+unsigned
+MachineBasicBlock::addLiveIn(unsigned PhysReg, const TargetRegisterClass *RC) {
+ assert(getParent() && "MBB must be inserted in function");
+ assert(TargetRegisterInfo::isPhysicalRegister(PhysReg) && "Expected physreg");
+ assert(RC && "Register class is required");
+ assert((isLandingPad() || this == &getParent()->front()) &&
+ "Only the entry block and landing pads can have physreg live ins");
+
+ bool LiveIn = isLiveIn(PhysReg);
+ iterator I = SkipPHIsAndLabels(begin()), E = end();
+ MachineRegisterInfo &MRI = getParent()->getRegInfo();
+ const TargetInstrInfo &TII = *getParent()->getSubtarget().getInstrInfo();
+
+ // Look for an existing copy.
+ if (LiveIn)
+ for (;I != E && I->isCopy(); ++I)
+ if (I->getOperand(1).getReg() == PhysReg) {
+ unsigned VirtReg = I->getOperand(0).getReg();
+ if (!MRI.constrainRegClass(VirtReg, RC))
+ llvm_unreachable("Incompatible live-in register class.");
+ return VirtReg;
+ }
+
+ // No luck, create a virtual register.
+ unsigned VirtReg = MRI.createVirtualRegister(RC);
+ BuildMI(*this, I, DebugLoc(), TII.get(TargetOpcode::COPY), VirtReg)
+ .addReg(PhysReg, RegState::Kill);
+ if (!LiveIn)
+ addLiveIn(PhysReg);
+ return VirtReg;
+}
+