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llvm-project/llvm/lib/Target/Mips/MipsInstrInfo.cpp

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//===- MipsInstrInfo.cpp - Mips Instruction Information ---------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the Mips implementation of the TargetInstrInfo class.
//
//===----------------------------------------------------------------------===//
#include "MipsInstrInfo.h"
#include "MipsTargetMachine.h"
#include "MipsMachineFunction.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Support/ErrorHandling.h"
#include "MipsGenInstrInfo.inc"
using namespace llvm;
MipsInstrInfo::MipsInstrInfo(MipsTargetMachine &tm)
: TargetInstrInfoImpl(MipsInsts, array_lengthof(MipsInsts)),
TM(tm), RI(*TM.getSubtargetImpl(), *this) {}
static bool isZeroImm(const MachineOperand &op) {
return op.isImm() && op.getImm() == 0;
}
/// Return true if the instruction is a register to register move and
/// leave the source and dest operands in the passed parameters.
bool MipsInstrInfo::
isMoveInstr(const MachineInstr &MI, unsigned &SrcReg, unsigned &DstReg,
unsigned &SrcSubIdx, unsigned &DstSubIdx) const
{
SrcSubIdx = DstSubIdx = 0; // No sub-registers.
// addu $dst, $src, $zero || addu $dst, $zero, $src
// or $dst, $src, $zero || or $dst, $zero, $src
if ((MI.getOpcode() == Mips::ADDu) || (MI.getOpcode() == Mips::OR)) {
if (MI.getOperand(1).getReg() == Mips::ZERO) {
DstReg = MI.getOperand(0).getReg();
SrcReg = MI.getOperand(2).getReg();
return true;
} else if (MI.getOperand(2).getReg() == Mips::ZERO) {
DstReg = MI.getOperand(0).getReg();
SrcReg = MI.getOperand(1).getReg();
return true;
}
}
// mov $fpDst, $fpSrc
// mfc $gpDst, $fpSrc
// mtc $fpDst, $gpSrc
if (MI.getOpcode() == Mips::FMOV_S32 ||
MI.getOpcode() == Mips::FMOV_D32 ||
MI.getOpcode() == Mips::MFC1 ||
MI.getOpcode() == Mips::MTC1 ||
MI.getOpcode() == Mips::MOVCCRToCCR) {
DstReg = MI.getOperand(0).getReg();
SrcReg = MI.getOperand(1).getReg();
return true;
}
// addiu $dst, $src, 0
if (MI.getOpcode() == Mips::ADDiu) {
if ((MI.getOperand(1).isReg()) && (isZeroImm(MI.getOperand(2)))) {
DstReg = MI.getOperand(0).getReg();
SrcReg = MI.getOperand(1).getReg();
return true;
}
}
return false;
}
/// isLoadFromStackSlot - If the specified machine instruction is a direct
/// load from a stack slot, return the virtual or physical register number of
/// the destination along with the FrameIndex of the loaded stack slot. If
/// not, return 0. This predicate must return 0 if the instruction has
/// any side effects other than loading from the stack slot.
unsigned MipsInstrInfo::
isLoadFromStackSlot(const MachineInstr *MI, int &FrameIndex) const
{
if ((MI->getOpcode() == Mips::LW) || (MI->getOpcode() == Mips::LWC1) ||
(MI->getOpcode() == Mips::LDC1)) {
if ((MI->getOperand(2).isFI()) && // is a stack slot
(MI->getOperand(1).isImm()) && // the imm is zero
(isZeroImm(MI->getOperand(1)))) {
FrameIndex = MI->getOperand(2).getIndex();
return MI->getOperand(0).getReg();
}
}
return 0;
}
/// isStoreToStackSlot - If the specified machine instruction is a direct
/// store to a stack slot, return the virtual or physical register number of
/// the source reg along with the FrameIndex of the loaded stack slot. If
/// not, return 0. This predicate must return 0 if the instruction has
/// any side effects other than storing to the stack slot.
unsigned MipsInstrInfo::
isStoreToStackSlot(const MachineInstr *MI, int &FrameIndex) const
{
if ((MI->getOpcode() == Mips::SW) || (MI->getOpcode() == Mips::SWC1) ||
(MI->getOpcode() == Mips::SDC1)) {
if ((MI->getOperand(2).isFI()) && // is a stack slot
(MI->getOperand(1).isImm()) && // the imm is zero
(isZeroImm(MI->getOperand(1)))) {
FrameIndex = MI->getOperand(2).getIndex();
return MI->getOperand(0).getReg();
}
}
return 0;
}
/// insertNoop - If data hazard condition is found insert the target nop
/// instruction.
