From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id BDA7D3858402; Wed, 17 Nov 2021 20:54:19 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org BDA7D3858402 From: "pallansson at gmail dot com" To: gcc-bugs@gcc.gnu.org Subject: [Bug c/103308] New: gcc regression after version 8, simple double loop exiting early with optimizations Date: Wed, 17 Nov 2021 20:54:19 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: c X-Bugzilla-Version: 11.1.1 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: pallansson at gmail dot com 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 target_milestone 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: Wed, 17 Nov 2021 20:54:19 -0000 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103308 Bug ID: 103308 Summary: gcc regression after version 8, simple double loop exiting early with optimizations Product: gcc Version: 11.1.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c Assignee: unassigned at gcc dot gnu.org Reporter: pallansson at gmail dot com Target Milestone: --- Picked up from here: https://cboard.cprogramming.com/c-programming/180520-interesting-bug-gcc-9-= above.html I have tested gcc-9/10/11 as included in Ubuntu and they all give the same results, as well as builds from gcc.git of latest gcc-11 and gcc-12, specif= ic results from gcc 11.1.0 in Ubuntu 21.04 below: $ gcc-11 -Og -o el earlyloop.c $ ./el a=3D0, c=3D1 a=3D0, c=3D2 a=3D1, c=3D3 a=3D1, c=3D4 a=3D2, c=3D5 a=3D2, c=3D6 a=3D3, c=3D7 a=3D3, c=3D8 a=3D4, c=3D9 a=3D4, c=3D10 a=3D5, c=3D11 a=3D5, c=3D12 a=3D6, c=3D13 a=3D6, c=3D14 a=3D7, c=3D15 a=3D7, c=3D16 a=3D8, c=3D17 a=3D8, c=3D18 a=3D9, c=3D19 a=3D9, c=3D20 $ gcc-11 -O3 -o el earlyloop.c $ ./el a=3D0, c=3D1 a=3D0, c=3D2 a=3D1, c=3D3 $ gcc-11 -v Using built-in specs. COLLECT_GCC=3Dgcc-11 COLLECT_LTO_WRAPPER=3D/usr/lib/gcc/x86_64-linux-gnu/11/lto-wrapper OFFLOAD_TARGET_NAMES=3Dnvptx-none:amdgcn-amdhsa OFFLOAD_TARGET_DEFAULT=3D1 Target: x86_64-linux-gnu Configured with: ../src/configure -v --with-pkgversion=3D'Ubuntu 11.1.0-1ubuntu1~21.04' --with-bugurl=3Dfile:///usr/share/doc/gcc-11/README.= Bugs --enable-languages=3Dc,ada,c++,go,brig,d,fortran,objc,obj-c++,m2 --prefix= =3D/usr --with-gcc-major-version-only --program-suffix=3D-11 --program-prefix=3Dx86_64-linux-gnu- --enable-shared --enable-linker-build-= id --libexecdir=3D/usr/lib --without-included-gettext --enable-threads=3Dposix --libdir=3D/usr/lib --enable-nls --enable-bootstrap --enable-clocale=3Dgnu --enable-libstdcxx-debug --enable-libstdcxx-time=3Dyes --with-default-libstdcxx-abi=3Dnew --enable-gnu-unique-object --disable-vtable-verify --enable-plugin --enable-default-pie --with-system-= zlib --enable-libphobos-checking=3Drelease --with-target-system-zlib=3Dauto --enable-objc-gc=3Dauto --enable-multiarch --disable-werror --enable-cet --with-arch-32=3Di686 --with-abi=3Dm64 --with-multilib-list=3Dm32,m64,mx32 --enable-multilib --with-tune=3Dgeneric --enable-offload-targets=3Dnvptx-none=3D/build/gcc-11-RPS7jb/gcc-11-11.1.0/= debian/tmp-nvptx/usr,amdgcn-amdhsa=3D/build/gcc-11-RPS7jb/gcc-11-11.1.0/deb= ian/tmp-gcn/usr --without-cuda-driver --enable-checking=3Drelease --build=3Dx86_64-linux-gnu --host=3Dx86_64-linux-gnu --target=3Dx86_64-linux-gnu --with-build-config=3Dbootstrap-lto-lean --enable-link-serialization=3D2 Thread model: posix Supported LTO compression algorithms: zlib zstd gcc version 11.1.0 (Ubuntu 11.1.0-1ubuntu1~21.04)=