TypeTree add fast path for checkedOrIn

enzyme/Enzyme/TypeAnalysis/TypeTree.h

@@ -1239,8 +1239,26 @@ class TypeTree : public std::enable_shared_from_this<TypeTree> {
   /// changed Setting `PointerIntSame` considers pointers and integers as
   /// equivalent If this is an illegal operation, `LegalOr` will be set to false
   bool checkedOrIn(const TypeTree &RHS, bool PointerIntSame, bool &LegalOr) {
-    // TODO detect recursive merge and simplify
+    // Add fast path where nothing could change because all potentially inserted
+    // value are already in the map
+    {
+      bool newval = false;
+      for (const auto &pair : mapping) {
+        auto found = mapping.find(pair.first);
+        if (found == mapping.end()) {
+          newval = true;
+          break;
+        }
+        if (found->second != pair.second) {
+          newval = true;
+          break;
+        }
+      }
+      if (!newval)
+        return false;
+    }
 
+    // TODO detect recursive merge and simplify
     bool changed = false;
     for (auto &pair : RHS.mapping) {
       changed |= checkedOrIn(pair.first, pair.second, PointerIntSame, LegalOr);