Cache some global constants in Thread, to allow access via THR register.

runtime/vm/thread.h

Index: runtime/vm/thread.h
diff --git a/runtime/vm/thread.h b/runtime/vm/thread.h
index 3a8dacda14fe84f0f24d16c59ae1dde5a3da9f3d..e3494d5a12fddd638844bb80acc23d3204e01339 100644
--- a/runtime/vm/thread.h
+++ b/runtime/vm/thread.h
@@ -14,6 +14,9 @@ namespace dart {
 
 class CHA;
 class Isolate;
+class RawBool;
+class RawObject;
+
 
 // A VM thread; may be executing Dart code or performing helper tasks like
 // garbage collection or compilation. The Thread structure associated with
@@ -53,7 +56,8 @@ class Thread {
 #endif
 
   // Called at VM startup.
-  static void InitOnce();
+  static void InitOnceBeforeIsolate();
+  static void InitOnceAfterObjectAndStubCode();
 
   // The topmost zone used for allocation in this thread.
   Zone* zone() {
@@ -83,14 +87,35 @@ class Thread {
     return OFFSET_OF(Thread, store_buffer_block_);
   }
 
+  static intptr_t object_null_offset() {
+    return OFFSET_OF(Thread, object_null_);
+  }
+
+  static intptr_t bool_true_offset() {
+    return OFFSET_OF(Thread, bool_true_);
+  }
+
+  static intptr_t bool_false_offset() {
+    return OFFSET_OF(Thread, bool_false_);
+  }
+
+  static intptr_t update_store_buffer_entry_point_offset() {
+    return OFFSET_OF(Thread, update_store_buffer_entry_point_);
+  }
+
  private:
   static ThreadLocalKey thread_key_;
 
   Isolate* isolate_;
   StoreBufferBlock* store_buffer_block_;
+  RawObject* object_null_;
+  RawBool* bool_true_;
+  RawBool* bool_false_;
+  uword update_store_buffer_entry_point_;
+
+  explicit Thread(bool init_vm_constants = true);
 
-  Thread()
-      : isolate_(NULL), store_buffer_block_(NULL) {}
+  void InitVMConstants();
 
   static void SetCurrent(Thread* current);