Merged r11907 into 3.11 branch.

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 f62528e34a4513e4a6269ca2e5edf39806f7adee..7dc38a1429f8758e6abb5ae4eb84ec04d077d99b 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -2235,10 +2235,15 @@ void LCodeGen::EmitLoadFieldOrConstantFunction(Register result,
 
 // Check for cases where EmitLoadFieldOrConstantFunction needs to walk the
 // prototype chain, which causes unbounded code generation.
-static bool CompactEmit(
-    SmallMapList* list, Handle<String> name, int i, Isolate* isolate) {
-  LookupResult lookup(isolate);
+static bool CompactEmit(SmallMapList* list,
+                        Handle<String> name,
+                        int i,
+                        Isolate* isolate) {
   Handle<Map> map = list->at(i);
+  // If the map has ElementsKind transitions, we will generate map checks
+  // for each kind in __ CompareMap(..., ALLOW_ELEMENTS_TRANSITION_MAPS).
+  if (map->elements_transition_map() != NULL) return false;
+  LookupResult lookup(isolate);
   map->LookupInDescriptors(NULL, *name, &lookup);
   return lookup.IsFound() &&
       (lookup.type() == FIELD || lookup.type() == CONSTANT_FUNCTION);