[Bug middle-end/99520] Failure to detect bswap pattern

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99520

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Bet handling PLUS_EXPR next to BIT_IOR_EXPR in find_bswap_or_nop_1
and pass_optimize_bswap::execute could do the trick.
Though, I guess for PLUS_EXPR one needs stronger tests in
perform_symbolic_merge.
Because for BIT_IOR_EXPR, it is perfectly fine if the same bytes are ored in
multiple times, but for PLUS_EXPR it obviously is not.
So
      masked1 = n1->n & mask;
      masked2 = n2->n & mask;
      if (masked1 && masked2 && masked1 != masked2)
        return NULL;
is good enough for BIT_IOR_EXPR, but PLUS_EXPR would need a
      if (masked1 && masked2)
        return NULL;
test.