void MipsInstrInfo::
insertNoop(MachineBasicBlock &MBB, MachineBasicBlock::iterator MI) const
{
DebugLoc DL = DebugLoc::getUnknownLoc();
if (MI != MBB.end()) DL = MI->getDebugLoc();
BuildMI(MBB, MI, DL, get(Mips::NOP));
}
bool MipsInstrInfo::
copyRegToReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
unsigned DestReg, unsigned SrcReg,
const TargetRegisterClass *DestRC,
const TargetRegisterClass *SrcRC) const {
DebugLoc DL = DebugLoc::getUnknownLoc();
if (I != MBB.end()) DL = I->getDebugLoc();
if (DestRC != SrcRC) {
// Copy to/from FCR31 condition register
if ((DestRC == Mips::CPURegsRegisterClass) &&
(SrcRC == Mips::CCRRegisterClass))
BuildMI(MBB, I, DL, get(Mips::CFC1), DestReg).addReg(SrcReg);
else if ((DestRC == Mips::CCRRegisterClass) &&
(SrcRC == Mips::CPURegsRegisterClass))
BuildMI(MBB, I, DL, get(Mips::CTC1), DestReg).addReg(SrcReg);
// Moves between coprocessors and cpu
else if ((DestRC == Mips::CPURegsRegisterClass) &&
(SrcRC == Mips::FGR32RegisterClass))
BuildMI(MBB, I, DL, get(Mips::MFC1), DestReg).addReg(SrcReg);
else if ((DestRC == Mips::FGR32RegisterClass) &&
(SrcRC == Mips::CPURegsRegisterClass))
BuildMI(MBB, I, DL, get(Mips::MTC1), DestReg).addReg(SrcReg);
// Move from/to Hi/Lo registers
else if ((DestRC == Mips::HILORegisterClass) &&
(SrcRC == Mips::CPURegsRegisterClass)) {
unsigned Opc = (DestReg == Mips::HI) ? Mips::MTHI : Mips::MTLO;
BuildMI(MBB, I, DL, get(Opc), DestReg);
} else if ((SrcRC == Mips::HILORegisterClass) &&
(DestRC == Mips::CPURegsRegisterClass)) {
unsigned Opc = (SrcReg == Mips::HI) ? Mips::MFHI : Mips::MFLO;
BuildMI(MBB, I, DL, get(Opc), DestReg);
} else
// Can't copy this register
return false;
return true;
}
if (DestRC == Mips::CPURegsRegisterClass)
BuildMI(MBB, I, DL, get(Mips::ADDu), DestReg).addReg(Mips::ZERO)
.addReg(SrcReg);
else if (DestRC == Mips::FGR32RegisterClass)
BuildMI(MBB, I, DL, get(Mips::FMOV_S32), DestReg).addReg(SrcReg);
else if (DestRC == Mips::AFGR64RegisterClass)
BuildMI(MBB, I, DL, get(Mips::FMOV_D32), DestReg).addReg(SrcReg);
else if (DestRC == Mips::CCRRegisterClass)
BuildMI(MBB, I, DL, get(Mips::MOVCCRToCCR), DestReg).addReg(SrcReg);
else
// Can't copy this register
return false;
return true;
}
void MipsInstrInfo::
storeRegToStackSlot(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
unsigned SrcReg, bool isKill, int FI,
const TargetRegisterClass *RC) const {
DebugLoc DL = DebugLoc::getUnknownLoc();
if (I != MBB.end()) DL = I->getDebugLoc();
if (RC == Mips::CPURegsRegisterClass)
BuildMI(MBB, I, DL, get(Mips::SW)).addReg(SrcReg, getKillRegState(isKill))
.addImm(0).addFrameIndex(FI);
else if (RC == Mips::FGR32RegisterClass)
BuildMI(MBB, I, DL, get(Mips::SWC1)).addReg(SrcReg, getKillRegState(isKill))
.addImm(0).addFrameIndex(FI);
else if (RC == Mips::AFGR64RegisterClass) {
if (!TM.getSubtarget<MipsSubtarget>().isMips1()) {
BuildMI(MBB, I, DL, get(Mips::SDC1))
.addReg(SrcReg, getKillRegState(isKill))
.addImm(0).addFrameIndex(FI);
