
591 if (CP.isPhys() && CP.isFlipped())
594 // Bail if there is no dst interval.
595 if (!LIS->hasInterval(CP.getDstReg()))
598 SlotIndex CopyIdx = LIS->getInstructionIndex(CopyMI).getRegSlot();
601 LIS->getInterval(CP.isFlipped() ? CP.getDstReg() : CP.getSrcReg());
603 LIS->getInterval(CP.isFlipped() ? CP.getSrcReg() : CP.getDstReg());
605 // BValNo is a value number in B that is defined by a copy from A. 'B3' in
606 // the example above.
607 VNInfo *BValNo = IntB.getVNInfoAt(CopyIdx);
608 if (!BValNo || BValNo->def != CopyIdx)
611 assert(BValNo->def == CopyIdx && "Copy doesn't define the value?");
613 // AValNo is the value number in A that defines the copy, A3 in the example.
614 VNInfo *AValNo = IntA.getVNInfoAt(CopyIdx.getRegSlot(true));
615 assert(AValNo && "COPY source not live");
617 // If other defs can reach uses of this def, then it's not safe to perform
619 if (AValNo->isPHIDef() || AValNo->isUnused() || AValNo->hasPHIKill())
621 MachineInstr *DefMI = LIS->getInstructionFromIndex(AValNo->def);
624 if (!DefMI->isCommutable())
626 // If DefMI is a two-address instruction then commuting it will change the
627 // destination register.
628 int DefIdx = DefMI->findRegisterDefOperandIdx(IntA.reg);
629 assert(DefIdx != -1);
631 if (!DefMI->isRegTiedToUseOperand(DefIdx, &UseOpIdx))
633 unsigned Op1, Op2, NewDstIdx;
634 if (!TII->findCommutedOpIndices(DefMI, Op1, Op2))
638 else if (Op2 == UseOpIdx)
643 MachineOperand &NewDstMO = DefMI->getOperand(NewDstIdx);
644 unsigned NewReg = NewDstMO.getReg();
645 if (NewReg != IntB.reg || !NewDstMO.isKill())
648 // Make sure there are no other definitions of IntB that would reach the
649 // uses which the new definition can reach.
650 if (HasOtherReachingDefs(IntA, IntB, AValNo, BValNo))
653 // Abort if the aliases of IntB.reg have values that are not simply the
654 // clobbers from the superreg.
655 if (TargetRegisterInfo::isPhysicalRegister(IntB.reg))
656 for (const uint16_t *AS = TRI->getAliasSet(IntB.reg); *AS; ++AS)
657 if (LIS->hasInterval(*AS) &&
658 HasOtherReachingDefs(IntA, LIS->getInterval(*AS), AValNo, 0))
661 // If some of the uses of IntA.reg is already coalesced away, return false.
662 // It's not possible to determine whether it's safe to perform the coalescing.
663 for (MachineRegisterInfo::use_nodbg_iterator UI =
664 MRI->use_nodbg_begin(IntA.reg),
665 UE = MRI->use_nodbg_end(); UI != UE; ++UI) {
666 MachineInstr *UseMI = &*UI;
667 SlotIndex UseIdx = LIS->getInstructionIndex(UseMI);
668 LiveInterval::iterator ULR = IntA.FindLiveRangeContaining(UseIdx);
669 if (ULR == IntA.end())
671 if (ULR->valno == AValNo && JoinedCopies.count(UseMI))
675 DEBUG(dbgs() << "\tRemoveCopyByCommutingDef: " << AValNo->def << '\t'
678 // At this point we have decided that it is legal to do this
679 // transformation. Start by commuting the instruction.
680 MachineBasicBlock *MBB = DefMI->getParent();
681 MachineInstr *NewMI = TII->commuteInstruction(DefMI);
684 if (TargetRegisterInfo::isVirtualRegister(IntA.reg) &&
685 TargetRegisterInfo::isVirtualRegister(IntB.reg) &&
686 !MRI->constrainRegClass(IntB.reg, MRI->getRegClass(IntA.reg)))
688 if (NewMI != DefMI) {
689 LIS->ReplaceMachineInstrInMaps(DefMI, NewMI);
690 MachineBasicBlock::iterator Pos = DefMI;
691 MBB->insert(Pos, NewMI);
694 unsigned OpIdx = NewMI->findRegisterUseOperandIdx(IntA.reg, false);
695 NewMI->getOperand(OpIdx).setIsKill();
697 // If ALR and BLR overlaps and end of BLR extends beyond end of ALR, e.g.
706 // Update uses of IntA of the specific Val# with IntB.
707 for (MachineRegisterInfo::use_iterator UI = MRI->use_begin(IntA.reg),
708 UE = MRI->use_end(); UI != UE;) {
709 MachineOperand &UseMO = UI.getOperand();
710 MachineInstr *UseMI = &*UI;
712 if (JoinedCopies.count(UseMI))
714 if (UseMI->isDebugValue()) {
715 // FIXME These don't have an instruction index. Not clear we have enough
716 // info to decide whether to do this replacement or not. For now do it.
717 UseMO.setReg(NewReg);
720 SlotIndex UseIdx = LIS->getInstructionIndex(UseMI).getRegSlot(true);
721 LiveInterval::iterator ULR = IntA.FindLiveRangeContaining(UseIdx);
722 if (ULR == IntA.end() || ULR->valno != AValNo)
724 if (TargetRegisterInfo::isPhysicalRegister(NewReg))
725 UseMO.substPhysReg(NewReg, *TRI);
727 UseMO.setReg(NewReg);
730 if (!UseMI->isCopy())
732 if (UseMI->getOperand(0).getReg() != IntB.reg ||
733 UseMI->getOperand(0).getSubReg())
736 // This copy will become a noop. If it's defining a new val#, merge it into
738 SlotIndex DefIdx = UseIdx.getRegSlot();
739 VNInfo *DVNI = IntB.getVNInfoAt(DefIdx);
742 DEBUG(dbgs() << "\t\tnoop: " << DefIdx << '\t' << *UseMI);
743 assert(DVNI->def == DefIdx);
744 BValNo = IntB.MergeValueNumberInto(BValNo, DVNI);
748 // Extend BValNo by merging in IntA live ranges of AValNo. Val# definition
750 VNInfo *ValNo = BValNo;
751 ValNo->def = AValNo->def;
752 for (LiveInterval::iterator AI = IntA.begin(), AE = IntA.end();
754 if (AI->valno != AValNo) continue;
755 IntB.addRange(LiveRange(AI->start, AI->end, ValNo));
757 DEBUG(dbgs() << "\t\textended: " << IntB << '\n');
759 IntA.removeValNo(AValNo);
760 DEBUG(dbgs() << "\t\ttrimmed: " << IntA << '\n');
765 /// ReMaterializeTrivialDef - If the source of a copy is defined by a trivial
766 /// computation, replace the copy by rematerialize the definition.
