Fix HConstants with Smi-ranged HeapNumber values

src/hydrogen-instructions.cc

 // Copyright 2012 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 2544 matching lines @@
     has_smi_value_(Smi::IsValid(integer_value)),
     has_int32_value_(true),
     has_double_value_(true),
     has_external_reference_value_(false),
     is_internalized_string_(false),
     is_not_in_new_space_(is_not_in_new_space),
     is_cell_(false),
     boolean_value_(integer_value != 0),
     int32_value_(integer_value),
     double_value_(FastI2D(integer_value)) {
-  set_type(has_smi_value_ ? HType::Smi() : HType::TaggedNumber());
+  // It's possible to create a constant with a value in Smi-range but stored
+  // in a (pre-existing) HeapNumber. See crbug.com/349878.
+  bool could_be_heapobject = r.IsTagged() && !object.handle().is_null();
+  bool is_smi = has_smi_value_ && !could_be_heapobject;
+  set_type(is_smi ? HType::Smi() : HType::TaggedNumber());
   Initialize(r);
 }
 
 
 HConstant::HConstant(double double_value,
                      Representation r,
                      bool is_not_in_new_space,
                      Unique<Object> object)
   : object_(object),
     has_int32_value_(IsInteger32(double_value)),
     has_double_value_(true),
     has_external_reference_value_(false),
     is_internalized_string_(false),
     is_not_in_new_space_(is_not_in_new_space),
     is_cell_(false),
     boolean_value_(double_value != 0 && !std::isnan(double_value)),
     int32_value_(DoubleToInt32(double_value)),
     double_value_(double_value) {
   has_smi_value_ = has_int32_value_ && Smi::IsValid(int32_value_);
-  set_type(has_smi_value_ ? HType::Smi() : HType::TaggedNumber());
+  // It's possible to create a constant with a value in Smi-range but stored
+  // in a (pre-existing) HeapNumber. See crbug.com/349878.
+  bool could_be_heapobject = r.IsTagged() && !object.handle().is_null();
+  bool is_smi = has_smi_value_ && !could_be_heapobject;
+  set_type(is_smi ? HType::Smi() : HType::TaggedNumber());
   Initialize(r);
 }
 
 
 HConstant::HConstant(ExternalReference reference)
   : HTemplateInstruction<0>(HType::None()),
     object_(Unique<Object>(Handle<Object>::null())),
     has_smi_value_(false),
     has_int32_value_(false),
     has_double_value_(false),
@@ skipping 1926 matching lines @@
       break;
     case kExternalMemory:
       stream->Add("[external-memory]");
       break;
   }
 
   stream->Add("@%d", offset());
 }
 
 } }  // namespace v8::internal