Change 64 bit ArtMethod fields to be pointer sized

Changed the 64 bit entrypoint and gc map fields in ArtMethod to be
pointer sized. This saves a large amount of memory on 32 bit systems.
Reduces ArtMethod size by 16 bytes on 32 bit.

Total number of ArtMethod on low memory mako: 169957
Image size: 49203 methods -> 787248 image size reduction.
Zygote space size: 1070 methods -> 17120 size reduction.
App methods: ~120k -> 2 MB savings.

Savings per app on low memory mako: 125K+ per app
(less active apps -> more image methods per app).

Savings depend on how often the shared methods are on dirty pages vs
shared.

TODO in another CL, delete gc map field from ArtMethod since we
should be able to get it from the Oat method header.

Bug: 17643507

Change-Id: Ie9508f05907a9f693882d4d32a564460bf273ee8

(cherry picked from commit e832e64a7e82d7f72aedbd7d798fb929d458ee8f)
diff --git a/runtime/mirror/art_method-inl.h b/runtime/mirror/art_method-inl.h
index 494fa2f..62d17ab 100644
--- a/runtime/mirror/art_method-inl.h
+++ b/runtime/mirror/art_method-inl.h
@@ -307,12 +307,6 @@
   return pc - reinterpret_cast<uintptr_t>(code);
 }
 
-template<VerifyObjectFlags kVerifyFlags>
-inline void ArtMethod::SetNativeMethod(const void* native_method) {
-  SetFieldPtr<false, true, kVerifyFlags>(
-      OFFSET_OF_OBJECT_MEMBER(ArtMethod, entry_point_from_jni_), native_method);
-}
-
 inline QuickMethodFrameInfo ArtMethod::GetQuickFrameInfo(const void* code_pointer) {
   DCHECK(code_pointer != nullptr);
   DCHECK_EQ(code_pointer, GetQuickOatCodePointer());
@@ -485,6 +479,12 @@
   return type;
 }
 
+inline void ArtMethod::CheckObjectSizeEqualsMirrorSize() {
+  // Using the default, check the class object size to make sure it matches the size of the
+  // object.
+  DCHECK_EQ(GetClass()->GetObjectSize(), sizeof(*this));
+}
+
 }  // namespace mirror
 }  // namespace art
 
diff --git a/runtime/mirror/art_method.cc b/runtime/mirror/art_method.cc
index a742aaa..3b4d5f3 100644
--- a/runtime/mirror/art_method.cc
+++ b/runtime/mirror/art_method.cc
@@ -483,7 +483,7 @@
   if (is_fast) {
     SetAccessFlags(GetAccessFlags() | kAccFastNative);
   }
-  SetNativeMethod(native_method);
+  SetEntryPointFromJni(native_method);
 }
 
 void ArtMethod::UnregisterNative() {
diff --git a/runtime/mirror/art_method.h b/runtime/mirror/art_method.h
index d92d00a..4a7831f 100644
--- a/runtime/mirror/art_method.h
+++ b/runtime/mirror/art_method.h
@@ -48,11 +48,6 @@
   // Size of java.lang.reflect.ArtMethod.class.
   static uint32_t ClassSize();
 
-  // Size of an instance of java.lang.reflect.ArtMethod not including its value array.
-  static constexpr uint32_t InstanceSize() {
-    return sizeof(ArtMethod);
-  }
-
   static ArtMethod* FromReflectedMethod(const ScopedObjectAccessAlreadyRunnable& soa,
                                         jobject jlr_method)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
@@ -258,49 +253,92 @@
   template<VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags>
   EntryPointFromInterpreter* GetEntryPointFromInterpreter()
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
-    return GetFieldPtr<EntryPointFromInterpreter*, kVerifyFlags>(
-        OFFSET_OF_OBJECT_MEMBER(ArtMethod, entry_point_from_interpreter_));
+    CheckObjectSizeEqualsMirrorSize();
+    return GetEntryPointFromInterpreterPtrSize(sizeof(void*));
+  }
+  template<VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags>
+  EntryPointFromInterpreter* GetEntryPointFromInterpreterPtrSize(size_t pointer_size)
+      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+    return GetFieldPtrWithSize<EntryPointFromInterpreter*, kVerifyFlags>(
+        EntryPointFromInterpreterOffset(pointer_size), pointer_size);
   }
 
