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: Thu, 04 Sep 2014 09:03:47 -0700 Organization: UCLA Computer Science Department Message-ID: <54088D63.8010406@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> <54086B1A.8070506@yandex.ru> <54087B5E.10402@yandex.ru> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="------------020404000902010702090208" X-Trace: ger.gmane.org 1409846706 19307 80.91.229.3 (4 Sep 2014 16:05:06 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 4 Sep 2014 16:05:06 +0000 (UTC) Cc: Stefan Monnier , Emacs development discussions To: Dmitry Antipov Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Thu Sep 04 18:04:58 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 1XPZWr-0004Gl-Mo for ged-emacs-devel@m.gmane.org; Thu, 04 Sep 2014 18:04:57 +0200 Original-Received: from localhost ([::1]:52327 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XPZWq-0008VA-Et for ged-emacs-devel@m.gmane.org; Thu, 04 Sep 2014 12:04:56 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:50452) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XPZWC-0008F5-4F for emacs-devel@gnu.org; Thu, 04 Sep 2014 12:04:23 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XPZW4-0002cv-Cn for emacs-devel@gnu.org; Thu, 04 Sep 2014 12:04:16 -0400 Original-Received: from smtp.cs.ucla.edu ([131.179.128.62]:43521) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XPZW4-0002bi-2U for emacs-devel@gnu.org; Thu, 04 Sep 2014 12:04:08 -0400 Original-Received: from localhost (localhost.localdomain [127.0.0.1]) by smtp.cs.ucla.edu (Postfix) with ESMTP id 0095239E801C; Thu, 4 Sep 2014 09:04:00 -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 wYXk-XZEy5RR; Thu, 4 Sep 2014 09:03:51 -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 3094C39E8014; Thu, 4 Sep 2014 09:03:51 -0700 (PDT) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.0 In-Reply-To: <54087B5E.10402@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:174013 Archived-At: This is a multi-part message in MIME format. --------------020404000902010702090208 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Dmitry Antipov wrote: > I don't know how to use VLAs in the way similar to alloca For vectors the macro needs to generate a series of declarations and statements rather than an expression. It's less clean, but it's good enough. Something like the attached, say. --------------020404000902010702090208 Content-Type: text/x-csrc; name="safe-vla.c" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="safe-vla.c" /* Placeholders for what's in lisp.h already. */ #include #include #include typedef long Lisp_Object; enum { word_size = sizeof (Lisp_Object) }; enum { MAX_ALLOCA = 16 * 1024 }; #define USE_SAFE_ALLOCA bool sa_must_free = false #define SAFE_FREE() (sa_must_free ? magic_freer () : (void) 0) #define min(a, b) ((a) < (b) ? (a) : (b)) extern void *xnmalloc (size_t, size_t); extern Lisp_Object make_save_memory (Lisp_Object *, ptrdiff_t); extern void magic_freer (void); extern void record_unwind_protect (void (*) (Lisp_Object), Lisp_Object); extern void free_save_value (Lisp_Object); extern _Noreturn void memory_full (size_t); /* The new macro. */ #ifdef __STDC_NO_VLA__ # define SAFE_LISP_ARRAY(name, elems) \ Lisp_Object *name; \ SAFE_ALLOCA_LISP (name, elems) #else # define SAFE_LISP_ARRAY(name, elems) \ ptrdiff_t name##n = elems; \ bool name##issmall = name##n <= MAX_ALLOCA / word_size; \ Lisp_Object name##vec[name##issmall && name##n ? name##n : 1]; \ Lisp_Object *name; \ if (name##issmall) \ name = name##vec; \ else \ { \ name = xnmalloc (name##n, word_size); \ record_unwind_protect (free_save_value, \ make_save_memory (name, name##n)); \ sa_must_free = true; \ } #endif /* Example use. */ Lisp_Object foo (ptrdiff_t n) { USE_SAFE_ALLOCA; SAFE_LISP_ARRAY (foo, n); for (ptrdiff_t i = 0; i < n; i++) foo[i] = i; Lisp_Object x = 0; for (ptrdiff_t i = 0; i < n; i++) x ^= foo[0]; SAFE_FREE (); return x; } --------------020404000902010702090208--