Add time trace scopes to addToCallGraph & getCFG (#174717)

This PR adds performance instrumentation to `clang::CallGraph` and
`clang::CFG` to aid in benchmarking the overhead of call
graph construction and CFG rebuilding.

This aims to facilitate benchmarking on large codebases like LLVM to
ensure that the performance impact of new analysis-based warnings
remains within acceptable regressions.

clang/include/clang/Analysis/CallGraph.h

@@ -26,6 +26,7 @@
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/iterator_range.h"
+#include "llvm/Support/TimeProfiler.h"
 #include <memory>
 
 namespace clang {
@@ -61,6 +62,7 @@ public:
   ///
   /// Recursively walks the declaration to find all the dependent Decls as well.
   void addToCallGraph(Decl *D) {
+    llvm::TimeTraceScope TimeProfile("AddToCallGraph");
     TraverseDecl(D);
   }
 

clang/lib/Analysis/CFG.cpp

@@ -52,6 +52,7 @@
 #include "llvm/Support/Format.h"
 #include "llvm/Support/GraphWriter.h"
 #include "llvm/Support/SaveAndRestore.h"
+#include "llvm/Support/TimeProfiler.h"
 #include "llvm/Support/raw_ostream.h"
 #include <cassert>
 #include <memory>
@@ -5359,6 +5360,7 @@ CFGBlock *CFG::createBlock() {
 /// buildCFG - Constructs a CFG from an AST.
 std::unique_ptr<CFG> CFG::buildCFG(const Decl *D, Stmt *Statement,
                                    ASTContext *C, const BuildOptions &BO) {
+  llvm::TimeTraceScope TimeProfile("BuildCFG");
   CFGBuilder Builder(C, BO);
   return Builder.buildCFG(D, Statement);
 }

clang/unittests/Support/TimeProfilerTest.cpp

@@ -333,8 +333,10 @@ Frontend (test.cc)
 | | InstantiateFunction (fooA<int>, a.h:7)
 | | | InstantiateFunction (fooB<int>, b.h:8)
 | | | | DeferInstantiation (fooC<int>)
+| | | | BuildCFG
 | | | DeferInstantiation (fooMTA<int>)
 | | | InstantiateFunction (fooC<int>, b.h:3)
+| | | | BuildCFG
 | | | InstantiateFunction (fooMTA<int>, a.h:4)
 )",
             buildTraceGraph(Json));