} else {
const TargetRegisterInfo *TRI =
MBB.getParent()->getTarget().getRegisterInfo();
const unsigned *SubSet = TRI->getSubRegisters(SrcReg);
BuildMI(MBB, I, DL, get(Mips::SWC1))
.addReg(SubSet[0], getKillRegState(isKill))
.addImm(0).addFrameIndex(FI);
BuildMI(MBB, I, DL, get(Mips::SWC1))
.addReg(SubSet[1], getKillRegState(isKill))
.addImm(4).addFrameIndex(FI);
}
} else
llvm_unreachable("Register class not handled!");
}
void MipsInstrInfo::
loadRegFromStackSlot(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
unsigned DestReg, int FI,
const TargetRegisterClass *RC) const
{
DebugLoc DL = DebugLoc::getUnknownLoc();
if (I != MBB.end()) DL = I->getDebugLoc();
if (RC == Mips::CPURegsRegisterClass)
BuildMI(MBB, I, DL, get(Mips::LW), DestReg).addImm(0).addFrameIndex(FI);
else if (RC == Mips::FGR32RegisterClass)
BuildMI(MBB, I, DL, get(Mips::LWC1), DestReg).addImm(0).addFrameIndex(FI);
else if (RC == Mips::AFGR64RegisterClass) {
if (!TM.getSubtarget<MipsSubtarget>().isMips1()) {
BuildMI(MBB, I, DL, get(Mips::LDC1), DestReg).addImm(0).addFrameIndex(FI);
} else {
const TargetRegisterInfo *TRI =
MBB.getParent()->getTarget().getRegisterInfo();
const unsigned *SubSet = TRI->getSubRegisters(DestReg);
BuildMI(MBB, I, DL, get(Mips::LWC1), SubSet[0])
.addImm(0).addFrameIndex(FI);
BuildMI(MBB, I, DL, get(Mips::LWC1), SubSet[1])
.addImm(4).addFrameIndex(FI);
}
} else
llvm_unreachable("Register class not handled!");
}
MachineInstr *MipsInstrInfo::
foldMemoryOperandImpl(MachineFunction &MF,
MachineInstr* MI,
const SmallVectorImpl<unsigned> &Ops, int FI) const
{
if (Ops.size() != 1) return NULL;
MachineInstr *NewMI = NULL;
switch (MI->getOpcode()) {
case Mips::ADDu:
if ((MI->getOperand(0).isReg()) &&
(MI->getOperand(1).isReg()) &&
(MI->getOperand(1).getReg() == Mips::ZERO) &&
(MI->getOperand(2).isReg())) {
if (Ops[0] == 0) { // COPY -> STORE
unsigned SrcReg = MI->getOperand(2).getReg();
bool isKill = MI->getOperand(2).isKill();
bool isUndef = MI->getOperand(2).isUndef();
NewMI = BuildMI(MF, MI->getDebugLoc(), get(Mips::SW))
.addReg(SrcReg, getKillRegState(isKill) | getUndefRegState(isUndef))
.addImm(0).addFrameIndex(FI);
} else { // COPY -> LOAD
unsigned DstReg = MI->getOperand(0).getReg();
bool isDead = MI->getOperand(0).isDead();
bool isUndef = MI->getOperand(0).isUndef();
NewMI = BuildMI(MF, MI->getDebugLoc(), get(Mips::LW))
.addReg(DstReg, RegState::Define | getDeadRegState(isDead) |
getUndefRegState(isUndef))
.addImm(0).addFrameIndex(FI);
}
}
break;
case Mips::FMOV_S32:
case Mips::FMOV_D32:
if ((MI->getOperand(0).isReg()) &&
(MI->getOperand(1).isReg())) {
const TargetRegisterClass
*RC = RI.getRegClass(MI->getOperand(0).getReg());
unsigned StoreOpc, LoadOpc;
bool IsMips1 = TM.getSubtarget<MipsSubtarget>().isMips1();
if (RC == Mips::FGR32RegisterClass) {
LoadOpc = Mips::LWC1; StoreOpc = Mips::SWC1;
} else {
assert(RC == Mips::AFGR64RegisterClass);
// Mips1 doesn't have ldc/sdc instructions.
