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 #include "RegisterCoalescer.h"
17 #include "llvm/ADT/STLExtras.h"
18 #include "llvm/ADT/SmallSet.h"
19 #include "llvm/ADT/Statistic.h"
20 #include "llvm/Analysis/AliasAnalysis.h"
21 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
22 #include "llvm/CodeGen/LiveRangeEdit.h"
23 #include "llvm/CodeGen/MachineFrameInfo.h"
24 #include "llvm/CodeGen/MachineInstr.h"
25 #include "llvm/CodeGen/MachineLoopInfo.h"
26 #include "llvm/CodeGen/MachineRegisterInfo.h"
27 #include "llvm/CodeGen/Passes.h"
28 #include "llvm/CodeGen/RegisterClassInfo.h"
29 #include "llvm/CodeGen/VirtRegMap.h"
30 #include "llvm/IR/Value.h"
31 #include "llvm/Pass.h"
32 #include "llvm/Support/CommandLine.h"
33 #include "llvm/Support/Debug.h"
34 #include "llvm/Support/ErrorHandling.h"
35 #include "llvm/Support/Format.h"
36 #include "llvm/Support/raw_ostream.h"
37 #include "llvm/Target/TargetInstrInfo.h"
38 #include "llvm/Target/TargetMachine.h"
39 #include "llvm/Target/TargetRegisterInfo.h"
40 #include "llvm/Target/TargetSubtargetInfo.h"
45 #define DEBUG_TYPE "regalloc"
47 STATISTIC(numJoins , "Number of interval joins performed");
48 STATISTIC(numCrossRCs , "Number of cross class joins performed");
49 STATISTIC(numCommutes , "Number of instruction commuting performed");
50 STATISTIC(numExtends , "Number of copies extended");
51 STATISTIC(NumReMats , "Number of instructions re-materialized");
52 STATISTIC(NumInflated , "Number of register classes inflated");
53 STATISTIC(NumLaneConflicts, "Number of dead lane conflicts tested");
54 STATISTIC(NumLaneResolves, "Number of dead lane conflicts resolved");
57 EnableJoining("join-liveintervals",
58 cl::desc("Coalesce copies (default=true)"),
61 // Temporary flag to test critical edge unsplitting.
63 EnableJoinSplits("join-splitedges",
64 cl::desc("Coalesce copies on split edges (default=subtarget)"), cl::Hidden);
66 // Temporary flag to test global copy optimization.
67 static cl::opt<cl::boolOrDefault>
68 EnableGlobalCopies("join-globalcopies",
69 cl::desc("Coalesce copies that span blocks (default=subtarget)"),
70 cl::init(cl::BOU_UNSET), cl::Hidden);
73 VerifyCoalescing("verify-coalescing",
74 cl::desc("Verify machine instrs before and after register coalescing"),
78 class RegisterCoalescer : public MachineFunctionPass,
79 private LiveRangeEdit::Delegate {
81 MachineRegisterInfo* MRI;
82 const TargetMachine* TM;
83 const TargetRegisterInfo* TRI;
84 const TargetInstrInfo* TII;
86 const MachineLoopInfo* Loops;
88 RegisterClassInfo RegClassInfo;
90 /// A LaneMask to remember on which subregister live ranges we need to call
91 /// shrinkToUses() later.
94 /// True if the main range of the currently coalesced intervals should be
95 /// checked for smaller live intervals.
98 /// \brief True if the coalescer should aggressively coalesce global copies
99 /// in favor of keeping local copies.
100 bool JoinGlobalCopies;
102 /// \brief True if the coalescer should aggressively coalesce fall-thru
103 /// blocks exclusively containing copies.
106 /// Copy instructions yet to be coalesced.
107 SmallVector<MachineInstr*, 8> WorkList;
108 SmallVector<MachineInstr*, 8> LocalWorkList;
110 /// Set of instruction pointers that have been erased, and
111 /// that may be present in WorkList.
112 SmallPtrSet<MachineInstr*, 8> ErasedInstrs;
114 /// Dead instructions that are about to be deleted.
115 SmallVector<MachineInstr*, 8> DeadDefs;
117 /// Virtual registers to be considered for register class inflation.
118 SmallVector<unsigned, 8> InflateRegs;
120 /// Recursively eliminate dead defs in DeadDefs.
121 void eliminateDeadDefs();
123 /// LiveRangeEdit callback.
124 void LRE_WillEraseInstruction(MachineInstr *MI) override;
126 /// Coalesce the LocalWorkList.
127 void coalesceLocals();
129 /// Join compatible live intervals
130 void joinAllIntervals();
132 /// Coalesce copies in the specified MBB, putting
133 /// copies that cannot yet be coalesced into WorkList.
134 void copyCoalesceInMBB(MachineBasicBlock *MBB);
136 /// Try to coalesce all copies in CurrList. Return
137 /// true if any progress was made.
138 bool copyCoalesceWorkList(MutableArrayRef<MachineInstr*> CurrList);
140 /// Attempt to join intervals corresponding to SrcReg/DstReg,
141 /// which are the src/dst of the copy instruction CopyMI. This returns
142 /// true if the copy was successfully coalesced away. If it is not
143 /// currently possible to coalesce this interval, but it may be possible if
144 /// other things get coalesced, then it returns true by reference in
146 bool joinCopy(MachineInstr *TheCopy, bool &Again);
148 /// Attempt to join these two intervals. On failure, this
149 /// returns false. The output "SrcInt" will not have been modified, so we
150 /// can use this information below to update aliases.
151 bool joinIntervals(CoalescerPair &CP);
153 /// Attempt joining two virtual registers. Return true on success.
154 bool joinVirtRegs(CoalescerPair &CP);
156 /// Attempt joining with a reserved physreg.
157 bool joinReservedPhysReg(CoalescerPair &CP);
159 /// Add the LiveRange @p ToMerge as a subregister liverange of @p LI.
160 /// Subranges in @p LI which only partially interfere with the desired
161 /// LaneMask are split as necessary. @p LaneMask are the lanes that
162 /// @p ToMerge will occupy in the coalescer register. @p LI has its subrange
163 /// lanemasks already adjusted to the coalesced register.
164 void mergeSubRangeInto(LiveInterval &LI, const LiveRange &ToMerge,
165 unsigned LaneMask, CoalescerPair &CP);
167 /// Join the liveranges of two subregisters. Joins @p RRange into
168 /// @p LRange, @p RRange may be invalid afterwards.
169 void joinSubRegRanges(LiveRange &LRange, LiveRange &RRange,
170 unsigned LaneMask, const CoalescerPair &CP);
172 /// We found a non-trivially-coalescable copy. If
173 /// the source value number is defined by a copy from the destination reg
174 /// see if we can merge these two destination reg valno# into a single
175 /// value number, eliminating a copy.
176 bool adjustCopiesBackFrom(const CoalescerPair &CP, MachineInstr *CopyMI);
178 /// Return true if there are definitions of IntB
179 /// other than BValNo val# that can reach uses of AValno val# of IntA.
180 bool hasOtherReachingDefs(LiveInterval &IntA, LiveInterval &IntB,
181 VNInfo *AValNo, VNInfo *BValNo);
183 /// We found a non-trivially-coalescable copy.
184 /// If the source value number is defined by a commutable instruction and
185 /// its other operand is coalesced to the copy dest register, see if we
186 /// can transform the copy into a noop by commuting the definition.
187 bool removeCopyByCommutingDef(const CoalescerPair &CP,MachineInstr *CopyMI);
189 /// If the source of a copy is defined by a
190 /// trivial computation, replace the copy by rematerialize the definition.
191 bool reMaterializeTrivialDef(CoalescerPair &CP, MachineInstr *CopyMI,
194 /// Return true if a physreg copy should be joined.
195 bool canJoinPhys(const CoalescerPair &CP);
197 /// Replace all defs and uses of SrcReg to DstReg and
198 /// update the subregister number if it is not zero. If DstReg is a
199 /// physical register and the existing subregister number of the def / use
200 /// being updated is not zero, make sure to set it to the correct physical
202 void updateRegDefsUses(unsigned SrcReg, unsigned DstReg, unsigned SubIdx);
204 /// Handle copies of undef values.
205 bool eliminateUndefCopy(MachineInstr *CopyMI);
208 static char ID; // Class identification, replacement for typeinfo
209 RegisterCoalescer() : MachineFunctionPass(ID) {
210 initializeRegisterCoalescerPass(*PassRegistry::getPassRegistry());
213 void getAnalysisUsage(AnalysisUsage &AU) const override;
215 void releaseMemory() override;
217 /// This is the pass entry point.
218 bool runOnMachineFunction(MachineFunction&) override;
220 /// Implement the dump method.
221 void print(raw_ostream &O, const Module* = nullptr) const override;
223 } /// end anonymous namespace
225 char &llvm::RegisterCoalescerID = RegisterCoalescer::ID;
227 INITIALIZE_PASS_BEGIN(RegisterCoalescer, "simple-register-coalescing",
228 "Simple Register Coalescing", false, false)
229 INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
230 INITIALIZE_PASS_DEPENDENCY(SlotIndexes)
231 INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
232 INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
233 INITIALIZE_PASS_END(RegisterCoalescer, "simple-register-coalescing",
234 "Simple Register Coalescing", false, false)
236 char RegisterCoalescer::ID = 0;
238 static bool isMoveInstr(const TargetRegisterInfo &tri, const MachineInstr *MI,
239 unsigned &Src, unsigned &Dst,
240 unsigned &SrcSub, unsigned &DstSub) {
242 Dst = MI->getOperand(0).getReg();
243 DstSub = MI->getOperand(0).getSubReg();
244 Src = MI->getOperand(1).getReg();
245 SrcSub = MI->getOperand(1).getSubReg();
246 } else if (MI->isSubregToReg()) {
247 Dst = MI->getOperand(0).getReg();
248 DstSub = tri.composeSubRegIndices(MI->getOperand(0).getSubReg(),
249 MI->getOperand(3).getImm());
250 Src = MI->getOperand(2).getReg();
251 SrcSub = MI->getOperand(2).getSubReg();
257 // Return true if this block should be vacated by the coalescer to eliminate
258 // branches. The important cases to handle in the coalescer are critical edges
259 // split during phi elimination which contain only copies. Simple blocks that
260 // contain non-branches should also be vacated, but this can be handled by an
261 // earlier pass similar to early if-conversion.
262 static bool isSplitEdge(const MachineBasicBlock *MBB) {
263 if (MBB->pred_size() != 1 || MBB->succ_size() != 1)
266 for (const auto &MI : *MBB) {
267 if (!MI.isCopyLike() && !MI.isUnconditionalBranch())
273 bool CoalescerPair::setRegisters(const MachineInstr *MI) {
277 Flipped = CrossClass = false;
279 unsigned Src, Dst, SrcSub, DstSub;
280 if (!isMoveInstr(TRI, MI, Src, Dst, SrcSub, DstSub))
282 Partial = SrcSub || DstSub;
284 // If one register is a physreg, it must be Dst.
285 if (TargetRegisterInfo::isPhysicalRegister(Src)) {
286 if (TargetRegisterInfo::isPhysicalRegister(Dst))
289 std::swap(SrcSub, DstSub);
293 const MachineRegisterInfo &MRI = MI->getParent()->getParent()->getRegInfo();
295 if (TargetRegisterInfo::isPhysicalRegister(Dst)) {
296 // Eliminate DstSub on a physreg.
298 Dst = TRI.getSubReg(Dst, DstSub);
299 if (!Dst) return false;
303 // Eliminate SrcSub by picking a corresponding Dst superregister.
305 Dst = TRI.getMatchingSuperReg(Dst, SrcSub, MRI.getRegClass(Src));
306 if (!Dst) return false;
307 } else if (!MRI.getRegClass(Src)->contains(Dst)) {
311 // Both registers are virtual.
312 const TargetRegisterClass *SrcRC = MRI.getRegClass(Src);
313 const TargetRegisterClass *DstRC = MRI.getRegClass(Dst);
315 // Both registers have subreg indices.
316 if (SrcSub && DstSub) {
317 // Copies between different sub-registers are never coalescable.
318 if (Src == Dst && SrcSub != DstSub)
321 NewRC = TRI.getCommonSuperRegClass(SrcRC, SrcSub, DstRC, DstSub,
326 // SrcReg will be merged with a sub-register of DstReg.
328 NewRC = TRI.getMatchingSuperRegClass(DstRC, SrcRC, DstSub);
330 // DstReg will be merged with a sub-register of SrcReg.
332 NewRC = TRI.getMatchingSuperRegClass(SrcRC, DstRC, SrcSub);
334 // This is a straight copy without sub-registers.
335 NewRC = TRI.getCommonSubClass(DstRC, SrcRC);
338 // The combined constraint may be impossible to satisfy.
342 // Prefer SrcReg to be a sub-register of DstReg.
343 // FIXME: Coalescer should support subregs symmetrically.
344 if (DstIdx && !SrcIdx) {
346 std::swap(SrcIdx, DstIdx);
350 CrossClass = NewRC != DstRC || NewRC != SrcRC;
352 // Check our invariants
353 assert(TargetRegisterInfo::isVirtualRegister(Src) && "Src must be virtual");
354 assert(!(TargetRegisterInfo::isPhysicalRegister(Dst) && DstSub) &&
355 "Cannot have a physical SubIdx");
361 bool CoalescerPair::flip() {
362 if (TargetRegisterInfo::isPhysicalRegister(DstReg))
364 std::swap(SrcReg, DstReg);
365 std::swap(SrcIdx, DstIdx);
370 bool CoalescerPair::isCoalescable(const MachineInstr *MI) const {
373 unsigned Src, Dst, SrcSub, DstSub;
374 if (!isMoveInstr(TRI, MI, Src, Dst, SrcSub, DstSub))
377 // Find the virtual register that is SrcReg.
380 std::swap(SrcSub, DstSub);
381 } else if (Src != SrcReg) {
385 // Now check that Dst matches DstReg.
386 if (TargetRegisterInfo::isPhysicalRegister(DstReg)) {
387 if (!TargetRegisterInfo::isPhysicalRegister(Dst))
389 assert(!DstIdx && !SrcIdx && "Inconsistent CoalescerPair state.");
390 // DstSub could be set for a physreg from INSERT_SUBREG.
