From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id B20ED385840C; Sat, 19 Mar 2022 23:28:39 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org B20ED385840C From: "dv at vollmann dot ch" To: gcc-bugs@gcc.gnu.org Subject: [Bug libgcc/104988] New: Zero register (R1) clobbered by __udivmodsi4 for AVR Date: Sat, 19 Mar 2022 23:28:39 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: libgcc X-Bugzilla-Version: 12.0 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: dv at vollmann dot ch X-Bugzilla-Status: UNCONFIRMED 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: bug_id short_desc product version bug_status bug_severity priority component assigned_to reporter cc target_milestone attachments.created Message-ID: 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: Sat, 19 Mar 2022 23:28:39 -0000 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D104988 Bug ID: 104988 Summary: Zero register (R1) clobbered by __udivmodsi4 for AVR Product: gcc Version: 12.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: libgcc Assignee: unassigned at gcc dot gnu.org Reporter: dv at vollmann dot ch CC: dv at vollmann dot ch Target Milestone: --- Created attachment 52652 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D52652&action=3Dedit compiler configuration Line 1630 in libgcc/config/avr/lib1funcs.S defined r_cnt as __zero_reg__ and uses it as loop count, i.e. it sets it to a non-zero value. This is fine if the loop reaches its end, but causes chaos if there's an interrupt before the loop end. __zero_reg__ should never be set to a non-zero value! Looking through the file there seem to be a number of other places where __zero_reg__ is modified.=