767 bool RegisterCoalescer::ReMaterializeTrivialDef(LiveInterval &SrcInt,
770 MachineInstr *CopyMI) {
771 SlotIndex CopyIdx = LIS->getInstructionIndex(CopyMI).getRegSlot(true);
772 LiveInterval::iterator SrcLR = SrcInt.FindLiveRangeContaining(CopyIdx);
773 assert(SrcLR != SrcInt.end() && "Live range not found!");
774 VNInfo *ValNo = SrcLR->valno;
775 if (ValNo->isPHIDef() || ValNo->isUnused())
777 MachineInstr *DefMI = LIS->getInstructionFromIndex(ValNo->def);
780 assert(DefMI && "Defining instruction disappeared");
781 if (!DefMI->isAsCheapAsAMove())
783 if (!TII->isTriviallyReMaterializable(DefMI, AA))
785 bool SawStore = false;
786 if (!DefMI->isSafeToMove(TII, AA, SawStore))
788 const MCInstrDesc &MCID = DefMI->getDesc();
789 if (MCID.getNumDefs() != 1)
791 if (!DefMI->isImplicitDef()) {
792 // Make sure the copy destination register class fits the instruction
793 // definition register class. The mismatch can happen as a result of earlier
794 // extract_subreg, insert_subreg, subreg_to_reg coalescing.
795 const TargetRegisterClass *RC = TII->getRegClass(MCID, 0, TRI);
796 if (TargetRegisterInfo::isVirtualRegister(DstReg)) {
797 if (MRI->getRegClass(DstReg) != RC)
799 } else if (!RC->contains(DstReg))
803 MachineBasicBlock *MBB = CopyMI->getParent();
804 MachineBasicBlock::iterator MII =
805 llvm::next(MachineBasicBlock::iterator(CopyMI));
806 TII->reMaterialize(*MBB, MII, DstReg, 0, DefMI, *TRI);
807 MachineInstr *NewMI = prior(MII);
809 // NewMI may have dead implicit defs (E.g. EFLAGS for MOV<bits>r0 on X86).
810 // We need to remember these so we can add intervals once we insert
811 // NewMI into SlotIndexes.
812 SmallVector<unsigned, 4> NewMIImplDefs;
813 for (unsigned i = NewMI->getDesc().getNumOperands(),
814 e = NewMI->getNumOperands(); i != e; ++i) {
815 MachineOperand &MO = NewMI->getOperand(i);
817 assert(MO.isDef() && MO.isImplicit() && MO.isDead() &&
818 TargetRegisterInfo::isPhysicalRegister(MO.getReg()));
819 NewMIImplDefs.push_back(MO.getReg());
823 // CopyMI may have implicit operands, transfer them over to the newly
824 // rematerialized instruction. And update implicit def interval valnos.
825 for (unsigned i = CopyMI->getDesc().getNumOperands(),
826 e = CopyMI->getNumOperands(); i != e; ++i) {
827 MachineOperand &MO = CopyMI->getOperand(i);
829 assert(MO.isImplicit() && "No explicit operands after implict operands.");
830 // Discard VReg implicit defs.
831 if (TargetRegisterInfo::isPhysicalRegister(MO.getReg())) {
832 NewMI->addOperand(MO);
837 LIS->ReplaceMachineInstrInMaps(CopyMI, NewMI);
839 SlotIndex NewMIIdx = LIS->getInstructionIndex(NewMI);
840 for (unsigned i = 0, e = NewMIImplDefs.size(); i != e; ++i) {
841 unsigned reg = NewMIImplDefs[i];
842 LiveInterval &li = LIS->getInterval(reg);
843 VNInfo *DeadDefVN = li.getNextValue(NewMIIdx.getRegSlot(),
844 LIS->getVNInfoAllocator());
845 LiveRange lr(NewMIIdx.getRegSlot(), NewMIIdx.getDeadSlot(), DeadDefVN);
849 CopyMI->eraseFromParent();
850 ReMatCopies.insert(CopyMI);
851 ReMatDefs.insert(DefMI);
852 DEBUG(dbgs() << "Remat: " << *NewMI);
855 // The source interval can become smaller because we removed a use.
857 LIS->shrinkToUses(&SrcInt);
862 /// eliminateUndefCopy - ProcessImpicitDefs may leave some copies of <undef>
863 /// values, it only removes local variables. When we have a copy like:
865 /// %vreg1 = COPY %vreg2<undef>
867 /// We delete the copy and remove the corresponding value number from %vreg1.
868 /// Any uses of that value number are marked as <undef>.
869 bool RegisterCoalescer::eliminateUndefCopy(MachineInstr *CopyMI,
870 const CoalescerPair &CP) {
871 SlotIndex Idx = LIS->getInstructionIndex(CopyMI);
872 LiveInterval *SrcInt = &LIS->getInterval(CP.getSrcReg());
873 if (SrcInt->liveAt(Idx))
875 LiveInterval *DstInt = &LIS->getInterval(CP.getDstReg());
876 if (DstInt->liveAt(Idx))
879 // No intervals are live-in to CopyMI - it is undef.
884 VNInfo *DeadVNI = DstInt->getVNInfoAt(Idx.getRegSlot());
885 assert(DeadVNI && "No value defined in DstInt");
886 DstInt->removeValNo(DeadVNI);
888 // Find new undef uses.
889 for (MachineRegisterInfo::reg_nodbg_iterator
890 I = MRI->reg_nodbg_begin(DstInt->reg), E = MRI->reg_nodbg_end();
892 MachineOperand &MO = I.getOperand();
893 if (MO.isDef() || MO.isUndef())
895 MachineInstr *MI = MO.getParent();
896 SlotIndex Idx = LIS->getInstructionIndex(MI);
897 if (DstInt->liveAt(Idx))
900 DEBUG(dbgs() << "\tnew undef: " << Idx << '\t' << *MI);
905 /// UpdateRegDefsUses - Replace all defs and uses of SrcReg to DstReg and
906 /// update the subregister number if it is not zero. If DstReg is a
907 /// physical register and the existing subregister number of the def / use
908 /// being updated is not zero, make sure to set it to the correct physical
911 RegisterCoalescer::UpdateRegDefsUses(const CoalescerPair &CP) {
912 bool DstIsPhys = CP.isPhys();
913 unsigned SrcReg = CP.getSrcReg();
914 unsigned DstReg = CP.getDstReg();
915 unsigned SubIdx = CP.getSubIdx();
917 // Update LiveDebugVariables.
918 LDV->renameRegister(SrcReg, DstReg, SubIdx);
920 for (MachineRegisterInfo::reg_iterator I = MRI->reg_begin(SrcReg);
921 MachineInstr *UseMI = I.skipInstruction();) {
922 // A PhysReg copy that won't be coalesced can perhaps be rematerialized
925 if (UseMI->isFullCopy() &&
926 UseMI->getOperand(1).getReg() == SrcReg &&
927 UseMI->getOperand(0).getReg() != SrcReg &&
928 UseMI->getOperand(0).getReg() != DstReg &&
929 !JoinedCopies.count(UseMI) &&
930 ReMaterializeTrivialDef(LIS->getInterval(SrcReg), false,
931 UseMI->getOperand(0).getReg(), UseMI))
935 SmallVector<unsigned,8> Ops;
937 tie(Reads, Writes) = UseMI->readsWritesVirtualRegister(SrcReg, &Ops);
938 bool Kills = false, Deads = false;
940 // Replace SrcReg with DstReg in all UseMI operands.
