[clang] Add time trace scopes to addToCallGraph & getCFG (PR #174717)

[Utkarsh Saxena via cfe-commits]

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@@ -61,6 +62,7 @@ class CallGraph : public DynamicRecursiveASTVisitor {
   ///
   /// Recursively walks the declaration to find all the dependent Decls as well.
   void addToCallGraph(Decl *D) {
+    llvm::TimeTraceScope TimeProfile("AddToCallGraph");
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usx95 wrote:

I would not worry too much of the overhead here as this is a smallish string (`AddToCallGraph`). I have seen larger string to work fine (like fully qualified templated names:smile: )  
Wrt to a having a common larger parent, callers can choose to do this explicitly or we can introduce `ArrayRef` API as well later if needed.

https://github.com/llvm/llvm-project/pull/174717