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  • This sort of analysis is great.

    Now why can't compilers do this sort of thing automatically?

    Almost any problem seems to be possible to speed up 1000x in AVX512+days of thought compared to the naive version written in a python loop. If we could automate that whole process for big codebases the performance gains could be huge.

    by londons_explore
  • Is the matrix for bit shifting upside down or am I momentarily making a really dumb mistake here? Edit: nvm I missed the footnote which clarifies that for whatever reason the instruction populates the matrix from bottom to top.
    by fc417fc802
  • Zigzag encodings are a common compression scheme used in the Parquet format. It is fun to speculate that these kind of tricks could be applied there in something so commonly under the hood of a lot of data processing and analytics
    by wood_spirit
  • While we could utilize zigzag encoding (i>>31) ^ (i<<1) to convert SLEB128-encoded type/addend to use ULEB128 instead, the generate code is inferior to or on par with SLEB128 for one-byte encodings on x86, AArch64, and RISC-V. Haven't tried wider values - but zigzag encoding is likely slower as well

    // One-byte case for SLEB128 int64_t from_signext(uint64_t v) { return v < 64 ? v - 128 : v; }

    // One-byte case for ULEB128 with zig-zag encoding int64_t from_zigzag(uint64_t z) { return (z >> 1) ^ -(z & 1); }

    by MaskRay
  • Worth mentioning that MeshOptimizer (https://github.com/zeux/meshoptimizer) has become one of a handful 'hidden champion' pillar libraries that probably carries half of the gaming industry.

    Basically the curl of asset pipelines ;)

    https://github.com/zeux/meshoptimizer/discussions/986

    by flohofwoe

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