[Bug tree-optimization/112533] missed optimization (~A & C) == (~B & C) => (A & C) == (B & C)

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112533

--- Comment #6 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Richard Biener <[email protected]>:

https://gcc.gnu.org/g:9d59dcff40a4f39ee82f9c59a67f9466d7a8bc66

commit r17-3351-g9d59dcff40a4f39ee82f9c59a67f9466d7a8bc66
Author: Shivam Gupta <[email protected]>
Date:   Sat Aug 15 12:06:22 2026 +0530

    match.pd: Simplify (~A & 1) == (~B & 1) at -O1 [PR112533]

    At -O1, GCC lowers (~a & 1) == (~b & 1) into two different GIMPLE
    forms depending on whether the boolean values come from a function
    return boundary or an inline expression:

      1. Via function return (e.g. inlined is_even), GCC preserves the
         eq/ne form because the function boundary hides the internal
         structure from the gimplifier:
           ((a&1)==0) == ((b&1)==0)   outer node is eq/ne

      2. Via inline expression (directly written), GCC sees the full
         boolean expression tree at once and folds to bit_xor during
         gimplification:
           ((a&1)!=0) ^ ((b&1)==0)   outer node is bit_xor

    Add a generalized match.pd rule handling:
      1. ((x & c) == 0) OP ((y & c) == 0)
      2. ((x & c) != 0) OP ((y & c) == 0)

    for OP in { ==, !=, ^ } and pow2 masks.

    Fold these directly into the canonical xor-mask form:
      ((x ^ y) & c) == 0
      ((x ^ y) & c) != 0

    Bootstrapped and tested on aarch64-linux-gnu with
    RUNTESTFLAGS="tree-ssa.exp".

    Changes since v1:
    * v5: Add :s to the inner comparisons and bit_and expressions.
          Simplify the innersame check to compare icmp0 and icmp1
          directly.

    * v4: Removed the ((x & c) == 0) OP (y & c) simplify rule and
          mark the corresponding test case as XFAIL.

    * v3: Collapse both previous simplify rules into one generalized
          matcher covering all combinations of outer {eq, ne, bit_xor}
          and inner {eq, ne} comparisons.
          Add missing mixed-polarity test cases.

    * v2: Generalize mask from integer_onep to integer_pow2p.
          Combine both patterns into single one.
          Split test into bool-eq-evenness.c, bool-eq-bitxor.c,
          bool-eq-pow2.c.

            PR tree-optimization/112533

    gcc/ChangeLog:
            * match.pd: Canonicalize boolean comparisons of masked pow2
            bits into xor-mask tests.

    gcc/testsuite/ChangeLog:
            * gcc.dg/tree-ssa/bool-eq-bitxor.c: New test.
            * gcc.dg/tree-ssa/bool-eq-evenness.c: New test.
            * gcc.dg/tree-ssa/bool-eq-pow2.c: New test.

    Signed-off-by: Shivam Gupta <[email protected]>