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 for eliminateDeadDefs().
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 /// Tries to coalesce all copies in CurrList. Returns true if any progress
138 bool copyCoalesceWorkList(MutableArrayRef<MachineInstr*> CurrList);
140 /// Attempt to join intervals corresponding to SrcReg/DstReg, which are the
141 /// src/dst of the copy instruction CopyMI. This returns true if the copy
142 /// was successfully coalesced away. If it is not currently possible to
143 /// coalesce this interval, but it may be possible if other things get
144 /// coalesced, then it returns true by reference in 'Again'.
145 bool joinCopy(MachineInstr *TheCopy, bool &Again);
147 /// Attempt to join these two intervals. On failure, this
148 /// returns false. The output "SrcInt" will not have been modified, so we
149 /// can use this information below to update aliases.
150 bool joinIntervals(CoalescerPair &CP);
152 /// Attempt joining two virtual registers. Return true on success.
153 bool joinVirtRegs(CoalescerPair &CP);
155 /// Attempt joining with a reserved physreg.
156 bool joinReservedPhysReg(CoalescerPair &CP);
158 /// Add the LiveRange @p ToMerge as a subregister liverange of @p LI.
159 /// Subranges in @p LI which only partially interfere with the desired
160 /// LaneMask are split as necessary. @p LaneMask are the lanes that
161 /// @p ToMerge will occupy in the coalescer register. @p LI has its subrange
162 /// lanemasks already adjusted to the coalesced register.
163 void mergeSubRangeInto(LiveInterval &LI, const LiveRange &ToMerge,
164 unsigned LaneMask, CoalescerPair &CP);
166 /// Join the liveranges of two subregisters. Joins @p RRange into
167 /// @p LRange, @p RRange may be invalid afterwards.
168 void joinSubRegRanges(LiveRange &LRange, LiveRange &RRange,
169 unsigned LaneMask, const CoalescerPair &CP);
171 /// We found a non-trivially-coalescable copy. If the source value number is
172 /// defined by a copy from the destination reg see if we can merge these two
173 /// destination reg valno# into a single value number, eliminating a copy.
174 /// This returns true if an interval was modified.
175 bool adjustCopiesBackFrom(const CoalescerPair &CP, MachineInstr *CopyMI);
177 /// Return true if there are definitions of IntB
178 /// other than BValNo val# that can reach uses of AValno val# of IntA.
179 bool hasOtherReachingDefs(LiveInterval &IntA, LiveInterval &IntB,
180 VNInfo *AValNo, VNInfo *BValNo);
182 /// We found a non-trivially-coalescable copy.
183 /// If the source value number is defined by a commutable instruction and
184 /// its other operand is coalesced to the copy dest register, see if we
185 /// can transform the copy into a noop by commuting the definition.
186 /// This returns true if an interval was modified.
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 copy involving a physreg should be joined.
195 bool canJoinPhys(const CoalescerPair &CP);
197 /// Replace all defs and uses of SrcReg to DstReg and update the subregister
198 /// number if it is not zero. If DstReg is a physical register and the
199 /// existing subregister number of the def / use being updated is not zero,
200 /// make sure to set it to the correct physical subregister.
201 void updateRegDefsUses(unsigned SrcReg, unsigned DstReg, unsigned SubIdx);
203 /// Handle copies of undef values.
204 /// Returns true if @p CopyMI was a copy of an undef value and eliminated.
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 void RegisterCoalescer::LRE_WillEraseInstruction(MachineInstr *MI) {
427 // MI may be in WorkList. Make sure we don't visit it.
428 ErasedInstrs.insert(MI);
431 bool RegisterCoalescer::adjustCopiesBackFrom(const CoalescerPair &CP,
432 MachineInstr *CopyMI) {
433 assert(!CP.isPartial() && "This doesn't work for partial copies.");
434 assert(!CP.isPhys() && "This doesn't work for physreg copies.");
437 LIS->getInterval(CP.isFlipped() ? CP.getDstReg() : CP.getSrcReg());
439 LIS->getInterval(CP.isFlipped() ? CP.getSrcReg() : CP.getDstReg());
440 SlotIndex CopyIdx = LIS->getInstructionIndex(CopyMI).getRegSlot();
442 // We have a non-trivially-coalescable copy with IntA being the source and
443 // IntB being the dest, thus this defines a value number in IntB. If the
444 // source value number (in IntA) is defined by a copy from B, see if we can
445 // merge these two pieces of B into a single value number, eliminating a copy.
450 // B1 = A3 <- this copy
452 // In this case, B0 can be extended to where the B1 copy lives, allowing the
453 // B1 value number to be replaced with B0 (which simplifies the B
456 // BValNo is a value number in B that is defined by a copy from A. 'B1' in
457 // the example above.
458 LiveInterval::iterator BS = IntB.FindSegmentContaining(CopyIdx);
459 if (BS == IntB.end()) return false;
460 VNInfo *BValNo = BS->valno;
462 // Get the location that B is defined at. Two options: either this value has
463 // an unknown definition point or it is defined at CopyIdx. If unknown, we
465 if (BValNo->def != CopyIdx) return false;
467 // AValNo is the value number in A that defines the copy, A3 in the example.
468 SlotIndex CopyUseIdx = CopyIdx.getRegSlot(true);
469 LiveInterval::iterator AS = IntA.FindSegmentContaining(CopyUseIdx);
470 // The live segment might not exist after fun with physreg coalescing.
471 if (AS == IntA.end()) return false;
472 VNInfo *AValNo = AS->valno;
474 // If AValNo is defined as a copy from IntB, we can potentially process this.
475 // Get the instruction that defines this value number.
476 MachineInstr *ACopyMI = LIS->getInstructionFromIndex(AValNo->def);
477 // Don't allow any partial copies, even if isCoalescable() allows them.
478 if (!CP.isCoalescable(ACopyMI) || !ACopyMI->isFullCopy())
481 // Get the Segment in IntB that this value number starts with.
482 LiveInterval::iterator ValS =
483 IntB.FindSegmentContaining(AValNo->def.getPrevSlot());
484 if (ValS == IntB.end())
487 // Make sure that the end of the live segment is inside the same block as
489 MachineInstr *ValSEndInst =
490 LIS->getInstructionFromIndex(ValS->end.getPrevSlot());
491 if (!ValSEndInst || ValSEndInst->getParent() != CopyMI->getParent())
494 // Okay, we now know that ValS ends in the same block that the CopyMI
495 // live-range starts. If there are no intervening live segments between them
496 // in IntB, we can merge them.
497 if (ValS+1 != BS) return false;
499 DEBUG(dbgs() << "Extending: " << PrintReg(IntB.reg, TRI));
501 SlotIndex FillerStart = ValS->end, FillerEnd = BS->start;
502 // We are about to delete CopyMI, so need to remove it as the 'instruction
503 // that defines this value #'. Update the valnum with the new defining
505 BValNo->def = FillerStart;
507 // Okay, we can merge them. We need to insert a new liverange:
508 // [ValS.end, BS.begin) of either value number, then we merge the
509 // two value numbers.
510 IntB.addSegment(LiveInterval::Segment(FillerStart, FillerEnd, BValNo));
512 // Okay, merge "B1" into the same value number as "B0".
513 if (BValNo != ValS->valno)
514 IntB.MergeValueNumberInto(BValNo, ValS->valno);
516 // Do the same for the subregister segments.
517 for (LiveInterval::SubRange &S : IntB.subranges()) {
518 VNInfo *SubBValNo = S.getVNInfoAt(CopyIdx);
519 S.addSegment(LiveInterval::Segment(FillerStart, FillerEnd, SubBValNo));
520 VNInfo *SubValSNo = S.getVNInfoAt(AValNo->def.getPrevSlot());
521 if (SubBValNo != SubValSNo)
522 S.MergeValueNumberInto(SubBValNo, SubValSNo);
525 DEBUG(dbgs() << " result = " << IntB << '\n');
527 // If the source instruction was killing the source register before the
528 // merge, unset the isKill marker given the live range has been extended.
529 int UIdx = ValSEndInst->findRegisterUseOperandIdx(IntB.reg, true);
531 ValSEndInst->getOperand(UIdx).setIsKill(false);
534 // Rewrite the copy. If the copy instruction was killing the destination
535 // register before the merge, find the last use and trim the live range. That
536 // will also add the isKill marker.
537 CopyMI->substituteRegister(IntA.reg, IntB.reg, 0, *TRI);
538 if (AS->end == CopyIdx)
539 LIS->shrinkToUses(&IntA);
545 bool RegisterCoalescer::hasOtherReachingDefs(LiveInterval &IntA,
549 // If AValNo has PHI kills, conservatively assume that IntB defs can reach
551 if (LIS->hasPHIKill(IntA, AValNo))
554 for (LiveRange::Segment &ASeg : IntA.segments) {
555 if (ASeg.valno != AValNo) continue;
556 LiveInterval::iterator BI =
557 std::upper_bound(IntB.begin(), IntB.end(), ASeg.start);
558 if (BI != IntB.begin())
560 for (; BI != IntB.end() && ASeg.end >= BI->start; ++BI) {
561 if (BI->valno == BValNo)
563 if (BI->start <= ASeg.start && BI->end > ASeg.start)
565 if (BI->start > ASeg.start && BI->start < ASeg.end)
572 /// Copy segements with value number @p SrcValNo from liverange @p Src to live
573 /// range @Dst and use value number @p DstValNo there.
574 static void addSegmentsWithValNo(LiveRange &Dst, VNInfo *DstValNo,
575 const LiveRange &Src, const VNInfo *SrcValNo)
577 for (const LiveRange::Segment &S : Src.segments) {
578 if (S.valno != SrcValNo)
580 Dst.addSegment(LiveRange::Segment(S.start, S.end, DstValNo));
584 bool RegisterCoalescer::removeCopyByCommutingDef(const CoalescerPair &CP,
585 MachineInstr *CopyMI) {
586 assert(!CP.isPhys());
589 LIS->getInterval(CP.isFlipped() ? CP.getDstReg() : CP.getSrcReg());
591 LIS->getInterval(CP.isFlipped() ? CP.getSrcReg() : CP.getDstReg());
593 // We found a non-trivially-coalescable copy with IntA being the source and
594 // IntB being the dest, thus this defines a value number in IntB. If the
595 // source value number (in IntA) is defined by a commutable instruction and
596 // its other operand is coalesced to the copy dest register, see if we can
597 // transform the copy into a noop by commuting the definition. For example,
599 // A3 = op A2 B0<kill>
601 // B1 = A3 <- this copy
603 // = op A3 <- more uses
607 // B2 = op B0 A2<kill>
609 // B1 = B2 <- now an identity copy
611 // = op B2 <- more uses
613 // BValNo is a value number in B that is defined by a copy from A. 'B1' in
614 // the example above.
615 SlotIndex CopyIdx = LIS->getInstructionIndex(CopyMI).getRegSlot();
616 VNInfo *BValNo = IntB.getVNInfoAt(CopyIdx);
617 assert(BValNo != nullptr && BValNo->def == CopyIdx);
619 // AValNo is the value number in A that defines the copy, A3 in the example.
620 VNInfo *AValNo = IntA.getVNInfoAt(CopyIdx.getRegSlot(true));
621 assert(AValNo && !AValNo->isUnused() && "COPY source not live");
622 if (AValNo->isPHIDef())
624 MachineInstr *DefMI = LIS->getInstructionFromIndex(AValNo->def);
627 if (!DefMI->isCommutable())
629 // If DefMI is a two-address instruction then commuting it will change the
630 // destination register.
631 int DefIdx = DefMI->findRegisterDefOperandIdx(IntA.reg);
632 assert(DefIdx != -1);
634 if (!DefMI->isRegTiedToUseOperand(DefIdx, &UseOpIdx))
636 unsigned Op1, Op2, NewDstIdx;
637 if (!TII->findCommutedOpIndices(DefMI, Op1, Op2))
641 else if (Op2 == UseOpIdx)
646 MachineOperand &NewDstMO = DefMI->getOperand(NewDstIdx);
647 unsigned NewReg = NewDstMO.getReg();
648 if (NewReg != IntB.reg || !IntB.Query(AValNo->def).isKill())
651 // Make sure there are no other definitions of IntB that would reach the
652 // uses which the new definition can reach.
653 if (hasOtherReachingDefs(IntA, IntB, AValNo, BValNo))
656 // If some of the uses of IntA.reg is already coalesced away, return false.
657 // It's not possible to determine whether it's safe to perform the coalescing.
