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 EnablePhysicalJoin("join-physregs",
67 cl::desc("Join physical register copies"),
68 cl::init(false), cl::Hidden);
71 VerifyCoalescing("verify-coalescing",
72 cl::desc("Verify machine instrs before and after register coalescing"),
76 class RegisterCoalescer : public MachineFunctionPass {
78 MachineRegisterInfo* MRI;
79 const TargetMachine* TM;
80 const TargetRegisterInfo* TRI;
81 const TargetInstrInfo* TII;
83 LiveDebugVariables *LDV;
84 const MachineLoopInfo* Loops;
86 RegisterClassInfo RegClassInfo;
88 /// JoinedCopies - Keep track of copies eliminated due to coalescing.
90 SmallPtrSet<MachineInstr*, 32> JoinedCopies;
92 /// ReMatCopies - Keep track of copies eliminated due to remat.
94 SmallPtrSet<MachineInstr*, 32> ReMatCopies;
96 /// ReMatDefs - Keep track of definition instructions which have
98 SmallPtrSet<MachineInstr*, 8> ReMatDefs;
100 /// joinAllIntervals - join compatible live intervals
101 void joinAllIntervals();
103 /// copyCoalesceInMBB - Coalesce copies in the specified MBB, putting
104 /// copies that cannot yet be coalesced into the "TryAgain" list.
105 void copyCoalesceInMBB(MachineBasicBlock *MBB,
106 std::vector<MachineInstr*> &TryAgain);
108 /// joinCopy - Attempt to join intervals corresponding to SrcReg/DstReg,
109 /// which are the src/dst of the copy instruction CopyMI. This returns
110 /// true if the copy was successfully coalesced away. If it is not
111 /// currently possible to coalesce this interval, but it may be possible if
112 /// other things get coalesced, then it returns true by reference in
114 bool joinCopy(MachineInstr *TheCopy, bool &Again);
116 /// joinIntervals - Attempt to join these two intervals. On failure, this
117 /// returns false. The output "SrcInt" will not have been modified, so we
118 /// can use this information below to update aliases.
119 bool joinIntervals(CoalescerPair &CP);
121 /// Attempt joining with a reserved physreg.
122 bool joinReservedPhysReg(CoalescerPair &CP);
124 /// Check for interference with a normal unreserved physreg.
125 bool canJoinPhysReg(CoalescerPair &CP);
127 /// adjustCopiesBackFrom - We found a non-trivially-coalescable copy. If
128 /// the source value number is defined by a copy from the destination reg
129 /// see if we can merge these two destination reg valno# into a single
130 /// value number, eliminating a copy.
131 bool adjustCopiesBackFrom(const CoalescerPair &CP, MachineInstr *CopyMI);
133 /// hasOtherReachingDefs - Return true if there are definitions of IntB
134 /// other than BValNo val# that can reach uses of AValno val# of IntA.
135 bool hasOtherReachingDefs(LiveInterval &IntA, LiveInterval &IntB,
136 VNInfo *AValNo, VNInfo *BValNo);
138 /// removeCopyByCommutingDef - We found a non-trivially-coalescable copy.
139 /// If the source value number is defined by a commutable instruction and
140 /// its other operand is coalesced to the copy dest register, see if we
141 /// can transform the copy into a noop by commuting the definition.
142 bool removeCopyByCommutingDef(const CoalescerPair &CP,MachineInstr *CopyMI);
144 /// reMaterializeTrivialDef - If the source of a copy is defined by a
145 /// trivial computation, replace the copy by rematerialize the definition.
146 /// If PreserveSrcInt is true, make sure SrcInt is valid after the call.
147 bool reMaterializeTrivialDef(LiveInterval &SrcInt, bool PreserveSrcInt,
148 unsigned DstReg, MachineInstr *CopyMI);
150 /// shouldJoinPhys - Return true if a physreg copy should be joined.
151 bool shouldJoinPhys(CoalescerPair &CP);
153 /// updateRegDefsUses - Replace all defs and uses of SrcReg to DstReg and
154 /// update the subregister number if it is not zero. If DstReg is a
155 /// physical register and the existing subregister number of the def / use
156 /// being updated is not zero, make sure to set it to the correct physical
158 void updateRegDefsUses(unsigned SrcReg, unsigned DstReg, unsigned SubIdx);
160 /// removeDeadDef - If a def of a live interval is now determined dead,
161 /// remove the val# it defines. If the live interval becomes empty, remove
163 bool removeDeadDef(LiveInterval &li, MachineInstr *DefMI);
165 /// markAsJoined - Remember that CopyMI has already been joined.
166 void markAsJoined(MachineInstr *CopyMI);
168 /// eliminateUndefCopy - Handle copies of undef values.
169 bool eliminateUndefCopy(MachineInstr *CopyMI, const CoalescerPair &CP);
172 static char ID; // Class identification, replacement for typeinfo
173 RegisterCoalescer() : MachineFunctionPass(ID) {
174 initializeRegisterCoalescerPass(*PassRegistry::getPassRegistry());
177 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
179 virtual void releaseMemory();
181 /// runOnMachineFunction - pass entry point
182 virtual bool runOnMachineFunction(MachineFunction&);
184 /// print - Implement the dump method.
185 virtual void print(raw_ostream &O, const Module* = 0) const;
187 } /// end anonymous namespace
189 char &llvm::RegisterCoalescerID = RegisterCoalescer::ID;
191 INITIALIZE_PASS_BEGIN(RegisterCoalescer, "simple-register-coalescing",
192 "Simple Register Coalescing", false, false)
193 INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
194 INITIALIZE_PASS_DEPENDENCY(LiveDebugVariables)
195 INITIALIZE_PASS_DEPENDENCY(SlotIndexes)
196 INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
197 INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
198 INITIALIZE_PASS_END(RegisterCoalescer, "simple-register-coalescing",
199 "Simple Register Coalescing", false, false)
201 char RegisterCoalescer::ID = 0;
203 static unsigned compose(const TargetRegisterInfo &tri, unsigned a, unsigned b) {
206 return tri.composeSubRegIndices(a, b);
209 static bool isMoveInstr(const TargetRegisterInfo &tri, const MachineInstr *MI,
210 unsigned &Src, unsigned &Dst,
211 unsigned &SrcSub, unsigned &DstSub) {
213 Dst = MI->getOperand(0).getReg();
214 DstSub = MI->getOperand(0).getSubReg();
215 Src = MI->getOperand(1).getReg();
216 SrcSub = MI->getOperand(1).getSubReg();
217 } else if (MI->isSubregToReg()) {
218 Dst = MI->getOperand(0).getReg();
219 DstSub = compose(tri, MI->getOperand(0).getSubReg(),
220 MI->getOperand(3).getImm());
221 Src = MI->getOperand(2).getReg();
222 SrcSub = MI->getOperand(2).getSubReg();
228 bool CoalescerPair::setRegisters(const MachineInstr *MI) {
232 Flipped = CrossClass = false;
234 unsigned Src, Dst, SrcSub, DstSub;
235 if (!isMoveInstr(TRI, MI, Src, Dst, SrcSub, DstSub))
237 Partial = SrcSub || DstSub;
239 // If one register is a physreg, it must be Dst.
240 if (TargetRegisterInfo::isPhysicalRegister(Src)) {
241 if (TargetRegisterInfo::isPhysicalRegister(Dst))
244 std::swap(SrcSub, DstSub);
248 const MachineRegisterInfo &MRI = MI->getParent()->getParent()->getRegInfo();
250 if (TargetRegisterInfo::isPhysicalRegister(Dst)) {
251 // Eliminate DstSub on a physreg.
