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

[Anatoly Trosinenko via llvm-commits]

================
@@ -32,6 +39,62 @@
 namespace llvm {
 namespace exegesis {
 
+static cl::opt<bool> AArch64DisablePacControl(
+    "aarch64-keep-pac-keys",
+    cl::desc("Disable PAC key control at runtime for benchmarking. Use this if "
+             "llvm-exegesis crashes or instruction timings are affected."),
+    cl::init(false));
+
+static bool isPointerAuth(unsigned Opcode) {
+  switch (Opcode) {
+  default:
+    return false;
+
+  // FIXME: Pointer Authentication instructions.
+  // We would like to measure these instructions, but they can behave
+  // differently on different platforms, and maybe the snippets need to look
+  // different for these instructions,
+  // Platform-specific handling:  On Linux, owing to the fact that disabling
+  // keys can cause exegesis to crash, the user may pass
+  // --aarch64-keep-pack-keys in case we disable authentication to ensure
----------------
atrosinenko wrote:

Typo:
```suggestion
  // --aarch64-keep-pac-keys in case we disable authentication to ensure
```

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