If you read the discussions to end, you will notice many objections to the benchmark that you have posted here. Even I have objections. -O3 is not the end of all possible optimizations in C and Fortran.
https://benchmarksgame-team.pages.debian.net/benchmarksgame/...
https://drmeister.wordpress.com/2015/07/30/timing-data-compa...
https://groups.google.com/forum/?_escaped_fragment_=topic/co...