392 Dst = TRI.getSubReg(Dst, DstSub);
395 return DstReg == Dst;
396 // This is a partial register copy. Check that the parts match.
397 return TRI.getSubReg(DstReg, SrcSub) == Dst;
399 // DstReg is virtual.
402 // Registers match, do the subregisters line up?
403 return TRI.composeSubRegIndices(SrcIdx, SrcSub) ==
404 TRI.composeSubRegIndices(DstIdx, DstSub);
408 void RegisterCoalescer::getAnalysisUsage(AnalysisUsage &AU) const {
409 AU.setPreservesCFG();
410 AU.addRequired<AliasAnalysis>();
411 AU.addRequired<LiveIntervals>();
412 AU.addPreserved<LiveIntervals>();
413 AU.addPreserved<SlotIndexes>();
414 AU.addRequired<MachineLoopInfo>();
415 AU.addPreserved<MachineLoopInfo>();
416 AU.addPreservedID(MachineDominatorsID);
417 MachineFunctionPass::getAnalysisUsage(AU);
420 void RegisterCoalescer::eliminateDeadDefs() {
421 SmallVector<unsigned, 8> NewRegs;
422 LiveRangeEdit(nullptr, NewRegs, *MF, *LIS,
423 nullptr, this).eliminateDeadDefs(DeadDefs);
426 // Callback from eliminateDeadDefs().
427 void RegisterCoalescer::LRE_WillEraseInstruction(MachineInstr *MI) {
428 // MI may be in WorkList. Make sure we don't visit it.
429 ErasedInstrs.insert(MI);
432 /// We found a non-trivially-coalescable copy with IntA
433 /// being the source and IntB being the dest, thus this defines a value number
434 /// in IntB. If the source value number (in IntA) is defined by a copy from B,
435 /// see if we can merge these two pieces of B into a single value number,
436 /// eliminating a copy. For example:
440 /// B1 = A3 <- this copy
442 /// In this case, B0 can be extended to where the B1 copy lives, allowing the B1
443 /// value number to be replaced with B0 (which simplifies the B liveinterval).
445 /// This returns true if an interval was modified.
447 bool RegisterCoalescer::adjustCopiesBackFrom(const CoalescerPair &CP,
448 MachineInstr *CopyMI) {
449 assert(!CP.isPartial() && "This doesn't work for partial copies.");
450 assert(!CP.isPhys() && "This doesn't work for physreg copies.");
453 LIS->getInterval(CP.isFlipped() ? CP.getDstReg() : CP.getSrcReg());
455 LIS->getInterval(CP.isFlipped() ? CP.getSrcReg() : CP.getDstReg());
456 SlotIndex CopyIdx = LIS->getInstructionIndex(CopyMI).getRegSlot();
458 // BValNo is a value number in B that is defined by a copy from A. 'B1' in
459 // the example above.
460 LiveInterval::iterator BS = IntB.FindSegmentContaining(CopyIdx);
461 if (BS == IntB.end()) return false;
462 VNInfo *BValNo = BS->valno;
464 // Get the location that B is defined at. Two options: either this value has
465 // an unknown definition point or it is defined at CopyIdx. If unknown, we
467 if (BValNo->def != CopyIdx) return false;
469 // AValNo is the value number in A that defines the copy, A3 in the example.
470 SlotIndex CopyUseIdx = CopyIdx.getRegSlot(true);
471 LiveInterval::iterator AS = IntA.FindSegmentContaining(CopyUseIdx);
472 // The live segment might not exist after fun with physreg coalescing.
473 if (AS == IntA.end()) return false;
474 VNInfo *AValNo = AS->valno;
476 // If AValNo is defined as a copy from IntB, we can potentially process this.
477 // Get the instruction that defines this value number.
478 MachineInstr *ACopyMI = LIS->getInstructionFromIndex(AValNo->def);
479 // Don't allow any partial copies, even if isCoalescable() allows them.
480 if (!CP.isCoalescable(ACopyMI) || !ACopyMI->isFullCopy())
483 // Get the Segment in IntB that this value number starts with.
484 LiveInterval::iterator ValS =
485 IntB.FindSegmentContaining(AValNo->def.getPrevSlot());
486 if (ValS == IntB.end())
489 // Make sure that the end of the live segment is inside the same block as
491 MachineInstr *ValSEndInst =
492 LIS->getInstructionFromIndex(ValS->end.getPrevSlot());
493 if (!ValSEndInst || ValSEndInst->getParent() != CopyMI->getParent())
496 // Okay, we now know that ValS ends in the same block that the CopyMI
497 // live-range starts. If there are no intervening live segments between them
498 // in IntB, we can merge them.
499 if (ValS+1 != BS) return false;
501 DEBUG(dbgs() << "Extending: " << PrintReg(IntB.reg, TRI));
503 SlotIndex FillerStart = ValS->end, FillerEnd = BS->start;
504 // We are about to delete CopyMI, so need to remove it as the 'instruction
505 // that defines this value #'. Update the valnum with the new defining
507 BValNo->def = FillerStart;
509 // Okay, we can merge them. We need to insert a new liverange:
510 // [ValS.end, BS.begin) of either value number, then we merge the
511 // two value numbers.
512 IntB.addSegment(LiveInterval::Segment(FillerStart, FillerEnd, BValNo));
514 // Okay, merge "B1" into the same value number as "B0".
515 if (BValNo != ValS->valno)
516 IntB.MergeValueNumberInto(BValNo, ValS->valno);
518 // Do the same for the subregister segments.
519 for (LiveInterval::SubRange &S : IntB.subranges()) {
520 VNInfo *SubBValNo = S.getVNInfoAt(CopyIdx);
521 S.addSegment(LiveInterval::Segment(FillerStart, FillerEnd, SubBValNo));
522 VNInfo *SubValSNo = S.getVNInfoAt(AValNo->def.getPrevSlot());
523 if (SubBValNo != SubValSNo)
524 S.MergeValueNumberInto(SubBValNo, SubValSNo);
527 DEBUG(dbgs() << " result = " << IntB << '\n');
529 // If the source instruction was killing the source register before the
530 // merge, unset the isKill marker given the live range has been extended.
531 int UIdx = ValSEndInst->findRegisterUseOperandIdx(IntB.reg, true);
533 ValSEndInst->getOperand(UIdx).setIsKill(false);
536 // Rewrite the copy. If the copy instruction was killing the destination
537 // register before the merge, find the last use and trim the live range. That
538 // will also add the isKill marker.
539 CopyMI->substituteRegister(IntA.reg, IntB.reg, 0, *TRI);
540 if (AS->end == CopyIdx)
541 LIS->shrinkToUses(&IntA);
547 /// Return true if there are definitions of IntB
548 /// other than BValNo val# that can reach uses of AValno val# of IntA.
549 bool RegisterCoalescer::hasOtherReachingDefs(LiveInterval &IntA,
553 // If AValNo has PHI kills, conservatively assume that IntB defs can reach
555 if (LIS->hasPHIKill(IntA, AValNo))
558 for (LiveRange::Segment &ASeg : IntA.segments) {
559 if (ASeg.valno != AValNo) continue;
560 LiveInterval::iterator BI =
561 std::upper_bound(IntB.begin(), IntB.end(), ASeg.start);
562 if (BI != IntB.begin())
564 for (; BI != IntB.end() && ASeg.end >= BI->start; ++BI) {
565 if (BI->valno == BValNo)
567 if (BI->start <= ASeg.start && BI->end > ASeg.start)
569 if (BI->start > ASeg.start && BI->start < ASeg.end)
576 /// Copy segements with value number @p SrcValNo from liverange @p Src to live
577 /// range @Dst and use value number @p DstValNo there.
578 static void addSegmentsWithValNo(LiveRange &Dst, VNInfo *DstValNo,
579 const LiveRange &Src, const VNInfo *SrcValNo)
581 for (const LiveRange::Segment &S : Src.segments) {
582 if (S.valno != SrcValNo)
584 Dst.addSegment(LiveRange::Segment(S.start, S.end, DstValNo));
588 /// We found a non-trivially-coalescable copy with
589 /// IntA being the source and IntB being the dest, thus this defines a value
590 /// number in IntB. If the source value number (in IntA) is defined by a
591 /// commutable instruction and its other operand is coalesced to the copy dest
592 /// register, see if we can transform the copy into a noop by commuting the
593 /// definition. For example,
595 /// A3 = op A2 B0<kill>
597 /// B1 = A3 <- this copy
599 /// = op A3 <- more uses
603 /// B2 = op B0 A2<kill>
605 /// B1 = B2 <- now an identity copy
607 /// = op B2 <- more uses
609 /// This returns true if an interval was modified.
611 bool RegisterCoalescer::removeCopyByCommutingDef(const CoalescerPair &CP,
612 MachineInstr *CopyMI) {
613 assert(!CP.isPhys());
616 LIS->getInterval(CP.isFlipped() ? CP.getDstReg() : CP.getSrcReg());
618 LIS->getInterval(CP.isFlipped() ? CP.getSrcReg() : CP.getDstReg());
620 // BValNo is a value number in B that is defined by a copy from A. 'B1' in
621 // the example above.
622 SlotIndex CopyIdx = LIS->getInstructionIndex(CopyMI).getRegSlot();
623 VNInfo *BValNo = IntB.getVNInfoAt(CopyIdx);
624 assert(BValNo != nullptr && BValNo->def == CopyIdx);
626 // AValNo is the value number in A that defines the copy, A3 in the example.
627 VNInfo *AValNo = IntA.getVNInfoAt(CopyIdx.getRegSlot(true));
628 assert(AValNo && !AValNo->isUnused() && "COPY source not live");
629 if (AValNo->isPHIDef())
631 MachineInstr *DefMI = LIS->getInstructionFromIndex(AValNo->def);
634 if (!DefMI->isCommutable())
636 // If DefMI is a two-address instruction then commuting it will change the
637 // destination register.
638 int DefIdx = DefMI->findRegisterDefOperandIdx(IntA.reg);
639 assert(DefIdx != -1);
641 if (!DefMI->isRegTiedToUseOperand(DefIdx, &UseOpIdx))
643 unsigned Op1, Op2, NewDstIdx;
644 if (!TII->findCommutedOpIndices(DefMI, Op1, Op2))
648 else if (Op2 == UseOpIdx)
653 MachineOperand &NewDstMO = DefMI->getOperand(NewDstIdx);
654 unsigned NewReg = NewDstMO.getReg();
655 if (NewReg != IntB.reg || !IntB.Query(AValNo->def).isKill())
658 // Make sure there are no other definitions of IntB that would reach the
659 // uses which the new definition can reach.
660 if (hasOtherReachingDefs(IntA, IntB, AValNo, BValNo))
663 // If some of the uses of IntA.reg is already coalesced away, return false.
664 // It's not possible to determine whether it's safe to perform the coalescing.
665 for (MachineOperand &MO : MRI->use_nodbg_operands(IntA.reg)) {
666 MachineInstr *UseMI = MO.getParent();
667 unsigned OpNo = &MO - &UseMI->getOperand(0);
668 SlotIndex UseIdx = LIS->getInstructionIndex(UseMI);
669 LiveInterval::iterator US = IntA.FindSegmentContaining(UseIdx);
670 if (US == IntA.end() || US->valno != AValNo)
672 // If this use is tied to a def, we can't rewrite the register.
673 if (UseMI->isRegTiedToDefOperand(OpNo))
677 DEBUG(dbgs() << "\tremoveCopyByCommutingDef: " << AValNo->def << '\t'
680 // At this point we have decided that it is legal to do this
681 // transformation. Start by commuting the instruction.
682 MachineBasicBlock *MBB = DefMI->getParent();
683 MachineInstr *NewMI = TII->commuteInstruction(DefMI);
686 if (TargetRegisterInfo::isVirtualRegister(IntA.reg) &&
687 TargetRegisterInfo::isVirtualRegister(IntB.reg) &&
688 !MRI->constrainRegClass(IntB.reg, MRI->getRegClass(IntA.reg)))
690 if (NewMI != DefMI) {
691 LIS->ReplaceMachineInstrInMaps(DefMI, NewMI);
692 MachineBasicBlock::iterator Pos = DefMI;
693 MBB->insert(Pos, NewMI);
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),
709 UI != UE; /* ++UI is below because of possible MI removal */) {
710 MachineOperand &UseMO = *UI;
714 MachineInstr *UseMI = UseMO.getParent();
715 if (UseMI->isDebugValue()) {
716 // FIXME These don't have an instruction index. Not clear we have enough
717 // info to decide whether to do this replacement or not. For now do it.
718 UseMO.setReg(NewReg);
721 SlotIndex UseIdx = LIS->getInstructionIndex(UseMI).getRegSlot(true);
722 LiveInterval::iterator US = IntA.FindSegmentContaining(UseIdx);
723 assert(US != IntA.end() && "Use must be live");
724 if (US->valno != AValNo)
726 // Kill flags are no longer accurate. They are recomputed after RA.
