Implement vertical convolutions using Neon USDOT instruction
Add additional AArch64 paths for vpx_convolve8_vert_neon and
vpx_convolve8_avg_vert_neon that use the Armv8.6-A USDOT (mixed-sign
dot-product) instruction. The USDOT instruction takes an 8-bit
unsigned operand vector and a signed 8-bit operand vector to produce
a signed 32-bit result. This is helpful because convolution filters
often have both positive and negative values, while the 8-bit pixel
channel data being filtered is all unsigned. As a result, the USDOT
convolution paths added here do not have to do the "transform the
pixel channel data to [-128, 128) and correct for it later" dance
that we have to do with the SDOT paths.
The USDOT instruction is optional from Armv8.2 to Armv8.5 but
mandatory from Armv8.6 onwards. The availability of the USDOT
instruction is indicated by the feature macro
__ARM_FEATURE_MATMUL_INT8. The SDOT paths are retained for use on
target CPUs that do not implement the USDOT instructions.
Change-Id: Ifbf467681dd53bb1d26e22359885e6edde3c5c72
2 files changed
