[clang] [llvm] [CodeGen][AArch64][FMV] PAC the stub_helper's frame on arm64e (PR #84704)

[Daniil Kovalev via cfe-commits]

kovdan01 wrote:

> Can the triple checks be generalized to checking about pauth-enabled subtarget feature? This way everything would work for ELF platforms eventually.

@asl Since I'm not sure how particularly ifuncs should be handled, here are two answers for two different cases.

If we need just to check that pauth target feature is enabled, we can use `TM.getTargetFeatureString()` and see if it contains `+pauth`.

If the ifunc-related behavior is dependent on `-fptrauth-calls` (implicitly enabled on apple arm64e) and should not be enabled when, say, only `-fptrauth-returns` is used (in both cases the target feature string contains `+pauth`), on ELF we can add a check against (platform,version) tuple defining the ABI after #85236 is merged.

https://github.com/llvm/llvm-project/pull/84704