Introduce FieldIndex to unify and abstract property/field offset

src/code-stubs-hydrogen.cc

Index: src/code-stubs-hydrogen.cc
diff --git a/src/code-stubs-hydrogen.cc b/src/code-stubs-hydrogen.cc
index 9e974138926d711ee4f5033364152d836d3d60a1..88e71faca9ee9dca4db2991d81117fbb8568a147 100644
--- a/src/code-stubs-hydrogen.cc
+++ b/src/code-stubs-hydrogen.cc
@@ -5,6 +5,7 @@
 #include "src/v8.h"
 
 #include "src/code-stubs.h"
+#include "src/field-index.h"
 #include "src/hydrogen.h"
 #include "src/lithium.h"
 
@@ -59,9 +60,7 @@ class CodeStubGraphBuilderBase : public HGraphBuilder {
   Isolate* isolate() { return info_.isolate(); }
 
   HLoadNamedField* BuildLoadNamedField(HValue* object,
-                                       Representation representation,
-                                       int offset,
-                                       bool is_inobject);
+                                       FieldIndex index);
 
   enum ArgumentClass {
     NONE,
@@ -553,14 +552,15 @@ Handle<Code> KeyedLoadFastElementStub::GenerateCode() {
 
 
 HLoadNamedField* CodeStubGraphBuilderBase::BuildLoadNamedField(
-    HValue* object,
-    Representation representation,
-    int offset,
-    bool is_inobject) {
-  HObjectAccess access = is_inobject
+    HValue* object, FieldIndex index) {
+  Representation representation = index.is_double()
+      ? Representation::Double()
+      : Representation::Tagged();
+  int offset = index.offset();
+  HObjectAccess access = index.is_inobject()
       ? HObjectAccess::ForObservableJSObjectOffset(offset, representation)
       : HObjectAccess::ForBackingStoreOffset(offset, representation);
-  if (representation.IsDouble()) {
+  if (index.is_double()) {
     // Load the heap number.
     object = Add<HLoadNamedField>(
         object, static_cast<HValue*>(NULL),
@@ -574,10 +574,7 @@ HLoadNamedField* CodeStubGraphBuilderBase::BuildLoadNamedField(
 
 template<>
 HValue* CodeStubGraphBuilder<LoadFieldStub>::BuildCodeStub() {
-  return BuildLoadNamedField(GetParameter(0),
-                             casted_stub()->representation(),
-                             casted_stub()->offset(),
-                             casted_stub()->is_inobject());
+  return BuildLoadNamedField(GetParameter(0), casted_stub()->index());
 }
 
 
@@ -588,10 +585,10 @@ Handle<Code> LoadFieldStub::GenerateCode() {
 
 template<>
 HValue* CodeStubGraphBuilder<StringLengthStub>::BuildCodeStub() {
-  HValue* string = BuildLoadNamedField(
-      GetParameter(0), Representation::Tagged(), JSValue::kValueOffset, true);
-  return BuildLoadNamedField(
-      string, Representation::Tagged(), String::kLengthOffset, true);
+  HValue* string = BuildLoadNamedField(GetParameter(0),
+      FieldIndex::ForInObjectOffset(JSValue::kValueOffset));
+  return BuildLoadNamedField(string,
+      FieldIndex::ForInObjectOffset(String::kLengthOffset));
 }