658 for (MachineOperand &MO : MRI->use_nodbg_operands(IntA.reg)) {
659 MachineInstr *UseMI = MO.getParent();
660 unsigned OpNo = &MO - &UseMI->getOperand(0);
661 SlotIndex UseIdx = LIS->getInstructionIndex(UseMI);
662 LiveInterval::iterator US = IntA.FindSegmentContaining(UseIdx);
663 if (US == IntA.end() || US->valno != AValNo)
665 // If this use is tied to a def, we can't rewrite the register.
666 if (UseMI->isRegTiedToDefOperand(OpNo))
670 DEBUG(dbgs() << "\tremoveCopyByCommutingDef: " << AValNo->def << '\t'
673 // At this point we have decided that it is legal to do this
674 // transformation. Start by commuting the instruction.
675 MachineBasicBlock *MBB = DefMI->getParent();
676 MachineInstr *NewMI = TII->commuteInstruction(DefMI);
679 if (TargetRegisterInfo::isVirtualRegister(IntA.reg) &&
680 TargetRegisterInfo::isVirtualRegister(IntB.reg) &&
681 !MRI->constrainRegClass(IntB.reg, MRI->getRegClass(IntA.reg)))
683 if (NewMI != DefMI) {
684 LIS->ReplaceMachineInstrInMaps(DefMI, NewMI);
685 MachineBasicBlock::iterator Pos = DefMI;
686 MBB->insert(Pos, NewMI);
690 // If ALR and BLR overlaps and end of BLR extends beyond end of ALR, e.g.
699 // Update uses of IntA of the specific Val# with IntB.
700 for (MachineRegisterInfo::use_iterator UI = MRI->use_begin(IntA.reg),
702 UI != UE; /* ++UI is below because of possible MI removal */) {
703 MachineOperand &UseMO = *UI;
707 MachineInstr *UseMI = UseMO.getParent();
708 if (UseMI->isDebugValue()) {
709 // FIXME These don't have an instruction index. Not clear we have enough
710 // info to decide whether to do this replacement or not. For now do it.
711 UseMO.setReg(NewReg);
714 SlotIndex UseIdx = LIS->getInstructionIndex(UseMI).getRegSlot(true);
715 LiveInterval::iterator US = IntA.FindSegmentContaining(UseIdx);
716 assert(US != IntA.end() && "Use must be live");
717 if (US->valno != AValNo)
719 // Kill flags are no longer accurate. They are recomputed after RA.
720 UseMO.setIsKill(false);
721 if (TargetRegisterInfo::isPhysicalRegister(NewReg))
722 UseMO.substPhysReg(NewReg, *TRI);
724 UseMO.setReg(NewReg);
727 if (!UseMI->isCopy())
729 if (UseMI->getOperand(0).getReg() != IntB.reg ||
730 UseMI->getOperand(0).getSubReg())
733 // This copy will become a noop. If it's defining a new val#, merge it into
735 SlotIndex DefIdx = UseIdx.getRegSlot();
736 VNInfo *DVNI = IntB.getVNInfoAt(DefIdx);
739 DEBUG(dbgs() << "\t\tnoop: " << DefIdx << '\t' << *UseMI);
740 assert(DVNI->def == DefIdx);
741 BValNo = IntB.MergeValueNumberInto(DVNI, BValNo);
742 for (LiveInterval::SubRange &S : IntB.subranges()) {
743 VNInfo *SubDVNI = S.getVNInfoAt(DefIdx);
746 VNInfo *SubBValNo = S.getVNInfoAt(CopyIdx);
747 assert(SubBValNo->def == CopyIdx);
748 S.MergeValueNumberInto(SubDVNI, SubBValNo);
751 ErasedInstrs.insert(UseMI);
752 LIS->RemoveMachineInstrFromMaps(UseMI);
753 UseMI->eraseFromParent();
756 // Extend BValNo by merging in IntA live segments of AValNo. Val# definition
758 BumpPtrAllocator &Allocator = LIS->getVNInfoAllocator();
759 if (IntB.hasSubRanges()) {
760 if (!IntA.hasSubRanges()) {
761 unsigned Mask = MRI->getMaxLaneMaskForVReg(IntA.reg);
762 IntA.createSubRangeFrom(Allocator, Mask, IntA);
764 SlotIndex AIdx = CopyIdx.getRegSlot(true);
765 for (LiveInterval::SubRange &SA : IntA.subranges()) {
766 VNInfo *ASubValNo = SA.getVNInfoAt(AIdx);
767 assert(ASubValNo != nullptr);
769 unsigned AMask = SA.LaneMask;
770 for (LiveInterval::SubRange &SB : IntB.subranges()) {
771 unsigned BMask = SB.LaneMask;
772 unsigned Common = BMask & AMask;
777 dbgs() << format("\t\tCopy+Merge %04X into %04X\n", BMask, Common));
778 unsigned BRest = BMask & ~AMask;
779 LiveInterval::SubRange *CommonRange;
782 DEBUG(dbgs() << format("\t\tReduce Lane to %04X\n", BRest));
783 // Duplicate SubRange for newly merged common stuff.
784 CommonRange = IntB.createSubRangeFrom(Allocator, Common, SB);
786 // We van reuse the L SubRange.
787 SB.LaneMask = Common;
790 LiveRange RangeCopy(SB, Allocator);
792 VNInfo *BSubValNo = CommonRange->getVNInfoAt(CopyIdx);
793 assert(BSubValNo->def == CopyIdx);
794 BSubValNo->def = ASubValNo->def;
795 addSegmentsWithValNo(*CommonRange, BSubValNo, SA, ASubValNo);
799 DEBUG(dbgs() << format("\t\tNew Lane %04X\n", AMask));
800 LiveRange *NewRange = IntB.createSubRange(Allocator, AMask);
801 VNInfo *BSubValNo = NewRange->getNextValue(CopyIdx, Allocator);
802 addSegmentsWithValNo(*NewRange, BSubValNo, SA, ASubValNo);
807 BValNo->def = AValNo->def;
808 addSegmentsWithValNo(IntB, BValNo, IntA, AValNo);
809 DEBUG(dbgs() << "\t\textended: " << IntB << '\n');
811 LIS->removeVRegDefAt(IntA, AValNo->def);
813 DEBUG(dbgs() << "\t\ttrimmed: " << IntA << '\n');
818 bool RegisterCoalescer::reMaterializeTrivialDef(CoalescerPair &CP,
819 MachineInstr *CopyMI,
822 unsigned SrcReg = CP.isFlipped() ? CP.getDstReg() : CP.getSrcReg();
823 unsigned SrcIdx = CP.isFlipped() ? CP.getDstIdx() : CP.getSrcIdx();
824 unsigned DstReg = CP.isFlipped() ? CP.getSrcReg() : CP.getDstReg();
825 unsigned DstIdx = CP.isFlipped() ? CP.getSrcIdx() : CP.getDstIdx();
826 if (TargetRegisterInfo::isPhysicalRegister(SrcReg))
829 LiveInterval &SrcInt = LIS->getInterval(SrcReg);
830 SlotIndex CopyIdx = LIS->getInstructionIndex(CopyMI);
831 VNInfo *ValNo = SrcInt.Query(CopyIdx).valueIn();
832 assert(ValNo && "CopyMI input register not live");
833 if (ValNo->isPHIDef() || ValNo->isUnused())
835 MachineInstr *DefMI = LIS->getInstructionFromIndex(ValNo->def);
838 if (DefMI->isCopyLike()) {
842 if (!TII->isAsCheapAsAMove(DefMI))
844 if (!TII->isTriviallyReMaterializable(DefMI, AA))
846 bool SawStore = false;
847 if (!DefMI->isSafeToMove(TII, AA, SawStore))
849 const MCInstrDesc &MCID = DefMI->getDesc();
850 if (MCID.getNumDefs() != 1)
852 // Only support subregister destinations when the def is read-undef.
853 MachineOperand &DstOperand = CopyMI->getOperand(0);
854 unsigned CopyDstReg = DstOperand.getReg();
855 if (DstOperand.getSubReg() && !DstOperand.isUndef())
858 // If both SrcIdx and DstIdx are set, correct rematerialization would widen
859 // the register substantially (beyond both source and dest size). This is bad
860 // for performance since it can cascade through a function, introducing many
861 // extra spills and fills (e.g. ARM can easily end up copying QQQQPR registers
862 // around after a few subreg copies).
863 if (SrcIdx && DstIdx)
866 const TargetRegisterClass *DefRC = TII->getRegClass(MCID, 0, TRI, *MF);
867 if (!DefMI->isImplicitDef()) {
868 if (TargetRegisterInfo::isPhysicalRegister(DstReg)) {
869 unsigned NewDstReg = DstReg;
871 unsigned NewDstIdx = TRI->composeSubRegIndices(CP.getSrcIdx(),
872 DefMI->getOperand(0).getSubReg());
874 NewDstReg = TRI->getSubReg(DstReg, NewDstIdx);
876 // Finally, make sure that the physical subregister that will be
877 // constructed later is permitted for the instruction.
878 if (!DefRC->contains(NewDstReg))
881 // Theoretically, some stack frame reference could exist. Just make sure
882 // it hasn't actually happened.
883 assert(TargetRegisterInfo::isVirtualRegister(DstReg) &&
884 "Only expect to deal with virtual or physical registers");
888 MachineBasicBlock *MBB = CopyMI->getParent();
889 MachineBasicBlock::iterator MII =
890 std::next(MachineBasicBlock::iterator(CopyMI));
891 TII->reMaterialize(*MBB, MII, DstReg, SrcIdx, DefMI, *TRI);
892 MachineInstr *NewMI = std::prev(MII);
894 LIS->ReplaceMachineInstrInMaps(CopyMI, NewMI);
895 CopyMI->eraseFromParent();
896 ErasedInstrs.insert(CopyMI);
898 // NewMI may have dead implicit defs (E.g. EFLAGS for MOV<bits>r0 on X86).
899 // We need to remember these so we can add intervals once we insert
900 // NewMI into SlotIndexes.
901 SmallVector<unsigned, 4> NewMIImplDefs;
902 for (unsigned i = NewMI->getDesc().getNumOperands(),
903 e = NewMI->getNumOperands(); i != e; ++i) {
904 MachineOperand &MO = NewMI->getOperand(i);
906 assert(MO.isDef() && MO.isImplicit() && MO.isDead() &&
907 TargetRegisterInfo::isPhysicalRegister(MO.getReg()));
908 NewMIImplDefs.push_back(MO.getReg());
912 if (TargetRegisterInfo::isVirtualRegister(DstReg)) {
913 const TargetRegisterClass *NewRC = CP.getNewRC();
914 unsigned NewIdx = NewMI->getOperand(0).getSubReg();
917 NewRC = TRI->getMatchingSuperRegClass(NewRC, DefRC, NewIdx);
919 NewRC = TRI->getCommonSubClass(NewRC, DefRC);
921 assert(NewRC && "subreg chosen for remat incompatible with instruction");
922 MRI->setRegClass(DstReg, NewRC);
924 updateRegDefsUses(DstReg, DstReg, DstIdx);
925 NewMI->getOperand(0).setSubReg(NewIdx);
926 } else if (NewMI->getOperand(0).getReg() != CopyDstReg) {
927 // The New instruction may be defining a sub-register of what's actually
928 // been asked for. If so it must implicitly define the whole thing.
929 assert(TargetRegisterInfo::isPhysicalRegister(DstReg) &&
930 "Only expect virtual or physical registers in remat");
931 NewMI->getOperand(0).setIsDead(true);
932 NewMI->addOperand(MachineOperand::CreateReg(CopyDstReg,
936 // Record small dead def live-ranges for all the subregisters
937 // of the destination register.
938 // Otherwise, variables that live through may miss some
939 // interferences, thus creating invalid allocation.
941 // vreg1 = somedef ; vreg1 GR8
942 // vreg2 = remat ; vreg2 GR32
943 // CL = COPY vreg2.sub_8bit
944 // = somedef vreg1 ; vreg1 GR8
946 // vreg1 = somedef ; vreg1 GR8
947 // ECX<def, dead> = remat ; CL<imp-def>
948 // = somedef vreg1 ; vreg1 GR8
949 // vreg1 will see the inteferences with CL but not with CH since
950 // no live-ranges would have been created for ECX.
952 SlotIndex NewMIIdx = LIS->getInstructionIndex(NewMI);
953 for (MCRegUnitIterator Units(NewMI->getOperand(0).getReg(), TRI);
954 Units.isValid(); ++Units)
955 if (LiveRange *LR = LIS->getCachedRegUnit(*Units))
956 LR->createDeadDef(NewMIIdx.getRegSlot(), LIS->getVNInfoAllocator());
959 if (NewMI->getOperand(0).getSubReg())
960 NewMI->getOperand(0).setIsUndef();
962 // CopyMI may have implicit operands, transfer them over to the newly
963 // rematerialized instruction. And update implicit def interval valnos.
