From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 59607 invoked by alias); 7 Jul 2015 14:48:24 -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 59537 invoked by uid 48); 7 Jul 2015 14:48:20 -0000 From: "hjl.tools at gmail dot com" To: gcc-bugs@gcc.gnu.org Subject: [Bug target/66703] [4.9/5/6] gcc.target/i386/readeflags-1.c aborts on -march=i586 or on -miamcu Date: Tue, 07 Jul 2015 14:48:00 -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: 4.9.3 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: hjl.tools at gmail dot com X-Bugzilla-Status: RESOLVED X-Bugzilla-Resolution: WONTFIX 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: 2015-07/txt/msg00546.txt.bz2 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66703 --- Comment #3 from H.J. Lu --- (In reply to Yulia Koval from comment #2) > Why zero-extend with and is better than zero-extend with movz? Why it's ok > to clobber the flags? According to Intel Pentium optimization guide, zero-extend with and is faster than zero-extend with movz. It is OK to clobber EFLAGS to do unsigned int x = (unsigned int) b; where b is a boolean value.