[clang] [llvm] [aarch64][llvm] Allow AArch64 TLB maintenance instructions to be enabled via -march (PR #116707)

[David Green via cfe-commits]

davemgreen wrote:

> These instructions are being used in the hand-written assembly for a hypervisor. The hypervisor will check at runtime if the instructions are available on the current CPU before calling this code.

We try to coordinate between GCC and LLVM, to make sure we implement the same interface. Is there a reason you can't use `-march=armv8.7-a` as it works today, or add a `.arch armv8.7-a` directive? Otherwise we will need to check with GCC to make sure they are happy to implement the same features.

https://github.com/llvm/llvm-project/pull/116707