[Bug tree-optimization/124667] Optimize load/store IOR|AND branch mispredict (former bitmap_set_bit from GCC benchmark)

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124667

--- Comment #5 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Daniel Barboza <[email protected]>:

https://gcc.gnu.org/g:656bb1d9e9637028f917310e6c7688a0f1e99758

commit r17-3334-g656bb1d9e9637028f917310e6c7688a0f1e99758
Author: Daniel Barboza <[email protected]>
Date:   Tue Aug 11 08:20:40 2026 -0300

    match.pd: turn more conditional bit_iors unconditional [PR124667]

    Add patterns to handle the case where we're checking if a bit is set and
    setting it in case it's not.  Similar to the work done in PR64567 but in
    this case the bit is a result of a 1 << val lshift:

    (A & BIT) EQ 0 ? A | BIT : A , BIT = 1 << val => A | BIT
    (A & BIT) NE 0 ? A : A | BIT , BIT = 1 << val => A | BIT

    Following Andrea's suggestion we're also handling the variants that
    results in just 'A' if we switch the conditionals:

    (A & BIT) EQ 0 ? A | BIT : A , BIT = 1 << val => A | BIT
    (A & BIT) NE 0 ? A | BIT : A , BIT = 1 << val => A

    (A & BIT) NE 0 ? A : A | BIT , BIT = 1 << val => A | BIT
    (A & BIT) EQ 0 ? A : A | BIT , BIT = 1 << val => A

    We're also adding cases where a full bitmask is tested, i.e.:

    (A & MASK) EQ MASK ? A : A | MASK => A | MASK
    (A & MASK) NE MASK ? A : A | MASK => A

    (A & MASK) NE MASK ? A | MASK : A => A | MASK
    (A & MASK) EQ MASK ? A | MASK : A => A

    Note that for these simplifications we're not limited to a bit/pow2
    value like the zero comparisons, which don't work with multiple bits
    because there's no guarantees to preserve the 'non-zero' cases. E.g.:
    "(A & 0xF) == 0 ? A | 0xF : A" can't be simplified to just "A | 0xF"
    because there's a whole range of A lower bits (1,2...E) that would be
    turned to 0xF in the simplification - bits that would be preserved in
    the original pattern. This is the same scenario discussed before in
    PR64567.

    Bootstrapped and regression tested in x86_64, aarch64 and riscv64.

            PR tree-optimization/124667

    gcc/ChangeLog:

            * match.pd(`(A & BIT) EQ|NE 0 ? A | BIT : A`): New
            pattern.
            (`(A & BIT) EQ|NE 0 ? A : A | BIT`): New pattern.
            (`(A & MASK) EQ|NE MASK ? A : A | MASK`): New pattern.
            (`(A & MASK) EQ|NE MASK ? A | MASK : A`): New pattern.
            (`A | (((A >> N) & 1) << N)`): New pattern.

    gcc/testsuite/ChangeLog:

            * gcc.dg/tree-ssa/pr124667-2.c: New test.
            * gcc.dg/tree-ssa/pr124667.c: New test.