964 for (unsigned i = CopyMI->getDesc().getNumOperands(),
965 e = CopyMI->getNumOperands(); i != e; ++i) {
966 MachineOperand &MO = CopyMI->getOperand(i);
968 assert(MO.isImplicit() && "No explicit operands after implict operands.");
969 // Discard VReg implicit defs.
970 if (TargetRegisterInfo::isPhysicalRegister(MO.getReg())) {
971 NewMI->addOperand(MO);
976 SlotIndex NewMIIdx = LIS->getInstructionIndex(NewMI);
977 for (unsigned i = 0, e = NewMIImplDefs.size(); i != e; ++i) {
978 unsigned Reg = NewMIImplDefs[i];
979 for (MCRegUnitIterator Units(Reg, TRI); Units.isValid(); ++Units)
980 if (LiveRange *LR = LIS->getCachedRegUnit(*Units))
981 LR->createDeadDef(NewMIIdx.getRegSlot(), LIS->getVNInfoAllocator());
984 DEBUG(dbgs() << "Remat: " << *NewMI);
987 // The source interval can become smaller because we removed a use.
988 LIS->shrinkToUses(&SrcInt, &DeadDefs);
989 if (!DeadDefs.empty()) {
990 // If the virtual SrcReg is completely eliminated, update all DBG_VALUEs
991 // to describe DstReg instead.
992 for (MachineOperand &UseMO : MRI->use_operands(SrcReg)) {
993 MachineInstr *UseMI = UseMO.getParent();
994 if (UseMI->isDebugValue()) {
995 UseMO.setReg(DstReg);
996 DEBUG(dbgs() << "\t\tupdated: " << *UseMI);
1005 bool RegisterCoalescer::eliminateUndefCopy(MachineInstr *CopyMI) {
1006 // ProcessImpicitDefs may leave some copies of <undef> values, it only removes
1007 // local variables. When we have a copy like:
1009 // %vreg1 = COPY %vreg2<undef>
1011 // We delete the copy and remove the corresponding value number from %vreg1.
1012 // Any uses of that value number are marked as <undef>.
1014 // Note that we do not query CoalescerPair here but redo isMoveInstr as the
1015 // CoalescerPair may have a new register class with adjusted subreg indices
1017 unsigned SrcReg, DstReg, SrcSubIdx, DstSubIdx;
1018 isMoveInstr(*TRI, CopyMI, SrcReg, DstReg, SrcSubIdx, DstSubIdx);
1020 SlotIndex Idx = LIS->getInstructionIndex(CopyMI);
1021 const LiveInterval &SrcLI = LIS->getInterval(SrcReg);
1022 // CopyMI is undef iff SrcReg is not live before the instruction.
1023 if (SrcSubIdx != 0 && SrcLI.hasSubRanges()) {
1024 unsigned SrcMask = TRI->getSubRegIndexLaneMask(SrcSubIdx);
1025 for (const LiveInterval::SubRange &SR : SrcLI.subranges()) {
1026 if ((SR.LaneMask & SrcMask) == 0)
1031 } else if (SrcLI.liveAt(Idx))
1034 DEBUG(dbgs() << "\tEliminating copy of <undef> value\n");
1036 // Remove any DstReg segments starting at the instruction.
1037 LiveInterval &DstLI = LIS->getInterval(DstReg);
1038 SlotIndex RegIndex = Idx.getRegSlot();
1039 // Remove value or merge with previous one in case of a subregister def.
1040 if (VNInfo *PrevVNI = DstLI.getVNInfoAt(Idx)) {
1041 VNInfo *VNI = DstLI.getVNInfoAt(RegIndex);
1042 DstLI.MergeValueNumberInto(VNI, PrevVNI);
1044 // The affected subregister segments can be removed.
1045 unsigned DstMask = TRI->getSubRegIndexLaneMask(DstSubIdx);
1046 for (LiveInterval::SubRange &SR : DstLI.subranges()) {
1047 if ((SR.LaneMask & DstMask) == 0)
1050 VNInfo *SVNI = SR.getVNInfoAt(RegIndex);
1051 assert(SVNI != nullptr && SlotIndex::isSameInstr(SVNI->def, RegIndex));
1052 SR.removeValNo(SVNI);
1054 DstLI.removeEmptySubRanges();
1056 LIS->removeVRegDefAt(DstLI, RegIndex);
1058 // Mark uses as undef.
1059 for (MachineOperand &MO : MRI->reg_nodbg_operands(DstReg)) {
1060 if (MO.isDef() /*|| MO.isUndef()*/)
1062 const MachineInstr &MI = *MO.getParent();
1063 SlotIndex UseIdx = LIS->getInstructionIndex(&MI);
1064 unsigned UseMask = TRI->getSubRegIndexLaneMask(MO.getSubReg());
1066 if (UseMask != ~0u && DstLI.hasSubRanges()) {
1068 for (const LiveInterval::SubRange &SR : DstLI.subranges()) {
1069 if ((SR.LaneMask & UseMask) == 0)
1071 if (SR.liveAt(UseIdx)) {
1077 isLive = DstLI.liveAt(UseIdx);
1080 MO.setIsUndef(true);
1081 DEBUG(dbgs() << "\tnew undef: " << UseIdx << '\t' << MI);
1086 void RegisterCoalescer::updateRegDefsUses(unsigned SrcReg,
1089 bool DstIsPhys = TargetRegisterInfo::isPhysicalRegister(DstReg);
1090 LiveInterval *DstInt = DstIsPhys ? nullptr : &LIS->getInterval(DstReg);
1092 SmallPtrSet<MachineInstr*, 8> Visited;
1093 for (MachineRegisterInfo::reg_instr_iterator
1094 I = MRI->reg_instr_begin(SrcReg), E = MRI->reg_instr_end();
1096 MachineInstr *UseMI = &*(I++);
1098 // Each instruction can only be rewritten once because sub-register
1099 // composition is not always idempotent. When SrcReg != DstReg, rewriting
1100 // the UseMI operands removes them from the SrcReg use-def chain, but when
1101 // SrcReg is DstReg we could encounter UseMI twice if it has multiple
1102 // operands mentioning the virtual register.
1103 if (SrcReg == DstReg && !Visited.insert(UseMI).second)
1106 SmallVector<unsigned,8> Ops;
1108 std::tie(Reads, Writes) = UseMI->readsWritesVirtualRegister(SrcReg, &Ops);
1110 // If SrcReg wasn't read, it may still be the case that DstReg is live-in
1111 // because SrcReg is a sub-register.
1112 if (DstInt && !Reads && SubIdx)
1113 Reads = DstInt->liveAt(LIS->getInstructionIndex(UseMI));
1115 // Replace SrcReg with DstReg in all UseMI operands.
1116 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
1117 MachineOperand &MO = UseMI->getOperand(Ops[i]);
1119 // Adjust <undef> flags in case of sub-register joins. We don't want to
1120 // turn a full def into a read-modify-write sub-register def and vice
1122 if (SubIdx && MO.isDef())
1123 MO.setIsUndef(!Reads);
1125 // A subreg use of a partially undef (super) register may be a complete
1126 // undef use now and then has to be marked that way.
1127 if (SubIdx != 0 && MO.isUse() && MRI->tracksSubRegLiveness()) {
1128 if (!DstInt->hasSubRanges()) {
1129 BumpPtrAllocator &Allocator = LIS->getVNInfoAllocator();
1130 unsigned Mask = MRI->getMaxLaneMaskForVReg(DstInt->reg);
1131 DstInt->createSubRangeFrom(Allocator, Mask, *DstInt);
1133 unsigned Mask = TRI->getSubRegIndexLaneMask(SubIdx);
1134 bool IsUndef = true;
1135 SlotIndex MIIdx = UseMI->isDebugValue()
1136 ? LIS->getSlotIndexes()->getIndexBefore(UseMI)
1137 : LIS->getInstructionIndex(UseMI);
1138 SlotIndex UseIdx = MIIdx.getRegSlot(true);
1139 for (LiveInterval::SubRange &S : DstInt->subranges()) {
1140 if ((S.LaneMask & Mask) == 0)
1142 if (S.liveAt(UseIdx)) {
1148 MO.setIsUndef(true);
1149 // We found out some subregister use is actually reading an undefined
1150 // value. In some cases the whole vreg has become undefined at this
1151 // point so we have to potentially shrink the main range if the
1152 // use was ending a live segment there.
1153 LiveQueryResult Q = DstInt->Query(MIIdx);
1154 if (Q.valueOut() == nullptr)
1155 ShrinkMainRange = true;
1160 MO.substPhysReg(DstReg, *TRI);
1162 MO.substVirtReg(DstReg, SubIdx, *TRI);
1166 dbgs() << "\t\tupdated: ";
1167 if (!UseMI->isDebugValue())
1168 dbgs() << LIS->getInstructionIndex(UseMI) << "\t";
1174 bool RegisterCoalescer::canJoinPhys(const CoalescerPair &CP) {
1175 // Always join simple intervals that are defined by a single copy from a
1176 // reserved register. This doesn't increase register pressure, so it is
1177 // always beneficial.
1178 if (!MRI->isReserved(CP.getDstReg())) {
1179 DEBUG(dbgs() << "\tCan only merge into reserved registers.\n");
1183 LiveInterval &JoinVInt = LIS->getInterval(CP.getSrcReg());
1184 if (JoinVInt.containsOneValue())
1187 DEBUG(dbgs() << "\tCannot join complex intervals into reserved register.\n");
1191 bool RegisterCoalescer::joinCopy(MachineInstr *CopyMI, bool &Again) {
1194 DEBUG(dbgs() << LIS->getInstructionIndex(CopyMI) << '\t' << *CopyMI);
1196 CoalescerPair CP(*TRI);
1197 if (!CP.setRegisters(CopyMI)) {
1198 DEBUG(dbgs() << "\tNot coalescable.\n");
1202 if (CP.getNewRC()) {
1203 auto SrcRC = MRI->getRegClass(CP.getSrcReg());
1204 auto DstRC = MRI->getRegClass(CP.getDstReg());
1205 unsigned SrcIdx = CP.getSrcIdx();
1206 unsigned DstIdx = CP.getDstIdx();
1207 if (CP.isFlipped()) {
1208 std::swap(SrcIdx, DstIdx);
1209 std::swap(SrcRC, DstRC);
1211 if (!TRI->shouldCoalesce(CopyMI, SrcRC, SrcIdx, DstRC, DstIdx,
1213 DEBUG(dbgs() << "\tSubtarget bailed on coalescing.\n");
1218 // Dead code elimination. This really should be handled by MachineDCE, but
1219 // sometimes dead copies slip through, and we can't generate invalid live
1221 if (!CP.isPhys() && CopyMI->allDefsAreDead()) {
1222 DEBUG(dbgs() << "\tCopy is dead.\n");
1223 DeadDefs.push_back(CopyMI);
1224 eliminateDeadDefs();
1228 // Eliminate undefs.
1229 if (!CP.isPhys() && eliminateUndefCopy(CopyMI)) {
1230 LIS->RemoveMachineInstrFromMaps(CopyMI);
1231 CopyMI->eraseFromParent();
1232 return false; // Not coalescable.
1235 // Coalesced copies are normally removed immediately, but transformations
1236 // like removeCopyByCommutingDef() can inadvertently create identity copies.
1237 // When that happens, just join the values and remove the copy.
1238 if (CP.getSrcReg() == CP.getDstReg()) {
1239 LiveInterval &LI = LIS->getInterval(CP.getSrcReg());
1240 DEBUG(dbgs() << "\tCopy already coalesced: " << LI << '\n');
1241 const SlotIndex CopyIdx = LIS->getInstructionIndex(CopyMI);
1242 LiveQueryResult LRQ = LI.Query(CopyIdx);
1243 if (VNInfo *DefVNI = LRQ.valueDefined()) {
1244 VNInfo *ReadVNI = LRQ.valueIn();
1245 assert(ReadVNI && "No value before copy and no <undef> flag.");
1246 assert(ReadVNI != DefVNI && "Cannot read and define the same value.");
1247 LI.MergeValueNumberInto(DefVNI, ReadVNI);
1249 // Process subregister liveranges.
1250 for (LiveInterval::SubRange &S : LI.subranges()) {
1251 LiveQueryResult SLRQ = S.Query(CopyIdx);
1252 if (VNInfo *SDefVNI = SLRQ.valueDefined()) {
1253 VNInfo *SReadVNI = SLRQ.valueIn();
1254 S.MergeValueNumberInto(SDefVNI, SReadVNI);
1257 DEBUG(dbgs() << "\tMerged values: " << LI << '\n');
1259 LIS->RemoveMachineInstrFromMaps(CopyMI);
1260 CopyMI->eraseFromParent();
1264 // Enforce policies.
