Use shorter write-barrier filtering sequence when value is known to be non-smi.

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 "lib/error.h"
@@ skipping 1494 matching lines @@
                        : Location::RegisterOrConstant(value()));
   return summary;
 }
 
 
 void StoreInstanceFieldInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   Register instance_reg = locs()->in(0).reg();
   if (ShouldEmitStoreBarrier()) {
     Register value_reg = locs()->in(1).reg();
     __ StoreIntoObject(instance_reg,
-        FieldAddress(instance_reg, field().Offset()), value_reg);
+                       FieldAddress(instance_reg, field().Offset()),
+                       value_reg,
+                       CanValueBeSmi());
   } else {
     if (locs()->in(1).IsConstant()) {
       __ StoreObject(FieldAddress(instance_reg, field().Offset()),
                      locs()->in(1).constant());
     } else {
       Register value_reg = locs()->in(1).reg();
       __ StoreIntoObjectNoBarrier(instance_reg,
           FieldAddress(instance_reg, field().Offset()), value_reg);
     }
   }
@@ skipping 1801 matching lines @@
                          PcDescriptors::kOther,
                          locs());
   __ Drop(2);  // Discard type arguments and receiver.
 }
 
 }  // namespace dart
 
 #undef __
 
 #endif  // defined TARGET_ARCH_X64