727 UseMO.setIsKill(false);
728 if (TargetRegisterInfo::isPhysicalRegister(NewReg))
729 UseMO.substPhysReg(NewReg, *TRI);
731 UseMO.setReg(NewReg);
734 if (!UseMI->isCopy())
736 if (UseMI->getOperand(0).getReg() != IntB.reg ||
737 UseMI->getOperand(0).getSubReg())
740 // This copy will become a noop. If it's defining a new val#, merge it into
742 SlotIndex DefIdx = UseIdx.getRegSlot();
743 VNInfo *DVNI = IntB.getVNInfoAt(DefIdx);
746 DEBUG(dbgs() << "\t\tnoop: " << DefIdx << '\t' << *UseMI);
747 assert(DVNI->def == DefIdx);
748 BValNo = IntB.MergeValueNumberInto(BValNo, DVNI);
749 for (LiveInterval::SubRange &S : IntB.subranges()) {
750 VNInfo *SubDVNI = S.getVNInfoAt(DefIdx);
753 VNInfo *SubBValNo = S.getVNInfoAt(CopyIdx);
754 assert(SubBValNo->def == CopyIdx);
755 VNInfo *Merged = S.MergeValueNumberInto(SubBValNo, SubDVNI);
756 Merged->def = CopyIdx;
759 ErasedInstrs.insert(UseMI);
760 LIS->RemoveMachineInstrFromMaps(UseMI);
761 UseMI->eraseFromParent();
764 // Extend BValNo by merging in IntA live segments of AValNo. Val# definition
766 BumpPtrAllocator &Allocator = LIS->getVNInfoAllocator();
767 if (IntB.hasSubRanges()) {
768 if (!IntA.hasSubRanges()) {
769 unsigned Mask = MRI->getMaxLaneMaskForVReg(IntA.reg);
770 IntA.createSubRangeFrom(Allocator, Mask, IntA);
772 SlotIndex AIdx = CopyIdx.getRegSlot(true);
773 for (LiveInterval::SubRange &SA : IntA.subranges()) {
774 VNInfo *ASubValNo = SA.getVNInfoAt(AIdx);
775 assert(ASubValNo != nullptr);
777 unsigned AMask = SA.LaneMask;
778 for (LiveInterval::SubRange &SB : IntB.subranges()) {
779 unsigned BMask = SB.LaneMask;
780 unsigned Common = BMask & AMask;
785 dbgs() << format("\t\tCopy+Merge %04X into %04X\n", BMask, Common));
786 unsigned BRest = BMask & ~AMask;
787 LiveInterval::SubRange *CommonRange;
790 DEBUG(dbgs() << format("\t\tReduce Lane to %04X\n", BRest));
791 // Duplicate SubRange for newly merged common stuff.
792 CommonRange = IntB.createSubRangeFrom(Allocator, Common, SB);
794 // We van reuse the L SubRange.
795 SB.LaneMask = Common;
798 LiveRange RangeCopy(SB, Allocator);
800 VNInfo *BSubValNo = CommonRange->getVNInfoAt(CopyIdx);
801 assert(BSubValNo->def == CopyIdx);
802 BSubValNo->def = ASubValNo->def;
803 addSegmentsWithValNo(*CommonRange, BSubValNo, SA, ASubValNo);
807 DEBUG(dbgs() << format("\t\tNew Lane %04X\n", AMask));
808 LiveRange *NewRange = IntB.createSubRange(Allocator, AMask);
809 VNInfo *BSubValNo = NewRange->getNextValue(CopyIdx, Allocator);
810 addSegmentsWithValNo(*NewRange, BSubValNo, SA, ASubValNo);
812 SA.removeValNo(ASubValNo);
816 BValNo->def = AValNo->def;
817 addSegmentsWithValNo(IntB, BValNo, IntA, AValNo);
818 DEBUG(dbgs() << "\t\textended: " << IntB << '\n');
820 IntA.removeValNo(AValNo);
821 // Remove valuenos in subranges (the A+B have subranges case has already been
823 if (!IntB.hasSubRanges()) {
824 SlotIndex AIdx = CopyIdx.getRegSlot(true);
825 for (LiveInterval::SubRange &SA : IntA.subranges()) {
826 VNInfo *ASubValNo = SA.getVNInfoAt(AIdx);
827 assert(ASubValNo != nullptr);
828 SA.removeValNo(ASubValNo);
831 DEBUG(dbgs() << "\t\ttrimmed: " << IntA << '\n');
836 /// If the source of a copy is defined by a trivial
837 /// computation, replace the copy by rematerialize the definition.
838 bool RegisterCoalescer::reMaterializeTrivialDef(CoalescerPair &CP,
839 MachineInstr *CopyMI,
842 unsigned SrcReg = CP.isFlipped() ? CP.getDstReg() : CP.getSrcReg();
843 unsigned SrcIdx = CP.isFlipped() ? CP.getDstIdx() : CP.getSrcIdx();
844 unsigned DstReg = CP.isFlipped() ? CP.getSrcReg() : CP.getDstReg();
845 unsigned DstIdx = CP.isFlipped() ? CP.getSrcIdx() : CP.getDstIdx();
846 if (TargetRegisterInfo::isPhysicalRegister(SrcReg))
849 LiveInterval &SrcInt = LIS->getInterval(SrcReg);
850 SlotIndex CopyIdx = LIS->getInstructionIndex(CopyMI);
851 VNInfo *ValNo = SrcInt.Query(CopyIdx).valueIn();
852 assert(ValNo && "CopyMI input register not live");
853 if (ValNo->isPHIDef() || ValNo->isUnused())
855 MachineInstr *DefMI = LIS->getInstructionFromIndex(ValNo->def);
858 if (DefMI->isCopyLike()) {
862 if (!TII->isAsCheapAsAMove(DefMI))
864 if (!TII->isTriviallyReMaterializable(DefMI, AA))
866 bool SawStore = false;
867 if (!DefMI->isSafeToMove(TII, AA, SawStore))
869 const MCInstrDesc &MCID = DefMI->getDesc();
870 if (MCID.getNumDefs() != 1)
872 // Only support subregister destinations when the def is read-undef.
873 MachineOperand &DstOperand = CopyMI->getOperand(0);
874 unsigned CopyDstReg = DstOperand.getReg();
875 if (DstOperand.getSubReg() && !DstOperand.isUndef())
878 // If both SrcIdx and DstIdx are set, correct rematerialization would widen
879 // the register substantially (beyond both source and dest size). This is bad
880 // for performance since it can cascade through a function, introducing many
881 // extra spills and fills (e.g. ARM can easily end up copying QQQQPR registers
882 // around after a few subreg copies).
883 if (SrcIdx && DstIdx)
886 const TargetRegisterClass *DefRC = TII->getRegClass(MCID, 0, TRI, *MF);
887 if (!DefMI->isImplicitDef()) {
888 if (TargetRegisterInfo::isPhysicalRegister(DstReg)) {
889 unsigned NewDstReg = DstReg;
891 unsigned NewDstIdx = TRI->composeSubRegIndices(CP.getSrcIdx(),
892 DefMI->getOperand(0).getSubReg());
894 NewDstReg = TRI->getSubReg(DstReg, NewDstIdx);
896 // Finally, make sure that the physical subregister that will be
897 // constructed later is permitted for the instruction.
898 if (!DefRC->contains(NewDstReg))
901 // Theoretically, some stack frame reference could exist. Just make sure
902 // it hasn't actually happened.
903 assert(TargetRegisterInfo::isVirtualRegister(DstReg) &&
904 "Only expect to deal with virtual or physical registers");
908 MachineBasicBlock *MBB = CopyMI->getParent();
909 MachineBasicBlock::iterator MII =
910 std::next(MachineBasicBlock::iterator(CopyMI));
911 TII->reMaterialize(*MBB, MII, DstReg, SrcIdx, DefMI, *TRI);
912 MachineInstr *NewMI = std::prev(MII);
914 LIS->ReplaceMachineInstrInMaps(CopyMI, NewMI);
915 CopyMI->eraseFromParent();
916 ErasedInstrs.insert(CopyMI);
918 // NewMI may have dead implicit defs (E.g. EFLAGS for MOV<bits>r0 on X86).
919 // We need to remember these so we can add intervals once we insert
920 // NewMI into SlotIndexes.
921 SmallVector<unsigned, 4> NewMIImplDefs;
922 for (unsigned i = NewMI->getDesc().getNumOperands(),
923 e = NewMI->getNumOperands(); i != e; ++i) {
924 MachineOperand &MO = NewMI->getOperand(i);
926 assert(MO.isDef() && MO.isImplicit() && MO.isDead() &&
927 TargetRegisterInfo::isPhysicalRegister(MO.getReg()));
928 NewMIImplDefs.push_back(MO.getReg());
932 if (TargetRegisterInfo::isVirtualRegister(DstReg)) {
933 const TargetRegisterClass *NewRC = CP.getNewRC();
934 unsigned NewIdx = NewMI->getOperand(0).getSubReg();
937 NewRC = TRI->getMatchingSuperRegClass(NewRC, DefRC, NewIdx);
939 NewRC = TRI->getCommonSubClass(NewRC, DefRC);
941 assert(NewRC && "subreg chosen for remat incompatible with instruction");
942 MRI->setRegClass(DstReg, NewRC);
944 updateRegDefsUses(DstReg, DstReg, DstIdx);
945 NewMI->getOperand(0).setSubReg(NewIdx);
946 } else if (NewMI->getOperand(0).getReg() != CopyDstReg) {
947 // The New instruction may be defining a sub-register of what's actually
948 // been asked for. If so it must implicitly define the whole thing.
949 assert(TargetRegisterInfo::isPhysicalRegister(DstReg) &&
950 "Only expect virtual or physical registers in remat");
951 NewMI->getOperand(0).setIsDead(true);
952 NewMI->addOperand(MachineOperand::CreateReg(CopyDstReg,
956 // Record small dead def live-ranges for all the subregisters
957 // of the destination register.
958 // Otherwise, variables that live through may miss some
959 // interferences, thus creating invalid allocation.
961 // vreg1 = somedef ; vreg1 GR8
962 // vreg2 = remat ; vreg2 GR32
963 // CL = COPY vreg2.sub_8bit
964 // = somedef vreg1 ; vreg1 GR8
966 // vreg1 = somedef ; vreg1 GR8
967 // ECX<def, dead> = remat ; CL<imp-def>
968 // = somedef vreg1 ; vreg1 GR8
969 // vreg1 will see the inteferences with CL but not with CH since
970 // no live-ranges would have been created for ECX.
972 SlotIndex NewMIIdx = LIS->getInstructionIndex(NewMI);
973 for (MCRegUnitIterator Units(NewMI->getOperand(0).getReg(), TRI);
974 Units.isValid(); ++Units)
975 if (LiveRange *LR = LIS->getCachedRegUnit(*Units))
976 LR->createDeadDef(NewMIIdx.getRegSlot(), LIS->getVNInfoAllocator());
979 if (NewMI->getOperand(0).getSubReg())
980 NewMI->getOperand(0).setIsUndef();
982 // CopyMI may have implicit operands, transfer them over to the newly
983 // rematerialized instruction. And update implicit def interval valnos.
984 for (unsigned i = CopyMI->getDesc().getNumOperands(),
985 e = CopyMI->getNumOperands(); i != e; ++i) {
986 MachineOperand &MO = CopyMI->getOperand(i);
988 assert(MO.isImplicit() && "No explicit operands after implict operands.");
989 // Discard VReg implicit defs.
990 if (TargetRegisterInfo::isPhysicalRegister(MO.getReg())) {
991 NewMI->addOperand(MO);
996 SlotIndex NewMIIdx = LIS->getInstructionIndex(NewMI);
997 for (unsigned i = 0, e = NewMIImplDefs.size(); i != e; ++i) {
998 unsigned Reg = NewMIImplDefs[i];
999 for (MCRegUnitIterator Units(Reg, TRI); Units.isValid(); ++Units)
1000 if (LiveRange *LR = LIS->getCachedRegUnit(*Units))
1001 LR->createDeadDef(NewMIIdx.getRegSlot(), LIS->getVNInfoAllocator());
1004 DEBUG(dbgs() << "Remat: " << *NewMI);
1007 // The source interval can become smaller because we removed a use.
1008 LIS->shrinkToUses(&SrcInt, &DeadDefs);
1009 if (!DeadDefs.empty()) {
1010 // If the virtual SrcReg is completely eliminated, update all DBG_VALUEs
1011 // to describe DstReg instead.
1012 for (MachineOperand &UseMO : MRI->use_operands(SrcReg)) {
1013 MachineInstr *UseMI = UseMO.getParent();
1014 if (UseMI->isDebugValue()) {
1015 UseMO.setReg(DstReg);
1016 DEBUG(dbgs() << "\t\tupdated: " << *UseMI);
1019 eliminateDeadDefs();
1025 static void removeUndefValue(LiveRange &LR, SlotIndex At)
1027 VNInfo *VNInfo = LR.getVNInfoAt(At);
1028 assert(VNInfo != nullptr && SlotIndex::isSameInstr(VNInfo->def, At));
1029 LR.removeValNo(VNInfo);
1032 /// ProcessImpicitDefs may leave some copies of <undef>
1033 /// values, it only removes local variables. When we have a copy like:
1035 /// %vreg1 = COPY %vreg2<undef>
1037 /// We delete the copy and remove the corresponding value number from %vreg1.
1038 /// Any uses of that value number are marked as <undef>.
1039 bool RegisterCoalescer::eliminateUndefCopy(MachineInstr *CopyMI) {
1040 // Note that we do not query CoalescerPair here but redo isMoveInstr as the
1041 // CoalescerPair may have a new register class with adjusted subreg indices
1043 unsigned SrcReg, DstReg, SrcSubIdx, DstSubIdx;
1044 isMoveInstr(*TRI, CopyMI, SrcReg, DstReg, SrcSubIdx, DstSubIdx);
1046 SlotIndex Idx = LIS->getInstructionIndex(CopyMI);
1047 const LiveInterval &SrcLI = LIS->getInterval(SrcReg);
1048 // CopyMI is undef iff SrcReg is not live before the instruction.
1049 if (SrcSubIdx != 0 && SrcLI.hasSubRanges()) {
1050 unsigned SrcMask = TRI->getSubRegIndexLaneMask(SrcSubIdx);
1051 for (const LiveInterval::SubRange &SR : SrcLI.subranges()) {
1052 if ((SR.LaneMask & SrcMask) == 0)
1057 } else if (SrcLI.liveAt(Idx))
1060 DEBUG(dbgs() << "\tEliminating copy of <undef> value\n");
1062 // Remove any DstReg segments starting at the instruction.
1063 LiveInterval &DstLI = LIS->getInterval(DstReg);
1064 unsigned DstMask = TRI->getSubRegIndexLaneMask(DstSubIdx);
1065 SlotIndex RegIndex = Idx.getRegSlot();
1066 for (LiveInterval::SubRange &SR : DstLI.subranges()) {
1067 if ((SR.LaneMask & DstMask) == 0)
1069 removeUndefValue(SR, RegIndex);
1071 DstLI.removeEmptySubRanges();
1073 // Remove value or merge with previous one in case of a subregister def.
1074 if (VNInfo *PrevVNI = DstLI.getVNInfoAt(Idx)) {
1075 VNInfo *VNInfo = DstLI.getVNInfoAt(RegIndex);
1076 DstLI.MergeValueNumberInto(VNInfo, PrevVNI);
1078 removeUndefValue(DstLI, RegIndex);
1081 // Mark uses as undef.
