------- Comment #22 from aoliva at gcc dot gnu dot org 2008-01-14 19:56 ------- Both are cases in which the absence of bit-field reduction *on widening conversions* causes the problem.
I realize the absence of such reductions can be harmful in other cases as well, e.g. division and right-shifts. But for most cases, modulo semantics guarantees the correct results as long as we stick to the narrower type. However, when modulo semantics is required, reduction must take place, e.g. for compare operations that don't disregard the bits that are not in the type's implied mask. I believe the module semantics is the reasoning behind the no-reduction policy. But I do see that we fail to implement it properly, and I don't know whether it is the front-end's responsibility to provide the missing bits explicitly, or the middle end to cover for what the front end might be assuming the middle end will provide. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33887
