X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FPrologEpilogInserter.cpp;h=230a20c2a3c831d7cdc26d273121c1ef8a4505c2;hb=84c73e9b8234287c4521e6d7e27c15e77843489e;hp=2c5c8c913dee5d0ef752fcf25338e492de45a24f;hpb=752c1df73949438ef6fa86a86363ee7091aa2532;p=oota-llvm.git diff --git a/lib/CodeGen/PrologEpilogInserter.cpp b/lib/CodeGen/PrologEpilogInserter.cpp index 2c5c8c913de..230a20c2a3c 100644 --- a/lib/CodeGen/PrologEpilogInserter.cpp +++ b/lib/CodeGen/PrologEpilogInserter.cpp @@ -31,7 +31,9 @@ #include "llvm/Target/TargetRegisterInfo.h" #include "llvm/Target/TargetFrameInfo.h" #include "llvm/Target/TargetInstrInfo.h" +#include "llvm/Support/CommandLine.h" #include "llvm/Support/Compiler.h" +#include "llvm/ADT/IndexedMap.h" #include "llvm/ADT/STLExtras.h" #include @@ -51,22 +53,26 @@ FunctionPass *llvm::createPrologEpilogCodeInserter() { return new PEI(); } /// frame indexes with appropriate references. /// bool PEI::runOnMachineFunction(MachineFunction &Fn) { + const Function* F = Fn.getFunction(); const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo(); RS = TRI->requiresRegisterScavenging(Fn) ? new RegScavenger() : NULL; + FrameIndexVirtualScavenging = TRI->requiresFrameIndexScavenging(Fn); // Get MachineModuleInfo so that we can track the construction of the // frame. if (MachineModuleInfo *MMI = getAnalysisIfAvailable()) Fn.getFrameInfo()->setMachineModuleInfo(MMI); + // Calculate the MaxCallFrameSize and HasCalls variables for the function's + // frame information. Also eliminates call frame pseudo instructions. + calculateCallsInformation(Fn); + // Allow the target machine to make some adjustments to the function // e.g. UsedPhysRegs before calculateCalleeSavedRegisters. TRI->processFunctionBeforeCalleeSavedScan(Fn, RS); - // Scan the function for modified callee saved registers and insert spill - // code for any callee saved registers that are modified. Also calculate - // the MaxCallFrameSize and HasCalls variables for the function's frame - // information and eliminates call frame pseudo instructions. + // Scan the function for modified callee saved registers and insert spill code + // for any callee saved registers that are modified. calculateCalleeSavedRegisters(Fn); // Determine placement of CSR spill/restore code: @@ -78,7 +84,8 @@ bool PEI::runOnMachineFunction(MachineFunction &Fn) { placeCSRSpillsAndRestores(Fn); // Add the code to save and restore the callee saved registers - insertCSRSpillsAndRestores(Fn); + if (!F->hasFnAttr(Attribute::Naked)) + insertCSRSpillsAndRestores(Fn); // Allow the target machine to make final modifications to the function // before the frame layout is finalized. @@ -92,13 +99,20 @@ bool PEI::runOnMachineFunction(MachineFunction &Fn) { // called functions. Because of this, calculateCalleeSavedRegisters // must be called before this function in order to set the HasCalls // and MaxCallFrameSize variables. - insertPrologEpilogCode(Fn); + if (!F->hasFnAttr(Attribute::Naked)) + insertPrologEpilogCode(Fn); // Replace all MO_FrameIndex operands with physical register references // and actual offsets. // replaceFrameIndices(Fn); + // If register scavenging is needed, as we've enabled doing it as a + // post-pass, scavenge the virtual registers that frame index elimiation + // inserted. + if (TRI->requiresRegisterScavenging(Fn) && FrameIndexVirtualScavenging) + scavengeFrameVirtualRegs(Fn); + delete RS; clearAllSets(); return true; @@ -117,35 +131,24 @@ void PEI::getAnalysisUsage(AnalysisUsage &AU) const { } #endif -/// calculateCalleeSavedRegisters - Scan the function for modified callee saved -/// registers. Also calculate the MaxCallFrameSize and HasCalls variables for -/// the function's frame information and eliminates call frame pseudo -/// instructions. -/// -void PEI::calculateCalleeSavedRegisters(MachineFunction &Fn) { +/// calculateCallsInformation - Calculate the MaxCallFrameSize and