[llvm] [ADT] Restore handwritten vector find in SmallSet (PR #110254)

[Nikita Popov via llvm-commits]

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@@ -237,20 +237,26 @@ class SmallSet {
       return {const_iterator(I), Inserted};
     }
 
-    auto I = std::find(Vector.begin(), Vector.end(), V);
+    auto I = vfind(V);
     if (I != Vector.end()) // Don't reinsert if it already exists.
       return {const_iterator(I), false};
     if (Vector.size() < N) {
       Vector.push_back(std::forward<ArgType>(V));
       return {const_iterator(std::prev(Vector.end())), true};
     }
-
     // Otherwise, grow from vector to set.
     Set.insert(std::make_move_iterator(Vector.begin()),
                std::make_move_iterator(Vector.end()));
     Vector.clear();
     return {const_iterator(Set.insert(std::forward<ArgType>(V)).first), true};
   }
+
+  auto vfind(const T &V) const {
+    for (auto I = Vector.begin(), E = Vector.end(); I != E; ++I)
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nikic wrote:

Maybe add a comment here like `// Don't use std::find(), because it is slower`?

https://github.com/llvm/llvm-project/pull/110254