The existing Neon code only makes use of 64-bit vectors throughout which
limits the performance on larger cores. To avoid this, swap the Neon
code from a Wx8 implementation to a Wx16 implementation and process
blocks of 16 full vectors at a time.
The original code also handled widths that were not exact multiples of
16, however this should already be handled by the "any" kernel so it is
removed.
Finally, avoid duplicating the TransposeWx16_C fallback kernel
definition in all architectures that need it, and just put it once in
rotate_common.cc instead.
Observed speedups for TransposePlane across a range of
micro-architectures:
Cortex-A53: -40.0%
Cortex-A55: -20.7%
Cortex-A57: -43.9%
Cortex-A510: -43.5%
Cortex-A520: -43.9%
Cortex-A720: -31.1%
Cortex-X2: -38.3%
Cortex-X4: -43.6%
Change-Id: Ic7c4d5f24eb27091d743ddc00cd95ef178b6984e
Reviewed-on: https://chromium-review.googlesource.com/c/libyuv/libyuv/+/5545459
Reviewed-by: Frank Barchard <fbarchard@chromium.org>
