From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 27743 invoked by alias); 26 Oct 2010 13:41:24 -0000 Received: (qmail 27730 invoked by uid 22791); 26 Oct 2010 13:41:23 -0000 X-SWARE-Spam-Status: No, hits=-2.4 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00,MISSING_MID X-Spam-Check-By: sourceware.org Received: from localhost (HELO gcc.gnu.org) (127.0.0.1) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Tue, 26 Oct 2010 13:41:13 +0000 From: "jakub at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug target/46080] [4.4/4.5/4.6 Regression] incorrect precision of sqrtf builtin for x87 arithmetic (-mfpmath=387) X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: target X-Bugzilla-Keywords: wrong-code X-Bugzilla-Severity: normal X-Bugzilla-Who: jakub at gcc dot gnu.org X-Bugzilla-Status: NEW X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: 4.4.6 X-Bugzilla-Changed-Fields: In-Reply-To: References: X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 Date: Tue, 26 Oct 2010 13:41:00 -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 X-SW-Source: 2010-10/txt/msg02175.txt.bz2 Message-ID: <20101026134100.c66TxE40_e4vll0AjCTaold9bx_zGWIPisok1xy48IA@z> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46080 --- Comment #12 from Jakub Jelinek 2010-10-26 13:41:10 UTC --- Well, the setting of errno by calling another function has similar effects like calling any other function in between, if you do float a = sqrtf (x); foo (); float b = sqrtf (x); bar (); float c = sqrtf (x); printf ("%f %f %f\n", a, b, c); then there is similar problem - every call in between on i?86/x86_64 will clobber the i387 register stack in the ABI, so the values need to be flushed into memory and thus with the fast extended precision mode rounded to floating point precision, but the c value is probably kept in reg-stack and saved as a double instead of float, because of varargs in printf. Thus it can have different value.