if (IsMips1) break;
LoadOpc = Mips::LDC1; StoreOpc = Mips::SDC1;
}
if (Ops[0] == 0) { // COPY -> STORE
unsigned SrcReg = MI->getOperand(1).getReg();
bool isKill = MI->getOperand(1).isKill();
bool isUndef = MI->getOperand(2).isUndef();
NewMI = BuildMI(MF, MI->getDebugLoc(), get(StoreOpc))
.addReg(SrcReg, getKillRegState(isKill) | getUndefRegState(isUndef))
.addImm(0).addFrameIndex(FI) ;
} else { // COPY -> LOAD
unsigned DstReg = MI->getOperand(0).getReg();
bool isDead = MI->getOperand(0).isDead();
bool isUndef = MI->getOperand(0).isUndef();
NewMI = BuildMI(MF, MI->getDebugLoc(), get(LoadOpc))
.addReg(DstReg, RegState::Define | getDeadRegState(isDead) |
getUndefRegState(isUndef))
.addImm(0).addFrameIndex(FI);
}
}
break;
}
return NewMI;
}
//===----------------------------------------------------------------------===//
// Branch Analysis
//===----------------------------------------------------------------------===//
/// GetCondFromBranchOpc - Return the Mips CC that matches
/// the correspondent Branch instruction opcode.
static Mips::CondCode GetCondFromBranchOpc(unsigned BrOpc)
{
switch (BrOpc) {
default: return Mips::COND_INVALID;
case Mips::BEQ : return Mips::COND_E;
case Mips::BNE : return Mips::COND_NE;
case Mips::BGTZ : return Mips::COND_GZ;
case Mips::BGEZ : return Mips::COND_GEZ;
case Mips::BLTZ : return Mips::COND_LZ;
case Mips::BLEZ : return Mips::COND_LEZ;
// We dont do fp branch analysis yet!
case Mips::BC1T :
case Mips::BC1F : return Mips::COND_INVALID;
}
}
/// GetCondBranchFromCond - Return the Branch instruction
/// opcode that matches the cc.
unsigned Mips::GetCondBranchFromCond(Mips::CondCode CC)
{
switch (CC) {
default: llvm_unreachable("Illegal condition code!");
case Mips::COND_E : return Mips::BEQ;
case Mips::COND_NE : return Mips::BNE;
case Mips::COND_GZ : return Mips::BGTZ;
case Mips::COND_GEZ : return Mips::BGEZ;
case Mips::COND_LZ : return Mips::BLTZ;
case Mips::COND_LEZ : return Mips::BLEZ;
case Mips::FCOND_F:
case Mips::FCOND_UN:
case Mips::FCOND_EQ:
case Mips::FCOND_UEQ:
case Mips::FCOND_OLT:
case Mips::FCOND_ULT:
case Mips::FCOND_OLE:
case Mips::FCOND_ULE:
case Mips::FCOND_SF:
case Mips::FCOND_NGLE:
case Mips::FCOND_SEQ:
case Mips::FCOND_NGL:
case Mips::FCOND_LT:
case Mips::FCOND_NGE:
case Mips::FCOND_LE:
case Mips::FCOND_NGT: return Mips::BC1T;
case Mips::FCOND_T:
case Mips::FCOND_OR:
case Mips::FCOND_NEQ:
case Mips::FCOND_OGL:
case Mips::FCOND_UGE:
case Mips::FCOND_OGE:
case Mips::FCOND_UGT:
case Mips::FCOND_OGT:
case Mips::FCOND_ST:
case Mips::FCOND_GLE:
case Mips::FCOND_SNE:
case Mips::FCOND_GL:
case Mips::FCOND_NLT:
case Mips::FCOND_GE:
case Mips::FCOND_NLE:
case Mips::FCOND_GT: return Mips::BC1F;
}
}
/// GetOppositeBranchCondition - Return the inverse of the specified
/// condition, e.g. turning COND_E to COND_NE.
