Hmmm. The one time I tried it (for a crypto miner), it ran about 60% the speed of gcc and clang (which were comparable; one was slightly ahead, I forget which

Hmmm. The one time I tried it (for a crypto miner), it ran about 60% the speed of gcc and clang (which were comparable; one was slightly ahead, I forget which but I think it was gcc). Granted, I may have gotten the flags wrong (there were a lot of them), but I turned all the ones that looked relevant.