*** old/src/jdk.internal.vm.compiler/share/classes/org.graalvm.compiler.core.common/src/org/graalvm/compiler/core/common/type/ArithmeticStamp.java	Mon Mar 20 17:37:11 2017
--- new/src/jdk.internal.vm.compiler/share/classes/org.graalvm.compiler.core.common/src/org/graalvm/compiler/core/common/type/ArithmeticStamp.java	Mon Mar 20 17:37:11 2017

*** 44,55 ****
--- 44,59 ----
  
      public abstract SerializableConstant deserialize(ByteBuffer buffer);
  
      @Override
      public Stamp improveWith(Stamp other) {
+         if (this.isCompatible(other)) {
              return this.join(other);
          }
+         // Cannot improve, because stamps are not compatible.
+         return this;
+     }
  
      @Override
      public int hashCode() {
          final int prime = 31;
          int result = 1;

*** 63,71 ****
--- 67,75 ----
              return true;
          }
          if (!(obj instanceof ArithmeticStamp)) {
              return false;
          }
!         assert Objects.equals(ops, ((ArithmeticStamp) obj).ops) : ops + " vs. " + ((ArithmeticStamp) obj).ops;
          return true;
      }
  }