Avoid creating duplicate entries for a value when merging HSimulates

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index 90fea07f982faaa0bb8d81a98fafaac4a2a755c1..ecfc859abde54cff0ce801869dfb36130f58dd16 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -1858,6 +1858,12 @@ class HSimulate: public HInstruction {
     // use lists are correctly updated.
     SetOperandAt(values_.length() - 1, value);
   }
+  bool HasValueForIndex(int index) {
+    for (int i = 0; i < assigned_indexes_.length(); ++i) {
+      if (assigned_indexes_[i] == index) return true;
+    }
+    return false;
+  }
   BailoutId ast_id_;
   int pop_count_;
   ZoneList<HValue*> values_;