In generated code for ia32 don't load object's class directly from class_ field.

runtime/vm/assembler_ia32.cc

 // Copyright (c) 2011, 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"
 #if defined(TARGET_ARCH_IA32)
 
 #include "vm/assembler.h"
 #include "vm/heap.h"
 #include "vm/memory_region.h"
@@ skipping 1544 matching lines @@
 void Assembler::EmitGenericShift(int rm,
                                  Register operand,
                                  Register shifter) {
   AssemblerBuffer::EnsureCapacity ensured(&buffer_);
   ASSERT(shifter == ECX);
   EmitUint8(0xD3);
   EmitOperand(rm, Operand(operand));
 }
 
 
+void Assembler::LoadClassOfObject(Register result,
+                                  Register object,
+                                  Register scratch) {
+  ASSERT(scratch != result);
+  LoadClassIndexOfObject(scratch, object);
+
+  movl(result, FieldAddress(CTX, Context::isolate_offset()));
+  const intptr_t table_offset_in_isolate =
+      Isolate::class_table_offset() + ClassTable::table_offset();
+  movl(result, Address(result, table_offset_in_isolate));
+  movl(result, Address(result, scratch, TIMES_4, 0));
+}
+
+
+void Assembler::LoadClassIndexOfObject(Register result, Register object) {
+  ASSERT(RawObject::kClassTagBit == 16);
+  ASSERT(RawObject::kClassTagSize == 16);
+  const intptr_t class_id_offset = Object::tags_offset() +
+      RawObject::kClassTagBit / kBitsPerByte;
+  movzxw(result, FieldAddress(object, class_id_offset));
+}
+
+
+void Assembler::CompareClassOfObject(Register object,
+                                     const Class& clazz,
+                                     Register scratch) {
+  LoadClassIndexOfObject(scratch, object);
+  cmpl(scratch, Immediate(clazz.index()));
+}
+
+
 void Assembler::Comment(const char* comment) {
   if (FLAG_code_comments) {
     comments_.Add(new CodeComment(buffer_.GetPosition(),
                                   String::Handle(String::New(comment))));
   }
 }
 
 
 const Code::Comments& Assembler::GetCodeComments() const {
   Code::Comments& comments = Code::Comments::New(comments_.length());
 
   for (intptr_t i = 0; i < comments_.length(); i++) {
     comments.SetPCOffsetAt(i, comments_[i]->pc_offset());
     comments.SetCommentAt(i, comments_[i]->comment());
   }
 
   return comments;
 }
 
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32