--- old/src/hotspot/share/c1/c1_Instruction.cpp	2019-02-20 20:12:23.423538106 -0800
+++ new/src/hotspot/share/c1/c1_Instruction.cpp	2019-02-20 20:12:23.203530025 -0800
@@ -147,7 +147,7 @@
   return false;
 }
 
-bool Instruction::maybe_flattened_array() const {
+bool Instruction::maybe_flattened_array() {
   if (ValueArrayFlatten) {
     ciType* type = declared_type();
     if (type != NULL) {
@@ -167,6 +167,10 @@
           return true;
         }
       }
+    } else if (as_Phi() != NULL) {
+      // Type info gets lost during Phi merging, but we might be storing into a
+      // flattened array, so we should do a runtime check.
+      return true;
     }
   }