[llvm] [llvm-exegesis] [AArch64] Resolving Illegal Instruction Error (PR #132346)

[Sjoerd Meijer via llvm-commits]

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@@ -35,6 +35,14 @@ const ExegesisTarget *ExegesisTarget::lookup(Triple TT) {
   return nullptr;
 }
 
+static bool isPointerAuthOpcode(unsigned Opcode) {
+  return (Opcode >= 1648 && Opcode <= 1667); // AUT instruction class range
----------------
sjoerdmeijer wrote:

> These numbers are not stable and could change as new instructions are added - you will need to check the opcodes directly (AArch64::AUT etc).
> 
> I would expect they were useful instructions to check the throughput of though, if there was a way to do that.

Agree on the usefulness, but was thinking to leave this for another day and mark them as unsupported for now. The problem is that the snippet might need to look a bit different, as some of these need to come in pairs. If used in isolation, you might run into a useless "Illegal instruction" kernel/linux error. This confused me as that made it look like the pauth extension wasn't enabled in the kernel, but turned out be a user error, e.g. checking a pointer before it was signed, that kind of stuff. So the idea is to worry about this later, avoid crashing snippets, and figure out what to do with this later. 

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