For icmp pred (and (sh X, Y), C), 0

When C is signbit, expect to fold (X << Y) & signbit ==/!= 0 into (X << Y) >=/< 0, rather than (X & (signbit >> Y)) != 0. When C+1 is power of 2, expect to fold (X << Y) & ~C ==/!= 0 into (X << Y) </>= C+1, rather than (X & (~C >> Y)) == 0. For icmp pred (and X, (sh signbit, Y)), 0 Expect to fold (X & (signbit l>> Y)) ==/!= 0 into (X << Y) >=/< 0 Expect to fold (X & (signbit << Y)) ==/!= 0 into (X l>> Y) >=/< 0