From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 84113385840E; Fri, 11 Feb 2022 15:24:57 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 84113385840E From: "rearnsha at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug target/104455] Cannot select -march=armv7-a using GCC 11 Date: Fri, 11 Feb 2022 15:24:57 +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: 11.0 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: rearnsha at gcc dot gnu.org X-Bugzilla-Status: RESOLVED X-Bugzilla-Resolution: INVALID 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: Fri, 11 Feb 2022 15:24:57 -0000 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D104455 --- Comment #5 from Richard Earnshaw --- (In reply to Jeffrey Walton from comment #4) >=20 > So stepping back to 10,000 feet, we now need to specify options and ISA's= we > are not using. That seems like a bug to me. I'm not sure I would consider > this fixed. >=20 > Where is it going to stop? How many non-used options that I am not aware = of > will I need to specify? >=20 > I think either GCC or Debian needs to fix this. This could be a GCC bug > because GCC apparently knows there's a fp unit but it chooses to ignore i= t. > Instead it wants me to say it again. This could be a Debian bug because t= hey > need to completely (not partially) configure things. No, it knows it /needs/ a FP unit, but you haven't told it which one is available. The Arm architecture has many variants and not all are necessar= ily compatible with a base set, so you have to explicitly state which one is intended. Assumptions are a potential source of massive misunderstandings. Note, in the past the FPU variant was baked into the compiler when it was configured and this lead to all forms of confusion because if you had a Neon FPU and then started compiling for a cortex-m device you could still end up with Neon instructions in your code because there was no explicit option to turn it off. We've gone as far as we can by allowing you to simply specify '+fp' rather than having to know exactly which variant of the VFP architect= ure goes with armv7-a. Also note that clang has the same option logic for CPU selection.=