https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64309
--- Comment #11 from Marc Glisse <glisse at gcc dot gnu.org> --- (In reply to Oleg Endo from comment #7) > (1 << n) & 6 != 0 -> n > 0 && n < 3 (not beneficial) We usually spell it (unsigned)n-1<2 (still not that great). (In reply to Marek Polacek from comment #8) > > > I don't think so. I tried to come up with a more general transformation > > > that would simplify ((CST << n) & CST) != 0, but I haven't found anything > > > > If both CST are (possibly different) powers of 2 it works. > > Yes, but I'm not sure if it's worth it (doing it for 1, 2, 4, 8, ... instead > of just for 1). I am not sure why 1 is so much more important than the others... > > ((c<<n)&c)==c also works. ((pow2<<p)&(pow2<<n))!=0. > > I don't see how's that a simplification. ((c<<n)&c)==c -> n==0 ((pow2<<p)&(pow2<<n))!=0 -> p==n
