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Re:86 GB/s bitpacking with ARM SIMD (single thread) by TinkersW on Sunday October 05, 2025 @01:08PM (#45483272)
8 bit is not absent in x86 SIMD, it is a slightly less covered than 32 & 16 bit, but you can fully implement all the common 8 bit ops and most are 1 instruction(with AVX2). There are even various horizontal ops on 8 bit values(avg, dot etc).

Also AVX512 is way more common than SVE2, all Zen4 & Zen5 support it.

Re:86 GB/s bitpacking with ARM SIMD (single thread) by dzaima on Sunday October 05, 2025 @01:59PM (#45483714)
More specifically, basically the only absent 8-bit ops that have 32-bit equivalents in AVX2 are shifts and multiplies. Shifts are quite annoying (though, with a uniform shift they can be emulated on AVX-512 via GFNI abuse in 1 instr), multiplies are rather rare (though note that there is vpmaddubsw for an 8-bit→16-bit multiply-add). There's even a case of the opposite - saturating add/sub exist for 8-bit and 16-bit ints, but not wider.
Re:86 GB/s bitpacking with ARM SIMD (single thread) by namibj on Sunday October 05, 2025 @06:38PM (#45485919)
GFNI is distinct from AVX-512; it was merely introduced in cores that also had AVX-512.