253 Dst = TRI.getSubReg(Dst, DstSub);
254 if (!Dst) return false;
258 // Eliminate SrcSub by picking a corresponding Dst superregister.
260 Dst = TRI.getMatchingSuperReg(Dst, SrcSub, MRI.getRegClass(Src));
261 if (!Dst) return false;
263 } else if (!MRI.getRegClass(Src)->contains(Dst)) {
267 // Both registers are virtual.
268 const TargetRegisterClass *SrcRC = MRI.getRegClass(Src);
269 const TargetRegisterClass *DstRC = MRI.getRegClass(Dst);
271 // Both registers have subreg indices.
272 if (SrcSub && DstSub) {
273 // Copies between different sub-registers are never coalescable.
274 if (Src == Dst && SrcSub != DstSub)
277 NewRC = TRI.getCommonSuperRegClass(SrcRC, SrcSub, DstRC, DstSub,
282 // SrcReg will be merged with a sub-register of DstReg.
284 NewRC = TRI.getMatchingSuperRegClass(DstRC, SrcRC, DstSub);
286 // DstReg will be merged with a sub-register of SrcReg.
288 NewRC = TRI.getMatchingSuperRegClass(SrcRC, DstRC, SrcSub);
290 // This is a straight copy without sub-registers.
291 NewRC = TRI.getCommonSubClass(DstRC, SrcRC);
294 // The combined constraint may be impossible to satisfy.
298 // Prefer SrcReg to be a sub-register of DstReg.
299 // FIXME: Coalescer should support subregs symmetrically.
300 if (DstIdx && !SrcIdx) {
302 std::swap(SrcIdx, DstIdx);
306 CrossClass = NewRC != DstRC || NewRC != SrcRC;
308 // Check our invariants
309 assert(TargetRegisterInfo::isVirtualRegister(Src) && "Src must be virtual");
310 assert(!(TargetRegisterInfo::isPhysicalRegister(Dst) && DstSub) &&
311 "Cannot have a physical SubIdx");
317 bool CoalescerPair::flip() {
318 if (TargetRegisterInfo::isPhysicalRegister(DstReg))
320 std::swap(SrcReg, DstReg);
321 std::swap(SrcIdx, DstIdx);
326 bool CoalescerPair::isCoalescable(const MachineInstr *MI) const {
329 unsigned Src, Dst, SrcSub, DstSub;
330 if (!isMoveInstr(TRI, MI, Src, Dst, SrcSub, DstSub))
333 // Find the virtual register that is SrcReg.
336 std::swap(SrcSub, DstSub);
337 } else if (Src != SrcReg) {
341 // Now check that Dst matches DstReg.
342 if (TargetRegisterInfo::isPhysicalRegister(DstReg)) {
343 if (!TargetRegisterInfo::isPhysicalRegister(Dst))
345 assert(!DstIdx && !SrcIdx && "Inconsistent CoalescerPair state.");
346 // DstSub could be set for a physreg from INSERT_SUBREG.
348 Dst = TRI.getSubReg(Dst, DstSub);
351 return DstReg == Dst;
352 // This is a partial register copy. Check that the parts match.
353 return TRI.getSubReg(DstReg, SrcSub) == Dst;
355 // DstReg is virtual.
358 // Registers match, do the subregisters line up?
359 return compose(TRI, SrcIdx, SrcSub) == compose(TRI, DstIdx, DstSub);
363 void RegisterCoalescer::getAnalysisUsage(AnalysisUsage &AU) const {
364 AU.setPreservesCFG();
365 AU.addRequired<AliasAnalysis>();
366 AU.addRequired<LiveIntervals>();
367 AU.addPreserved<LiveIntervals>();
368 AU.addRequired<LiveDebugVariables>();
369 AU.addPreserved<LiveDebugVariables>();
370 AU.addPreserved<SlotIndexes>();
371 AU.addRequired<MachineLoopInfo>();
372 AU.addPreserved<MachineLoopInfo>();
373 AU.addPreservedID(MachineDominatorsID);
374 MachineFunctionPass::getAnalysisUsage(AU);
377 void RegisterCoalescer::markAsJoined(MachineInstr *CopyMI) {
378 /// Joined copies are not deleted immediately, but kept in JoinedCopies.
379 JoinedCopies.insert(CopyMI);
381 /// Mark all register operands of CopyMI as <undef> so they won't affect dead
382 /// code elimination.
383 for (MachineInstr::mop_iterator I = CopyMI->operands_begin(),
384 E = CopyMI->operands_end(); I != E; ++I)
389 /// adjustCopiesBackFrom - We found a non-trivially-coalescable copy with IntA
390 /// being the source and IntB being the dest, thus this defines a value number
391 /// in IntB. If the source value number (in IntA) is defined by a copy from B,
392 /// see if we can merge these two pieces of B into a single value number,
393 /// eliminating a copy. For example:
397 /// B1 = A3 <- this copy
399 /// In this case, B0 can be extended to where the B1 copy lives, allowing the B1
400 /// value number to be replaced with B0 (which simplifies the B liveinterval).
402 /// This returns true if an interval was modified.
404 bool RegisterCoalescer::adjustCopiesBackFrom(const CoalescerPair &CP,
405 MachineInstr *CopyMI) {
406 assert(!CP.isPartial() && "This doesn't work for partial copies.");
408 // Bail if there is no dst interval - can happen when merging physical subreg
410 if (!LIS->hasInterval(CP.getDstReg()))
414 LIS->getInterval(CP.isFlipped() ? CP.getDstReg() : CP.getSrcReg());
416 LIS->getInterval(CP.isFlipped() ? CP.getSrcReg() : CP.getDstReg());
417 SlotIndex CopyIdx = LIS->getInstructionIndex(CopyMI).getRegSlot();
419 // BValNo is a value number in B that is defined by a copy from A. 'B3' in
420 // the example above.
421 LiveInterval::iterator BLR = IntB.FindLiveRangeContaining(CopyIdx);
422 if (BLR == IntB.end()) return false;
423 VNInfo *BValNo = BLR->valno;
425 // Get the location that B is defined at. Two options: either this value has
426 // an unknown definition point or it is defined at CopyIdx. If unknown, we
428 if (BValNo->def != CopyIdx) return false;
430 // AValNo is the value number in A that defines the copy, A3 in the example.
431 SlotIndex CopyUseIdx = CopyIdx.getRegSlot(true);
432 LiveInterval::iterator ALR = IntA.FindLiveRangeContaining(CopyUseIdx);
433 // The live range might not exist after fun with physreg coalescing.
434 if (ALR == IntA.end()) return false;
435 VNInfo *AValNo = ALR->valno;
437 // If AValNo is defined as a copy from IntB, we can potentially process this.
438 // Get the instruction that defines this value number.
439 MachineInstr *ACopyMI = LIS->getInstructionFromIndex(AValNo->def);
440 if (!CP.isCoalescable(ACopyMI))
443 // Get the LiveRange in IntB that this value number starts with.
444 LiveInterval::iterator ValLR =
445 IntB.FindLiveRangeContaining(AValNo->def.getPrevSlot());
446 if (ValLR == IntB.end())
449 // Make sure that the end of the live range is inside the same block as
451 MachineInstr *ValLREndInst =
452 LIS->getInstructionFromIndex(ValLR->end.getPrevSlot());
453 if (!ValLREndInst || ValLREndInst->getParent() != CopyMI->getParent())
456 // Okay, we now know that ValLR ends in the same block that the CopyMI
457 // live-range starts. If there are no intervening live ranges between them in
458 // IntB, we can merge them.
