[llvm] [llvm-exegesis][AArch64] Disable pauth and ldgm as unsupported instructions (PR #132346)

[Aiden Grossman via llvm-commits]

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@@ -335,6 +335,9 @@ class ExegesisTarget {
   const OpcodeAvailabilityChecker IsOpcodeAvailable;
 };
 
+bool isPointerAuth(unsigned Opcode);
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boomanaiden154 wrote:

These do not make sense to have in the normal target given they are specific to AArch64. It would be better (in my opinion) to add a method similar to `getIgnoredOpcodeReasonOrNull` that can be overrided by targets and then gets invoked in `getIgnoredOpcodeReasonsOrNull`.

https://github.com/llvm/llvm-project/pull/132346