[ASTMatcher] Fix redundant macro expansion checks in getExpansionLocOfMacro

When dealing with macro parameters, getExpansionLocOfMacro ecursively calls itself to check the expansion of macro arguments. This recursive logic redundantly checks previous macro expansions, leading to significant performance degradation when macros are heavily nested.

This fix tracks already processed macros during recursion.

Author: wangmi

clang/lib/ASTMatchers/ASTMatchersInternal.cpp

@@ -36,6 +36,7 @@
 #include <cstddef>
 #include <optional>
 #include <string>
+#include <unordered_set>
 #include <utility>
 #include <vector>
 
@@ -697,27 +698,61 @@ static bool isTokenAtLoc(const SourceManager &SM, const LangOptions &LangOpts,
   return !Invalid && Text == TokenText;
 }
 
-std::optional<SourceLocation>
-getExpansionLocOfMacro(StringRef MacroName, SourceLocation Loc,
-                       const ASTContext &Context) {
+namespace {
+struct SourceLocationHash {
+  std::size_t operator()(const SourceLocation &Loc) const {
+    return Loc.getHashValue();
+  }
+};
+
+struct SourceLocationEqual {
+  bool operator()(const SourceLocation &LHS, const SourceLocation &RHS) const {
+    return LHS == RHS;
+  }
+};
+
+} // namespace
+
+static std::optional<SourceLocation> getExpansionLocOfMacroRecursive(
+    StringRef MacroName, SourceLocation Loc, const ASTContext &Context,
+    std::unordered_set<SourceLocation, SourceLocationHash, SourceLocationEqual>
+        &CheckedLocations) {
   auto &SM = Context.getSourceManager();
   const LangOptions &LangOpts = Context.getLangOpts();
   while (Loc.isMacroID()) {
+    if (CheckedLocations.count(Loc)) {
+      return std::nullopt;
+    }
+    CheckedLocations.insert(Loc);
     SrcMgr::ExpansionInfo Expansion =
         SM.getSLocEntry(SM.getFileID(Loc)).getExpansion();
-    if (Expansion.isMacroArgExpansion())
+    if (Expansion.isMacroArgExpansion()) {
       // Check macro argument for an expansion of the given macro. For example,
       // `F(G(3))`, where `MacroName` is `G`.
-      if (std::optional<SourceLocation> ArgLoc = getExpansionLocOfMacro(
-              MacroName, Expansion.getSpellingLoc(), Context))
+      if (std::optional<SourceLocation> ArgLoc =
+              getExpansionLocOfMacroRecursive(MacroName,
+                                              Expansion.getSpellingLoc(),
+                                              Context, CheckedLocations)) {
         return ArgLoc;
+      }
+    }
     Loc = Expansion.getExpansionLocStart();
-    if (isTokenAtLoc(SM, LangOpts, MacroName, Loc))
+    if (isTokenAtLoc(SM, LangOpts, MacroName, Loc)) {
       return Loc;
+    }
   }
   return std::nullopt;
 }
 
+std::optional<SourceLocation>
+getExpansionLocOfMacro(StringRef MacroName, SourceLocation Loc,
+                       const ASTContext &Context) {
+  std::unordered_set<SourceLocation, SourceLocationHash, SourceLocationEqual>
+      CheckedLocations;
+  return getExpansionLocOfMacroRecursive(MacroName, Loc, Context,
+                                         CheckedLocations);
+}
+
 std::shared_ptr<llvm::Regex> createAndVerifyRegex(StringRef Regex,
                                                   llvm::Regex::RegexFlags Flags,
                                                   StringRef MatcherID) {