+/// \brief If we change a kill flag on the bundle instruction implicit register
+/// operands, then we also need to propagate that to any instructions inside
+/// the bundle which had the same kill state.
+static void toggleBundleKillFlag(MachineInstr *MI, unsigned Reg,
+ bool NewKillState) {
+ if (MI->getOpcode() != TargetOpcode::BUNDLE)
+ return;
+
+ // Walk backwards from the last instruction in the bundle to the first.
+ // Once we set a kill flag on an instruction, we bail out, as otherwise we
+ // might set it on too many operands. We will clear as many flags as we
+ // can though.
+ MachineBasicBlock::instr_iterator Begin = MI;
+ MachineBasicBlock::instr_iterator End = getBundleEnd(MI);
+ while (Begin != End) {
+ for (MachineOperand &MO : (--End)->operands()) {
+ if (!MO.isReg() || MO.isDef() || Reg != MO.getReg())
+ continue;
+
+ // DEBUG_VALUE nodes do not contribute to code generation and should
+ // always be ignored. Failure to do so may result in trying to modify
+ // KILL flags on DEBUG_VALUE nodes, which is distressing.
+ if (MO.isDebug())
+ continue;
+
+ // If the register has the internal flag then it could be killing an
+ // internal def of the register. In this case, just skip. We only want
+ // to toggle the flag on operands visible outside the bundle.
+ if (MO.isInternalRead())
+ continue;
+
+ if (MO.isKill() == NewKillState)
+ continue;
+ MO.setIsKill(NewKillState);
+ if (NewKillState)
+ return;
+ }
+ }
+}
+