Avoid undefined behavior from passing a std::vector's own contents

in as an argument to push_back.

llvm-svn: 178166

llvm/utils/TableGen/CodeGenSchedule.cpp

@@ -1105,7 +1105,9 @@ void PredTransitions::getIntersectingVariants(
       // Push another copy of the current transition for more variants.
       Variant.TransVecIdx = TransVec.size();
       IntersectingVariants.push_back(Variant);
-      TransVec.push_back(TransVec[TransIdx]);
+
+      PredTransition Trans = TransVec[TransIdx];
+      TransVec.push_back(Trans);
     }
   }
 }