Back port r11886: Fix GC bug with missing handle. Bug=133618

src/x64/lithium-codegen-x64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2200 matching lines @@
       // Non-negative property indices are in the properties array.
       __ movq(result, FieldOperand(object, JSObject::kPropertiesOffset));
       __ movq(result, FieldOperand(result, offset + FixedArray::kHeaderSize));
     }
   } else if (lookup.IsFound() && lookup.type() == CONSTANT_FUNCTION) {
     Handle<JSFunction> function(lookup.GetConstantFunctionFromMap(*type));
     __ LoadHeapObject(result, function);
   } else {
     // Negative lookup.
     // Check prototypes.
-    HeapObject* current = HeapObject::cast((*type)->prototype());
+    Handle<HeapObject> current(HeapObject::cast((*type)->prototype()));
     Heap* heap = type->GetHeap();
-    while (current != heap->null_value()) {
-      Handle<HeapObject> link(current);
-      __ LoadHeapObject(result, link);
+    while (*current != heap->null_value()) {
+      __ LoadHeapObject(result, current);
       __ Cmp(FieldOperand(result, HeapObject::kMapOffset),
-                          Handle<Map>(JSObject::cast(current)->map()));
+                          Handle<Map>(current->map()));
       DeoptimizeIf(not_equal, env);
-      current = HeapObject::cast(current->map()->prototype());
+      current =
+          Handle<HeapObject>(HeapObject::cast(current->map()->prototype()));
     }
     __ LoadRoot(result, Heap::kUndefinedValueRootIndex);
   }
 }
 
 
 // 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) {
@@ skipping 2705 matching lines @@
                                FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64