941 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
942 MachineOperand &MO = UseMI->getOperand(Ops[i]);
943 Kills |= MO.isKill();
944 Deads |= MO.isDead();
946 // Make sure we don't create read-modify-write defs accidentally. We
947 // assume here that a SrcReg def cannot be joined into a live DstReg. If
948 // RegisterCoalescer starts tracking partially live registers, we will
949 // need to check the actual LiveInterval to determine if DstReg is live
951 if (SubIdx && !Reads)
955 MO.substPhysReg(DstReg, *TRI);
957 MO.substVirtReg(DstReg, SubIdx, *TRI);
960 // This instruction is a copy that will be removed.
961 if (JoinedCopies.count(UseMI))
965 // If UseMI was a simple SrcReg def, make sure we didn't turn it into a
966 // read-modify-write of DstReg.
968 UseMI->addRegisterDead(DstReg, TRI);
969 else if (!Reads && Writes)
970 UseMI->addRegisterDefined(DstReg, TRI);
972 // Kill flags apply to the whole physical register.
973 if (DstIsPhys && Kills)
974 UseMI->addRegisterKilled(DstReg, TRI);
978 dbgs() << "\t\tupdated: ";
979 if (!UseMI->isDebugValue())
980 dbgs() << LIS->getInstructionIndex(UseMI) << "\t";
986 /// removeIntervalIfEmpty - Check if the live interval of a physical register
987 /// is empty, if so remove it and also remove the empty intervals of its
988 /// sub-registers. Return true if live interval is removed.
989 static bool removeIntervalIfEmpty(LiveInterval &li, LiveIntervals *LIS,
990 const TargetRegisterInfo *TRI) {
992 if (TargetRegisterInfo::isPhysicalRegister(li.reg))
993 for (const unsigned* SR = TRI->getSubRegisters(li.reg); *SR; ++SR) {
994 if (!LIS->hasInterval(*SR))
996 LiveInterval &sli = LIS->getInterval(*SR);
998 LIS->removeInterval(*SR);
1000 LIS->removeInterval(li.reg);
1006 /// RemoveDeadDef - If a def of a live interval is now determined dead, remove
1007 /// the val# it defines. If the live interval becomes empty, remove it as well.
1008 bool RegisterCoalescer::RemoveDeadDef(LiveInterval &li,
1009 MachineInstr *DefMI) {
1010 SlotIndex DefIdx = LIS->getInstructionIndex(DefMI).getRegSlot();
1011 LiveInterval::iterator MLR = li.FindLiveRangeContaining(DefIdx);
1012 if (DefIdx != MLR->valno->def)
1014 li.removeValNo(MLR->valno);
1015 return removeIntervalIfEmpty(li, LIS, TRI);
1018 /// shouldJoinPhys - Return true if a copy involving a physreg should be joined.
1019 /// We need to be careful about coalescing a source physical register with a
1020 /// virtual register. Once the coalescing is done, it cannot be broken and these
1021 /// are not spillable! If the destination interval uses are far away, think
1022 /// twice about coalescing them!
1023 bool RegisterCoalescer::shouldJoinPhys(CoalescerPair &CP) {
1024 bool Allocatable = LIS->isAllocatable(CP.getDstReg());
1025 LiveInterval &JoinVInt = LIS->getInterval(CP.getSrcReg());
1027 /// Always join simple intervals that are defined by a single copy from a
1028 /// reserved register. This doesn't increase register pressure, so it is
1029 /// always beneficial.
1030 if (!Allocatable && CP.isFlipped() && JoinVInt.containsOneValue())
1033 if (!EnablePhysicalJoin) {
1034 DEBUG(dbgs() << "\tPhysreg joins disabled.\n");
1038 // Only coalesce to allocatable physreg, we don't want to risk modifying
1039 // reserved registers.
1041 DEBUG(dbgs() << "\tRegister is an unallocatable physreg.\n");
1042 return false; // Not coalescable.
1045 // Don't join with physregs that have a ridiculous number of live
1046 // ranges. The data structure performance is really bad when that
1048 if (LIS->hasInterval(CP.getDstReg()) &&
1049 LIS->getInterval(CP.getDstReg()).ranges.size() > 1000) {
1052 << "\tPhysical register live interval too complicated, abort!\n");
1056 // FIXME: Why are we skipping this test for partial copies?
1057 // CodeGen/X86/phys_subreg_coalesce-3.ll needs it.
1058 if (!CP.isPartial()) {
1059 const TargetRegisterClass *RC = MRI->getRegClass(CP.getSrcReg());
1060 unsigned Threshold = RegClassInfo.getNumAllocatableRegs(RC) * 2;
1061 unsigned Length = LIS->getApproximateInstructionCount(JoinVInt);
1062 if (Length > Threshold) {
1064 DEBUG(dbgs() << "\tMay tie down a physical register, abort!\n");
1071 /// isWinToJoinCrossClass - Return true if it's profitable to coalesce
1072 /// two virtual registers from different register classes.
1074 RegisterCoalescer::isWinToJoinCrossClass(unsigned SrcReg,
1076 const TargetRegisterClass *SrcRC,
1077 const TargetRegisterClass *DstRC,
1078 const TargetRegisterClass *NewRC) {
1079 unsigned NewRCCount = RegClassInfo.getNumAllocatableRegs(NewRC);
1080 // This heuristics is good enough in practice, but it's obviously not *right*.
1081 // 4 is a magic number that works well enough for x86, ARM, etc. It filter
1082 // out all but the most restrictive register classes.
1083 if (NewRCCount > 4 ||
1084 // Early exit if the function is fairly small, coalesce aggressively if
1085 // that's the case. For really special register classes with 3 or
1086 // fewer registers, be a bit more careful.
1087 (LIS->getFuncInstructionCount() / NewRCCount) < 8)
1089 LiveInterval &SrcInt = LIS->getInterval(SrcReg);
1090 LiveInterval &DstInt = LIS->getInterval(DstReg);
1091 unsigned SrcSize = LIS->getApproximateInstructionCount(SrcInt);
1092 unsigned DstSize = LIS->getApproximateInstructionCount(DstInt);
1094 // Coalesce aggressively if the intervals are small compared to the number of
1095 // registers in the new class. The number 4 is fairly arbitrary, chosen to be
1096 // less aggressive than the 8 used for the whole function size.
1097 const unsigned ThresSize = 4 * NewRCCount;
1098 if (SrcSize <= ThresSize && DstSize <= ThresSize)
1101 // Estimate *register use density*. If it doubles or more, abort.
