GLIBC libmvec status

[GT]

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Thursday, February 27, 2020 9:52 AM, Jakub Jelinek <jakub@redhat.com> wrote:

> On Thu, Feb 27, 2020 at 08:47:19AM -0600, Bill Schmidt wrote:
>
> > But is this actually a good idea? It seems to me this will generate lousy
> > code in the absence of hardware support. Won't we be better off warning and
> > ignoring the directive, leaving the code in scalar form?
>
> Depends on the exact code, I think sometimes it will be just fine and will
> allow vectorizing something that really couldn't be otherwise.
> Isn't it better to leave it for the user to decide?
> They can always ask for it not to be generated (add notinbranch) if it isn't
> worthwhile.
>

I'm trying to understand what the x86_64 implementation does w.r.t. masked versions
of user defined functions. I haven't found any test under directory testsuite which verifies
that compiler-generated versions (from inbranch being specified) produce expected
results.

Which raises the question: what use-case motivated allowing the compiler
to auto-vectorize user defined functions? From having manually created vector
versions of sin, cos and other libmvec functions, I'm wondering how GCC is able to
autovectorize a non-trivial user defined function.

Any pointers to relevant tests and documentation will be really appreciated.

Thanks.
Bert.