Use VM type cast and save handles.

runtime/vm/benchmark_test.cc

 // Copyright (c) 2012, 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/benchmark_test.h"
 
 #include "bin/file.h"
 
 #include "platform/assert.h"
 
@@ skipping 251 matching lines @@
   const int kNumIterations = 100;
   Dart_EnterScope();
   Code& code = Code::Handle();
   Timer timer(true, "LookupDartCode benchmark");
   timer.Start();
   for (int i = 0; i < kNumIterations; i++) {
     StackFrameIterator frames(StackFrameIterator::kDontValidateFrames);
     StackFrame* frame = frames.NextFrame();
     while (frame != NULL) {
       if (frame->IsStubFrame()) {
-        code ^= frame->LookupDartCode();
+        code = frame->LookupDartCode();
         EXPECT(code.function() == Function::null());
       } else if (frame->IsDartFrame()) {
-        code ^= frame->LookupDartCode();
+        code = frame->LookupDartCode();
         EXPECT(code.function() != Function::null());
       }
       frame = frames.NextFrame();
     }
   }
   timer.Stop();
   int64_t elapsed_time = timer.TotalElapsedTime();
   Dart_SetReturnValue(args, Dart_NewInteger(elapsed_time));
   Dart_ExitScope();
 }
@@ skipping 50 matching lines @@
       reinterpret_cast<Dart_NativeEntryResolver>(StackFrameNativeResolver));
   Dart_Handle cls = Dart_GetClass(lib, Dart_NewString("StackFrameTest"));
   Dart_Handle result = Dart_Invoke(cls, Dart_NewString("testMain"), 0, NULL);
   EXPECT_VALID(result);
   int64_t elapsed_time = 0;
   EXPECT(!Dart_IsError(Dart_IntegerToInt64(result, &elapsed_time)));
   benchmark->set_score(elapsed_time);
 }
 
 }  // namespace dart