Mips::CondCode Mips::GetOppositeBranchCondition(Mips::CondCode CC)
{
switch (CC) {
default: llvm_unreachable("Illegal condition code!");
case Mips::COND_E : return Mips::COND_NE;
case Mips::COND_NE : return Mips::COND_E;
case Mips::COND_GZ : return Mips::COND_LEZ;
case Mips::COND_GEZ : return Mips::COND_LZ;
case Mips::COND_LZ : return Mips::COND_GEZ;
case Mips::COND_LEZ : return Mips::COND_GZ;
case Mips::FCOND_F : return Mips::FCOND_T;
case Mips::FCOND_UN : return Mips::FCOND_OR;
case Mips::FCOND_EQ : return Mips::FCOND_NEQ;
case Mips::FCOND_UEQ: return Mips::FCOND_OGL;
case Mips::FCOND_OLT: return Mips::FCOND_UGE;
case Mips::FCOND_ULT: return Mips::FCOND_OGE;
case Mips::FCOND_OLE: return Mips::FCOND_UGT;
case Mips::FCOND_ULE: return Mips::FCOND_OGT;
case Mips::FCOND_SF: return Mips::FCOND_ST;
case Mips::FCOND_NGLE:return Mips::FCOND_GLE;
case Mips::FCOND_SEQ: return Mips::FCOND_SNE;
case Mips::FCOND_NGL: return Mips::FCOND_GL;
case Mips::FCOND_LT: return Mips::FCOND_NLT;
case Mips::FCOND_NGE: return Mips::FCOND_GE;
case Mips::FCOND_LE: return Mips::FCOND_NLE;
case Mips::FCOND_NGT: return Mips::FCOND_GT;
}
}
bool MipsInstrInfo::AnalyzeBranch(MachineBasicBlock &MBB,
MachineBasicBlock *&TBB,
MachineBasicBlock *&FBB,
SmallVectorImpl<MachineOperand> &Cond,
bool AllowModify) const
{
// If the block has no terminators, it just falls into the block after it.
MachineBasicBlock::iterator I = MBB.end();
if (I == MBB.begin() || !isUnpredicatedTerminator(--I))
return false;
// Get the last instruction in the block.
MachineInstr *LastInst = I;
// If there is only one terminator instruction, process it.
unsigned LastOpc = LastInst->getOpcode();
if (I == MBB.begin() || !isUnpredicatedTerminator(--I)) {
if (!LastInst->getDesc().isBranch())
return true;
// Unconditional branch
if (LastOpc == Mips::J) {
TBB = LastInst->getOperand(0).getMBB();
return false;
}
Mips::CondCode BranchCode = GetCondFromBranchOpc(LastInst->getOpcode());
if (BranchCode == Mips::COND_INVALID)
return true; // Can't handle indirect branch.
// Conditional branch
// Block ends with fall-through condbranch.
if (LastOpc != Mips::COND_INVALID) {
int LastNumOp = LastInst->getNumOperands();
TBB = LastInst->getOperand(LastNumOp-1).getMBB();
Cond.push_back(MachineOperand::CreateImm(BranchCode));
for (int i=0; i<LastNumOp-1; i++) {
Cond.push_back(LastInst->getOperand(i));
}
return false;
}
}
// Get the instruction before it if it is a terminator.
MachineInstr *SecondLastInst = I;
// If there are three terminators, we don't know what sort of block this is.
if (SecondLastInst && I != MBB.begin() && isUnpredicatedTerminator(--I))
return true;
// If the block ends with Mips::J and a Mips::BNE/Mips::BEQ, handle it.
unsigned SecondLastOpc = SecondLastInst->getOpcode();
Mips::CondCode BranchCode = GetCondFromBranchOpc(SecondLastOpc);
if (BranchCode != Mips::COND_INVALID && LastOpc == Mips::J) {
int SecondNumOp = SecondLastInst->getNumOperands();
TBB = SecondLastInst->getOperand(SecondNumOp-1).getMBB();
Cond.push_back(MachineOperand::CreateImm(BranchCode));
for (int i=0; i<SecondNumOp-1; i++) {
Cond.push_back(SecondLastInst->getOperand(i));
}
FBB = LastInst->getOperand(0).getMBB();
return false;
}
// If the block ends with two unconditional branches, handle it. The last
// one is not executed, so remove it.
if ((SecondLastOpc == Mips::J) && (LastOpc == Mips::J)) {
TBB = SecondLastInst->getOperand(0).getMBB();
I = LastInst;
if (AllowModify)
I->eraseFromParent();
return false;
}
// Otherwise, can't handle this.
