Better support for 'polymorphic' JS and external arrays

src/x64/macro-assembler-x64.cc

Index: src/x64/macro-assembler-x64.cc
diff --git a/src/x64/macro-assembler-x64.cc b/src/x64/macro-assembler-x64.cc
index 339420679184b15ead2d8a4921d07368eeb86106..fc9840edfcfce4b4d86a10a7032d2c31bfe1fc08 100644
--- a/src/x64/macro-assembler-x64.cc
+++ b/src/x64/macro-assembler-x64.cc
@@ -1896,6 +1896,36 @@ void MacroAssembler::CheckMap(Register obj,
 }
 
 
+void MacroAssembler::CheckMaps(Register obj,
+                               ZoneMapList* receiver_maps,
+                               Label* fail,
+                               bool is_heap_object) {
+  if (!is_heap_object) {
+    testb(obj, Immediate(kSmiTagMask));
+    j(zero, fail);
+  }
+
+  // Check that the map matches.
+  if (receiver_maps->length() == 0) {
+    jmp(fail);
+  } else if (receiver_maps->length() == 1) {
+    Cmp(FieldOperand(obj, HeapObject::kMapOffset), receiver_maps->at(0));
+    j(not_equal, fail);
+  } else {
+    NearLabel map_match;
+    for (int current = 0; current < receiver_maps->length() - 1; ++current) {
+      Handle<Map> current_map = receiver_maps->at(current);
+      Cmp(FieldOperand(obj, HeapObject::kMapOffset), current_map);
+      j(equal, &map_match);
+    }
+    Cmp(FieldOperand(obj, HeapObject::kMapOffset),
+        receiver_maps->at(receiver_maps->length()-1));
+    j(not_equal, fail);
+    bind(&map_match);
+  }
+}
+
+
 void MacroAssembler::AbortIfNotNumber(Register object) {
   NearLabel ok;
   Condition is_smi = CheckSmi(object);