`LLC` and `Clang` accept different flags:

[vchuravy]

llc uses a more restrictive set of cpu march, whereas clang sometimes support nicer for the user ones that then are mapped onto the llc. An example of this is:

-mcpu=power9 which is valid for clang, but llc expects pwr9 and this is what clang maps it to internally.

Some programming languages like Julia use the llc targets and not the clang ones.

So we could in archspec either map clang targets to llc or add llc as a separate compiler.

[alalazo]

I think adding llc as a separate compiler would be better since, if I recall correctly, target names for llc are not supported directly by clang.