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Teach TransferDeadness to delete truly dead instructions if they do not produce side effects.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@71606 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng
2009-05-12 23:07:00 +00:00
parent 3b895cfac9
commit eca24fba3f
3 changed files with 61 additions and 21 deletions
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31
lib/CodeGen/RegAllocLinearScan.cpp
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@@ -350,29 +350,44 @@ unsigned RALinScan::attemptTrivialCoalescing(LiveInterval &cur, unsigned Reg) {
if (!vni->def || vni->def == ~1U || vni->def == ~0U)
return Reg;
MachineInstr *CopyMI = li_->getInstructionFromIndex(vni->def);
unsigned SrcReg, DstReg, SrcSubReg, DstSubReg;
unsigned SrcReg, DstReg, SrcSubReg, DstSubReg, PhysReg;
if (!CopyMI ||
!tii_->isMoveInstr(*CopyMI, SrcReg, DstReg, SrcSubReg, DstSubReg))
return Reg;
PhysReg = SrcReg;
if (TargetRegisterInfo::isVirtualRegister(SrcReg)) {
if (!vrm_->isAssignedReg(SrcReg))
return Reg;
else
SrcReg = vrm_->getPhys(SrcReg);
PhysReg = vrm_->getPhys(SrcReg);
}
if (Reg == SrcReg)
if (Reg == PhysReg)
return Reg;
const TargetRegisterClass *RC = mri_->getRegClass(cur.reg);
if (!RC->contains(SrcReg))
if (!RC->contains(PhysReg))
return Reg;
// Try to coalesce.
if (!li_->conflictsWithPhysRegDef(cur, *vrm_, SrcReg)) {
DOUT << "Coalescing: " << cur << " -> " << tri_->getName(SrcReg)
if (!li_->conflictsWithPhysRegDef(cur, *vrm_, PhysReg)) {
DOUT << "Coalescing: " << cur << " -> " << tri_->getName(PhysReg)
<< '\n';
vrm_->clearVirt(cur.reg);
vrm_->assignVirt2Phys(cur.reg, SrcReg);
vrm_->assignVirt2Phys(cur.reg, PhysReg);
// Remove unnecessary kills since a copy does not clobber the register.
if (li_->hasInterval(SrcReg)) {
LiveInterval &SrcLI = li_->getInterval(SrcReg);
for (MachineRegisterInfo::reg_iterator I = mri_->reg_begin(cur.reg),
E = mri_->reg_end(); I != E; ++I) {
MachineOperand &O = I.getOperand();
if (!O.isUse() || !O.isKill())
continue;
MachineInstr *MI = &*I;
if (SrcLI.liveAt(li_->getDefIndex(li_->getInstructionIndex(MI))))
O.setIsKill(false);
}
}
++NumCoalesce;
return SrcReg;
}