1266 DEBUG(dbgs() << "\tConsidering merging " << PrintReg(CP.getSrcReg(), TRI)
1267 << " with " << PrintReg(CP.getDstReg(), TRI, CP.getSrcIdx())
1269 if (!canJoinPhys(CP)) {
1270 // Before giving up coalescing, if definition of source is defined by
1271 // trivial computation, try rematerializing it.
1273 if (reMaterializeTrivialDef(CP, CopyMI, IsDefCopy))
1276 Again = true; // May be possible to coalesce later.
1280 // When possible, let DstReg be the larger interval.
1281 if (!CP.isPartial() && LIS->getInterval(CP.getSrcReg()).size() >
1282 LIS->getInterval(CP.getDstReg()).size())
1286 dbgs() << "\tConsidering merging to "
1287 << TRI->getRegClassName(CP.getNewRC()) << " with ";
1288 if (CP.getDstIdx() && CP.getSrcIdx())
1289 dbgs() << PrintReg(CP.getDstReg()) << " in "
1290 << TRI->getSubRegIndexName(CP.getDstIdx()) << " and "
1291 << PrintReg(CP.getSrcReg()) << " in "
1292 << TRI->getSubRegIndexName(CP.getSrcIdx()) << '\n';
1294 dbgs() << PrintReg(CP.getSrcReg(), TRI) << " in "
1295 << PrintReg(CP.getDstReg(), TRI, CP.getSrcIdx()) << '\n';
1300 ShrinkMainRange = false;
1302 // Okay, attempt to join these two intervals. On failure, this returns false.
1303 // Otherwise, if one of the intervals being joined is a physreg, this method
1304 // always canonicalizes DstInt to be it. The output "SrcInt" will not have
1305 // been modified, so we can use this information below to update aliases.
1306 if (!joinIntervals(CP)) {
1307 // Coalescing failed.
1309 // If definition of source is defined by trivial computation, try
1310 // rematerializing it.
1312 if (reMaterializeTrivialDef(CP, CopyMI, IsDefCopy))
1315 // If we can eliminate the copy without merging the live segments, do so
1317 if (!CP.isPartial() && !CP.isPhys()) {
1318 if (adjustCopiesBackFrom(CP, CopyMI) ||
1319 removeCopyByCommutingDef(CP, CopyMI)) {
1320 LIS->RemoveMachineInstrFromMaps(CopyMI);
1321 CopyMI->eraseFromParent();
1322 DEBUG(dbgs() << "\tTrivial!\n");
1327 // Otherwise, we are unable to join the intervals.
1328 DEBUG(dbgs() << "\tInterference!\n");
1329 Again = true; // May be possible to coalesce later.
1333 // Coalescing to a virtual register that is of a sub-register class of the
1334 // other. Make sure the resulting register is set to the right register class.
1335 if (CP.isCrossClass()) {
1337 MRI->setRegClass(CP.getDstReg(), CP.getNewRC());
1340 // Removing sub-register copies can ease the register class constraints.
1341 // Make sure we attempt to inflate the register class of DstReg.
1342 if (!CP.isPhys() && RegClassInfo.isProperSubClass(CP.getNewRC()))
1343 InflateRegs.push_back(CP.getDstReg());
1345 // CopyMI has been erased by joinIntervals at this point. Remove it from
1346 // ErasedInstrs since copyCoalesceWorkList() won't add a successful join back
1347 // to the work list. This keeps ErasedInstrs from growing needlessly.
1348 ErasedInstrs.erase(CopyMI);
1350 // Rewrite all SrcReg operands to DstReg.
1351 // Also update DstReg operands to include DstIdx if it is set.
1353 updateRegDefsUses(CP.getDstReg(), CP.getDstReg(), CP.getDstIdx());
1354 updateRegDefsUses(CP.getSrcReg(), CP.getDstReg(), CP.getSrcIdx());
1356 // Shrink subregister ranges if necessary.
1357 if (ShrinkMask != 0) {
1358 LiveInterval &LI = LIS->getInterval(CP.getDstReg());
1359 for (LiveInterval::SubRange &S : LI.subranges()) {
1360 if ((S.LaneMask & ShrinkMask) == 0)
1362 DEBUG(dbgs() << "Shrink LaneUses (Lane "
1363 << format("%04X", S.LaneMask) << ")\n");
1364 LIS->shrinkToUses(S, LI.reg);
1367 if (ShrinkMainRange) {
1368 LiveInterval &LI = LIS->getInterval(CP.getDstReg());
1369 LIS->shrinkToUses(&LI);
1372 // SrcReg is guaranteed to be the register whose live interval that is
1374 LIS->removeInterval(CP.getSrcReg());
1376 // Update regalloc hint.
1377 TRI->UpdateRegAllocHint(CP.getSrcReg(), CP.getDstReg(), *MF);
1380 dbgs() << "\tSuccess: " << PrintReg(CP.getSrcReg(), TRI, CP.getSrcIdx())
1381 << " -> " << PrintReg(CP.getDstReg(), TRI, CP.getDstIdx()) << '\n';
1382 dbgs() << "\tResult = ";
1384 dbgs() << PrintReg(CP.getDstReg(), TRI);
1386 dbgs() << LIS->getInterval(CP.getDstReg());
1394 bool RegisterCoalescer::joinReservedPhysReg(CoalescerPair &CP) {
1395 unsigned DstReg = CP.getDstReg();
1396 assert(CP.isPhys() && "Must be a physreg copy");
1397 assert(MRI->isReserved(DstReg) && "Not a reserved register");
1398 LiveInterval &RHS = LIS->getInterval(CP.getSrcReg());
1399 DEBUG(dbgs() << "\t\tRHS = " << RHS << '\n');
1401 assert(RHS.containsOneValue() && "Invalid join with reserved register");
1403 // Optimization for reserved registers like ESP. We can only merge with a
1404 // reserved physreg if RHS has a single value that is a copy of DstReg.
1405 // The live range of the reserved register will look like a set of dead defs
1406 // - we don't properly track the live range of reserved registers.
1408 // Deny any overlapping intervals. This depends on all the reserved
1409 // register live ranges to look like dead defs.
1410 for (MCRegUnitIterator UI(DstReg, TRI); UI.isValid(); ++UI)
1411 if (RHS.overlaps(LIS->getRegUnit(*UI))) {
1412 DEBUG(dbgs() << "\t\tInterference: " << PrintRegUnit(*UI, TRI) << '\n');
1416 // Skip any value computations, we are not adding new values to the
1417 // reserved register. Also skip merging the live ranges, the reserved
1418 // register live range doesn't need to be accurate as long as all the
1421 // Delete the identity copy.
1422 MachineInstr *CopyMI;
1423 if (CP.isFlipped()) {
1424 CopyMI = MRI->getVRegDef(RHS.reg);
1426 if (!MRI->hasOneNonDBGUse(RHS.reg)) {
1427 DEBUG(dbgs() << "\t\tMultiple vreg uses!\n");
1431 MachineInstr *DestMI = MRI->getVRegDef(RHS.reg);
1432 CopyMI = &*MRI->use_instr_nodbg_begin(RHS.reg);
1433 const SlotIndex CopyRegIdx = LIS->getInstructionIndex(CopyMI).getRegSlot();
1434 const SlotIndex DestRegIdx = LIS->getInstructionIndex(DestMI).getRegSlot();
1436 // We checked above that there are no interfering defs of the physical
1437 // register. However, for this case, where we intent to move up the def of
1438 // the physical register, we also need to check for interfering uses.
1439 SlotIndexes *Indexes = LIS->getSlotIndexes();
1440 for (SlotIndex SI = Indexes->getNextNonNullIndex(DestRegIdx);
1441 SI != CopyRegIdx; SI = Indexes->getNextNonNullIndex(SI)) {
1442 MachineInstr *MI = LIS->getInstructionFromIndex(SI);
1443 if (MI->readsRegister(DstReg, TRI)) {
1444 DEBUG(dbgs() << "\t\tInterference (read): " << *MI);
1449 // We're going to remove the copy which defines a physical reserved
1450 // register, so remove its valno, etc.
1451 DEBUG(dbgs() << "\t\tRemoving phys reg def of " << DstReg << " at "
1452 << CopyRegIdx << "\n");
1454 LIS->removePhysRegDefAt(DstReg, CopyRegIdx);
1455 // Create a new dead def at the new def location.
1456 for (MCRegUnitIterator UI(DstReg, TRI); UI.isValid(); ++UI) {
1457 LiveRange &LR = LIS->getRegUnit(*UI);
1458 LR.createDeadDef(DestRegIdx, LIS->getVNInfoAllocator());
1462 LIS->RemoveMachineInstrFromMaps(CopyMI);
1463 CopyMI->eraseFromParent();
1465 // We don't track kills for reserved registers.
1466 MRI->clearKillFlags(CP.getSrcReg());
1471 //===----------------------------------------------------------------------===//
1472 // Interference checking and interval joining
1473 //===----------------------------------------------------------------------===//
1475 // In the easiest case, the two live ranges being joined are disjoint, and
1476 // there is no interference to consider. It is quite common, though, to have
1477 // overlapping live ranges, and we need to check if the interference can be
1480 // The live range of a single SSA value forms a sub-tree of the dominator tree.
1481 // This means that two SSA values overlap if and only if the def of one value
1482 // is contained in the live range of the other value. As a special case, the
1483 // overlapping values can be defined at the same index.
1485 // The interference from an overlapping def can be resolved in these cases:
1487 // 1. Coalescable copies. The value is defined by a copy that would become an
1488 // identity copy after joining SrcReg and DstReg. The copy instruction will
1489 // be removed, and the value will be merged with the source value.
1491 // There can be several copies back and forth, causing many values to be
1492 // merged into one. We compute a list of ultimate values in the joined live
1493 // range as well as a mappings from the old value numbers.
1495 // 2. IMPLICIT_DEF. This instruction is only inserted to ensure all PHI
1496 // predecessors have a live out value. It doesn't cause real interference,
1497 // and can be merged into the value it overlaps. Like a coalescable copy, it
1498 // can be erased after joining.
1500 // 3. Copy of external value. The overlapping def may be a copy of a value that
1501 // is already in the other register. This is like a coalescable copy, but
1502 // the live range of the source register must be trimmed after erasing the
1503 // copy instruction:
1506 // %dst = COPY %ext <-- Remove this COPY, trim the live range of %ext.
1508 // 4. Clobbering undefined lanes. Vector registers are sometimes built by
1509 // defining one lane at a time:
1511 // %dst:ssub0<def,read-undef> = FOO
1513 // %dst:ssub1<def> = COPY %src
1515 // The live range of %src overlaps the %dst value defined by FOO, but
1516 // merging %src into %dst:ssub1 is only going to clobber the ssub1 lane
1517 // which was undef anyway.
1519 // The value mapping is more complicated in this case. The final live range
1520 // will have different value numbers for both FOO and BAR, but there is no
1521 // simple mapping from old to new values. It may even be necessary to add
1524 // 5. Clobbering dead lanes. A def may clobber a lane of a vector register that
1525 // is live, but never read. This can happen because we don't compute
1526 // individual live ranges per lane.
1530 // %dst:ssub1<def> = COPY %src
1532 // This kind of interference is only resolved locally. If the clobbered
1533 // lane value escapes the block, the join is aborted.
1536 /// Track information about values in a single virtual register about to be
1537 /// joined. Objects of this class are always created in pairs - one for each
1538 /// side of the CoalescerPair (or one for each lane of a side of the coalescer
1541 /// Live range we work on.
1543 /// (Main) register we work on.
1546 /// Reg (and therefore the values in this liverange) will end up as
1547 /// subregister SubIdx in the coalesced register. Either CP.DstIdx or
1549 const unsigned SubIdx;
1550 /// The LaneMask that this liverange will occupy the coalesced register. May
1551 /// be smaller than the lanemask produced by SubIdx when merging subranges.
1552 const unsigned LaneMask;
1554 /// This is true when joining sub register ranges, false when joining main
1556 const bool SubRangeJoin;
1557 /// Whether the current LiveInterval tracks subregister liveness.
1558 const bool TrackSubRegLiveness;
1560 /// Values that will be present in the final live range.
1561 SmallVectorImpl<VNInfo*> &NewVNInfo;
1563 const CoalescerPair &CP;
1565 SlotIndexes *Indexes;
1566 const TargetRegisterInfo *TRI;
1568 /// Value number assignments. Maps value numbers in LI to entries in
1569 /// NewVNInfo. This is suitable for passing to LiveInterval::join().
1570 SmallVector<int, 8> Assignments;
1572 /// Conflict resolution for overlapping values.
1573 enum ConflictResolution {
1574 /// No overlap, simply keep this value.
1577 /// Merge this value into OtherVNI and erase the defining instruction.
