GCC 8/9 vs. LLVM Clang 6/7 Compiler Benchmarks On AMD EPYC

With the FFTW benchmarks when using "-O3 -march=native" as the CFLAGS, the GCC performance came out much stronger than with the current LLVM Clang compiler.

At all of the optimization levels tested, GCC is currently performing much better than Clang with the AOBench renderer.

In many benchmarks the Clang performance continues to be on-par with GCC after years of playing catch up to the GNU Compiler Collection.

OpenMP workloads is one of the areas where GCC remains stronger than Clang with libomp.