return true;
}
unsigned MipsInstrInfo::
InsertBranch(MachineBasicBlock &MBB, MachineBasicBlock *TBB,
MachineBasicBlock *FBB,
const SmallVectorImpl<MachineOperand> &Cond) const {
// FIXME this should probably have a DebugLoc argument
DebugLoc dl = DebugLoc::getUnknownLoc();
// Shouldn't be a fall through.
assert(TBB && "InsertBranch must not be told to insert a fallthrough");
assert((Cond.size() == 3 || Cond.size() == 2 || Cond.size() == 0) &&
"Mips branch conditions can have two|three components!");
if (FBB == 0) { // One way branch.
if (Cond.empty()) {
// Unconditional branch?
BuildMI(&MBB, dl, get(Mips::J)).addMBB(TBB);
} else {
// Conditional branch.
unsigned Opc = GetCondBranchFromCond((Mips::CondCode)Cond[0].getImm());
const TargetInstrDesc &TID = get(Opc);
if (TID.getNumOperands() == 3)
BuildMI(&MBB, dl, TID).addReg(Cond[1].getReg())
.addReg(Cond[2].getReg())
.addMBB(TBB);
else
BuildMI(&MBB, dl, TID).addReg(Cond[1].getReg())
.addMBB(TBB);
}
return 1;
}
// Two-way Conditional branch.
unsigned Opc = GetCondBranchFromCond((Mips::CondCode)Cond[0].getImm());
const TargetInstrDesc &TID = get(Opc);
if (TID.getNumOperands() == 3)
BuildMI(&MBB, dl, TID).addReg(Cond[1].getReg()).addReg(Cond[2].getReg())
.addMBB(TBB);
else
BuildMI(&MBB, dl, TID).addReg(Cond[1].getReg()).addMBB(TBB);
BuildMI(&MBB, dl, get(Mips::J)).addMBB(FBB);
return 2;
}
unsigned MipsInstrInfo::
RemoveBranch(MachineBasicBlock &MBB) const
{
MachineBasicBlock::iterator I = MBB.end();
if (I == MBB.begin()) return 0;
--I;
if (I->getOpcode() != Mips::J &&
GetCondFromBranchOpc(I->getOpcode()) == Mips::COND_INVALID)
return 0;
// Remove the branch.
I->eraseFromParent();
I = MBB.end();
if (I == MBB.begin()) return 1;
--I;
if (GetCondFromBranchOpc(I->getOpcode()) == Mips::COND_INVALID)
return 1;
// Remove the branch.
I->eraseFromParent();
return 2;
}
/// ReverseBranchCondition - Return the inverse opcode of the
/// specified Branch instruction.
bool MipsInstrInfo::
ReverseBranchCondition(SmallVectorImpl<MachineOperand> &Cond) const
{
assert( (Cond.size() == 3 || Cond.size() == 2) &&
"Invalid Mips branch condition!");
Cond[0].setImm(GetOppositeBranchCondition((Mips::CondCode)Cond[0].getImm()));
return false;
}
/// getGlobalBaseReg - Return a virtual register initialized with the
/// the global base register value. Output instructions required to
/// initialize the register in the function entry block, if necessary.
///
unsigned MipsInstrInfo::getGlobalBaseReg(MachineFunction *MF) const {
MipsFunctionInfo *MipsFI = MF->getInfo<MipsFunctionInfo>();
unsigned GlobalBaseReg = MipsFI->getGlobalBaseReg();
if (GlobalBaseReg != 0)
return GlobalBaseReg;
// Insert the set of GlobalBaseReg into the first MBB of the function
MachineBasicBlock &FirstMBB = MF->front();
MachineBasicBlock::iterator MBBI = FirstMBB.begin();
MachineRegisterInfo &RegInfo = MF->getRegInfo();
const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
GlobalBaseReg = RegInfo.createVirtualRegister(Mips::CPURegsRegisterClass);
bool Ok = TII->copyRegToReg(FirstMBB, MBBI, GlobalBaseReg, Mips::GP,
Mips::CPURegsRegisterClass,
Mips::CPURegsRegisterClass);
assert(Ok && "Couldn't assign to global base register!");
Ok = Ok; // Silence warning when assertions are turned off.
RegInfo.addLiveIn(Mips::GP);
MipsFI->setGlobalBaseReg(GlobalBaseReg);
return GlobalBaseReg;
}
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