Use (more) xor on FP register to load it with 0.0.

runtime/vm/flow_graph_compiler_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/flow_graph_compiler.h"
 
 #include "vm/ast_printer.h"
@@ skipping 1561 matching lines @@
   } else {
     ASSERT(source.IsConstant());
     const Object& constant = source.constant();
     if (destination.IsRegister()) {
       if (constant.IsSmi() && (Smi::Cast(constant).Value() == 0)) {
         __ xorq(destination.reg(), destination.reg());
       } else {
         __ LoadObject(destination.reg(), constant, PP);
       }
     } else if (destination.IsFpuRegister()) {
-      __ LoadObject(TMP, constant, PP);
-      __ movsd(destination.fpu_reg(),
-          FieldAddress(TMP, Double::value_offset()));
+      if (Utils::DoublesBitEqual(Double::Cast(constant).value(), 0.0)) {
+        __ xorps(destination.fpu_reg(), destination.fpu_reg());
+      } else {
+        __ LoadObject(TMP, constant, PP);
+        __ movsd(destination.fpu_reg(),
+            FieldAddress(TMP, Double::value_offset()));
+      }
     } else if (destination.IsDoubleStackSlot()) {
-      __ LoadObject(TMP, constant, PP);
-      __ movsd(XMM0, FieldAddress(TMP, Double::value_offset()));
+      if (Utils::DoublesBitEqual(Double::Cast(constant).value(), 0.0)) {
+        __ xorps(XMM0, XMM0);
+      } else {
+        __ LoadObject(TMP, constant, PP);
+        __ movsd(XMM0, FieldAddress(TMP, Double::value_offset()));
+      }
       __ movsd(destination.ToStackSlotAddress(), XMM0);
     } else {
       ASSERT(destination.IsStackSlot());
       StoreObject(destination.ToStackSlotAddress(), constant);
     }
   }
 
   move->Eliminate();
 }
 
@@ skipping 128 matching lines @@
   __ movups(reg, Address(RSP, 0));
   __ AddImmediate(RSP, Immediate(kFpuRegisterSize), PP);
 }
 
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64