1102 unsigned SrcUses = std::distance(MRI->use_nodbg_begin(SrcReg),
1103 MRI->use_nodbg_end());
1104 unsigned DstUses = std::distance(MRI->use_nodbg_begin(DstReg),
1105 MRI->use_nodbg_end());
1106 unsigned NewUses = SrcUses + DstUses;
1107 unsigned NewSize = SrcSize + DstSize;
1108 if (SrcRC != NewRC && SrcSize > ThresSize) {
1109 unsigned SrcRCCount = RegClassInfo.getNumAllocatableRegs(SrcRC);
1110 if (NewUses*SrcSize*SrcRCCount > 2*SrcUses*NewSize*NewRCCount)
1113 if (DstRC != NewRC && DstSize > ThresSize) {
1114 unsigned DstRCCount = RegClassInfo.getNumAllocatableRegs(DstRC);
1115 if (NewUses*DstSize*DstRCCount > 2*DstUses*NewSize*NewRCCount)
1122 /// JoinCopy - Attempt to join intervals corresponding to SrcReg/DstReg,
1123 /// which are the src/dst of the copy instruction CopyMI. This returns true
1124 /// if the copy was successfully coalesced away. If it is not currently
1125 /// possible to coalesce this interval, but it may be possible if other
1126 /// things get coalesced, then it returns true by reference in 'Again'.
1127 bool RegisterCoalescer::JoinCopy(MachineInstr *CopyMI, bool &Again) {
1130 if (JoinedCopies.count(CopyMI) || ReMatCopies.count(CopyMI))
1131 return false; // Already done.
1133 DEBUG(dbgs() << LIS->getInstructionIndex(CopyMI) << '\t' << *CopyMI);
1135 CoalescerPair CP(*TII, *TRI);
1136 if (!CP.setRegisters(CopyMI)) {
1137 DEBUG(dbgs() << "\tNot coalescable.\n");
1141 // If they are already joined we continue.
1142 if (CP.getSrcReg() == CP.getDstReg()) {
1143 markAsJoined(CopyMI);
1144 DEBUG(dbgs() << "\tCopy already coalesced.\n");
1145 return false; // Not coalescable.
1148 // Eliminate undefs.
1149 if (!CP.isPhys() && eliminateUndefCopy(CopyMI, CP)) {
1150 markAsJoined(CopyMI);
1151 DEBUG(dbgs() << "\tEliminated copy of <undef> value.\n");
1152 return false; // Not coalescable.
1155 DEBUG(dbgs() << "\tConsidering merging " << PrintReg(CP.getSrcReg(), TRI)
1156 << " with " << PrintReg(CP.getDstReg(), TRI, CP.getSubIdx())
1159 // Enforce policies.
1161 if (!shouldJoinPhys(CP)) {
1162 // Before giving up coalescing, if definition of source is defined by
1163 // trivial computation, try rematerializing it.
1164 if (!CP.isFlipped() &&
1165 ReMaterializeTrivialDef(LIS->getInterval(CP.getSrcReg()), true,
1166 CP.getDstReg(), CopyMI))
1171 // Avoid constraining virtual register regclass too much.
1172 if (CP.isCrossClass()) {
1173 DEBUG(dbgs() << "\tCross-class to " << CP.getNewRC()->getName() << ".\n");
1174 if (DisableCrossClassJoin) {
1175 DEBUG(dbgs() << "\tCross-class joins disabled.\n");
1178 if (!isWinToJoinCrossClass(CP.getSrcReg(), CP.getDstReg(),
1179 MRI->getRegClass(CP.getSrcReg()),
1180 MRI->getRegClass(CP.getDstReg()),
1182 DEBUG(dbgs() << "\tAvoid coalescing to constrained register class.\n");
1183 Again = true; // May be possible to coalesce later.
1188 // When possible, let DstReg be the larger interval.
1189 if (!CP.getSubIdx() && LIS->getInterval(CP.getSrcReg()).ranges.size() >
1190 LIS->getInterval(CP.getDstReg()).ranges.size())
1194 // Okay, attempt to join these two intervals. On failure, this returns false.
1195 // Otherwise, if one of the intervals being joined is a physreg, this method
1196 // always canonicalizes DstInt to be it. The output "SrcInt" will not have
1197 // been modified, so we can use this information below to update aliases.
1198 if (!JoinIntervals(CP)) {
1199 // Coalescing failed.
1201 // If definition of source is defined by trivial computation, try
1202 // rematerializing it.
1203 if (!CP.isFlipped() &&
1204 ReMaterializeTrivialDef(LIS->getInterval(CP.getSrcReg()), true,
1205 CP.getDstReg(), CopyMI))
1208 // If we can eliminate the copy without merging the live ranges, do so now.
1209 if (!CP.isPartial()) {
1210 if (AdjustCopiesBackFrom(CP, CopyMI) ||
1211 RemoveCopyByCommutingDef(CP, CopyMI)) {
1212 markAsJoined(CopyMI);
1213 DEBUG(dbgs() << "\tTrivial!\n");
1218 // Otherwise, we are unable to join the intervals.
1219 DEBUG(dbgs() << "\tInterference!\n");
1220 Again = true; // May be possible to coalesce later.
1224 // Coalescing to a virtual register that is of a sub-register class of the
1225 // other. Make sure the resulting register is set to the right register class.
1226 if (CP.isCrossClass()) {
1228 MRI->setRegClass(CP.getDstReg(), CP.getNewRC());
1231 // Remember to delete the copy instruction.
1232 markAsJoined(CopyMI);
1234 UpdateRegDefsUses(CP);
1236 // If we have extended the live range of a physical register, make sure we
1237 // update live-in lists as well.
1239 SmallVector<MachineBasicBlock*, 16> BlockSeq;
1240 // JoinIntervals invalidates the VNInfos in SrcInt, but we only need the
1241 // ranges for this, and they are preserved.
1242 LiveInterval &SrcInt = LIS->getInterval(CP.getSrcReg());
1243 for (LiveInterval::const_iterator I = SrcInt.begin(), E = SrcInt.end();
1245 LIS->findLiveInMBBs(I->start, I->end, BlockSeq);
1246 for (unsigned idx = 0, size = BlockSeq.size(); idx != size; ++idx) {
1247 MachineBasicBlock &block = *BlockSeq[idx];
1248 if (!block.isLiveIn(CP.getDstReg()))
1249 block.addLiveIn(CP.getDstReg());
1255 // SrcReg is guaranteed to be the register whose live interval that is
1257 LIS->removeInterval(CP.getSrcReg());
1259 // Update regalloc hint.
1260 TRI->UpdateRegAllocHint(CP.getSrcReg(), CP.getDstReg(), *MF);
1263 LiveInterval &DstInt = LIS->getInterval(CP.getDstReg());
1264 dbgs() << "\tJoined. Result = ";
1265 DstInt.print(dbgs(), TRI);
1273 /// ComputeUltimateVN - Assuming we are going to join two live intervals,
1274 /// compute what the resultant value numbers for each value in the input two
1275 /// ranges will be. This is complicated by copies between the two which can
1276 /// and will commonly cause multiple value numbers to be merged into one.
1278 /// VN is the value number that we're trying to resolve. InstDefiningValue
1279 /// keeps track of the new InstDefiningValue assignment for the result
1280 /// LiveInterval. ThisFromOther/OtherFromThis are sets that keep track of
1281 /// whether a value in this or other is a copy from the opposite set.
