Re: [PATCH 7/14] [x86_64] Vector math functions (log and tests)

[Andrew Senkevich <andrew dot n dot senkevich at gmail dot com>]

2015-06-04 20:44 GMT+03:00 Joseph Myers <joseph@codesourcery.com>:
> On Thu, 4 Jun 2015, Andrew Senkevich wrote:
>
>> This patch adds vector implementations of log for x86_64 and tests.
>
> I see this patch adds e.g. both _ZGVbN2v_log and _ZGVbN2v___log_finite, as
> aliases.
>
> That's the sort of thing that needs specifically explaining in the patch
> write-up.  In general, it's a bad idea to add extra interfaces to any of
> glibc's shared libraries unless they actually have some sort of semantic
> difference (or unless the interfaces are required to be usable without
> including any headers) - and since all these vector functions are only for
> -ffast-math, I don't think there is any semantic difference in the _finite
> case.
>
> My guess is that this is something to do with interaction of the pragmas
> that cause these functions to be used and the asm redirection of e.g. log
> to __log_finite (for -ffinite-math-only, which is implied by -ffast-math).
> Now, I suppose you do want that redirection to be in effect for calls that
> don't get vectorized.  So I think you should try to work something out in
> the compiler context as a way to say "vector calls should have their names
> based on log not __log_finite, notwithstanding the redirection for scalar
> calls", so we can avoid adding redundant ABIs to libmvec that are never
> going to do anything different from the non-__*_finite ABIs.

Such aliases were added because GCC generates vector name based on
scalar one already containing _finite redirection.
May be stay only _ZGV*N*v___log_finite symbols?


--
WBR,
Andrew