Use xorps xmm1, xmm1 to creat a 0.0 cconstant. Add to utils a bitwise double test.

runtime/vm/utils_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 "platform/assert.h"
 #include "platform/utils.h"
 #include "vm/unit_test.h"
 
 namespace dart {
 
@@ skipping 201 matching lines @@
   EXPECT_EQ(0xf4, reinterpret_cast<uint8_t*>(&value64le)[0]);
   EXPECT_EQ(0xf3, reinterpret_cast<uint8_t*>(&value64le)[1]);
   EXPECT_EQ(0xf2, reinterpret_cast<uint8_t*>(&value64le)[2]);
   EXPECT_EQ(0xf1, reinterpret_cast<uint8_t*>(&value64le)[3]);
   EXPECT_EQ(0x0, reinterpret_cast<uint8_t*>(&value64le)[4]);
   EXPECT_EQ(0x0, reinterpret_cast<uint8_t*>(&value64le)[5]);
   EXPECT_EQ(0x0, reinterpret_cast<uint8_t*>(&value64le)[6]);
   EXPECT_EQ(0x0, reinterpret_cast<uint8_t*>(&value64le)[7]);
 }
 
+
+UNIT_TEST_CASE(DoublesBitEqual) {
+  EXPECT(Utils::DoublesBitEqual(1.0, 1.0));
+  EXPECT(!Utils::DoublesBitEqual(1.0, -1.0));
+  EXPECT(Utils::DoublesBitEqual(0.0, 0.0));
+  EXPECT(!Utils::DoublesBitEqual(0.0, -0.0));
+  EXPECT(Utils::DoublesBitEqual(NAN, NAN));
+}
+
 }  // namespace dart