-  template<VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags>
+  template <VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags>
   void SetEntryPointFromInterpreter(EntryPointFromInterpreter* entry_point_from_interpreter)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
-    SetFieldPtr<false, true, kVerifyFlags>(
-        OFFSET_OF_OBJECT_MEMBER(ArtMethod, entry_point_from_interpreter_),
-        entry_point_from_interpreter);
+    CheckObjectSizeEqualsMirrorSize();
+    SetEntryPointFromInterpreterPtrSize(entry_point_from_interpreter, sizeof(void*));
+  }
+  template <VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags>
+  void SetEntryPointFromInterpreterPtrSize(EntryPointFromInterpreter* entry_point_from_interpreter,
+                                           size_t pointer_size)
+      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+    SetFieldPtrWithSize<false, true, kVerifyFlags>(
+        EntryPointFromInterpreterOffset(pointer_size), entry_point_from_interpreter, pointer_size);
   }
 
-  static MemberOffset EntryPointFromPortableCompiledCodeOffset() {
-    return MemberOffset(OFFSETOF_MEMBER(ArtMethod, entry_point_from_portable_compiled_code_));
+  ALWAYS_INLINE static MemberOffset EntryPointFromPortableCompiledCodeOffset(size_t pointer_size) {
+    return MemberOffset(PtrSizedFieldsOffset() + OFFSETOF_MEMBER(
+        PtrSizedFields, entry_point_from_portable_compiled_code_) / sizeof(void*) * pointer_size);
   }
 
-  template<VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags>
-  const void* GetEntryPointFromPortableCompiledCode() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
-    return GetFieldPtr<const void*, kVerifyFlags>(
-        EntryPointFromPortableCompiledCodeOffset());
+  template <VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags>
+  const void* GetEntryPointFromPortableCompiledCode()
+      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+    CheckObjectSizeEqualsMirrorSize();
+    return GetEntryPointFromPortableCompiledCodePtrSize(sizeof(void*));
   }
 
-  template<VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags>
+  template <VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags>
+  ALWAYS_INLINE const void* GetEntryPointFromPortableCompiledCodePtrSize(size_t pointer_size)
+      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+    return GetFieldPtrWithSize<const void*, kVerifyFlags>(
+        EntryPointFromPortableCompiledCodeOffset(pointer_size), pointer_size);
+  }
+
+  template <VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags>
   void SetEntryPointFromPortableCompiledCode(const void* entry_point_from_portable_compiled_code)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
-    SetFieldPtr<false, true, kVerifyFlags>(
-        EntryPointFromPortableCompiledCodeOffset(), entry_point_from_portable_compiled_code);
+    CheckObjectSizeEqualsMirrorSize();
+    return SetEntryPointFromPortableCompiledCodePtrSize(entry_point_from_portable_compiled_code,
+                                                        sizeof(void*));
   }
 
-  static MemberOffset EntryPointFromQuickCompiledCodeOffset() {
-    return MemberOffset(OFFSETOF_MEMBER(ArtMethod, entry_point_from_quick_compiled_code_));
+  template <VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags>
+  void SetEntryPointFromPortableCompiledCodePtrSize(
+      const void* entry_point_from_portable_compiled_code, size_t pointer_size)
+      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+    SetFieldPtrWithSize<false, true, kVerifyFlags>(
+        EntryPointFromPortableCompiledCodeOffset(pointer_size),
+        entry_point_from_portable_compiled_code, pointer_size);
   }
 
