Make subtype test cache stub shared between isolates.

runtime/vm/assembler_x64.cc

 // 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.
 
 #include "vm/globals.h"  // NOLINT
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/assembler.h"
 #include "vm/cpu.h"
 #include "vm/heap.h"
@@ skipping 3763 matching lines @@
   ASSERT(RawObject::kClassIdTagSize == kBitsPerInt32);
   ASSERT(sizeof(classid_t) == sizeof(uint32_t));
   const intptr_t class_id_offset = Object::tags_offset() +
       RawObject::kClassIdTagPos / kBitsPerByte;
   movl(result, FieldAddress(object, class_id_offset));
 }
 
 
 void Assembler::LoadClassById(Register result, Register class_id, Register pp) {
   ASSERT(result != class_id);
-  Isolate* isolate = Isolate::Current();
-  LoadImmediate(result, Immediate(isolate->class_table()->TableAddress()), pp);
-  movq(result, Address(result, 0));
+  LoadIsolate(result);
+  const intptr_t offset =
+      Isolate::class_table_offset() + ClassTable::table_offset();
+  movq(result, Address(result, offset));
   movq(result, Address(result, class_id, TIMES_8, 0));
 }
 
 
 void Assembler::LoadClass(Register result, Register object, Register pp) {
   LoadClassId(TMP, object);
   LoadClassById(result, TMP, pp);
 }
 
 
@@ skipping 161 matching lines @@
 
 
 const char* Assembler::FpuRegisterName(FpuRegister reg) {
   ASSERT((0 <= reg) && (reg < kNumberOfXmmRegisters));
   return xmm_reg_names[reg];
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64