220 8384 <028701aa-9798-4cd1-a77f-9fa4f9de0b79@isocpp.org> article Path: news.gmane.org!not-for-mail From: fmatthew5876@gmail.com Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Proposal: standardize [[noinline]] Date: Thu, 2 Jan 2014 21:56:12 -0800 (PST) Lines: 69 Approved: news@gmane.org Message-ID: <028701aa-9798-4cd1-a77f-9fa4f9de0b79@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_10263_32875881.1388728572210" X-Trace: ger.gmane.org 1388728571 10329 80.91.229.3 (3 Jan 2014 05:56:11 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 3 Jan 2014 05:56:11 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDELF54RTIGRB7NBTGLAKGQEURQEDRY@isocpp.org Fri Jan 03 06:56:19 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pa0-f70.google.com ([209.85.220.70]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Vyxjy-0005cW-U9 for gclcip-std-proposals@m.gmane.org; Fri, 03 Jan 2014 06:56:15 +0100 Original-Received: by mail-pa0-f70.google.com with SMTP id fa1sf48076120pad.1 for ; Thu, 02 Jan 2014 21:56:13 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=date:from:to:message-id:subject:mime-version:x-original-sender :reply-to:precedence:mailing-list:list-id:list-post:list-help :list-archive:list-subscribe:list-unsubscribe:content-type; bh=etBeDBfLb3hjCb711eFPwRUJyMUlFy4hvn9TbifEEGw=; b=nrwdEmXnXeIfvie9X7oqmlclwAtJdNLkJEJ9NuFC4p+aLj0jIvBTmUMLu7IQzlSbCS 36bLBcmVR7kS2rwQxY7YoPXYxcpKjKbJqrfvhS1QVahpzvxg+yFHFNTFpm62vLn3gACN dgkZasMyt5FW6yClWyfVPcIC0Esv+6OskrjG3/D5BgzKcId0iVef1j+1j/4seNYtFkV5 1lr5WvpBZAZEmmV/36CW6kmtlXuUUxNRSHBXwfiFGf8QtcHrsfVfl7WOYHYMNX7H3zqK O071ogkhizexdv+Ek6lMOtGw/1Cm3iWsi8B4PW7caEBYw79tcfm+MkI39REClb5XE3L3 /dfQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:date:from:to:message-id:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe :content-type; bh=etBeDBfLb3hjCb711eFPwRUJyMUlFy4hvn9TbifEEGw=; b=cTtyLq/LA2HJYvu7GsphZbzsf99zVPCSzzQMyUQvjgkUhfskr8p5EMxY9Z9K17Taqp GtY8tnq6eyHeuFUO4Wnzvguo/gwwBb39rlm1RY15vVELctixdbJnYHI5zfPfnwKsefTy TdOf08ww4V1p2xtWQxBkmvxdNtER3Nmx0P20VkAEA7UMbHtn/xE7Uv0U3pJ3wnv0Lrxz +q4ouRggxq66a7CWr42NDWPQycm67QQn8INX3T55MDKD/9FLsO4ux83Ylda77McfNb2J QEsupTASo8gMGayy9DQ05fanX27k/+ZjiFC67+NHxK21AeN11I8eIjz4mAq8Z0EOsLEh 6Nfw== X-Gm-Message-State: ALoCoQktY8KZKVTmtqHTCsGpBBBUdQ122iPTY+4vJ1dIdhzl5uYJQnu2vVnQqmUesI1deCTSOnIU X-Received: by 10.68.254.230 with SMTP id al6mr35177656pbd.6.1388728573747; Thu, 02 Jan 2014 21:56:13 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.49.37.195 with SMTP id a3ls4588800qek.88.gmail; Thu, 02 Jan 2014 21:56:12 -0800 (PST) X-Received: by 10.49.94.144 with SMTP id dc16mr1803qeb.21.1388728572927; Thu, 02 Jan 2014 21:56:12 -0800 (PST) X-Original-Sender: fmatthew5876@gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:8384 Archived-At: ------=_Part_10263_32875881.1388728572210 Content-Type: text/plain; charset=ISO-8859-1 Inlining is one of the most powerful performance features of C++. Modern compilers may attempt to inline anything, even non-inline functions. With the advent of link time optimization / whole program optimization, inlining is potentially and unpredictably on the table for any function in the entire application. Sometimes we want to write synthetic code, particularly for benchmarks where we want to isolate a bit of code to test its performance. We don't want any details of the caller interfering with the code to be tested. In many cases, the compiler will even optimize out our test entirely if it does not produce a meaningful result. In this important use case, inlining can get in the way. The best way to write such benchmarks is to use __attribute__((noinline)) or its proposed standard equivalent [[noinline]]. This attribute ensures a function is compiled stand alone, without any influence from callers.Thus we can be confident in isolating it and testing its performance portably across all of our supported platforms. Any objections? -- --- You received this message because you are subscribed to the Google Groups "ISO C++ Standard - Future Proposals" group. To unsubscribe from this group and stop receiving emails from it, send an email to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposals/. ------=_Part_10263_32875881.1388728572210 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
Inlining is one of the most powerful performance features = of C++. Modern compilers may attempt to inline anything, even non-inline fu= nctions. With the advent of link time optimization / whole program optimiza= tion, inlining is potentially and unpredictably on the table for any functi= on in the entire application. 

Sometimes we want to= write synthetic code, particularly for benchmarks where we want to isolate= a bit of code to test its performance. We don't want any details of the ca= ller interfering with the code to be tested. In many cases, the compiler wi= ll even optimize out our test entirely if it does not produce a meaningful = result. In this important use case, inlining can get in the way.
=
The best way to write such benchmarks is to use __attribute_= _((noinline)) or its proposed standard equivalent [[noinline]]. This attrib= ute ensures a function is compiled stand alone, without any influence from = callers.Thus we can be confident in isolating it and testing its performanc= e portably across all of our supported platforms.

= Any objections?

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