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Diffstat (limited to 'contrib/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp')
| -rw-r--r-- | contrib/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp | 1891 |
1 files changed, 1891 insertions, 0 deletions
diff --git a/contrib/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp b/contrib/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp new file mode 100644 index 0000000..e69d3e4 --- /dev/null +++ b/contrib/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp @@ -0,0 +1,1891 @@ +//===-- SimpleRegisterCoalescing.cpp - Register Coalescing ----------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file implements a simple register coalescing pass that attempts to +// aggressively coalesce every register copy that it can. +// +//===----------------------------------------------------------------------===// + +#define DEBUG_TYPE "regcoalescing" +#include "SimpleRegisterCoalescing.h" +#include "VirtRegMap.h" +#include "llvm/CodeGen/LiveIntervalAnalysis.h" +#include "llvm/Value.h" +#include "llvm/Analysis/AliasAnalysis.h" +#include "llvm/CodeGen/MachineFrameInfo.h" +#include "llvm/CodeGen/MachineInstr.h" +#include "llvm/CodeGen/MachineLoopInfo.h" +#include "llvm/CodeGen/MachineRegisterInfo.h" +#include "llvm/CodeGen/Passes.h" +#include "llvm/CodeGen/RegisterCoalescer.h" +#include "llvm/Target/TargetInstrInfo.h" +#include "llvm/Target/TargetMachine.h" +#include "llvm/Target/TargetOptions.h" +#include "llvm/Support/CommandLine.h" +#include "llvm/Support/Debug.h" +#include "llvm/Support/ErrorHandling.h" +#include "llvm/Support/raw_ostream.h" +#include "llvm/ADT/OwningPtr.h" +#include "llvm/ADT/SmallSet.h" +#include "llvm/ADT/Statistic.h" +#include "llvm/ADT/STLExtras.h" +#include <algorithm> +#include <cmath> +using namespace llvm; + +STATISTIC(numJoins , "Number of interval joins performed"); +STATISTIC(numCrossRCs , "Number of cross class joins performed"); +STATISTIC(numCommutes , "Number of instruction commuting performed"); +STATISTIC(numExtends , "Number of copies extended"); +STATISTIC(NumReMats , "Number of instructions re-materialized"); +STATISTIC(numPeep , "Number of identity moves eliminated after coalescing"); +STATISTIC(numAborts , "Number of times interval joining aborted"); +STATISTIC(numDeadValNo, "Number of valno def marked dead"); + +char SimpleRegisterCoalescing::ID = 0; +static cl::opt<bool> +EnableJoining("join-liveintervals", + cl::desc("Coalesce copies (default=true)"), + cl::init(true)); + +static cl::opt<bool> +DisableCrossClassJoin("disable-cross-class-join", + cl::desc("Avoid coalescing cross register class copies"), + cl::init(false), cl::Hidden); + +static RegisterPass<SimpleRegisterCoalescing> +X("simple-register-coalescing", "Simple Register Coalescing"); + +// Declare that we implement the RegisterCoalescer interface +static RegisterAnalysisGroup<RegisterCoalescer, true/*The Default*/> V(X); + +const PassInfo *const llvm::SimpleRegisterCoalescingID = &X; + +void SimpleRegisterCoalescing::getAnalysisUsage(AnalysisUsage &AU) const { + AU.setPreservesCFG(); + AU.addRequired<AliasAnalysis>(); + AU.addRequired<LiveIntervals>(); + AU.addPreserved<LiveIntervals>(); + AU.addPreserved<SlotIndexes>(); + AU.addRequired<MachineLoopInfo>(); + AU.addPreserved<MachineLoopInfo>(); + AU.addPreservedID(MachineDominatorsID); + if (StrongPHIElim) + AU.addPreservedID(StrongPHIEliminationID); + else + AU.addPreservedID(PHIEliminationID); + AU.addPreservedID(TwoAddressInstructionPassID); + MachineFunctionPass::getAnalysisUsage(AU); +} + +/// AdjustCopiesBackFrom - We found a non-trivially-coalescable copy with IntA +/// being the source and IntB being the dest, thus this defines a value number +/// in IntB. If the source value number (in IntA) is defined by a copy from B, +/// see if we can merge these two pieces of B into a single value number, +/// eliminating a copy. For example: +/// +/// A3 = B0 +/// ... +/// B1 = A3 <- this copy +/// +/// In this case, B0 can be extended to where the B1 copy lives, allowing the B1 +/// value number to be replaced with B0 (which simplifies the B liveinterval). +/// +/// This returns true if an interval was modified. +/// +bool SimpleRegisterCoalescing::AdjustCopiesBackFrom(const CoalescerPair &CP, + MachineInstr *CopyMI) { + // Bail if there is no dst interval - can happen when merging physical subreg + // operations. + if (!li_->hasInterval(CP.getDstReg())) + return false; + + LiveInterval &IntA = + li_->getInterval(CP.isFlipped() ? CP.getDstReg() : CP.getSrcReg()); + LiveInterval &IntB = + li_->getInterval(CP.isFlipped() ? CP.getSrcReg() : CP.getDstReg()); + SlotIndex CopyIdx = li_->getInstructionIndex(CopyMI).getDefIndex(); + + // BValNo is a value number in B that is defined by a copy from A. 'B3' in + // the example above. + LiveInterval::iterator BLR = IntB.FindLiveRangeContaining(CopyIdx); + if (BLR == IntB.end()) return false; + VNInfo *BValNo = BLR->valno; + + // Get the location that B is defined at. Two options: either this value has + // an unknown definition point or it is defined at CopyIdx. If unknown, we + // can't process it. + if (!BValNo->getCopy()) return false; + assert(BValNo->def == CopyIdx && "Copy doesn't define the value?"); + + // AValNo is the value number in A that defines the copy, A3 in the example. + SlotIndex CopyUseIdx = CopyIdx.getUseIndex(); + LiveInterval::iterator ALR = IntA.FindLiveRangeContaining(CopyUseIdx); + // The live range might not exist after fun with physreg coalescing. + if (ALR == IntA.end()) return false; + VNInfo *AValNo = ALR->valno; + // If it's re-defined by an early clobber somewhere in the live range, then + // it's not safe to eliminate the copy. FIXME: This is a temporary workaround. + // See PR3149: + // 172 %ECX<def> = MOV32rr %reg1039<kill> + // 180 INLINEASM <es:subl $5,$1 + // sbbl $3,$0>, 10, %EAX<def>, 14, %ECX<earlyclobber,def>, 9, + // %EAX<kill>, + // 36, <fi#0>, 1, %reg0, 0, 9, %ECX<kill>, 36, <fi#1>, 1, %reg0, 0 + // 188 %EAX<def> = MOV32rr %EAX<kill> + // 196 %ECX<def> = MOV32rr %ECX<kill> + // 204 %ECX<def> = MOV32rr %ECX<kill> + // 212 %EAX<def> = MOV32rr %EAX<kill> + // 220 %EAX<def> = MOV32rr %EAX + // 228 %reg1039<def> = MOV32rr %ECX<kill> + // The early clobber operand ties ECX input to the ECX def. + // + // The live interval of ECX is represented as this: + // %reg20,inf = [46,47:1)[174,230:0) 0@174-(230) 1@46-(47) + // The coalescer has no idea there was a def in the middle of [174,230]. + if (AValNo->hasRedefByEC()) + return false; + + // If AValNo is defined as a copy from IntB, we can potentially process this. + // Get the instruction that defines this value number. + if (!CP.isCoalescable(AValNo->getCopy())) + return false; + + // Get the LiveRange in IntB that this value number starts with. + LiveInterval::iterator ValLR = + IntB.FindLiveRangeContaining(AValNo->def.getPrevSlot()); + if (ValLR == IntB.end()) + return false; + + // Make sure that the end of the live range is inside the same block as + // CopyMI. + MachineInstr *ValLREndInst = + li_->getInstructionFromIndex(ValLR->end.getPrevSlot()); + if (!ValLREndInst || ValLREndInst->getParent() != CopyMI->getParent()) + return false; + + // Okay, we now know that ValLR ends in the same block that the CopyMI + // live-range starts. If there are no intervening live ranges between them in + // IntB, we can merge them. + if (ValLR+1 != BLR) return false; + + // If a live interval is a physical register, conservatively check if any + // of its sub-registers is overlapping the live interval of the virtual + // register. If so, do not coalesce. + if (TargetRegisterInfo::isPhysicalRegister(IntB.reg) && + *tri_->getSubRegisters(IntB.reg)) { + for (const unsigned* SR = tri_->getSubRegisters(IntB.reg); *SR; ++SR) + if (li_->hasInterval(*SR) && IntA.overlaps(li_->getInterval(*SR))) { + DEBUG({ + dbgs() << "\t\tInterfere with sub-register "; + li_->getInterval(*SR).print(dbgs(), tri_); + }); + return false; + } + } + + DEBUG({ + dbgs() << "Extending: "; + IntB.print(dbgs(), tri_); + }); + + SlotIndex FillerStart = ValLR->end, FillerEnd = BLR->start; + // We are about to delete CopyMI, so need to remove it as the 'instruction + // that defines this value #'. Update the valnum with the new defining + // instruction #. + BValNo->def = FillerStart; + BValNo->setCopy(0); + + // Okay, we