1282 /// ThisValNoAssignments/OtherValNoAssignments keep track of value #'s that have
1283 /// already been assigned.
1285 /// ThisFromOther[x] - If x is defined as a copy from the other interval, this
1286 /// contains the value number the copy is from.
1288 static unsigned ComputeUltimateVN(VNInfo *VNI,
1289 SmallVector<VNInfo*, 16> &NewVNInfo,
1290 DenseMap<VNInfo*, VNInfo*> &ThisFromOther,
1291 DenseMap<VNInfo*, VNInfo*> &OtherFromThis,
1292 SmallVector<int, 16> &ThisValNoAssignments,
1293 SmallVector<int, 16> &OtherValNoAssignments) {
1294 unsigned VN = VNI->id;
1296 // If the VN has already been computed, just return it.
1297 if (ThisValNoAssignments[VN] >= 0)
1298 return ThisValNoAssignments[VN];
1299 assert(ThisValNoAssignments[VN] != -2 && "Cyclic value numbers");
1301 // If this val is not a copy from the other val, then it must be a new value
1302 // number in the destination.
1303 DenseMap<VNInfo*, VNInfo*>::iterator I = ThisFromOther.find(VNI);
1304 if (I == ThisFromOther.end()) {
1305 NewVNInfo.push_back(VNI);
1306 return ThisValNoAssignments[VN] = NewVNInfo.size()-1;
1308 VNInfo *OtherValNo = I->second;
1310 // Otherwise, this *is* a copy from the RHS. If the other side has already
1311 // been computed, return it.
1312 if (OtherValNoAssignments[OtherValNo->id] >= 0)
1313 return ThisValNoAssignments[VN] = OtherValNoAssignments[OtherValNo->id];
1315 // Mark this value number as currently being computed, then ask what the
1316 // ultimate value # of the other value is.
1317 ThisValNoAssignments[VN] = -2;
1318 unsigned UltimateVN =
1319 ComputeUltimateVN(OtherValNo, NewVNInfo, OtherFromThis, ThisFromOther,
1320 OtherValNoAssignments, ThisValNoAssignments);
1321 return ThisValNoAssignments[VN] = UltimateVN;
1325 // Find out if we have something like
1328 // if so, we can pretend this is actually
1331 // which allows us to coalesce A and B.
1332 // VNI is the definition of B. LR is the life range of A that includes
1333 // the slot just before B. If we return true, we add "B = X" to DupCopies.
1334 // This implies that A dominates B.
1335 static bool RegistersDefinedFromSameValue(LiveIntervals &li,
1336 const TargetRegisterInfo &tri,
1340 SmallVector<MachineInstr*, 8> &DupCopies) {
1341 // FIXME: This is very conservative. For example, we don't handle
1342 // physical registers.
1344 MachineInstr *MI = li.getInstructionFromIndex(VNI->def);
1346 if (!MI || !MI->isFullCopy() || CP.isPartial() || CP.isPhys())
1349 unsigned Dst = MI->getOperand(0).getReg();
1350 unsigned Src = MI->getOperand(1).getReg();
1352 if (!TargetRegisterInfo::isVirtualRegister(Src) ||
1353 !TargetRegisterInfo::isVirtualRegister(Dst))
1356 unsigned A = CP.getDstReg();
1357 unsigned B = CP.getSrcReg();
1363 VNInfo *Other = LR->valno;
1364 const MachineInstr *OtherMI = li.getInstructionFromIndex(Other->def);
1366 if (!OtherMI || !OtherMI->isFullCopy())
1369 unsigned OtherDst = OtherMI->getOperand(0).getReg();
1370 unsigned OtherSrc = OtherMI->getOperand(1).getReg();
1372 if (!TargetRegisterInfo::isVirtualRegister(OtherSrc) ||
1373 !TargetRegisterInfo::isVirtualRegister(OtherDst))
1376 assert(OtherDst == B);
1378 if (Src != OtherSrc)
1381 // If the copies use two different value numbers of X, we cannot merge
1383 LiveInterval &SrcInt = li.getInterval(Src);
1384 // getVNInfoBefore returns NULL for undef copies. In this case, the
1385 // optimization is still safe.
1386 if (SrcInt.getVNInfoBefore(Other->def) != SrcInt.getVNInfoBefore(VNI->def))
1389 DupCopies.push_back(MI);
1394 /// JoinIntervals - Attempt to join these two intervals. On failure, this
1396 bool RegisterCoalescer::JoinIntervals(CoalescerPair &CP) {
1397 LiveInterval &RHS = LIS->getInterval(CP.getSrcReg());
1398 DEBUG({ dbgs() << "\t\tRHS = "; RHS.print(dbgs(), TRI); dbgs() << "\n"; });
1400 // If a live interval is a physical register, check for interference with any
1401 // aliases. The interference check implemented here is a bit more conservative
1402 // than the full interfeence check below. We allow overlapping live ranges
1403 // only when one is a copy of the other.
1405 // Optimization for reserved registers like ESP.
1406 // We can only merge with a reserved physreg if RHS has a single value that
1407 // is a copy of CP.DstReg(). The live range of the reserved register will
1408 // look like a set of dead defs - we don't properly track the live range of
1409 // reserved registers.
1410 if (RegClassInfo.isReserved(CP.getDstReg())) {
1411 assert(CP.isFlipped() && RHS.containsOneValue() &&
1412 "Invalid join with reserved register");
1413 // Deny any overlapping intervals. This depends on all the reserved
1414 // register live ranges to look like dead defs.
1415 for (const uint16_t *AS = TRI->getOverlaps(CP.getDstReg()); *AS; ++AS) {
1416 if (!LIS->hasInterval(*AS)) {
1417 // Make sure at least DstReg itself exists before attempting a join.
1418 if (*AS == CP.getDstReg())
1419 LIS->getOrCreateInterval(CP.getDstReg());
1422 if (RHS.overlaps(LIS->getInterval(*AS))) {
1423 DEBUG(dbgs() << "\t\tInterference: " << PrintReg(*AS, TRI) << '\n');
1427 // Skip any value computations, we are not adding new values to the
1428 // reserved register. Also skip merging the live ranges, the reserved
1429 // register live range doesn't need to be accurate as long as all the
1434 // Check if a register mask clobbers DstReg.
1435 BitVector UsableRegs;
1436 if (LIS->checkRegMaskInterference(RHS, UsableRegs) &&
1437 !UsableRegs.test(CP.getDstReg())) {
1438 DEBUG(dbgs() << "\t\tRegister mask interference.\n");
1442 for (const uint16_t *AS = TRI->getAliasSet(CP.getDstReg()); *AS; ++AS){
1443 if (!LIS->hasInterval(*AS))
1445 const LiveInterval &LHS = LIS->getInterval(*AS);
1446 LiveInterval::const_iterator LI = LHS.begin();
1447 for (LiveInterval::const_iterator RI = RHS.begin(), RE = RHS.end();
1449 LI = std::lower_bound(LI, LHS.end(), RI->start);
1450 // Does LHS have an overlapping live range starting before RI?
