libyuv/docs/environment_variables.md
Frank Barchard 700f153cb8 [libyuv] Add Qualcomm Hexagon HVX SIMD support
Implement Qualcomm Hexagon Vector Extensions (HVX) 128-byte SIMD
optimizations and runtime CPU detection for Hexagon DSP targets:
- CPU detection: Add kCpuHasHexagon and kCpuHasHVX flags,
  LIBYUV_DISABLE_HVX environment variable support, and Hexagon
  unit_test mmap/munmap shims.
- Rotate/Transpose (rotate_hvx.cc): Implement TransposeWxH_HVX,
  TransposeUVWxH_HVX, TransposeWxH_16_HVX, and TransposeWxH_32_HVX
  using power-of-2 vdeal/vshuff butterfly networks.
- Compare (compare_hvx.cc): Implement HammingDistance_HVX,
  SumSquareError_HVX, HashDjb2_HVX, and Ssim4x4Row_HVX.
- Scale (scale_hvx.cc): Implement 16 scale row kernels including
  ScaleAddRow_HVX, ScaleRowDown2*_HVX (8-bit and 16-bit),
  ScaleRowDown4*_HVX, ScaleARGBRowDown2*_HVX, and
  ScaleUVRowDown2*_HVX.
- Row functions (row_hvx.cc): Implement 58 row kernels covering
  copy/set/mirror, split/merge, 8/16-bit conversions, YUV-to-ARGB,
  ARGB-to-YUV, ARGB channel swizzles, blend, attenuate, and
  interpolate using hardware-predicated partial loads/stores.

R=rrwinterton@gmail.com

Bug: None
Test: libyuv_unittest on Hexagon v81 simulator and Snapdragon 8 Elite
Change-Id: Ib6713de51f6246d95e58c95e629ff03f18e3b91e
Reviewed-on: https://chromium-review.googlesource.com/c/libyuv/libyuv/+/8604586
Reviewed-by: richard winterton <rrwinterton@gmail.com>
2026-10-19 14:16:18 -07:00

1.7 KiB

Introduction

For test purposes, environment variables can be set to control libyuv behavior. These should only be used for testing, to narrow down bugs or to test performance.

CPU

By default the cpu is detected and the most advanced form of SIMD is used. But you can disable instruction sets selectively, or completely, falling back on C code. Set the variable to 1 to disable the specified instruction set.

All CPUs

LIBYUV_DISABLE_ASM

Intel CPUs

LIBYUV_DISABLE_X86
LIBYUV_DISABLE_SSE2
LIBYUV_DISABLE_SSSE3
LIBYUV_DISABLE_SSE41
LIBYUV_DISABLE_SSE42
LIBYUV_DISABLE_AVX
LIBYUV_DISABLE_AVX2
LIBYUV_DISABLE_ERMS
LIBYUV_DISABLE_FMA3
LIBYUV_DISABLE_F16C
LIBYUV_DISABLE_AVX512BW
LIBYUV_DISABLE_AVX512VL
LIBYUV_DISABLE_AVX512VNNI
LIBYUV_DISABLE_AVX512VBMI
LIBYUV_DISABLE_AVX512VBMI2
LIBYUV_DISABLE_AVX512VBITALG
LIBYUV_DISABLE_AVX10
LIBYUV_DISABLE_AVX10_2
LIBYUV_DISABLE_AVXVNNI
LIBYUV_DISABLE_AVXVNNIINT8
LIBYUV_DISABLE_AMXINT8

Arm CPUs

LIBYUV_DISABLE_NEON
LIBYUV_DISABLE_NEON_DOTPROD
LIBYUV_DISABLE_NEON_I8MM
LIBYUV_DISABLE_SVE
LIBYUV_DISABLE_SVE2
LIBYUV_DISABLE_SME

LOONGARCH CPUs

LIBYUV_DISABLE_LSX
LIBYUV_DISABLE_LASX

RISCV CPUs

LIBYUV_DISABLE_RVV

Hexagon CPUs

LIBYUV_DISABLE_HVX

Test Width/Height/Repeat

The unittests default to a small image (128x72) to run fast. This can be set by environment variable to test a specific resolutions. You can also repeat the test a specified number of iterations, allowing benchmarking and profiling.

set LIBYUV_WIDTH=1280
set LIBYUV_HEIGHT=720
set LIBYUV_REPEAT=999
set LIBYUV_FLAGS=-1
set LIBYUV_CPU_INFO=-1