From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 241833856DFB; Wed, 18 May 2022 15:24:37 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 241833856DFB From: "cvs-commit at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug middle-end/98865] Missed transform of (a >> 63) * b Date: Wed, 18 May 2022 15:24:36 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: middle-end X-Bugzilla-Version: 11.0 X-Bugzilla-Keywords: missed-optimization X-Bugzilla-Severity: normal X-Bugzilla-Who: cvs-commit at gcc dot gnu.org X-Bugzilla-Status: NEW X-Bugzilla-Resolution: 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-BeenThere: gcc-bugs@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-bugs mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 18 May 2022 15:24:37 -0000 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D98865 --- Comment #6 from CVS Commits --- The master branch has been updated by Roger Sayle : https://gcc.gnu.org/g:4a9be8d51182076222d707d9d68f6eda78e8ee2c commit r13-624-g4a9be8d51182076222d707d9d68f6eda78e8ee2c Author: Roger Sayle Date: Wed May 18 16:23:01 2022 +0100 Correct ix86_rtx_cost for multi-word multiplication. This is the i386 backend specific piece of my revised patch for PR middle-end/98865, where Richard Biener has suggested that I perform the desired transformation during RTL expansion where the backend can control whether it is profitable to convert a multiplication into a bit-wise AND and a negation. This works well for x86_64, but alas exposes a latent bug with -m32, where a DImode multiplication incorrect= ly appears to be cheaper than negdi2+anddi3(!?). The fix to ix86_rtx_costs is to report that a DImode (multi-word) multiplication actually requires three SImode multiplications and two SImode additions. This also corre= cts the cost of TImode multiplication on TARGET_64BIT. 2022-05-18 Roger Sayle gcc/ChangeLog * config/i386/i386.cc (ix86_rtx_costs) [MULT]: When mode size is wider than word_mode, a multiplication costs three word_mode multiplications and two word_mode additions.=