Add LoadTaggedClassIdMayBeSmi to assembly and improve performance of inline cache stubs.

runtime/vm/assembler_arm64.h

 // Copyright (c) 2014, 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_ARM64_H_
 #define VM_ASSEMBLER_ARM64_H_
 
 #ifndef VM_ASSEMBLER_H_
 #error Do not include assembler_arm64.h directly; use assembler.h instead.
 #endif
@@ skipping 1152 matching lines @@
   void PushObject(const Object& object, Register pp) {
     LoadObject(TMP, object, pp);
     Push(TMP);
   }
   void CompareObject(Register reg, const Object& object, Register pp);
 
   void LoadClassId(Register result, Register object, Register pp);
   void LoadClassById(Register result, Register class_id, Register pp);
   void LoadClass(Register result, Register object, Register pp);
   void CompareClassId(Register object, intptr_t class_id, Register pp);
+  void LoadTaggedClassIdMayBeSmi(Register result, Register object);
 
   void EnterFrame(intptr_t frame_size);
   void LeaveFrame();
 
   // When entering Dart code from C++, we copy the system stack pointer (CSP)
   // to the Dart stack pointer (SP), and reserve a little space for the stack
   // to grow.
   void SetupDartSP(intptr_t reserved_space) {
     ASSERT(Utils::IsAligned(reserved_space, 16));
     mov(SP, CSP);
@@ skipping 486 matching lines @@
                                   Register value,
                                   Label* no_update);
 
   DISALLOW_ALLOCATION();
   DISALLOW_COPY_AND_ASSIGN(Assembler);
 };
 
 }  // namespace dart
 
 #endif  // VM_ASSEMBLER_ARM64_H_