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When checking if something's killed, don't rely simply on whether it's marked as 

"used outside of the block". If the block ends in a return, then it won't be
used outside of it.

llvm-svn: 98599
This commit is contained in:
Bill Wendling 2010-03-16 01:05:35 +00:00
parent 874cc62876
commit a8f54f032d
1 changed files with 15 additions and 8 deletions
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23
llvm/lib/CodeGen/RegAllocLocal.cpp
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@ -671,7 +671,8 @@ void RALocal::ComputeLocalLiveness(MachineBasicBlock& MBB) {
// Live-out (of the function) registers contain return values of the function,
// so we need to make sure they are alive at return time.
if (!MBB.empty() && MBB.back().getDesc().isReturn()) {
bool BBEndsInReturn = !MBB.empty() && MBB.back().getDesc().isReturn();
if (BBEndsInReturn) {
MachineInstr* Ret = &MBB.back();
for (MachineRegisterInfo::liveout_iterator
I = MF->getRegInfo().liveout_begin(),
@ -696,7 +697,10 @@ void RALocal::ComputeLocalLiveness(MachineBasicBlock& MBB) {
bool usedOutsideBlock = isPhysReg ? false :
UsedInMultipleBlocks.test(MO.getReg() -
TargetRegisterInfo::FirstVirtualRegister);
if (!isPhysReg && !usedOutsideBlock) {
// If the machine BB ends in a return instruction, then the value isn't used
// outside of the BB.
if (!isPhysReg && (!usedOutsideBlock || BBEndsInReturn)) {
// DBG_VALUE complicates this: if the only refs of a register outside
// this block are DBG_VALUE, we can't keep the reg live just for that,
// as it will cause the reg to be spilled at the end of this block when
@ -704,7 +708,7 @@ void RALocal::ComputeLocalLiveness(MachineBasicBlock& MBB) {
// happens.
bool UsedByDebugValueOnly = false;
for (MachineRegisterInfo::reg_iterator UI = MRI.reg_begin(MO.getReg()),
UE = MRI.reg_end(); UI != UE; ++UI)
UE = MRI.reg_end(); UI != UE; ++UI) {
// Two cases:
// - used in another block
// - used in the same block before it is defined (loop)
@ -714,6 +718,7 @@ void RALocal::ComputeLocalLiveness(MachineBasicBlock& MBB) {
UsedByDebugValueOnly = true;
continue;
}
// A non-DBG_VALUE use means we can leave DBG_VALUE uses alone.
UsedInMultipleBlocks.set(MO.getReg() -
TargetRegisterInfo::FirstVirtualRegister);
@ -721,6 +726,8 @@ void RALocal::ComputeLocalLiveness(MachineBasicBlock& MBB) {
UsedByDebugValueOnly = false;
break;
}
}
if (UsedByDebugValueOnly)
for (MachineRegisterInfo::reg_iterator UI = MRI.reg_begin(MO.getReg()),
UE = MRI.reg_end(); UI != UE; ++UI)
@ -730,16 +737,16 @@ void RALocal::ComputeLocalLiveness(MachineBasicBlock& MBB) {
UI.getOperand().setReg(0U);
}
// Physical registers and those that are not live-out of the block
// are killed/dead at their last use/def within this block.
if (isPhysReg || !usedOutsideBlock) {
// Physical registers and those that are not live-out of the block are
// killed/dead at their last use/def within this block.
if (isPhysReg || !usedOutsideBlock || BBEndsInReturn)
if (MO.isUse()) {
// Don't mark uses that are tied to defs as kills.
if (!MI->isRegTiedToDefOperand(idx))
MO.setIsKill(true);
} else
} else {
MO.setIsDead(true);
}
}
}
}