[llvm] [ADT] Avoid repeated hash lookups (NFC) (PR #131418)

[Kazu Hirata via llvm-commits]

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@@ -366,9 +366,9 @@ scc_member_iterator<GraphT, GT>::scc_member_iterator(
     Queue.pop();
     Nodes.push_back(Node);
     for (auto &Edge : Node->Edges) {
-      NodeInfoMap[Edge.Target].IncomingMSTEdges.erase(&Edge);
-      if (MSTEdges.count(&Edge) &&
-          NodeInfoMap[Edge.Target].IncomingMSTEdges.empty()) {
+      NodeInfo &Info = NodeInfoMap[Edge.Target];
+      Info.IncomingMSTEdges.erase(&Edge);
+      if (MSTEdges.count(&Edge) && Info.IncomingMSTEdges.empty()) {
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kazutakahirata wrote:

@kuhar I don't think we can here.  `std::unordered_set::contains` is a C++20 feature.  We could switch to a `DenseSet` or something, but that would be another PR.

https://github.com/llvm/llvm-project/pull/131418