Re: Did clang 14 lose some intrinsics support?

From: Warner Losh <imp_at_bsdimp.com>
Date: Mon, 26 Sep 2022 14:20:15 UTC 
On Mon, Sep 26, 2022, 7:54 AM Lev Serebryakov <lev@freebsd.org> wrote:

> On 26.09.2022 13:03, Dimitry Andric wrote:
>
> > Sure, but if you are compiling without -mavx, why would you want the AVX
> > intrinsics? You cannot use AVX intrinsics anyway, if AVX is not enabled.
>    Because autovectorization (generation of SSE or AVX instructions by
> compiler itself, without intrinsics) can pessimize code.
>
>    Sometimes it is valuable to know exactly where AVX is used. I don't
> have examples on hands, but I've seen situations, when autovectorized code
> was much slower than scalar code.
>

The detection method that dim@ outline will work just fine for the
autodetect script. It just replaces the internal, charging undocumented
names for standard ones.

How you later compile individual bits of code is orthogonal.

Warner

>