[RFC] How to add vector math functions to Glibc

[Carlos O'Donell]

On 09/26/2014 11:03 AM, H.J. Lu wrote:
> Put it in GLIBC means that GCC 5.0 may not support vector
> math, depending on the build or target GLIBC.  It is not a good
> GCC user experience.

The same goes for all the other C11 and C++11 features we
coordinate with glibc? I don't see how this has anything to do
with a "user experience." The distribution maintainers need to
make sure glibc is up to date, and gcc's required features are
present. This is always how it works.

> That is true that programmers who want to use vector math
> directly need to install GCC 5.0.  That is one reason I am
> asking who is the main user of vector math.

That's a serious upgrade for many users.

While backporting libmvec.so is pretty simple, and allows
the feature to be present for immediate use directly by a
developer, and later to be used when they are ready to
upgrade to gcc 5.0.

I think this chioce may actually be larger than just Intel.

For example IBM, and particularly their Power vector math
functions were explained to me as being callable directly
by developers. Thus Power might want libmvec.so in glibc?

I still believe that developers will want to call these
by hand if possible for code that is hand-optimized.

That IMO calls out for this to be libmvec.so in glibc.

Not to mention that gcc has no math testing infrastructure
and glibc does. We can immediately put all of this test
infrastructure to play for libmvec.so.

Cheers,
Carlos.