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Better handle instructions that re-def a scratch register

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llvm-svn: 84657
This commit is contained in:
Jim Grosbach 2009-10-20 19:52:35 +00:00
parent 6b54c70e78
commit 7800d00f20
1 changed files with 18 additions and 9 deletions
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27
lib/CodeGen/PrologEpilogInserter.cpp
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@ -778,6 +778,8 @@ void PEI::scavengeFrameVirtualRegs(MachineFunction &Fn) {
// directly.
for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ++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()) {
MachineOperand &MO = MI->getOperand(i);
@ -802,6 +804,12 @@ void PEI::scavengeFrameVirtualRegs(MachineFunction &Fn) {
}
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) {
@ -866,19 +874,20 @@ void PEI::scavengeFrameVirtualRegs(MachineFunction &Fn) {
assert (CurrentScratchReg && "Missing scratch register!");
MI->getOperand(i).setReg(CurrentScratchReg);
// If this is the last use of the register, stop tracking it.
if (MI->getOperand(i).isKill()) {
PrevScratchReg = CurrentScratchReg;
PrevLastUseMI = MI;
isKillInsn = true;
PrevLastUseOp = i;
CurrentScratchReg = CurrentVirtReg = 0;
havePrevValue = trackingCurrentValue;
// Re-scan the operands of this instruction to catch definitions
// of the scratch register we're using. This is to handle things
// like ldr "r2, [scratch]" where scratch is r2.
i = 0;
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) {
PrevScratchReg = CurrentScratchReg;
CurrentScratchReg = CurrentVirtReg = 0;
havePrevValue = trackingCurrentValue;
}
RS->forward(MI);
}
}