HasCalls +/// variables for the function's frame information and eliminate call frame +/// pseudo instructions. +void PEI::calculateCallsInformation(MachineFunction &Fn) { const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo(); - const TargetFrameInfo *TFI = Fn.getTarget().getFrameInfo(); - // Get the callee saved register list... - const unsigned *CSRegs = RegInfo->getCalleeSavedRegs(&Fn); + unsigned MaxCallFrameSize = 0; + bool HasCalls = false; // Get the function call frame set-up and tear-down instruction opcode int FrameSetupOpcode = RegInfo->getCallFrameSetupOpcode(); int FrameDestroyOpcode = RegInfo->getCallFrameDestroyOpcode(); - // These are used to keep track the callee-save area. Initialize them. - MinCSFrameIndex = INT_MAX; - MaxCSFrameIndex = 0; - - // Early exit for targets which have no callee saved registers and no call - // frame setup/destroy pseudo instructions. - if ((CSRegs == 0 || CSRegs[0] == 0) && - FrameSetupOpcode == -1 && FrameDestroyOpcode == -1) + // Early exit for targets which have no call frame setup/destroy pseudo + // instructions. + if (FrameSetupOpcode == -1 && FrameDestroyOpcode == -1) return; - unsigned MaxCallFrameSize = 0; - bool HasCalls = false; - std::vector FrameSDOps; for (MachineFunction::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB) for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) @@ -157,31 +160,57 @@ void PEI::calculateCalleeSavedRegisters(MachineFunction &Fn) { if (Size > MaxCallFrameSize) MaxCallFrameSize = Size; HasCalls = true; FrameSDOps.push_back(I); + } else if (I->getOpcode() == TargetInstrInfo::INLINEASM) { + // An InlineAsm might be a call; assume it is to get the stack frame + // aligned correctly for calls. + HasCalls = true; } MachineFrameInfo *FFI = Fn.getFrameInfo(); FFI->setHasCalls(HasCalls); FFI->setMaxCallFrameSize(MaxCallFrameSize); - for (unsigned i = 0, e = FrameSDOps.size(); i != e; ++i) { - MachineBasicBlock::iterator I = FrameSDOps[i]; - // If call frames are not being included as part of the stack frame, - // and there is no dynamic allocation (therefore referencing frame slots - // off sp), leave the pseudo ops alone. We'll eliminate them later. + for (std::vector::iterator + i = FrameSDOps.begin(), e = FrameSDOps.end(); i != e; ++i) { + MachineBasicBlock::iterator I = *i; + + // If call frames are not being included as part of the stack frame, and + // there is no dynamic allocation (therefore referencing frame slots off + // sp), leave the pseudo ops alone. We'll eliminate them later. if (RegInfo->hasReservedCallFrame(Fn) || RegInfo->hasFP(Fn)) RegInfo->eliminateCallFramePseudoInstr(Fn, *I->getParent(), I); } +} + + +/// calculateCalleeSavedRegisters - Scan the function for modified callee saved +/// registers. +void PEI::calculateCalleeSavedRegisters(MachineFunction &Fn) { + const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo(); + const TargetFrameInfo *TFI = Fn.getTarget().getFrameInfo(); + MachineFrameInfo *FFI = Fn.getFrameInfo(); + + // Get the callee saved register list... + const unsigned *CSRegs = RegInfo->getCalleeSavedRegs(&Fn); + + // These are used to keep track the callee-save area. Initialize them. + MinCSFrameIndex = INT_MAX; + MaxCSFrameIndex = 0; + + // Early exit for targets which have no callee saved registers. + if (CSRegs == 0 || CSRegs[0] == 0) + return; - // Now figure out which *callee saved* registers are modified by the current + // Figure out which *callee saved* registers are modified by the current // function, thus needing to be saved and restored in the prolog/epilog. - // - const TargetRegisterClass* const *CSRegClasses = + const TargetRegisterClass * const *CSRegClasses = RegInfo->getCalleeSavedRegClasses(&Fn); + std::vector CSI; for (unsigned i = 0; CSRegs[i]; ++i) { unsigned Reg = CSRegs[i]; - if (Fn.getRegInfo().isPhysRegUsed(Reg) || Fn.doesHaveBuiltinSetjmp()) { - // If the reg is modified, save