can merge them. We need to insert a new liverange: + // [ValLR.end, BLR.begin) of either value number, then we merge the + // two value numbers. + IntB.addRange(LiveRange(FillerStart, FillerEnd, BValNo)); + + // If the IntB live range is assigned to a physical register, and if that + // physreg has sub-registers, update their live intervals as well. + if (TargetRegisterInfo::isPhysicalRegister(IntB.reg)) { + for (const unsigned *SR = tri_->getSubRegisters(IntB.reg); *SR; ++SR) { + if (!li_->hasInterval(*SR)) + continue; + LiveInterval &SRLI = li_->getInterval(*SR); + SRLI.addRange(LiveRange(FillerStart, FillerEnd, + SRLI.getNextValue(FillerStart, 0, true, + li_->getVNInfoAllocator()))); + } + } + + // Okay, merge "B1" into the same value number as "B0". + if (BValNo != ValLR->valno) { + IntB.MergeValueNumberInto(BValNo, ValLR->valno); + } + DEBUG({ + dbgs() << " result = "; + IntB.print(dbgs(), tri_); + dbgs() << "\n"; + }); + + // If the source instruction was killing the source register before the + // merge, unset the isKill marker given the live range has been extended. + int UIdx = ValLREndInst->findRegisterUseOperandIdx(IntB.reg, true); + if (UIdx != -1) { + ValLREndInst->getOperand(UIdx).setIsKill(false); + } + + // If the copy instruction was killing the destination register before the + // merge, find the last use and trim the live range. That will also add the + // isKill marker. + if (ALR->end == CopyIdx) + TrimLiveIntervalToLastUse(CopyUseIdx, CopyMI->getParent(), IntA, ALR); + + ++numExtends; + return true; +} + +/// HasOtherReachingDefs - Return true if there are definitions of IntB +/// other than BValNo val# that can reach uses of AValno val# of IntA. +bool SimpleRegisterCoalescing::HasOtherReachingDefs(LiveInterval &IntA, + LiveInterval &IntB, + VNInfo *AValNo, + VNInfo *BValNo) { + for (LiveInterval::iterator AI = IntA.begin(), AE = IntA.end(); + AI != AE; ++AI) { + if (AI->valno != AValNo) continue; + LiveInterval::Ranges::iterator BI = + std::upper_bound(IntB.ranges.begin(), IntB.ranges.end(), AI->start); + if (BI != IntB.ranges.begin()) + --BI; + for (; BI != IntB.ranges.end() && AI->end >= BI->start; ++BI) { + if (BI->valno == BValNo) + continue; + // When BValNo is null, we're looking for a dummy clobber-value for a subreg. + if (!BValNo && !BI->valno->isDefAccurate() && !BI->valno->getCopy()) + continue; + if (BI->start <= AI->start && BI->end > AI->start) + return true; + if (BI->start > AI->start && BI->start < AI->end) + return true; + } + } + return false; +} + +static void +TransferImplicitOps(MachineInstr *MI, MachineInstr *NewMI) { + for (unsigned i = MI->getDesc().getNumOperands(), e = MI->getNumOperands(); + i != e; ++i) { + MachineOperand &MO = MI->getOperand(i); + if (MO.isReg() && MO.isImplicit()) + NewMI->addOperand(MO); + } +} + +/// RemoveCopyByCommutingDef - We found a non-trivially-coalescable copy with +/// IntA being the source and IntB being the dest, thus this defines a value +/// number in IntB. If the source value number (in IntA) is defined by a +/// commutable instruction and its other operand is coalesced to the copy dest +/// register, see if we can transform the copy into a noop by commuting the +/// definition. For example, +/// +/// A3 = op A2 B0<kill> +/// ... +/// B1 = A3 <- this copy +/// ... +/// = op A3 <- more uses +/// +/// ==> +/// +/// B2 = op B0 A2<kill> +/// ... +/// B1 = B2 <- now an identify copy +/// ... +/// = op B2 <- more uses +/// +/// This returns true if an interval was modified. +/// +bool SimpleRegisterCoalescing::RemoveCopyByCommutingDef(const CoalescerPair &CP, + MachineInstr *CopyMI) { + // FIXME: For now, only eliminate the copy by commuting its def when the + // source register is a virtual register. We want to guard against cases + // where the copy is a back edge copy and commuting the def lengthen the + // live interval of the source register to the entire loop. + if (CP.isPhys() && CP.isFlipped()) + return false; + + // Bail if there is no dst interval. + if (!li_->hasInterval(CP.getDstReg())) + return false; + + SlotIndex CopyIdx = + li_->getInstructionIndex(CopyMI).getDefIndex(); + + LiveInterval &IntA = + li_->getInterval(CP.isFlipped() ? CP.getDstReg() : CP.getSrcReg()); + LiveInterval &IntB = + li_->getInterval(CP.isFlipped() ? CP.getSrcReg() : CP.getDstReg()); + + // BValNo is a value number in B that is defined by a copy from A. 'B3' in + // the example above. + LiveInterval::iterator BLR = IntB.FindLiveRangeContaining(CopyIdx); + if (BLR == IntB.end()) return false; + VNInfo *BValNo = BLR->valno; + + // Get the location that B is defined at. Two options: either this value has + // an unknown definition point or it is defined at CopyIdx. If unknown, we + // can't process it. + if (!BValNo->getCopy()) return false; + assert(BValNo->def == CopyIdx && "Copy doesn't define the value?"); + + // AValNo is the value number in A that defines the copy, A3 in the example. + LiveInterval::iterator ALR = + IntA.FindLiveRangeContaining(CopyIdx.getUseIndex()); // + + assert(ALR != IntA.end() && "Live range not found!"); + VNInfo *AValNo = ALR->valno; + // If other defs can reach uses of this def, then it's not safe to perform + // the optimization. FIXME: Do isPHIDef and isDefAccurate both need to be + // tested? + if (AValNo->isPHIDef() || !AValNo->isDefAccurate() || + AValNo->isUnused() || AValNo->hasPHIKill()) + return false; + MachineInstr *DefMI = li_->getInstructionFromIndex(AValNo->def); + if (!DefMI) + return false; + const TargetInstrDesc &TID = DefMI->getDesc(); + if (!TID.isCommutable()) + return false; + // If DefMI is a two-address instruction then commuting it will change the + // destination register. + int DefIdx = DefMI->findRegisterDefOperandIdx(IntA.reg); + assert(DefIdx != -1); + unsigned UseOpIdx; + if (!DefMI->isRegTiedToUseOperand(DefIdx, &UseOpIdx)) + return false; + unsigned Op1, Op2, NewDstIdx; + if (!tii_->findCommutedOpIndices(DefMI, Op1, Op2)) + return false; + if (Op1 == UseOpIdx) + NewDstIdx = Op2; + else if (Op2 == UseOpIdx) + NewDstIdx = Op1; + else + return false; + + MachineOperand &NewDstMO = DefMI->getOperand(NewDstIdx); + unsigned NewReg = NewDstMO.getReg(); + if (NewReg != IntB.reg || !NewDstMO.isKill()) + return false; + + // Make sure there are no other definitions of IntB that would reach the + // uses which the new definition can reach. + if (HasOtherReachingDefs(IntA, IntB, AValNo, BValNo)) + return false; + + bool BHasSubRegs = false; + if (TargetRegisterInfo::isPhysicalRegister(IntB.reg)) + BHasSubRegs = *tri_->getSubRegisters(IntB.reg); + + // Abort if the subregisters of IntB.reg have values that are not simply the + // clobbers from the superreg. + if (BHasSubRegs) + for (const unsigned *SR = tri_->getSubRegisters(IntB.reg); *SR; ++SR) + if (li_->hasInterval(*SR) && + HasOtherReachingDefs(IntA, li_->getInterval(*SR), AValNo, 0)) + return false; + + // If some of the uses of IntA.reg is already coalesced away, return false. + // It's not possible to determine whether it's safe to perform the coalescing. + for (MachineRegisterInfo::use_nodbg_iterator UI = + mri_->use_nodbg_begin(IntA.reg), + UE = mri_->use_nodbg_end(); UI != UE; ++UI) { + MachineInstr *UseMI = &*UI; + SlotIndex UseIdx = li_->getInstructionIndex(UseMI); + LiveInterval::iterator ULR = IntA.FindLiveRangeContaining(UseIdx); + if (ULR == IntA.end()) + continue; + if (ULR->valno == AValNo && JoinedCopies.count(UseMI)) + return false; + } + + // At this point we have decided that it is legal to do this + // transformation. Start by commuting the instruction. + MachineBasicBlock *MBB = DefMI->getParent(); + MachineInstr *NewMI = tii_->commuteInstruction(DefMI); + if (!NewMI) + return false; + if (NewMI != DefMI) { + li_->ReplaceMachineInstrInMaps(DefMI, NewMI); + MBB->insert(DefMI, NewMI); + MBB->erase(DefMI); + } + unsigned OpIdx = NewMI->findRegisterUseOperandIdx(IntA.reg, false); + NewMI->getOperand(OpIdx).setIsKill(); + + bool BHasPHIKill = BValNo->hasPHIKill(); + SmallVector<VNInfo*, 4> BDeadValNos; + std::map<SlotIndex, SlotIndex> BExtend; + + // If ALR and BLR overlaps and end of BLR extends beyond end of ALR, e.g. + // A = or A, B + // ... + // B = A + // ... + // C = A<kill> + // ... + // = B + bool Extended = BLR->end > ALR->end && ALR->end != ALR->start; + if (Extended) + BExtend[ALR->end] = BLR->end; + + // Update