Index: clang/test/Analysis/func-mapping-path.c
===================================================================
--- /dev/null
+++ clang/test/Analysis/func-mapping-path.c
@@ -0,0 +1,3 @@
+// RUN: %clang_extdef_map %s -m '^(.*)clang(.*)$' -r '\1ctu-dir\2.ast' -- | FileCheck %s
+// CHECK: {{ctu-dir.*func-mapping-path\.c\.ast}}
+void f() {}
Index: clang/tools/clang-extdef-mapping/ClangExtDefMapGen.cpp
===================================================================
--- clang/tools/clang-extdef-mapping/ClangExtDefMapGen.cpp
+++ clang/tools/clang-extdef-mapping/ClangExtDefMapGen.cpp
@@ -30,11 +30,45 @@
 using namespace clang::tooling;
 
 static cl::OptionCategory ClangExtDefMapGenCategory("clang-extdefmapgen options");
+static cl::opt<std::string> OutputPathAdjusterMatcher(
+    "m", cl::desc("Match the part of output path to be replaced with regex"),
+    cl::cat(ClangExtDefMapGenCategory));
+static cl::opt<std::string> OutputPathAdjusterNewPath(
+    "r", cl::desc("The string which matched pattern will be replaced to"),
+    cl::cat(ClangExtDefMapGenCategory));
+
+namespace {
+class OutputPathAdjuster {
+  Regex Matcher;
+  std::string NewPath;
+
+public:
+  std::string adjust(StringRef Path) const {
+    return Matcher.sub(NewPath, Path);
+  }
+
+  bool resetMatcher(StringRef MatcherStr, StringRef NewPathStr);
+};
+
+bool OutputPathAdjuster::resetMatcher(StringRef MatcherStr,
+                                      StringRef NewPathStr) {
+  std::string ErrMsg;
+  Regex MatcherRegex(MatcherStr);
+  if (!MatcherRegex.isValid(ErrMsg)) {
+    errs() << "Invalid adjuster template: " << ErrMsg << '\n';
+    return false;
+  }
+
+  Matcher = std::move(MatcherRegex);
+  NewPath = NewPathStr.str();
+  return true;
+}
+} // namespace
 
 class MapExtDefNamesConsumer : public ASTConsumer {
 public:
-  MapExtDefNamesConsumer(ASTContext &Context)
-      : Ctx(Context), SM(Context.getSourceManager()) {}
+  MapExtDefNamesConsumer(const OutputPathAdjuster *Adjuster)
+      : Adjuster(Adjuster) {}
 
   ~MapExtDefNamesConsumer() {
     // Flush results to standard output.
@@ -49,10 +83,9 @@
   void handleDecl(const Decl *D);
   void addIfInMain(const DeclaratorDecl *DD, SourceLocation defStart);
 
-  ASTContext &Ctx;
-  SourceManager &SM;
   llvm::StringMap<std::string> Index;
   std::string CurrentFileName;
+  const OutputPathAdjuster *Adjuster = nullptr;
 };
 
 void MapExtDefNamesConsumer::handleDecl(const Decl *D) {
@@ -64,7 +97,7 @@
       if (const Stmt *Body = FD->getBody())
         addIfInMain(FD, Body->getBeginLoc());
   } else if (const auto *VD = dyn_cast<VarDecl>(D)) {
-    if (cross_tu::containsConst(VD, Ctx) && VD->hasInit())
+    if (cross_tu::containsConst(VD, VD->getASTContext()) && VD->hasInit())
       if (const Expr *Init = VD->getInit())
         addIfInMain(VD, Init->getBeginLoc());
   }
@@ -82,9 +115,12 @@
     return;
   assert(!LookupName->empty() && "Lookup name should be non-empty.");
 
+  SourceManager &SM = DD->getASTContext().getSourceManager();
   if (CurrentFileName.empty()) {
     CurrentFileName = std::string(
         SM.getFileEntryForID(SM.getMainFileID())->tryGetRealPathName());
+    if (Adjuster)
+      CurrentFileName = Adjuster->adjust(CurrentFileName);
     if (CurrentFileName.empty())
       CurrentFileName = "invalid_file";
   }
@@ -101,11 +137,15 @@
   }
 }
 
-class MapExtDefNamesAction : public ASTFrontendAction {
-protected:
-  std::unique_ptr<ASTConsumer> CreateASTConsumer(CompilerInstance &CI,
-                                                 llvm::StringRef) override {
-    return std::make_unique<MapExtDefNamesConsumer>(CI.getASTContext());
+class MapExtDefNamesConsumerFactory {
+  const OutputPathAdjuster *Adjuster = nullptr;
+
+public:
+  MapExtDefNamesConsumerFactory(const OutputPathAdjuster *Adjuster)
+      : Adjuster(Adjuster) {}
+
+  std::unique_ptr<ASTConsumer> newASTConsumer() {
+    return std::make_unique<MapExtDefNamesConsumer>(Adjuster);
   }
 };
 
@@ -118,7 +158,8 @@
 
   const char *Overview = "\nThis tool collects the USR name and location "
                          "of external definitions in the source files "
-                         "(excluding headers).\n";
+                         "(excluding headers).\n\nReset output path with -m "
+                         "<regex> -r <new-path>.\n";
   auto ExpectedParser = CommonOptionsParser::create(
       argc, argv, ClangExtDefMapGenCategory, cl::ZeroOrMore, Overview);
   if (!ExpectedParser) {
@@ -127,8 +168,17 @@
   }
   CommonOptionsParser &OptionsParser = ExpectedParser.get();
 
+  std::unique_ptr<OutputPathAdjuster> Adjuster;
+  if (!OutputPathAdjusterMatcher.empty()) {
+    Adjuster = std::make_unique<OutputPathAdjuster>();
+    if (!Adjuster->resetMatcher(OutputPathAdjusterMatcher,
+                                OutputPathAdjusterNewPath))
+      return 1;
+  }
+
   ClangTool Tool(OptionsParser.getCompilations(),
                  OptionsParser.getSourcePathList());
 
-  return Tool.run(newFrontendActionFactory<MapExtDefNamesAction>().get());
+  MapExtDefNamesConsumerFactory Factory(Adjuster.get());
+  return Tool.run(newFrontendActionFactory(&Factory).get());
 }