-  template<VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags>
+  template <VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags>
   const void* GetEntryPointFromQuickCompiledCode() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
-    return GetFieldPtr<const void*, kVerifyFlags>(EntryPointFromQuickCompiledCodeOffset());
+    CheckObjectSizeEqualsMirrorSize();
+    return GetEntryPointFromQuickCompiledCodePtrSize(sizeof(void*));
+  }
+  template <VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags>
+  ALWAYS_INLINE const void* GetEntryPointFromQuickCompiledCodePtrSize(size_t pointer_size)
+      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+    return GetFieldPtrWithSize<const void*, kVerifyFlags>(
+        EntryPointFromQuickCompiledCodeOffset(pointer_size), pointer_size);
   }
 
-  template<VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags>
+  template <VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags>
   void SetEntryPointFromQuickCompiledCode(const void* entry_point_from_quick_compiled_code)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
-    SetFieldPtr<false, true, kVerifyFlags>(
-        EntryPointFromQuickCompiledCodeOffset(), entry_point_from_quick_compiled_code);
+    CheckObjectSizeEqualsMirrorSize();
+    SetEntryPointFromQuickCompiledCodePtrSize(entry_point_from_quick_compiled_code,
+                                              sizeof(void*));
+  }
+  template <VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags>
+  ALWAYS_INLINE void SetEntryPointFromQuickCompiledCodePtrSize(
+      const void* entry_point_from_quick_compiled_code, size_t pointer_size)
+      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+    SetFieldPtrWithSize<false, true, kVerifyFlags>(
+        EntryPointFromQuickCompiledCodeOffset(pointer_size), entry_point_from_quick_compiled_code,
+        pointer_size);
   }
 
   uint32_t GetCodeSize() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
@@ -365,11 +403,23 @@
   CodeInfo GetOptimizedCodeInfo() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   const uint8_t* GetNativeGcMap() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
-    return GetFieldPtr<uint8_t*>(OFFSET_OF_OBJECT_MEMBER(ArtMethod, gc_map_));
+    CheckObjectSizeEqualsMirrorSize();
+    return GetNativeGcMapPtrSize(sizeof(void*));
   }
-  template<VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags>
+  ALWAYS_INLINE const uint8_t* GetNativeGcMapPtrSize(size_t pointer_size)
+      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+    return GetFieldPtrWithSize<uint8_t*>(GcMapOffset(pointer_size), pointer_size);
+  }
+  template <VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags>
   void SetNativeGcMap(const uint8_t* data) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
-    SetFieldPtr<false, true, kVerifyFlags>(OFFSET_OF_OBJECT_MEMBER(ArtMethod, gc_map_), data);
+    CheckObjectSizeEqualsMirrorSize();
+    SetNativeGcMapPtrSize(data, sizeof(void*));
+  }
+  template <VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags>
+  ALWAYS_INLINE void SetNativeGcMapPtrSize(const uint8_t* data, size_t pointer_size)
+      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+    SetFieldPtrWithSize<false, true, kVerifyFlags>(GcMapOffset(pointer_size), data,
+                                                   pointer_size);
   }
 
   // When building the oat need a convenient place to stuff the offset of the native GC map.
@@ -409,16 +459,46 @@
 
   void UnregisterNative() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
-  static MemberOffset NativeMethodOffset() {
-    return OFFSET_OF_OBJECT_MEMBER(ArtMethod, entry_point_from_jni_);
+  static MemberOffset EntryPointFromInterpreterOffset(size_t pointer_size) {
+    return MemberOffset(PtrSizedFieldsOffset() + OFFSETOF_MEMBER(
+        PtrSizedFields, entry_point_from_interpreter_) / sizeof(void*) * pointer_size);
   }
 
-  const void* GetNativeMethod() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
-    return GetFieldPtr<const void*>(NativeMethodOffset());
+  static MemberOffset EntryPointFromJniOffset(size_t pointer_size) {
+    return MemberOffset(PtrSizedFieldsOffset() + OFFSETOF_MEMBER(
+        PtrSizedFields, entry_point_from_jni_) / sizeof(void*) * pointer_size);
   }
 