1451 if ((LI != LHS.begin() && LI[-1].end > RI->start) &&
1452 (RI->start != RI->valno->def ||
1453 !CP.isCoalescable(LIS->getInstructionFromIndex(RI->start)))) {
1455 dbgs() << "\t\tInterference from alias: ";
1456 LHS.print(dbgs(), TRI);
1457 dbgs() << "\n\t\tOverlap at " << RI->start << " and no copy.\n";
1462 // Check that LHS ranges beginning in this range are copies.
1463 for (; LI != LHS.end() && LI->start < RI->end; ++LI) {
1464 if (LI->start != LI->valno->def ||
1465 !CP.isCoalescable(LIS->getInstructionFromIndex(LI->start))) {
1467 dbgs() << "\t\tInterference from alias: ";
1468 LHS.print(dbgs(), TRI);
1469 dbgs() << "\n\t\tDef at " << LI->start << " is not a copy.\n";
1478 // Compute the final value assignment, assuming that the live ranges can be
1480 SmallVector<int, 16> LHSValNoAssignments;
1481 SmallVector<int, 16> RHSValNoAssignments;
1482 DenseMap<VNInfo*, VNInfo*> LHSValsDefinedFromRHS;
1483 DenseMap<VNInfo*, VNInfo*> RHSValsDefinedFromLHS;
1484 SmallVector<VNInfo*, 16> NewVNInfo;
1486 SmallVector<MachineInstr*, 8> DupCopies;
1488 LiveInterval &LHS = LIS->getOrCreateInterval(CP.getDstReg());
1489 DEBUG({ dbgs() << "\t\tLHS = "; LHS.print(dbgs(), TRI); dbgs() << "\n"; });
1491 // Loop over the value numbers of the LHS, seeing if any are defined from
1493 for (LiveInterval::vni_iterator i = LHS.vni_begin(), e = LHS.vni_end();
1496 if (VNI->isUnused() || VNI->isPHIDef())
1498 MachineInstr *MI = LIS->getInstructionFromIndex(VNI->def);
1499 assert(MI && "Missing def");
1500 if (!MI->isCopyLike()) // Src not defined by a copy?
1503 // Figure out the value # from the RHS.
1504 LiveRange *lr = RHS.getLiveRangeContaining(VNI->def.getPrevSlot());
1505 // The copy could be to an aliased physreg.
1508 // DstReg is known to be a register in the LHS interval. If the src is
1509 // from the RHS interval, we can use its value #.
1510 if (!CP.isCoalescable(MI) &&
1511 !RegistersDefinedFromSameValue(*LIS, *TRI, CP, VNI, lr, DupCopies))
1514 LHSValsDefinedFromRHS[VNI] = lr->valno;
1517 // Loop over the value numbers of the RHS, seeing if any are defined from
1519 for (LiveInterval::vni_iterator i = RHS.vni_begin(), e = RHS.vni_end();
1522 if (VNI->isUnused() || VNI->isPHIDef())
1524 MachineInstr *MI = LIS->getInstructionFromIndex(VNI->def);
1525 assert(MI && "Missing def");
1526 if (!MI->isCopyLike()) // Src not defined by a copy?
1529 // Figure out the value # from the LHS.
1530 LiveRange *lr = LHS.getLiveRangeContaining(VNI->def.getPrevSlot());
1531 // The copy could be to an aliased physreg.
1534 // DstReg is known to be a register in the RHS interval. If the src is
1535 // from the LHS interval, we can use its value #.
1536 if (!CP.isCoalescable(MI) &&
1537 !RegistersDefinedFromSameValue(*LIS, *TRI, CP, VNI, lr, DupCopies))
1540 RHSValsDefinedFromLHS[VNI] = lr->valno;
1543 LHSValNoAssignments.resize(LHS.getNumValNums(), -1);
1544 RHSValNoAssignments.resize(RHS.getNumValNums(), -1);
1545 NewVNInfo.reserve(LHS.getNumValNums() + RHS.getNumValNums());
1547 for (LiveInterval::vni_iterator i = LHS.vni_begin(), e = LHS.vni_end();
1550 unsigned VN = VNI->id;
1551 if (LHSValNoAssignments[VN] >= 0 || VNI->isUnused())
1553 ComputeUltimateVN(VNI, NewVNInfo,
1554 LHSValsDefinedFromRHS, RHSValsDefinedFromLHS,
1555 LHSValNoAssignments, RHSValNoAssignments);
1557 for (LiveInterval::vni_iterator i = RHS.vni_begin(), e = RHS.vni_end();
1560 unsigned VN = VNI->id;
1561 if (RHSValNoAssignments[VN] >= 0 || VNI->isUnused())
1563 // If this value number isn't a copy from the LHS, it's a new number.
1564 if (RHSValsDefinedFromLHS.find(VNI) == RHSValsDefinedFromLHS.end()) {
1565 NewVNInfo.push_back(VNI);
1566 RHSValNoAssignments[VN] = NewVNInfo.size()-1;
1570 ComputeUltimateVN(VNI, NewVNInfo,
1571 RHSValsDefinedFromLHS, LHSValsDefinedFromRHS,
1572 RHSValNoAssignments, LHSValNoAssignments);
1575 // Armed with the mappings of LHS/RHS values to ultimate values, walk the
1576 // interval lists to see if these intervals are coalescable.
1577 LiveInterval::const_iterator I = LHS.begin();
1578 LiveInterval::const_iterator IE = LHS.end();
1579 LiveInterval::const_iterator J = RHS.begin();
1580 LiveInterval::const_iterator JE = RHS.end();
1582 // Skip ahead until the first place of potential sharing.
1583 if (I != IE && J != JE) {
1584 if (I->start < J->start) {
1585 I = std::upper_bound(I, IE, J->start);
1586 if (I != LHS.begin()) --I;
1587 } else if (J->start < I->start) {
1588 J = std::upper_bound(J, JE, I->start);
1589 if (J != RHS.begin()) --J;
1593 while (I != IE && J != JE) {
1594 // Determine if these two live ranges overlap.
1596 if (I->start < J->start) {
1597 Overlaps = I->end > J->start;
1599 Overlaps = J->end > I->start;
1602 // If so, check value # info to determine if they are really different.
1604 // If the live range overlap will map to the same value number in the
1605 // result liverange, we can still coalesce them. If not, we can't.
1606 if (LHSValNoAssignments[I->valno->id] !=
1607 RHSValNoAssignments[J->valno->id])
1611 if (I->end < J->end)
1617 // Update kill info. Some live ranges are extended due to copy coalescing.
1618 for (DenseMap<VNInfo*, VNInfo*>::iterator I = LHSValsDefinedFromRHS.begin(),
1619 E = LHSValsDefinedFromRHS.end(); I != E; ++I) {
1620 VNInfo *VNI = I->first;
1621 unsigned LHSValID = LHSValNoAssignments[VNI->id];
1622 if (VNI->hasPHIKill())
1623 NewVNInfo[LHSValID]->setHasPHIKill(true);
1626 // Update kill info. Some live ranges are extended due to copy coalescing.
