gf_eq
succ = gf_eq(a, b);
out = gf_eq(a, b);
out &= gf_eq(a, b);
out &= ~gf_eq(p->z, ZERO);
nz = ~gf_eq(x1, ZERO);
return gf_eq(L0, ONE);
mask_t gf_eq(const gf x, const gf y);