-  template<VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags>
-  void SetNativeMethod(const void*) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  static MemberOffset EntryPointFromQuickCompiledCodeOffset(size_t pointer_size) {
+    return MemberOffset(PtrSizedFieldsOffset() + OFFSETOF_MEMBER(
+        PtrSizedFields, entry_point_from_quick_compiled_code_) / sizeof(void*) * pointer_size);
+  }
+
+  static MemberOffset GcMapOffset(size_t pointer_size) {
+    return MemberOffset(PtrSizedFieldsOffset() + OFFSETOF_MEMBER(
+        PtrSizedFields, gc_map_) / sizeof(void*) * pointer_size);
+  }
+
+  void* GetEntryPointFromJni() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+    CheckObjectSizeEqualsMirrorSize();
+    return GetEntryPointFromJniPtrSize(sizeof(void*));
+  }
+  ALWAYS_INLINE void* GetEntryPointFromJniPtrSize(size_t pointer_size)
+      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+    return GetFieldPtrWithSize<void*>(EntryPointFromJniOffset(pointer_size), pointer_size);
+  }
+
+  template <VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags>
+  void SetEntryPointFromJni(const void* entrypoint) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+    CheckObjectSizeEqualsMirrorSize();
+    SetEntryPointFromJniPtrSize<kVerifyFlags>(entrypoint, sizeof(void*));
+  }
+  template <VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags>
+  ALWAYS_INLINE void SetEntryPointFromJniPtrSize(const void* entrypoint, size_t pointer_size)
+      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+    SetFieldPtrWithSize<false, true, kVerifyFlags>(
+        EntryPointFromJniOffset(pointer_size), entrypoint, pointer_size);
+  }
 
   static MemberOffset GetMethodIndexOffset() {
     return OFFSET_OF_OBJECT_MEMBER(ArtMethod, method_index_);
@@ -521,7 +601,16 @@
 
   ALWAYS_INLINE ArtMethod* GetInterfaceMethodIfProxy() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
- private:
+  static size_t SizeWithoutPointerFields() {
+    return sizeof(ArtMethod) - sizeof(PtrSizedFields);
+  }
+
+  // Size of an instance of java.lang.reflect.ArtMethod not including its value array.
+  static size_t InstanceSize(size_t pointer_size) {
+    return SizeWithoutPointerFields() + (sizeof(PtrSizedFields) / sizeof(void*)) * pointer_size;
+  }
+
+ protected:
   // Field order required by test "ValidateFieldOrderOfJavaCppUnionClasses".
   // The class we are a part of.
   HeapReference<Class> declaring_class_;
@@ -535,26 +624,6 @@
   // Short cuts to declaring_class_->dex_cache_ member for fast compiled code access.
   HeapReference<ObjectArray<String>> dex_cache_strings_;
 
-  // Method dispatch from the interpreter invokes this pointer which may cause a bridge into
-  // compiled code.
-  uint64_t entry_point_from_interpreter_;
-
-  // Pointer to JNI function registered to this method, or a function to resolve the JNI function.
-  uint64_t entry_point_from_jni_;
-
-  // Method dispatch from portable compiled code invokes this pointer which may cause bridging into
-  // quick compiled code or the interpreter.
-  uint64_t entry_point_from_portable_compiled_code_;
-
-  // Method dispatch from quick compiled code invokes this pointer which may cause bridging into
-  // portable compiled code or the interpreter.
-  uint64_t entry_point_from_quick_compiled_code_;
-
-  // Pointer to a data structure created by the compiler and used by the garbage collector to
-  // determine which registers hold live references to objects within the heap. Keyed by native PC
-  // offsets for the quick compiler and dex PCs for the portable.
-  uint64_t gc_map_;
-
   // Access flags; low 16 bits are defined by spec.
   uint32_t access_flags_;
 
@@ -573,15 +642,46 @@
   // ifTable.
   uint32_t method_index_;
 