1578 /// Used for IMPLICIT_DEF, coalescable copies, and copies from external
1582 /// Merge this value into OtherVNI but keep the defining instruction.
1583 /// This is for the special case where OtherVNI is defined by the same
1587 /// Keep this value, and have it replace OtherVNI where possible. This
1588 /// complicates value mapping since OtherVNI maps to two different values
1589 /// before and after this def.
1590 /// Used when clobbering undefined or dead lanes.
1593 /// Unresolved conflict. Visit later when all values have been mapped.
1596 /// Unresolvable conflict. Abort the join.
1600 /// Per-value info for LI. The lane bit masks are all relative to the final
1601 /// joined register, so they can be compared directly between SrcReg and
1604 ConflictResolution Resolution;
1606 /// Lanes written by this def, 0 for unanalyzed values.
1607 unsigned WriteLanes;
1609 /// Lanes with defined values in this register. Other lanes are undef and
1610 /// safe to clobber.
1611 unsigned ValidLanes;
1613 /// Value in LI being redefined by this def.
1616 /// Value in the other live range that overlaps this def, if any.
1619 /// Is this value an IMPLICIT_DEF that can be erased?
1621 /// IMPLICIT_DEF values should only exist at the end of a basic block that
1622 /// is a predecessor to a phi-value. These IMPLICIT_DEF instructions can be
1623 /// safely erased if they are overlapping a live value in the other live
1626 /// Weird control flow graphs and incomplete PHI handling in
1627 /// ProcessImplicitDefs can very rarely create IMPLICIT_DEF values with
1628 /// longer live ranges. Such IMPLICIT_DEF values should be treated like
1630 bool ErasableImplicitDef;
1632 /// True when the live range of this value will be pruned because of an
1633 /// overlapping CR_Replace value in the other live range.
1636 /// True once Pruned above has been computed.
1637 bool PrunedComputed;
1639 Val() : Resolution(CR_Keep), WriteLanes(0), ValidLanes(0),
1640 RedefVNI(nullptr), OtherVNI(nullptr), ErasableImplicitDef(false),
1641 Pruned(false), PrunedComputed(false) {}
1643 bool isAnalyzed() const { return WriteLanes != 0; }
1646 /// One entry per value number in LI.
1647 SmallVector<Val, 8> Vals;
1649 /// Compute the bitmask of lanes actually written by DefMI.
1650 /// Set Redef if there are any partial register definitions that depend on the
1651 /// previous value of the register.
1652 unsigned computeWriteLanes(const MachineInstr *DefMI, bool &Redef) const;
1654 /// Find the ultimate value that VNI was copied from.
1655 std::pair<const VNInfo*,unsigned> followCopyChain(const VNInfo *VNI) const;
1657 bool valuesIdentical(VNInfo *Val0, VNInfo *Val1, const JoinVals &Other) const;
1659 /// Analyze ValNo in this live range, and set all fields of Vals[ValNo].
1660 /// Return a conflict resolution when possible, but leave the hard cases as
1662 /// Recursively calls computeAssignment() on this and Other, guaranteeing that
1663 /// both OtherVNI and RedefVNI have been analyzed and mapped before returning.
1664 /// The recursion always goes upwards in the dominator tree, making loops
1666 ConflictResolution analyzeValue(unsigned ValNo, JoinVals &Other);
1668 /// Compute the value assignment for ValNo in RI.
1669 /// This may be called recursively by analyzeValue(), but never for a ValNo on
1671 void computeAssignment(unsigned ValNo, JoinVals &Other);
1673 /// Assuming ValNo is going to clobber some valid lanes in Other.LR, compute
1674 /// the extent of the tainted lanes in the block.
1676 /// Multiple values in Other.LR can be affected since partial redefinitions
1677 /// can preserve previously tainted lanes.
1679 /// 1 %dst = VLOAD <-- Define all lanes in %dst
1680 /// 2 %src = FOO <-- ValNo to be joined with %dst:ssub0
1681 /// 3 %dst:ssub1 = BAR <-- Partial redef doesn't clear taint in ssub0
1682 /// 4 %dst:ssub0 = COPY %src <-- Conflict resolved, ssub0 wasn't read
1684 /// For each ValNo in Other that is affected, add an (EndIndex, TaintedLanes)
1685 /// entry to TaintedVals.
1687 /// Returns false if the tainted lanes extend beyond the basic block.
1688 bool taintExtent(unsigned, unsigned, JoinVals&,
1689 SmallVectorImpl<std::pair<SlotIndex, unsigned> >&);
1691 /// Return true if MI uses any of the given Lanes from Reg.
1692 /// This does not include partial redefinitions of Reg.
1693 bool usesLanes(const MachineInstr *MI, unsigned, unsigned, unsigned) const;
1695 /// Determine if ValNo is a copy of a value number in LR or Other.LR that will
1698 /// %dst = COPY %src
1699 /// %src = COPY %dst <-- This value to be pruned.
1700 /// %dst = COPY %src <-- This value is a copy of a pruned value.
1701 bool isPrunedValue(unsigned ValNo, JoinVals &Other);
1704 JoinVals(LiveRange &LR, unsigned Reg, unsigned SubIdx, unsigned LaneMask,
1705 SmallVectorImpl<VNInfo*> &newVNInfo, const CoalescerPair &cp,
1706 LiveIntervals *lis, const TargetRegisterInfo *TRI, bool SubRangeJoin,
1707 bool TrackSubRegLiveness)
1708 : LR(LR), Reg(Reg), SubIdx(SubIdx), LaneMask(LaneMask),
1709 SubRangeJoin(SubRangeJoin), TrackSubRegLiveness(TrackSubRegLiveness),
1710 NewVNInfo(newVNInfo), CP(cp), LIS(lis), Indexes(LIS->getSlotIndexes()),
1711 TRI(TRI), Assignments(LR.getNumValNums(), -1), Vals(LR.getNumValNums())
1714 /// Analyze defs in LR and compute a value mapping in NewVNInfo.
1715 /// Returns false if any conflicts were impossible to resolve.
1716 bool mapValues(JoinVals &Other);
1718 /// Try to resolve conflicts that require all values to be mapped.
1719 /// Returns false if any conflicts were impossible to resolve.
1720 bool resolveConflicts(JoinVals &Other);
1722 /// Prune the live range of values in Other.LR where they would conflict with
1723 /// CR_Replace values in LR. Collect end points for restoring the live range
1725 void pruneValues(JoinVals &Other, SmallVectorImpl<SlotIndex> &EndPoints,
1728 /// Removes subranges starting at copies that get removed. This sometimes
1729 /// happens when undefined subranges are copied around. These ranges contain
1730 /// no usefull information and can be removed.
1731 void pruneSubRegValues(LiveInterval &LI, unsigned &ShrinkMask);
1733 /// Erase any machine instructions that have been coalesced away.
1734 /// Add erased instructions to ErasedInstrs.
1735 /// Add foreign virtual registers to ShrinkRegs if their live range ended at
1736 /// the erased instrs.
1737 void eraseInstrs(SmallPtrSetImpl<MachineInstr*> &ErasedInstrs,
1738 SmallVectorImpl<unsigned> &ShrinkRegs);
1740 /// Get the value assignments suitable for passing to LiveInterval::join.
1741 const int *getAssignments() const { return Assignments.data(); }
1743 } // end anonymous namespace
1745 unsigned JoinVals::computeWriteLanes(const MachineInstr *DefMI, bool &Redef)
1748 for (ConstMIOperands MO(DefMI); MO.isValid(); ++MO) {
1749 if (!MO->isReg() || MO->getReg() != Reg || !MO->isDef())
1751 L |= TRI->getSubRegIndexLaneMask(
1752 TRI->composeSubRegIndices(SubIdx, MO->getSubReg()));
1759 std::pair<const VNInfo*, unsigned> JoinVals::followCopyChain(
1760 const VNInfo *VNI) const {
1761 unsigned Reg = this->Reg;
1763 while (!VNI->isPHIDef()) {
1764 SlotIndex Def = VNI->def;
1765 MachineInstr *MI = Indexes->getInstructionFromIndex(Def);
1766 assert(MI && "No defining instruction");
1767 if (!MI->isFullCopy())
1768 return std::make_pair(VNI, Reg);
1769 unsigned SrcReg = MI->getOperand(1).getReg();
1770 if (!TargetRegisterInfo::isVirtualRegister(SrcReg))
1771 return std::make_pair(VNI, Reg);
1773 const LiveInterval &LI = LIS->getInterval(SrcReg);
1774 const VNInfo *ValueIn;
1775 // No subrange involved.
1776 if (!SubRangeJoin || !LI.hasSubRanges()) {
1777 LiveQueryResult LRQ = LI.Query(Def);
1778 ValueIn = LRQ.valueIn();
1780 // Query subranges. Pick the first matching one.
1782 for (const LiveInterval::SubRange &S : LI.subranges()) {
1783 // Transform lanemask to a mask in the joined live interval.
1784 unsigned SMask = TRI->composeSubRegIndexLaneMask(SubIdx, S.LaneMask);
1785 if ((SMask & LaneMask) == 0)
1787 LiveQueryResult LRQ = S.Query(Def);
1788 ValueIn = LRQ.valueIn();
1792 if (ValueIn == nullptr)
1797 return std::make_pair(VNI, Reg);
1800 bool JoinVals::valuesIdentical(VNInfo *Value0, VNInfo *Value1,
1801 const JoinVals &Other) const {
1802 const VNInfo *Orig0;
1804 std::tie(Orig0, Reg0) = followCopyChain(Value0);
1805 if (Orig0 == Value1)
1808 const VNInfo *Orig1;
1810 std::tie(Orig1, Reg1) = Other.followCopyChain(Value1);
1812 // The values are equal if they are defined at the same place and use the
1813 // same register. Note that we cannot compare VNInfos directly as some of
1814 // them might be from a copy created in mergeSubRangeInto() while the other
1815 // is from the original LiveInterval.
1816 return Orig0->def == Orig1->def && Reg0 == Reg1;
1819 JoinVals::ConflictResolution
1820 JoinVals::analyzeValue(unsigned ValNo, JoinVals &Other) {
1821 Val &V = Vals[ValNo];
1822 assert(!V.isAnalyzed() && "Value has already been analyzed!");
1823 VNInfo *VNI = LR.getValNumInfo(ValNo);
1824 if (VNI->isUnused()) {
1829 // Get the instruction defining this value, compute the lanes written.
1830 const MachineInstr *DefMI = nullptr;
1831 if (VNI->isPHIDef()) {
1832 // Conservatively assume that all lanes in a PHI are valid.
1833 unsigned Lanes = SubRangeJoin ? 1 : TRI->getSubRegIndexLaneMask(SubIdx);
1834 V.ValidLanes = V.WriteLanes = Lanes;
1836 DefMI = Indexes->getInstructionFromIndex(VNI->def);
1837 assert(DefMI != nullptr);
1839 // We don't care about the lanes when joining subregister ranges.
1840 V.ValidLanes = V.WriteLanes = 1;
1843 V.ValidLanes = V.WriteLanes = computeWriteLanes(DefMI, Redef);
1845 // If this is a read-modify-write instruction, there may be more valid
1846 // lanes than the ones written by this instruction.
1847 // This only covers partial redef operands. DefMI may have normal use
1848 // operands reading the register. They don't contribute valid lanes.
1850 // This adds ssub1 to the set of valid lanes in %src:
1852 // %src:ssub1<def> = FOO
1854 // This leaves only ssub1 valid, making any other lanes undef:
1856 // %src:ssub1<def,read-undef> = FOO %src:ssub2
1858 // The <read-undef> flag on the def operand means that old lane values are
1861 V.RedefVNI = LR.Query(VNI->def).valueIn();
1862 assert((TrackSubRegLiveness || V.RedefVNI) &&
1863 "Instruction is reading nonexistent value");
1864 if (V.RedefVNI != nullptr) {
1865 computeAssignment(V.RedefVNI->id, Other);
1866 V.ValidLanes |= Vals[V.RedefVNI->id].ValidLanes;
1870 // An IMPLICIT_DEF writes undef values.
1871 if (DefMI->isImplicitDef()) {
1872 // We normally expect IMPLICIT_DEF values to be live only until the end
1873 // of their block. If the value is really live longer and gets pruned in
1874 // another block, this flag is cleared again.
1875 V.ErasableImplicitDef = true;
1876 V.ValidLanes &= ~V.WriteLanes;
1881 // Find the value in Other that overlaps VNI->def, if any.
1882 LiveQueryResult OtherLRQ = Other.LR.Query(VNI->def);
1884 // It is possible that both values are defined by the same instruction, or
1885 // the values are PHIs defined in the same block. When that happens, the two
1886 // values should be merged into one, but not into any preceding value.
