Fix bug in optimization in the presence of externalized strings.

runtime/vm/intermediate_language.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/intermediate_language.h"
 
 #include "vm/bit_vector.h"
 #include "vm/dart_entry.h"
 #include "vm/flow_graph_allocator.h"
 #include "vm/flow_graph_builder.h"
@@ skipping 85 matching lines @@
     // TODO(fschneider): Make sure ic_data are sorted to hit more cases.
     if (unary_checks().GetReceiverClassIdAt(i) !=
         other_check->unary_checks().GetReceiverClassIdAt(i)) {
       return false;
     }
   }
   return true;
 }
 
 
+bool CheckClassInstr::AffectedBySideEffect() const {
+  // The class-id of string objects is not invariant: Externalization of strings
+  // via the API can change the class-id.
+  return unary_checks().HasReceiverClassId(kOneByteStringCid)
+      || unary_checks().HasReceiverClassId(kTwoByteStringCid);
+}
+
+
 bool CheckArrayBoundInstr::AttributesEqual(Instruction* other) const {
   CheckArrayBoundInstr* other_check = other->AsCheckArrayBound();
   ASSERT(other_check != NULL);
   return array_type() == other_check->array_type();
 }
 
 
 bool AssertAssignableInstr::AttributesEqual(Instruction* other) const {
   AssertAssignableInstr* other_assert = other->AsAssertAssignable();
   ASSERT(other_assert != NULL);
@@ skipping 2574 matching lines @@
       return ByteArray::length_offset();
     default:
       UNREACHABLE();
       return -1;
   }
 }
 
 #undef __
 
 }  // namespace dart