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x86intelsimdcrcavx2

256 bit CRC calculation on AVX2

64 bit CRC function exists on Intel SSE4.2 intrinsics. 

unsigned __int64 _mm_crc32_u64 (unsigned __int64 crc, unsigned __int64 v)

However I can't find 256 bit version of CRC calculation on AVX2 intrinsics. I'm using 256 bit variables (__m256i) on my program, so I want to calculate crc (or hash) over 256 bits. How can I do this operation with Intel AVX2 ?

Solution

  • _mm_crc32_u64 is not a SIMD intrinsic, even though it's notionally part of SSE4.2 - it is just a normal scalar instruction which operates on 64 bit values. So it makes no sense to talk about 128 bit or 256 bit SIMD versions - you just need to apply it in a loop to an array of unsigned 64 bit values.

    See this answer for a fuller explanation of the various x86 CRC32 instructions and intrinsics.