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From: "zsojka at seznam dot cz" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/112672] New: [14 Regression] wrong code with
 __builtin_parityl() at -O and above on x86_64
Date: Wed, 22 Nov 2023 17:04:24 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: target
X-Bugzilla-Version: 14.0
X-Bugzilla-Keywords: wrong-code
X-Bugzilla-Severity: normal
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D112672

            Bug ID: 112672
           Summary: [14 Regression] wrong code with __builtin_parityl() at
                    -O and above on x86_64
           Product: gcc
           Version: 14.0
            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 56666
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D56666&action=3Dedit
reduced testcase

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

$ 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-r14-5761-20231122145100-=
ge9b39df9333-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-r14-5761-20231122145100-ge9b39df93=
33-checking-yes-rtl-df-extra-nobootstrap-amd64
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 14.0.0 20231122 (experimental) (GCC)=20

At the asm output, the problem is obvious:

main:
# testcase.c:8:   u *=3D g;
        movzx   eax, WORD PTR g[rip]    # tmp110, g
        sal     eax, 2  # u,
# testcase.c:9:   return u + __builtin_parityl (u);
        xor     al, ah  # u <=3D=3D THIS OVERWRITES "u" in eax
        setnp   dl      #, tmp105
        movzx   edx, dl # tmp105, tmp105
# testcase.c:9:   return u + __builtin_parityl (u);
        add     eax, edx        # tmp107, tmp105 <=3D=3D THIS READ "u", but=
 it has
been lost
# testcase.c:16:   if (x !=3D 4 * 254 + 1)
        cmp     ax, 1017        # tmp107,
        jne     .L6     #,
# testcase.c:19: }
        mov     eax, 0  #,
        ret=