it! + if (Fn.getRegInfo().isPhysRegUsed(Reg)) { + // If the reg is modified, save it! CSI.push_back(CalleeSavedInfo(Reg, CSRegClasses[i])); } else { for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg); @@ -198,39 +227,47 @@ void PEI::calculateCalleeSavedRegisters(MachineFunction &Fn) { return; // Early exit if no callee saved registers are modified! unsigned NumFixedSpillSlots; - const std::pair *FixedSpillSlots = + const TargetFrameInfo::SpillSlot *FixedSpillSlots = TFI->getCalleeSavedSpillSlots(NumFixedSpillSlots); // Now that we know which registers need to be saved and restored, allocate // stack slots for them. - for (unsigned i = 0, e = CSI.size(); i != e; ++i) { - unsigned Reg = CSI[i].getReg(); - const TargetRegisterClass *RC = CSI[i].getRegClass(); + for (std::vector::iterator + I = CSI.begin(), E = CSI.end(); I != E; ++I) { + unsigned Reg = I->getReg(); + const TargetRegisterClass *RC = I->getRegClass(); + + int FrameIdx; + if (RegInfo->hasReservedSpillSlot(Fn, Reg, FrameIdx)) { + I->setFrameIdx(FrameIdx); + continue; + } // Check to see if this physreg must be spilled to a particular stack slot // on this target. - const std::pair *FixedSlot = FixedSpillSlots; + const TargetFrameInfo::SpillSlot *FixedSlot = FixedSpillSlots; while (FixedSlot != FixedSpillSlots+NumFixedSpillSlots && - FixedSlot->first != Reg) + FixedSlot->Reg != Reg) ++FixedSlot; - int FrameIdx; - if (FixedSlot == FixedSpillSlots+NumFixedSpillSlots) { + if (FixedSlot == FixedSpillSlots + NumFixedSpillSlots) { // Nope, just spill it anywhere convenient. unsigned Align = RC->getAlignment(); unsigned StackAlign = TFI->getStackAlignment(); - // We may not be able to sastify the desired alignment specification of - // the TargetRegisterClass if the stack alignment is smaller. - // Use the min. + + // We may not be able to satisfy the desired alignment specification of + // the TargetRegisterClass if the stack alignment is smaller. Use the + // min. Align = std::min(Align, StackAlign); - FrameIdx = FFI->CreateStackObject(RC->getSize(), Align); + FrameIdx = FFI->CreateStackObject(RC->getSize(), Align, true); if ((unsigned)FrameIdx < MinCSFrameIndex) MinCSFrameIndex = FrameIdx; if ((unsigned)FrameIdx > MaxCSFrameIndex) MaxCSFrameIndex = FrameIdx; } else { // Spill it to the stack where we must. - FrameIdx = FFI->CreateFixedObject(RC->getSize(), FixedSlot->second); + FrameIdx = FFI->CreateFixedObject(RC->getSize(), FixedSlot->Offset); } - CSI[i].setFrameIdx(FrameIdx); + + I->setFrameIdx(FrameIdx); } FFI->setCalleeSavedInfo(CSI); @@ -244,6 +281,8 @@ void PEI::insertCSRSpillsAndRestores(MachineFunction &Fn) { MachineFrameInfo *FFI = Fn.getFrameInfo(); const std::vector &CSI = FFI->getCalleeSavedInfo(); + FFI->setCalleeSavedInfoValid(true); + // Early exit if no callee saved registers are modified! if (CSI.empty()) return; @@ -403,8 +442,7 @@ static inline void AdjustStackOffset(MachineFrameInfo *FFI, int FrameIdx, bool StackGrowsDown, int64_t &Offset, unsigned &MaxAlign) { - // If stack grows down, we need to add size of find the lowest address of the - // object. + // If the stack grows down, add the object size to find the lowest address. if (StackGrowsDown) Offset += FFI->getObjectSize(FrameIdx); @@ -437,16 +475,17 @@ void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) { // Loop over all of the stack objects, assigning sequential addresses... MachineFrameInfo *FFI = Fn.getFrameInfo(); - unsigned MaxAlign = FFI->getMaxAlignment(); + unsigned MaxAlign = 1; // Start at the beginning of the local area. // The Offset is the distance from the stack top in the direction // of stack growth -- so it's always nonnegative. - int64_t Offset = TFI.getOffsetOfLocalArea(); + int LocalAreaOffset = TFI.getOffsetOfLocalArea(); if (StackGrowsDown) - Offset = -Offset; - assert(Offset >= 0 + LocalAreaOffset = -LocalAreaOffset; + assert(LocalAreaOffset >= 0 && "Local area