From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 19263 invoked by alias); 1 Aug 2005 19:01:31 -0000 Mailing-List: contact gcc-help-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Archive: List-Post: List-Help: Sender: gcc-help-owner@gcc.gnu.org Received: (qmail 19247 invoked by uid 22791); 1 Aug 2005 19:01:27 -0000 Received: from faui03.informatik.uni-erlangen.de (HELO faui03.informatik.uni-erlangen.de) (131.188.30.103) by sourceware.org (qpsmtpd/0.30-dev) with ESMTP; Mon, 01 Aug 2005 19:01:27 +0000 Received: from faui00i.informatik.uni-erlangen.de (sijoange@faui00i.informatik.uni-erlangen.de [131.188.30.68]) by faui03.informatik.uni-erlangen.de (8.12.11/8.12.11) with ESMTP id j71J1Paf005556 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Mon, 1 Aug 2005 19:01:25 GMT Received: (from sijoange@localhost) by faui00i.informatik.uni-erlangen.de (8.13.4/8.12.3/Debian-8) id j71J1P3x021120 for gcc-help@gcc.gnu.org; Mon, 1 Aug 2005 21:01:25 +0200 From: Josef Angermeier Date: Mon, 01 Aug 2005 19:01:00 -0000 To: gcc-help@gcc.gnu.org Subject: Re: gcc's x86 "RET"-machine instruction optimization Message-ID: <20050801190125.GE11284@faui00i.informatik.uni-erlangen.de> References: <20050801135646.GC11284@faui00i.informatik.uni-erlangen.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.9i X-SW-Source: 2005-08/txt/msg00016.txt.bz2 Hello > > GCC uses a jmp-instruction instead of a call one, so 'speeds up' execution by > > saving the execution of bios_16_xxxx's return instruction (lretw one). This of course > > ruins my efforts. Therfore i'd like to know how this optimization is called, and if > > there is any gcc option to disable this particular optimization. > These are called sibling calls, and you can turn the optimization off > using -fno-optimize-sibling-calls. oh great! > (I wouldn't be surprised if you run into other problems with your > approach, but that switch should take care of that particular > problem.) Mmm, i'd appreciate all hints to what problems could happen when going this approach. Doesn't matter how vague. > Ian Thanks Ian, again ! josef ciao