459 if (ValLR+1 != BLR) return false;
461 // If a live interval is a physical register, conservatively check if any
462 // of its aliases is overlapping the live interval of the virtual register.
463 // If so, do not coalesce.
464 if (TargetRegisterInfo::isPhysicalRegister(IntB.reg)) {
465 for (const uint16_t *AS = TRI->getAliasSet(IntB.reg); *AS; ++AS)
466 if (LIS->hasInterval(*AS) && IntA.overlaps(LIS->getInterval(*AS))) {
468 dbgs() << "\t\tInterfere with alias ";
469 LIS->getInterval(*AS).print(dbgs(), TRI);
476 dbgs() << "Extending: ";
477 IntB.print(dbgs(), TRI);
480 SlotIndex FillerStart = ValLR->end, FillerEnd = BLR->start;
481 // We are about to delete CopyMI, so need to remove it as the 'instruction
482 // that defines this value #'. Update the valnum with the new defining
484 BValNo->def = FillerStart;
486 // Okay, we can merge them. We need to insert a new liverange:
487 // [ValLR.end, BLR.begin) of either value number, then we merge the
488 // two value numbers.
489 IntB.addRange(LiveRange(FillerStart, FillerEnd, BValNo));
491 // If the IntB live range is assigned to a physical register, and if that
492 // physreg has sub-registers, update their live intervals as well.
493 if (TargetRegisterInfo::isPhysicalRegister(IntB.reg)) {
494 for (const uint16_t *SR = TRI->getSubRegisters(IntB.reg); *SR; ++SR) {
495 if (!LIS->hasInterval(*SR))
497 LiveInterval &SRLI = LIS->getInterval(*SR);
498 SRLI.addRange(LiveRange(FillerStart, FillerEnd,
499 SRLI.getNextValue(FillerStart,
500 LIS->getVNInfoAllocator())));
504 // Okay, merge "B1" into the same value number as "B0".
505 if (BValNo != ValLR->valno) {
506 // If B1 is killed by a PHI, then the merged live range must also be killed
507 // by the same PHI, as B0 and B1 can not overlap.
508 bool HasPHIKill = BValNo->hasPHIKill();
509 IntB.MergeValueNumberInto(BValNo, ValLR->valno);
511 ValLR->valno->setHasPHIKill(true);
514 dbgs() << " result = ";
515 IntB.print(dbgs(), TRI);
519 // If the source instruction was killing the source register before the
520 // merge, unset the isKill marker given the live range has been extended.
521 int UIdx = ValLREndInst->findRegisterUseOperandIdx(IntB.reg, true);
523 ValLREndInst->getOperand(UIdx).setIsKill(false);
526 // Rewrite the copy. If the copy instruction was killing the destination
527 // register before the merge, find the last use and trim the live range. That
528 // will also add the isKill marker.
529 CopyMI->substituteRegister(IntA.reg, IntB.reg, 0, *TRI);
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, *MF);
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
910 void RegisterCoalescer::updateRegDefsUses(unsigned SrcReg,
913 bool DstIsPhys = TargetRegisterInfo::isPhysicalRegister(DstReg);
915 // Update LiveDebugVariables.
916 LDV->renameRegister(SrcReg, DstReg, SubIdx);
918 for (MachineRegisterInfo::reg_iterator I = MRI->reg_begin(SrcReg);
919 MachineInstr *UseMI = I.skipInstruction();) {
920 // A PhysReg copy that won't be coalesced can perhaps be rematerialized
923 if (UseMI->isFullCopy() &&
924 UseMI->getOperand(1).getReg() == SrcReg &&
925 UseMI->getOperand(0).getReg() != SrcReg &&
926 UseMI->getOperand(0).getReg() != DstReg &&
927 !JoinedCopies.count(UseMI) &&
928 reMaterializeTrivialDef(LIS->getInterval(SrcReg), false,
929 UseMI->getOperand(0).getReg(), UseMI))
933 SmallVector<unsigned,8> Ops;
935 tie(Reads, Writes) = UseMI->readsWritesVirtualRegister(SrcReg, &Ops);
937 // Replace SrcReg with DstReg in all UseMI operands.
938 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
939 MachineOperand &MO = UseMI->getOperand(Ops[i]);
941 // Make sure we don't create read-modify-write defs accidentally. We
942 // assume here that a SrcReg def cannot be joined into a live DstReg. If
943 // RegisterCoalescer starts tracking partially live registers, we will
944 // need to check the actual LiveInterval to determine if DstReg is live
946 if (SubIdx && !Reads)
950 MO.substPhysReg(DstReg, *TRI);
952 MO.substVirtReg(DstReg, SubIdx, *TRI);
955 // This instruction is a copy that will be removed.
956 if (JoinedCopies.count(UseMI))
960 dbgs() << "\t\tupdated: ";
961 if (!UseMI->isDebugValue())
962 dbgs() << LIS->getInstructionIndex(UseMI) << "\t";
968 /// removeIntervalIfEmpty - Check if the live interval of a physical register
969 /// is empty, if so remove it and also remove the empty intervals of its
970 /// sub-registers. Return true if live interval is removed.
971 static bool removeIntervalIfEmpty(LiveInterval &li, LiveIntervals *LIS,
972 const TargetRegisterInfo *TRI) {
974 if (TargetRegisterInfo::isPhysicalRegister(li.reg))
975 for (const uint16_t* SR = TRI->getSubRegisters(li.reg); *SR; ++SR) {
976 if (!LIS->hasInterval(*SR))
978 LiveInterval &sli = LIS->getInterval(*SR);
980 LIS->removeInterval(*SR);
982 LIS->removeInterval(li.reg);
988 /// removeDeadDef - If a def of a live interval is now determined dead, remove
989 /// the val# it defines. If the live interval becomes empty, remove it as well.
990 bool RegisterCoalescer::removeDeadDef(LiveInterval &li, MachineInstr *DefMI) {
991 SlotIndex DefIdx = LIS->getInstructionIndex(DefMI).getRegSlot();
992 LiveInterval::iterator MLR = li.FindLiveRangeContaining(DefIdx);
993 if (DefIdx != MLR->valno->def)
995 li.removeValNo(MLR->valno);
996 return removeIntervalIfEmpty(li, LIS, TRI);
999 /// shouldJoinPhys - Return true if a copy involving a physreg should be joined.
1000 /// We need to be careful about coalescing a source physical register with a
1001 /// virtual register. Once the coalescing is done, it cannot be broken and these
1002 /// are not spillable! If the destination interval uses are far away, think
1003 /// twice about coalescing them!
1004 bool RegisterCoalescer::shouldJoinPhys(CoalescerPair &CP) {
1005 bool Allocatable = LIS->isAllocatable(CP.getDstReg());
1006 LiveInterval &JoinVInt = LIS->getInterval(CP.getSrcReg());
1008 /// Always join simple intervals that are defined by a single copy from a
1009 /// reserved register. This doesn't increase register pressure, so it is
1010 /// always beneficial.
1011 if (!Allocatable && CP.isFlipped() && JoinVInt.containsOneValue())
1014 if (!EnablePhysicalJoin) {
1015 DEBUG(dbgs() << "\tPhysreg joins disabled.\n");
1019 // Only coalesce to allocatable physreg, we don't want to risk modifying
1020 // reserved registers.