1627 for (DenseMap<VNInfo*, VNInfo*>::iterator I = RHSValsDefinedFromLHS.begin(),
1628 E = RHSValsDefinedFromLHS.end(); I != E; ++I) {
1629 VNInfo *VNI = I->first;
1630 unsigned RHSValID = RHSValNoAssignments[VNI->id];
1631 if (VNI->hasPHIKill())
1632 NewVNInfo[RHSValID]->setHasPHIKill(true);
1635 if (LHSValNoAssignments.empty())
1636 LHSValNoAssignments.push_back(-1);
1637 if (RHSValNoAssignments.empty())
1638 RHSValNoAssignments.push_back(-1);
1640 SmallVector<unsigned, 8> SourceRegisters;
1641 for (SmallVector<MachineInstr*, 8>::iterator I = DupCopies.begin(),
1642 E = DupCopies.end(); I != E; ++I) {
1643 MachineInstr *MI = *I;
1645 // We have pretended that the assignment to B in
1648 // was actually a copy from A. Now that we decided to coalesce A and B,
1649 // transform the code into
1652 // and mark the X as coalesced to keep the illusion.
1653 unsigned Src = MI->getOperand(1).getReg();
1654 SourceRegisters.push_back(Src);
1655 MI->getOperand(0).substVirtReg(Src, 0, *TRI);
1660 // If B = X was the last use of X in a liverange, we have to shrink it now
1661 // that B = X is gone.
1662 for (SmallVector<unsigned, 8>::iterator I = SourceRegisters.begin(),
1663 E = SourceRegisters.end(); I != E; ++I) {
1664 LIS->shrinkToUses(&LIS->getInterval(*I));
1667 // If we get here, we know that we can coalesce the live ranges. Ask the
1668 // intervals to coalesce themselves now.
1669 LHS.join(RHS, &LHSValNoAssignments[0], &RHSValNoAssignments[0], NewVNInfo,
1675 // DepthMBBCompare - Comparison predicate that sort first based on the loop
1676 // depth of the basic block (the unsigned), and then on the MBB number.
1677 struct DepthMBBCompare {
1678 typedef std::pair<unsigned, MachineBasicBlock*> DepthMBBPair;
1679 bool operator()(const DepthMBBPair &LHS, const DepthMBBPair &RHS) const {
1680 // Deeper loops first
1681 if (LHS.first != RHS.first)
1682 return LHS.first > RHS.first;
1684 // Prefer blocks that are more connected in the CFG. This takes care of
1685 // the most difficult copies first while intervals are short.
1686 unsigned cl = LHS.second->pred_size() + LHS.second->succ_size();
1687 unsigned cr = RHS.second->pred_size() + RHS.second->succ_size();
1691 // As a last resort, sort by block number.
1692 return LHS.second->getNumber() < RHS.second->getNumber();
1697 void RegisterCoalescer::CopyCoalesceInMBB(MachineBasicBlock *MBB,
1698 std::vector<MachineInstr*> &TryAgain) {
1699 DEBUG(dbgs() << MBB->getName() << ":\n");
1701 SmallVector<MachineInstr*, 8> VirtCopies;
1702 SmallVector<MachineInstr*, 8> PhysCopies;
1703 SmallVector<MachineInstr*, 8> ImpDefCopies;
1704 for (MachineBasicBlock::iterator MII = MBB->begin(), E = MBB->end();
1706 MachineInstr *Inst = MII++;
1708 // If this isn't a copy nor a extract_subreg, we can't join intervals.
1709 unsigned SrcReg, DstReg;
1710 if (Inst->isCopy()) {
1711 DstReg = Inst->getOperand(0).getReg();
1712 SrcReg = Inst->getOperand(1).getReg();
1713 } else if (Inst->isSubregToReg()) {
1714 DstReg = Inst->getOperand(0).getReg();
1715 SrcReg = Inst->getOperand(2).getReg();
1719 bool SrcIsPhys = TargetRegisterInfo::isPhysicalRegister(SrcReg);
1720 bool DstIsPhys = TargetRegisterInfo::isPhysicalRegister(DstReg);
1721 if (LIS->hasInterval(SrcReg) && LIS->getInterval(SrcReg).empty())
1722 ImpDefCopies.push_back(Inst);
1723 else if (SrcIsPhys || DstIsPhys)
1724 PhysCopies.push_back(Inst);
1726 VirtCopies.push_back(Inst);
1729 // Try coalescing implicit copies and insert_subreg <undef> first,
1730 // followed by copies to / from physical registers, then finally copies
1731 // from virtual registers to virtual registers.
1732 for (unsigned i = 0, e = ImpDefCopies.size(); i != e; ++i) {
1733 MachineInstr *TheCopy = ImpDefCopies[i];
1735 if (!JoinCopy(TheCopy, Again))
1737 TryAgain.push_back(TheCopy);
1739 for (unsigned i = 0, e = PhysCopies.size(); i != e; ++i) {
1740 MachineInstr *TheCopy = PhysCopies[i];
1742 if (!JoinCopy(TheCopy, Again))
1744 TryAgain.push_back(TheCopy);
1746 for (unsigned i = 0, e = VirtCopies.size(); i != e; ++i) {
1747 MachineInstr *TheCopy = VirtCopies[i];
1749 if (!JoinCopy(TheCopy, Again))
1751 TryAgain.push_back(TheCopy);
1755 void RegisterCoalescer::joinIntervals() {
1756 DEBUG(dbgs() << "********** JOINING INTERVALS ***********\n");
1758 std::vector<MachineInstr*> TryAgainList;
1759 if (Loops->empty()) {
1760 // If there are no loops in the function, join intervals in function order.
1761 for (MachineFunction::iterator I = MF->begin(), E = MF->end();
1763 CopyCoalesceInMBB(I, TryAgainList);
1765 // Otherwise, join intervals in inner loops before other intervals.
1766 // Unfortunately we can't just iterate over loop hierarchy here because
1767 // there may be more MBB's than BB's. Collect MBB's for sorting.
1769 // Join intervals in the function prolog first. We want to join physical
1770 // registers with virtual registers before the intervals got too long.
1771 std::vector<std::pair<unsigned, MachineBasicBlock*> > MBBs;
1772 for (MachineFunction::iterator I = MF->begin(), E = MF->end();I != E;++I){
1773 MachineBasicBlock *MBB = I;
1774 MBBs.push_back(std::make_pair(Loops->getLoopDepth(MBB), I));
1777 // Sort by loop depth.
1778 std::sort(MBBs.begin(), MBBs.end(), DepthMBBCompare());
1780 // Finally, join intervals in loop nest order.
1781 for (unsigned i = 0, e = MBBs.size(); i != e; ++i)
1782 CopyCoalesceInMBB(MBBs[i].second, TryAgainList);
1785 // Joining intervals can allow other intervals to be joined. Iteratively join
1786 // until we make no progress.
