From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 779D239B5C3A; Thu, 10 Jun 2021 21:13:24 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 779D239B5C3A From: "zsojka at seznam dot cz" To: gcc-bugs@gcc.gnu.org Subject: [Bug target/101023] New: [11/12 Regression] wrong code with -mstackrealign Date: Thu, 10 Jun 2021 21:13:24 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: target X-Bugzilla-Version: 12.0 X-Bugzilla-Keywords: wrong-code X-Bugzilla-Severity: normal X-Bugzilla-Who: zsojka at seznam dot cz 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 keywords bug_severity priority component assigned_to reporter target_milestone cf_gcchost cf_gcctarget 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: Thu, 10 Jun 2021 21:13:24 -0000 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101023 Bug ID: 101023 Summary: [11/12 Regression] wrong code with -mstackrealign Product: gcc Version: 12.0 Status: UNCONFIRMED Keywords: wrong-code Severity: normal Priority: P3 Component: target Assignee: unassigned at gcc dot gnu.org Reporter: zsojka at seznam dot cz Target Milestone: --- Host: x86_64-pc-linux-gnu Target: x86_64-pc-linux-gnu Created attachment 50981 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D50981&action=3Dedit auto-reduced testcase (from OpenTTD sources) Compiler output: $ x86_64-pc-linux-gnu-g++ -O2 -mtune=3Dopteron -mstackrealign --param=3Dhot-bb-frequency-fraction=3D1 testcase.C -S The offending code is: .L8: pushq %rbp .cfi_def_cfa_offset 16 .cfi_offset 6, -16 movq %rsp, %rbp .cfi_def_cfa_register 6 movq %r12, -8(%rbp) pushq %rax the "push" overwrites r12 stored just one instruction above; when returning: movq -8(%rbp), %r12 xorl %eax, %eax leave .cfi_def_cfa 7, 8 ret the wrong data is restored to r12 I wasn't able yet to generate an executable testcase, but I can try to if needed. (it shouldn't be that hard, just r12 needs to be used by the caller during the call) $ x86_64-pc-linux-gnu-g++ -v Using built-in specs. COLLECT_GCC=3D/repo/gcc-trunk/binary-latest-amd64/bin/x86_64-pc-linux-gnu-g= ++ COLLECT_LTO_WRAPPER=3D/repo/gcc-trunk/binary-trunk-r12-1366-20210610095751-= g6fcba9ef23e-checking-yes-rtl-df-extra-nobootstrap-amd64/bin/../libexec/gcc= /x86_64-pc-linux-gnu/12.0.0/lto-wrapper Target: x86_64-pc-linux-gnu Configured with: /repo/gcc-trunk//configure --enable-languages=3Dc,c++ --enable-valgrind-annotations --disable-nls --enable-checking=3Dyes,rtl,df,= extra --disable-bootstrap --with-cloog --with-ppl --with-isl --build=3Dx86_64-pc-linux-gnu --host=3Dx86_64-pc-linux-gnu --target=3Dx86_64-pc-linux-gnu --with-ld=3D/usr/bin/x86_64-pc-linux-gnu-ld --with-as=3D/usr/bin/x86_64-pc-linux-gnu-as --disable-libstdcxx-pch --prefix=3D/repo/gcc-trunk//binary-trunk-r12-1366-20210610095751-g6fcba9ef2= 3e-checking-yes-rtl-df-extra-nobootstrap-amd64 Thread model: posix Supported LTO compression algorithms: zlib zstd gcc version 12.0.0 20210610 (experimental) (GCC)=