internal/lz4block: Copy literals of <=48 bytes through XMM registers in amd64 decoder #161
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name old speed new speed delta UncompressPg1661-8 1.15GB/s ± 1% 1.19GB/s ± 1% +3.39% (p=0.000 n=10+10) UncompressDigits-8 1.89GB/s ± 0% 2.33GB/s ± 1% +23.46% (p=0.000 n=9+10) UncompressTwain-8 1.19GB/s ± 1% 1.23GB/s ± 0% +3.43% (p=0.000 n=10+10) UncompressRand-8 3.93GB/s ± 2% 3.96GB/s ± 1% ~ (p=0.105 n=10+10) The effect is most pronounced on Digits because 37.4% of its literals have lengths 17-48. In Twain and Pg1661, this is <4.1%. This is faster than copying 32 bytes. At 64 bytes, digits gets faster still whlie Twain and Pg1661 get slightly slower.
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Another optimization for the amd64 decoder, inspired by one of its comments:
The effect is most pronounced on Digits because 37.4% of its literals have lengths 17-48. In Twain and Pg1661, this is <4.1%.
This is faster than copying 32 bytes. At 64 bytes, digits gets faster still whlie Twain and Pg1661 get slightly slower.