kc3-lang/libjpeg-turbo

2018-03-22T11:36:43

C/SSE2 optimization of encode_mcu_AC_first() This commit adds C and SSE2 optimizations for the encode_mcu_AC_first() 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@293263c using `time ./jpegtran -outfile /dev/null -progressive -optimise -copy none print_poster_0025.jpg` C clang x86_64: +19% gcc-5 x86_64: +80% gcc-7 x86_64: +57% clang i386: +5% gcc-5 i386: +59% gcc-7 i386: +51% SSE2 clang x86_64: +79% gcc-5 x86_64: +158% gcc-7 x86_64: +122% clang i386: +71% gcc-5 i386: +134% gcc-7 i386: +135% Discussion in libjpeg-turbo/libjpeg-turbo#46