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

[Sjoerd Meijer via llvm-commits]

================
@@ -35,6 +37,37 @@ const ExegesisTarget *ExegesisTarget::lookup(Triple TT) {
   return nullptr;
 }
 
+static bool isPointerAuthOpcode(unsigned Opcode) {
----------------
sjoerdmeijer wrote:

Another nitpick, I wanted to suggest that we create one `isUnsupportedOpcode()` function that could use these new helper functions, but then realised that is function `getIgnoredOpcodeReasonOrNull()`. We might as well use that function then, here would be my suggestion and as you see I also split up the first couple of if-statements as I don't like error messages that say "it can be this or that":

```
    const char *
    ExegesisTarget::getIgnoredOpcodeReasonOrNull(const LLVMState &State,
                                             unsigned Opcode) const {
        const MCInstrDesc &InstrDesc = State.getIC().getInstr(Opcode).Description;

        if (InstrDesc.isPseudo())
          return "Unsupported opcode: isPseudo";
        if ( InstrDesc.usesCustomInsertionHook())
          return "Unsupported opcode: usesCustomInserter";
        if (InstrDesc.isBranch())
          return "Unsupported opcode: isBranch";
        if (InstrDesc.isIndirectBranch())
          return "Unsupported opcode: isIndirectBranch";
        if (InstrDesc.isCall())
          return "Unsupported opcode: isCall";
        if (InstrDesc.isReturn())
          return "Unsupported opcode: isReturn";

         switch (Opcode) {
         default:
           return nullptr;

         // 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,
         // so let's disable this for now. 
         case AArch64::AUTDA:
         case AArch64::AUTDB:
         case AArch64::AUTDZA:
         case AArch64::AUTDZB:
         case AArch64::AUTIA:
         case AArch64::AUTIA1716:
         case AArch64::AUTIASP:
         case AArch64::AUTIAZ:
         case AArch64::AUTIB:
         case AArch64::AUTIB1716:
         case AArch64::AUTIBSP:
         case AArch64::AUTIBZ:
         case AArch64::AUTIZA:
         case AArch64::AUTIZB:
           return ""Unsupported opcode: isPointerAuth";

         // Load tag multiple instruction
         case AArch64::LDGM:
           return "Unsupported opcode: load tag multiple";
       }
       return nullptr;
    }
```



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