[Bug tree-optimization/109959] `(a > 1) ? 0 : (a == 1)` is not optimized when spelled out at -O2+

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109959

--- Comment #12 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The trunk branch has been updated by Andrew Pinski <pinskia@gcc.gnu.org>:

https://gcc.gnu.org/g:b57bd27cb68fdbe5d9dcd571b1cb66f72b841290

commit r14-3036-gb57bd27cb68fdbe5d9dcd571b1cb66f72b841290
Author: Andrew Pinski <apinski@marvell.com>
Date:   Sun Aug 6 13:57:35 2023 -0700

    MATCH: [PR109959] `(uns <= 1) & uns` could be optimized to `uns == 1`

    I noticed while looking into some code generation of
bitmap_single_bit_set_p,
    that sometimes:
    ```
      if (uns > 1)
        return 0;
      return uns == 1;
    ```
    Would not optimize down to just:
    ```
    return uns == 1;
    ```

    In this case, VRP likes to change `a == 1` into `(bool)a` if
    a has a range of [0,1] due to `a <= 1` side of the branch.
    We might end up with this similar code even without VRP,
    in the case of builtin-sprintf-warn-23.c (and Wrestrict.c), we had:
    ```
    if (s < 0 || 1 < s)
      s = 0;
    ```
    Which is the same as `s = ((unsigned)s) <= 1 ? s : 0`;
    So we should be able to catch that also.

    This adds 2 patterns to catch `(uns <= 1) & uns` and
    `(uns > 1) ? 0 : uns` and convert those into:
    `(convert) uns == 1`.

    OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.

            PR tree-optimization/109959

    gcc/ChangeLog:

            * match.pd (`(a > 1) ? 0 : (cast)a`, `(a <= 1) & (cast)a`):
            New patterns.

    gcc/testsuite/ChangeLog:

            * gcc.dg/tree-ssa/builtin-sprintf-warn-23.c: Remove xfail.
            * c-c++-common/Wrestrict.c: Update test and remove some xfail.
            * gcc.dg/tree-ssa/cmpeq-1.c: New test.
            * gcc.dg/tree-ssa/cmpeq-2.c: New test.
            * gcc.dg/tree-ssa/cmpeq-3.c: New test.