This is mostly similar to the existing NV{12,21}ToARGBRow_SVE2 kernels
except reading the YUV components all from the same interleaved input
array. We load four-byte elements and then use TBL to de-interleave the
UV components.
Unlike the NV{12,21} cases we need to de-interleave bytes rather than
widened 16-bit elements. Since we need a TBL instruction already it
would ordinarily be possible to perform the zero-extension from bytes to
16-bit elements by setting the index for every other byte to be out of
range. Such an approach does not work in SVE since at a vector length of
2048 bits since all possible byte values (0-255) are valid indices into
the vector. We instead get around this by rewriting the I4XXTORGB_SVE
macro to perform widening multiplies, operating on the low byte of each
16-bit UV element instead of the full value and therefore eliminating
the need for a zero-extension.
Observed reductions in runtimes compared to the existing Neon code:
| UYVYToARGBRow | YUY2ToARGBRow
Cortex-A510 | -30.2% | -30.2%
Cortex-A720 | -4.8% | -4.7%
Cortex-X2 | -9.6% | -10.1%
Bug: libyuv:973
Change-Id: I841a049aba020d0517563d24d2f14f4d1221ebc6
Reviewed-on: https://chromium-review.googlesource.com/c/libyuv/libyuv/+/5622132
Reviewed-by: Frank Barchard <fbarchard@chromium.org>
367dd50755