> The lookup table is small enough to fit into 8 AVX2 registers Indeed. > so instead of hashing, you could use direct lookup However, I don’t think that part

> The lookup table is small enough to fit into 8 AVX2 registers Indeed. > so instead of hashing, you could use direct lookup However, I don’t think that part gonna work. See the code using that table: https://github.com/phoboslab/qoi/blob/master/qoi.h#L324-L328 https://github.com/phoboslab/qoi/blob/master/qoi.h#L324-L328 SIMD registers aren’t indexable (at least not on AMD64), the register needs to be known to the compiler. Lanes within each register aren’t indexable either. The insert and extract instructions are encoding lane index in the code. There’re workarounds for this one, like abusing vpshufb or vpermd, but with that amount of overhead I doubt SIMD will deliver any profit at all.