[IPO] Avoid repeated hash lookups (NFC) (llvm#129419)

Author: kazutakahirata

llvm/include/llvm/Transforms/IPO/ProfiledCallGraph.h

@@ -135,14 +135,15 @@ class ProfiledCallGraph {
   ProfiledCallGraphNode *getEntryNode() { return &Root; }
 
   void addProfiledFunction(FunctionId Name) {
-    if (!ProfiledFunctions.count(Name)) {
+    auto [It, Inserted] = ProfiledFunctions.try_emplace(Name);
+    if (Inserted) {
       // Link to synthetic root to make sure every node is reachable
       // from root. This does not affect SCC order.
       // Store the pointer of the node because the map can be rehashed.
       auto &Node =
           ProfiledCallGraphNodeList.emplace_back(ProfiledCallGraphNode(Name));
-      ProfiledFunctions[Name] = &Node;
-      Root.Edges.emplace(&Root, ProfiledFunctions[Name], 0);
+      It->second = &Node;
+      Root.Edges.emplace(&Root, It->second, 0);
     }
   }