http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56175
--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> 2013-02-11 14:38:37 UTC --- (In reply to comment #5) > This pattern is already recognized by simplify_bitwise_binary but only for > usual int type, i.e. if we change all short types to the ordinary int (or > unsigned) this simplification takes place (dump after 1st forwprop): > > <bb 4>: > x_8 = x_2(D) >> 1; > y_9 = y_4(D) >> 1; > _10 = x_8 & 1; > _11 = y_9 & 1; > _16 = x_8 ^ y_9; > z_12 = _16 & 1; > > i.e. the issue is redundant type conversions: > > <bb 3>: > x_7 = x_2(D) >> 1; > y_8 = y_4(D) >> 1; > _13 = x_7 & 1; > _9 = (signed char) _13; > _14 = y_8 & 1; > _10 = (signed char) _14; > _11 = _9 ^ _10; > > I assume that if we delete these redundant conversions the required > simplification will happen. Ah, well. The issue is that we transformed (unsigned char)y & 1 to (unsigned char)(y & 1).