1082 for (MachineOperand &MO : MRI->reg_nodbg_operands(DstReg)) {
1083 if (MO.isDef() /*|| MO.isUndef()*/)
1085 const MachineInstr &MI = *MO.getParent();
1086 SlotIndex UseIdx = LIS->getInstructionIndex(&MI);
1087 unsigned UseMask = TRI->getSubRegIndexLaneMask(MO.getSubReg());
1089 if (UseMask != ~0u && DstLI.hasSubRanges()) {
1091 for (const LiveInterval::SubRange &SR : DstLI.subranges()) {
1092 if ((SR.LaneMask & UseMask) == 0)
1094 if (SR.liveAt(UseIdx)) {
1100 isLive = DstLI.liveAt(UseIdx);
1103 MO.setIsUndef(true);
1104 DEBUG(dbgs() << "\tnew undef: " << UseIdx << '\t' << MI);
1109 /// Replace all defs and uses of SrcReg to DstReg and update the subregister
1110 /// number if it is not zero. If DstReg is a physical register and the existing
1111 /// subregister number of the def / use being updated is not zero, make sure to
1112 /// set it to the correct physical subregister.
1113 void RegisterCoalescer::updateRegDefsUses(unsigned SrcReg,
1116 bool DstIsPhys = TargetRegisterInfo::isPhysicalRegister(DstReg);
1117 LiveInterval *DstInt = DstIsPhys ? nullptr : &LIS->getInterval(DstReg);
1119 SmallPtrSet<MachineInstr*, 8> Visited;
1120 for (MachineRegisterInfo::reg_instr_iterator
1121 I = MRI->reg_instr_begin(SrcReg), E = MRI->reg_instr_end();
1123 MachineInstr *UseMI = &*(I++);
1125 // Each instruction can only be rewritten once because sub-register
1126 // composition is not always idempotent. When SrcReg != DstReg, rewriting
1127 // the UseMI operands removes them from the SrcReg use-def chain, but when
1128 // SrcReg is DstReg we could encounter UseMI twice if it has multiple
1129 // operands mentioning the virtual register.
1130 if (SrcReg == DstReg && !Visited.insert(UseMI).second)
1133 SmallVector<unsigned,8> Ops;
1135 std::tie(Reads, Writes) = UseMI->readsWritesVirtualRegister(SrcReg, &Ops);
1137 // If SrcReg wasn't read, it may still be the case that DstReg is live-in
1138 // because SrcReg is a sub-register.
1139 if (DstInt && !Reads && SubIdx)
1140 Reads = DstInt->liveAt(LIS->getInstructionIndex(UseMI));
1142 // Replace SrcReg with DstReg in all UseMI operands.
1143 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1144 MachineOperand &MO = UseMI->getOperand(Ops[i]);
1146 // Adjust <undef> flags in case of sub-register joins. We don't want to
1147 // turn a full def into a read-modify-write sub-register def and vice
1149 if (SubIdx && MO.isDef())
1150 MO.setIsUndef(!Reads);
1152 // A subreg use of a partially undef (super) register may be a complete
1153 // undef use now and then has to be marked that way.
1154 if (SubIdx != 0 && MO.isUse() && MRI->tracksSubRegLiveness()) {
1155 if (!DstInt->hasSubRanges()) {
1156 BumpPtrAllocator &Allocator = LIS->getVNInfoAllocator();
1157 unsigned Mask = MRI->getMaxLaneMaskForVReg(DstInt->reg);
1158 DstInt->createSubRangeFrom(Allocator, Mask, *DstInt);
1160 unsigned Mask = TRI->getSubRegIndexLaneMask(SubIdx);
1161 bool IsUndef = true;
1162 SlotIndex MIIdx = UseMI->isDebugValue()
1163 ? LIS->getSlotIndexes()->getIndexBefore(UseMI)
1164 : LIS->getInstructionIndex(UseMI);
1165 SlotIndex UseIdx = MIIdx.getRegSlot(true);
1166 for (LiveInterval::SubRange &S : DstInt->subranges()) {
1167 if ((S.LaneMask & Mask) == 0)
1169 if (S.liveAt(UseIdx)) {
1175 MO.setIsUndef(true);
1176 // We found out some subregister use is actually reading an undefined
1177 // value. In some cases the whole vreg has become undefined at this
1178 // point so we have to potentially shrink the main range if the
1179 // use was ending a live segment there.
1180 LiveQueryResult Q = DstInt->Query(MIIdx);
1181 if (Q.valueOut() == nullptr)
1182 ShrinkMainRange = true;
1187 MO.substPhysReg(DstReg, *TRI);
1189 MO.substVirtReg(DstReg, SubIdx, *TRI);
1193 dbgs() << "\t\tupdated: ";
1194 if (!UseMI->isDebugValue())
1195 dbgs() << LIS->getInstructionIndex(UseMI) << "\t";
1201 /// Return true if a copy involving a physreg should be joined.
1202 bool RegisterCoalescer::canJoinPhys(const CoalescerPair &CP) {
1203 /// Always join simple intervals that are defined by a single copy from a
1204 /// reserved register. This doesn't increase register pressure, so it is
1205 /// always beneficial.
1206 if (!MRI->isReserved(CP.getDstReg())) {
1207 DEBUG(dbgs() << "\tCan only merge into reserved registers.\n");
1211 LiveInterval &JoinVInt = LIS->getInterval(CP.getSrcReg());
1212 if (CP.isFlipped() && JoinVInt.containsOneValue())
1215 DEBUG(dbgs() << "\tCannot join defs into reserved register.\n");
1219 /// Attempt to join intervals corresponding to SrcReg/DstReg,
1220 /// which are the src/dst of the copy instruction CopyMI. This returns true
1221 /// if the copy was successfully coalesced away. If it is not currently
1222 /// possible to coalesce this interval, but it may be possible if other
1223 /// things get coalesced, then it returns true by reference in 'Again'.
1224 bool RegisterCoalescer::joinCopy(MachineInstr *CopyMI, bool &Again) {
1227 DEBUG(dbgs() << LIS->getInstructionIndex(CopyMI) << '\t' << *CopyMI);
1229 CoalescerPair CP(*TRI);
1230 if (!CP.setRegisters(CopyMI)) {
1231 DEBUG(dbgs() << "\tNot coalescable.\n");
1235 if (CP.getNewRC()) {
1236 auto SrcRC = MRI->getRegClass(CP.getSrcReg());
1237 auto DstRC = MRI->getRegClass(CP.getDstReg());
1238 unsigned SrcIdx = CP.getSrcIdx();
1239 unsigned DstIdx = CP.getDstIdx();
1240 if (CP.isFlipped()) {
1241 std::swap(SrcIdx, DstIdx);
1242 std::swap(SrcRC, DstRC);
1244 if (!TRI->shouldCoalesce(CopyMI, SrcRC, SrcIdx, DstRC, DstIdx,
1246 DEBUG(dbgs() << "\tSubtarget bailed on coalescing.\n");
1251 // Dead code elimination. This really should be handled by MachineDCE, but
1252 // sometimes dead copies slip through, and we can't generate invalid live
1254 if (!CP.isPhys() && CopyMI->allDefsAreDead()) {
1255 DEBUG(dbgs() << "\tCopy is dead.\n");
1256 DeadDefs.push_back(CopyMI);
1257 eliminateDeadDefs();
1261 // Eliminate undefs.
1262 if (!CP.isPhys() && eliminateUndefCopy(CopyMI)) {
1263 LIS->RemoveMachineInstrFromMaps(CopyMI);
1264 CopyMI->eraseFromParent();
1265 return false; // Not coalescable.
1268 // Coalesced copies are normally removed immediately, but transformations
1269 // like removeCopyByCommutingDef() can inadvertently create identity copies.
1270 // When that happens, just join the values and remove the copy.
1271 if (CP.getSrcReg() == CP.getDstReg()) {
1272 LiveInterval &LI = LIS->getInterval(CP.getSrcReg());
1273 DEBUG(dbgs() << "\tCopy already coalesced: " << LI << '\n');
1274 const SlotIndex CopyIdx = LIS->getInstructionIndex(CopyMI);
1275 LiveQueryResult LRQ = LI.Query(CopyIdx);
1276 if (VNInfo *DefVNI = LRQ.valueDefined()) {
1277 VNInfo *ReadVNI = LRQ.valueIn();
1278 assert(ReadVNI && "No value before copy and no <undef> flag.");
1279 assert(ReadVNI != DefVNI && "Cannot read and define the same value.");
1280 LI.MergeValueNumberInto(DefVNI, ReadVNI);
1282 // Process subregister liveranges.
1283 for (LiveInterval::SubRange &S : LI.subranges()) {
1284 LiveQueryResult SLRQ = S.Query(CopyIdx);
1285 if (VNInfo *SDefVNI = SLRQ.valueDefined()) {
1286 VNInfo *SReadVNI = SLRQ.valueIn();
1287 S.MergeValueNumberInto(SDefVNI, SReadVNI);
1290 DEBUG(dbgs() << "\tMerged values: " << LI << '\n');
1292 LIS->RemoveMachineInstrFromMaps(CopyMI);
1293 CopyMI->eraseFromParent();
1297 // Enforce policies.
1299 DEBUG(dbgs() << "\tConsidering merging " << PrintReg(CP.getSrcReg(), TRI)
1300 << " with " << PrintReg(CP.getDstReg(), TRI, CP.getSrcIdx())
1302 if (!canJoinPhys(CP)) {
1303 // Before giving up coalescing, if definition of source is defined by
1304 // trivial computation, try rematerializing it.
1306 if (reMaterializeTrivialDef(CP, CopyMI, IsDefCopy))
1309 Again = true; // May be possible to coalesce later.
1313 // When possible, let DstReg be the larger interval.
1314 if (!CP.isPartial() && LIS->getInterval(CP.getSrcReg()).size() >
1315 LIS->getInterval(CP.getDstReg()).size())
1319 dbgs() << "\tConsidering merging to "
1320 << TRI->getRegClassName(CP.getNewRC()) << " with ";
1321 if (CP.getDstIdx() && CP.getSrcIdx())
1322 dbgs() << PrintReg(CP.getDstReg()) << " in "
1323 << TRI->getSubRegIndexName(CP.getDstIdx()) << " and "
1324 << PrintReg(CP.getSrcReg()) << " in "
1325 << TRI->getSubRegIndexName(CP.getSrcIdx()) << '\n';
1327 dbgs() << PrintReg(CP.getSrcReg(), TRI) << " in "
1328 << PrintReg(CP.getDstReg(), TRI, CP.getSrcIdx()) << '\n';
1333 ShrinkMainRange = false;
1335 // Okay, attempt to join these two intervals. On failure, this returns false.
1336 // Otherwise, if one of the intervals being joined is a physreg, this method
1337 // always canonicalizes DstInt to be it. The output "SrcInt" will not have
1338 // been modified, so we can use this information below to update aliases.
1339 if (!joinIntervals(CP)) {
1340 // Coalescing failed.
1342 // If definition of source is defined by trivial computation, try
1343 // rematerializing it.
1345 if (reMaterializeTrivialDef(CP, CopyMI, IsDefCopy))
1348 // If we can eliminate the copy without merging the live segments, do so
1350 if (!CP.isPartial() && !CP.isPhys()) {
1351 if (adjustCopiesBackFrom(CP, CopyMI) ||
1352 removeCopyByCommutingDef(CP, CopyMI)) {
1353 LIS->RemoveMachineInstrFromMaps(CopyMI);
1354 CopyMI->eraseFromParent();
1355 DEBUG(dbgs() << "\tTrivial!\n");
1360 // Otherwise, we are unable to join the intervals.
1361 DEBUG(dbgs() << "\tInterference!\n");
1362 Again = true; // May be possible to coalesce later.
1366 // Coalescing to a virtual register that is of a sub-register class of the
1367 // other. Make sure the resulting register is set to the right register class.
1368 if (CP.isCrossClass()) {
1370 MRI->setRegClass(CP.getDstReg(), CP.getNewRC());
1373 // Removing sub-register copies can ease the register class constraints.
1374 // Make sure we attempt to inflate the register class of DstReg.
1375 if (!CP.isPhys() && RegClassInfo.isProperSubClass(CP.getNewRC()))
1376 InflateRegs.push_back(CP.getDstReg());
1378 // CopyMI has been erased by joinIntervals at this point. Remove it from
1379 // ErasedInstrs since copyCoalesceWorkList() won't add a successful join back
1380 // to the work list. This keeps ErasedInstrs from growing needlessly.
1381 ErasedInstrs.erase(CopyMI);
1383 // Rewrite all SrcReg operands to DstReg.
1384 // Also update DstReg operands to include DstIdx if it is set.
1386 updateRegDefsUses(CP.getDstReg(), CP.getDstReg(), CP.getDstIdx());
1387 updateRegDefsUses(CP.getSrcReg(), CP.getDstReg(), CP.getSrcIdx());
1389 // Shrink subregister ranges if necessary.
1390 if (ShrinkMask != 0) {
1391 LiveInterval &LI = LIS->getInterval(CP.getDstReg());
1392 for (LiveInterval::SubRange &S : LI.subranges()) {
1393 if ((S.LaneMask & ShrinkMask) == 0)
1395 DEBUG(dbgs() << "Shrink LaneUses (Lane "
1396 << format("%04X", S.LaneMask) << ")\n");
1397 LIS->shrinkToUses(S, LI.reg);
1400 if (ShrinkMainRange) {
1401 LiveInterval &LI = LIS->getInterval(CP.getDstReg());
1402 LIS->shrinkToUses(&LI);
1405 // SrcReg is guaranteed to be the register whose live interval that is
1407 LIS->removeInterval(CP.getSrcReg());
1409 // Update regalloc hint.
1410 TRI->UpdateRegAllocHint(CP.getSrcReg(), CP.getDstReg(), *MF);
1413 dbgs() << "\tSuccess: " << PrintReg(CP.getSrcReg(), TRI, CP.getSrcIdx())
1414 << " -> " << PrintReg(CP.getDstReg(), TRI, CP.getDstIdx()) << '\n';
1415 dbgs() << "\tResult = ";
1417 dbgs() << PrintReg(CP.getDstReg(), TRI);
1419 dbgs() << LIS->getInterval(CP.getDstReg());
1427 /// Attempt joining with a reserved physreg.
