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

runtime/vm/intermediate_language_x64.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/globals.h"  // Needed here to get TARGET_ARCH_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/intermediate_language.h"
 
 #include "vm/dart_entry.h"
@@ skipping 224 matching lines @@
       new LocationSummary(kNumInputs, kNumTemps, LocationSummary::kNoCall);
   locs->set_out(0, Location::RequiresFpuRegister());
   return locs;
 }
 
 
 void UnboxedConstantInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   // The register allocator drops constant definitions that have no uses.
   if (!locs()->out(0).IsInvalid()) {
     XmmRegister result = locs()->out(0).fpu_reg();
-    __ LoadObject(TMP, value(), PP);
-    __ movsd(result, FieldAddress(TMP, Double::value_offset()));
+    if (Utils::DoublesBitEqual(Double::Cast(value()).value(), 0.0)) {
+      __ xorps(result, result);
+    } else {
+      __ LoadObject(TMP, value(), PP);
+      __ movsd(result, FieldAddress(TMP, Double::value_offset()));
+    }
   }
 }
 
 
 LocationSummary* AssertAssignableInstr::MakeLocationSummary(bool opt) const {
   const intptr_t kNumInputs = 3;
   const intptr_t kNumTemps = 0;
   LocationSummary* summary =
       new LocationSummary(kNumInputs, kNumTemps, LocationSummary::kCall);
   summary->set_in(0, Location::RegisterLocation(RAX));  // Value.
@@ skipping 5351 matching lines @@
                          PcDescriptors::kOther,
                          locs());
   __ Drop(ArgumentCount());  // Discard arguments.
 }
 
 }  // namespace dart
 
 #undef __
 
 #endif  // defined TARGET_ARCH_X64