commit 4ad050b5ecc04925d2938df722c7b684e88647b7
author George Steed <george.steed@arm.com> Wed May 01 17:07:11 2024 +0100
committer Frank Barchard <fbarchard@chromium.org> Fri Jul 19 15:55:59 2024 +0000
tree 693312ce83a0836003e6f60bc2e068281e183581
parent b5f9d7cb76a1e31f1893df0d903a8a421f2fbba0

[AArch64] Unroll {I422,I422Alpha}ToARGBRow_SVE2

Since the UV components are duplicated in I422 we end up wasting half of
the vector bandwidth processing the same elements twice. By unrolling
the kernel to process two vectors of Y per iteration we can fill a whole
vector of U/V components.

Rather than packing RGBA components into pairs during the narrowing we
now just narrow into individual component vectors and use ST4B instead.
This by itself is slower on some micro-architectures like Cortex-A510
but the benefit from unrolling significantly outweights this.

            | I422AlphaToARGBRow_SVE2 | I422ToARGBRow_SVE2
Cortex-A510 |                  -46.2% |             -48.8%
Cortex-A720 |                  -20.8% |             -21.0%
  Cortex-X2 |                  -11.3% |              -7.5%
  Cortex-X4 |                  -15.4% |             -15.5%

Bug: libyuv:973
Change-Id: I69389c4279861f7a460ae0c28186f023c728c4e8
Reviewed-on: https://chromium-review.googlesource.com/c/libyuv/libyuv/+/5725173
Reviewed-by: Frank Barchard <fbarchard@chromium.org>