1428 bool RegisterCoalescer::joinReservedPhysReg(CoalescerPair &CP) {
1429 assert(CP.isPhys() && "Must be a physreg copy");
1430 assert(MRI->isReserved(CP.getDstReg()) && "Not a reserved register");
1431 LiveInterval &RHS = LIS->getInterval(CP.getSrcReg());
1432 DEBUG(dbgs() << "\t\tRHS = " << RHS << '\n');
1434 assert(CP.isFlipped() && RHS.containsOneValue() &&
1435 "Invalid join with reserved register");
1437 // Optimization for reserved registers like ESP. We can only merge with a
1438 // reserved physreg if RHS has a single value that is a copy of CP.DstReg().
1439 // The live range of the reserved register will look like a set of dead defs
1440 // - we don't properly track the live range of reserved registers.
1442 // Deny any overlapping intervals. This depends on all the reserved
1443 // register live ranges to look like dead defs.
1444 for (MCRegUnitIterator UI(CP.getDstReg(), TRI); UI.isValid(); ++UI)
1445 if (RHS.overlaps(LIS->getRegUnit(*UI))) {
1446 DEBUG(dbgs() << "\t\tInterference: " << PrintRegUnit(*UI, TRI) << '\n');
1450 // Skip any value computations, we are not adding new values to the
1451 // reserved register. Also skip merging the live ranges, the reserved
1452 // register live range doesn't need to be accurate as long as all the
1455 // Delete the identity copy.
1456 MachineInstr *CopyMI = MRI->getVRegDef(RHS.reg);
1457 LIS->RemoveMachineInstrFromMaps(CopyMI);
1458 CopyMI->eraseFromParent();
1460 // We don't track kills for reserved registers.
1461 MRI->clearKillFlags(CP.getSrcReg());
1466 //===----------------------------------------------------------------------===//
1467 // Interference checking and interval joining
1468 //===----------------------------------------------------------------------===//
1470 // In the easiest case, the two live ranges being joined are disjoint, and
1471 // there is no interference to consider. It is quite common, though, to have
1472 // overlapping live ranges, and we need to check if the interference can be
1475 // The live range of a single SSA value forms a sub-tree of the dominator tree.
1476 // This means that two SSA values overlap if and only if the def of one value
1477 // is contained in the live range of the other value. As a special case, the
1478 // overlapping values can be defined at the same index.
1480 // The interference from an overlapping def can be resolved in these cases:
1482 // 1. Coalescable copies. The value is defined by a copy that would become an
1483 // identity copy after joining SrcReg and DstReg. The copy instruction will
1484 // be removed, and the value will be merged with the source value.
1486 // There can be several copies back and forth, causing many values to be
1487 // merged into one. We compute a list of ultimate values in the joined live
1488 // range as well as a mappings from the old value numbers.
1490 // 2. IMPLICIT_DEF. This instruction is only inserted to ensure all PHI
1491 // predecessors have a live out value. It doesn't cause real interference,
1492 // and can be merged into the value it overlaps. Like a coalescable copy, it
1493 // can be erased after joining.
1495 // 3. Copy of external value. The overlapping def may be a copy of a value that
1496 // is already in the other register. This is like a coalescable copy, but
1497 // the live range of the source register must be trimmed after erasing the
1498 // copy instruction:
1501 // %dst = COPY %ext <-- Remove this COPY, trim the live range of %ext.
1503 // 4. Clobbering undefined lanes. Vector registers are sometimes built by
1504 // defining one lane at a time:
1506 // %dst:ssub0<def,read-undef> = FOO
1508 // %dst:ssub1<def> = COPY %src
1510 // The live range of %src overlaps the %dst value defined by FOO, but
1511 // merging %src into %dst:ssub1 is only going to clobber the ssub1 lane
1512 // which was undef anyway.
1514 // The value mapping is more complicated in this case. The final live range
1515 // will have different value numbers for both FOO and BAR, but there is no
1516 // simple mapping from old to new values. It may even be necessary to add
1519 // 5. Clobbering dead lanes. A def may clobber a lane of a vector register that
1520 // is live, but never read. This can happen because we don't compute
1521 // individual live ranges per lane.
1525 // %dst:ssub1<def> = COPY %src
1527 // This kind of interference is only resolved locally. If the clobbered
1528 // lane value escapes the block, the join is aborted.
1531 /// Track information about values in a single virtual register about to be
1532 /// joined. Objects of this class are always created in pairs - one for each
1533 /// side of the CoalescerPair (or one for each lane of a side of the coalescer
1536 /// Live range we work on.
1538 /// (Main) register we work on.
1541 // Reg (and therefore the values in this liverange) will end up as subregister
1542 // SubIdx in the coalesced register. Either CP.DstIdx or CP.SrcIdx.
1543 const unsigned SubIdx;
1544 // The LaneMask that this liverange will occupy the coalesced register. May be
1545 // smaller than the lanemask produced by SubIdx when merging subranges.
1546 const unsigned LaneMask;
1548 /// This is true when joining sub register ranges, false when joining main
1550 const bool SubRangeJoin;
1551 /// Whether the current LiveInterval tracks subregister liveness.
1552 const bool TrackSubRegLiveness;
1554 // Values that will be present in the final live range.
1555 SmallVectorImpl<VNInfo*> &NewVNInfo;
1557 const CoalescerPair &CP;
1559 SlotIndexes *Indexes;
1560 const TargetRegisterInfo *TRI;
1562 // Value number assignments. Maps value numbers in LI to entries in NewVNInfo.
1563 // This is suitable for passing to LiveInterval::join().
1564 SmallVector<int, 8> Assignments;
1566 // Conflict resolution for overlapping values.
1567 enum ConflictResolution {
1568 // No overlap, simply keep this value.
1571 // Merge this value into OtherVNI and erase the defining instruction.
1572 // Used for IMPLICIT_DEF, coalescable copies, and copies from external
1576 // Merge this value into OtherVNI but keep the defining instruction.
1577 // This is for the special case where OtherVNI is defined by the same
1581 // Keep this value, and have it replace OtherVNI where possible. This
1582 // complicates value mapping since OtherVNI maps to two different values
1583 // before and after this def.
1584 // Used when clobbering undefined or dead lanes.
1587 // Unresolved conflict. Visit later when all values have been mapped.
1590 // Unresolvable conflict. Abort the join.
1594 // Per-value info for LI. The lane bit masks are all relative to the final
1595 // joined register, so they can be compared directly between SrcReg and
1598 ConflictResolution Resolution;
1600 // Lanes written by this def, 0 for unanalyzed values.
1601 unsigned WriteLanes;
1603 // Lanes with defined values in this register. Other lanes are undef and
1605 unsigned ValidLanes;
1607 // Value in LI being redefined by this def.
1610 // Value in the other live range that overlaps this def, if any.
1613 // Is this value an IMPLICIT_DEF that can be erased?
1615 // IMPLICIT_DEF values should only exist at the end of a basic block that
1616 // is a predecessor to a phi-value. These IMPLICIT_DEF instructions can be
1617 // safely erased if they are overlapping a live value in the other live
1620 // Weird control flow graphs and incomplete PHI handling in
1621 // ProcessImplicitDefs can very rarely create IMPLICIT_DEF values with
1622 // longer live ranges. Such IMPLICIT_DEF values should be treated like
1624 bool ErasableImplicitDef;
1626 // True when the live range of this value will be pruned because of an
1627 // overlapping CR_Replace value in the other live range.
1630 // True once Pruned above has been computed.
1631 bool PrunedComputed;
1633 Val() : Resolution(CR_Keep), WriteLanes(0), ValidLanes(0),
1634 RedefVNI(nullptr), OtherVNI(nullptr), ErasableImplicitDef(false),
1635 Pruned(false), PrunedComputed(false) {}
1637 bool isAnalyzed() const { return WriteLanes != 0; }
1640 // One entry per value number in LI.
1641 SmallVector<Val, 8> Vals;
1643 unsigned computeWriteLanes(const MachineInstr *DefMI, bool &Redef) const;
1644 std::pair<const VNInfo*,unsigned> followCopyChain(const VNInfo *VNI) const;
1645 bool valuesIdentical(VNInfo *Val0, VNInfo *Val1, const JoinVals &Other) const;
1646 ConflictResolution analyzeValue(unsigned ValNo, JoinVals &Other);
1647 void computeAssignment(unsigned ValNo, JoinVals &Other);
1648 bool taintExtent(unsigned, unsigned, JoinVals&,
1649 SmallVectorImpl<std::pair<SlotIndex, unsigned> >&);
1650 bool usesLanes(const MachineInstr *MI, unsigned, unsigned, unsigned) const;
1651 bool isPrunedValue(unsigned ValNo, JoinVals &Other);
1654 JoinVals(LiveRange &LR, unsigned Reg, unsigned SubIdx, unsigned LaneMask,
1655 SmallVectorImpl<VNInfo*> &newVNInfo, const CoalescerPair &cp,
1656 LiveIntervals *lis, const TargetRegisterInfo *TRI, bool SubRangeJoin,
1657 bool TrackSubRegLiveness)
1658 : LR(LR), Reg(Reg), SubIdx(SubIdx), LaneMask(LaneMask),
1659 SubRangeJoin(SubRangeJoin), TrackSubRegLiveness(TrackSubRegLiveness),
1660 NewVNInfo(newVNInfo), CP(cp), LIS(lis), Indexes(LIS->getSlotIndexes()),
1661 TRI(TRI), Assignments(LR.getNumValNums(), -1), Vals(LR.getNumValNums())
1664 /// Analyze defs in LR and compute a value mapping in NewVNInfo.
1665 /// Returns false if any conflicts were impossible to resolve.
1666 bool mapValues(JoinVals &Other);
1668 /// Try to resolve conflicts that require all values to be mapped.
1669 /// Returns false if any conflicts were impossible to resolve.
1670 bool resolveConflicts(JoinVals &Other);
1672 /// Prune the live range of values in Other.LR where they would conflict with
1673 /// CR_Replace values in LR. Collect end points for restoring the live range
1675 void pruneValues(JoinVals &Other, SmallVectorImpl<SlotIndex> &EndPoints,
1678 // Removes subranges starting at copies that get removed. This sometimes
1679 // happens when undefined subranges are copied around. These ranges contain
1680 // no usefull information and can be removed.
1681 void pruneSubRegValues(LiveInterval &LI, unsigned &ShrinkMask);
1683 /// Erase any machine instructions that have been coalesced away.
1684 /// Add erased instructions to ErasedInstrs.
1685 /// Add foreign virtual registers to ShrinkRegs if their live range ended at
1686 /// the erased instrs.
1687 void eraseInstrs(SmallPtrSetImpl<MachineInstr*> &ErasedInstrs,
1688 SmallVectorImpl<unsigned> &ShrinkRegs);
1690 /// Get the value assignments suitable for passing to LiveInterval::join.
1691 const int *getAssignments() const { return Assignments.data(); }
1693 } // end anonymous namespace
1695 /// Compute the bitmask of lanes actually written by DefMI.
1696 /// Set Redef if there are any partial register definitions that depend on the
1697 /// previous value of the register.
1698 unsigned JoinVals::computeWriteLanes(const MachineInstr *DefMI, bool &Redef)
1701 for (ConstMIOperands MO(DefMI); MO.isValid(); ++MO) {
1702 if (!MO->isReg() || MO->getReg() != Reg || !MO->isDef())
1704 L |= TRI->getSubRegIndexLaneMask(
1705 TRI->composeSubRegIndices(SubIdx, MO->getSubReg()));
1712 /// Find the ultimate value that VNI was copied from.
1713 std::pair<const VNInfo*, unsigned> JoinVals::followCopyChain(
1714 const VNInfo *VNI) const {
1715 unsigned Reg = this->Reg;
1717 while (!VNI->isPHIDef()) {
1718 SlotIndex Def = VNI->def;
1719 MachineInstr *MI = Indexes->getInstructionFromIndex(Def);
1720 assert(MI && "No defining instruction");
1721 if (!MI->isFullCopy())
1722 return std::make_pair(VNI, Reg);
1723 unsigned SrcReg = MI->getOperand(1).getReg();
1724 if (!TargetRegisterInfo::isVirtualRegister(SrcReg))
1725 return std::make_pair(VNI, Reg);
1727 const LiveInterval &LI = LIS->getInterval(SrcReg);
1728 const VNInfo *ValueIn;
1729 // No subrange involved.
1730 if (!SubRangeJoin || !LI.hasSubRanges()) {
1731 LiveQueryResult LRQ = LI.Query(Def);
1732 ValueIn = LRQ.valueIn();
1734 // Query subranges. Pick the first matching one.
1736 for (const LiveInterval::SubRange &S : LI.subranges()) {
1737 // Transform lanemask to a mask in the joined live interval.
1738 unsigned SMask = TRI->composeSubRegIndexLaneMask(SubIdx, S.LaneMask);
1739 if ((SMask & LaneMask) == 0)
1741 LiveQueryResult LRQ = S.Query(Def);
1742 ValueIn = LRQ.valueIn();
1746 if (ValueIn == nullptr)
1751 return std::make_pair(VNI, Reg);
1754 bool JoinVals::valuesIdentical(VNInfo *Value0, VNInfo *Value1,
1755 const JoinVals &Other) const {
1756 const VNInfo *Orig0;
1758 std::tie(Orig0, Reg0) = followCopyChain(Value0);
1759 if (Orig0 == Value1)
1762 const VNInfo *Orig1;
1764 std::tie(Orig1, Reg1) = Other.followCopyChain(Value1);
1766 // The values are equal if they are defined at the same place and use the
1767 // same register. Note that we cannot compare VNInfos directly as some of
1768 // them might be from a copy created in mergeSubRangeInto() while the other
1769 // is from the original LiveInterval.
1770 return Orig0->def == Orig1->def && Reg0 == Reg1;
1773 /// Analyze ValNo in this live range, and set all fields of Vals[ValNo].
1774 /// Return a conflict resolution when possible, but leave the hard cases as
1776 /// Recursively calls computeAssignment() on this and Other, guaranteeing that
1777 /// both OtherVNI and RedefVNI have been analyzed and mapped before returning.
