https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93504
--- Comment #4 from Marc Glisse <glisse at gcc dot gnu.org> ---
/* (x & ~m) | (y & m) -> ((x ^ y) & m) ^ x */
I guess several transformations like this one which match (unary m) could do
with a second version for the case where m is constant (and thus (unary m) is
already constant folded). That is, unless we come up with a trick to avoid that
duplication, like (untested)
(match (my_not @0)
(bit_not @0))
(match (my_not @0)
INTEGER_CST@0
(with { @0 = fold_unary (BIT_NOT_EXPR, TREE_TYPE(@0), @0); }
(if (true))))
although that's hackish, the commutative version is redundant, it builds a tree
unnecessarily, the conditions (single_use?) to make the transformation worth it
may be different, etc.
