I noticed some inconsistency regarding tied use operands and
InstrEmitter::AddRegisterOperand() says tied use operands are never killed.
MachineInstr::addRegisterKilled() says that “Two-address uses of physregs must not be marked kill”, but allows tied VReg uses be marked as killed.
LiveVariables pass also adds this flag on tied uses while
LiveInterval pass apparently clears it.
What is correct behavior here? Is it documented somewhere?