1778 /// The recursion always goes upwards in the dominator tree, making loops
1780 JoinVals::ConflictResolution
1781 JoinVals::analyzeValue(unsigned ValNo, JoinVals &Other) {
1782 Val &V = Vals[ValNo];
1783 assert(!V.isAnalyzed() && "Value has already been analyzed!");
1784 VNInfo *VNI = LR.getValNumInfo(ValNo);
1785 if (VNI->isUnused()) {
1790 // Get the instruction defining this value, compute the lanes written.
1791 const MachineInstr *DefMI = nullptr;
1792 if (VNI->isPHIDef()) {
1793 // Conservatively assume that all lanes in a PHI are valid.
1794 unsigned Lanes = SubRangeJoin ? 1 : TRI->getSubRegIndexLaneMask(SubIdx);
1795 V.ValidLanes = V.WriteLanes = Lanes;
1797 DefMI = Indexes->getInstructionFromIndex(VNI->def);
1798 assert(DefMI != nullptr);
1800 // We don't care about the lanes when joining subregister ranges.
1801 V.ValidLanes = V.WriteLanes = 1;
1804 V.ValidLanes = V.WriteLanes = computeWriteLanes(DefMI, Redef);
1806 // If this is a read-modify-write instruction, there may be more valid
1807 // lanes than the ones written by this instruction.
1808 // This only covers partial redef operands. DefMI may have normal use
1809 // operands reading the register. They don't contribute valid lanes.
1811 // This adds ssub1 to the set of valid lanes in %src:
1813 // %src:ssub1<def> = FOO
1815 // This leaves only ssub1 valid, making any other lanes undef:
1817 // %src:ssub1<def,read-undef> = FOO %src:ssub2
1819 // The <read-undef> flag on the def operand means that old lane values are
1822 V.RedefVNI = LR.Query(VNI->def).valueIn();
1823 assert((TrackSubRegLiveness || V.RedefVNI) &&
1824 "Instruction is reading nonexistent value");
1825 if (V.RedefVNI != nullptr) {
1826 computeAssignment(V.RedefVNI->id, Other);
1827 V.ValidLanes |= Vals[V.RedefVNI->id].ValidLanes;
1831 // An IMPLICIT_DEF writes undef values.
1832 if (DefMI->isImplicitDef()) {
1833 // We normally expect IMPLICIT_DEF values to be live only until the end
1834 // of their block. If the value is really live longer and gets pruned in
1835 // another block, this flag is cleared again.
1836 V.ErasableImplicitDef = true;
1837 V.ValidLanes &= ~V.WriteLanes;
1842 // Find the value in Other that overlaps VNI->def, if any.
1843 LiveQueryResult OtherLRQ = Other.LR.Query(VNI->def);
1845 // It is possible that both values are defined by the same instruction, or
1846 // the values are PHIs defined in the same block. When that happens, the two
1847 // values should be merged into one, but not into any preceding value.
1848 // The first value defined or visited gets CR_Keep, the other gets CR_Merge.
1849 if (VNInfo *OtherVNI = OtherLRQ.valueDefined()) {
1850 assert(SlotIndex::isSameInstr(VNI->def, OtherVNI->def) && "Broken LRQ");
1852 // One value stays, the other is merged. Keep the earlier one, or the first
1854 if (OtherVNI->def < VNI->def)
1855 Other.computeAssignment(OtherVNI->id, *this);
1856 else if (VNI->def < OtherVNI->def && OtherLRQ.valueIn()) {
1857 // This is an early-clobber def overlapping a live-in value in the other
1858 // register. Not mergeable.
1859 V.OtherVNI = OtherLRQ.valueIn();
1860 return CR_Impossible;
1862 V.OtherVNI = OtherVNI;
1863 Val &OtherV = Other.Vals[OtherVNI->id];
1864 // Keep this value, check for conflicts when analyzing OtherVNI.
1865 if (!OtherV.isAnalyzed())
1867 // Both sides have been analyzed now.
1868 // Allow overlapping PHI values. Any real interference would show up in a
1869 // predecessor, the PHI itself can't introduce any conflicts.
1870 if (VNI->isPHIDef())
1872 if (V.ValidLanes & OtherV.ValidLanes)
1873 // Overlapping lanes can't be resolved.
1874 return CR_Impossible;
1879 // No simultaneous def. Is Other live at the def?
1880 V.OtherVNI = OtherLRQ.valueIn();
1882 // No overlap, no conflict.
1885 assert(!SlotIndex::isSameInstr(VNI->def, V.OtherVNI->def) && "Broken LRQ");
1887 // We have overlapping values, or possibly a kill of Other.
1888 // Recursively compute assignments up the dominator tree.
1889 Other.computeAssignment(V.OtherVNI->id, *this);
1890 Val &OtherV = Other.Vals[V.OtherVNI->id];
1892 // Check if OtherV is an IMPLICIT_DEF that extends beyond its basic block.
1893 // This shouldn't normally happen, but ProcessImplicitDefs can leave such
1894 // IMPLICIT_DEF instructions behind, and there is nothing wrong with it
1897 // WHen it happens, treat that IMPLICIT_DEF as a normal value, and don't try
1898 // to erase the IMPLICIT_DEF instruction.
1899 if (OtherV.ErasableImplicitDef && DefMI &&
1900 DefMI->getParent() != Indexes->getMBBFromIndex(V.OtherVNI->def)) {
1901 DEBUG(dbgs() << "IMPLICIT_DEF defined at " << V.OtherVNI->def
1902 << " extends into BB#" << DefMI->getParent()->getNumber()
1903 << ", keeping it.\n");
1904 OtherV.ErasableImplicitDef = false;
1907 // Allow overlapping PHI values. Any real interference would show up in a
1908 // predecessor, the PHI itself can't introduce any conflicts.
1909 if (VNI->isPHIDef())
1912 // Check for simple erasable conflicts.
1913 if (DefMI->isImplicitDef()) {
1914 // We need the def for the subregister if there is nothing else live at the
1915 // subrange at this point.
1916 if (TrackSubRegLiveness
1917 && (V.WriteLanes & (OtherV.ValidLanes | OtherV.WriteLanes)) == 0)
1922 // Include the non-conflict where DefMI is a coalescable copy that kills
1923 // OtherVNI. We still want the copy erased and value numbers merged.
1924 if (CP.isCoalescable(DefMI)) {
1925 // Some of the lanes copied from OtherVNI may be undef, making them undef
1927 V.ValidLanes &= ~V.WriteLanes | OtherV.ValidLanes;
1931 // This may not be a real conflict if DefMI simply kills Other and defines
1933 if (OtherLRQ.isKill() && OtherLRQ.endPoint() <= VNI->def)
1936 // Handle the case where VNI and OtherVNI can be proven to be identical:
1938 // %other = COPY %ext
1939 // %this = COPY %ext <-- Erase this copy
1941 if (DefMI->isFullCopy() && !CP.isPartial()
1942 && valuesIdentical(VNI, V.OtherVNI, Other))
1945 // If the lanes written by this instruction were all undef in OtherVNI, it is
1946 // still safe to join the live ranges. This can't be done with a simple value
1947 // mapping, though - OtherVNI will map to multiple values:
1949 // 1 %dst:ssub0 = FOO <-- OtherVNI
1950 // 2 %src = BAR <-- VNI
1951 // 3 %dst:ssub1 = COPY %src<kill> <-- Eliminate this copy.
1953 // 5 QUUX %src<kill>
1955 // Here OtherVNI will map to itself in [1;2), but to VNI in [2;5). CR_Replace
1956 // handles this complex value mapping.
1957 if ((V.WriteLanes & OtherV.ValidLanes) == 0)
1960 // If the other live range is killed by DefMI and the live ranges are still
1961 // overlapping, it must be because we're looking at an early clobber def:
1963 // %dst<def,early-clobber> = ASM %src<kill>
1965 // In this case, it is illegal to merge the two live ranges since the early
1966 // clobber def would clobber %src before it was read.
1967 if (OtherLRQ.isKill()) {
1968 // This case where the def doesn't overlap the kill is handled above.
1969 assert(VNI->def.isEarlyClobber() &&
1970 "Only early clobber defs can overlap a kill");
1971 return CR_Impossible;
1974 // VNI is clobbering live lanes in OtherVNI, but there is still the
1975 // possibility that no instructions actually read the clobbered lanes.
1976 // If we're clobbering all the lanes in OtherVNI, at least one must be read.
1977 // Otherwise Other.RI wouldn't be live here.
1978 if ((TRI->getSubRegIndexLaneMask(Other.SubIdx) & ~V.WriteLanes) == 0)
1979 return CR_Impossible;
1981 // We need to verify that no instructions are reading the clobbered lanes. To
1982 // save compile time, we'll only check that locally. Don't allow the tainted
1983 // value to escape the basic block.
1984 MachineBasicBlock *MBB = Indexes->getMBBFromIndex(VNI->def);
1985 if (OtherLRQ.endPoint() >= Indexes->getMBBEndIdx(MBB))
1986 return CR_Impossible;
1988 // There are still some things that could go wrong besides clobbered lanes
1989 // being read, for example OtherVNI may be only partially redefined in MBB,
1990 // and some clobbered lanes could escape the block. Save this analysis for
1991 // resolveConflicts() when all values have been mapped. We need to know
1992 // RedefVNI and WriteLanes for any later defs in MBB, and we can't compute
1993 // that now - the recursive analyzeValue() calls must go upwards in the
1995 return CR_Unresolved;
1998 /// Compute the value assignment for ValNo in RI.
1999 /// This may be called recursively by analyzeValue(), but never for a ValNo on
2001 void JoinVals::computeAssignment(unsigned ValNo, JoinVals &Other) {
2002 Val &V = Vals[ValNo];
2003 if (V.isAnalyzed()) {
2004 // Recursion should always move up the dominator tree, so ValNo is not
2005 // supposed to reappear before it has been assigned.
2006 assert(Assignments[ValNo] != -1 && "Bad recursion?");
2009 switch ((V.Resolution = analyzeValue(ValNo, Other))) {
2012 // Merge this ValNo into OtherVNI.
2013 assert(V.OtherVNI && "OtherVNI not assigned, can't merge.");
2014 assert(Other.Vals[V.OtherVNI->id].isAnalyzed() && "Missing recursion");
2015 Assignments[ValNo] = Other.Assignments[V.OtherVNI->id];
2016 DEBUG(dbgs() << "\t\tmerge " << PrintReg(Reg) << ':' << ValNo << '@'
2017 << LR.getValNumInfo(ValNo)->def << " into "
2018 << PrintReg(Other.Reg) << ':' << V.OtherVNI->id << '@'
2019 << V.OtherVNI->def << " --> @"
2020 << NewVNInfo[Assignments[ValNo]]->def << '\n');
2023 case CR_Unresolved: {
2024 // The other value is going to be pruned if this join is successful.
2025 assert(V.OtherVNI && "OtherVNI not assigned, can't prune");
2026 Val &OtherV = Other.Vals[V.OtherVNI->id];
2027 // We cannot erase an IMPLICIT_DEF if we don't have valid values for all
2029 if ((OtherV.WriteLanes & ~V.ValidLanes) != 0 && TrackSubRegLiveness)
2030 OtherV.ErasableImplicitDef = false;
2031 OtherV.Pruned = true;
2035 // This value number needs to go in the final joined live range.
2036 Assignments[ValNo] = NewVNInfo.size();
2037 NewVNInfo.push_back(LR.getValNumInfo(ValNo));
2042 bool JoinVals::mapValues(JoinVals &Other) {
2043 for (unsigned i = 0, e = LR.getNumValNums(); i != e; ++i) {
2044 computeAssignment(i, Other);
2045 if (Vals[i].Resolution == CR_Impossible) {
2046 DEBUG(dbgs() << "\t\tinterference at " << PrintReg(Reg) << ':' << i
2047 << '@' << LR.getValNumInfo(i)->def << '\n');
2054 /// Assuming ValNo is going to clobber some valid lanes in Other.LR, compute
2055 /// the extent of the tainted lanes in the block.
2057 /// Multiple values in Other.LR can be affected since partial redefinitions can
2058 /// preserve previously tainted lanes.
2060 /// 1 %dst = VLOAD <-- Define all lanes in %dst
2061 /// 2 %src = FOO <-- ValNo to be joined with %dst:ssub0
2062 /// 3 %dst:ssub1 = BAR <-- Partial redef doesn't clear taint in ssub0
2063 /// 4 %dst:ssub0 = COPY %src <-- Conflict resolved, ssub0 wasn't read
2065 /// For each ValNo in Other that is affected, add an (EndIndex, TaintedLanes)
2066 /// entry to TaintedVals.
2068 /// Returns false if the tainted lanes extend beyond the basic block.
2070 taintExtent(unsigned ValNo, unsigned TaintedLanes, JoinVals &Other,
2071 SmallVectorImpl<std::pair<SlotIndex, unsigned> > &TaintExtent) {
2072 VNInfo *VNI = LR.getValNumInfo(ValNo);
2073 MachineBasicBlock *MBB = Indexes->getMBBFromIndex(VNI->def);
2074 SlotIndex MBBEnd = Indexes->getMBBEndIdx(MBB);
2076 // Scan Other.LR from VNI.def to MBBEnd.
2077 LiveInterval::iterator OtherI = Other.LR.find(VNI->def);
2078 assert(OtherI != Other.LR.end() && "No conflict?");
2080 // OtherI is pointing to a tainted value. Abort the join if the tainted
2081 // lanes escape the block.
2082 SlotIndex End = OtherI->end;
2083 if (End >= MBBEnd) {
2084 DEBUG(dbgs() << "\t\ttaints global " << PrintReg(Other.Reg) << ':'
2085 << OtherI->valno->id << '@' << OtherI->start << '\n');
2088 DEBUG(dbgs() << "\t\ttaints local " << PrintReg(Other.Reg) << ':'
2089 << OtherI->valno->id << '@' << OtherI->start
2090 << " to " << End << '\n');
2091 // A dead def is not a problem.
2094 TaintExtent.push_back(std::make_pair(End, TaintedLanes));
2096 // Check for another def in the MBB.
2097 if (++OtherI == Other.LR.end() || OtherI->start >= MBBEnd)
2100 // Lanes written by the new def are no longer tainted.
