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Use a spilled free callee-saved register as scratch register.

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llvm-svn: 34785
This commit is contained in:
Evan Cheng 2007-03-01 08:57:52 +00:00
parent 0aa68b9246
commit 07dcde8ba2
1 changed files with 17 additions and 3 deletions
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20
lib/Target/ARM/ARMRegisterInfo.cpp
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@ -313,6 +313,7 @@ ARMRegisterInfo::getCalleeSavedRegClasses() const {
}
BitVector ARMRegisterInfo::getReservedRegs(const MachineFunction &MF) const {
// FIXME: avoid re-calculating this everytime.
BitVector Reserved(getNumRegs());
Reserved.set(ARM::SP);
Reserved.set(ARM::PC);
@ -619,6 +620,20 @@ static void emitThumbConstant(MachineBasicBlock &MBB,
.addReg(DestReg, false, false, true);
}
/// findScratchRegister - Find a 'free' ARM register. If register scavenger
/// is not being used, R12 is available. Otherwise, try for a call-clobbered
/// register first and then a spilled callee-saved register if that fails.
static
unsigned findScratchRegister(RegScavenger *RS, const TargetRegisterClass *RC,
ARMFunctionInfo *AFI) {
unsigned Reg = RS ? RS->FindUnusedReg(RC, true) : (unsigned) ARM::R12;
if (Reg == 0)
// Try a already spilled CS register.
Reg = RS->FindUnusedReg(RC, AFI->getSpilledCSRegisters());
return Reg;
}
void ARMRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
RegScavenger *RS) const{
unsigned i = 0;
@ -902,9 +917,8 @@ void ARMRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
// If the offset we have is too large to fit into the instruction, we need
// to form it with a series of ADDri's. Do this by taking 8-bit chunks
// out of 'Offset'.
unsigned ScratchReg = RS
? RS->FindUnusedReg(&ARM::GPRRegClass, true) : (unsigned)ARM::R12;
assert(ScratchReg != 0 && "Unable to find a free call-clobbered register!");
unsigned ScratchReg = findScratchRegister(RS, &ARM::GPRRegClass, AFI);
assert(ScratchReg && "Unable to find a free register!");
emitARMRegPlusImmediate(MBB, II, ScratchReg, FrameReg,
isSub ? -Offset : Offset, TII);
MI.getOperand(i).ChangeToRegister(ScratchReg, false, false, true);