[clang] [llvm] [RISCV][FMV] Support target_clones (PR #85786)

[Philip Reames via llvm-commits]

https://github.com/preames requested changes to this pull request.

At a high level, I think this is a quite a ways from being ready to land.  There's both code style issues (mostly false generality), and missing bits of the user interface on the clang side.  I do not think this has any real serious chance of being ready to land in 19.x.

My suggestion would be that we do one of two things.
1) Acknowledge this is not getting in to 19.x, and switch the the glibc based resolver approach for 20.x.
2) Drastically cut the scope of this.  We won't get target_clones or target_variants, but we *could* possibly get builtin_cpu_supports.  That has a much smaller user interface scope, and while we would need to add the syntax checking bits there, there's none of the ordering and intersection problems.  

https://github.com/llvm/llvm-project/pull/85786