[llvm] [llvm-exegesis][AArch64] Check for PAC keys before disabling them (PR #138643)

[Anatoly Trosinenko via llvm-commits]

https://github.com/atrosinenko commented:

Thank you for the updates! Except for tiny comments here and there, the code looks good to me.

I tested it in QEMU with three different CPU models (no PAuth, PAuth without FPAC, PAuth with FPAC), and it behaves as expected (notably, when the simulated CPU is set to support PAuth with FPAC, when I ask llvm-exegesis to actually execute the snippets, they are executed successfully by default and crash on SIGILL when I pass `--aarch64-disable-pac-control` - exactly as expected).

https://github.com/llvm/llvm-project/pull/138643