From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 6181 invoked by alias); 25 Mar 2009 06:06:21 -0000 Received: (qmail 5682 invoked by uid 22791); 25 Mar 2009 06:06:20 -0000 X-SWARE-Spam-Status: No, hits=-2.4 required=5.0 tests=AWL,BAYES_00,SARE_MILLIONSOF,SPF_PASS X-Spam-Check-By: sourceware.org Received: from mail-gx0-f207.google.com (HELO mail-gx0-f207.google.com) (209.85.217.207) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Wed, 25 Mar 2009 06:06:15 +0000 Received: by gxk3 with SMTP id 3so7142318gxk.8 for ; Tue, 24 Mar 2009 23:06:13 -0700 (PDT) Received: by 10.90.82.17 with SMTP id f17mr5223281agb.41.1237961173160; Tue, 24 Mar 2009 23:06:13 -0700 (PDT) Received: from ?18.138.1.33? (M7-100-4.MIT.EDU [18.138.1.33]) by mx.google.com with ESMTPS id 5sm11580029agc.14.2009.03.24.23.06.12 (version=SSLv3 cipher=RC4-MD5); Tue, 24 Mar 2009 23:06:12 -0700 (PDT) Message-ID: <49C9C9D3.9000502@gmail.com> Date: Wed, 25 Mar 2009 06:06:00 -0000 From: Yang Zhang User-Agent: Thunderbird 2.0.0.21 (X11/20090318) MIME-Version: 1.0 To: Ian Lance Taylor CC: GCC-help Subject: Re: Profiling compilation time References: <49C8A53A.8000104@gmail.com> <49C9159E.108@gmail.com> <49C933FA.5060805@gmail.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-IsSubscribed: yes Mailing-List: contact gcc-help-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-help-owner@gcc.gnu.org X-SW-Source: 2009-03/txt/msg00315.txt.bz2 Ian Lance Taylor wrote: > In my experience, when not optimizing, C++ compilation time is normally > dominated by parsing and name lookup. From an earlier thread "Precompiled headers and templates:" Ian Lance Taylor wrote: > However, including explicit instantiations in the precompiled header > won't make any significant difference to compilation time. The > precompiled header saves on parsing and name lookup time, it doesn't > save on code generation time. > > I don't personally find that precompiled headers help with compilation > time all that much. However, for some projects, ones with millions of > lines of header files included in every compilation, I expect that they > would help. So PCHs only help with a very small fraction of the parsing + name lookup? (Already established that they wouldn't include template instantiation component of paths.) -- Yang Zhang http://www.mit.edu/~y_z/