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Updated comments to reflect what "side effects" means in this situation.

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llvm-svn: 45245
This commit is contained in:
Bill Wendling 2007-12-20 01:08:10 +00:00
parent 5cbdbd26a8
commit cba1938285
1 changed files with 3 additions and 10 deletions
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13
lib/CodeGen/MachineLICM.cpp
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@ -249,8 +249,8 @@ void MachineLICM::HoistRegion(MachineDomTreeNode *N) {
/// IsLoopInvariantInst - Returns true if the instruction is loop
/// invariant. I.e., all virtual register operands are defined outside of the
/// loop, physical registers aren't accessed (explicitly or implicitly), and the
/// instruction is hoistable.
/// loop, physical registers aren't accessed explicitly, and there are no side
/// effects that aren't captured by the operands or other flags.
///
bool MachineLICM::IsLoopInvariantInst(MachineInstr &I) {
DEBUG({
@ -281,13 +281,6 @@ bool MachineLICM::IsLoopInvariantInst(MachineInstr &I) {
DOUT << " * Instruction has side effects.\n";
});
#if 0
// FIXME: Don't hoist if this instruction implicitly reads physical registers.
if (I.getInstrDescriptor()->ImplicitUses ||
I.getInstrDescriptor()->ImplicitDefs)
return false;
#endif
// The instruction is loop invariant if all of its operands are loop-invariant
for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i) {
const MachineOperand &MO = I.getOperand(i);
@ -309,7 +302,7 @@ bool MachineLICM::IsLoopInvariantInst(MachineInstr &I) {
return false;
}
// Don't hoist something that has side effects.
// Don't hoist something that has unmodelled side effects.
if (TII->hasUnmodelledSideEffects(&I)) return false;
// If we got this far, the instruction is loop invariant!