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

[Björn Pettersson via llvm-commits]

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@@ -186,21 +190,13 @@ unsigned TargetSchedModel::computeOperandLatency(
       unsigned DefClass = DefMI->getDesc().getSchedClass();
       OperLatency = InstrItins.getOperandCycle(DefClass, DefOperIdx);
     }
-    if (OperLatency >= 0)
-      return OperLatency;
-
-    // No operand latency was found.
-    unsigned InstrLatency = TII->getInstrLatency(&InstrItins, *DefMI);
-
-    // Expected latency is the max of the stage latency and itinerary props.
-    // Rather than directly querying InstrItins stage latency, we call a TII
-    // hook to allow subtargets to specialize latency. This hook is only
-    // applicable to the InstrItins model. InstrSchedModel should model all
-    // special cases without TII hooks.
-    InstrLatency =
-        std::max(InstrLatency, TII->defaultDefLatency(SchedModel, *DefMI));
-    return InstrLatency;
+
+    // Expected latency is the max of InstrLatency and DefaultDefLatency, if we
+    // didn't find an operand latency.
+    return OperLatency ? *OperLatency
+                       : std::max(InstrLatency, DefaultDefLatency);
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bjope wrote:

What happened to the the `InstrLatency = TII->getInstrLatency(&InstrItins, *DefMI);` statement?

Once again, the commit is doing lots of refactoring, but then it seems like you slipped in a potential change in the behavior as well.

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