[llvm] [MachineOutliner] Efficient Implementation of MachineOutliner::findCandidates() (PR #90260)

[Xuan Zhang via llvm-commits]

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@@ -593,7 +593,11 @@ void MachineOutliner::findCandidates(
     unsigned NumDiscarded = 0;
     unsigned NumKept = 0;
 #endif
-    for (const unsigned &StartIdx : RS.StartIndices) {
+    // Sort the start indices so that we can efficiently check if candidates
+    // overlap with each other in MachineOutliner::findCandidates().
+    SmallVector<unsigned> SortedStartIndices(RS.StartIndices);
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xuanzh-meta wrote:

I dropped the `const` and sort the `RS.StartIndices` in place. 

https://github.com/llvm/llvm-project/pull/90260