GCC 12 Compiler Optimization Tuning With The AMD Ryzen Threadripper 3990X
For most users, "-O3 -march=native -flto" is likely as aggressive as you'll want to get without risking potentially unsafe math or the increased likelihood of possible issues creeping up.
These results are largely the same comparatively as what we've seen out of prior GCC compiler optimization comparisons, but here are the fresh results for those interested.