[Bug tree-optimization/113849] New: wrong code with _BitInt() arithmetics at -O1

[Bug tree-optimization/113849] New: wrong code with _BitInt() arithmetics at -O1

[zsojka at seznam dot cz]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113849

            Bug ID: 113849
           Summary: wrong code with _BitInt() arithmetics at -O1
           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 57370
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=57370&action=edit
reduced testcase

This testcase was originally attached to PR113774, but this is still failed
after the fix.

Output:
$ x86_64-pc-linux-gnu-gcc -O1 testcase.c
$ ./a.out
Aborted

$ x86_64-pc-linux-gnu-gcc -v
Using built-in specs.
COLLECT_GCC=/repo/gcc-trunk/binary-latest-amd64/bin/x86_64-pc-linux-gnu-gcc
COLLECT_LTO_WRAPPER=/repo/gcc-trunk/binary-trunk-r14-8897-20240209102321-g0a329ecf113-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=c,c++
--enable-valgrind-annotations --disable-nls --enable-checking=yes,rtl,df,extra
--disable-bootstrap --with-cloog --with-ppl --with-isl
--build=x86_64-pc-linux-gnu --host=x86_64-pc-linux-gnu
--target=x86_64-pc-linux-gnu --with-ld=/usr/bin/x86_64-pc-linux-gnu-ld
--with-as=/usr/bin/x86_64-pc-linux-gnu-as --disable-libstdcxx-pch
--prefix=/repo/gcc-trunk//binary-trunk-r14-8897-20240209102321-g0a329ecf113-checking-yes-rtl-df-extra-nobootstrap-amd64
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 14.0.1 20240209 (experimental) (GCC)

[Bug tree-optimization/113849] wrong code with _BitInt() arithmetics at -O1

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113849

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2024-02-09

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed.

[Bug tree-optimization/113849] wrong code with _BitInt() arithmetics at -O1

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113849

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |jakub at gcc dot gnu.org
             Status|NEW                         |ASSIGNED

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 57399
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=57399&action=edit
gcc14-pr113849.patch

Untested fix.

[Bug tree-optimization/113849] wrong code with _BitInt() arithmetics at -O1

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113849

--- Comment #3 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:9511b91c56f08b319b4a407608f85c96029ce7ce

commit r14-8941-g9511b91c56f08b319b4a407608f85c96029ce7ce
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Mon Feb 12 20:46:04 2024 +0100

    lower-bitint: Fix handle_cast when used e.g. in comparisons of precisions
multiple of limb_prec [PR113849]

    handle_cast handles the simple way all narrowing large/huge bitint to
    large/huge bitint conversions and also such widening conversions if we can
    assume that the most significant limb is processed using constant index
    and both lhs and rhs have same number of limbs.
    But, the condition whether we can rely on the most significant limb
    being processed using constant index is incorrect.
    For m_upwards_2limb it was correct (m_upwards_2limb then is the number
    of limbs handled by the loop, so if lhs_type has larger precision than
    that, it is handled with constant index), similarly if m_var_msb is set
    (on left shifts), it is never handled with constant idx.  But in other
    cases, like right shifts or non-equality comparisons, or bitquery
operations
    which operate from most significant to least significant limb, all those
    can handle even the most significant limb in a loop when lhs_type has
    precision which is a multiple of limb_prec.

    So, the following patch punts on the optimization in that case and goes for
    the conditionals in the loop for that case.

    2024-02-12  Jakub Jelinek  <jakub@redhat.com>

            PR tree-optimization/113849
            * gimple-lower-bitint.cc (bitint_large_huge::handle_cast): Don't
use
            fast path for widening casts where !m_upwards_2limb and lhs_type
            has precision which is a multiple of limb_prec.

            * gcc.dg/torture/bitint-58.c: New test.

[Bug tree-optimization/113849] wrong code with _BitInt() arithmetics at -O1

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113849

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Should be fixed now.