[clang-tools-extra] [clang-doc] Improve performance by adding a short circuit (PR #96809)

[Paul Kirth via cfe-commits]

================
@@ -12,16 +12,25 @@
 #include "clang/AST/Comment.h"
 #include "clang/Index/USRGeneration.h"
 #include "llvm/ADT/StringExtras.h"
-#include "llvm/Support/Error.h"
+#include "llvm/Support/Mutex.h"
+#include <unordered_set>
 
 namespace clang {
 namespace doc {
 
+
+static std::unordered_set<std::string> USRVisited;
+
+static llvm::sys::Mutex USRVisitedGuard;
+
+
+
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ilovepi wrote:

nit: extra newlines

https://github.com/llvm/llvm-project/pull/96809