1022 DEBUG(dbgs() << "\tRegister is an unallocatable physreg.\n");
1023 return false; // Not coalescable.
1026 // Don't join with physregs that have a ridiculous number of live
1027 // ranges. The data structure performance is really bad when that
1029 if (LIS->hasInterval(CP.getDstReg()) &&
1030 LIS->getInterval(CP.getDstReg()).ranges.size() > 1000) {
1033 << "\tPhysical register live interval too complicated, abort!\n");
1037 // FIXME: Why are we skipping this test for partial copies?
1038 // CodeGen/X86/phys_subreg_coalesce-3.ll needs it.
1039 if (!CP.isPartial()) {
1040 const TargetRegisterClass *RC = MRI->getRegClass(CP.getSrcReg());
1041 unsigned Threshold = RegClassInfo.getNumAllocatableRegs(RC) * 2;
1042 unsigned Length = LIS->getApproximateInstructionCount(JoinVInt);
1043 if (Length > Threshold) {
1045 DEBUG(dbgs() << "\tMay tie down a physical register, abort!\n");
1053 /// joinCopy - Attempt to join intervals corresponding to SrcReg/DstReg,
1054 /// which are the src/dst of the copy instruction CopyMI. This returns true
1055 /// if the copy was successfully coalesced away. If it is not currently
1056 /// possible to coalesce this interval, but it may be possible if other
1057 /// things get coalesced, then it returns true by reference in 'Again'.
1058 bool RegisterCoalescer::joinCopy(MachineInstr *CopyMI, bool &Again) {
1061 if (JoinedCopies.count(CopyMI) || ReMatCopies.count(CopyMI))
1062 return false; // Already done.
1064 DEBUG(dbgs() << LIS->getInstructionIndex(CopyMI) << '\t' << *CopyMI);
1066 CoalescerPair CP(*TII, *TRI);
1067 if (!CP.setRegisters(CopyMI)) {
1068 DEBUG(dbgs() << "\tNot coalescable.\n");
1072 // If they are already joined we continue.
1073 if (CP.getSrcReg() == CP.getDstReg()) {
1074 markAsJoined(CopyMI);
1075 DEBUG(dbgs() << "\tCopy already coalesced.\n");
1076 return false; // Not coalescable.
1079 // Eliminate undefs.
1080 if (!CP.isPhys() && eliminateUndefCopy(CopyMI, CP)) {
1081 markAsJoined(CopyMI);
1082 DEBUG(dbgs() << "\tEliminated copy of <undef> value.\n");
1083 return false; // Not coalescable.
1086 // Enforce policies.
1088 DEBUG(dbgs() << "\tConsidering merging " << PrintReg(CP.getSrcReg(), TRI)
1089 << " with " << PrintReg(CP.getDstReg(), TRI, CP.getSrcIdx())
1091 if (!shouldJoinPhys(CP)) {
1092 // Before giving up coalescing, if definition of source is defined by
1093 // trivial computation, try rematerializing it.
1094 if (!CP.isFlipped() &&
1095 reMaterializeTrivialDef(LIS->getInterval(CP.getSrcReg()), true,
1096 CP.getDstReg(), CopyMI))
1102 dbgs() << "\tConsidering merging to " << CP.getNewRC()->getName()
1104 if (CP.getDstIdx() && CP.getSrcIdx())
1105 dbgs() << PrintReg(CP.getDstReg()) << " in "
1106 << TRI->getSubRegIndexName(CP.getDstIdx()) << " and "
1107 << PrintReg(CP.getSrcReg()) << " in "
1108 << TRI->getSubRegIndexName(CP.getSrcIdx()) << '\n';
1110 dbgs() << PrintReg(CP.getSrcReg(), TRI) << " in "
1111 << PrintReg(CP.getDstReg(), TRI, CP.getSrcIdx()) << '\n';
1114 // When possible, let DstReg be the larger interval.
1115 if (!CP.isPartial() && LIS->getInterval(CP.getSrcReg()).ranges.size() >
1116 LIS->getInterval(CP.getDstReg()).ranges.size())
1120 // Okay, attempt to join these two intervals. On failure, this returns false.
1121 // Otherwise, if one of the intervals being joined is a physreg, this method
1122 // always canonicalizes DstInt to be it. The output "SrcInt" will not have
1123 // been modified, so we can use this information below to update aliases.
1124 if (!joinIntervals(CP)) {
1125 // Coalescing failed.
1127 // If definition of source is defined by trivial computation, try
1128 // rematerializing it.
1129 if (!CP.isFlipped() &&
1130 reMaterializeTrivialDef(LIS->getInterval(CP.getSrcReg()), true,
1131 CP.getDstReg(), CopyMI))
1134 // If we can eliminate the copy without merging the live ranges, do so now.
1135 if (!CP.isPartial()) {
1136 if (adjustCopiesBackFrom(CP, CopyMI) ||
1137 removeCopyByCommutingDef(CP, CopyMI)) {
1138 markAsJoined(CopyMI);
1139 DEBUG(dbgs() << "\tTrivial!\n");
1144 // Otherwise, we are unable to join the intervals.
1145 DEBUG(dbgs() << "\tInterference!\n");
1146 Again = true; // May be possible to coalesce later.
1150 // Coalescing to a virtual register that is of a sub-register class of the
1151 // other. Make sure the resulting register is set to the right register class.
1152 if (CP.isCrossClass()) {
1154 MRI->setRegClass(CP.getDstReg(), CP.getNewRC());
1157 // Remember to delete the copy instruction.
1158 markAsJoined(CopyMI);
1160 // Rewrite all SrcReg operands to DstReg.
1161 // Also update DstReg operands to include DstIdx if it is set.
1163 updateRegDefsUses(CP.getDstReg(), CP.getDstReg(), CP.getDstIdx());
1164 updateRegDefsUses(CP.getSrcReg(), CP.getDstReg(), CP.getSrcIdx());
1166 // If we have extended the live range of a physical register, make sure we
1167 // update live-in lists as well.
1169 SmallVector<MachineBasicBlock*, 16> BlockSeq;
1170 // joinIntervals invalidates the VNInfos in SrcInt, but we only need the
1171 // ranges for this, and they are preserved.
1172 LiveInterval &SrcInt = LIS->getInterval(CP.getSrcReg());
1173 for (LiveInterval::const_iterator I = SrcInt.begin(), E = SrcInt.end();
1175 LIS->findLiveInMBBs(I->start, I->end, BlockSeq);
1176 for (unsigned idx = 0, size = BlockSeq.size(); idx != size; ++idx) {
1177 MachineBasicBlock &block = *BlockSeq[idx];
1178 if (!block.isLiveIn(CP.getDstReg()))
1179 block.addLiveIn(CP.getDstReg());
1185 // SrcReg is guaranteed to be the register whose live interval that is
1187 LIS->removeInterval(CP.getSrcReg());
1189 // Update regalloc hint.
1190 TRI->UpdateRegAllocHint(CP.getSrcReg(), CP.getDstReg(), *MF);
1193 LiveInterval &DstInt = LIS->getInterval(CP.getDstReg());
1194 dbgs() << "\tJoined. Result = ";
1195 DstInt.print(dbgs(), TRI);
1203 /// Attempt joining with a reserved physreg.
