[Bug tree-optimization/77980] Regression in GCC-7.0.0's optimizer.

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77980

--- Comment #1 from Marc Glisse <glisse at gcc dot gnu.org> ---
To simplify 1/n to 0, we would have to notice that n cannot be ±1 (the last bit
is zero since n is 2*x2), and it cannot be 0 either in that division. That
seems quite specialized, but rather easy to add to match.pd using
get_nonzero_bits if someone wants to write it... Is there anything more general
that can be done based on that?