https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114331
--- Comment #14 from Jakub Jelinek <jakub at gcc dot gnu.org> --- (In reply to Aldy Hernandez from comment #13) > And yes Jakub, as you have noticed, BIT_IOR_EXPR, BIT_XOR_EXPR, and likely > other operators may need to be tweaked to take bitmasks into account. I > wouldn't be surprised if there's a lot of low hanging fruit in this space. I think next to BIT_AND_EXPR with const second operand in the reverse direction it certainly is BIT_IOR_EXPR with const second operand in the forward direction, that is another thing where some bits become unknown compared to the source bitmask. Whether it is also BIT_XOR_EXPR/BIT_NOT_EXPR, dunno right now, we'd need to play with testcases. Maybe it is also BIT_AND_EXPR with const second operand in the forward direction (and then BIT_IOR_EXPR with const second operand in the reverse direction and BIT_XOR_EXPR with const second operand and BIT_NOT_EXPR in both directions) which instead of making some bits unknown (i.e. oring some bits into mask) makes some bits known (i.e. removes them from the mask; for xor/not keeps mask as is but modifies value).
