[Bug target/81616] Update -mtune=generic for the current Intel and AMD processors

[andrewm.roberts at sky dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81616

--- Comment #17 from Andrew Roberts <andrewm.roberts at sky dot com> ---
The general consensus in userland is that the znver1 optimization is much worse
than 0.5%, or even 2% off. Most people are using -march=haswell if they care
about performance.

Just taking one part of one of my apps I see a 5% difference with
-march=haswell vs -march=znver1, and this is just general code (loading GL
extensions). 

The trick is to remove system dependencies from things I could benchmark. If
there are no recommendations, I'll come up with some tests myself for various
workloads, and try across various march/tune combos.

I'll also look at some other real world benchmarks that are available online.