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Run dead code elimination immediately after rematerialization.

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This may eliminate some uses of the spilled registers, and we don't want to
insert reloads for that.

llvm-svn: 128468
This commit is contained in:
Jakob Stoklund Olesen 2011-03-29 17:47:00 +00:00
parent 3310282e25
commit 4676323ac8
1 changed files with 24 additions and 9 deletions
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33
lib/CodeGen/InlineSpiller.cpp
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@ -684,8 +684,7 @@ void InlineSpiller::reMaterializeAll() {
for (LiveInterval::vni_iterator I = LI.vni_begin(), E = LI.vni_end();
I != E; ++I) {
VNInfo *VNI = *I;
if (VNI->isUnused() || VNI->isPHIDef() || VNI->hasPHIKill() ||
UsedValues.count(VNI))
if (VNI->isUnused() || VNI->isPHIDef() || UsedValues.count(VNI))
continue;
MachineInstr *MI = LIS.getInstructionFromIndex(VNI->def);
MI->addRegisterDead(Reg, &TRI);
@ -693,14 +692,30 @@ void InlineSpiller::reMaterializeAll() {
continue;
DEBUG(dbgs() << "All defs dead: " << *MI);
DeadDefs.push_back(MI);
// Remove all Reg references so we don't insert spill code around MI.
for (MachineInstr::mop_iterator MOI = MI->operands_begin(),
MOE = MI->operands_end(); MOI != MOE ; ++MOI)
if (MOI->isReg() && MOI->getReg() == Reg)
MOI->setReg(0);
VNI->setIsUnused(true);
}
}
// Eliminate dead code after remat. Note that some snippet copies may be
// deleted here.
if (DeadDefs.empty())
return;
DEBUG(dbgs() << "Remat created " << DeadDefs.size() << " dead defs.\n");
Edit->eliminateDeadDefs(DeadDefs, LIS, VRM, TII);
// Get rid of deleted and empty intervals.
for (unsigned i = RegsToSpill.size(); i != 0; --i) {
unsigned Reg = RegsToSpill[i-1];
if (!LIS.hasInterval(Reg)) {
RegsToSpill.erase(RegsToSpill.begin() + (i - 1));
continue;
}
LiveInterval &LI = LIS.getInterval(Reg);
if (!LI.empty())
continue;
Edit->eraseVirtReg(Reg, LIS);
RegsToSpill.erase(RegsToSpill.begin() + (i - 1));
}
DEBUG(dbgs() << RegsToSpill.size() << " registers to spill after remat.\n");
}
/// If MI is a load or store of StackSlot, it can be removed.
@ -913,7 +928,7 @@ void InlineSpiller::spill(LiveRangeEdit &edit) {
reMaterializeAll();
// Remat may handle everything.
if (Edit->getParent().empty())
if (RegsToSpill.empty())
return;
// Update LiveStacks now that we are committed to spilling.