X-Git-Url: http://plrg.eecs.uci.edu/git/?p=oota-llvm.git;a=blobdiff_plain;f=lib%2FTarget%2FARM%2FThumb1FrameLowering.cpp;h=6deab4f0887c7949a7a6c2de54e29579a0e4abe5;hp=326d4af19826e51139dac61295612c750484d377;hb=b23c2d9b2c9f4cfcb3781486c3a13d553a45b474;hpb=63b46faeb8acae9b7e5f865b7417dc00b9b9dad3 diff --git a/lib/Target/ARM/Thumb1FrameLowering.cpp b/lib/Target/ARM/Thumb1FrameLowering.cpp index 326d4af1982..6deab4f0887 100644 --- a/lib/Target/ARM/Thumb1FrameLowering.cpp +++ b/lib/Target/ARM/Thumb1FrameLowering.cpp @@ -1,4 +1,4 @@ -//======- Thumb1FrameLowering.cpp - Thumb1 Frame Information ---*- C++ -*-====// +//===-- Thumb1FrameLowering.cpp - Thumb1 Frame Information ----------------===// // // The LLVM Compiler Infrastructure // @@ -12,16 +12,19 @@ //===----------------------------------------------------------------------===// #include "Thumb1FrameLowering.h" -#include "ARMBaseInstrInfo.h" #include "ARMMachineFunctionInfo.h" #include "llvm/CodeGen/MachineFrameInfo.h" #include "llvm/CodeGen/MachineFunction.h" #include "llvm/CodeGen/MachineInstrBuilder.h" +#include "llvm/CodeGen/MachineModuleInfo.h" #include "llvm/CodeGen/MachineRegisterInfo.h" using namespace llvm; -bool Thumb1FrameLowering::hasReservedCallFrame(const MachineFunction &MF) const { +Thumb1FrameLowering::Thumb1FrameLowering(const ARMSubtarget &sti) + : ARMFrameLowering(sti) {} + +bool Thumb1FrameLowering::hasReservedCallFrame(const MachineFunction &MF) const{ const MachineFrameInfo *FFI = MF.getFrameInfo(); unsigned CFSize = FFI->getMaxCallFrameSize(); // It's not always a good idea to include the call frame as part of the @@ -44,22 +47,66 @@ emitSPUpdate(MachineBasicBlock &MBB, MRI, MIFlags); } + +void Thumb1FrameLowering:: +eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB, + MachineBasicBlock::iterator I) const { + const Thumb1InstrInfo &TII = + *static_cast(MF.getSubtarget().getInstrInfo()); + const Thumb1RegisterInfo *RegInfo = static_cast( + MF.getSubtarget().getRegisterInfo()); + if (!hasReservedCallFrame(MF)) { + // If we have alloca, convert as follows: + // ADJCALLSTACKDOWN -> sub, sp, sp, amount + // ADJCALLSTACKUP -> add, sp, sp, amount + MachineInstr *Old = I; + DebugLoc dl = Old->getDebugLoc(); + unsigned Amount = Old->getOperand(0).getImm(); + if (Amount != 0) { + // We need to keep the stack aligned properly. To do this, we round the + // amount of space needed for the outgoing arguments up to the next + // alignment boundary. + unsigned Align = getStackAlignment(); + Amount = (Amount+Align-1)/Align*Align; + + // Replace the pseudo instruction with a new instruction... + unsigned Opc = Old->getOpcode(); + if (Opc == ARM::ADJCALLSTACKDOWN || Opc == ARM::tADJCALLSTACKDOWN) { + emitSPUpdate(MBB, I, TII, dl, *RegInfo, -Amount); + } else { + assert(Opc == ARM::ADJCALLSTACKUP || Opc == ARM::tADJCALLSTACKUP); + emitSPUpdate(MBB, I, TII, dl, *RegInfo, Amount); + } + } + } + MBB.erase(I); +} + void Thumb1FrameLowering::emitPrologue(MachineFunction &MF) const { MachineBasicBlock &MBB = MF.front(); MachineBasicBlock::iterator MBBI = MBB.begin(); MachineFrameInfo *MFI = MF.getFrameInfo(); ARMFunctionInfo *AFI = MF.getInfo(); - const Thumb1RegisterInfo *RegInfo = - static_cast(MF.getTarget().getRegisterInfo()); + MachineModuleInfo &MMI = MF.getMMI(); + const MCRegisterInfo *MRI = MMI.getContext().getRegisterInfo(); + const Thumb1RegisterInfo *RegInfo = static_cast( + MF.getSubtarget().getRegisterInfo()); const Thumb1InstrInfo &TII = - *static_cast(MF.getTarget().getInstrInfo()); + *static_cast(MF.getSubtarget().getInstrInfo()); - unsigned VARegSaveSize = AFI->getVarArgsRegSaveSize(); + unsigned Align = MF.getTarget() + .getSubtargetImpl() + ->getFrameLowering() + ->getStackAlignment(); + unsigned ArgRegsSaveSize = AFI->getArgRegsSaveSize(Align); unsigned NumBytes = MFI->getStackSize(); + assert(NumBytes >= ArgRegsSaveSize && + "ArgRegsSaveSize is included in NumBytes"); const std::vector &CSI = MFI->getCalleeSavedInfo(); DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc(); unsigned FramePtr = RegInfo->getFrameRegister(MF); unsigned BasePtr = RegInfo->getBaseRegister(); + int CFAOffset = 0; // Thumb add/sub sp, imm8 instructions implicitly multiply the offset by 4. NumBytes = (NumBytes + 3) & ~3; @@ -70,14 +117,26 @@ void Thumb1FrameLowering::emitPrologue(MachineFunction &MF) const { unsigned GPRCS1Size = 0, GPRCS2Size = 0, DPRCSSize = 0; int FramePtrSpillFI = 0; - if (VARegSaveSize) - emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, -VARegSaveSize, + if (ArgRegsSaveSize) { + emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, -ArgRegsSaveSize, MachineInstr::FrameSetup); + CFAOffset -= ArgRegsSaveSize; + unsigned CFIIndex = MMI.addFrameInst( + MCCFIInstruction::createDefCfaOffset(nullptr, CFAOffset)); + BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION)) + .addCFIIndex(CFIIndex); + } if (!AFI->hasStackFrame()) { - if (NumBytes != 0) - emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, -NumBytes, + if (NumBytes - ArgRegsSaveSize != 0) { + emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, -(NumBytes - ArgRegsSaveSize), MachineInstr::FrameSetup); + CFAOffset -= NumBytes - ArgRegsSaveSize; + unsigned CFIIndex = MMI.addFrameInst( + MCCFIInstruction::createDefCfaOffset(nullptr, CFAOffset)); + BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION)) + .addCFIIndex(CFIIndex); + } return; } @@ -85,6 +144,15 @@ void Thumb1FrameLowering::emitPrologue(MachineFunction &MF) const { unsigned Reg = CSI[i].getReg(); int FI = CSI[i].getFrameIdx(); switch (Reg) { + case ARM::R8: + case ARM::R9: + case ARM::R10: + case ARM::R11: + if (STI.isTargetMachO()) { + GPRCS2Size += 4; + break; + } + // fallthrough case ARM::R4: case ARM::R5: case ARM::R6: @@ -92,25 +160,9 @@ void Thumb1FrameLowering::emitPrologue(MachineFunction &MF) const { case ARM::LR: if (Reg == FramePtr) FramePtrSpillFI = FI; - AFI->addGPRCalleeSavedArea1Frame(FI); GPRCS1Size += 4; break; - case ARM::R8: - case ARM::R9: - case ARM::R10: - case ARM::R11: - if (Reg == FramePtr) - FramePtrSpillFI = FI; - if (STI.isTargetDarwin()) { - AFI->addGPRCalleeSavedArea2Frame(FI); - GPRCS2Size += 4; - } else { - AFI->addGPRCalleeSavedArea1Frame(FI); - GPRCS1Size += 4; - } - break; default: - AFI->addDPRCalleeSavedAreaFrame(FI); DPRCSSize += 8; } } @@ -122,32 +174,104 @@ void Thumb1FrameLowering::emitPrologue(MachineFunction &MF) const { } // Determine starting offsets of spill areas. - unsigned DPRCSOffset = NumBytes - (GPRCS1Size + GPRCS2Size + DPRCSSize); + unsigned DPRCSOffset = NumBytes - ArgRegsSaveSize - (GPRCS1Size + GPRCS2Size + DPRCSSize); unsigned GPRCS2Offset = DPRCSOffset + DPRCSSize; unsigned GPRCS1Offset = GPRCS2Offset + GPRCS2Size; - AFI->setFramePtrSpillOffset(MFI->getObjectOffset(FramePtrSpillFI) + NumBytes); + bool HasFP = hasFP(MF); + if (HasFP) + AFI->setFramePtrSpillOffset(MFI->getObjectOffset(FramePtrSpillFI) + + NumBytes); AFI->setGPRCalleeSavedArea1Offset(GPRCS1Offset); AFI->setGPRCalleeSavedArea2Offset(GPRCS2Offset); AFI->setDPRCalleeSavedAreaOffset(DPRCSOffset); NumBytes = DPRCSOffset; + int FramePtrOffsetInBlock = 0; + unsigned adjustedGPRCS1Size = GPRCS1Size; + if (tryFoldSPUpdateIntoPushPop(STI, MF, std::prev(MBBI), NumBytes)) { + FramePtrOffsetInBlock = NumBytes; + adjustedGPRCS1Size += NumBytes; + NumBytes = 0; + } + + if (adjustedGPRCS1Size) { + CFAOffset -= adjustedGPRCS1Size; + unsigned CFIIndex = MMI.addFrameInst( + MCCFIInstruction::createDefCfaOffset(nullptr, CFAOffset)); + BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION)) + .addCFIIndex(CFIIndex); + } + for (std::vector::const_iterator I = CSI.begin(), + E = CSI.end(); I != E; ++I) { + unsigned Reg = I->getReg(); + int FI = I->getFrameIdx(); + switch (Reg) { + case ARM::R8: + case ARM::R9: + case ARM::R10: + case ARM::R11: + case ARM::R12: + if (STI.isTargetMachO()) + break; + // fallthough + case ARM::R0: + case ARM::R1: + case ARM::R2: + case ARM::R3: + case ARM::R4: + case ARM::R5: + case ARM::R6: + case ARM::R7: + case ARM::LR: + unsigned CFIIndex = MMI.addFrameInst(MCCFIInstruction::createOffset( + nullptr, MRI->getDwarfRegNum(Reg, true), MFI->getObjectOffset(FI))); + BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION)) + .addCFIIndex(CFIIndex); + break; + } + } + + // Adjust FP so it point to the stack slot that contains the previous FP. - if (hasFP(MF)) { - BuildMI(MBB, MBBI, dl, TII.get(ARM::tADDrSPi), FramePtr) - .addFrameIndex(FramePtrSpillFI).addImm(0) - .setMIFlags(MachineInstr::FrameSetup); + if (HasFP) { + FramePtrOffsetInBlock += MFI->getObjectOffset(FramePtrSpillFI) + + GPRCS1Size + ArgRegsSaveSize; + AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tADDrSPi), FramePtr) + .addReg(ARM::SP).addImm(FramePtrOffsetInBlock / 4) + .setMIFlags(MachineInstr::FrameSetup)); + if(FramePtrOffsetInBlock) { + CFAOffset += FramePtrOffsetInBlock; + unsigned CFIIndex = MMI.addFrameInst(MCCFIInstruction::createDefCfa( + nullptr, MRI->getDwarfRegNum(FramePtr, true), CFAOffset)); + BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION)) + .addCFIIndex(CFIIndex); + } else { + unsigned CFIIndex = + MMI.addFrameInst(MCCFIInstruction::createDefCfaRegister( + nullptr, MRI->getDwarfRegNum(FramePtr, true))); + BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION)) + .addCFIIndex(CFIIndex); + } if (NumBytes > 508) // If offset is > 508 then sp cannot be adjusted in a single instruction, // try restoring from fp instead. AFI->setShouldRestoreSPFromFP(true); } - if (NumBytes) + if (NumBytes) { // Insert it after all the callee-save spills. emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, -NumBytes, MachineInstr::FrameSetup); + if (!HasFP) { + CFAOffset -= NumBytes; + unsigned CFIIndex = MMI.addFrameInst( + MCCFIInstruction::createDefCfaOffset(nullptr, CFAOffset)); + BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION)) + .addCFIIndex(CFIIndex); + } + } - if (STI.isTargetELF() && hasFP(MF)) + if (STI.isTargetELF() && HasFP) MFI->setOffsetAdjustment(MFI->getOffsetAdjustment() - AFI->getFramePtrSpillOffset()); @@ -155,12 +279,17 @@ void Thumb1FrameLowering::emitPrologue(MachineFunction &MF) const { AFI->setGPRCalleeSavedArea2Size(GPRCS2Size); AFI->setDPRCalleeSavedAreaSize(DPRCSSize); + // Thumb1 does not currently support dynamic stack realignment. Report a + // fatal error rather then silently generate bad code. + if (RegInfo->needsStackRealignment(MF)) + report_fatal_error("Dynamic stack realignment not supported for thumb1."); + // If we need a base pointer, set it up here. It's whatever the value // of the stack pointer is at this point. Any variable size objects // will be allocated after this, so we can still use the base pointer // to reference locals. if (RegInfo->hasBasePointer(MF)) - AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVgpr2gpr), BasePtr) + AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), BasePtr) .addReg(ARM::SP)); // If the frame has variable sized objects then the epilogue must restore @@ -170,14 +299,7 @@ void