llc: Unknown command line argument '-debug-only=isel'

-debug-only only works on builds with assertions enabled. Your version string says optimized build and doesn’t mention assertions.

I believe Crag answered your problem. As for the command line option, usually you can use -help-hidden to list developers’ option, -debug-only is one example.

陳韋任,您好,非常感谢您的回复 :slight_smile: 欢迎再来hellogcc分享!

Thanks for your hint! I will try -DLLVM_ENABLE_ASSERTIONS=ON build option.