[clang] [compiler-rt] [llvm] [FMV][AArch64] Add feature CSSC and detect on linux platform. (PR #132727)

[Alexandros Lamprineas via llvm-commits]

labrinea wrote:

> The place to look for feature tests on Apple platforms is here: https://github.com/apple-oss-distributions/xnu/blob/main/osfmk/arm/cpu_capabilities_public.h.

I am not seeing a capability bit for this feature. Does this mean it cannot be supported yet?

https://github.com/llvm/llvm-project/pull/132727