[llvm] TargetInstrInfo: make getOperandLatency return optional (NFC) (PR #73769)

[Francesco Petrogalli via llvm-commits]

================
@@ -173,11 +173,14 @@ unsigned TargetSchedModel::computeOperandLatency(
   const MachineInstr *DefMI, unsigned DefOperIdx,
   const MachineInstr *UseMI, unsigned UseOperIdx) const {
 
+  const unsigned InstrLatency = computeInstrLatency(DefMI);
+  const unsigned DefaultDefLatency = TII->defaultDefLatency(SchedModel, *DefMI);
+
   if (!hasInstrSchedModel() && !hasInstrItineraries())
-    return TII->defaultDefLatency(SchedModel, *DefMI);
+    return InstrLatency;
 
   if (hasInstrItineraries()) {
-    int OperLatency = 0;
+    std::optional<unsigned> OperLatency = 0;
----------------
fpetrogalli wrote:

I think you want this:

```suggestion
    std::optional<unsigned> OperLatency;
```


Otherwise the optional `has_value() == true`.

I am aware it is not a problem for the current code, but if someone modifies the if/else following the declaration we might end up thinking that the OpenradLatency is set, when it is not.

https://github.com/llvm/llvm-project/pull/73769