Move ArtField to native

Add linear alloc. Moved ArtField to be native object. Changed image
writer to put ArtFields after the mirror section.

Savings:
2MB on low ram devices
4MB on normal devices

Total PSS measurements before (normal N5, 95s after shell start):
Image size: 7729152 bytes
23112 kB: .NonMoving
23212 kB: .NonMoving
22868 kB: .NonMoving
23072 kB: .NonMoving
22836 kB: .NonMoving
19618 kB: .Zygote
19850 kB: .Zygote
19623 kB: .Zygote
19924 kB: .Zygote
19612 kB: .Zygote
Avg: 42745.4 kB

After:
Image size: 7462912 bytes
17440 kB: .NonMoving
16776 kB: .NonMoving
16804 kB: .NonMoving
17812 kB: .NonMoving
16820 kB: .NonMoving
18788 kB: .Zygote
18856 kB: .Zygote
19064 kB: .Zygote
18841 kB: .Zygote
18629 kB: .Zygote
3499 kB: .LinearAlloc
3408 kB: .LinearAlloc
3424 kB: .LinearAlloc
3600 kB: .LinearAlloc
3436 kB: .LinearAlloc
Avg: 39439.4 kB

No reflection performance changes.

Bug: 19264997
Bug: 17643507

Change-Id: I10c73a37913332080aeb978c7c94713bdfe4fe1c

3 files changed, 15 insertions, 21 deletions

diff --git a/runtime/gc/accounting/mod_union_table.cc b/runtime/gc/accounting/mod_union_table.cc
index a3fac58e8a..cd3f910d95 100644
--- a/runtime/gc/accounting/mod_union_table.cc
+++ b/runtime/gc/accounting/mod_union_table.cc
@@ -28,7 +28,6 @@
 #include "gc/heap.h"
 #include "gc/space/space.h"
 #include "gc/space/image_space.h"
-#include "mirror/art_field-inl.h"
 #include "mirror/object-inl.h"
 #include "mirror/class-inl.h"
 #include "mirror/object_array-inl.h"
diff --git a/runtime/gc/accounting/remembered_set.cc b/runtime/gc/accounting/remembered_set.cc
index b16a146ea9..eeb385e957 100644
--- a/runtime/gc/accounting/remembered_set.cc
+++ b/runtime/gc/accounting/remembered_set.cc
@@ -26,7 +26,6 @@
 #include "gc/collector/semi_space.h"
 #include "gc/heap.h"
 #include "gc/space/space.h"
-#include "mirror/art_field-inl.h"
 #include "mirror/object-inl.h"
 #include "mirror/class-inl.h"
 #include "mirror/object_array-inl.h"
diff --git a/runtime/gc/accounting/space_bitmap.cc b/runtime/gc/accounting/space_bitmap.cc
index ad8d9884ec..2da83250d3 100644
--- a/runtime/gc/accounting/space_bitmap.cc
+++ b/runtime/gc/accounting/space_bitmap.cc
@@ -16,12 +16,12 @@
 
 #include "space_bitmap-inl.h"
 
+#include "art_field-inl.h"
 #include "base/stringprintf.h"
 #include "dex_file-inl.h"
 #include "mem_map.h"
 #include "mirror/object-inl.h"
 #include "mirror/class.h"
-#include "mirror/art_field.h"
 #include "mirror/object_array.h"
 
 namespace art {
@@ -190,15 +190,13 @@ void SpaceBitmap<kAlignment>::WalkInstanceFields(SpaceBitmap<kAlignment>* visite
     WalkInstanceFields(visited, callback, obj, super, arg);
   }
   // Walk instance fields
-  mirror::ObjectArray<mirror::ArtField>* fields = klass->GetIFields();
-  if (fields != NULL) {
-    for (int32_t i = 0; i < fields->GetLength(); i++) {
-      mirror::ArtField* field = fields->Get(i);
-      if (!field->IsPrimitiveType()) {
-        mirror::Object* value = field->GetObj(obj);
-        if (value != NULL) {
-          WalkFieldsInOrder(visited, callback, value, arg);
-        }
+  auto* fields = klass->GetIFields();
+  for (size_t i = 0, count = klass->NumInstanceFields(); i < count; ++i) {
+    ArtField* field = &fields[i];
+    if (!field->IsPrimitiveType()) {
+      mirror::Object* value = field->GetObj(obj);
+      if (value != nullptr) {
+        WalkFieldsInOrder(visited, callback, value, arg);
       }
     }
   }
@@ -219,15 +217,13 @@ void SpaceBitmap<kAlignment>::WalkFieldsInOrder(SpaceBitmap<kAlignment>* visited
   WalkInstanceFields(visited, callback, obj, klass, arg);
   // Walk static fields of a Class
   if (obj->IsClass()) {
-    mirror::ObjectArray<mirror::ArtField>* fields = klass->GetSFields();
-    if (fields != NULL) {
-      for (int32_t i = 0; i < fields->GetLength(); i++) {
-        mirror::ArtField* field = fields->Get(i);
-        if (!field->IsPrimitiveType()) {
-          mirror::Object* value = field->GetObj(NULL);
-          if (value != NULL) {
-            WalkFieldsInOrder(visited, callback, value, arg);
-          }
+    auto* sfields = klass->GetSFields();
+    for (size_t i = 0, count = klass->NumStaticFields(); i < count; ++i) {
+      ArtField* field = &sfields[i];
+      if (!field->IsPrimitiveType()) {
+        mirror::Object* value = field->GetObj(nullptr);
+        if (value != nullptr) {
+          WalkFieldsInOrder(visited, callback, value, arg);
         }
       }
     }