2101 const Val &OV = Other.Vals[OtherI->valno->id];
2102 TaintedLanes &= ~OV.WriteLanes;
2105 } while (TaintedLanes);
2109 /// Return true if MI uses any of the given Lanes from Reg.
2110 /// This does not include partial redefinitions of Reg.
2111 bool JoinVals::usesLanes(const MachineInstr *MI, unsigned Reg, unsigned SubIdx,
2112 unsigned Lanes) const {
2113 if (MI->isDebugValue())
2115 for (ConstMIOperands MO(MI); MO.isValid(); ++MO) {
2116 if (!MO->isReg() || MO->isDef() || MO->getReg() != Reg)
2118 if (!MO->readsReg())
2120 if (Lanes & TRI->getSubRegIndexLaneMask(
2121 TRI->composeSubRegIndices(SubIdx, MO->getSubReg())))
2127 bool JoinVals::resolveConflicts(JoinVals &Other) {
2128 for (unsigned i = 0, e = LR.getNumValNums(); i != e; ++i) {
2130 assert (V.Resolution != CR_Impossible && "Unresolvable conflict");
2131 if (V.Resolution != CR_Unresolved)
2133 DEBUG(dbgs() << "\t\tconflict at " << PrintReg(Reg) << ':' << i
2134 << '@' << LR.getValNumInfo(i)->def << '\n');
2139 assert(V.OtherVNI && "Inconsistent conflict resolution.");
2140 VNInfo *VNI = LR.getValNumInfo(i);
2141 const Val &OtherV = Other.Vals[V.OtherVNI->id];
2143 // VNI is known to clobber some lanes in OtherVNI. If we go ahead with the
2144 // join, those lanes will be tainted with a wrong value. Get the extent of
2145 // the tainted lanes.
2146 unsigned TaintedLanes = V.WriteLanes & OtherV.ValidLanes;
2147 SmallVector<std::pair<SlotIndex, unsigned>, 8> TaintExtent;
2148 if (!taintExtent(i, TaintedLanes, Other, TaintExtent))
2149 // Tainted lanes would extend beyond the basic block.
2152 assert(!TaintExtent.empty() && "There should be at least one conflict.");
2154 // Now look at the instructions from VNI->def to TaintExtent (inclusive).
2155 MachineBasicBlock *MBB = Indexes->getMBBFromIndex(VNI->def);
2156 MachineBasicBlock::iterator MI = MBB->begin();
2157 if (!VNI->isPHIDef()) {
2158 MI = Indexes->getInstructionFromIndex(VNI->def);
2159 // No need to check the instruction defining VNI for reads.
2162 assert(!SlotIndex::isSameInstr(VNI->def, TaintExtent.front().first) &&
2163 "Interference ends on VNI->def. Should have been handled earlier");
2164 MachineInstr *LastMI =
2165 Indexes->getInstructionFromIndex(TaintExtent.front().first);
2166 assert(LastMI && "Range must end at a proper instruction");
2167 unsigned TaintNum = 0;
2169 assert(MI != MBB->end() && "Bad LastMI");
2170 if (usesLanes(MI, Other.Reg, Other.SubIdx, TaintedLanes)) {
2171 DEBUG(dbgs() << "\t\ttainted lanes used by: " << *MI);
2174 // LastMI is the last instruction to use the current value.
2175 if (&*MI == LastMI) {
2176 if (++TaintNum == TaintExtent.size())
2178 LastMI = Indexes->getInstructionFromIndex(TaintExtent[TaintNum].first);
2179 assert(LastMI && "Range must end at a proper instruction");
2180 TaintedLanes = TaintExtent[TaintNum].second;
2185 // The tainted lanes are unused.
2186 V.Resolution = CR_Replace;
2192 // Determine if ValNo is a copy of a value number in LR or Other.LR that will
2196 // %src = COPY %dst <-- This value to be pruned.
2197 // %dst = COPY %src <-- This value is a copy of a pruned value.
2199 bool JoinVals::isPrunedValue(unsigned ValNo, JoinVals &Other) {
2200 Val &V = Vals[ValNo];
2201 if (V.Pruned || V.PrunedComputed)
2204 if (V.Resolution != CR_Erase && V.Resolution != CR_Merge)
2207 // Follow copies up the dominator tree and check if any intermediate value
2209 V.PrunedComputed = true;
2210 V.Pruned = Other.isPrunedValue(V.OtherVNI->id, *this);
2214 void JoinVals::pruneValues(JoinVals &Other,
2215 SmallVectorImpl<SlotIndex> &EndPoints,
2216 bool changeInstrs) {
2217 for (unsigned i = 0, e = LR.getNumValNums(); i != e; ++i) {
2218 SlotIndex Def = LR.getValNumInfo(i)->def;
2219 switch (Vals[i].Resolution) {
2223 // This value takes precedence over the value in Other.LR.
2224 LIS->pruneValue(Other.LR, Def, &EndPoints);
2225 // Check if we're replacing an IMPLICIT_DEF value. The IMPLICIT_DEF
2226 // instructions are only inserted to provide a live-out value for PHI
2227 // predecessors, so the instruction should simply go away once its value
2228 // has been replaced.
2229 Val &OtherV = Other.Vals[Vals[i].OtherVNI->id];
2230 bool EraseImpDef = OtherV.ErasableImplicitDef &&
2231 OtherV.Resolution == CR_Keep;
2232 if (!Def.isBlock()) {
2234 // Remove <def,read-undef> flags. This def is now a partial redef.
2235 // Also remove <def,dead> flags since the joined live range will
2236 // continue past this instruction.
2237 for (MIOperands MO(Indexes->getInstructionFromIndex(Def));
2238 MO.isValid(); ++MO) {
2239 if (MO->isReg() && MO->isDef() && MO->getReg() == Reg) {
2240 MO->setIsUndef(EraseImpDef);
2241 MO->setIsDead(false);
2245 // This value will reach instructions below, but we need to make sure
2246 // the live range also reaches the instruction at Def.
2248 EndPoints.push_back(Def);
2250 DEBUG(dbgs() << "\t\tpruned " << PrintReg(Other.Reg) << " at " << Def
2251 << ": " << Other.LR << '\n');
2256 if (isPrunedValue(i, Other)) {
2257 // This value is ultimately a copy of a pruned value in LR or Other.LR.
2258 // We can no longer trust the value mapping computed by
2259 // computeAssignment(), the value that was originally copied could have
2261 LIS->pruneValue(LR, Def, &EndPoints);
2262 DEBUG(dbgs() << "\t\tpruned all of " << PrintReg(Reg) << " at "
2263 << Def << ": " << LR << '\n');
2268 llvm_unreachable("Unresolved conflicts");
2273 void JoinVals::pruneSubRegValues(LiveInterval &LI, unsigned &ShrinkMask)
2275 // Look for values being erased.
2276 bool DidPrune = false;
2277 for (unsigned i = 0, e = LR.getNumValNums(); i != e; ++i) {
2278 if (Vals[i].Resolution != CR_Erase)
2281 // Check subranges at the point where the copy will be removed.
2282 SlotIndex Def = LR.getValNumInfo(i)->def;
2283 for (LiveInterval::SubRange &S : LI.subranges()) {
2284 LiveQueryResult Q = S.Query(Def);
2286 // If a subrange starts at the copy then an undefined value has been
2287 // copied and we must remove that subrange value as well.
2288 VNInfo *ValueOut = Q.valueOutOrDead();
2289 if (ValueOut != nullptr && Q.valueIn() == nullptr) {
2290 DEBUG(dbgs() << "\t\tPrune sublane " << format("%04X", S.LaneMask)
2291 << " at " << Def << "\n");
2292 LIS->pruneValue(S, Def, nullptr);
2294 // Mark value number as unused.
2295 ValueOut->markUnused();
2298 // If a subrange ends at the copy, then a value was copied but only
2299 // partially used later. Shrink the subregister range apropriately.
2300 if (Q.valueIn() != nullptr && Q.valueOut() == nullptr) {
2301 DEBUG(dbgs() << "\t\tDead uses at sublane "
2302 << format("%04X", S.LaneMask) << " at " << Def << "\n");
2303 ShrinkMask |= S.LaneMask;
2308 LI.removeEmptySubRanges();
2311 void JoinVals::eraseInstrs(SmallPtrSetImpl<MachineInstr*> &ErasedInstrs,
2312 SmallVectorImpl<unsigned> &ShrinkRegs) {
2313 for (unsigned i = 0, e = LR.getNumValNums(); i != e; ++i) {
2314 // Get the def location before markUnused() below invalidates it.
2315 SlotIndex Def = LR.getValNumInfo(i)->def;
2316 switch (Vals[i].Resolution) {
2318 // If an IMPLICIT_DEF value is pruned, it doesn't serve a purpose any
2319 // longer. The IMPLICIT_DEF instructions are only inserted by
2320 // PHIElimination to guarantee that all PHI predecessors have a value.
2321 if (!Vals[i].ErasableImplicitDef || !Vals[i].Pruned)
2323 // Remove value number i from LR. Note that this VNInfo is still present
2324 // in NewVNInfo, so it will appear as an unused value number in the final
2326 LR.getValNumInfo(i)->markUnused();
2327 LR.removeValNo(LR.getValNumInfo(i));
2328 DEBUG(dbgs() << "\t\tremoved " << i << '@' << Def << ": " << LR << '\n');
2332 MachineInstr *MI = Indexes->getInstructionFromIndex(Def);
2333 assert(MI && "No instruction to erase");
2335 unsigned Reg = MI->getOperand(1).getReg();
2336 if (TargetRegisterInfo::isVirtualRegister(Reg) &&
2337 Reg != CP.getSrcReg() && Reg != CP.getDstReg())
2338 ShrinkRegs.push_back(Reg);
2340 ErasedInstrs.insert(MI);
2341 DEBUG(dbgs() << "\t\terased:\t" << Def << '\t' << *MI);
2342 LIS->RemoveMachineInstrFromMaps(MI);
2343 MI->eraseFromParent();
2352 void RegisterCoalescer::joinSubRegRanges(LiveRange &LRange, LiveRange &RRange,
2354 const CoalescerPair &CP) {
2355 SmallVector<VNInfo*, 16> NewVNInfo;
2356 JoinVals RHSVals(RRange, CP.getSrcReg(), CP.getSrcIdx(), LaneMask,
2357 NewVNInfo, CP, LIS, TRI, true, true);
2358 JoinVals LHSVals(LRange, CP.getDstReg(), CP.getDstIdx(), LaneMask,
2359 NewVNInfo, CP, LIS, TRI, true, true);
2361 /// Compute NewVNInfo and resolve conflicts (see also joinVirtRegs())
2362 /// Conflicts should already be resolved so the mapping/resolution should
2364 if (!LHSVals.mapValues(RHSVals) || !RHSVals.mapValues(LHSVals))
2365 llvm_unreachable("Can't join subrange although main ranges are compatible");
2366 if (!LHSVals.resolveConflicts(RHSVals) || !RHSVals.resolveConflicts(LHSVals))
2367 llvm_unreachable("Can't join subrange although main ranges are compatible");
2369 // The merging algorithm in LiveInterval::join() can't handle conflicting
2370 // value mappings, so we need to remove any live ranges that overlap a
2371 // CR_Replace resolution. Collect a set of end points that can be used to
2372 // restore the live range after joining.
2373 SmallVector<SlotIndex, 8> EndPoints;
2374 LHSVals.pruneValues(RHSVals, EndPoints, false);
2375 RHSVals.pruneValues(LHSVals, EndPoints, false);
2380 // Join RRange into LHS.
2381 LRange.join(RRange, LHSVals.getAssignments(), RHSVals.getAssignments(),
2384 DEBUG(dbgs() << "\t\tjoined lanes: " << LRange << "\n");
2385 if (EndPoints.empty())
2388 // Recompute the parts of the live range we had to remove because of
2389 // CR_Replace conflicts.
2390 DEBUG(dbgs() << "\t\trestoring liveness to " << EndPoints.size()
2391 << " points: " << LRange << '\n');
2392 LIS->extendToIndices(LRange, EndPoints);
2395 void RegisterCoalescer::mergeSubRangeInto(LiveInterval &LI,
2396 const LiveRange &ToMerge,
2397 unsigned LaneMask, CoalescerPair &CP) {
2398 BumpPtrAllocator &Allocator = LIS->getVNInfoAllocator();
2399 for (LiveInterval::SubRange &R : LI.subranges()) {
2400 unsigned RMask = R.LaneMask;
2401 // LaneMask of subregisters common to subrange R and ToMerge.
2402 unsigned Common = RMask & LaneMask;
2403 // There is nothing to do without common subregs.
2407 DEBUG(dbgs() << format("\t\tCopy+Merge %04X into %04X\n", RMask, Common));
2408 // LaneMask of subregisters contained in the R range but not in ToMerge,
2409 // they have to split into their own subrange.
2410 unsigned LRest = RMask & ~LaneMask;
2411 LiveInterval::SubRange *CommonRange;
2414 DEBUG(dbgs() << format("\t\tReduce Lane to %04X\n", LRest));
2415 // Duplicate SubRange for newly merged common stuff.
2416 CommonRange = LI.createSubRangeFrom(Allocator, Common, R);
2418 // Reuse the existing range.
2419 R.LaneMask = Common;
2422 LiveRange RangeCopy(ToMerge, Allocator);
2423 joinSubRegRanges(*CommonRange, RangeCopy, Common, CP);
2427 if (LaneMask != 0) {
2428 DEBUG(dbgs() << format("\t\tNew Lane %04X\n", LaneMask));
2429 LI.createSubRangeFrom(Allocator, LaneMask, ToMerge);
2433 bool RegisterCoalescer::joinVirtRegs(CoalescerPair &CP) {
2434 SmallVector<VNInfo*, 16> NewVNInfo;
2435 LiveInterval &RHS = LIS->getInterval(CP.getSrcReg());
2436 LiveInterval &LHS = LIS->getInterval(CP.getDstReg());
2437 bool TrackSubRegLiveness = MRI->tracksSubRegLiveness();
2438 JoinVals RHSVals(RHS, CP.getSrcReg(), CP.getSrcIdx(), 0, NewVNInfo, CP, LIS,
2439 TRI, false, TrackSubRegLiveness);
2440 JoinVals LHSVals(LHS, CP.getDstReg(), CP.getDstIdx(), 0, NewVNInfo, CP, LIS,
2441 TRI, false, TrackSubRegLiveness);
2443 DEBUG(dbgs() << "\t\tRHS = " << RHS
2444 << "\n\t\tLHS = " << LHS
2447 // First compute NewVNInfo and the simple value mappings.
