From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 20880 invoked by alias); 30 Dec 2013 17:56:41 -0000 Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org Received: (qmail 20850 invoked by uid 48); 30 Dec 2013 17:56:38 -0000 From: "jakub at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug c/59615] "asm goto" output or at least clobbered operands Date: Mon, 30 Dec 2013 17:56:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: c X-Bugzilla-Version: unknown X-Bugzilla-Keywords: X-Bugzilla-Severity: enhancement X-Bugzilla-Who: jakub at gcc dot gnu.org X-Bugzilla-Status: UNCONFIRMED X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-SW-Source: 2013-12/txt/msg02420.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59615 --- Comment #7 from Jakub Jelinek --- (In reply to Marc Glisse from comment #6) > (In reply to Jakub Jelinek from comment #4) > > Anyway, you definitely don't want > > to use inline asm in this case, if there is some code GCC doesn't optimize > > as good as you'd like to, just report that. > > One common similar case where people are tempted to use asm goto with an > output operand is, on x86: compute a*b and check if it overflowed. x86 has > flags for that but AFAIR they are not modeled in the .md files. (I was also > interested in output operands for asm goto in PR52381, but there is no good > example there) They are modelled in the .md files now, we just don't have general purpose builtins for this yet in GCC 4.9, it is only used for -fsanitize=undefined right now.