Correct handling of arrays with callbacks in the prototype chain.

src/ia32/macro-assembler-ia32.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
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@@ skipping 3532 matching lines @@
       JSArray::kSize + AllocationMemento::kSize - kHeapObjectTag));
   cmp(scratch_reg, Immediate(new_space_start));
   j(less, no_memento_found);
   cmp(scratch_reg, Operand::StaticVariable(new_space_allocation_top));
   j(greater, no_memento_found);
   cmp(MemOperand(scratch_reg, -AllocationMemento::kSize),
       Immediate(isolate()->factory()->allocation_memento_map()));
 }
 
 
+void MacroAssembler::HasElementCallbacksInPrototypeChain(
+    Register object,
+    Register elements,
+    Label* found) {
+  Factory* factory = isolate()->factory();
+  Register scratch = elements;
+  Label loop, not_found;
+
+  // ebx contained elements pointer.

[danno, 2013/10/30 12:17:45]

nit: comment is wrong above (no explicit register need to be named).

[mvstanton, 2013/10/30 18:22:28]

Done.

+  mov(scratch, FieldOperand(object, HeapObject::kMapOffset));

[danno, 2013/10/30 12:17:45]

If you move object into scratch before entering the loop and add a bind of a
label "loop_again" then at the end of the loop you can just use:

cmp(scratch, Immediate(factory->null_value()));
j(not_equal, &loop_again); 

and get rid of the

mov(scratch, FieldOperand(scratch, HeapObject::kMapOffset));
jmp(&loop);

[mvstanton, 2013/10/30 18:22:28]

Done.

+
+  // Loop based on the map going up the prototype chain.
+  bind(&loop);
+  test(FieldOperand(scratch, Map::kBitField4Offset),
+       Immediate(Smi::FromInt(Map::HasElementCallbacks::kMask)));
+  j(not_zero, found);
+
+  // Next map
+  mov(scratch, FieldOperand(scratch, Map::kPrototypeOffset));
+  cmp(scratch, Immediate(factory->null_value()));
+  j(equal, &not_found);
+  mov(scratch, FieldOperand(scratch, HeapObject::kMapOffset));
+  jmp(&loop);
+
+  // Restore ebx
+  bind(&not_found);
+  mov(elements, FieldOperand(object, JSObject::kElementsOffset));
+}
+
+
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32