1787 bool ProgressMade = true;
1788 while (ProgressMade) {
1789 ProgressMade = false;
1791 for (unsigned i = 0, e = TryAgainList.size(); i != e; ++i) {
1792 MachineInstr *&TheCopy = TryAgainList[i];
1797 bool Success = JoinCopy(TheCopy, Again);
1798 if (Success || !Again) {
1799 TheCopy= 0; // Mark this one as done.
1800 ProgressMade = true;
1806 void RegisterCoalescer::releaseMemory() {
1807 JoinedCopies.clear();
1808 ReMatCopies.clear();
1812 bool RegisterCoalescer::runOnMachineFunction(MachineFunction &fn) {
1814 MRI = &fn.getRegInfo();
1815 TM = &fn.getTarget();
1816 TRI = TM->getRegisterInfo();
1817 TII = TM->getInstrInfo();
1818 LIS = &getAnalysis<LiveIntervals>();
1819 LDV = &getAnalysis<LiveDebugVariables>();
1820 AA = &getAnalysis<AliasAnalysis>();
1821 Loops = &getAnalysis<MachineLoopInfo>();
1823 DEBUG(dbgs() << "********** SIMPLE REGISTER COALESCING **********\n"
1824 << "********** Function: "
1825 << ((Value*)MF->getFunction())->getName() << '\n');
1827 if (VerifyCoalescing)
1828 MF->verify(this, "Before register coalescing");
1830 RegClassInfo.runOnMachineFunction(fn);
1832 // Join (coalesce) intervals if requested.
1833 if (EnableJoining) {
1836 dbgs() << "********** INTERVALS POST JOINING **********\n";
1837 for (LiveIntervals::iterator I = LIS->begin(), E = LIS->end();
1839 I->second->print(dbgs(), TRI);
1845 // Perform a final pass over the instructions and compute spill weights
1846 // and remove identity moves.
1847 SmallVector<unsigned, 4> DeadDefs, InflateRegs;
1848 for (MachineFunction::iterator mbbi = MF->begin(), mbbe = MF->end();
1849 mbbi != mbbe; ++mbbi) {
1850 MachineBasicBlock* mbb = mbbi;
1851 for (MachineBasicBlock::iterator mii = mbb->begin(), mie = mbb->end();
1853 MachineInstr *MI = mii;
1854 if (JoinedCopies.count(MI)) {
1855 // Delete all coalesced copies.
1856 bool DoDelete = true;
1857 assert(MI->isCopyLike() && "Unrecognized copy instruction");
1858 unsigned SrcReg = MI->getOperand(MI->isSubregToReg() ? 2 : 1).getReg();
1859 unsigned DstReg = MI->getOperand(0).getReg();
1861 // Collect candidates for register class inflation.
1862 if (TargetRegisterInfo::isVirtualRegister(SrcReg) &&
1863 RegClassInfo.isProperSubClass(MRI->getRegClass(SrcReg)))
1864 InflateRegs.push_back(SrcReg);
1865 if (TargetRegisterInfo::isVirtualRegister(DstReg) &&
1866 RegClassInfo.isProperSubClass(MRI->getRegClass(DstReg)))
1867 InflateRegs.push_back(DstReg);
1869 if (TargetRegisterInfo::isPhysicalRegister(SrcReg) &&
1870 MI->getNumOperands() > 2)
1871 // Do not delete extract_subreg, insert_subreg of physical
1872 // registers unless the definition is dead. e.g.
1873 // %DO<def> = INSERT_SUBREG %D0<undef>, %S0<kill>, 1
1874 // or else the scavenger may complain. LowerSubregs will
1875 // delete them later.
1878 if (MI->allDefsAreDead()) {
1879 if (TargetRegisterInfo::isVirtualRegister(SrcReg) &&
1880 LIS->hasInterval(SrcReg))
1881 LIS->shrinkToUses(&LIS->getInterval(SrcReg));
1885 // We need the instruction to adjust liveness, so make it a KILL.
1886 if (MI->isSubregToReg()) {
1887 MI->RemoveOperand(3);
1888 MI->RemoveOperand(1);
1890 MI->setDesc(TII->get(TargetOpcode::KILL));
1891 mii = llvm::next(mii);
1893 LIS->RemoveMachineInstrFromMaps(MI);
1894 mii = mbbi->erase(mii);
1900 // Now check if this is a remat'ed def instruction which is now dead.
1901 if (ReMatDefs.count(MI)) {
1903 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
1904 const MachineOperand &MO = MI->getOperand(i);
1907 unsigned Reg = MO.getReg();
1910 DeadDefs.push_back(Reg);
1911 if (TargetRegisterInfo::isVirtualRegister(Reg)) {
1912 // Remat may also enable register class inflation.
1913 if (RegClassInfo.isProperSubClass(MRI->getRegClass(Reg)))
1914 InflateRegs.push_back(Reg);
1918 if (TargetRegisterInfo::isPhysicalRegister(Reg) ||
1919 !MRI->use_nodbg_empty(Reg)) {
1925 while (!DeadDefs.empty()) {
1926 unsigned DeadDef = DeadDefs.back();
1927 DeadDefs.pop_back();
1928 RemoveDeadDef(LIS->getInterval(DeadDef), MI);
1930 LIS->RemoveMachineInstrFromMaps(mii);
1931 mii = mbbi->erase(mii);
1939 // Check for now unnecessary kill flags.
1940 if (LIS->isNotInMIMap(MI)) continue;
1941 SlotIndex DefIdx = LIS->getInstructionIndex(MI).getRegSlot();
1942 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
1943 MachineOperand &MO = MI->getOperand(i);
1944 if (!MO.isReg() || !MO.isKill()) continue;
1945 unsigned reg = MO.getReg();
1946 if (!reg || !LIS->hasInterval(reg)) continue;
1947 if (!LIS->getInterval(reg).killedAt(DefIdx)) {
1948 MO.setIsKill(false);
1951 // When leaving a kill flag on a physreg, check if any subregs should
1953 if (!TargetRegisterInfo::isPhysicalRegister(reg))
1955 for (const unsigned *SR = TRI->getSubRegisters(reg);
1956 unsigned S = *SR; ++SR)
1957 if (LIS->hasInterval(S) && LIS->getInterval(S).liveAt(DefIdx))
1958 MI->addRegisterDefined(S, TRI);
1963 // After deleting a lot of copies, register classes may be less constrained.
1964 // Removing sub-register opreands may alow GR32_ABCD -> GR32 and DPR_VFP2 ->
1966 array_pod_sort(InflateRegs.begin(), InflateRegs.end());
1967 InflateRegs.erase(std::unique(InflateRegs.begin(), InflateRegs.end()),
1969 DEBUG(dbgs() << "Trying to inflate " << InflateRegs.size() << " regs.\n");
1970 for (unsigned i = 0, e = InflateRegs.size(); i != e; ++i) {
1971 unsigned Reg = InflateRegs[i];
1972 if (MRI->reg_nodbg_empty(Reg))
1974 if (MRI->recomputeRegClass(Reg, *TM)) {
1975 DEBUG(dbgs() << PrintReg(Reg) << " inflated to "
1976 << MRI->getRegClass(Reg)->getName() << '\n');
1983 if (VerifyCoalescing)
1984 MF->verify(this, "After register coalescing");
1988 /// print - Implement the dump method.
1989 void RegisterCoalescer::print(raw_ostream &O, const Module* m) const {