[PATCH] Aarch64: Add simd exp/expf functions

[Florian Weimer]

* Steve Ellcey:

> On Wed, 2019-03-06 at 20:16 +0100, Florian Weimer wrote:
>
>> * Steve Ellcey:
>> 
>> > On Wed, 2019-03-06 at 19:04 +0000, Szabolcs Nagy wrote:
>> > > 
>> > > this will need to detect support for
>> > > __attribute__((aarch64_vector_pcs))
>> > > (which will require gcc-9)
>> > 
>> > That seems easy enough to check for.
>> 
>> Can you add assembler trampolines, so that the compiler support
>> becomes optional, at a performance cost?
>
> Yuck.  I suppose this is possible, but I do not want to do it.
> The whole reason for vector functions (and for the new vector ABI)
> is performance so adding a slow path doesn't seem to me like it is
> worthwhile.

On the other hand, it could help to get libmvec out of the door more
quickly.  I think it's not ideal that if you use an older compiler,
you get only a subset of the glibc ABI.  We can get away with it here
because it affects an entire soname.  Still it might be difficult to
explain why applications are not portable.