Thumb1FrameLowering::emitPrologue(MachineFunction &MF) const { AFI->setShouldRestoreSPFromFP(true); } -static bool isCalleeSavedRegister(unsigned Reg, const unsigned *CSRegs) { - for (unsigned i = 0; CSRegs[i]; ++i) - if (Reg == CSRegs[i]) - return true; - return false; -} - -static bool isCSRestore(MachineInstr *MI, const unsigned *CSRegs) { +static bool isCSRestore(MachineInstr *MI, const MCPhysReg *CSRegs) { if (MI->getOpcode() == ARM::tLDRspi && MI->getOperand(1).isFI() && isCalleeSavedRegister(MI->getOperand(0).getReg(), CSRegs)) @@ -202,19 +324,25 @@ void Thumb1FrameLowering::emitEpilogue(MachineFunction &MF, DebugLoc dl = MBBI->getDebugLoc(); MachineFrameInfo *MFI = MF.getFrameInfo(); ARMFunctionInfo *AFI = MF.getInfo(); - const Thumb1RegisterInfo *RegInfo = - static_cast(MF.getTarget().getRegisterInfo()); + const Thumb1RegisterInfo *RegInfo = static_cast( + MF.getSubtarget().getRegisterInfo()); const Thumb1InstrInfo &TII = - *static_cast(MF.getTarget().getInstrInfo()); + *static_cast(MF.getSubtarget().getInstrInfo()); - unsigned VARegSaveSize = AFI->getVarArgsRegSaveSize(); + unsigned Align = MF.getTarget() + .getSubtargetImpl() + ->getFrameLowering() + ->getStackAlignment(); + unsigned ArgRegsSaveSize = AFI->getArgRegsSaveSize(Align); int NumBytes = (int)MFI->getStackSize(); - const unsigned *CSRegs = RegInfo->getCalleeSavedRegs(); + assert((unsigned)NumBytes >= ArgRegsSaveSize && + "ArgRegsSaveSize is included in NumBytes"); + const MCPhysReg *CSRegs = RegInfo->getCalleeSavedRegs(); unsigned FramePtr = RegInfo->getFrameRegister(MF); if (!AFI->hasStackFrame()) { - if (NumBytes != 0) - emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, NumBytes); + if (NumBytes - ArgRegsSaveSize != 0) + emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, NumBytes - ArgRegsSaveSize); } else { // Unwind MBBI to point to first LDR / VLDRD. if (MBBI != MBB.begin()) { @@ -228,7 +356,8 @@ void Thumb1FrameLowering::emitEpilogue(MachineFunction &MF, // Move SP to start of FP callee save spill area. NumBytes -= (AFI->getGPRCalleeSavedArea1Size() + AFI->getGPRCalleeSavedArea2Size() + - AFI->getDPRCalleeSavedAreaSize()); + AFI->getDPRCalleeSavedAreaSize() + + ArgRegsSaveSize); if (AFI->shouldRestoreSPFromFP()) { NumBytes = AFI->getFramePtrSpillOffset() - NumBytes; @@ -240,43 +369,84 @@ void Thumb1FrameLowering::emitEpilogue(MachineFunction &MF, "No scratch register to restore SP from FP!"); emitThumbRegPlusImmediate(MBB, MBBI, dl, ARM::R4, FramePtr, -NumBytes, TII, *RegInfo); - AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVtgpr2gpr), + AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::SP) .addReg(ARM::R4)); } else - AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVtgpr2gpr), + AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), ARM::SP) .addReg(FramePtr)); } else { if (MBBI->getOpcode() == ARM::tBX_RET && &MBB.front() != MBBI && - prior(MBBI)->getOpcode() == ARM::tPOP) { - MachineBasicBlock::iterator PMBBI = prior(MBBI); - emitSPUpdate(MBB, PMBBI, TII, dl, *RegInfo, NumBytes); - } else + std::prev(MBBI)->getOpcode() == ARM::tPOP) { + MachineBasicBlock::iterator PMBBI = std::prev(MBBI); + if (!tryFoldSPUpdateIntoPushPop(STI, MF, PMBBI, NumBytes)) + emitSPUpdate(MBB, PMBBI, TII, dl, *RegInfo, NumBytes); + } else if (!tryFoldSPUpdateIntoPushPop(STI, MF, MBBI, NumBytes)) emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, NumBytes); } } - if (VARegSaveSize) { - // Unlike T2 and ARM mode, the T1 pop instruction cannot restore - // to LR, and we can't pop the value directly to the PC since - // we need to update the SP after popping the value. Therefore, we - // pop the old LR into R3 as a temporary. - - // Move