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

[Francesco Petrogalli via llvm-commits]

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@@ -164,16 +165,17 @@ class InstrItineraryData {
 
   /// Return the cycle for the given class and operand.  Return -1 if no
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fpetrogalli wrote:

This comment needs updating.

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