Changes:
* Improved CRC-32 performance on recent x86 CPUs by adding
VPCLMULQDQ-accelerated implementations using 256-bit and 512-bit vectors.
* Improved Adler-32 performance on recent x86 CPUs by adding
VNNI-accelerated implementations using 256-bit and 512-bit vectors.
* Improved CRC-32 and Adler-32 performance on short inputs.
* Optimized the portable implementation of Adler-32.
* Added some basic optimizations for RISC-V.
* Dropped support for gcc versions older than v4.9 (released in 2014) and
clang versions older than v3.9 (released in 2016).
* Dropped support for CRC-32 acceleration on 32-bit ARM using the ARMv8 pmull or crc32 instructions.
This code only worked on CPUs that also have a 64-bit mode, and it was
already disabled on many compiler versions due to compiler limitations.
CRC-32 acceleration remains fully supported on 64-bit ARM.
Signed-off-by: Robert Marko <robimarko@gmail.com>
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