+ // Go through implicit defs of CSMI and MI, and clear the kill flags on
+ // their uses in all the instructions between CSMI and MI.
+ // We might have made some of the kill flags redundant, consider:
+ // subs ... %NZCV<imp-def> <- CSMI
+ // csinc ... %NZCV<imp-use,kill> <- this kill flag isn't valid anymore
+ // subs ... %NZCV<imp-def> <- MI, to be eliminated
+ // csinc ... %NZCV<imp-use,kill>
+ // Since we eliminated MI, and reused a register imp-def'd by CSMI
+ // (here %NZCV), that register, if it was killed before MI, should have
+ // that kill flag removed, because it's lifetime was extended.
+ if (CSMI->getParent() == MI->getParent()) {
+ for (MachineBasicBlock::iterator II = CSMI, IE = MI; II != IE; ++II)
+ for (auto ImplicitDef : ImplicitDefs)
+ if (MachineOperand *MO = II->findRegisterUseOperand(
+ ImplicitDef, /*isKill=*/true, TRI))
+ MO->setIsKill(false);
+ } else {
+ // If the instructions aren't in the same BB, bail out and clear the
+ // kill flag on all uses of the imp-def'd register.
+ for (auto ImplicitDef : ImplicitDefs)
+ MRI->clearKillFlags(ImplicitDef);
+ }
+