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From: "zsojka at seznam dot cz" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/113334] New: wrong code with _BitInt() shift
 at -O0
Date: Thu, 11 Jan 2024 12:26:53 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 14.0
X-Bugzilla-Keywords: wrong-code
X-Bugzilla-Severity: normal
X-Bugzilla-Who: zsojka at seznam dot cz
X-Bugzilla-Status: UNCONFIRMED
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X-Bugzilla-Priority: P3
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113334

            Bug ID: 113334
           Summary: wrong code with _BitInt() shift at -O0
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zsojka at seznam dot cz
                CC: jakub at gcc dot gnu.org
  Target Milestone: ---
              Host: x86_64-pc-linux-gnu
            Target: x86_64-pc-linux-gnu

Created attachment 57040
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D57040&action=3Dedit
reduced testcase

I cannot tell for sure that the code is defined, but I don't see anything
breaking pre-C23 rules, if applied to _BitInt().

Output:
$ x86_64-pc-linux-gnu-gcc testcase.c
$ ./a.out=20
Aborted

It works fine on -O1 and above.

$ x86_64-pc-linux-gnu-gcc -v
Using built-in specs.
COLLECT_GCC=3D/repo/gcc-trunk/binary-latest-amd64/bin/x86_64-pc-linux-gnu-g=
cc
COLLECT_LTO_WRAPPER=3D/repo/gcc-trunk/binary-trunk-r14-7127-20240110200826-=
g2105c49bbe8-checking-yes-rtl-df-extra-nobootstrap-amd64/bin/../libexec/gcc=
/x86_64-pc-linux-gnu/14.0.0/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-r14-7127-20240110200826-g2105c49bb=
e8-checking-yes-rtl-df-extra-nobootstrap-amd64
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 14.0.0 20240111 (experimental) (GCC)=