1204 bool RegisterCoalescer::joinReservedPhysReg(CoalescerPair &CP) {
1205 assert(CP.isPhys() && "Must be a physreg copy");
1206 assert(RegClassInfo.isReserved(CP.getDstReg()) && "Not a reserved register");
1207 LiveInterval &RHS = LIS->getInterval(CP.getSrcReg());
1208 DEBUG({ dbgs() << "\t\tRHS = "; RHS.print(dbgs(), TRI); dbgs() << "\n"; });
1210 assert(CP.isFlipped() && RHS.containsOneValue() &&
1211 "Invalid join with reserved register");
1213 // Optimization for reserved registers like ESP. We can only merge with a
1214 // reserved physreg if RHS has a single value that is a copy of CP.DstReg().
1215 // The live range of the reserved register will look like a set of dead defs
1216 // - we don't properly track the live range of reserved registers.
1218 // Deny any overlapping intervals. This depends on all the reserved
1219 // register live ranges to look like dead defs.
1220 for (const uint16_t *AS = TRI->getOverlaps(CP.getDstReg()); *AS; ++AS) {
1221 if (!LIS->hasInterval(*AS)) {
1222 // Make sure at least DstReg itself exists before attempting a join.
1223 if (*AS == CP.getDstReg())
1224 LIS->getOrCreateInterval(CP.getDstReg());
1227 if (RHS.overlaps(LIS->getInterval(*AS))) {
1228 DEBUG(dbgs() << "\t\tInterference: " << PrintReg(*AS, TRI) << '\n');
1232 // Skip any value computations, we are not adding new values to the
1233 // reserved register. Also skip merging the live ranges, the reserved
1234 // register live range doesn't need to be accurate as long as all the
1239 bool RegisterCoalescer::canJoinPhysReg(CoalescerPair &CP) {
1240 assert(CP.isPhys() && "Must be a physreg copy");
1241 // If a live interval is a physical register, check for interference with any
1242 // aliases. The interference check implemented here is a bit more
1243 // conservative than the full interfeence check below. We allow overlapping
1244 // live ranges only when one is a copy of the other.
1245 LiveInterval &RHS = LIS->getInterval(CP.getSrcReg());
1246 DEBUG({ dbgs() << "\t\tRHS = "; RHS.print(dbgs(), TRI); dbgs() << "\n"; });
1248 // Check if a register mask clobbers DstReg.
1249 BitVector UsableRegs;
1250 if (LIS->checkRegMaskInterference(RHS, UsableRegs) &&
1251 !UsableRegs.test(CP.getDstReg())) {
1252 DEBUG(dbgs() << "\t\tRegister mask interference.\n");
1256 for (const uint16_t *AS = TRI->getAliasSet(CP.getDstReg()); *AS; ++AS){
1257 if (!LIS->hasInterval(*AS))
1259 const LiveInterval &LHS = LIS->getInterval(*AS);
1260 LiveInterval::const_iterator LI = LHS.begin();
1261 for (LiveInterval::const_iterator RI = RHS.begin(), RE = RHS.end();
1263 LI = std::lower_bound(LI, LHS.end(), RI->start);
1264 // Does LHS have an overlapping live range starting before RI?
1265 if ((LI != LHS.begin() && LI[-1].end > RI->start) &&
1266 (RI->start != RI->valno->def ||
1267 !CP.isCoalescable(LIS->getInstructionFromIndex(RI->start)))) {
1269 dbgs() << "\t\tInterference from alias: ";
1270 LHS.print(dbgs(), TRI);
1271 dbgs() << "\n\t\tOverlap at " << RI->start << " and no copy.\n";
1276 // Check that LHS ranges beginning in this range are copies.
1277 for (; LI != LHS.end() && LI->start < RI->end; ++LI) {
1278 if (LI->start != LI->valno->def ||
1279 !CP.isCoalescable(LIS->getInstructionFromIndex(LI->start))) {
1281 dbgs() << "\t\tInterference from alias: ";
1282 LHS.print(dbgs(), TRI);
1283 dbgs() << "\n\t\tDef at " << LI->start << " is not a copy.\n";
1293 /// ComputeUltimateVN - Assuming we are going to join two live intervals,
1294 /// compute what the resultant value numbers for each value in the input two
1295 /// ranges will be. This is complicated by copies between the two which can
1296 /// and will commonly cause multiple value numbers to be merged into one.
1298 /// VN is the value number that we're trying to resolve. InstDefiningValue
1299 /// keeps track of the new InstDefiningValue assignment for the result
1300 /// LiveInterval. ThisFromOther/OtherFromThis are sets that keep track of
1301 /// whether a value in this or other is a copy from the opposite set.
1302 /// ThisValNoAssignments/OtherValNoAssignments keep track of value #'s that have
1303 /// already been assigned.
1305 /// ThisFromOther[x] - If x is defined as a copy from the other interval, this
1306 /// contains the value number the copy is from.
1308 static unsigned ComputeUltimateVN(VNInfo *VNI,
1309 SmallVector<VNInfo*, 16> &NewVNInfo,
1310 DenseMap<VNInfo*, VNInfo*> &ThisFromOther,
1311 DenseMap<VNInfo*, VNInfo*> &OtherFromThis,
1312 SmallVector<int, 16> &ThisValNoAssignments,
1313 SmallVector<int, 16> &OtherValNoAssignments) {
1314 unsigned VN = VNI->id;
1316 // If the VN has already been computed, just return it.
1317 if (ThisValNoAssignments[VN] >= 0)
1318 return ThisValNoAssignments[VN];
1319 assert(ThisValNoAssignments[VN] != -2 && "Cyclic value numbers");
1321 // If this val is not a copy from the other val, then it must be a new value
1322 // number in the destination.
1323 DenseMap<VNInfo*, VNInfo*>::iterator I = ThisFromOther.find(VNI);
1324 if (I == ThisFromOther.end()) {
1325 NewVNInfo.push_back(VNI);
1326 return ThisValNoAssignments[VN] = NewVNInfo.size()-1;
1328 VNInfo *OtherValNo = I->second;
1330 // Otherwise, this *is* a copy from the RHS. If the other side has already
1331 // been computed, return it.
1332 if (OtherValNoAssignments[OtherValNo->id] >= 0)
1333 return ThisValNoAssignments[VN] = OtherValNoAssignments[OtherValNo->id];
1335 // Mark this value number as currently being computed, then ask what the
1336 // ultimate value # of the other value is.
1337 ThisValNoAssignments[VN] = -2;
1338 unsigned UltimateVN =
1339 ComputeUltimateVN(OtherValNo, NewVNInfo, OtherFromThis, ThisFromOther,
1340 OtherValNoAssignments, ThisValNoAssignments);
1341 return ThisValNoAssignments[VN] = UltimateVN;
1345 // Find out if we have something like
1348 // if so, we can pretend this is actually
1351 // which allows us to coalesce A and B.
1352 // VNI is the definition of B. LR is the life range of A that includes
1353 // the slot just before B. If we return true, we add "B = X" to DupCopies.
1354 // This implies that A dominates B.
1355 static bool RegistersDefinedFromSameValue(LiveIntervals &li,
1356 const TargetRegisterInfo &tri,
1360 SmallVector<MachineInstr*, 8> &DupCopies) {
1361 // FIXME: This is very conservative. For example, we don't handle
1362 // physical registers.
