Introduce FieldIndex to unify and abstract property/field offset

src/x64/stub-cache-x64.cc

Index: src/x64/stub-cache-x64.cc
diff --git a/src/x64/stub-cache-x64.cc b/src/x64/stub-cache-x64.cc
index c8be271cf969f2818214eabf041f0263bd99b6b2..b0aa310b7419d90d5aaaa5fba1c7182b9c7c97c2 100644
--- a/src/x64/stub-cache-x64.cc
+++ b/src/x64/stub-cache-x64.cc
@@ -618,12 +618,7 @@ void StoreStubCompiler::GenerateStoreField(MacroAssembler* masm,
   // checks.
   ASSERT(object->IsJSGlobalProxy() || !object->IsAccessCheckNeeded());
 
-  int index = lookup->GetFieldIndex().field_index();
-
-  // Adjust for the number of properties stored in the object. Even in the
-  // face of a transition we can use the old map here because the size of the
-  // object and the number of in-object properties is not going to change.
-  index -= object->map()->inobject_properties();
+  FieldIndex index = lookup->GetFieldIndex();
 
   Representation representation = lookup->representation();
   ASSERT(!representation.IsNone());
@@ -648,14 +643,12 @@ void StoreStubCompiler::GenerateStoreField(MacroAssembler* masm,
     }
   } else if (representation.IsDouble()) {
     // Load the double storage.
-    if (index < 0) {
-      int offset = object->map()->instance_size() + (index * kPointerSize);
-      __ movp(scratch1, FieldOperand(receiver_reg, offset));
+    if (index.is_inobject()) {
+      __ movp(scratch1, FieldOperand(receiver_reg, index.offset()));
     } else {
       __ movp(scratch1,
               FieldOperand(receiver_reg, JSObject::kPropertiesOffset));
-      int offset = index * kPointerSize + FixedArray::kHeaderSize;
-      __ movp(scratch1, FieldOperand(scratch1, offset));
+      __ movp(scratch1, FieldOperand(scratch1, index.offset()));
     }
 
     // Store the value into the storage.
@@ -680,32 +673,30 @@ void StoreStubCompiler::GenerateStoreField(MacroAssembler* masm,
   // TODO(verwaest): Share this code as a code stub.
   SmiCheck smi_check = representation.IsTagged()
       ? INLINE_SMI_CHECK : OMIT_SMI_CHECK;
-  if (index < 0) {
+  if (index.is_inobject()) {
     // Set the property straight into the object.
-    int offset = object->map()->instance_size() + (index * kPointerSize);
-    __ movp(FieldOperand(receiver_reg, offset), value_reg);
+    __ movp(FieldOperand(receiver_reg, index.offset()), value_reg);
 
     if (!representation.IsSmi()) {
       // Update the write barrier for the array address.
       // Pass the value being stored in the now unused name_reg.
       __ movp(name_reg, value_reg);
       __ RecordWriteField(
-          receiver_reg, offset, name_reg, scratch1, kDontSaveFPRegs,
+          receiver_reg, index.offset(), name_reg, scratch1, kDontSaveFPRegs,
           EMIT_REMEMBERED_SET, smi_check);
     }
   } else {
     // Write to the properties array.
-    int offset = index * kPointerSize + FixedArray::kHeaderSize;
     // Get the properties array (optimistically).
     __ movp(scratch1, FieldOperand(receiver_reg, JSObject::kPropertiesOffset));
-    __ movp(FieldOperand(scratch1, offset), value_reg);
+    __ movp(FieldOperand(scratch1, index.offset()), value_reg);
 
     if (!representation.IsSmi()) {
       // Update the write barrier for the array address.
       // Pass the value being stored in the now unused name_reg.
       __ movp(name_reg, value_reg);
       __ RecordWriteField(
-          scratch1, offset, name_reg, receiver_reg, kDontSaveFPRegs,
+          scratch1, index.offset(), name_reg, receiver_reg, kDontSaveFPRegs,
           EMIT_REMEMBERED_SET, smi_check);
     }
   }
@@ -913,20 +904,14 @@ Register LoadStubCompiler::CallbackHandlerFrontend(
 
 void LoadStubCompiler::GenerateLoadField(Register reg,
                                          Handle<JSObject> holder,
-                                         PropertyIndex field,
+                                         FieldIndex field,
                                          Representation representation) {
   if (!reg.is(receiver())) __ movp(receiver(), reg);
   if (kind() == Code::LOAD_IC) {
-    LoadFieldStub stub(isolate(),
-                       field.is_inobject(holder),
-                       field.translate(holder),
-                       representation);
+    LoadFieldStub stub(isolate(), field);
     GenerateTailCall(masm(), stub.GetCode());
   } else {
-    KeyedLoadFieldStub stub(isolate(),
-                            field.is_inobject(holder),
-                            field.translate(holder),
-                            representation);
+    KeyedLoadFieldStub stub(isolate(), field);
     GenerateTailCall(masm(), stub.GetCode());
   }
 }