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

[Francesco Petrogalli via llvm-commits]

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@@ -173,11 +173,14 @@ unsigned TargetSchedModel::computeOperandLatency(
   const MachineInstr *DefMI, unsigned DefOperIdx,
   const MachineInstr *UseMI, unsigned UseOperIdx) const {
 
+  const unsigned InstrLatency = computeInstrLatency(DefMI);
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fpetrogalli wrote:

Please mention in the description of the PR (that will end up in the commit message) that the interface change was inspired by the refactoring you wanted to do TargetSchedModel::computeOperandLatency.

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