Copy-on-write arrays.

src/ia32/macro-assembler-ia32.cc

Index: src/ia32/macro-assembler-ia32.cc
diff --git a/src/ia32/macro-assembler-ia32.cc b/src/ia32/macro-assembler-ia32.cc
index 66ec04facb1c8695b0cc925bdb3efc6b0dd60eaa..69ecf214a82ae471b385024d9393bf553bb80f1b 100644
--- a/src/ia32/macro-assembler-ia32.cc
+++ b/src/ia32/macro-assembler-ia32.cc
@@ -1464,6 +1464,21 @@ void MacroAssembler::Assert(Condition cc, const char* msg) {
 }
 
 
+void MacroAssembler::AssertFastElements(Register elements) {
+  if (FLAG_debug_code) {
+    Label ok;
+    cmp(FieldOperand(elements, HeapObject::kMapOffset),
+        Immediate(Factory::fixed_array_map()));
+    j(equal, &ok);
+    cmp(FieldOperand(elements, HeapObject::kMapOffset),
+        Immediate(Factory::fixed_cow_array_map()));
+    j(equal, &ok);
+    Abort("JSObject with fast elements map has slow elements");
+    bind(&ok);
+  }
+}
+
+
 void MacroAssembler::Check(Condition cc, const char* msg) {
   Label L;
   j(cc, &L, taken);