ffmpeg (without any libs) compiled by GCC 7 from snapshot 2017-04-14:
www.msystem.waw.pl/x265/ffmpeg-2017-04-14.7z
The ffmpeg2.exe is the same with '-O2' optimize option instead of default '-O3 -fno-tree-vectorize'. For my i5 3450S this ffmpeg2.exe is slightly faster.
It looks like ffmpeg is faster in decoding HEVC than one month before.