1887 // The first value defined or visited gets CR_Keep, the other gets CR_Merge.
1888 if (VNInfo *OtherVNI = OtherLRQ.valueDefined()) {
1889 assert(SlotIndex::isSameInstr(VNI->def, OtherVNI->def) && "Broken LRQ");
1891 // One value stays, the other is merged. Keep the earlier one, or the first
1893 if (OtherVNI->def < VNI->def)
1894 Other.computeAssignment(OtherVNI->id, *this);
1895 else if (VNI->def < OtherVNI->def && OtherLRQ.valueIn()) {
1896 // This is an early-clobber def overlapping a live-in value in the other
1897 // register. Not mergeable.
1898 V.OtherVNI = OtherLRQ.valueIn();
1899 return CR_Impossible;
1901 V.OtherVNI = OtherVNI;
1902 Val &OtherV = Other.Vals[OtherVNI->id];
1903 // Keep this value, check for conflicts when analyzing OtherVNI.
1904 if (!OtherV.isAnalyzed())
1906 // Both sides have been analyzed now.
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())
1911 if (V.ValidLanes & OtherV.ValidLanes)
1912 // Overlapping lanes can't be resolved.
1913 return CR_Impossible;
1918 // No simultaneous def. Is Other live at the def?
1919 V.OtherVNI = OtherLRQ.valueIn();
1921 // No overlap, no conflict.
1924 assert(!SlotIndex::isSameInstr(VNI->def, V.OtherVNI->def) && "Broken LRQ");
1926 // We have overlapping values, or possibly a kill of Other.
1927 // Recursively compute assignments up the dominator tree.
1928 Other.computeAssignment(V.OtherVNI->id, *this);
1929 Val &OtherV = Other.Vals[V.OtherVNI->id];
1931 // Check if OtherV is an IMPLICIT_DEF that extends beyond its basic block.
1932 // This shouldn't normally happen, but ProcessImplicitDefs can leave such
1933 // IMPLICIT_DEF instructions behind, and there is nothing wrong with it
1936 // WHen it happens, treat that IMPLICIT_DEF as a normal value, and don't try
1937 // to erase the IMPLICIT_DEF instruction.
1938 if (OtherV.ErasableImplicitDef && DefMI &&
1939 DefMI->getParent() != Indexes->getMBBFromIndex(V.OtherVNI->def)) {
1940 DEBUG(dbgs() << "IMPLICIT_DEF defined at " << V.OtherVNI->def
1941 << " extends into BB#" << DefMI->getParent()->getNumber()
1942 << ", keeping it.\n");
1943 OtherV.ErasableImplicitDef = false;
1946 // Allow overlapping PHI values. Any real interference would show up in a
1947 // predecessor, the PHI itself can't introduce any conflicts.
1948 if (VNI->isPHIDef())
1951 // Check for simple erasable conflicts.
1952 if (DefMI->isImplicitDef()) {
1953 // We need the def for the subregister if there is nothing else live at the
1954 // subrange at this point.
1955 if (TrackSubRegLiveness
1956 && (V.WriteLanes & (OtherV.ValidLanes | OtherV.WriteLanes)) == 0)
1961 // Include the non-conflict where DefMI is a coalescable copy that kills
1962 // OtherVNI. We still want the copy erased and value numbers merged.
1963 if (CP.isCoalescable(DefMI)) {
1964 // Some of the lanes copied from OtherVNI may be undef, making them undef
1966 V.ValidLanes &= ~V.WriteLanes | OtherV.ValidLanes;
1970 // This may not be a real conflict if DefMI simply kills Other and defines
1972 if (OtherLRQ.isKill() && OtherLRQ.endPoint() <= VNI->def)
1975 // Handle the case where VNI and OtherVNI can be proven to be identical:
1977 // %other = COPY %ext
1978 // %this = COPY %ext <-- Erase this copy
1980 if (DefMI->isFullCopy() && !CP.isPartial()
1981 && valuesIdentical(VNI, V.OtherVNI, Other))
1984 // If the lanes written by this instruction were all undef in OtherVNI, it is
1985 // still safe to join the live ranges. This can't be done with a simple value
1986 // mapping, though - OtherVNI will map to multiple values:
1988 // 1 %dst:ssub0 = FOO <-- OtherVNI
1989 // 2 %src = BAR <-- VNI
1990 // 3 %dst:ssub1 = COPY %src<kill> <-- Eliminate this copy.
1992 // 5 QUUX %src<kill>
1994 // Here OtherVNI will map to itself in [1;2), but to VNI in [2;5). CR_Replace
1995 // handles this complex value mapping.
1996 if ((V.WriteLanes & OtherV.ValidLanes) == 0)
1999 // If the other live range is killed by DefMI and the live ranges are still
2000 // overlapping, it must be because we're looking at an early clobber def:
2002 // %dst<def,early-clobber> = ASM %src<kill>
2004 // In this case, it is illegal to merge the two live ranges since the early
2005 // clobber def would clobber %src before it was read.
2006 if (OtherLRQ.isKill()) {
2007 // This case where the def doesn't overlap the kill is handled above.
2008 assert(VNI->def.isEarlyClobber() &&
2009 "Only early clobber defs can overlap a kill");
2010 return CR_Impossible;
2013 // VNI is clobbering live lanes in OtherVNI, but there is still the
2014 // possibility that no instructions actually read the clobbered lanes.
2015 // If we're clobbering all the lanes in OtherVNI, at least one must be read.
2016 // Otherwise Other.RI wouldn't be live here.
2017 if ((TRI->getSubRegIndexLaneMask(Other.SubIdx) & ~V.WriteLanes) == 0)
2018 return CR_Impossible;
2020 // We need to verify that no instructions are reading the clobbered lanes. To
2021 // save compile time, we'll only check that locally. Don't allow the tainted
2022 // value to escape the basic block.
2023 MachineBasicBlock *MBB = Indexes->getMBBFromIndex(VNI->def);
2024 if (OtherLRQ.endPoint() >= Indexes->getMBBEndIdx(MBB))
2025 return CR_Impossible;
2027 // There are still some things that could go wrong besides clobbered lanes
2028 // being read, for example OtherVNI may be only partially redefined in MBB,
2029 // and some clobbered lanes could escape the block. Save this analysis for
2030 // resolveConflicts() when all values have been mapped. We need to know
2031 // RedefVNI and WriteLanes for any later defs in MBB, and we can't compute
2032 // that now - the recursive analyzeValue() calls must go upwards in the
2034 return CR_Unresolved;
2037 void JoinVals::computeAssignment(unsigned ValNo, JoinVals &Other) {
2038 Val &V = Vals[ValNo];
2039 if (V.isAnalyzed()) {
2040 // Recursion should always move up the dominator tree, so ValNo is not
2041 // supposed to reappear before it has been assigned.
2042 assert(Assignments[ValNo] != -1 && "Bad recursion?");
2045 switch ((V.Resolution = analyzeValue(ValNo, Other))) {
2048 // Merge this ValNo into OtherVNI.
2049 assert(V.OtherVNI && "OtherVNI not assigned, can't merge.");
2050 assert(Other.Vals[V.OtherVNI->id].isAnalyzed() && "Missing recursion");
2051 Assignments[ValNo] = Other.Assignments[V.OtherVNI->id];
2052 DEBUG(dbgs() << "\t\tmerge " << PrintReg(Reg) << ':' << ValNo << '@'
2053 << LR.getValNumInfo(ValNo)->def << " into "
2054 << PrintReg(Other.Reg) << ':' << V.OtherVNI->id << '@'
2055 << V.OtherVNI->def << " --> @"
2056 << NewVNInfo[Assignments[ValNo]]->def << '\n');
2059 case CR_Unresolved: {
2060 // The other value is going to be pruned if this join is successful.
2061 assert(V.OtherVNI && "OtherVNI not assigned, can't prune");
2062 Val &OtherV = Other.Vals[V.OtherVNI->id];
2063 // We cannot erase an IMPLICIT_DEF if we don't have valid values for all
2065 if ((OtherV.WriteLanes & ~V.ValidLanes) != 0 && TrackSubRegLiveness)
2066 OtherV.ErasableImplicitDef = false;
2067 OtherV.Pruned = true;
2071 // This value number needs to go in the final joined live range.
2072 Assignments[ValNo] = NewVNInfo.size();
2073 NewVNInfo.push_back(LR.getValNumInfo(ValNo));
2078 bool JoinVals::mapValues(JoinVals &Other) {
2079 for (unsigned i = 0, e = LR.getNumValNums(); i != e; ++i) {
2080 computeAssignment(i, Other);
2081 if (Vals[i].Resolution == CR_Impossible) {
2082 DEBUG(dbgs() << "\t\tinterference at " << PrintReg(Reg) << ':' << i
2083 << '@' << LR.getValNumInfo(i)->def << '\n');
2091 taintExtent(unsigned ValNo, unsigned TaintedLanes, JoinVals &Other,
2092 SmallVectorImpl<std::pair<SlotIndex, unsigned> > &TaintExtent) {
2093 VNInfo *VNI = LR.getValNumInfo(ValNo);
2094 MachineBasicBlock *MBB = Indexes->getMBBFromIndex(VNI->def);
2095 SlotIndex MBBEnd = Indexes->getMBBEndIdx(MBB);
2097 // Scan Other.LR from VNI.def to MBBEnd.
2098 LiveInterval::iterator OtherI = Other.LR.find(VNI->def);
2099 assert(OtherI != Other.LR.end() && "No conflict?");
2101 // OtherI is pointing to a tainted value. Abort the join if the tainted
2102 // lanes escape the block.
2103 SlotIndex End = OtherI->end;
2104 if (End >= MBBEnd) {
2105 DEBUG(dbgs() << "\t\ttaints global " << PrintReg(Other.Reg) << ':'
2106 << OtherI->valno->id << '@' << OtherI->start << '\n');
2109 DEBUG(dbgs() << "\t\ttaints local " << PrintReg(Other.Reg) << ':'
2110 << OtherI->valno->id << '@' << OtherI->start
2111 << " to " << End << '\n');
2112 // A dead def is not a problem.
2115 TaintExtent.push_back(std::make_pair(End, TaintedLanes));
2117 // Check for another def in the MBB.
2118 if (++OtherI == Other.LR.end() || OtherI->start >= MBBEnd)
2121 // Lanes written by the new def are no longer tainted.
2122 const Val &OV = Other.Vals[OtherI->valno->id];
2123 TaintedLanes &= ~OV.WriteLanes;
2126 } while (TaintedLanes);
2130 bool JoinVals::usesLanes(const MachineInstr *MI, unsigned Reg, unsigned SubIdx,
2131 unsigned Lanes) const {
2132 if (MI->isDebugValue())
2134 for (ConstMIOperands MO(MI); MO.isValid(); ++MO) {
2135 if (!MO->isReg() || MO->isDef() || MO->getReg() != Reg)
2137 if (!MO->readsReg())
2139 if (Lanes & TRI->getSubRegIndexLaneMask(
2140 TRI->composeSubRegIndices(SubIdx, MO->getSubReg())))
2146 bool JoinVals::resolveConflicts(JoinVals &Other) {
2147 for (unsigned i = 0, e = LR.getNumValNums(); i != e; ++i) {
2149 assert (V.Resolution != CR_Impossible && "Unresolvable conflict");
2150 if (V.Resolution != CR_Unresolved)
2152 DEBUG(dbgs() << "\t\tconflict at " << PrintReg(Reg) << ':' << i
2153 << '@' << LR.getValNumInfo(i)->def << '\n');
2158 assert(V.OtherVNI && "Inconsistent conflict resolution.");
2159 VNInfo *VNI = LR.getValNumInfo(i);
2160 const Val &OtherV = Other.Vals[V.OtherVNI->id];
2162 // VNI is known to clobber some lanes in OtherVNI. If we go ahead with the
2163 // join, those lanes will be tainted with a wrong value. Get the extent of
2164 // the tainted lanes.
2165 unsigned TaintedLanes = V.WriteLanes & OtherV.ValidLanes;
2166 SmallVector<std::pair<SlotIndex, unsigned>, 8> TaintExtent;
2167 if (!taintExtent(i, TaintedLanes, Other, TaintExtent))
2168 // Tainted lanes would extend beyond the basic block.
2171 assert(!TaintExtent.empty() && "There should be at least one conflict.");
2173 // Now look at the instructions from VNI->def to TaintExtent (inclusive).
2174 MachineBasicBlock *MBB = Indexes->getMBBFromIndex(VNI->def);
2175 MachineBasicBlock::iterator MI = MBB->begin();
2176 if (!VNI->isPHIDef()) {
2177 MI = Indexes->getInstructionFromIndex(VNI->def);
2178 // No need to check the instruction defining VNI for reads.
