I spent a lot of time on those benchmarks. I think my conclusion is just that because WASM isn't a register-machine architecture, you basically have to implement a register allocator to be really fast. wasmtime uses a complex allocator to great success. wasm3 has done it too, but it's just a basic one and it won't be able to compete with GCC or Clang. I could be wrong here, but what else is there? During my testing, it was never in question if libriscv was faster.

I used my usual benchmarks: STREAM (memory) and CoreMark (CPU).