Back in February for LLVM Clang 9.0 was the initial AMD Zen 2 “znver2” enablement, but like the GCC support at the time it was the very basics. With time GCC picked up Zen 2 scheduler improvements and other work while sadly in the case of LLVM the improvements are still pending…

Source: Phoronix – AMD Zen 2 Improvements For LLVM Have Been Held Up For Months By Code Review