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When processing frame index virtual registers, consider all available registers

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(if there are any) and use the one which remains available for the longest
rather than just using the first one. This should help enable better re-use
of the loaded frame index values. rdar://7318760



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@107847 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jim Grosbach
2010-07-08 00:38:54 +00:00
parent 0238f8c430
commit d9642faf7c
3 changed files with 37 additions and 8 deletions
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14
lib/CodeGen/PrologEpilogInserter.cpp
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@@ -885,10 +885,20 @@ void PEI::scavengeFrameVirtualRegs(MachineFunction &Fn) {
// Scavenge a new scratch register
CurrentVirtReg = Reg;
const TargetRegisterClass *RC = Fn.getRegInfo().getRegClass(Reg);
CurrentScratchReg = RS->FindUnusedReg(RC);
if (CurrentScratchReg == 0)
const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
BitVector Candidates(TRI->getNumRegs());
RS->getRegsAvailable(RC, Candidates);
// If there are any registers available, use the one that's
// unused for the longest after this instruction. That increases
// the ability to reuse the value.
if (Candidates.any()) {
MachineBasicBlock::iterator UMI;
CurrentScratchReg = RS->findSurvivorReg(I, Candidates, 25, UMI);
} else {
// No register is "free". Scavenge a register.
CurrentScratchReg = RS->scavengeRegister(RC, I, SPAdj);
}
PrevValue = Value;
}