[Bug tree-optimization/99396] std::rotl and std::rotr do not invoke intrinsics, leading to serious performance issues

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99396

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|libstdc++                   |tree-optimization
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2021-03-05

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
    return std::rotr(v,((unsigned int)t)&63);
Fixes the problem ....
    int a = std::abs(t);
    a &= 63;
    return std::rotr(v,a);

Also improves the situtation.
I am thinking the std::rotr could be rewritten or we could optimize this at the
tree level into the almost the intrinsics.
Note I think I Might have gotten the above incorrect a little bit.