2181 assert(!SlotIndex::isSameInstr(VNI->def, TaintExtent.front().first) &&
2182 "Interference ends on VNI->def. Should have been handled earlier");
2183 MachineInstr *LastMI =
2184 Indexes->getInstructionFromIndex(TaintExtent.front().first);
2185 assert(LastMI && "Range must end at a proper instruction");
2186 unsigned TaintNum = 0;
2188 assert(MI != MBB->end() && "Bad LastMI");
2189 if (usesLanes(MI, Other.Reg, Other.SubIdx, TaintedLanes)) {
2190 DEBUG(dbgs() << "\t\ttainted lanes used by: " << *MI);
2193 // LastMI is the last instruction to use the current value.
2194 if (&*MI == LastMI) {
2195 if (++TaintNum == TaintExtent.size())
2197 LastMI = Indexes->getInstructionFromIndex(TaintExtent[TaintNum].first);
2198 assert(LastMI && "Range must end at a proper instruction");
2199 TaintedLanes = TaintExtent[TaintNum].second;
2204 // The tainted lanes are unused.
2205 V.Resolution = CR_Replace;
2211 bool JoinVals::isPrunedValue(unsigned ValNo, JoinVals &Other) {
2212 Val &V = Vals[ValNo];
2213 if (V.Pruned || V.PrunedComputed)
2216 if (V.Resolution != CR_Erase && V.Resolution != CR_Merge)
2219 // Follow copies up the dominator tree and check if any intermediate value
2221 V.PrunedComputed = true;
2222 V.Pruned = Other.isPrunedValue(V.OtherVNI->id, *this);
2226 void JoinVals::pruneValues(JoinVals &Other,
2227 SmallVectorImpl<SlotIndex> &EndPoints,
2228 bool changeInstrs) {
2229 for (unsigned i = 0, e = LR.getNumValNums(); i != e; ++i) {
2230 SlotIndex Def = LR.getValNumInfo(i)->def;
2231 switch (Vals[i].Resolution) {
2235 // This value takes precedence over the value in Other.LR.
2236 LIS->pruneValue(Other.LR, Def, &EndPoints);
2237 // Check if we're replacing an IMPLICIT_DEF value. The IMPLICIT_DEF
2238 // instructions are only inserted to provide a live-out value for PHI
2239 // predecessors, so the instruction should simply go away once its value
2240 // has been replaced.
2241 Val &OtherV = Other.Vals[Vals[i].OtherVNI->id];
2242 bool EraseImpDef = OtherV.ErasableImplicitDef &&
2243 OtherV.Resolution == CR_Keep;
2244 if (!Def.isBlock()) {
2246 // Remove <def,read-undef> flags. This def is now a partial redef.
2247 // Also remove <def,dead> flags since the joined live range will
2248 // continue past this instruction.
2249 for (MIOperands MO(Indexes->getInstructionFromIndex(Def));
2250 MO.isValid(); ++MO) {
2251 if (MO->isReg() && MO->isDef() && MO->getReg() == Reg) {
2252 MO->setIsUndef(EraseImpDef);
2253 MO->setIsDead(false);
2257 // This value will reach instructions below, but we need to make sure
2258 // the live range also reaches the instruction at Def.
2260 EndPoints.push_back(Def);
2262 DEBUG(dbgs() << "\t\tpruned " << PrintReg(Other.Reg) << " at " << Def
2263 << ": " << Other.LR << '\n');
2268 if (isPrunedValue(i, Other)) {
2269 // This value is ultimately a copy of a pruned value in LR or Other.LR.
2270 // We can no longer trust the value mapping computed by
2271 // computeAssignment(), the value that was originally copied could have
2273 LIS->pruneValue(LR, Def, &EndPoints);
2274 DEBUG(dbgs() << "\t\tpruned all of " << PrintReg(Reg) << " at "
2275 << Def << ": " << LR << '\n');
2280 llvm_unreachable("Unresolved conflicts");
2285 void JoinVals::pruneSubRegValues(LiveInterval &LI, unsigned &ShrinkMask)
2287 // Look for values being erased.
2288 bool DidPrune = false;
2289 for (unsigned i = 0, e = LR.getNumValNums(); i != e; ++i) {
2290 if (Vals[i].Resolution != CR_Erase)
2293 // Check subranges at the point where the copy will be removed.
2294 SlotIndex Def = LR.getValNumInfo(i)->def;
2295 for (LiveInterval::SubRange &S : LI.subranges()) {
2296 LiveQueryResult Q = S.Query(Def);
2298 // If a subrange starts at the copy then an undefined value has been
2299 // copied and we must remove that subrange value as well.
2300 VNInfo *ValueOut = Q.valueOutOrDead();
2301 if (ValueOut != nullptr && Q.valueIn() == nullptr) {
2302 DEBUG(dbgs() << "\t\tPrune sublane " << format("%04X", S.LaneMask)
2303 << " at " << Def << "\n");
2304 LIS->pruneValue(S, Def, nullptr);
2306 // Mark value number as unused.
2307 ValueOut->markUnused();
2310 // If a subrange ends at the copy, then a value was copied but only
2311 // partially used later. Shrink the subregister range apropriately.
2312 if (Q.valueIn() != nullptr && Q.valueOut() == nullptr) {
2313 DEBUG(dbgs() << "\t\tDead uses at sublane "
2314 << format("%04X", S.LaneMask) << " at " << Def << "\n");
2315 ShrinkMask |= S.LaneMask;
2320 LI.removeEmptySubRanges();
2323 void JoinVals::eraseInstrs(SmallPtrSetImpl<MachineInstr*> &ErasedInstrs,
2324 SmallVectorImpl<unsigned> &ShrinkRegs) {
2325 for (unsigned i = 0, e = LR.getNumValNums(); i != e; ++i) {
2326 // Get the def location before markUnused() below invalidates it.
2327 SlotIndex Def = LR.getValNumInfo(i)->def;
2328 switch (Vals[i].Resolution) {
2330 // If an IMPLICIT_DEF value is pruned, it doesn't serve a purpose any
2331 // longer. The IMPLICIT_DEF instructions are only inserted by
2332 // PHIElimination to guarantee that all PHI predecessors have a value.
2333 if (!Vals[i].ErasableImplicitDef || !Vals[i].Pruned)
2335 // Remove value number i from LR.
2336 VNInfo *VNI = LR.getValNumInfo(i);
2337 LR.removeValNo(VNI);
2338 // Note that this VNInfo is reused and still referenced in NewVNInfo,
2339 // make it appear like an unused value number.
2341 DEBUG(dbgs() << "\t\tremoved " << i << '@' << Def << ": " << LR << '\n');
2346 MachineInstr *MI = Indexes->getInstructionFromIndex(Def);
2347 assert(MI && "No instruction to erase");
2349 unsigned Reg = MI->getOperand(1).getReg();
2350 if (TargetRegisterInfo::isVirtualRegister(Reg) &&
2351 Reg != CP.getSrcReg() && Reg != CP.getDstReg())
2352 ShrinkRegs.push_back(Reg);
2354 ErasedInstrs.insert(MI);
2355 DEBUG(dbgs() << "\t\terased:\t" << Def << '\t' << *MI);
2356 LIS->RemoveMachineInstrFromMaps(MI);
2357 MI->eraseFromParent();
2366 void RegisterCoalescer::joinSubRegRanges(LiveRange &LRange, LiveRange &RRange,
2368 const CoalescerPair &CP) {
2369 SmallVector<VNInfo*, 16> NewVNInfo;
2370 JoinVals RHSVals(RRange, CP.getSrcReg(), CP.getSrcIdx(), LaneMask,
2371 NewVNInfo, CP, LIS, TRI, true, true);
2372 JoinVals LHSVals(LRange, CP.getDstReg(), CP.getDstIdx(), LaneMask,
2373 NewVNInfo, CP, LIS, TRI, true, true);
2375 // Compute NewVNInfo and resolve conflicts (see also joinVirtRegs())
2376 // Conflicts should already be resolved so the mapping/resolution should
2378 if (!LHSVals.mapValues(RHSVals) || !RHSVals.mapValues(LHSVals))
2379 llvm_unreachable("Can't join subrange although main ranges are compatible");
2380 if (!LHSVals.resolveConflicts(RHSVals) || !RHSVals.resolveConflicts(LHSVals))
2381 llvm_unreachable("Can't join subrange although main ranges are compatible");
2383 // The merging algorithm in LiveInterval::join() can't handle conflicting
2384 // value mappings, so we need to remove any live ranges that overlap a
2385 // CR_Replace resolution. Collect a set of end points that can be used to
2386 // restore the live range after joining.
2387 SmallVector<SlotIndex, 8> EndPoints;
2388 LHSVals.pruneValues(RHSVals, EndPoints, false);
2389 RHSVals.pruneValues(LHSVals, EndPoints, false);
2394 // Join RRange into LHS.
2395 LRange.join(RRange, LHSVals.getAssignments(), RHSVals.getAssignments(),
2398 DEBUG(dbgs() << "\t\tjoined lanes: " << LRange << "\n");
2399 if (EndPoints.empty())
2402 // Recompute the parts of the live range we had to remove because of
2403 // CR_Replace conflicts.
2404 DEBUG(dbgs() << "\t\trestoring liveness to " << EndPoints.size()
2405 << " points: " << LRange << '\n');
2406 LIS->extendToIndices(LRange, EndPoints);
2409 void RegisterCoalescer::mergeSubRangeInto(LiveInterval &LI,
2410 const LiveRange &ToMerge,
2411 unsigned LaneMask, CoalescerPair &CP) {
2412 BumpPtrAllocator &Allocator = LIS->getVNInfoAllocator();
2413 for (LiveInterval::SubRange &R : LI.subranges()) {
2414 unsigned RMask = R.LaneMask;
2415 // LaneMask of subregisters common to subrange R and ToMerge.
2416 unsigned Common = RMask & LaneMask;
2417 // There is nothing to do without common subregs.
2421 DEBUG(dbgs() << format("\t\tCopy+Merge %04X into %04X\n", RMask, Common));
2422 // LaneMask of subregisters contained in the R range but not in ToMerge,
2423 // they have to split into their own subrange.
2424 unsigned LRest = RMask & ~LaneMask;
2425 LiveInterval::SubRange *CommonRange;
2428 DEBUG(dbgs() << format("\t\tReduce Lane to %04X\n", LRest));
2429 // Duplicate SubRange for newly merged common stuff.
2430 CommonRange = LI.createSubRangeFrom(Allocator, Common, R);
2432 // Reuse the existing range.
2433 R.LaneMask = Common;
2436 LiveRange RangeCopy(ToMerge, Allocator);
2437 joinSubRegRanges(*CommonRange, RangeCopy, Common, CP);
2441 if (LaneMask != 0) {
2442 DEBUG(dbgs() << format("\t\tNew Lane %04X\n", LaneMask));
2443 LI.createSubRangeFrom(Allocator, LaneMask, ToMerge);
2447 bool RegisterCoalescer::joinVirtRegs(CoalescerPair &CP) {
2448 SmallVector<VNInfo*, 16> NewVNInfo;
2449 LiveInterval &RHS = LIS->getInterval(CP.getSrcReg());
2450 LiveInterval &LHS = LIS->getInterval(CP.getDstReg());
2451 bool TrackSubRegLiveness = MRI->tracksSubRegLiveness();
2452 JoinVals RHSVals(RHS, CP.getSrcReg(), CP.getSrcIdx(), 0, NewVNInfo, CP, LIS,
2453 TRI, false, TrackSubRegLiveness);
2454 JoinVals LHSVals(LHS, CP.getDstReg(), CP.getDstIdx(), 0, NewVNInfo, CP, LIS,
2455 TRI, false, TrackSubRegLiveness);
2457 DEBUG(dbgs() << "\t\tRHS = " << RHS
2458 << "\n\t\tLHS = " << LHS
2461 // First compute NewVNInfo and the simple value mappings.
2462 // Detect impossible conflicts early.
2463 if (!LHSVals.mapValues(RHSVals) || !RHSVals.mapValues(LHSVals))
2466 // Some conflicts can only be resolved after all values have been mapped.
2467 if (!LHSVals.resolveConflicts(RHSVals) || !RHSVals.resolveConflicts(LHSVals))
2470 // All clear, the live ranges can be merged.
2471 if (RHS.hasSubRanges() || LHS.hasSubRanges()) {
2472 BumpPtrAllocator &Allocator = LIS->getVNInfoAllocator();
2474 // Transform lanemasks from the LHS to masks in the coalesced register and
2475 // create initial subranges if necessary.
2476 unsigned DstIdx = CP.getDstIdx();
2477 if (!LHS.hasSubRanges()) {
2478 unsigned Mask = DstIdx == 0 ? CP.getNewRC()->getLaneMask()
2479 : TRI->getSubRegIndexLaneMask(DstIdx);
2480 // LHS must support subregs or we wouldn't be in this codepath.
