Index: llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -2916,7 +2916,8 @@
     ISD::VSELECT : ISD::SELECT;
 
   // Min/max matching is only viable if all output VTs are the same.
-  if (std::equal(ValueVTs.begin(), ValueVTs.end(), ValueVTs.begin())) {
+  if (ValueVTs.size() == 1 ||
+      std::equal(ValueVTs.begin() + 1, ValueVTs.end(), ValueVTs.begin())) {
     EVT VT = ValueVTs[0];
     LLVMContext &Ctx = *DAG.getContext();
     auto &TLI = DAG.getTargetLoweringInfo();
Index: llvm/lib/Transforms/Scalar/NewGVN.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/NewGVN.cpp
+++ llvm/lib/Transforms/Scalar/NewGVN.cpp
@@ -3176,8 +3176,8 @@
             std::back_inserter(OperandList));
   bool Okay = OperandList.size() == 1;
   if (!Okay)
-    Okay =
-        std::equal(OperandList.begin(), OperandList.end(), OperandList.begin());
+    Okay = std::equal(OperandList.begin() + 1, OperandList.end(),
+                      OperandList.begin());
   if (Okay)
     return singleReachablePHIPath(Visited, cast<MemoryAccess>(OperandList[0]),
                                   Second);
@@ -3272,8 +3272,9 @@
                        const MemoryDef *MD = cast<MemoryDef>(U);
                        return ValueToClass.lookup(MD->getMemoryInst());
                      });
-      assert(std::equal(PhiOpClasses.begin(), PhiOpClasses.end(),
-                        PhiOpClasses.begin()) &&
+      assert((PhiOpClasses.size() == 1 ||
+              std::equal(PhiOpClasses.begin() + 1, PhiOpClasses.end(),
+                         PhiOpClasses.begin())) &&
              "All MemoryPhi arguments should be in the same class");
     }
   }