/// 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({
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);
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!