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Allow Post-RA LICM to hoist reserved register reads. 

When using register masks, registers like %rip are clobbered by the
register mask. LICM should still be able to hoist instructions reading
%rip from a loop containing calls.

llvm-svn: 150288
This commit is contained in:
Jakob Stoklund Olesen 2012-02-11 00:44:19 +00:00
parent 17402e3d5a
commit fd338e9777
1 changed files with 11 additions and 0 deletions
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11
llvm/lib/CodeGen/MachineLICM.cpp
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@ -68,6 +68,7 @@ namespace {
MachineRegisterInfo *MRI;
const InstrItineraryData *InstrItins;
bool PreRegAlloc;
BitVector ReservedRegs;
// Various analyses that we use...
AliasAnalysis *AA; // Alias analysis info.
@ -337,6 +338,8 @@ bool MachineLICM::runOnMachineFunction(MachineFunction &MF) {
for (TargetRegisterInfo::regclass_iterator I = TRI->regclass_begin(),
E = TRI->regclass_end(); I != E; ++I)
RegLimit[(*I)->getID()] = TRI->getRegPressureLimit(*I, MF);
} else {
ReservedRegs = TRI->getReservedRegs(MF);
}
// Get our Loop information...
@ -426,6 +429,9 @@ void MachineLICM::ProcessMI(MachineInstr *MI,
"Not expecting virtual register!");
if (!MO.isDef()) {
// Allow reserved register reads to be hoisted.
if (ReservedRegs.test(Reg))
continue;
if (Reg && (PhysRegDefs.test(Reg) || PhysRegClobbers.test(Reg)))
// If it's using a non-loop-invariant register, then it's obviously not
// safe to hoist.
@ -531,6 +537,11 @@ void MachineLICM::HoistRegionPostRA() {
const MachineOperand &MO = MI->getOperand(j);
if (!MO.isReg() || MO.isDef() || !MO.getReg())
continue;
// Allow hoisting of reserved register reads that aren't call preserved.
// For example %rip.
// IsLoopInvariantInst() already checks MRI->isConstantPhysReg().
if (ReservedRegs.test(MO.getReg()))
continue;
if (PhysRegDefs.test(MO.getReg()) ||
PhysRegClobbers.test(MO.getReg())) {
// If it's using a non-loop-invariant register, then it's obviously