For anyone doing HPC work and hasn't tried GFortran >=10, I highly suggest giving it a go. We switched to it for the arm64 improvements, but surprisingly also found a 20% speedup on the x86-64 target. My best guess is that it's a combination of IPO and autovec enhancements.
Profiling and -fopt-info should tell you why. (If you care about speed, use them anyway!) I'd be surprised if it's vectorization improvements, other than a specific bug fix.
