Request for comments on overall approach.

runtime/vm/assembler_ia32.h

 // Copyright (c) 2012, 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_IA32_H_
 #define VM_ASSEMBLER_IA32_H_
 
 #ifndef VM_ASSEMBLER_H_
 #error Do not include assembler_ia32.h directly; use assembler.h instead.
 #endif
@@ skipping 511 matching lines @@
     lock();
     cmpxchgl(address, reg);
   }
 
   void EnterFrame(intptr_t frame_space);
   void LeaveFrame();
 
   void CallRuntime(const RuntimeEntry& entry);
 
   /*
+   * Loading and comparing classes of objects
+   */
+  void GetClassOf(Register result, Register object, Register scratch);
+
+  void LoadObjectClassId(Register result, Register object);
+
+  void CompareClassOf(Register object, const Class& clazz, Register scratch);

[Ivan Posva, 2012/05/26 04:34:46]

When do you ever have to compare classes? Or asked differently: In which
situation are classids not good enough?

[Vyacheslav Egorov (Google), 2012/05/26 16:48:22]

This macros was introduced initially to cover a very common code pattern that
loads class and then compares to some constant. 

This does compare class ids internally. 

I can expand it in places where it is used but it seems cleaner when it's
collapsed.

+
+  void CompareClassId(Register clsid, const Class& cls) {
+    cmpl(clsid, Immediate(cls.index()));
+  }
+
+  /*
    * Misc. functionality
    */
   void SmiTag(Register reg) {
     addl(reg, reg);
   }
 
   void SmiUntag(Register reg) {
     sarl(reg, Immediate(kSmiTagSize));
   }
 
@@ skipping 91 matching lines @@
 }
 
 
 inline void Assembler::EmitOperandSizeOverride() {
   EmitUint8(0x66);
 }
 
 }  // namespace dart
 
 #endif  // VM_ASSEMBLER_IA32_H_