back past the callee-saved register restoration - while (MBBI != MBB.end() && isCSRestore(MBBI, CSRegs)) - ++MBBI; - // Epilogue for vararg functions: pop LR to R3 and branch off it. - AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tPOP))) - .addReg(ARM::R3, RegState::Define); - - emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, VARegSaveSize); - - BuildMI(MBB, MBBI, dl, TII.get(ARM::tBX_RET_vararg)) - .addReg(ARM::R3, RegState::Kill); - // erase the old tBX_RET instruction - MBB.erase(MBBI); + bool IsV4PopReturn = false; + for (const CalleeSavedInfo &CSI : MFI->getCalleeSavedInfo()) + if (CSI.getReg() == ARM::LR) + IsV4PopReturn = true; + IsV4PopReturn &= STI.hasV4TOps() && !STI.hasV5TOps(); + + // Unlike T2 and ARM mode, the T1 pop instruction cannot restore + // to LR, and we can't pop the value directly to the PC since + // we need to update the SP after popping the value. So instead + // we have to emit: + // POP {r3} + // ADD sp, #offset + // BX r3 + // If this would clobber a return value, then generate this sequence instead: + // MOV ip, r3 + // POP {r3} + // ADD sp, #offset + // MOV lr, r3 + // MOV r3, ip + // BX lr + if (ArgRegsSaveSize || IsV4PopReturn) { + // Get the last instruction, tBX_RET + MBBI = MBB.getLastNonDebugInstr(); + assert (MBBI->getOpcode() == ARM::tBX_RET); + DebugLoc dl = MBBI->getDebugLoc(); + + if (AFI->getReturnRegsCount() <= 3) { + // Epilogue: pop saved LR to R3 and branch off it. + AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tPOP))) + .addReg(ARM::R3, RegState::Define); + + emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, ArgRegsSaveSize); + + MachineInstrBuilder MIB = + BuildMI(MBB, MBBI, dl, TII.get(ARM::tBX)) + .addReg(ARM::R3, RegState::Kill); + AddDefaultPred(MIB); + MIB.copyImplicitOps(&*MBBI); + // erase the old tBX_RET instruction + MBB.erase(MBBI); + } else { + AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr)) + .addReg(ARM::R12, RegState::Define) + .addReg(ARM::R3, RegState::Kill)); + + AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tPOP))) + .addReg(ARM::R3, RegState::Define); + + emitSPUpdate(MBB, MBBI, TII, dl, *RegInfo, ArgRegsSaveSize); + + AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr)) + .addReg(ARM::LR, RegState::Define) + .addReg(ARM::R3, RegState::Kill)); + + AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr)) + .addReg(ARM::R3, RegState::Define) + .addReg(ARM::R12, RegState::Kill)); + // Keep the tBX_RET instruction + } } } @@ -290,7 +460,7 @@ spillCalleeSavedRegisters(MachineBasicBlock &MBB, DebugLoc DL; MachineFunction &MF = *MBB.getParent(); - const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo(); + const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo(); if (MI != MBB.end()) DL = MI->getDebugLoc(); @@ -329,9 +499,9 @@ restoreCalleeSavedRegisters(MachineBasicBlock &MBB, MachineFunction &MF = *MBB.getParent(); ARMFunctionInfo *AFI = MF.getInfo(); - const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo(); + const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo(); - bool isVarArg = AFI->getVarArgsRegSaveSize() > 0; + bool isVarArg = AFI->getArgRegsSaveSize() > 0; DebugLoc DL = MI->getDebugLoc(); MachineInstrBuilder MIB = BuildMI(MF, DL, TII.get(ARM::tPOP)); AddDefaultPred(MIB); @@ -343,8 +513,12 @@ restoreCalleeSavedRegisters(MachineBasicBlock &MBB, // Special epilogue for vararg functions. See emitEpilogue if (isVarArg) continue; + // ARMv4T requires BX, see emitEpilogue + if (STI.hasV4TOps() && !STI.hasV5TOps()) + continue; Reg = ARM::PC; (*MIB).setDesc(TII.get(ARM::tPOP_RET)); + MIB.copyImplicitOps(&*MI); MI = MBB.erase(MI); } MIB.addReg(Reg, getDefRegState(true));