uses of IntA of the specific Val# with IntB. + for (MachineRegisterInfo::use_iterator UI = mri_->use_begin(IntA.reg), + UE = mri_->use_end(); UI != UE;) { + MachineOperand &UseMO = UI.getOperand(); + MachineInstr *UseMI = &*UI; + ++UI; + if (JoinedCopies.count(UseMI)) + continue; + if (UseMI->isDebugValue()) { + // FIXME These don't have an instruction index. Not clear we have enough + // info to decide whether to do this replacement or not. For now do it. + UseMO.setReg(NewReg); + continue; + } + SlotIndex UseIdx = li_->getInstructionIndex(UseMI).getUseIndex(); + LiveInterval::iterator ULR = IntA.FindLiveRangeContaining(UseIdx); + if (ULR == IntA.end() || ULR->valno != AValNo) + continue; + if (TargetRegisterInfo::isPhysicalRegister(NewReg)) + UseMO.substPhysReg(NewReg, *tri_); + else + UseMO.setReg(NewReg); + if (UseMI == CopyMI) + continue; + if (UseMO.isKill()) { + if (Extended) + UseMO.setIsKill(false); + } + unsigned SrcReg, DstReg, SrcSubIdx, DstSubIdx; + if (UseMI->isCopy()) { + if (UseMI->getOperand(0).getReg() != IntB.reg || + UseMI->getOperand(0).getSubReg()) + continue; + } else if (tii_->isMoveInstr(*UseMI, SrcReg, DstReg, SrcSubIdx, DstSubIdx)){ + if (DstReg != IntB.reg || DstSubIdx) + continue; + } else + continue; + // This copy will become a noop. If it's defining a new val#, + // remove that val# as well. However this live range is being + // extended to the end of the existing live range defined by the copy. + SlotIndex DefIdx = UseIdx.getDefIndex(); + const LiveRange *DLR = IntB.getLiveRangeContaining(DefIdx); + if (!DLR) + continue; + BHasPHIKill |= DLR->valno->hasPHIKill(); + assert(DLR->valno->def == DefIdx); + BDeadValNos.push_back(DLR->valno); + BExtend[DLR->start] = DLR->end; + JoinedCopies.insert(UseMI); + } + + // We need to insert a new liverange: [ALR.start, LastUse). It may be we can + // simply extend BLR if CopyMI doesn't end the range. + DEBUG({ + dbgs() << "Extending: "; + IntB.print(dbgs(), tri_); + }); + + // Remove val#'s defined by copies that will be coalesced away. + for (unsigned i = 0, e = BDeadValNos.size(); i != e; ++i) { + VNInfo *DeadVNI = BDeadValNos[i]; + if (BHasSubRegs) { + for (const unsigned *SR = tri_->getSubRegisters(IntB.reg); *SR; ++SR) { + if (!li_->hasInterval(*SR)) + continue; + LiveInterval &SRLI = li_->getInterval(*SR); + if (const LiveRange *SRLR = SRLI.getLiveRangeContaining(DeadVNI->def)) + SRLI.removeValNo(SRLR->valno); + } + } + IntB.removeValNo(BDeadValNos[i]); + } + + // Extend BValNo by merging in IntA live ranges of AValNo. Val# definition + // is updated. + VNInfo *ValNo = BValNo; + ValNo->def = AValNo->def; + ValNo->setCopy(0); + for (LiveInterval::iterator AI = IntA.begin(), AE = IntA.end(); + AI != AE; ++AI) { + if (AI->valno != AValNo) continue; + SlotIndex End = AI->end; + std::map<SlotIndex, SlotIndex>::iterator + EI = BExtend.find(End); + if (EI != BExtend.end()) + End = EI->second; + IntB.addRange(LiveRange(AI->start, End, ValNo)); + } + ValNo->setHasPHIKill(BHasPHIKill); + + DEBUG({ + dbgs() << " result = "; + IntB.print(dbgs(), tri_); + dbgs() << "\nShortening: "; + IntA.print(dbgs(), tri_); + }); + + IntA.removeValNo(AValNo); + + DEBUG({ + dbgs() << " result = "; + IntA.print(dbgs(), tri_); + dbgs() << '\n'; + }); + + ++numCommutes; + return true; +} + +/// isSameOrFallThroughBB - Return true if MBB == SuccMBB or MBB simply +/// fallthoughs to SuccMBB. +static bool isSameOrFallThroughBB(MachineBasicBlock *MBB, + MachineBasicBlock *SuccMBB, + const TargetInstrInfo *tii_) { + if (MBB == SuccMBB) + return true; + MachineBasicBlock *TBB = 0, *FBB = 0; + SmallVector<MachineOperand, 4> Cond; + return !tii_->AnalyzeBranch(*MBB, TBB, FBB, Cond) && !TBB && !FBB && + MBB->isSuccessor(SuccMBB); +} + +/// removeRange - Wrapper for LiveInterval::removeRange. This removes a range +/// from a physical register live interval as well as from the live intervals +/// of its sub-registers. +static void removeRange(LiveInterval &li, + SlotIndex Start, SlotIndex End, + LiveIntervals *li_, const TargetRegisterInfo *tri_) { + li.removeRange(Start, End, true); + if (TargetRegisterInfo::isPhysicalRegister(li.reg)) { + for (const unsigned* SR = tri_->getSubRegisters(li.reg); *SR; ++SR) { + if (!li_->hasInterval(*SR)) + continue; + LiveInterval &sli = li_->getInterval(*SR); + SlotIndex RemoveStart = Start; + SlotIndex RemoveEnd = Start; + + while (RemoveEnd != End) { + LiveInterval::iterator LR = sli.FindLiveRangeContaining(RemoveStart); + if (LR == sli.end()) + break; + RemoveEnd = (LR->end < End) ? LR->end : End; + sli.removeRange(RemoveStart, RemoveEnd, true); + RemoveStart = RemoveEnd; + } + } + } +} + +/// TrimLiveIntervalToLastUse - If there is a last use in the same basic block +/// as the copy instruction, trim the live interval to the last use and return +/// true. +bool +SimpleRegisterCoalescing::TrimLiveIntervalToLastUse(SlotIndex CopyIdx, + MachineBasicBlock *CopyMBB, + LiveInterval &li, + const LiveRange *LR) { + SlotIndex MBBStart = li_->getMBBStartIdx(CopyMBB); + SlotIndex LastUseIdx; + MachineOperand *LastUse = + lastRegisterUse(LR->start, CopyIdx.getPrevSlot(), li.reg, LastUseIdx); + if (LastUse) { + MachineInstr *LastUseMI = LastUse->getParent(); + if (!isSameOrFallThroughBB(LastUseMI->getParent(), CopyMBB, tii_)) { + // r1024 = op + // ... + // BB1: + // = r1024 + // + // BB2: + // r1025<dead> = r1024<kill> + if (MBBStart < LR->end) + removeRange(li, MBBStart, LR->end, li_, tri_); + return true; + } + + // There are uses before the copy, just shorten the live range to the end + // of last use. + LastUse->setIsKill(); + removeRange(li, LastUseIdx.getDefIndex(), LR->end, li_, tri_); + if (LastUseMI->isCopy()) { + MachineOperand &DefMO = LastUseMI->getOperand(0); + if (DefMO.getReg() == li.reg && !DefMO.getSubReg()) + DefMO.setIsDead(); + } + unsigned SrcReg, DstReg, SrcSubIdx, DstSubIdx; + if (tii_->isMoveInstr(*LastUseMI, SrcReg, DstReg, SrcSubIdx, DstSubIdx) && + DstReg == li.reg && DstSubIdx == 0) { + // Last use is itself an identity code. + int DeadIdx = LastUseMI->findRegisterDefOperandIdx(li.reg, + false, false, tri_); + LastUseMI->getOperand(DeadIdx).setIsDead(); + } + return true; + } + + // Is it livein? + if (LR->start <= MBBStart && LR->end > MBBStart) { + if (LR->start == li_->getZeroIndex()) { + assert(TargetRegisterInfo::isPhysicalRegister(li.reg)); + // Live-in to the function but dead. Remove it from entry live-in set. + mf_->begin()->removeLiveIn(li.reg); + } + // FIXME: Shorten intervals in BBs that reaches this BB. + } + + return false; +} + +/// ReMaterializeTrivialDef - If the source of a copy is defined by a trivial +/// computation, replace the copy by rematerialize the definition. +bool SimpleRegisterCoalescing::ReMaterializeTrivialDef(LiveInterval &SrcInt, + unsigned DstReg, + unsigned DstSubIdx, + MachineInstr *CopyMI) { + SlotIndex CopyIdx = li_->getInstructionIndex(CopyMI).getUseIndex(); + LiveInterval::iterator SrcLR = SrcInt.FindLiveRangeContaining(CopyIdx); + assert(SrcLR != SrcInt.end() && "Live range not found!"); + VNInfo *ValNo = SrcLR->valno; + // If other defs can reach uses of this def, then it's not safe to perform + // the optimization. FIXME: Do isPHIDef and isDefAccurate both need to be + // tested? + if (ValNo->isPHIDef() || !ValNo->isDefAccurate() || + ValNo->isUnused() || ValNo->hasPHIKill()) + return false; + MachineInstr *DefMI = li_->getInstructionFromIndex(ValNo->def); + assert(DefMI && "Defining instruction disappeared"); + const TargetInstrDesc &TID = DefMI->getDesc(); + if (!TID.isAsCheapAsAMove()) + return false; + if (!tii_->isTriviallyReMaterializable(DefMI, AA)) + return false; + bool SawStore = false; + if (!DefMI->isSafeToMove(tii_, AA, SawStore)) + return false; + if (TID.getNumDefs() != 1) + return false; + if (!DefMI->isImplicitDef()) { + // Make sure the copy destination register class fits the instruction + // definition register class. The mismatch can happen as a result of earlier + // extract_subreg, insert_subreg, subreg_to_reg coalescing. + const TargetRegisterClass *RC = TID.OpInfo[0].getRegClass(tri_); + if (TargetRegisterInfo::isVirtualRegister(DstReg)) { + if (mri_->getRegClass(DstReg) != RC) + return false; + } else if (!RC->contains(DstReg)) + return false; + } + + // If destination register has a sub-register index on it, make sure it mtches + // the instruction register class. + if (DstSubIdx) { + const TargetInstrDesc &TID = DefMI->getDesc(); + if (TID.getNumDefs() != 1) + return false; + const TargetRegisterClass *DstRC = mri_->getRegClass(DstReg); + const TargetRegisterClass *DstSubRC = + DstRC->getSubRegisterRegClass(DstSubIdx); + const TargetRegisterClass *DefRC = TID.OpInfo[0].getRegClass(tri_); + if (DefRC == DstRC) + DstSubIdx = 0; + else if (DefRC != DstSubRC) + return false; + } + + RemoveCopyFlag(DstReg, CopyMI); + + // If copy kills the source register, find the last use and propagate + // kill. + bool checkForDeadDef = false; + MachineBasicBlock *MBB = CopyMI->getParent(); + if (SrcLR->end == CopyIdx.getDefIndex()) + if (!TrimLiveIntervalToLastUse(CopyIdx, MBB, SrcInt, SrcLR)) { + checkForDeadDef = true; + } + + MachineBasicBlock::iterator MII = + llvm::next(MachineBasicBlock::iterator(CopyMI)); + tii_->reMaterialize(*MBB, MII, DstReg, DstSubIdx, DefMI, *tri_); + MachineInstr *NewMI = prior(MII); + + if (checkForDeadDef) { + // PR4090 fix: Trim interval failed because there was no use of the + // source interval in this MBB. If the def is in this MBB too then we + // should mark it dead: + if (DefMI->getParent() == MBB) { + DefMI->addRegisterDead(SrcInt.reg, tri_); + SrcLR->end = SrcLR->start.getNextSlot(); + } + } + + // CopyMI may have implicit operands, transfer them over to the newly + // rematerialized instruction. And update implicit def interval valnos. + for (unsigned i = CopyMI->getDesc().getNumOperands(), + e = CopyMI->getNumOperands(); i != e; ++i) { + MachineOperand &MO = CopyMI->getOperand(i); + if (MO.isReg() && MO.isImplicit()) + NewMI->addOperand(MO); + if (MO.isDef()) + RemoveCopyFlag(MO.getReg(), CopyMI); + } + + TransferImplicitOps(CopyMI, NewMI); + li_->ReplaceMachineInstrInMaps(CopyMI, NewMI); + CopyMI->eraseFromParent(); + ReMatCopies.insert(CopyMI); + ReMatDefs.insert(DefMI); + DEBUG(dbgs() << "Remat: " << *NewMI); + ++NumReMats; + return true; +} + +/// UpdateRegDefsUses - Replace all defs and uses of SrcReg to DstReg and +/// update the subregister number if it is not zero. If DstReg is a +/// physical register and the existing subregister number of the def / use +/// being updated is not zero, make sure to set it to the correct physical +/// subregister. +void +SimpleRegisterCoalescing::UpdateRegDefsUses(const CoalescerPair &CP) { + bool DstIsPhys = CP.isPhys(); + unsigned SrcReg = CP.getSrcReg(); + unsigned DstReg = CP.getDstReg(); + unsigned SubIdx = CP.getSubIdx(); + + for (MachineRegisterInfo::reg_iterator I = mri_->reg_begin(SrcReg); + MachineInstr *UseMI = I.skipInstruction();) { + // A PhysReg copy that won't be coalesced can perhaps be rematerialized + // instead. + if (DstIsPhys) { + unsigned CopySrcReg, CopyDstReg, CopySrcSubIdx, CopyDstSubIdx; + if (tii_->isMoveInstr(*UseMI, CopySrcReg, CopyDstReg, + CopySrcSubIdx, CopyDstSubIdx) && + CopySrcSubIdx == 0 && CopyDstSubIdx == 0 && + CopySrcReg != CopyDstReg && CopySrcReg == SrcReg && + CopyDstReg != DstReg && !JoinedCopies.count(UseMI) && + ReMaterializeTrivialDef(li_->getInterval(SrcReg), CopyDstReg, 0, + UseMI)) + continue; + + if (UseMI->isCopy() && + !UseMI->getOperand(1).getSubReg() && + !UseMI->getOperand(0).getSubReg() && + UseMI->getOperand(1).getReg() == SrcReg && + UseMI->getOperand(0).getReg() != SrcReg && + UseMI->getOperand(0).getReg() != DstReg && + !JoinedCopies.count(UseMI) && + ReMaterializeTrivialDef(li_->getInterval(SrcReg), + UseMI->getOperand(0).getReg(), 0, UseMI)) + continue; + } + + SmallVector<unsigned,8> Ops; + bool Reads, Writes; + tie(Reads, Writes) = UseMI->readsWritesVirtualRegister(SrcReg, &Ops); + bool Kills = false, Deads = false; + + // Replace SrcReg with DstReg in all UseMI operands. + for (unsigned i = 0, e = Ops.size(); i != e; ++i) { + MachineOperand &MO = UseMI->getOperand(Ops[i]); + Kills |= MO.isKill(); + Deads |= MO.isDead(); + + if (DstIsPhys) + MO.substPhysReg(DstReg, *tri_); + else + MO.substVirtReg(DstReg, SubIdx, *tri_); + } + + // This instruction is a copy that will be removed. + if (JoinedCopies.count(UseMI)) + continue; + + if (SubIdx) { + // If UseMI was a simple SrcReg def, make sure we didn't turn it into a + // read-modify-write of DstReg. + if (Deads) + UseMI->addRegisterDead(DstReg, tri_); + else if (!Reads && Writes) + UseMI->addRegisterDefined(DstReg, tri_); + + // Kill flags apply to the whole physical register. + if (DstIsPhys && Kills) + UseMI->addRegisterKilled(DstReg, tri_); + } + + DEBUG({ + dbgs() << "\t\tupdated: "; + if (!UseMI->isDebugValue()) + dbgs() << li_->getInstructionIndex(UseMI) << "\t"; + dbgs() << *UseMI; + }); + + + // After updating the operand, check if the machine instruction has + // become a copy. If so, update its val# information. + const TargetInstrDesc &TID = UseMI->getDesc(); + if (DstIsPhys || TID.getNumDefs() != 1 || TID.getNumOperands() <= 2) + continue; + + unsigned CopySrcReg, CopyDstReg, CopySrcSubIdx, CopyDstSubIdx; + if (tii_->isMoveInstr(*UseMI, CopySrcReg, CopyDstReg, + CopySrcSubIdx, CopyDstSubIdx) && + CopySrcReg != CopyDstReg && + (TargetRegisterInfo::isVirtualRegister(CopyDstReg) || + allocatableRegs_[CopyDstReg])) { + LiveInterval &LI = li_->getInterval(CopyDstReg); + SlotIndex DefIdx = + li_->getInstructionIndex(UseMI).getDefIndex(); + if (const LiveRange *DLR = LI.getLiveRangeContaining(DefIdx)) { + if (DLR->valno->def == DefIdx) + DLR->valno->setCopy(UseMI); + } + } + } +} + +/// removeIntervalIfEmpty - Check if the live interval of a physical register +/// is empty, if so remove it and also remove the empty intervals of its +/// sub-registers. Return true if live interval is removed. +static bool removeIntervalIfEmpty(LiveInterval &li, LiveIntervals *li_, + const TargetRegisterInfo *tri_) { + if (li.empty()) { + if (TargetRegisterInfo::isPhysicalRegister(li.reg)) + for (const unsigned* SR = tri_->getSubRegisters(li.reg); *SR; ++SR) { + if (!li_->hasInterval(*SR)) + continue; + LiveInterval &sli = li_->getInterval(*SR); + if (sli.empty()) + li_->removeInterval(*SR); + } + li_->removeInterval(li.reg); + return true; + } + return false; +} + +/// ShortenDeadCopyLiveRange - Shorten a live range defined by a dead copy. +/// Return true if live interval is removed. +bool SimpleRegisterCoalescing::ShortenDeadCopyLiveRange(LiveInterval &li, + MachineInstr *CopyMI) { + SlotIndex CopyIdx = li_->getInstructionIndex(CopyMI); + LiveInterval::iterator MLR = + li.FindLiveRangeContaining(CopyIdx.getDefIndex()); + if (MLR == li.end()) + return false; // Already removed by ShortenDeadCopySrcLiveRange. + SlotIndex RemoveStart = MLR->start; + SlotIndex RemoveEnd = MLR->end; + SlotIndex DefIdx = CopyIdx.getDefIndex(); + // Remove the liverange that's defined by this. + if (RemoveStart == DefIdx && RemoveEnd == DefIdx.getStoreIndex()) { + removeRange(li, RemoveStart, RemoveEnd, li_, tri_); + return removeIntervalIfEmpty(li, li_, tri_); + } + return false; +} + +/// RemoveDeadDef - If a def of a live interval is now determined dead, remove +/// the val# it defines. If the live interval becomes empty, remove it as well. +bool SimpleRegisterCoalescing::RemoveDeadDef(LiveInterval &li, + MachineInstr *DefMI) { + SlotIndex DefIdx = li_->getInstructionIndex(DefMI).getDefIndex(); + LiveInterval::iterator MLR = li.FindLiveRangeContaining(DefIdx); + if (DefIdx != MLR->valno->def) + return false; + li.removeValNo(MLR->valno); + return removeIntervalIfEmpty(li, li_, tri_); +} + +void SimpleRegisterCoalescing::RemoveCopyFlag(unsigned DstReg, + const MachineInstr *CopyMI) { + SlotIndex DefIdx = li_->getInstructionIndex(CopyMI).getDefIndex(); + if (li_->hasInterval(DstReg)) { + LiveInterval &LI = li_->getInterval(DstReg); + if (const LiveRange *LR = LI.getLiveRangeContaining(DefIdx)) + if (LR->valno->getCopy() == CopyMI) + LR->valno->setCopy(0); + } + if (!TargetRegisterInfo::isPhysicalRegister(DstReg)) + return; + for (const unsigned* AS = tri_->getAliasSet(DstReg); *AS; ++AS) { + if (!li_->hasInterval(*AS)) + continue; + LiveInterval &LI = li_->getInterval(*AS); + if (const LiveRange *LR = LI.getLiveRangeContaining(DefIdx)) + if (LR->valno->getCopy() == CopyMI) + LR->valno->setCopy(0); + } +} + +/// PropagateDeadness - Propagate the dead marker to the instruction which +/// defines the val#. +static void PropagateDeadness(LiveInterval &li, MachineInstr *CopyMI, + SlotIndex &LRStart, LiveIntervals *li_, + const TargetRegisterInfo* tri_) { + MachineInstr *DefMI = + li_->getInstructionFromIndex(LRStart.getDefIndex()); + if (DefMI && DefMI != CopyMI) { + int DeadIdx = DefMI->findRegisterDefOperandIdx(li.reg); + if (DeadIdx != -1) + DefMI->getOperand(DeadIdx).setIsDead(); + else + DefMI->addOperand(MachineOperand::CreateReg(li.reg, + /*def*/true, /*implicit*/true, /*kill*/false, /*dead*/true)); + LRStart = LRStart.getNextSlot(); + } +} + +/// ShortenDeadCopySrcLiveRange - Shorten a live range as it's artificially +/// extended by a dead copy. Mark the last use (if any) of the val# as kill as +/// ends the live range there. If there isn't another use, then this live range +/// is dead. Return true if live interval is removed. +bool +SimpleRegisterCoalescing::ShortenDeadCopySrcLiveRange(LiveInterval &li, + MachineInstr *CopyMI) { + SlotIndex CopyIdx = li_->getInstructionIndex(CopyMI); + if (CopyIdx == SlotIndex()) { + // FIXME: special case: function live in. It can be a general case if the + // first instruction index starts at > 0 value. + assert(TargetRegisterInfo::isPhysicalRegister(li.reg)); + // Live-in to the function but dead. Remove it from entry live-in set. + if (mf_->begin()->isLiveIn(li.reg)) + mf_->begin()->removeLiveIn(li.reg); + if (const LiveRange *LR = li.getLiveRangeContaining(CopyIdx)) + removeRange(li, LR->start, LR->end, li_, tri_); + return removeIntervalIfEmpty(li, li_, tri_); + } + + LiveInterval::iterator LR = + li.FindLiveRangeContaining(CopyIdx.getPrevIndex().getStoreIndex()); + if (LR == li.end()) + // Livein but defined by a phi. + return false; + + SlotIndex RemoveStart = LR->start; + SlotIndex RemoveEnd = CopyIdx.getStoreIndex(); + if (LR->end > RemoveEnd) + // More uses past this copy? Nothing to do. + return false; + + // If there is a last use in the same bb, we can't remove the live range. + // Shorten the live interval and return. + MachineBasicBlock *CopyMBB = CopyMI->getParent(); + if (TrimLiveIntervalToLastUse(CopyIdx, CopyMBB, li, LR)) + return false; + + // There are other kills of the val#. Nothing to do. + if (!li.isOnlyLROfValNo(LR)) + return false; + + MachineBasicBlock *StartMBB = li_->getMBBFromIndex(RemoveStart); + if (!isSameOrFallThroughBB(StartMBB, CopyMBB, tii_)) + // If the live range starts in another mbb and the copy mbb is not a fall + // through mbb, then we can only cut the range from the beginning of the + // copy mbb. + RemoveStart = li_->getMBBStartIdx(CopyMBB).getNextIndex().getBaseIndex(); + + if (LR->valno->def == RemoveStart) { + // If the def MI defines the val# and this copy is the only kill of the + // val#, then propagate the dead marker. + PropagateDeadness(li, CopyMI, RemoveStart, li_, tri_); + ++numDeadValNo; + } + + removeRange(li, RemoveStart, RemoveEnd, li_, tri_); + return removeIntervalIfEmpty(li, li_, tri_); +} + + +/// isWinToJoinCrossClass - Return true if it's profitable to coalesce +/// two virtual registers from different register classes. +bool +SimpleRegisterCoalescing::isWinToJoinCrossClass(unsigned SrcReg, + unsigned DstReg, + const TargetRegisterClass *SrcRC, + const TargetRegisterClass *DstRC, + const TargetRegisterClass *NewRC) { + unsigned NewRCCount = allocatableRCRegs_[NewRC].count(); + // This heuristics is good enough in practice, but it's obviously not *right*. + // 4 is a magic number that works well enough for x86, ARM, etc. It filter + // out all but the most restrictive register classes. + if (NewRCCount > 4 || + // Early exit if the function is fairly small, coalesce aggressively if + // that's the case. For really special register classes with 3 or + // fewer registers, be a bit more careful. + (li_->getFuncInstructionCount() / NewRCCount) < 8) + return true; + LiveInterval &SrcInt = li_->getInterval(SrcReg); + LiveInterval &DstInt = li_->getInterval(DstReg); + unsigned SrcSize = li_->getApproximateInstructionCount(SrcInt); + unsigned DstSize = li_->getApproximateInstructionCount(DstInt); + if (SrcSize <= NewRCCount && DstSize <= NewRCCount) + return true; + // Estimate *register use density*. If it doubles or more, abort. + unsigned SrcUses = std::distance(mri_->use_nodbg_begin(SrcReg), + mri_->use_nodbg_end()); + unsigned DstUses = std::distance(mri_->use_nodbg_begin(DstReg), + mri_->use_nodbg_end()); + unsigned NewUses = SrcUses + DstUses; + unsigned NewSize = SrcSize + DstSize; + if (SrcRC != NewRC && SrcSize > NewRCCount) { + unsigned SrcRCCount = allocatableRCRegs_[SrcRC].count(); + if (NewUses*SrcSize*SrcRCCount > 2*SrcUses*NewSize*NewRCCount) + return false; + } + if (DstRC != NewRC && DstSize > NewRCCount) { + unsigned DstRCCount = allocatableRCRegs_[DstRC].count(); + if (NewUses*DstSize*DstRCCount > 2*DstUses*NewSize*NewRCCount) + return false; + } + return true; +} + + +/// JoinCopy - Attempt to join intervals corresponding to SrcReg/DstReg, +/// which are the src/dst of the copy instruction CopyMI. This returns true +/// if the copy was successfully coalesced away. If it is not currently +/// possible to coalesce this interval, but it may be possible if other +/// things get coalesced, then it returns true by reference in 'Again'. +bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) { + MachineInstr *CopyMI = TheCopy.MI; + + Again = false; + if (JoinedCopies.count(CopyMI) || ReMatCopies.count(CopyMI)) + return false; // Already done. + + DEBUG(dbgs() << li_->getInstructionIndex(CopyMI) << '\t' << *CopyMI); + + CoalescerPair CP(*tii_, *tri_); + if (!CP.setRegisters(CopyMI)) { + DEBUG(dbgs() << "\tNot coalescable.\n"); + return false; + } + + // If they are already joined we continue. + if (CP.getSrcReg() == CP.getDstReg()) { + DEBUG(dbgs() << "\tCopy already coalesced.\n"); + return false; // Not coalescable. + } + + DEBUG(dbgs() << "\tConsidering merging %reg" << CP.getSrcReg()); + + // Enforce policies. + if (CP.isPhys()) { + DEBUG(dbgs() <<" with physreg %" << tri_->getName(CP.getDstReg()) << "\n"); + // Only coalesce to allocatable physreg. + if (!allocatableRegs_[CP.getDstReg()]) { + DEBUG(dbgs() << "\tRegister is an unallocatable physreg.\n"); + return false; // Not coalescable. + } + } else { + DEBUG({ + dbgs() << " with reg%" << CP.getDstReg(); + if (CP.getSubIdx()) + dbgs() << ":" << tri_->getSubRegIndexName(CP.getSubIdx()); + dbgs() << " to " << CP.getNewRC()->getName() << "\n"; + }); + + // Avoid constraining virtual register regclass too much. + if (CP.isCrossClass()) { + if (DisableCrossClassJoin) { + DEBUG(dbgs() << "\tCross-class joins disabled.\n"); + return false; + } + if (!isWinToJoinCrossClass(CP.getSrcReg(), CP.getDstReg(), + mri_->getRegClass(CP.getSrcReg()), + mri_->getRegClass(CP.getDstReg()), + CP.getNewRC())) { + DEBUG(dbgs() << "\tAvoid coalescing to constrained register class: " + << CP.getNewRC()->getName() << ".\n"); + Again = true; // May be possible to coalesce later. + return false; + } + } + + // When possible, let DstReg be the larger interval. + if (!CP.getSubIdx() && li_->getInterval(CP.getSrcReg()).ranges.size() > + li_->getInterval(CP.getDstReg()).ranges.size()) + CP.flip(); + } + + // We need to be careful about coalescing a source physical register with a + // virtual register. Once the coalescing is done, it cannot be broken and + // these are not spillable! If the destination interval uses are far away, + // think twice about coalescing them! + // FIXME: Why are we skipping this test for partial copies? + // CodeGen/X86/phys_subreg_coalesce-3.ll needs it. + if (!CP.isPartial() && CP.isPhys()) { + LiveInterval &JoinVInt = li_->getInterval(CP.getSrcReg()); + + // Don't join with physregs that have a ridiculous number of live + // ranges. The data structure performance is really bad when that + // happens. + if (li_->hasInterval(CP.getDstReg()) && + li_->getInterval(CP.getDstReg()).ranges.size() > 1000) { + mri_->setRegAllocationHint(CP.getSrcReg(), 0, CP.getDstReg()); + ++numAborts; + DEBUG(dbgs() + << "\tPhysical register live interval too complicated, abort!\n"); + return false; + } + + const TargetRegisterClass *RC = mri_->getRegClass(CP.getSrcReg()); + unsigned Threshold = allocatableRCRegs_[RC].count() * 2; + unsigned Length = li_->getApproximateInstructionCount(JoinVInt); + if (Length > Threshold && + std::distance(mri_->use_nodbg_begin(CP.getSrcReg()), + mri_->use_nodbg_end()) * Threshold < Length) { + // Before giving up coalescing, if definition of source is defined by + // trivial computation, try rematerializing it. + if (!CP.isFlipped() && + ReMaterializeTrivialDef(JoinVInt, CP.getDstReg(), 0, CopyMI)) + return true; + + mri_->setRegAllocationHint(CP.getSrcReg(), 0, CP.getDstReg()); + ++numAborts; + DEBUG(dbgs() << "\tMay tie down a physical register, abort!