[RFC PATCH] aarch64: improve memset

[Richard Henderson <rth at twiddle dot net>]

The major idea here is to use IFUNC to check the zva line size once, and use
that to select different entry points.  This saves 3 branches during startup,
and allows significantly more flexibility.

Also, I've cribbed several of the unaligned store ideas that Ondrej has done
with the x86 versions.

I've done some performance testing using cachebench, which suggests that the
unrolled memset_zva_64 path is 1.5x faster than the current memset at 1024
bytes and above.  The non-zva path appears to be largely unchanged.

I'd like to use some of Ondrej's benchmarks+data, but I couldn't locate them in
a quick search of the mailing list.  Pointers?

Comments?


r~

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