diff --git a/lldb/source/Plugins/TypeSystem/Swift/SwiftASTContext.cpp b/lldb/source/Plugins/TypeSystem/Swift/SwiftASTContext.cpp
index f5ff8da6aa1e7..7c142b5efc89b 100644
--- a/lldb/source/Plugins/TypeSystem/Swift/SwiftASTContext.cpp
+++ b/lldb/source/Plugins/TypeSystem/Swift/SwiftASTContext.cpp
@@ -1448,44 +1448,25 @@ void ApplyWorkingDir(SmallString &clang_argument, StringRef cur_working_dir) {
   llvm::sys::path::append(clang_argument, cur_working_dir, rel_path);
   llvm::sys::path::remove_dots(clang_argument);
 }
-
-std::array<StringRef, 2> macro_flags = { "-D", "-U" };
-
-bool IsMultiArgClangFlag(StringRef arg) {
-  for (auto &flag : macro_flags)
-    if (flag == arg)
-      return true;
-  return arg == "-working-directory";
-}
-
-bool IsMacroDefinition(StringRef arg) {
-  for (auto &flag : macro_flags)
-    if (arg.startswith(flag))
-      return true;
-  return false;
-}
-
-bool ShouldUnique(StringRef arg) {
-  return IsMacroDefinition(arg);
-}
 } // namespace
 
 void SwiftASTContext::AddExtraClangArgs(std::vector<std::string> ExtraArgs) {
-  swift::ClangImporterOptions &importer_options = GetClangImporterOptions();
-  llvm::DenseSet<StringRef> unique_flags;
-  for (auto &arg : importer_options.ExtraArgs)
-    unique_flags.insert(arg);
-
   llvm::SmallString<128> cur_working_dir;
   llvm::SmallString<128> clang_argument;
   for (const std::string &arg : ExtraArgs) {
-    // Join multi-arg options for uniquing.
+    // Join multi-arg -D and -U options for uniquing.
     clang_argument += arg;
-    if (IsMultiArgClangFlag(clang_argument))
+    if (clang_argument == "-D" || clang_argument == "-U" ||
+        clang_argument == "-working-directory")
       continue;
 
     auto clear_arg = llvm::make_scope_exit([&] { clang_argument.clear(); });
 
+    // Enable uniquing for -D and -U options.
+    bool is_macro = (clang_argument.size() >= 2 && clang_argument[0] == '-' &&
+                     (clang_argument[1] == 'D' || clang_argument[1] == 'U'));
+    bool unique = is_macro;
+
     // Consume any -working-directory arguments.
     StringRef cwd(clang_argument);
     if (cwd.consume_front("-working-directory")) {
@@ -1493,21 +1474,13 @@ void SwiftASTContext::AddExtraClangArgs(std::vector<std::string> ExtraArgs) {
       continue;
     }
     // Drop -Werror; it would only cause trouble in the debugger.
-    if (clang_argument.startswith("-Werror"))
+    if (clang_argument.startswith("-Werror")) {
       continue;
-
-    if (clang_argument.empty())
-      continue;
-
+    }
     // Otherwise add the argument to the list.
-    if (!IsMacroDefinition(clang_argument))
+    if (!is_macro)
       ApplyWorkingDir(clang_argument, cur_working_dir);
-
-    auto clang_arg_str = clang_argument.str();
-    if (!ShouldUnique(clang_argument) || !unique_flags.count(clang_arg_str)) {
-      importer_options.ExtraArgs.push_back(clang_arg_str);
-      unique_flags.insert(clang_arg_str);
-    }
+    AddClangArgument(clang_argument.str(), unique);
   }
 }
 
@@ -3414,6 +3387,41 @@ swift::DWARFImporterDelegate *SwiftASTContext::GetDWARFImporterDelegate() {
   return m_dwarf_importer_delegate_up.get();
 }
 
+bool SwiftASTContext::AddClangArgument(std::string clang_arg, bool unique) {
+  if (clang_arg.empty())
+    return false;
+
+  swift::ClangImporterOptions &importer_options = GetClangImporterOptions();
+  // Avoid inserting the same option twice.
+  if (unique)
+    for (std::string &arg : importer_options.ExtraArgs)
+      if (arg == clang_arg)
+        return false;
+
+  importer_options.ExtraArgs.push_back(clang_arg);
+  return true;
+}
+
+bool SwiftASTContext::AddClangArgumentPair(StringRef clang_arg_1,
+                                           StringRef clang_arg_2) {
+  if (clang_arg_1.empty() || clang_arg_2.empty())
+    return false;
+
+  swift::ClangImporterOptions &importer_options = GetClangImporterOptions();
+  bool add_hmap = true;
+  for (ssize_t ai = 0, ae = importer_options.ExtraArgs.size() -
+                            1; // -1 because we look at the next one too
+       ai < ae; ++ai) {
+    if (clang_arg_1.equals(importer_options.ExtraArgs[ai]) &&
+        clang_arg_2.equals(importer_options.ExtraArgs[ai + 1]))
+      return false;
+  }
+
+  importer_options.ExtraArgs.push_back(clang_arg_1);
+  importer_options.ExtraArgs.push_back(clang_arg_2);
+  return true;
+}
+
 const swift::SearchPathOptions *SwiftASTContext::GetSearchPathOptions() const {
   VALID_OR_RETURN(0);
 
diff --git a/lldb/source/Plugins/TypeSystem/Swift/SwiftASTContext.h b/lldb/source/Plugins/TypeSystem/Swift/SwiftASTContext.h
index e1439c0a86a13..6c5434aa59db4 100644
--- a/lldb/source/Plugins/TypeSystem/Swift/SwiftASTContext.h
+++ b/lldb/source/Plugins/TypeSystem/Swift/SwiftASTContext.h
@@ -215,6 +215,10 @@ class SwiftASTContext : public TypeSystemSwift {
 
   bool AddModuleSearchPath(llvm::StringRef path);
 
+  bool AddClangArgument(std::string arg, bool unique = true);
+
+  bool AddClangArgumentPair(llvm::StringRef arg1, llvm::StringRef arg2);
+
   /// Add a list of Clang arguments to the ClangImporter options and
   /// apply the working directory to any relative paths.
   void AddExtraClangArgs(std::vector<std::string> ExtraArgs);