\n"); + Again = true; // May be possible to coalesce later. + return false; + } + } + + // Okay, attempt to join these two intervals. On failure, this returns false. + // Otherwise, if one of the intervals being joined is a physreg, this method + // always canonicalizes DstInt to be it. The output "SrcInt" will not have + // been modified, so we can use this information below to update aliases. + if (!JoinIntervals(CP)) { + // Coalescing failed. + + // If definition of source is defined by trivial computation, try + // rematerializing it. + if (!CP.isFlipped() && + ReMaterializeTrivialDef(li_->getInterval(CP.getSrcReg()), + CP.getDstReg(), 0, CopyMI)) + return true; + + // If we can eliminate the copy without merging the live ranges, do so now. + if (!CP.isPartial()) { + if (AdjustCopiesBackFrom(CP, CopyMI) || + RemoveCopyByCommutingDef(CP, CopyMI)) { + JoinedCopies.insert(CopyMI); + DEBUG(dbgs() << "\tTrivial!\n"); + return true; + } + } + + // Otherwise, we are unable to join the intervals. + DEBUG(dbgs() << "\tInterference!\n"); + Again = true; // May be possible to coalesce later. + return false; + } + + // Coalescing to a virtual register that is of a sub-register class of the + // other. Make sure the resulting register is set to the right register class. + if (CP.isCrossClass()) { + ++numCrossRCs; + mri_->setRegClass(CP.getDstReg(), CP.getNewRC()); + } + + // Remember to delete the copy instruction. + JoinedCopies.insert(CopyMI); + + UpdateRegDefsUses(CP); + + // If we have extended the live range of a physical register, make sure we + // update live-in lists as well. + if (CP.isPhys()) { + SmallVector<MachineBasicBlock*, 16> BlockSeq; + // JoinIntervals invalidates the VNInfos in SrcInt, but we only need the + // ranges for this, and they are preserved. + LiveInterval &SrcInt = li_->getInterval(CP.getSrcReg()); + for (LiveInterval::const_iterator I = SrcInt.begin(), E = SrcInt.end(); + I != E; ++I ) { + li_->findLiveInMBBs(I->start, I->end, BlockSeq); + for (unsigned idx = 0, size = BlockSeq.size(); idx != size; ++idx) { + MachineBasicBlock &block = *BlockSeq[idx]; + if (!block.isLiveIn(CP.getDstReg())) + block.addLiveIn(CP.getDstReg()); + } + BlockSeq.clear(); + } + } + + // SrcReg is guarateed to be the register whose live interval that is + // being merged. + li_->removeInterval(CP.getSrcReg()); + + // Update regalloc hint. + tri_->UpdateRegAllocHint(CP.getSrcReg(), CP.getDstReg(), *mf_); + + DEBUG({ + LiveInterval &DstInt = li_->getInterval(CP.getDstReg()); + dbgs() << "\tJoined. Result = "; + DstInt.print(dbgs(), tri_); + dbgs() << "\n"; + }); + + ++numJoins; + return true; +} + +/// ComputeUltimateVN - Assuming we are going to join two live intervals, +/// compute what the resultant value numbers for each value in the input two +/// ranges will be. This is complicated by copies between the two which can +/// and will commonly cause multiple value numbers to be merged into one. +/// +/// VN is the value number that we're trying to resolve. InstDefiningValue +/// keeps track of the new InstDefiningValue assignment for the result +/// LiveInterval. ThisFromOther/OtherFromThis are sets that keep track of +/// whether a value in this or other is a copy from the opposite set. +/// ThisValNoAssignments/OtherValNoAssignments keep track of value #'s that have +/// already been assigned. +/// +/// ThisFromOther[x] - If x is defined as a copy from the other interval, this +/// contains the value number the copy is from. +/// +static unsigned ComputeUltimateVN(VNInfo *VNI, + SmallVector<VNInfo*, 16> &NewVNInfo, + DenseMap<VNInfo*, VNInfo*> &ThisFromOther, + DenseMap<VNInfo*, VNInfo*> &OtherFromThis, + SmallVector<int, 16> &ThisValNoAssignments, + SmallVector<int, 16> &OtherValNoAssignments) { + unsigned VN = VNI->id; + + // If the VN has already been computed, just return it. + if (ThisValNoAssignments[VN] >= 0) + return ThisValNoAssignments[VN]; + assert(ThisValNoAssignments[VN] != -2 && "Cyclic value numbers"); + + // If this val is not a copy from the other val, then it must be a new value + // number in the destination. + DenseMap<VNInfo*, VNInfo*>::iterator I = ThisFromOther.find(VNI); + if (I == ThisFromOther.end()) { + NewVNInfo.push_back(VNI); + return ThisValNoAssignments[VN] = NewVNInfo.size()-1; + } + VNInfo *OtherValNo = I->second; + + // Otherwise, this *is* a copy from the RHS. If the other side has already + // been computed, return it. + if (OtherValNoAssignments[OtherValNo->id] >= 0) + return ThisValNoAssignments[VN] = OtherValNoAssignments[OtherValNo->id]; + + // Mark this value number as currently being computed, then ask what the + // ultimate value # of the other value is. + ThisValNoAssignments[VN] = -2; + unsigned UltimateVN = + ComputeUltimateVN(OtherValNo, NewVNInfo, OtherFromThis, ThisFromOther, + OtherValNoAssignments, ThisValNoAssignments); + return ThisValNoAssignments[VN] = UltimateVN; +} + +/// JoinIntervals - Attempt to join these two intervals. On failure, this +/// returns false. +bool SimpleRegisterCoalescing::JoinIntervals(CoalescerPair &CP) { + LiveInterval &RHS = li_->getInterval(CP.getSrcReg()); + DEBUG({ dbgs() << "\t\tRHS = "; RHS.print(dbgs(), tri_); dbgs() << "\n"; }); + + // If a live interval is a physical register, check for interference with any + // aliases. The interference check implemented here is a bit more conservative + // than the full interfeence check below. We allow overlapping live ranges + // only when one is a copy of the other. + if (CP.isPhys()) { + for (const unsigned *AS = tri_->getAliasSet(CP.getDstReg()); *AS; ++AS){ + if (!li_->hasInterval(*AS)) + continue; + const LiveInterval &LHS = li_->getInterval(*AS); + LiveInterval::const_iterator LI = LHS.begin(); + for (LiveInterval::const_iterator RI = RHS.begin(), RE = RHS.end(); + RI != RE; ++RI) { + LI = std::lower_bound(LI, LHS.end(), RI->start); + // Does LHS have an overlapping live range starting before RI? + if ((LI != LHS.begin() && LI[-1].end > RI->start) && + (RI->start != RI->valno->def || + !CP.isCoalescable(li_->getInstructionFromIndex(RI->start)))) { + DEBUG({ + dbgs() << "\t\tInterference from alias: "; + LHS.print(dbgs(), tri_); + dbgs() << "\n\t\tOverlap at " << RI->start << " and no copy.\n"; + }); + return false; + } + + // Check that LHS ranges beginning in this range are copies. + for (; LI != LHS.end() && LI->start < RI->end; ++LI) { + if (LI->start != LI->valno->def || + !CP.isCoalescable(li_->getInstructionFromIndex(LI->start))) { + DEBUG({ + dbgs() << "\t\tInterference from alias: "; + LHS.print(dbgs(), tri_); + dbgs() << "\n\t\tDef at " << LI->start << " is not a copy.\n"; + }); + return false; + } + } + } + } + } + + // Compute the final value assignment, assuming that the live ranges can be + // coalesced. + SmallVector<int, 16> LHSValNoAssignments; + SmallVector<int, 16> RHSValNoAssignments; + DenseMap<VNInfo*, VNInfo*> LHSValsDefinedFromRHS; + DenseMap<VNInfo*, VNInfo*> RHSValsDefinedFromLHS; + SmallVector<VNInfo*, 16> NewVNInfo; + + LiveInterval &LHS = li_->getOrCreateInterval(CP.getDstReg()); + DEBUG({ dbgs() << "\t\tLHS = "; LHS.print(dbgs(), tri_); dbgs() << "\n"; }); + + // Loop over the value numbers of the LHS, seeing if any are defined from + // the RHS. + for (LiveInterval::vni_iterator i = LHS.vni_begin(), e = LHS.vni_end(); + i != e; ++i) { + VNInfo *VNI = *i; + if (VNI->isUnused() || VNI->getCopy() == 0) // Src not defined by a copy? + continue; + + // Never join with a register that has EarlyClobber redefs. + if (VNI->hasRedefByEC()) + return false; + + // DstReg is known to be a register in the LHS interval. If the src is + // from the RHS interval, we can use its value #. + if (!CP.isCoalescable(VNI->getCopy())) + continue; + + // Figure out the value # from the RHS. + LiveRange *lr = RHS.getLiveRangeContaining(VNI->def.getPrevSlot()); + // The copy could be to an aliased physreg. + if (!lr) continue; + LHSValsDefinedFromRHS[VNI] = lr->valno; + } + + // Loop over the value numbers of the RHS, seeing if any are