offset should be in direction of stack growth"); + int64_t Offset = LocalAreaOffset; // If there are fixed sized objects that are preallocated in the local area, // non-fixed objects can't be allocated right at the start of local area. @@ -503,7 +542,7 @@ void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) { // Make sure the special register scavenging spill slot is closest to the // frame pointer if a frame pointer is required. const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo(); - if (RS && RegInfo->hasFP(Fn)) { + if (RS && RegInfo->hasFP(Fn) && !RegInfo->needsStackRealignment(Fn)) { int SFI = RS->getScavengingFrameIndex(); if (SFI >= 0) AdjustStackOffset(FFI, SFI, StackGrowsDown, Offset, MaxAlign); @@ -532,38 +571,44 @@ void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) { // Make sure the special register scavenging spill slot is closest to the // stack pointer. - if (RS && !RegInfo->hasFP(Fn)) { + if (RS && (!RegInfo->hasFP(Fn) || RegInfo->needsStackRealignment(Fn))) { int SFI = RS->getScavengingFrameIndex(); if (SFI >= 0) AdjustStackOffset(FFI, SFI, StackGrowsDown, Offset, MaxAlign); } - // Round up the size to a multiple of the alignment, but only if there are - // calls or alloca's in the function. This ensures that any calls to - // subroutines have their stack frames suitable aligned. - // Also do this if we need runtime alignment of the stack. In this case - // offsets will be relative to SP not FP; round up the stack size so this - // works. - if (!RegInfo->targetHandlesStackFrameRounding() && - (FFI->hasCalls() || FFI->hasVarSizedObjects() || - (RegInfo->needsStackRealignment(Fn) && - FFI->getObjectIndexEnd() != 0))) { + if (!RegInfo->targetHandlesStackFrameRounding()) { // If we have reserved argument space for call sites in the function // immediately on entry to the current function, count it as part of the // overall stack size. - if (RegInfo->hasReservedCallFrame(Fn)) + if (FFI->hasCalls() && RegInfo->hasReservedCallFrame(Fn)) Offset += FFI->getMaxCallFrameSize(); - unsigned AlignMask = std::max(TFI.getStackAlignment(),MaxAlign) - 1; + // Round up the size to a multiple of the alignment. If the function has + // any calls or alloca's, align to the target's StackAlignment value to + // ensure that the callee's frame or the alloca data is suitably aligned; + // otherwise, for leaf functions, align to the TransientStackAlignment + // value. + unsigned StackAlign; + if (FFI->hasCalls() || FFI->hasVarSizedObjects() || + (RegInfo->needsStackRealignment(Fn) && FFI->getObjectIndexEnd() != 0)) + StackAlign = TFI.getStackAlignment(); + else + StackAlign = TFI.getTransientStackAlignment(); + // If the frame pointer is eliminated, all frame offsets will be relative + // to SP not FP; align to MaxAlign so this works. + StackAlign = std::max(StackAlign, MaxAlign); + unsigned AlignMask = StackAlign - 1; Offset = (Offset + AlignMask) & ~uint64_t(AlignMask); } // Update frame info to pretend that this is part of the stack... - FFI->setStackSize(Offset+TFI.getOffsetOfLocalArea()); + FFI->setStackSize(Offset - LocalAreaOffset); // Remember the required stack alignment in case targets need it to perform // dynamic stack alignment. - FFI->setMaxAlignment(MaxAlign); + if (MaxAlign > FFI->getMaxAlignment()) + FFI->setMaxAlignment(MaxAlign); } @@ -604,14 +649,9 @@ void PEI::replaceFrameIndices(MachineFunction &Fn) { for (MachineFunction::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB) { int SPAdj = 0; // SP offset due to call frame setup / destroy. - if (RS) RS->enterBasicBlock(BB); + if (RS && !FrameIndexVirtualScavenging) RS->enterBasicBlock(BB); for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) { - if (I->getOpcode() == TargetInstrInfo::DECLARE) { - // Ignore it. - ++I; - continue; - } if (I->getOpcode() == FrameSetupOpcode || I->getOpcode() == FrameDestroyOpcode) { @@ -654,8 +694,16 @@ void