From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Paul Eggert Newsgroups: gmane.emacs.devel Subject: Re: Benchmarking temporary Lisp objects [Was: Re: [RFC] temporary Lisp_Strings] Date: Wed, 03 Sep 2014 23:45:18 -0700 Organization: UCLA Computer Science Department Message-ID: <54080A7E.8080008@cs.ucla.edu> References: <5405BE5D.1090003@yandex.ru> <5405DE8B.4050201@yandex.ru> <5406EC21.4060200@yandex.ru> <5407281C.3090302@cs.ucla.edu> <54073621.2040403@yandex.ru> <540744F5.2010804@cs.ucla.edu> <5407F1B7.6090704@yandex.ru> <5407F4E6.2040809@cs.ucla.edu> <5407FDF4.7020504@yandex.ru> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Trace: ger.gmane.org 1409829272 7506 80.91.229.3 (4 Sep 2014 11:14:32 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 4 Sep 2014 11:14:32 +0000 (UTC) Cc: Emacs development discussions To: Dmitry Antipov Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Thu Sep 04 08:46:03 2014 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1XPQnz-0001Jx-Ba for ged-emacs-devel@m.gmane.org; Thu, 04 Sep 2014 08:46:03 +0200 Original-Received: from localhost ([::1]:49075 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XPQny-0007ZZ-VP for ged-emacs-devel@m.gmane.org; Thu, 04 Sep 2014 02:46:02 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:51550) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XPQnb-0007ZC-I8 for emacs-devel@gnu.org; Thu, 04 Sep 2014 02:45:47 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XPQnT-00040u-QL for emacs-devel@gnu.org; Thu, 04 Sep 2014 02:45:39 -0400 Original-Received: from smtp.cs.ucla.edu ([131.179.128.62]:51943) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XPQnT-00040f-K8 for emacs-devel@gnu.org; Thu, 04 Sep 2014 02:45:31 -0400 Original-Received: from localhost (localhost.localdomain [127.0.0.1]) by smtp.cs.ucla.edu (Postfix) with ESMTP id DC63139E801C; Wed, 3 Sep 2014 23:45:28 -0700 (PDT) X-Virus-Scanned: amavisd-new at smtp.cs.ucla.edu Original-Received: from smtp.cs.ucla.edu ([127.0.0.1]) by localhost (smtp.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id G84Nw5r-o4xP; Wed, 3 Sep 2014 23:45:20 -0700 (PDT) Original-Received: from [192.168.1.9] (pool-71-177-17-123.lsanca.dsl-w.verizon.net [71.177.17.123]) by smtp.cs.ucla.edu (Postfix) with ESMTPSA id 2E42F39E8014; Wed, 3 Sep 2014 23:45:20 -0700 (PDT) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.0 In-Reply-To: <5407FDF4.7020504@yandex.ru> X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.6.x X-Received-From: 131.179.128.62 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Original-Sender: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.devel:174003 Dmitry Antipov wrote: > I'm talking about the case when we can't us __attribute__ ((aligned (X))). How about something like this? typedef unsigned long uintptr_t; typedef uintptr_t Lisp_Object; struct Lisp_Cons { Lisp_Object car; Lisp_Object cdr; }; static Lisp_Object cons_init (void *result, Lisp_Object a, Lisp_Object b) { struct Lisp_Cons *p = (struct Lisp_Cons *) (((uintptr_t) result + 7) & -8); p->car = a; p->cdr = b; return (Lisp_Object) p + 3; } #define BCONS(a, b) cons_init ((char[sizeof (struct Lisp_Cons) + 7]){}, a, b) #define untag(x) ((struct Lisp_Cons *) (uintptr_t) ((x) - 3)) int foo (void) { Lisp_Object a = BCONS (0, 0); Lisp_Object b = BCONS (0, a); return untag (untag(b) -> cdr) -> car; }