[PATCH] aarch64: Fix and improve SVE pow(f) special cases.

[Wilco Dijkstra]

Hi Pierre,

...
> Throughput gain of about 5-10% on V1 for large values and 25% for subnormal `x`.

LGTM - committed.

Reviewed-by: Wilco Dijkstra  <Wilco.Dijkstra@arm.com>

Cheers,
Wilco