1364 MachineInstr *MI = li.getInstructionFromIndex(VNI->def);
1366 if (!MI || !MI->isFullCopy() || CP.isPartial() || CP.isPhys())
1369 unsigned Dst = MI->getOperand(0).getReg();
1370 unsigned Src = MI->getOperand(1).getReg();
1372 if (!TargetRegisterInfo::isVirtualRegister(Src) ||
1373 !TargetRegisterInfo::isVirtualRegister(Dst))
1376 unsigned A = CP.getDstReg();
1377 unsigned B = CP.getSrcReg();
1383 VNInfo *Other = LR->valno;
1384 const MachineInstr *OtherMI = li.getInstructionFromIndex(Other->def);
1386 if (!OtherMI || !OtherMI->isFullCopy())
1389 unsigned OtherDst = OtherMI->getOperand(0).getReg();
1390 unsigned OtherSrc = OtherMI->getOperand(1).getReg();
1392 if (!TargetRegisterInfo::isVirtualRegister(OtherSrc) ||
1393 !TargetRegisterInfo::isVirtualRegister(OtherDst))
1396 assert(OtherDst == B);
1398 if (Src != OtherSrc)
1401 // If the copies use two different value numbers of X, we cannot merge
1403 LiveInterval &SrcInt = li.getInterval(Src);
1404 // getVNInfoBefore returns NULL for undef copies. In this case, the
1405 // optimization is still safe.
1406 if (SrcInt.getVNInfoBefore(Other->def) != SrcInt.getVNInfoBefore(VNI->def))
1409 DupCopies.push_back(MI);
1414 /// joinIntervals - Attempt to join these two intervals. On failure, this
1416 bool RegisterCoalescer::joinIntervals(CoalescerPair &CP) {
1417 // Handle physreg joins separately.
1419 if (RegClassInfo.isReserved(CP.getDstReg()))
1420 return joinReservedPhysReg(CP);
1421 if (!canJoinPhysReg(CP))
1425 LiveInterval &RHS = LIS->getInterval(CP.getSrcReg());
1426 DEBUG({ dbgs() << "\t\tRHS = "; RHS.print(dbgs(), TRI); dbgs() << "\n"; });
1428 // Compute the final value assignment, assuming that the live ranges can be
1430 SmallVector<int, 16> LHSValNoAssignments;
1431 SmallVector<int, 16> RHSValNoAssignments;
1432 DenseMap<VNInfo*, VNInfo*> LHSValsDefinedFromRHS;
1433 DenseMap<VNInfo*, VNInfo*> RHSValsDefinedFromLHS;
1434 SmallVector<VNInfo*, 16> NewVNInfo;
1436 SmallVector<MachineInstr*, 8> DupCopies;
1438 LiveInterval &LHS = LIS->getOrCreateInterval(CP.getDstReg());
1439 DEBUG({ dbgs() << "\t\tLHS = "; LHS.print(dbgs(), TRI); dbgs() << "\n"; });
1441 // Loop over the value numbers of the LHS, seeing if any are defined from
1443 for (LiveInterval::vni_iterator i = LHS.vni_begin(), e = LHS.vni_end();
1446 if (VNI->isUnused() || VNI->isPHIDef())
1448 MachineInstr *MI = LIS->getInstructionFromIndex(VNI->def);
1449 assert(MI && "Missing def");
1450 if (!MI->isCopyLike()) // Src not defined by a copy?
1453 // Figure out the value # from the RHS.
1454 LiveRange *lr = RHS.getLiveRangeContaining(VNI->def.getPrevSlot());
1455 // The copy could be to an aliased physreg.
1458 // DstReg is known to be a register in the LHS interval. If the src is
1459 // from the RHS interval, we can use its value #.
1460 if (!CP.isCoalescable(MI) &&
1461 !RegistersDefinedFromSameValue(*LIS, *TRI, CP, VNI, lr, DupCopies))
1464 LHSValsDefinedFromRHS[VNI] = lr->valno;
1467 // Loop over the value numbers of the RHS, seeing if any are defined from
1469 for (LiveInterval::vni_iterator i = RHS.vni_begin(), e = RHS.vni_end();
1472 if (VNI->isUnused() || VNI->isPHIDef())
1474 MachineInstr *MI = LIS->getInstructionFromIndex(VNI->def);
1475 assert(MI && "Missing def");
1476 if (!MI->isCopyLike()) // Src not defined by a copy?
1479 // Figure out the value # from the LHS.
1480 LiveRange *lr = LHS.getLiveRangeContaining(VNI->def.getPrevSlot());
1481 // The copy could be to an aliased physreg.
1484 // DstReg is known to be a register in the RHS interval. If the src is
1485 // from the LHS interval, we can use its value #.
1486 if (!CP.isCoalescable(MI) &&
1487 !RegistersDefinedFromSameValue(*LIS, *TRI, CP, VNI, lr, DupCopies))
1490 RHSValsDefinedFromLHS[VNI] = lr->valno;
1493 LHSValNoAssignments.resize(LHS.getNumValNums(), -1);
1494 RHSValNoAssignments.resize(RHS.getNumValNums(), -1);
1495 NewVNInfo.reserve(LHS.getNumValNums() + RHS.getNumValNums());
1497 for (LiveInterval::vni_iterator i = LHS.vni_begin(), e = LHS.vni_end();
1500 unsigned VN = VNI->id;
1501 if (LHSValNoAssignments[VN] >= 0 || VNI->isUnused())
1503 ComputeUltimateVN(VNI, NewVNInfo,
1504 LHSValsDefinedFromRHS, RHSValsDefinedFromLHS,
1505 LHSValNoAssignments, RHSValNoAssignments);
1507 for (LiveInterval::vni_iterator i = RHS.vni_begin(), e = RHS.vni_end();
1510 unsigned VN = VNI->id;
1511 if (RHSValNoAssignments[VN] >= 0 || VNI->isUnused())
1513 // If this value number isn't a copy from the LHS, it's a new number.
1514 if (RHSValsDefinedFromLHS.find(VNI) == RHSValsDefinedFromLHS.end()) {
1515 NewVNInfo.push_back(VNI);
1516 RHSValNoAssignments[VN] = NewVNInfo.size()-1;
1520 ComputeUltimateVN(VNI, NewVNInfo,
1521 RHSValsDefinedFromLHS, LHSValsDefinedFromRHS,
1522 RHSValNoAssignments, LHSValNoAssignments);
1525 // Armed with the mappings of LHS/RHS values to ultimate values, walk the
1526 // interval lists to see if these intervals are coalescable.
1527 LiveInterval::const_iterator I = LHS.begin();
1528 LiveInterval::const_iterator IE = LHS.end();
1529 LiveInterval::const_iterator J = RHS.begin();
1530 LiveInterval::const_iterator JE = RHS.end();
1532 // Skip ahead until the first place of potential sharing.
1533 if (I != IE && J != JE) {
1534 if (I->start < J->start) {
1535 I = std::upper_bound(I, IE, J->start);
1536 if (I != LHS.begin()) --I;
1537 } else if (J->start < I->start) {
1538 J = std::upper_bound(J, JE, I->start);
1539 if (J != RHS.begin()) --J;
1543 while (I != IE && J != JE) {
1544 // Determine if these two live ranges overlap.
1546 if (I->start < J->start) {
1547 Overlaps = I->end > J->start;
1549 Overlaps = J->end > I->start;
1552 // If so, check value # info to determine if they are really different.
1554 // If the live range overlap will map to the same value number in the
1555 // result liverange, we can still coalesce them. If not, we can't.
