Ensure constant truncation is only done when it is safe.

src/hydrogen.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 7676 matching lines @@
       return false;
     }
   }
   return true;
 }
 
 
 HValue* HGraphBuilder::TruncateToNumber(HValue* value, Handle<Type>* expected) {
   if (value->IsConstant()) {
     HConstant* constant = HConstant::cast(value);
-    Maybe<HConstant*> number = constant->CopyToTruncatedNumber(zone());
+    Maybe<HConstant*> number =
+        constant->CopyToTruncatedNumberAndAdd(zone(), this);
     if (number.has_value) {
       *expected = handle(Type::Number(), isolate());
-      return AddInstruction(number.value);
+      return number.value;
     }
   }
 
   return value;
 }
 
 
 HInstruction* HOptimizedGraphBuilder::BuildBinaryOperation(
     BinaryOperation* expr,
     HValue* left,
@@ skipping 1993 matching lines @@
   if (ShouldProduceTraceOutput()) {
     isolate()->GetHTracer()->TraceHydrogen(name(), graph_);
   }
 
 #ifdef DEBUG
   graph_->Verify(false);  // No full verify.
 #endif
 }
 
 } }  // namespace v8::internal