- for (unsigned i = 0, e = CSEPairs.size(); i != e; ++i) {
- MRI->replaceRegWith(CSEPairs[i].first, CSEPairs[i].second);
- MRI->clearKillFlags(CSEPairs[i].second);
+ for (std::pair<unsigned, unsigned> &CSEPair : CSEPairs) {
+ unsigned OldReg = CSEPair.first;
+ unsigned NewReg = CSEPair.second;
+ // OldReg may have been unused but is used now, clear the Dead flag
+ MachineInstr *Def = MRI->getUniqueVRegDef(NewReg);
+ assert(Def != nullptr && "CSEd register has no unique definition?");
+ Def->clearRegisterDeads(NewReg);
+ // Replace with NewReg and clear kill flags which may be wrong now.
+ MRI->replaceRegWith(OldReg, NewReg);
+ MRI->clearKillFlags(NewReg);