1556 if (LHSValNoAssignments[I->valno->id] !=
1557 RHSValNoAssignments[J->valno->id])
1561 if (I->end < J->end)
1567 // Update kill info. Some live ranges are extended due to copy coalescing.
1568 for (DenseMap<VNInfo*, VNInfo*>::iterator I = LHSValsDefinedFromRHS.begin(),
1569 E = LHSValsDefinedFromRHS.end(); I != E; ++I) {
1570 VNInfo *VNI = I->first;
1571 unsigned LHSValID = LHSValNoAssignments[VNI->id];
1572 if (VNI->hasPHIKill())
1573 NewVNInfo[LHSValID]->setHasPHIKill(true);
1576 // Update kill info. Some live ranges are extended due to copy coalescing.
1577 for (DenseMap<VNInfo*, VNInfo*>::iterator I = RHSValsDefinedFromLHS.begin(),
1578 E = RHSValsDefinedFromLHS.end(); I != E; ++I) {
1579 VNInfo *VNI = I->first;
1580 unsigned RHSValID = RHSValNoAssignments[VNI->id];
1581 if (VNI->hasPHIKill())
1582 NewVNInfo[RHSValID]->setHasPHIKill(true);
1585 if (LHSValNoAssignments.empty())
1586 LHSValNoAssignments.push_back(-1);
1587 if (RHSValNoAssignments.empty())
1588 RHSValNoAssignments.push_back(-1);
1590 SmallVector<unsigned, 8> SourceRegisters;
1591 for (SmallVector<MachineInstr*, 8>::iterator I = DupCopies.begin(),
1592 E = DupCopies.end(); I != E; ++I) {
1593 MachineInstr *MI = *I;
1595 // We have pretended that the assignment to B in
1598 // was actually a copy from A. Now that we decided to coalesce A and B,
1599 // transform the code into
1602 // and mark the X as coalesced to keep the illusion.
1603 unsigned Src = MI->getOperand(1).getReg();
1604 SourceRegisters.push_back(Src);
1605 MI->getOperand(0).substVirtReg(Src, 0, *TRI);
1610 // If B = X was the last use of X in a liverange, we have to shrink it now
1611 // that B = X is gone.
1612 for (SmallVector<unsigned, 8>::iterator I = SourceRegisters.begin(),
1613 E = SourceRegisters.end(); I != E; ++I) {
1614 LIS->shrinkToUses(&LIS->getInterval(*I));
1617 // If we get here, we know that we can coalesce the live ranges. Ask the
1618 // intervals to coalesce themselves now.
1619 LHS.join(RHS, &LHSValNoAssignments[0], &RHSValNoAssignments[0], NewVNInfo,
1625 // DepthMBBCompare - Comparison predicate that sort first based on the loop
1626 // depth of the basic block (the unsigned), and then on the MBB number.
1627 struct DepthMBBCompare {
1628 typedef std::pair<unsigned, MachineBasicBlock*> DepthMBBPair;
1629 bool operator()(const DepthMBBPair &LHS, const DepthMBBPair &RHS) const {
1630 // Deeper loops first
1631 if (LHS.first != RHS.first)
1632 return LHS.first > RHS.first;
1634 // Prefer blocks that are more connected in the CFG. This takes care of
1635 // the most difficult copies first while intervals are short.
1636 unsigned cl = LHS.second->pred_size() + LHS.second->succ_size();
1637 unsigned cr = RHS.second->pred_size() + RHS.second->succ_size();
1641 // As a last resort, sort by block number.
1642 return LHS.second->getNumber() < RHS.second->getNumber();
1648 RegisterCoalescer::copyCoalesceInMBB(MachineBasicBlock *MBB,
1649 std::vector<MachineInstr*> &TryAgain) {
1650 DEBUG(dbgs() << MBB->getName() << ":\n");
1652 SmallVector<MachineInstr*, 8> VirtCopies;
1653 SmallVector<MachineInstr*, 8> PhysCopies;
1654 SmallVector<MachineInstr*, 8> ImpDefCopies;
1655 for (MachineBasicBlock::iterator MII = MBB->begin(), E = MBB->end();
1657 MachineInstr *Inst = MII++;
1659 // If this isn't a copy nor a extract_subreg, we can't join intervals.
1660 unsigned SrcReg, DstReg;
1661 if (Inst->isCopy()) {
1662 DstReg = Inst->getOperand(0).getReg();
1663 SrcReg = Inst->getOperand(1).getReg();
1664 } else if (Inst->isSubregToReg()) {
1665 DstReg = Inst->getOperand(0).getReg();
1666 SrcReg = Inst->getOperand(2).getReg();
1670 bool SrcIsPhys = TargetRegisterInfo::isPhysicalRegister(SrcReg);
1671 bool DstIsPhys = TargetRegisterInfo::isPhysicalRegister(DstReg);
1672 if (LIS->hasInterval(SrcReg) && LIS->getInterval(SrcReg).empty())
1673 ImpDefCopies.push_back(Inst);
1674 else if (SrcIsPhys || DstIsPhys)
1675 PhysCopies.push_back(Inst);
1677 VirtCopies.push_back(Inst);
1680 // Try coalescing implicit copies and insert_subreg <undef> first,
1681 // followed by copies to / from physical registers, then finally copies
1682 // from virtual registers to virtual registers.
1683 for (unsigned i = 0, e = ImpDefCopies.size(); i != e; ++i) {
1684 MachineInstr *TheCopy = ImpDefCopies[i];
1686 if (!joinCopy(TheCopy, Again))
1688 TryAgain.push_back(TheCopy);
1690 for (unsigned i = 0, e = PhysCopies.size(); i != e; ++i) {
1691 MachineInstr *TheCopy = PhysCopies[i];
1693 if (!joinCopy(TheCopy, Again))
1695 TryAgain.push_back(TheCopy);
1697 for (unsigned i = 0, e = VirtCopies.size(); i != e; ++i) {
1698 MachineInstr *TheCopy = VirtCopies[i];
1700 if (!joinCopy(TheCopy, Again))
1702 TryAgain.push_back(TheCopy);
1706 void RegisterCoalescer::joinAllIntervals() {
1707 DEBUG(dbgs() << "********** JOINING INTERVALS ***********\n");
1709 std::vector<MachineInstr*> TryAgainList;
1710 if (Loops->empty()) {
1711 // If there are no loops in the function, join intervals in function order.
1712 for (MachineFunction::iterator I = MF->begin(), E = MF->end();
1714 copyCoalesceInMBB(I, TryAgainList);
1716 // Otherwise, join intervals in inner loops before other intervals.
1717 // Unfortunately we can't just iterate over loop hierarchy here because
1718 // there may be more MBB's than BB's. Collect MBB's for sorting.
1720 // Join intervals in the function prolog first. We want to join physical
1721 // registers with virtual registers before the intervals got too long.
1722 std::vector<std::pair<unsigned, MachineBasicBlock*> > MBBs;
1723 for (MachineFunction::iterator I = MF->begin(), E = MF->end();I != E;++I){
1724 MachineBasicBlock *MBB = I;
1725 MBBs.push_back(std::make_pair(Loops->getLoopDepth(MBB), I));
1728 // Sort by loop depth.
1729 std::sort(MBBs.begin(), MBBs.end(), DepthMBBCompare());
1731 // Finally, join intervals in loop nest order.
1732 for (unsigned i = 0, e = MBBs.size(); i != e; ++i)
1733 copyCoalesceInMBB(MBBs[i].second, TryAgainList);
1736 // Joining intervals can allow other intervals to be joined. Iteratively join
1737 // until we make no progress.
