+/// addRetOperand - ensure that a return instruction has an operand for each
+/// value live out of the function.
+///
+/// Things marked both call and return are tail calls; do not do this for them.
+/// The tail callee need not take the same registers as input that it produces
+/// as output, and there are dependencies for its input registers elsewhere.
+///
+/// FIXME: This should be done as part of instruction selection, and this helper
+/// should be deleted. Until then, we use custom logic here to create the proper
+/// operand under all circumstances. We can't use addRegisterKilled because that
+/// doesn't make sense for undefined values. We can't simply avoid calling it
+/// for undefined values, because we must ensure that the operand always exists.
+void RAFast::addRetOperands(MachineBasicBlock *MBB) {
+ if (MBB->empty() || !MBB->back().isReturn() || MBB->back().isCall())
+ return;
+
+ MachineInstr *MI = &MBB->back();
+
+ for (MachineRegisterInfo::liveout_iterator
+ I = MBB->getParent()->getRegInfo().liveout_begin(),
+ E = MBB->getParent()->getRegInfo().liveout_end(); I != E; ++I) {
+ unsigned Reg = *I;
+ assert(TargetRegisterInfo::isPhysicalRegister(Reg) &&
+ "Cannot have a live-out virtual register.");
+
+ bool hasDef = PhysRegState[Reg] == regReserved;
+
+ // Check if this register already has an operand.
+ bool Found = false;
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ MachineOperand &MO = MI->getOperand(i);
+ if (!MO.isReg() || !MO.isUse())
+ continue;
+
+ unsigned OperReg = MO.getReg();
+ if (!TargetRegisterInfo::isPhysicalRegister(OperReg))
+ continue;
+
+ if (OperReg == Reg || TRI->isSuperRegister(OperReg, Reg)) {
+ // If the ret already has an operand for this physreg or a superset,
+ // don't duplicate it. Set the kill flag if the value is defined.
+ if (hasDef && !MO.isKill())
+ MO.setIsKill();
+ Found = true;
+ break;
+ }
+ }
+ if (!Found)
+ MI->addOperand(MachineOperand::CreateReg(Reg,
+ false /*IsDef*/,
+ true /*IsImp*/,
+ hasDef/*IsKill*/));
+ }
+}
+