kc3-lang/libjpeg-turbo

2018-03-02T22:33:19

C/SSE2 optimization of encode_mcu_AC_refine() This commit adds C and SSE2 optimizations for the encode_mcu_AC_refine() function used in progressive Huffman encoding. The image used for testing can be retrieved from this page: https://blog.cloudflare.com/doubling-the-speed-of-jpegtran All timings done on `Intel(R) Core(TM) i7-4870HQ CPU @ 2.50GHz` clang version is `Apple LLVM version 9.0.0 (clang-900.0.39.2)` gcc-5 version is `gcc-5 (Homebrew GCC 5.5.0) 5.5.0` gcc-7 version is `gcc-7 (Homebrew GCC 7.2.0) 7.2.0` Here are the results in comparison to libjpeg-turbo@3c54642 using `time ./jpegtran -outfile /dev/null -progressive -optimise -copy none print_poster_0025.jpg` C clang x86_64: +7% gcc-5 x86_64: +30% gcc-7 x86_64: +33% clang i386: +0% gcc-5 i386: +24% gcc-7 i386: +23% SSE2 clang x86_64: +42% gcc-5 x86_64: +53% gcc-7 x86_64: +64% clang i386: +35% gcc-5 i386: +46% gcc-7 i386: +49% Discussion in libjpeg-turbo/libjpeg-turbo#46