diff --git a/src/globals.h b/src/globals.h
index fbc749d..c218f80 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -93,6 +93,18 @@
 #error Target architecture mips is only supported on mips and ia32 host
 #endif
 
+// Determine whether we are running in a simulated environment.
+// Setting USE_SIMULATOR explicitly from the build script will force
+// the use of a simulated environment.
+#if !defined(USE_SIMULATOR)
+#if (defined(V8_TARGET_ARCH_ARM) && !defined(V8_HOST_ARCH_ARM))
+#define USE_SIMULATOR 1
+#endif
+#if (defined(V8_TARGET_ARCH_MIPS) && !defined(V8_HOST_ARCH_MIPS))
+#define USE_SIMULATOR 1
+#endif
+#endif
+
 // Define unaligned read for the target architectures supporting it.
 #if defined(V8_TARGET_ARCH_X64) || defined(V8_TARGET_ARCH_IA32)
 #define V8_TARGET_CAN_READ_UNALIGNED 1
@@ -189,9 +201,11 @@
 #if V8_HOST_ARCH_64_BIT
 const int kPointerSizeLog2 = 3;
 const intptr_t kIntptrSignBit = V8_INT64_C(0x8000000000000000);
+const uintptr_t kUintptrAllBitsSet = V8_UINT64_C(0xFFFFFFFFFFFFFFFF);
 #else
 const int kPointerSizeLog2 = 2;
 const intptr_t kIntptrSignBit = 0x80000000;
+const uintptr_t kUintptrAllBitsSet = 0xFFFFFFFFu;
 #endif
 
 // Mask for the sign bit in a smi.
@@ -324,6 +338,7 @@
 class NewSpace;
 class NodeVisitor;
 class Object;
+class MaybeObject;
 class OldSpace;
 class Property;
 class Proxy;
@@ -542,8 +557,8 @@
 
 // AccessorCallback
 struct AccessorDescriptor {
-  Object* (*getter)(Object* object, void* data);
-  Object* (*setter)(JSObject* object, Object* value, void* data);
+  MaybeObject* (*getter)(Object* object, void* data);
+  MaybeObject* (*setter)(JSObject* object, Object* value, void* data);
   void* data;
 };