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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/113421] New: wrong code with -O -fno-tree-fre
 and _BitInt() multiplication
Date: Tue, 16 Jan 2024 12:04:03 +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
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113421

            Bug ID: 113421
           Summary: wrong code with -O -fno-tree-fre and _BitInt()
                    multiplication
           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
  Target Milestone: ---
              Host: x86_64-pc-linux-gnu
            Target: x86_64-pc-linux-gnu

Created attachment 57101
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D57101&action=3Dedit
reduced testcase

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

On the asm level:
...
        mov     r9d, 1024       #,
        lea     r8, [rsp+16]    #,
        mov     ecx, 1024       #,
        mov     edx, OFFSET FLAT:g      #,
        mov     esi, 1024       #,
        mov     rdi, rdx        #,
        call    __mulbitint3    #
...

rdi =3D=3D rdx, overlapping the "ret" and "u" arguments of __mulbitint3

$ 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-r14-7274-20240116114934-=
g1251d3957de-checking-yes-rtl-df-extra-nobootstrap-amd64/bin/../libexec/gcc=
/x86_64-pc-linux-gnu/14.0.1/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-r14-7274-20240116114934-g1251d3957=
de-checking-yes-rtl-df-extra-nobootstrap-amd64
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 14.0.1 20240116 (experimental) (GCC)=