+  // Add alignment word here if necessary.
+
+  // Must be the last fields in the method.
+  struct PACKED(4) PtrSizedFields {
+    // Method dispatch from the interpreter invokes this pointer which may cause a bridge into
+    // compiled code.
+    void* entry_point_from_interpreter_;
+
+    // Pointer to JNI function registered to this method, or a function to resolve the JNI function.
+    void* entry_point_from_jni_;
+
+    // Method dispatch from quick compiled code invokes this pointer which may cause bridging into
+    // portable compiled code or the interpreter.
+    void* entry_point_from_quick_compiled_code_;
+
+    // Pointer to a data structure created by the compiler and used by the garbage collector to
+    // determine which registers hold live references to objects within the heap. Keyed by native PC
+    // offsets for the quick compiler and dex PCs for the portable.
+    void* gc_map_;
+
+    // Method dispatch from portable compiled code invokes this pointer which may cause bridging
+    // into quick compiled code or the interpreter. Last to simplify entrypoint logic.
+    void* entry_point_from_portable_compiled_code_;
+  } ptr_sized_fields_;
+
   static GcRoot<Class> java_lang_reflect_ArtMethod_;
 
  private:
+  ALWAYS_INLINE void CheckObjectSizeEqualsMirrorSize() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+
   ALWAYS_INLINE ObjectArray<ArtMethod>* GetDexCacheResolvedMethods()
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   ALWAYS_INLINE ObjectArray<Class>* GetDexCacheResolvedTypes()
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
+  static size_t PtrSizedFieldsOffset() {
+    return OFFSETOF_MEMBER(ArtMethod, ptr_sized_fields_);
+  }
+
   friend struct art::ArtMethodOffsets;  // for verifying offset information
   DISALLOW_IMPLICIT_CONSTRUCTORS(ArtMethod);
 };
diff --git a/runtime/mirror/class.h b/runtime/mirror/class.h
index f45ea85..82425b5 100644
--- a/runtime/mirror/class.h
+++ b/runtime/mirror/class.h
@@ -528,6 +528,13 @@
     return SetField32<false>(OFFSET_OF_OBJECT_MEMBER(Class, object_size_), new_object_size);
   }
 
+  void SetObjectSizeWithoutChecks(uint32_t new_object_size)
+      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+    // Not called within a transaction.
+    return SetField32<false, false, kVerifyNone>(
+        OFFSET_OF_OBJECT_MEMBER(Class, object_size_), new_object_size);
+  }
+
   // Returns true if this class is in the same packages as that class.
   bool IsInSamePackage(Class* that) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
diff --git a/runtime/mirror/object-inl.h b/runtime/mirror/object-inl.h
index 4199eef..121947d 100644
--- a/runtime/mirror/object-inl.h
+++ b/runtime/mirror/object-inl.h
@@ -404,8 +404,7 @@
   }
   DCHECK_GE(result, sizeof(Object))
       << " class=" << PrettyTypeOf(GetClass<kNewFlags, kReadBarrierOption>());
-  DCHECK(!(IsArtField<kNewFlags, kReadBarrierOption>())  || result == sizeof(ArtField));
-  DCHECK(!(IsArtMethod<kNewFlags, kReadBarrierOption>()) || result == sizeof(ArtMethod));
+  DCHECK(!(IsArtField<kNewFlags, kReadBarrierOption>()) || result == sizeof(ArtField));
   return result;
 }
 
@@ -962,7 +961,6 @@
     }
   }
 }
-
 }  // namespace mirror
 }  // namespace art
 
diff --git a/runtime/mirror/object.h b/runtime/mirror/object.h
index 0ce5231..221feca 100644
--- a/runtime/mirror/object.h
+++ b/runtime/mirror/object.h
@@ -392,15 +392,26 @@
       VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags, typename T>
   void SetFieldPtr(MemberOffset field_offset, T new_value)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
-#ifndef __LP64__
-    SetField32<kTransactionActive, kCheckTransaction, kVerifyFlags>(
-        field_offset, reinterpret_cast<int32_t>(new_value));
-#else
-    SetField64<kTransactionActive, kCheckTransaction, kVerifyFlags>(
-        field_offset, reinterpret_cast<int64_t>(new_value));
-#endif
+    SetFieldPtrWithSize<kTransactionActive, kCheckTransaction, kVerifyFlags>(
+        field_offset, new_value, sizeof(void*));
   }
 
