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Teach LowerSubregs to preserve kill/dead information when lowering 

subreg instructions.

llvm-svn: 61220
This commit is contained in:
Dan Gohman 2008-12-18 22:14:08 +00:00
parent 4c13e77d49
commit 9abd04bf3f
1 changed files with 63 additions and 1 deletions
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64
llvm/lib/CodeGen/LowerSubregs.cpp
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@ -49,6 +49,11 @@ namespace {
bool LowerExtract(MachineInstr *MI);
bool LowerInsert(MachineInstr *MI);
bool LowerSubregToReg(MachineInstr *MI);
void TransferDeadFlag(MachineInstr *MI, unsigned DstReg,
const TargetRegisterInfo &TRI);
void TransferKillFlag(MachineInstr *MI, unsigned SrcReg,
const TargetRegisterInfo &TRI);
};
char LowerSubregsInstructionPass::ID = 0;
@ -58,6 +63,38 @@ FunctionPass *llvm::createLowerSubregsPass() {
return new LowerSubregsInstructionPass();
}
/// TransferDeadFlag - MI is a pseudo-instruction with DstReg dead,
/// and the lowered replacement instructions immediately precede it.
/// Mark the replacement instructions with the dead flag.
void
LowerSubregsInstructionPass::TransferDeadFlag(MachineInstr *MI,
unsigned DstReg,
const TargetRegisterInfo &TRI) {
for (MachineBasicBlock::iterator MII =
prior(MachineBasicBlock::iterator(MI)); ; --MII) {
if (MII->addRegisterDead(DstReg, &TRI))
break;
assert(MII != MI->getParent()->begin() &&
"copyRegToReg output doesn't reference destination register!");
}
}
/// TransferKillFlag - MI is a pseudo-instruction with SrcReg killed,
/// and the lowered replacement instructions immediately precede it.
/// Mark the replacement instructions with the kill flag.
void
LowerSubregsInstructionPass::TransferKillFlag(MachineInstr *MI,
unsigned SrcReg,
const TargetRegisterInfo &TRI) {
for (MachineBasicBlock::iterator MII =
prior(MachineBasicBlock::iterator(MI)); ; --MII) {
if (MII->addRegisterKilled(SrcReg, &TRI))
break;
assert(MII != MI->getParent()->begin() &&
"copyRegToReg output doesn't reference source register!");
}
}
bool LowerSubregsInstructionPass::LowerExtract(MachineInstr *MI) {
MachineBasicBlock *MBB = MI->getParent();
MachineFunction &MF = *MBB->getParent();
@ -83,13 +120,28 @@ bool LowerSubregsInstructionPass::LowerExtract(MachineInstr *MI) {
if (SrcReg == DstReg) {
// No need to insert an identify copy instruction.
DOUT << "subreg: eliminated!";
// Find the kill of the destination register's live range, and insert
// a kill of the source register at that point.
if (MI->getOperand(1).isKill() && !MI->getOperand(0).isDead())
for (MachineBasicBlock::iterator MII =
next(MachineBasicBlock::iterator(MI));
MII != MBB->end(); ++MII)
if (MII->killsRegister(DstReg, &TRI)) {
MII->addRegisterKilled(SuperReg, &TRI, /*AddIfNotFound=*/true);
break;
}
} else {
// Insert copy
const TargetRegisterClass *TRC = TRI.getPhysicalRegisterRegClass(DstReg);
assert(TRC == TRI.getPhysicalRegisterRegClass(SrcReg) &&
"Extract subreg and Dst must be of same register class");
TII.copyRegToReg(*MBB, MI, DstReg, SrcReg, TRC, TRC);
// Transfer the kill/dead flags, if needed.
if (MI->getOperand(0).isDead())
TransferDeadFlag(MI, DstReg, TRI);
if (MI->getOperand(1).isKill())
TransferKillFlag(MI, SrcReg, TRI);
#ifndef NDEBUG
MachineBasicBlock::iterator dMI = MI;
DOUT << "subreg: " << *(--dMI);
@ -133,6 +185,11 @@ bool LowerSubregsInstructionPass::LowerSubregToReg(MachineInstr *MI) {
const TargetRegisterClass *TRC0= TRI.getPhysicalRegisterRegClass(DstSubReg);
const TargetRegisterClass *TRC1= TRI.getPhysicalRegisterRegClass(InsReg);
TII.copyRegToReg(*MBB, MI, DstSubReg, InsReg, TRC0, TRC1);
// Transfer the kill/dead flags, if needed.
if (MI->getOperand(0).isDead())
TransferDeadFlag(MI, DstSubReg, TRI);
if (MI->getOperand(2).isKill())
TransferKillFlag(MI, InsReg, TRI);
#ifndef NDEBUG
MachineBasicBlock::iterator dMI = MI;
@ -181,6 +238,11 @@ bool LowerSubregsInstructionPass::LowerInsert(MachineInstr *MI) {
const TargetRegisterClass *TRC0= TRI.getPhysicalRegisterRegClass(DstSubReg);
const TargetRegisterClass *TRC1= TRI.getPhysicalRegisterRegClass(InsReg);
TII.copyRegToReg(*MBB, MI, DstSubReg, InsReg, TRC0, TRC1);
// Transfer the kill/dead flags, if needed.
if (MI->getOperand(0).isDead())
TransferDeadFlag(MI, DstSubReg, TRI);
if (MI->getOperand(1).isKill())
TransferKillFlag(MI, InsReg, TRI);
#ifndef NDEBUG
MachineBasicBlock::iterator dMI = MI;