From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 28168 invoked by alias); 10 Jul 2014 16:10:28 -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 27985 invoked by uid 48); 10 Jul 2014 16:10:17 -0000 From: "ubizjak at gmail dot com" To: gcc-bugs@gcc.gnu.org Subject: [Bug target/61656] Undefined behavior in classify_argument Date: Thu, 10 Jul 2014 16:10:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: target X-Bugzilla-Version: 4.10.0 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: ubizjak at gmail dot com 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: quoted-printable X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-SW-Source: 2014-07/txt/msg00659.txt.bz2 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D61656 --- Comment #6 from Uro=C5=A1 Bizjak --- (In reply to Jakub Jelinek from comment #5) > then it uses movq %rsi, ... and the patch doesn't change anything on that. > If you want to use movl %esi, ... in foo in this testcase, more changes a= re > needed of course. This is allowed, as long as we don't use movl on a DImode value. So, your proposed patch avoids undefined issue, while optimizes memory access a bit. >>From gcc-bugs-return-456069-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Thu Jul 10 16:17:14 2014 Return-Path: Delivered-To: listarch-gcc-bugs@gcc.gnu.org Received: (qmail 6177 invoked by alias); 10 Jul 2014 16:17:13 -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 Delivered-To: mailing list gcc-bugs@gcc.gnu.org Received: (qmail 5930 invoked by uid 48); 10 Jul 2014 16:17:04 -0000 From: "jakub at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug target/61656] Undefined behavior in classify_argument Date: Thu, 10 Jul 2014 16:17:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: target X-Bugzilla-Version: 4.10.0 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal 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: 2014-07/txt/msg00660.txt.bz2 Content-length: 510 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61656 --- Comment #7 from Jakub Jelinek --- The patch actually just removes the undefined behavior and nothing else, it really doesn't affect code generation. It just causes merge_classes (which is a const function) not to be called on (initialized) subclasses[i] and (uninitialized) classes[i], storing the result back to classes[i]. We are not going to use the result of the merger of the initialized and uninitialized value later.