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Re: [PATCH 1/3] Use generic vector computations in s_sincosf.h


Hi Carlos,

> I wonder what is the cost of using a tunable with defaults set differently by
> architecture?
>
> This way if a architectural licensee does something different for AArch64 that
> changes this back the other way they could tune it differently with a global
> env var setting?

I'm not sure how it would be useful as a tunable - the overhead is due to
extra scalar/vector conversion instructions that GCC inserts, so it is
not dependent on the micro architecture (and you'd use an ifunc if it was).

We can revisit this when GCC's handling of vectors has been improved.
However I think it's more interesting to go after the big performance gains
first, for example we can get a 50% speedup with an improved interface:
https://sourceware.org/ml/libc-alpha/2018-09/msg00185.html

Wilco

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