mirror of
https://github.com/facebook/zstd.git
synced 2025-03-07 09:26:03 +02:00
8957fef554
Add generic C versions of the fast decoding loops to serve architectures that don't have an assembly implementation. Also allow selecting the C decoding loop over the assembly decoding loop through a zstd decompression parameter `ZSTD_d_disableHuffmanAssembly`. I benchmarked on my Intel i9-9900K and my Macbook Air with an M1 processor. The benchmark command forces zstd to compress without any matches, using only literals compression, and measures only Huffman decompression speed: ``` zstd -b1e1 --compress-literals --zstd=tlen=131072 silesia.tar ``` The new fast decoding loops outperform the previous implementation uniformly, but don't beat the x86-64 assembly. Additionally, the fast C decoding loops suffer from the same stability problems that we've seen in the past, where the assembly version doesn't. So even though clang gets close to assembly on x86-64, it still has stability issues. | Arch | Function | Compiler | Default (MB/s) | Assembly (MB/s) | Fast (MB/s) | |---------|----------------|--------------|----------------|-----------------|-------------| | x86-64 | decompress 4X1 | gcc-12.2.0 | 1029.6 | 1308.1 | 1208.1 | | x86-64 | decompress 4X1 | clang-14.0.6 | 1019.3 | 1305.6 | 1276.3 | | x86-64 | decompress 4X2 | gcc-12.2.0 | 1348.5 | 1657.0 | 1374.1 | | x86-64 | decompress 4X2 | clang-14.0.6 | 1027.6 | 1659.9 | 1468.1 | | aarch64 | decompress 4X1 | clang-12.0.5 | 1081.0 | N/A | 1234.9 | | aarch64 | decompress 4X2 | clang-12.0.5 | 1270.0 | N/A | 1516.6 |