[AArch64] Unroll HalfFloat{,1}Row_NEON

The existing C implementation compiled with a recent LLVM is
auto-vectorised and unrolled to process four vectors per loop iteration,
making the Neon implementation slower than the C implementation on
little cores. To avoid this, unroll the Neon implementation to also
process four vectors per iteration.

Reduction in cycle counts observed compared to the existing Neon
implementation:

            | HalfFloat1Row_NEON | HalfFloatRow_NEON
Cortex-A510 |             -37.1% |            -40.8%
Cortex-A520 |             -32.3% |            -37.4%
Cortex-A720 |               0.0% |            -10.6%
  Cortex-X2 |               0.0% |             -7.8%
  Cortex-X4 |              +0.3% |             -6.9%

Bug: b/42280945
Change-Id: I12b474c970fc4355d75ed924c4ca6169badda2bc
Reviewed-on: https://chromium-review.googlesource.com/c/libyuv/libyuv/+/5872805
Reviewed-by: Frank Barchard <fbarchard@chromium.org>
Reviewed-by: Justin Green <greenjustin@google.com>
3 files changed
tree: 7ac0170c9f89bffaf220a7f488e2349c88248893
  1. build_overrides/
  2. docs/
  3. include/
  4. infra/
  5. riscv_script/
  6. source/
  7. tools_libyuv/
  8. unit_test/
  9. util/
  10. .clang-format
  11. .gitignore
  12. .gn
  13. .vpython
  14. .vpython3
  15. Android.bp
  16. Android.mk
  17. AUTHORS
  18. BUILD.gn
  19. CM_linux_packages.cmake
  20. CMakeLists.txt
  21. codereview.settings
  22. DEPS
  23. DIR_METADATA
  24. download_vs_toolchain.py
  25. libyuv.gni
  26. libyuv.gyp
  27. libyuv.gypi
  28. LICENSE
  29. linux.mk
  30. OWNERS
  31. PATENTS
  32. PRESUBMIT.py
  33. public.mk
  34. pylintrc
  35. README.chromium
  36. README.md
  37. winarm.mk
README.md

libyuv is an open source project that includes YUV scaling and conversion functionality.

  • Scale YUV to prepare content for compression, with point, bilinear or box filter.
  • Convert to YUV from webcam formats for compression.
  • Convert to RGB formats for rendering/effects.
  • Rotate by 90/180/270 degrees to adjust for mobile devices in portrait mode.
  • Optimized for SSSE3/AVX2 on x86/x64.
  • Optimized for Neon/SVE2/SME on Arm.
  • Optimized for MSA on Mips.
  • Optimized for RVV on RISC-V.

Development

See Getting started for instructions on how to get started developing.

You can also browse the docs directory for more documentation.