Use the property load IC for accessing the array length.

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index 2bcf943ab6cb3963fe9c8b53f0a3679355c9048e..ff6067f74994bd1c74f4f1241571c187c8e6bd45 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -4514,11 +4514,11 @@ void LCodeGen::DoCheckMaps(LCheckMaps* instr) {
   SmallMapList* map_set = instr->hydrogen()->map_set();
   for (int i = 0; i < map_set->length() - 1; i++) {
     Handle<Map> map = map_set->at(i);
-    __ CompareMap(reg, map, &success, REQUIRE_EXACT_MAP);
+    __ CompareMap(reg, map, &success, instr->hydrogen()->mode());
     __ j(equal, &success);
   }
   Handle<Map> map = map_set->last();
-  DoCheckMapCommon(reg, map, REQUIRE_EXACT_MAP, instr->environment());
+  DoCheckMapCommon(reg, map, instr->hydrogen()->mode(), instr->environment());
   __ bind(&success);
 }