Minor cleanup in assembly code.

runtime/vm/stub_code_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/code_generator.h"
 #include "vm/compiler.h"
 #include "vm/object_store.h"
@@ skipping 1741 matching lines @@
   __ j(EQUAL, &ic_cache_one_arg, Assembler::kNearJump);
   __ jmp(&StubCode::TwoArgsCheckInlineCacheLabel());
   __ Bind(&ic_cache_one_arg);
   __ jmp(&StubCode::OneArgCheckInlineCacheLabel());
 }
 
 
 // Check if an instance class is a subtype of class/interface using simple
 // superchain and interface array traversal. Does not take type parameters into
 // account.
-// EAX: instance.
+// EAX: instance (preserved)
 // EDX: class/interface to test against (is class of instance a subtype of it).
-// Result in EDX: 1 is subtype, 0 maybe not.
+//      (preserved).
+// Result in EBX: 1 is subtype, 0 maybe not.
 // Destroys EBX, ECX.
 void StubCode::GenerateIsRawSubTypeStub(Assembler* assembler) {
   const Immediate raw_null =
       Immediate(reinterpret_cast<intptr_t>(Object::null()));
   Label test_class, not_found, found, class_loaded_in_ECX, smi_value;
   __ EnterFrame(0);
   __ testl(EAX, Immediate(kSmiTagMask));
   __ j(ZERO, &smi_value, Assembler::kNearJump);
   __ movl(ECX, FieldAddress(EAX, Object::class_offset()));
   __ jmp(&class_loaded_in_ECX, Assembler::kNearJump);
@@ skipping 23 matching lines @@
   __ j(LESS, &not_found, Assembler::kNearJump);
   // EDI is Smi therefore TIMES_2 instead of TIMES_4.
   // Get type from array.
   __ movl(ECX, FieldAddress(EBX, EDI, TIMES_2, Array::data_offset()));
   __ movl(ECX, FieldAddress(ECX, Type::type_class_offset()));
   __ cmpl(ECX, EDX);
   __ j(EQUAL, &found, Assembler::kNearJump);
   __ jmp(&array_loop, Assembler::kNearJump);
 
   __ Bind(&not_found);
-  __ xorl(EAX, EAX);
+  __ xorl(EBX, EBX);
   __ LeaveFrame();
   __ ret();
 
   __ Bind(&found);
-  __ movl(EAX, Immediate(1));
+  __ movl(EBX, Immediate(1));
   __ LeaveFrame();
   __ ret();
 
   __ Bind(&test_class);
   // EDX: test class.
   __ cmpl(ECX, EDX);
   __ j(EQUAL, &found, Assembler::kNearJump);
 
   // Check superclasses using a loop (faster than runtime call).
   Label super_loop;
   __ Bind(&super_loop);
   // ECX: class -> super.
   __ movl(ECX, FieldAddress(ECX, Class::super_type_offset()));
   // The supertype of Object is a null object.
   __ cmpl(ECX, raw_null);
   __ j(EQUAL, &not_found, Assembler::kNearJump);
   __ movl(ECX, FieldAddress(ECX, Type::type_class_offset()));
   __ cmpl(EDX, ECX);
   __ j(NOT_EQUAL, &super_loop, Assembler::kNearJump);
   __ jmp(&found, Assembler::kNearJump);
 }
 
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32