GCC 9.0 Compiler Benchmarks Against GCC7/GCC8 At The End Of 2018
At least on this Core i9 7980XE HEDT system, going from GCC7 to GCC8 yielded more of a performance improvement than we're seeing in a number of tests in going from GCC8 to GCC9... Not too surprising though with the Skylake compiler support being quite mature.
One of the noticeable improvements with GCC9 was in SciMark2's FFT test, but the other SciMark2 cases didn't have such dramatic differences.
The x265 performance did have a minor pent up in performance with GCC 9.0.0.