[Bug tree-optimization/126761] missing detection of umin(a,~c) with __builtin_add_overflow

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126761

--- Comment #1 from Drea Pinski <pinskia at gcc dot gnu.org> ---
I was going to say we could have a match pattern for:
  add_4 = .SAT_ADD (a_5(D), cst_6(D));
  _3 = add_4 - cst_6(D);

But we don't have a forwprop after widening_multiply.
So this might be more complex. There is an isel which might do some match and
simplify stuff but it does not yet.