PEI::replaceFrameIndices(MachineFunction &Fn) { // If this instruction has a FrameIndex operand, we need to // use that target machine register info object to eliminate // it. - - TRI.eliminateFrameIndex(MI, SPAdj, RS); + int Value; + unsigned VReg = + TRI.eliminateFrameIndex(MI, SPAdj, &Value, + FrameIndexVirtualScavenging ? NULL : RS); + if (VReg) { + assert (FrameIndexVirtualScavenging && + "Not scavenging, but virtual returned from " + "eliminateFrameIndex()!"); + FrameConstantRegMap[VReg] = FrameConstantEntry(Value, SPAdj); + } // Reset the iterator if we were at the beginning of the BB. if (AtBeginning) { @@ -670,10 +718,202 @@ void PEI::replaceFrameIndices(MachineFunction &Fn) { if (DoIncr && I != BB->end()) ++I; // Update register states. - if (RS && MI) RS->forward(MI); + if (RS && !FrameIndexVirtualScavenging && MI) RS->forward(MI); } assert(SPAdj == 0 && "Unbalanced call frame setup / destroy pairs?"); } } +/// findLastUseReg - find the killing use of the specified register within +/// the instruciton range. Return the operand number of the kill in Operand. +static MachineBasicBlock::iterator +findLastUseReg(MachineBasicBlock::iterator I, MachineBasicBlock::iterator ME, + unsigned Reg) { + // Scan forward to find the last use of this virtual register + for (++I; I != ME; ++I) { + MachineInstr *MI = I; + bool isDefInsn = false; + bool isKillInsn = false; + for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) + if (MI->getOperand(i).isReg()) { + unsigned OpReg = MI->getOperand(i).getReg(); + if (OpReg == 0 || !TargetRegisterInfo::isVirtualRegister(OpReg)) + continue; + assert (OpReg == Reg + && "overlapping use of scavenged index register!"); + // If this is the killing use, we have a candidate. + if (MI->getOperand(i).isKill()) + isKillInsn = true; + else if (MI->getOperand(i).isDef()) + isDefInsn = true; + } + if (isKillInsn && !isDefInsn) + return I; + } + // If we hit the end of the basic block, there was no kill of + // the virtual register, which is wrong. + assert (0 && "scavenged index register never killed!"); + return ME; +} + +/// scavengeFrameVirtualRegs - Replace all frame index virtual registers +/// with physical registers. Use the register scavenger to find an +/// appropriate register to use. +void PEI::scavengeFrameVirtualRegs(MachineFunction &Fn) { + // Run through the instructions and find any virtual registers. + for (MachineFunction::iterator BB = Fn.begin(), + E = Fn.end(); BB != E; ++BB) { + RS->enterBasicBlock(BB); + + // FIXME: The logic flow in this function is still too convoluted. + // It needs a cleanup refactoring. Do that in preparation for tracking + // more than one scratch register value and using ranges to find + // available scratch registers. + unsigned CurrentVirtReg = 0; + unsigned CurrentScratchReg = 0; + bool havePrevValue = false; + int PrevValue = 0; + MachineInstr *PrevLastUseMI = NULL; + unsigned PrevLastUseOp = 0; + bool trackingCurrentValue = false; + int SPAdj = 0; + int Value = 0; + + // The instruction stream may change in the loop, so check BB->end() + // directly. + for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) { + MachineInstr *MI = I; + bool isDefInsn = false; + bool isKillInsn = false; + bool clobbersScratchReg = false; + bool DoIncr = true; + for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { + if (MI->getOperand(i).isReg()) { + MachineOperand &MO = MI->getOperand(i); + unsigned Reg = MO.getReg(); + if (Reg == 0) + continue; + if (!TargetRegisterInfo::isVirtualRegister(Reg)) { + // If we have a previous scratch reg, check and see if anything + // here kills whatever value is in there. + if (Reg == CurrentScratchReg) { + if (MO.isUse()) { + // Two-address operands implicitly kill + if (MO.isKill() || MI->isRegTiedToDefOperand(i)) + clobbersScratchReg = true; + } else { + assert (MO.isDef()); + clobbersScratchReg = true; + } + } + continue; + } + // If this