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

[Joseph Myers]

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.

-- 
Joseph S. Myers
joseph@codesourcery.com