2482 LHS.createSubRangeFrom(Allocator, Mask, LHS);
2483 } else if (DstIdx != 0) {
2484 // Transform LHS lanemasks to new register class if necessary.
2485 for (LiveInterval::SubRange &R : LHS.subranges()) {
2486 unsigned Mask = TRI->composeSubRegIndexLaneMask(DstIdx, R.LaneMask);
2490 DEBUG(dbgs() << "\t\tLHST = " << PrintReg(CP.getDstReg())
2491 << ' ' << LHS << '\n');
2493 // Determine lanemasks of RHS in the coalesced register and merge subranges.
2494 unsigned SrcIdx = CP.getSrcIdx();
2495 if (!RHS.hasSubRanges()) {
2496 unsigned Mask = SrcIdx == 0 ? CP.getNewRC()->getLaneMask()
2497 : TRI->getSubRegIndexLaneMask(SrcIdx);
2498 mergeSubRangeInto(LHS, RHS, Mask, CP);
2500 // Pair up subranges and merge.
2501 for (LiveInterval::SubRange &R : RHS.subranges()) {
2502 unsigned Mask = TRI->composeSubRegIndexLaneMask(SrcIdx, R.LaneMask);
2503 mergeSubRangeInto(LHS, R, Mask, CP);
2507 DEBUG(dbgs() << "\tJoined SubRanges " << LHS << "\n");
2509 LHSVals.pruneSubRegValues(LHS, ShrinkMask);
2510 RHSVals.pruneSubRegValues(LHS, ShrinkMask);
2513 // The merging algorithm in LiveInterval::join() can't handle conflicting
2514 // value mappings, so we need to remove any live ranges that overlap a
2515 // CR_Replace resolution. Collect a set of end points that can be used to
2516 // restore the live range after joining.
2517 SmallVector<SlotIndex, 8> EndPoints;
2518 LHSVals.pruneValues(RHSVals, EndPoints, true);
2519 RHSVals.pruneValues(LHSVals, EndPoints, true);
2521 // Erase COPY and IMPLICIT_DEF instructions. This may cause some external
2522 // registers to require trimming.
2523 SmallVector<unsigned, 8> ShrinkRegs;
2524 LHSVals.eraseInstrs(ErasedInstrs, ShrinkRegs);
2525 RHSVals.eraseInstrs(ErasedInstrs, ShrinkRegs);
2526 while (!ShrinkRegs.empty())
2527 LIS->shrinkToUses(&LIS->getInterval(ShrinkRegs.pop_back_val()));
2529 // Join RHS into LHS.
2530 LHS.join(RHS, LHSVals.getAssignments(), RHSVals.getAssignments(), NewVNInfo);
2532 // Kill flags are going to be wrong if the live ranges were overlapping.
2533 // Eventually, we should simply clear all kill flags when computing live
2534 // ranges. They are reinserted after register allocation.
2535 MRI->clearKillFlags(LHS.reg);
2536 MRI->clearKillFlags(RHS.reg);
2538 if (!EndPoints.empty()) {
2539 // Recompute the parts of the live range we had to remove because of
2540 // CR_Replace conflicts.
2541 DEBUG(dbgs() << "\t\trestoring liveness to " << EndPoints.size()
2542 << " points: " << LHS << '\n');
2543 LIS->extendToIndices((LiveRange&)LHS, EndPoints);
2549 bool RegisterCoalescer::joinIntervals(CoalescerPair &CP) {
2550 return CP.isPhys() ? joinReservedPhysReg(CP) : joinVirtRegs(CP);
2554 /// Information concerning MBB coalescing priority.
2555 struct MBBPriorityInfo {
2556 MachineBasicBlock *MBB;
2560 MBBPriorityInfo(MachineBasicBlock *mbb, unsigned depth, bool issplit)
2561 : MBB(mbb), Depth(depth), IsSplit(issplit) {}
2565 /// C-style comparator that sorts first based on the loop depth of the basic
2566 /// block (the unsigned), and then on the MBB number.
2568 /// EnableGlobalCopies assumes that the primary sort key is loop depth.
2569 static int compareMBBPriority(const MBBPriorityInfo *LHS,
2570 const MBBPriorityInfo *RHS) {
2571 // Deeper loops first
2572 if (LHS->Depth != RHS->Depth)
2573 return LHS->Depth > RHS->Depth ? -1 : 1;
2575 // Try to unsplit critical edges next.
2576 if (LHS->IsSplit != RHS->IsSplit)
2577 return LHS->IsSplit ? -1 : 1;
2579 // Prefer blocks that are more connected in the CFG. This takes care of
2580 // the most difficult copies first while intervals are short.
2581 unsigned cl = LHS->MBB->pred_size() + LHS->MBB->succ_size();
2582 unsigned cr = RHS->MBB->pred_size() + RHS->MBB->succ_size();
2584 return cl > cr ? -1 : 1;
2586 // As a last resort, sort by block number.
2587 return LHS->MBB->getNumber() < RHS->MBB->getNumber() ? -1 : 1;
2590 /// \returns true if the given copy uses or defines a local live range.
2591 static bool isLocalCopy(MachineInstr *Copy, const LiveIntervals *LIS) {
2592 if (!Copy->isCopy())
2595 if (Copy->getOperand(1).isUndef())
2598 unsigned SrcReg = Copy->getOperand(1).getReg();
2599 unsigned DstReg = Copy->getOperand(0).getReg();
2600 if (TargetRegisterInfo::isPhysicalRegister(SrcReg)
2601 || TargetRegisterInfo::isPhysicalRegister(DstReg))
2604 return LIS->intervalIsInOneMBB(LIS->getInterval(SrcReg))
2605 || LIS->intervalIsInOneMBB(LIS->getInterval(DstReg));
2608 bool RegisterCoalescer::
2609 copyCoalesceWorkList(MutableArrayRef<MachineInstr*> CurrList) {
2610 bool Progress = false;
2611 for (unsigned i = 0, e = CurrList.size(); i != e; ++i) {
2614 // Skip instruction pointers that have already been erased, for example by
2615 // dead code elimination.
2616 if (ErasedInstrs.erase(CurrList[i])) {
2617 CurrList[i] = nullptr;
2621 bool Success = joinCopy(CurrList[i], Again);
2622 Progress |= Success;
2623 if (Success || !Again)
2624 CurrList[i] = nullptr;
2630 RegisterCoalescer::copyCoalesceInMBB(MachineBasicBlock *MBB) {
2631 DEBUG(dbgs() << MBB->getName() << ":\n");
2633 // Collect all copy-like instructions in MBB. Don't start coalescing anything
2634 // yet, it might invalidate the iterator.
2635 const unsigned PrevSize = WorkList.size();
2636 if (JoinGlobalCopies) {
2637 // Coalesce copies bottom-up to coalesce local defs before local uses. They
2638 // are not inherently easier to resolve, but slightly preferable until we
2639 // have local live range splitting. In particular this is required by
2640 // cmp+jmp macro fusion.
2641 for (MachineBasicBlock::iterator MII = MBB->begin(), E = MBB->end();
2643 if (!MII->isCopyLike())
2645 if (isLocalCopy(&(*MII), LIS))
2646 LocalWorkList.push_back(&(*MII));
2648 WorkList.push_back(&(*MII));
2652 for (MachineBasicBlock::iterator MII = MBB->begin(), E = MBB->end();
2654 if (MII->isCopyLike())
2655 WorkList.push_back(MII);
2657 // Try coalescing the collected copies immediately, and remove the nulls.
2658 // This prevents the WorkList from getting too large since most copies are
2659 // joinable on the first attempt.
2660 MutableArrayRef<MachineInstr*>
2661 CurrList(WorkList.begin() + PrevSize, WorkList.end());
2662 if (copyCoalesceWorkList(CurrList))
2663 WorkList.erase(std::remove(WorkList.begin() + PrevSize, WorkList.end(),
2664 (MachineInstr*)nullptr), WorkList.end());
2667 void RegisterCoalescer::coalesceLocals() {
2668 copyCoalesceWorkList(LocalWorkList);
2669 for (unsigned j = 0, je = LocalWorkList.size(); j != je; ++j) {
2670 if (LocalWorkList[j])
2671 WorkList.push_back(LocalWorkList[j]);
2673 LocalWorkList.clear();
2676 void RegisterCoalescer::joinAllIntervals() {
2677 DEBUG(dbgs() << "********** JOINING INTERVALS ***********\n");
2678 assert(WorkList.empty() && LocalWorkList.empty() && "Old data still around.");
2680 std::vector<MBBPriorityInfo> MBBs;
2681 MBBs.reserve(MF->size());
2682 for (MachineFunction::iterator I = MF->begin(), E = MF->end();I != E;++I){
2683 MachineBasicBlock *MBB = I;
2684 MBBs.push_back(MBBPriorityInfo(MBB, Loops->getLoopDepth(MBB),
2685 JoinSplitEdges && isSplitEdge(MBB)));
2687 array_pod_sort(MBBs.begin(), MBBs.end(), compareMBBPriority);
2689 // Coalesce intervals in MBB priority order.
2690 unsigned CurrDepth = UINT_MAX;
2691 for (unsigned i = 0, e = MBBs.size(); i != e; ++i) {
2692 // Try coalescing the collected local copies for deeper loops.
2693 if (JoinGlobalCopies && MBBs[i].Depth < CurrDepth) {
2695 CurrDepth = MBBs[i].Depth;
2697 copyCoalesceInMBB(MBBs[i].MBB);
2701 // Joining intervals can allow other intervals to be joined. Iteratively join
2702 // until we make no progress.
2703 while (copyCoalesceWorkList(WorkList))
2707 void RegisterCoalescer::releaseMemory() {
2708 ErasedInstrs.clear();
2711 InflateRegs.clear();
2714 bool RegisterCoalescer::runOnMachineFunction(MachineFunction &fn) {
2716 MRI = &fn.getRegInfo();
2717 TM = &fn.getTarget();
2718 const TargetSubtargetInfo &STI = fn.getSubtarget();
2719 TRI = STI.getRegisterInfo();
2720 TII = STI.getInstrInfo();
2721 LIS = &getAnalysis<LiveIntervals>();
2722 AA = &getAnalysis<AliasAnalysis>();
2723 Loops = &getAnalysis<MachineLoopInfo>();
2724 if (EnableGlobalCopies == cl::BOU_UNSET)
2725 JoinGlobalCopies = STI.useMachineScheduler();
2727 JoinGlobalCopies = (EnableGlobalCopies == cl::BOU_TRUE);
2729 // The MachineScheduler does not currently require JoinSplitEdges. This will
2730 // either be enabled unconditionally or replaced by a more general live range
2731 // splitting optimization.
2732 JoinSplitEdges = EnableJoinSplits;
2734 DEBUG(dbgs() << "********** SIMPLE REGISTER COALESCING **********\n"
2735 << "********** Function: " << MF->getName() << '\n');
2737 if (VerifyCoalescing)
2738 MF->verify(this, "Before register coalescing");
2740 RegClassInfo.runOnMachineFunction(fn);
2742 // Join (coalesce) intervals if requested.
2746 // After deleting a lot of copies, register classes may be less constrained.
2747 // Removing sub-register operands may allow GR32_ABCD -> GR32 and DPR_VFP2 ->
2749 array_pod_sort(InflateRegs.begin(), InflateRegs.end());
2750 InflateRegs.erase(std::unique(InflateRegs.begin(), InflateRegs.end()),
2752 DEBUG(dbgs() << "Trying to inflate " << InflateRegs.size() << " regs.\n");
2753 for (unsigned i = 0, e = InflateRegs.size(); i != e; ++i) {
2754 unsigned Reg = InflateRegs[i];
2755 if (MRI->reg_nodbg_empty(Reg))
2757 if (MRI->recomputeRegClass(Reg)) {
2758 DEBUG(dbgs() << PrintReg(Reg) << " inflated to "
2759 << TRI->getRegClassName(MRI->getRegClass(Reg)) << '\n');
2760 LiveInterval &LI = LIS->getInterval(Reg);
2761 unsigned MaxMask = MRI->getMaxLaneMaskForVReg(Reg);
2763 // If the inflated register class does not support subregisters anymore
2764 // remove the subranges.
2765 LI.clearSubRanges();
2768 // If subranges are still supported, then the same subregs should still
2770 for (LiveInterval::SubRange &S : LI.subranges()) {
2771 assert ((S.LaneMask & ~MaxMask) == 0);
2780 if (VerifyCoalescing)
2781 MF->verify(this, "After register coalescing");
2785 void RegisterCoalescer::print(raw_ostream &O, const Module* m) const {