1738 bool ProgressMade = true;
1739 while (ProgressMade) {
1740 ProgressMade = false;
1742 for (unsigned i = 0, e = TryAgainList.size(); i != e; ++i) {
1743 MachineInstr *&TheCopy = TryAgainList[i];
1748 bool Success = joinCopy(TheCopy, Again);
1749 if (Success || !Again) {
1750 TheCopy= 0; // Mark this one as done.
1751 ProgressMade = true;
1757 void RegisterCoalescer::releaseMemory() {
1758 JoinedCopies.clear();
1759 ReMatCopies.clear();
1763 bool RegisterCoalescer::runOnMachineFunction(MachineFunction &fn) {
1765 MRI = &fn.getRegInfo();
1766 TM = &fn.getTarget();
1767 TRI = TM->getRegisterInfo();
1768 TII = TM->getInstrInfo();
1769 LIS = &getAnalysis<LiveIntervals>();
1770 LDV = &getAnalysis<LiveDebugVariables>();
1771 AA = &getAnalysis<AliasAnalysis>();
1772 Loops = &getAnalysis<MachineLoopInfo>();
1774 DEBUG(dbgs() << "********** SIMPLE REGISTER COALESCING **********\n"
1775 << "********** Function: "
1776 << ((Value*)MF->getFunction())->getName() << '\n');
1778 if (VerifyCoalescing)
1779 MF->verify(this, "Before register coalescing");
1781 RegClassInfo.runOnMachineFunction(fn);
1783 // Join (coalesce) intervals if requested.
1784 if (EnableJoining) {
1787 dbgs() << "********** INTERVALS POST JOINING **********\n";
1788 for (LiveIntervals::iterator I = LIS->begin(), E = LIS->end();
1790 I->second->print(dbgs(), TRI);
1796 // Perform a final pass over the instructions and compute spill weights
1797 // and remove identity moves.
1798 SmallVector<unsigned, 4> DeadDefs, InflateRegs;
1799 for (MachineFunction::iterator mbbi = MF->begin(), mbbe = MF->end();
1800 mbbi != mbbe; ++mbbi) {
1801 MachineBasicBlock* mbb = mbbi;
1802 for (MachineBasicBlock::iterator mii = mbb->begin(), mie = mbb->end();
1804 MachineInstr *MI = mii;
1805 if (JoinedCopies.count(MI)) {
1806 // Delete all coalesced copies.
1807 bool DoDelete = true;
1808 assert(MI->isCopyLike() && "Unrecognized copy instruction");
1809 unsigned SrcReg = MI->getOperand(MI->isSubregToReg() ? 2 : 1).getReg();
1810 unsigned DstReg = MI->getOperand(0).getReg();
1812 // Collect candidates for register class inflation.
1813 if (TargetRegisterInfo::isVirtualRegister(SrcReg) &&
1814 RegClassInfo.isProperSubClass(MRI->getRegClass(SrcReg)))
1815 InflateRegs.push_back(SrcReg);
1816 if (TargetRegisterInfo::isVirtualRegister(DstReg) &&
1817 RegClassInfo.isProperSubClass(MRI->getRegClass(DstReg)))
1818 InflateRegs.push_back(DstReg);
1820 if (TargetRegisterInfo::isPhysicalRegister(SrcReg) &&
1821 MI->getNumOperands() > 2)
1822 // Do not delete extract_subreg, insert_subreg of physical
1823 // registers unless the definition is dead. e.g.
1824 // %DO<def> = INSERT_SUBREG %D0<undef>, %S0<kill>, 1
1825 // or else the scavenger may complain. LowerSubregs will
1826 // delete them later.
1829 if (MI->allDefsAreDead()) {
1830 if (TargetRegisterInfo::isVirtualRegister(SrcReg) &&
1831 LIS->hasInterval(SrcReg))
1832 LIS->shrinkToUses(&LIS->getInterval(SrcReg));
1836 // We need the instruction to adjust liveness, so make it a KILL.
1837 if (MI->isSubregToReg()) {
1838 MI->RemoveOperand(3);
1839 MI->RemoveOperand(1);
1841 MI->setDesc(TII->get(TargetOpcode::KILL));
1842 mii = llvm::next(mii);
1844 LIS->RemoveMachineInstrFromMaps(MI);
1845 mii = mbbi->erase(mii);
1851 // Now check if this is a remat'ed def instruction which is now dead.
1852 if (ReMatDefs.count(MI)) {
1854 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
1855 const MachineOperand &MO = MI->getOperand(i);
1858 unsigned Reg = MO.getReg();
1861 DeadDefs.push_back(Reg);
1862 if (TargetRegisterInfo::isVirtualRegister(Reg)) {
1863 // Remat may also enable register class inflation.
1864 if (RegClassInfo.isProperSubClass(MRI->getRegClass(Reg)))
1865 InflateRegs.push_back(Reg);
1869 if (TargetRegisterInfo::isPhysicalRegister(Reg) ||
1870 !MRI->use_nodbg_empty(Reg)) {
1876 while (!DeadDefs.empty()) {
1877 unsigned DeadDef = DeadDefs.back();
1878 DeadDefs.pop_back();
1879 removeDeadDef(LIS->getInterval(DeadDef), MI);
1881 LIS->RemoveMachineInstrFromMaps(mii);
1882 mii = mbbi->erase(mii);
1890 // Check for now unnecessary kill flags.
1891 if (LIS->isNotInMIMap(MI)) continue;
1892 SlotIndex DefIdx = LIS->getInstructionIndex(MI).getRegSlot();
1893 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
1894 MachineOperand &MO = MI->getOperand(i);
1895 if (!MO.isReg() || !MO.isKill()) continue;
1896 unsigned reg = MO.getReg();
1897 if (!reg || !LIS->hasInterval(reg)) continue;
1898 if (!LIS->getInterval(reg).killedAt(DefIdx)) {
1899 MO.setIsKill(false);
1902 // When leaving a kill flag on a physreg, check if any subregs should
1904 if (!TargetRegisterInfo::isPhysicalRegister(reg))
1906 for (const uint16_t *SR = TRI->getSubRegisters(reg);
1907 unsigned S = *SR; ++SR)
1908 if (LIS->hasInterval(S) && LIS->getInterval(S).liveAt(DefIdx))
1909 MI->addRegisterDefined(S, TRI);
1914 // After deleting a lot of copies, register classes may be less constrained.
1915 // Removing sub-register opreands may alow GR32_ABCD -> GR32 and DPR_VFP2 ->
1917 array_pod_sort(InflateRegs.begin(), InflateRegs.end());
1918 InflateRegs.erase(std::unique(InflateRegs.begin(), InflateRegs.end()),
1920 DEBUG(dbgs() << "Trying to inflate " << InflateRegs.size() << " regs.\n");
1921 for (unsigned i = 0, e = InflateRegs.size(); i != e; ++i) {
1922 unsigned Reg = InflateRegs[i];
1923 if (MRI->reg_nodbg_empty(Reg))
1925 if (MRI->recomputeRegClass(Reg, *TM)) {
1926 DEBUG(dbgs() << PrintReg(Reg) << " inflated to "
1927 << MRI->getRegClass(Reg)->getName() << '\n');
1934 if (VerifyCoalescing)
1935 MF->verify(this, "After register coalescing");
1939 /// print - Implement the dump method.
1940 void RegisterCoalescer::print(raw_ostream &O, const Module* m) const {