defined from + // the LHS. + for (LiveInterval::vni_iterator i = RHS.vni_begin(), e = RHS.vni_end(); + i != e; ++i) { + VNInfo *VNI = *i; + if (VNI->isUnused() || VNI->getCopy() == 0) // Src not defined by a copy? + continue; + + // Never join with a register that has EarlyClobber redefs. + if (VNI->hasRedefByEC()) + return false; + + // DstReg is known to be a register in the RHS interval. If the src is + // from the LHS interval, we can use its value #. + if (!CP.isCoalescable(VNI->getCopy())) + continue; + + // Figure out the value # from the LHS. + LiveRange *lr = LHS.getLiveRangeContaining(VNI->def.getPrevSlot()); + // The copy could be to an aliased physreg. + if (!lr) continue; + RHSValsDefinedFromLHS[VNI] = lr->valno; + } + + LHSValNoAssignments.resize(LHS.getNumValNums(), -1); + RHSValNoAssignments.resize(RHS.getNumValNums(), -1); + NewVNInfo.reserve(LHS.getNumValNums() + RHS.getNumValNums()); + + for (LiveInterval::vni_iterator i = LHS.vni_begin(), e = LHS.vni_end(); + i != e; ++i) { + VNInfo *VNI = *i; + unsigned VN = VNI->id; + if (LHSValNoAssignments[VN] >= 0 || VNI->isUnused()) + continue; + ComputeUltimateVN(VNI, NewVNInfo, + LHSValsDefinedFromRHS, RHSValsDefinedFromLHS, + LHSValNoAssignments, RHSValNoAssignments); + } + for (LiveInterval::vni_iterator i = RHS.vni_begin(), e = RHS.vni_end(); + i != e; ++i) { + VNInfo *VNI = *i; + unsigned VN = VNI->id; + if (RHSValNoAssignments[VN] >= 0 || VNI->isUnused()) + continue; + // If this value number isn't a copy from the LHS, it's a new number. + if (RHSValsDefinedFromLHS.find(VNI) == RHSValsDefinedFromLHS.end()) { + NewVNInfo.push_back(VNI); + RHSValNoAssignments[VN] = NewVNInfo.size()-1; + continue; + } + + ComputeUltimateVN(VNI, NewVNInfo, + RHSValsDefinedFromLHS, LHSValsDefinedFromRHS, + RHSValNoAssignments, LHSValNoAssignments); + } + + // Armed with the mappings of LHS/RHS values to ultimate values, walk the + // interval lists to see if these intervals are coalescable. + LiveInterval::const_iterator I = LHS.begin(); + LiveInterval::const_iterator IE = LHS.end(); + LiveInterval::const_iterator J = RHS.begin(); + LiveInterval::const_iterator JE = RHS.end(); + + // Skip ahead until the first place of potential sharing. + if (I != IE && J != JE) { + if (I->start < J->start) { + I = std::upper_bound(I, IE, J->start); + if (I != LHS.begin()) --I; + } else if (J->start < I->start) { + J = std::upper_bound(J, JE, I->start); + if (J != RHS.begin()) --J; + } + } + + while (I != IE && J != JE) { + // Determine if these two live ranges overlap. + bool Overlaps; + if (I->start < J->start) { + Overlaps = I->end > J->start; + } else { + Overlaps = J->end > I->start; + } + + // If so, check value # info to determine if they are really different. + if (Overlaps) { + // If the live range overlap will map to the same value number in the + // result liverange, we can still coalesce them. If not, we can't. + if (LHSValNoAssignments[I->valno->id] != + RHSValNoAssignments[J->valno->id]) + return false; + // If it's re-defined by an early clobber somewhere in the live range, + // then conservatively abort coalescing. + if (NewVNInfo[LHSValNoAssignments[I->valno->id]]->hasRedefByEC()) + return false; + } + + if (I->end < J->end) + ++I; + else + ++J; + } + + // Update kill info. Some live ranges are extended due to copy coalescing. + for (DenseMap<VNInfo*, VNInfo*>::iterator I = LHSValsDefinedFromRHS.begin(), + E = LHSValsDefinedFromRHS.end(); I != E; ++I) { + VNInfo *VNI = I->first; + unsigned LHSValID = LHSValNoAssignments[VNI->id]; + if (VNI->hasPHIKill()) + NewVNInfo[LHSValID]->setHasPHIKill(true); + } + + // Update kill info. Some live ranges are extended due to copy coalescing. + for (DenseMap<VNInfo*, VNInfo*>::iterator I = RHSValsDefinedFromLHS.begin(), + E = RHSValsDefinedFromLHS.end(); I != E; ++I) { + VNInfo *VNI = I->first; + unsigned RHSValID = RHSValNoAssignments[VNI->id]; + if (VNI->hasPHIKill()) + NewVNInfo[RHSValID]->setHasPHIKill(true); + } + + if (LHSValNoAssignments.empty()) + LHSValNoAssignments.push_back(-1); + if (RHSValNoAssignments.empty()) + RHSValNoAssignments.push_back(-1); + + // If we get here, we know that we can coalesce the live ranges. Ask the + // intervals to coalesce themselves now. + LHS.join(RHS, &LHSValNoAssignments[0], &RHSValNoAssignments[0], NewVNInfo, + mri_); + return true; +} + +namespace { + // DepthMBBCompare - Comparison predicate that sort first based on the loop + // depth of the basic block (the unsigned), and then on the MBB number. + struct DepthMBBCompare { + typedef std::pair<unsigned, MachineBasicBlock*> DepthMBBPair; + bool operator()(const DepthMBBPair &LHS, const DepthMBBPair &RHS) const { + // Deeper loops first + if (LHS.first != RHS.first) + return LHS.first > RHS.first; + + // Prefer blocks that are more connected in the CFG. This takes care of + // the most difficult copies first while intervals are short. + unsigned cl = LHS.second->pred_size() + LHS.second->succ_size(); + unsigned cr = RHS.second->pred_size() + RHS.second->succ_size(); + if (cl != cr) + return cl > cr; + + // As a last resort, sort by block number. + return LHS.second->getNumber() < RHS.second->getNumber(); + } + }; +} + +void SimpleRegisterCoalescing::CopyCoalesceInMBB(MachineBasicBlock *MBB, + std::vector<CopyRec> &TryAgain) { + DEBUG(dbgs() << MBB->getName() << ":\n"); + + std::vector<CopyRec> VirtCopies; + std::vector<CopyRec> PhysCopies; + std::vector<CopyRec> ImpDefCopies; + for (MachineBasicBlock::iterator MII = MBB->begin(), E = MBB->end(); + MII != E;) { + MachineInstr *Inst = MII++; + + // If this isn't a copy nor a extract_subreg, we can't join intervals. + unsigned SrcReg, DstReg, SrcSubIdx, DstSubIdx; + bool isInsUndef = false; + if (Inst->isCopy()) { + DstReg = Inst->getOperand(0).getReg(); + SrcReg = Inst->getOperand(1).getReg(); + } else if (Inst->isSubregToReg()) { + DstReg = Inst->getOperand(0).getReg(); + SrcReg = Inst->getOperand(2).getReg(); + } else if (!tii_->isMoveInstr(*Inst, SrcReg, DstReg, SrcSubIdx, DstSubIdx)) + continue; + + bool SrcIsPhys = TargetRegisterInfo::isPhysicalRegister(SrcReg); + bool DstIsPhys = TargetRegisterInfo::isPhysicalRegister(DstReg); + if (isInsUndef || + (li_->hasInterval(SrcReg) && li_->getInterval(SrcReg).empty())) + ImpDefCopies.push_back(CopyRec(Inst, 0)); + else if (SrcIsPhys || DstIsPhys) + PhysCopies.push_back(CopyRec(Inst, 0)); + else + VirtCopies.push_back(CopyRec(Inst, 0)); + } + + // Try coalescing implicit copies and insert_subreg <undef> first, + // followed by copies to / from physical registers, then finally copies + // from virtual registers to virtual registers. + for (unsigned i = 0, e = ImpDefCopies.size(); i != e; ++i) { + CopyRec &TheCopy = ImpDefCopies[i]; + bool Again = false; + if (!JoinCopy(TheCopy, Again)) + if (Again) + TryAgain.push_back(TheCopy); + } + for (unsigned i = 0, e = PhysCopies.size(); i != e; ++i) { + CopyRec &TheCopy = PhysCopies[i]; + bool Again = false; + if (!JoinCopy(TheCopy, Again)) + if (Again) + TryAgain.push_back(TheCopy); + } + for (unsigned i = 0, e = VirtCopies.size(); i != e; ++i) { + CopyRec &TheCopy = VirtCopies[i]; + bool Again = false; + if (!JoinCopy(TheCopy, Again)) + if (Again) + TryAgain.push_back(TheCopy); + } +} + +void SimpleRegisterCoalescing::joinIntervals() { + DEBUG(dbgs() << "********** JOINING INTERVALS ***********\n"); + + std::vector<CopyRec> TryAgainList; + if (loopInfo->empty()) { + // If there are no loops in the function, join intervals in function order. + for (MachineFunction::iterator I = mf_->begin(), E = mf_->end(); + I != E; ++I) + CopyCoalesceInMBB(I, TryAgainList); + } else { + // Otherwise, join intervals in inner loops before other intervals. + // Unfortunately we can't just iterate over loop hierarchy here because + // there may be more MBB's than BB's. Collect MBB's for sorting. + + // Join intervals in the function prolog first. We want to join physical + // registers with virtual registers before the intervals got too long. + std::vector<std::pair<unsigned, MachineBasicBlock*> > MBBs; + for (MachineFunction::iterator I = mf_->begin(), E = mf_->end();I != E;++I){ + MachineBasicBlock *MBB = I; + MBBs.push_back(std::make_pair(loopInfo->getLoopDepth(MBB), I)); + } + + // Sort by loop depth. + std::sort(MBBs.begin(), MBBs.end(), DepthMBBCompare()); + + // Finally, join intervals in loop nest order. + for (unsigned i = 0, e = MBBs.size(); i != e; ++i) + CopyCoalesceInMBB(MBBs[i].second, TryAgainList); + } + + // Joining intervals can allow other intervals to be joined. Iteratively join + // until we make no progress. + bool ProgressMade = true; + while (ProgressMade) { + ProgressMade = false; + + for (unsigned i = 0, e = TryAgainList.size(); i != e; ++i) { + CopyRec &TheCopy = TryAgainList[i]; + if (!TheCopy.MI) + continue; + + bool Again = false; + bool Success = JoinCopy(TheCopy, Again); + if (Success || !Again) { + TheCopy.MI = 0; // Mark this one as done. + ProgressMade = true; + } + } + } +} + +/// Return true if the two specified registers belong to different register +/// classes. The registers may be either phys or virt regs. +bool +SimpleRegisterCoalescing::differingRegisterClasses(unsigned RegA, + unsigned RegB) const { + // Get the register classes for the first reg. + if (TargetRegisterInfo::isPhysicalRegister(RegA)) { + assert(TargetRegisterInfo::isVirtualRegister(RegB) && + "Shouldn't consider two physregs!"); + return !mri_->getRegClass(RegB)->contains(RegA); + } + + // Compare against the regclass for the second reg. + const TargetRegisterClass *RegClassA = mri_->getRegClass(RegA); + if (TargetRegisterInfo::isVirtualRegister(RegB)) { + const TargetRegisterClass *RegClassB = mri_->getRegClass(RegB); + return RegClassA != RegClassB; + } + return !RegClassA->contains(RegB); +} + +/// lastRegisterUse - Returns the last (non-debug) use of the specific register +/// between cycles Start and End or NULL if there are no uses. +MachineOperand * +SimpleRegisterCoalescing::lastRegisterUse(SlotIndex Start, + SlotIndex End, + unsigned Reg, + SlotIndex &UseIdx) const{ + UseIdx = SlotIndex(); + if (TargetRegisterInfo::isVirtualRegister(Reg)) { + MachineOperand *LastUse = NULL; + for (MachineRegisterInfo::use_nodbg_iterator I = mri_->use_nodbg_begin(Reg), + E = mri_->use_nodbg_end(); I != E; ++I) { + MachineOperand &Use = I.getOperand(); + MachineInstr *UseMI = Use.getParent(); + if (UseMI->isIdentityCopy()) + continue; + unsigned SrcReg, DstReg, SrcSubIdx, DstSubIdx; + if (tii_->isMoveInstr(*UseMI, SrcReg, DstReg, SrcSubIdx, DstSubIdx) && + SrcReg == DstReg && SrcSubIdx == DstSubIdx) + // Ignore identity copies. + continue; + SlotIndex Idx = li_->getInstructionIndex(UseMI); + // FIXME: Should this be Idx != UseIdx? SlotIndex() will return something + // that compares higher than any other interval. + if (Idx >= Start && Idx < End && Idx >= UseIdx) { + LastUse = &Use; + UseIdx = Idx.getUseIndex(); + } + } + return LastUse; + } + + SlotIndex s = Start; + SlotIndex e = End.getPrevSlot().getBaseIndex(); + while (e >= s) { + // Skip deleted instructions + MachineInstr *MI = li_->getInstructionFromIndex(e); + while (e != SlotIndex() && e.getPrevIndex() >= s && !MI) { + e = e.getPrevIndex(); + MI = li_->getInstructionFromIndex(e); + } + if (e < s || MI == NULL) + return NULL; + + // Ignore identity copies. + unsigned SrcReg, DstReg, SrcSubIdx, DstSubIdx; + if (!MI->isIdentityCopy() && + !(tii_->isMoveInstr(*MI, SrcReg, DstReg, SrcSubIdx, DstSubIdx) && + SrcReg == DstReg && SrcSubIdx == DstSubIdx)) + for (unsigned i = 0, NumOps = MI->getNumOperands(); i != NumOps; ++i) { + MachineOperand &Use = MI->getOperand(i); + if (Use.isReg() && Use.isUse() && Use.getReg() && + tri_->regsOverlap(Use.getReg(), Reg)) { + UseIdx = e.getUseIndex(); + return &Use; + } + } + + e = e.getPrevIndex(); + } + + return NULL; +} + +void SimpleRegisterCoalescing::releaseMemory() { + JoinedCopies.clear(); + ReMatCopies.clear(); + ReMatDefs.clear(); +} + +bool SimpleRegisterCoalescing::runOnMachineFunction(MachineFunction &fn) { + mf_ = &fn; + mri_ = &fn.getRegInfo(); + tm_ = &fn.getTarget(); + tri_ = tm_->getRegisterInfo(); + tii_ = tm_->getInstrInfo(); + li_ = &getAnalysis<LiveIntervals>(); + AA = &getAnalysis<AliasAnalysis>(); + loopInfo = &getAnalysis<MachineLoopInfo>(); + + DEBUG(dbgs() << "********** SIMPLE REGISTER COALESCING **********\n" + << "********** Function: " + << ((Value*)mf_->getFunction())->getName() << '\n'); + + allocatableRegs_ = tri_->getAllocatableSet(fn); + for (TargetRegisterInfo::regclass_iterator I = tri_->regclass_begin(), + E = tri_->regclass_end(); I != E; ++I) + allocatableRCRegs_.insert(std::make_pair(*I, + tri_->getAllocatableSet(fn, *I))); + + // Join (coalesce) intervals if requested. + if (EnableJoining) { + joinIntervals(); + DEBUG({ + dbgs() << "********** INTERVALS POST JOINING **********\n"; + for (LiveIntervals::iterator I = li_->begin(), E = li_->end(); + I != E; ++I){ + I->second->print(dbgs(), tri_); + dbgs() << "\n"; + } + }); + } + + // Perform a final pass over the instructions and compute spill weights + // and remove identity moves. + SmallVector<unsigned, 4> DeadDefs; + for (MachineFunction::iterator mbbi = mf_->begin(), mbbe = mf_->end(); + mbbi != mbbe; ++mbbi) { + MachineBasicBlock* mbb = mbbi; + for (MachineBasicBlock::iterator mii = mbb->begin(), mie = mbb->end(); + mii != mie; ) { + MachineInstr *MI = mii; + unsigned SrcReg, DstReg, SrcSubIdx, DstSubIdx; + if (JoinedCopies.count(MI)) { + // Delete all coalesced copies. + bool DoDelete = true; + if (!tii_->isMoveInstr(*MI, SrcReg, DstReg, SrcSubIdx, DstSubIdx)) { + assert(MI->isCopyLike() && "Unrecognized copy instruction"); + SrcReg = MI->getOperand(MI->isSubregToReg() ? 2 : 1).getReg(); + if (TargetRegisterInfo::isPhysicalRegister(SrcReg)) + // Do not delete extract_subreg, insert_subreg of physical + // registers unless the definition is dead. e.g. + // %DO<def> = INSERT_SUBREG %D0<undef>, %S0<kill>, 1 + // or else the scavenger may complain. LowerSubregs will + // delete them later. + DoDelete = false; + } + if (MI->allDefsAreDead()) { + LiveInterval &li = li_->getInterval(SrcReg); + if (!ShortenDeadCopySrcLiveRange(li, MI)) + ShortenDeadCopyLiveRange(li, MI); + DoDelete = true; + } + if (!DoDelete) + mii = llvm::next(mii); + else { + li_->RemoveMachineInstrFromMaps(MI); + mii = mbbi->erase(mii); + ++numPeep; + } + continue; + } + + // Now check if this is a remat'ed def instruction which is now dead. + if (ReMatDefs.count(MI)) { + bool isDead = true; + for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { + const MachineOperand &MO = MI->getOperand(i); + if (!MO.isReg()) + continue; + unsigned Reg = MO.getReg(); + if (!Reg) + continue; + if (TargetRegisterInfo::isVirtualRegister(Reg)) + DeadDefs.push_back(Reg); + if (MO.isDead()) + continue; + if (TargetRegisterInfo::isPhysicalRegister(Reg) || + !mri_->use_nodbg_empty(Reg)) { + isDead = false; + break; + } + } + if (isDead) { + while (!DeadDefs.empty()) { + unsigned DeadDef = DeadDefs.back(); + DeadDefs.pop_back(); + RemoveDeadDef(li_->getInterval(DeadDef), MI); + } + li_->RemoveMachineInstrFromMaps(mii); + mii = mbbi->erase(mii); + continue; + } else + DeadDefs.clear(); + } + + // If the move will be an identity move delete it + bool isMove= tii_->isMoveInstr(*MI, SrcReg, DstReg, SrcSubIdx, DstSubIdx); + if (MI->isIdentityCopy() || + (isMove && SrcReg == DstReg && SrcSubIdx == DstSubIdx)) { + if (li_->hasInterval(SrcReg)) { + LiveInterval &RegInt = li_->getInterval(SrcReg); + // If def of this move instruction is dead, remove its live range + // from the destination register's live interval. + if (MI->allDefsAreDead()) { + if (!ShortenDeadCopySrcLiveRange(RegInt, MI)) + ShortenDeadCopyLiveRange(RegInt, MI); + } + } + li_->RemoveMachineInstrFromMaps(MI); + mii = mbbi->erase(mii); + ++numPeep; + continue; + } + + ++mii; + + // Check for now unnecessary kill flags. + if (li_->isNotInMIMap(MI)) continue; + SlotIndex DefIdx = li_->getInstructionIndex(MI).getDefIndex(); + for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { + MachineOperand &MO = MI->getOperand(i); + if (!MO.isReg() || !MO.isKill()) continue; + unsigned reg = MO.getReg(); + if (!reg || !li_->hasInterval(reg)) continue; + if (!li_->getInterval(reg).killedAt(DefIdx)) + MO.setIsKill(false); + } + } + } + + DEBUG(dump()); + return true; +} + +/// print - Implement the dump method. +void SimpleRegisterCoalescing::print(raw_ostream &O, const Module* m) const { + li_->print(O, m); +} + +RegisterCoalescer* llvm::createSimpleRegisterCoalescer() { + return new SimpleRegisterCoalescing(); +} + +// Make sure that anything that uses RegisterCoalescer pulls in this file... +DEFINING_FILE_FOR(SimpleRegisterCoalescing) |
