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Expand postra machine licm's capability a little more. If an instruction's register operands are all loop invariants, then it's safe to hoist it.

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llvm-svn: 101167
This commit is contained in:
Evan Cheng 2010-04-13 20:21:05 +00:00
parent a75eedea38
commit bc94b6f1fd
1 changed files with 24 additions and 8 deletions
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32
lib/CodeGen/MachineLICM.cpp
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@ -276,7 +276,7 @@ void MachineLICM::ProcessMI(MachineInstr *MI,
SmallSet<int, 32> &StoredFIs,
SmallVector<CandidateInfo, 32> &Candidates) {
bool RuledOut = false;
bool HasRegFIUse = false;
bool HasNonInvariantUse = false;
unsigned Def = 0;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
@ -287,7 +287,7 @@ void MachineLICM::ProcessMI(MachineInstr *MI,
MFI->isSpillSlotObjectIndex(FI) &&
InstructionStoresToFI(MI, FI))
StoredFIs.insert(FI);
HasRegFIUse = true;
HasNonInvariantUse = true;
continue;
}
@ -300,7 +300,10 @@ void MachineLICM::ProcessMI(MachineInstr *MI,
"Not expecting virtual register!");
if (!MO.isDef()) {
HasRegFIUse = true;
if (PhysRegDefs[Reg])
// If it's using a non-loop-invariant register, then it's obviously not
// safe to hoist.
HasNonInvariantUse = true;
continue;
}
@ -338,9 +341,7 @@ void MachineLICM::ProcessMI(MachineInstr *MI,
// operands. FIXME: Consider unfold load folding instructions.
if (Def && !RuledOut) {
int FI = INT_MIN;
// FIXME: Also hoist instructions if all source operands are live in
// to the loop.
if ((!HasRegFIUse && IsLICMCandidate(*MI)) ||
if ((!HasNonInvariantUse && IsLICMCandidate(*MI)) ||
(TII->isLoadFromStackSlot(MI, FI) && MFI->isSpillSlotObjectIndex(FI)))
Candidates.push_back(CandidateInfo(MI, Def, FI));
}
@ -400,8 +401,23 @@ void MachineLICM::HoistRegionPostRA(MachineDomTreeNode *N) {
StoredFIs.count(Candidates[i].FI))
continue;
if (PhysRegDefs[Candidates[i].Def] == 1)
HoistPostRA(Candidates[i].MI, Candidates[i].Def);
if (PhysRegDefs[Candidates[i].Def] == 1) {
bool Safe = true;
MachineInstr *MI = Candidates[i].MI;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg() || MO.isDef())
continue;
if (PhysRegDefs[MO.getReg()]) {
// If it's using a non-loop-invariant register, then it's obviously
// not safe to hoist.
Safe = false;
break;
}
}
if (Safe)
HoistPostRA(MI, Candidates[i].Def);
}
}
delete[] PhysRegDefs;