2448 // Detect impossible conflicts early.
2449 if (!LHSVals.mapValues(RHSVals) || !RHSVals.mapValues(LHSVals))
2452 // Some conflicts can only be resolved after all values have been mapped.
2453 if (!LHSVals.resolveConflicts(RHSVals) || !RHSVals.resolveConflicts(LHSVals))
2456 // All clear, the live ranges can be merged.
2457 if (RHS.hasSubRanges() || LHS.hasSubRanges()) {
2458 BumpPtrAllocator &Allocator = LIS->getVNInfoAllocator();
2460 // Transform lanemasks from the LHS to masks in the coalesced register and
2461 // create initial subranges if necessary.
2462 unsigned DstIdx = CP.getDstIdx();
2463 if (!LHS.hasSubRanges()) {
2464 unsigned Mask = DstIdx == 0 ? CP.getNewRC()->getLaneMask()
2465 : TRI->getSubRegIndexLaneMask(DstIdx);
2466 // LHS must support subregs or we wouldn't be in this codepath.
2468 LHS.createSubRangeFrom(Allocator, Mask, LHS);
2469 } else if (DstIdx != 0) {
2470 // Transform LHS lanemasks to new register class if necessary.
2471 for (LiveInterval::SubRange &R : LHS.subranges()) {
2472 unsigned Mask = TRI->composeSubRegIndexLaneMask(DstIdx, R.LaneMask);
2476 DEBUG(dbgs() << "\t\tLHST = " << PrintReg(CP.getDstReg())
2477 << ' ' << LHS << '\n');
2479 // Determine lanemasks of RHS in the coalesced register and merge subranges.
2480 unsigned SrcIdx = CP.getSrcIdx();
2481 if (!RHS.hasSubRanges()) {
2482 unsigned Mask = SrcIdx == 0 ? CP.getNewRC()->getLaneMask()
2483 : TRI->getSubRegIndexLaneMask(SrcIdx);
2484 mergeSubRangeInto(LHS, RHS, Mask, CP);
2486 // Pair up subranges and merge.
2487 for (LiveInterval::SubRange &R : RHS.subranges()) {
2488 unsigned Mask = TRI->composeSubRegIndexLaneMask(SrcIdx, R.LaneMask);
2489 mergeSubRangeInto(LHS, R, Mask, CP);
2493 DEBUG(dbgs() << "\tJoined SubRanges " << LHS << "\n");
2495 LHSVals.pruneSubRegValues(LHS, ShrinkMask);
2496 RHSVals.pruneSubRegValues(LHS, ShrinkMask);
2499 // The merging algorithm in LiveInterval::join() can't handle conflicting
2500 // value mappings, so we need to remove any live ranges that overlap a
2501 // CR_Replace resolution. Collect a set of end points that can be used to
2502 // restore the live range after joining.
2503 SmallVector<SlotIndex, 8> EndPoints;
2504 LHSVals.pruneValues(RHSVals, EndPoints, true);
2505 RHSVals.pruneValues(LHSVals, EndPoints, true);
2507 // Erase COPY and IMPLICIT_DEF instructions. This may cause some external
2508 // registers to require trimming.
2509 SmallVector<unsigned, 8> ShrinkRegs;
2510 LHSVals.eraseInstrs(ErasedInstrs, ShrinkRegs);
2511 RHSVals.eraseInstrs(ErasedInstrs, ShrinkRegs);
2512 while (!ShrinkRegs.empty())
2513 LIS->shrinkToUses(&LIS->getInterval(ShrinkRegs.pop_back_val()));
2515 // Join RHS into LHS.
2516 LHS.join(RHS, LHSVals.getAssignments(), RHSVals.getAssignments(), NewVNInfo);
2518 // Kill flags are going to be wrong if the live ranges were overlapping.
2519 // Eventually, we should simply clear all kill flags when computing live
2520 // ranges. They are reinserted after register allocation.
2521 MRI->clearKillFlags(LHS.reg);
2522 MRI->clearKillFlags(RHS.reg);
2524 if (!EndPoints.empty()) {
2525 // Recompute the parts of the live range we had to remove because of
2526 // CR_Replace conflicts.
2527 DEBUG(dbgs() << "\t\trestoring liveness to " << EndPoints.size()
2528 << " points: " << LHS << '\n');
2529 LIS->extendToIndices((LiveRange&)LHS, EndPoints);
2535 /// Attempt to join these two intervals. On failure, this returns false.
2536 bool RegisterCoalescer::joinIntervals(CoalescerPair &CP) {
2537 return CP.isPhys() ? joinReservedPhysReg(CP) : joinVirtRegs(CP);
2541 // Information concerning MBB coalescing priority.
2542 struct MBBPriorityInfo {
2543 MachineBasicBlock *MBB;
2547 MBBPriorityInfo(MachineBasicBlock *mbb, unsigned depth, bool issplit)
2548 : MBB(mbb), Depth(depth), IsSplit(issplit) {}
2552 // C-style comparator that sorts first based on the loop depth of the basic
2553 // block (the unsigned), and then on the MBB number.
2555 // EnableGlobalCopies assumes that the primary sort key is loop depth.
2556 static int compareMBBPriority(const MBBPriorityInfo *LHS,
2557 const MBBPriorityInfo *RHS) {
2558 // Deeper loops first
2559 if (LHS->Depth != RHS->Depth)
2560 return LHS->Depth > RHS->Depth ? -1 : 1;
2562 // Try to unsplit critical edges next.
2563 if (LHS->IsSplit != RHS->IsSplit)
2564 return LHS->IsSplit ? -1 : 1;
2566 // Prefer blocks that are more connected in the CFG. This takes care of
2567 // the most difficult copies first while intervals are short.
2568 unsigned cl = LHS->MBB->pred_size() + LHS->MBB->succ_size();
2569 unsigned cr = RHS->MBB->pred_size() + RHS->MBB->succ_size();
2571 return cl > cr ? -1 : 1;
2573 // As a last resort, sort by block number.
2574 return LHS->MBB->getNumber() < RHS->MBB->getNumber() ? -1 : 1;
2577 /// \returns true if the given copy uses or defines a local live range.
2578 static bool isLocalCopy(MachineInstr *Copy, const LiveIntervals *LIS) {
2579 if (!Copy->isCopy())
2582 if (Copy->getOperand(1).isUndef())
2585 unsigned SrcReg = Copy->getOperand(1).getReg();
2586 unsigned DstReg = Copy->getOperand(0).getReg();
2587 if (TargetRegisterInfo::isPhysicalRegister(SrcReg)
2588 || TargetRegisterInfo::isPhysicalRegister(DstReg))
2591 return LIS->intervalIsInOneMBB(LIS->getInterval(SrcReg))
2592 || LIS->intervalIsInOneMBB(LIS->getInterval(DstReg));
2595 // Try joining WorkList copies starting from index From.
2596 // Null out any successful joins.
2597 bool RegisterCoalescer::
2598 copyCoalesceWorkList(MutableArrayRef<MachineInstr*> CurrList) {
2599 bool Progress = false;
2600 for (unsigned i = 0, e = CurrList.size(); i != e; ++i) {
2603 // Skip instruction pointers that have already been erased, for example by
2604 // dead code elimination.
2605 if (ErasedInstrs.erase(CurrList[i])) {
2606 CurrList[i] = nullptr;
2610 bool Success = joinCopy(CurrList[i], Again);
2611 Progress |= Success;
2612 if (Success || !Again)
2613 CurrList[i] = nullptr;
2619 RegisterCoalescer::copyCoalesceInMBB(MachineBasicBlock *MBB) {
2620 DEBUG(dbgs() << MBB->getName() << ":\n");
2622 // Collect all copy-like instructions in MBB. Don't start coalescing anything
2623 // yet, it might invalidate the iterator.
2624 const unsigned PrevSize = WorkList.size();
2625 if (JoinGlobalCopies) {
2626 // Coalesce copies bottom-up to coalesce local defs before local uses. They
2627 // are not inherently easier to resolve, but slightly preferable until we
2628 // have local live range splitting. In particular this is required by
2629 // cmp+jmp macro fusion.
2630 for (MachineBasicBlock::iterator MII = MBB->begin(), E = MBB->end();
2632 if (!MII->isCopyLike())
2634 if (isLocalCopy(&(*MII), LIS))
2635 LocalWorkList.push_back(&(*MII));
2637 WorkList.push_back(&(*MII));
2641 for (MachineBasicBlock::iterator MII = MBB->begin(), E = MBB->end();
2643 if (MII->isCopyLike())
2644 WorkList.push_back(MII);
2646 // Try coalescing the collected copies immediately, and remove the nulls.
2647 // This prevents the WorkList from getting too large since most copies are
2648 // joinable on the first attempt.
2649 MutableArrayRef<MachineInstr*>
2650 CurrList(WorkList.begin() + PrevSize, WorkList.end());
2651 if (copyCoalesceWorkList(CurrList))
2652 WorkList.erase(std::remove(WorkList.begin() + PrevSize, WorkList.end(),
2653 (MachineInstr*)nullptr), WorkList.end());
2656 void RegisterCoalescer::coalesceLocals() {
2657 copyCoalesceWorkList(LocalWorkList);
2658 for (unsigned j = 0, je = LocalWorkList.size(); j != je; ++j) {
2659 if (LocalWorkList[j])
2660 WorkList.push_back(LocalWorkList[j]);
2662 LocalWorkList.clear();
2665 void RegisterCoalescer::joinAllIntervals() {
2666 DEBUG(dbgs() << "********** JOINING INTERVALS ***********\n");
2667 assert(WorkList.empty() && LocalWorkList.empty() && "Old data still around.");
2669 std::vector<MBBPriorityInfo> MBBs;
2670 MBBs.reserve(MF->size());
2671 for (MachineFunction::iterator I = MF->begin(), E = MF->end();I != E;++I){
2672 MachineBasicBlock *MBB = I;
2673 MBBs.push_back(MBBPriorityInfo(MBB, Loops->getLoopDepth(MBB),
2674 JoinSplitEdges && isSplitEdge(MBB)));
2676 array_pod_sort(MBBs.begin(), MBBs.end(), compareMBBPriority);
2678 // Coalesce intervals in MBB priority order.
2679 unsigned CurrDepth = UINT_MAX;
2680 for (unsigned i = 0, e = MBBs.size(); i != e; ++i) {
2681 // Try coalescing the collected local copies for deeper loops.
2682 if (JoinGlobalCopies && MBBs[i].Depth < CurrDepth) {
2684 CurrDepth = MBBs[i].Depth;
2686 copyCoalesceInMBB(MBBs[i].MBB);
2690 // Joining intervals can allow other intervals to be joined. Iteratively join
2691 // until we make no progress.
2692 while (copyCoalesceWorkList(WorkList))
2696 void RegisterCoalescer::releaseMemory() {
2697 ErasedInstrs.clear();
2700 InflateRegs.clear();
2703 bool RegisterCoalescer::runOnMachineFunction(MachineFunction &fn) {
2705 MRI = &fn.getRegInfo();
2706 TM = &fn.getTarget();
2707 TRI = TM->getSubtargetImpl()->getRegisterInfo();
2708 TII = TM->getSubtargetImpl()->getInstrInfo();
2709 LIS = &getAnalysis<LiveIntervals>();
2710 AA = &getAnalysis<AliasAnalysis>();
2711 Loops = &getAnalysis<MachineLoopInfo>();
2713 const TargetSubtargetInfo &ST = TM->getSubtarget<TargetSubtargetInfo>();
2714 if (EnableGlobalCopies == cl::BOU_UNSET)
2715 JoinGlobalCopies = ST.useMachineScheduler();
2717 JoinGlobalCopies = (EnableGlobalCopies == cl::BOU_TRUE);
2719 // The MachineScheduler does not currently require JoinSplitEdges. This will
2720 // either be enabled unconditionally or replaced by a more general live range
2721 // splitting optimization.
2722 JoinSplitEdges = EnableJoinSplits;
2724 DEBUG(dbgs() << "********** SIMPLE REGISTER COALESCING **********\n"
2725 << "********** Function: " << MF->getName() << '\n');
2727 if (VerifyCoalescing)
2728 MF->verify(this, "Before register coalescing");
2730 RegClassInfo.runOnMachineFunction(fn);
2732 // Join (coalesce) intervals if requested.
2736 // After deleting a lot of copies, register classes may be less constrained.
2737 // Removing sub-register operands may allow GR32_ABCD -> GR32 and DPR_VFP2 ->
2739 array_pod_sort(InflateRegs.begin(), InflateRegs.end());
2740 InflateRegs.erase(std::unique(InflateRegs.begin(), InflateRegs.end()),
2742 DEBUG(dbgs() << "Trying to inflate " << InflateRegs.size() << " regs.\n");
2743 for (unsigned i = 0, e = InflateRegs.size(); i != e; ++i) {
2744 unsigned Reg = InflateRegs[i];
2745 if (MRI->reg_nodbg_empty(Reg))
2747 if (MRI->recomputeRegClass(Reg, *TM)) {
2748 DEBUG(dbgs() << PrintReg(Reg) << " inflated to "
2749 << TRI->getRegClassName(MRI->getRegClass(Reg)) << '\n');
2750 LiveInterval &LI = LIS->getInterval(Reg);
2751 unsigned MaxMask = MRI->getMaxLaneMaskForVReg(Reg);
2753 // If the inflated register class does not support subregisters anymore
2754 // remove the subranges.
2755 LI.clearSubRanges();
2757 // If subranges are still supported, then the same subregs should still
2760 for (LiveInterval::SubRange &S : LI.subranges()) {
2761 assert ((S.LaneMask & ~MaxMask) == 0);
2770 if (VerifyCoalescing)
2771 MF->verify(this, "After register coalescing");
2775 /// Implement the dump method.
2776 void RegisterCoalescer::print(raw_ostream &O, const Module* m) const {