diff --git a/lib/CodeGen/MachineInstr.cpp b/lib/CodeGen/MachineInstr.cpp
index e008c9a..5da6a31 100644
--- a/lib/CodeGen/MachineInstr.cpp
+++ b/lib/CodeGen/MachineInstr.cpp
@@ -780,6 +780,7 @@
                                    const TargetRegisterInfo *RegInfo,
                                    bool AddIfNotFound) {
   bool isPhysReg = TargetRegisterInfo::isPhysicalRegister(IncomingReg);
+  bool hasAliases = isPhysReg && RegInfo->getAliasSet(IncomingReg) == 0;
   bool Found = false;
   SmallVector<unsigned,4> DeadOps;
   for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
@@ -790,7 +791,7 @@
     if (Reg == IncomingReg) {
       MO.setIsDead();
       Found = true;
-    } else if (isPhysReg && MO.isDead() &&
+    } else if (hasAliases && MO.isDead() &&
         TargetRegisterInfo::isPhysicalRegister(Reg)) {
       // There exists a super-register that's marked dead.
       if (RegInfo->isSuperRegister(IncomingReg, Reg))