Move vm_tags from isolate to thread, since we may have multiple threads in same isolate (GC, backgr…

runtime/vm/assembler_x64.h

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_ASSEMBLER_X64_H_
 #define VM_ASSEMBLER_X64_H_
 
 #ifndef VM_ASSEMBLER_H_
 #error Do not include assembler_x64.h directly; use assembler.h instead.
 #endif
@@ skipping 1014 matching lines @@
                                            intptr_t cid,
                                            intptr_t index_scale,
                                            Register array,
                                            intptr_t index);
   static Address ElementAddressForRegIndex(bool is_external,
                                            intptr_t cid,
                                            intptr_t index_scale,
                                            Register array,
                                            Register index);
 
+  static Address VMTagAddress() {
+    return Address(THR, Thread::vm_tag_offset());
+  }
+
   // On some other platforms, we draw a distinction between safe and unsafe
   // smis.
   static bool IsSafe(const Object& object) { return true; }
   static bool IsSafeSmi(const Object& object) { return object.IsSmi(); }
 
  private:
   AssemblerBuffer buffer_;
 
   ObjectPoolWrapper object_pool_wrapper_;
 
@@ skipping 153 matching lines @@
 }
 
 
 inline void Assembler::EmitOperandSizeOverride() {
   EmitUint8(0x66);
 }
 
 }  // namespace dart
 
 #endif  // VM_ASSEMBLER_X64_H_