[Bug tree-optimization/55157] Missed VRP with != 0 and multiply

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55157

--- Comment #2 from Marc Glisse <glisse at gcc dot gnu.org> ---
Instead of looking at the definition, it could also look at get_nonzero_bits.
It would help when being a multiple of 16 is less obvious, but it wouldn't do
anything useful for t*15. It might be easier to optimize g<=4 to g==0 and let
existing optimizations do the rest.