HStoreNamedField for Smis optimized for x64

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index 8dbecac1191d49440fd755860a559cd71b75e2a5..b4be3fbb134832c6750937eedd50c59f873d0b9d 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -5275,6 +5275,8 @@ HInstruction* HOptimizedGraphBuilder::BuildStoreNamedField(
     // TODO(fschneider): Record the new map type of the object in the IR to
     // enable elimination of redundant checks after the transition store.
     instr->SetGVNFlag(kChangesMaps);
+  } else {
+    instr->set_can_omit_smi_tag_store(true);
   }
   return instr;
 }
@@ -9475,7 +9477,7 @@ void HOptimizedGraphBuilder::BuildEmitInObjectProperties(
       Add<HStoreNamedField>(object, access, result);
     } else {
       Representation representation = details.representation();
-      HInstruction* value_instruction = Add<HConstant>(value);
+      HInstruction* value_instruction;
 
       if (representation.IsDouble()) {
         // Allocate a HeapNumber box and store the value into it.
@@ -9490,8 +9492,12 @@ void HOptimizedGraphBuilder::BuildEmitInObjectProperties(
         AddStoreMapConstant(double_box,
             isolate()->factory()->heap_number_map());
         Add<HStoreNamedField>(double_box, HObjectAccess::ForHeapNumberValue(),
-            value_instruction);
+                              Add<HConstant>(value));
         value_instruction = double_box;
+      } else if (representation.IsSmi() && value->IsUninitialized()) {
+        value_instruction = graph()->GetConstant0();
+      } else {
+        value_instruction = Add<HConstant>(value);
       }
 
       Add<HStoreNamedField>(object, access, value_instruction);