+  template<bool kTransactionActive, bool kCheckTransaction = true,
+      VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags, typename T>
+  ALWAYS_INLINE void SetFieldPtrWithSize(MemberOffset field_offset, T new_value,
+                                         size_t pointer_size)
+      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+    DCHECK(pointer_size == 4 || pointer_size == 8) << pointer_size;
+    if (pointer_size == 4) {
+      intptr_t ptr  = reinterpret_cast<intptr_t>(new_value);
+      DCHECK_EQ(static_cast<int32_t>(ptr), ptr);  // Check that we dont lose any non 0 bits.
+      SetField32<kTransactionActive, kCheckTransaction, kVerifyFlags>(
+          field_offset, static_cast<int32_t>(ptr));
+    } else {
+      SetField64<kTransactionActive, kCheckTransaction, kVerifyFlags>(
+          field_offset, static_cast<int64_t>(reinterpret_cast<intptr_t>(new_value)));
+    }
+  }
   // TODO fix thread safety analysis broken by the use of template. This should be
   // SHARED_LOCKS_REQUIRED(Locks::mutator_lock_).
   template <const bool kVisitClass, VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags,
@@ -413,11 +424,21 @@
   template<class T, VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags, bool kIsVolatile = false>
   T GetFieldPtr(MemberOffset field_offset)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
-#ifndef __LP64__
-    return reinterpret_cast<T>(GetField32<kVerifyFlags, kIsVolatile>(field_offset));
-#else
-    return reinterpret_cast<T>(GetField64<kVerifyFlags, kIsVolatile>(field_offset));
-#endif
+    return GetFieldPtrWithSize<T, kVerifyFlags, kIsVolatile>(field_offset, sizeof(void*));
+  }
+
+  template<class T, VerifyObjectFlags kVerifyFlags = kDefaultVerifyFlags, bool kIsVolatile = false>
+  ALWAYS_INLINE T GetFieldPtrWithSize(MemberOffset field_offset, size_t pointer_size)
+      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+    DCHECK(pointer_size == 4 || pointer_size == 8) << pointer_size;
+    if (pointer_size == 4) {
+      return reinterpret_cast<T>(GetField32<kVerifyFlags, kIsVolatile>(field_offset));
+    } else {
+      int64_t v = GetField64<kVerifyFlags, kIsVolatile>(field_offset);
+      // Check that we dont lose any non 0 bits.
+      DCHECK_EQ(reinterpret_cast<int64_t>(reinterpret_cast<T>(v)), v);
+      return reinterpret_cast<T>(v);
+    }
   }
 
   // TODO: Fixme when anotatalysis works with visitors.
diff --git a/runtime/mirror/object_test.cc b/runtime/mirror/object_test.cc
index a0aaa9e..4402031 100644
--- a/runtime/mirror/object_test.cc
+++ b/runtime/mirror/object_test.cc
@@ -78,6 +78,14 @@
 TEST_F(ObjectTest, Constants) {
   EXPECT_EQ(kObjectReferenceSize, sizeof(HeapReference<Object>));
   EXPECT_EQ(kObjectHeaderSize, sizeof(Object));
+  EXPECT_EQ(MIRROR_ART_METHOD_PORTABLE_CODE_OFFSET_32,
+            ArtMethod::EntryPointFromPortableCompiledCodeOffset(4).Int32Value());
+  EXPECT_EQ(MIRROR_ART_METHOD_PORTABLE_CODE_OFFSET_64,
+            ArtMethod::EntryPointFromPortableCompiledCodeOffset(8).Int32Value());
+  EXPECT_EQ(MIRROR_ART_METHOD_QUICK_CODE_OFFSET_32,
+            ArtMethod::EntryPointFromQuickCompiledCodeOffset(4).Int32Value());
+  EXPECT_EQ(MIRROR_ART_METHOD_QUICK_CODE_OFFSET_64,
+            ArtMethod::EntryPointFromQuickCompiledCodeOffset(8).Int32Value());
 }
 
 TEST_F(ObjectTest, IsInSamePackage) {