Fix a bug in delete for lookup slots.

src/x64/full-codegen-x64.cc

 // Copyright 2011 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 2988 matching lines @@
                  var->AsSlot()->type() != Slot::LOOKUP) {
         // Result of deleting non-global, non-dynamic variables is false.
         // The subexpression does not have side effects.
         context()->Plug(false);
       } else {
         // Property or variable reference.  Call the delete builtin with
         // object and property name as arguments.
         if (prop != NULL) {
           VisitForStackValue(prop->obj());
           VisitForStackValue(prop->key());
+          __ InvokeBuiltin(Builtins::DELETE, CALL_FUNCTION);
         } else if (var->is_global()) {
           __ push(GlobalObjectOperand());
           __ Push(var->name());
+          __ InvokeBuiltin(Builtins::DELETE, CALL_FUNCTION);
         } else {
-          // Non-global variable.  Call the runtime to look up the context
-          // where the variable was introduced.
+          // Non-global variable.  Call the runtime to delete from the
+          // context where the variable was introduced.
           __ push(context_register());
           __ Push(var->name());
-          __ CallRuntime(Runtime::kLookupContext, 2);
-          __ push(rax);
-          __ Push(var->name());
+          __ CallRuntime(Runtime::kDeleteContextSlot, 2);
         }
-        __ InvokeBuiltin(Builtins::DELETE, CALL_FUNCTION);
         context()->Plug(rax);
       }
       break;
     }
 
     case Token::VOID: {
       Comment cmnt(masm_, "[ UnaryOperation (VOID)");
       VisitForEffect(expr->expression());
       context()->Plug(Heap::kUndefinedValueRootIndex);
       break;
@@ skipping 611 matching lines @@
   __ ret(0);
 }
 
 
 #undef __
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64