is a def, remember that this insn defines the value. + // This lets us properly consider insns which re-use the scratch + // register, such as r2 = sub r2, #imm, in the middle of the + // scratch range. + if (MO.isDef()) + isDefInsn = true; + + // Have we already allocated a scratch register for this virtual? + if (Reg != CurrentVirtReg) { + // When we first encounter a new virtual register, it + // must be a definition. + assert(MI->getOperand(i).isDef() && + "frame index virtual missing def!"); + // We can't have nested virtual register live ranges because + // there's only a guarantee of one scavenged register at a time. + assert (CurrentVirtReg == 0 && + "overlapping frame index virtual registers!"); + + // If the target gave us information about what's in the register, + // we can use that to re-use scratch regs. + DenseMap::iterator Entry = + FrameConstantRegMap.find(Reg); + trackingCurrentValue = Entry != FrameConstantRegMap.end(); + if (trackingCurrentValue) { + SPAdj = (*Entry).second.second; + Value = (*Entry).second.first; + } else + SPAdj = Value = 0; + + // If the scratch register from the last allocation is still + // available, see if the value matches. If it does, just re-use it. + if (trackingCurrentValue && havePrevValue && PrevValue == Value) { + // FIXME: This assumes that the instructions in the live range + // for the virtual register are exclusively for the purpose + // of populating the value in the register. That's reasonable + // for these frame index registers, but it's still a very, very + // strong assumption. rdar://7322732. Better would be to + // explicitly check each instruction in the range for references + // to the virtual register. Only delete those insns that + // touch the virtual register. + + // Find the last use of the new virtual register. Remove all + // instruction between here and there, and update the current + // instruction to reference the last use insn instead. + MachineBasicBlock::iterator LastUseMI = + findLastUseReg(I, BB->end(), Reg); + + // Remove all instructions up 'til the last use, since they're + // just calculating the value we already have. + BB->erase(I, LastUseMI); + MI = I = LastUseMI; + + // Extend the live range of the scratch register + PrevLastUseMI->getOperand(PrevLastUseOp).setIsKill(false); + RS->setUsed(CurrentScratchReg); + CurrentVirtReg = Reg; + + // We deleted the instruction we were scanning the operands of. + // Jump back to the instruction iterator loop. Don't increment + // past this instruction since we updated the iterator already. + DoIncr = false; + break; + } + + // Scavenge a new scratch register + CurrentVirtReg = Reg; + const TargetRegisterClass *RC = Fn.getRegInfo().getRegClass(Reg); + CurrentScratchReg = RS->FindUnusedReg(RC); + if (CurrentScratchReg == 0) + // No register is "free". Scavenge a register. + CurrentScratchReg = RS->scavengeRegister(RC, I, SPAdj); + + PrevValue = Value; + } + // replace this reference to the virtual register with the + // scratch register. + assert (CurrentScratchReg && "Missing scratch register!"); + MI->getOperand(i).setReg(CurrentScratchReg); + + if (MI->getOperand(i).isKill()) { + isKillInsn = true; + PrevLastUseOp = i; + PrevLastUseMI = MI; + } + } + } + // If this is the last use of the scratch, stop tracking it. The + // last use will be a kill operand in an instruction that does + // not also define the scratch register. + if (isKillInsn && !isDefInsn) { + CurrentVirtReg = 0; + havePrevValue = trackingCurrentValue; + } + // Similarly, notice if instruction clobbered the value in the + // register we're tracking for possible later reuse. This is noted + // above, but enforced here since the value is still live while we + // process the rest of the operands of the instruction. + if (clobbersScratchReg) { + havePrevValue = false; + CurrentScratchReg = 0; + } + if (DoIncr) { + RS->forward(I); + ++I; + } + } + } +}