diff --git a/lib/Frontend/ASTMerge.cpp b/lib/Frontend/ASTMerge.cpp
new file mode 100644
index 0000000..d51647b
--- /dev/null
+++ b/lib/Frontend/ASTMerge.cpp
@@ -0,0 +1,107 @@
+//===-- ASTMerge.cpp - AST Merging Frontent Action --------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+#include "clang/Frontend/ASTUnit.h"
+#include "clang/Frontend/CompilerInstance.h"
+#include "clang/Frontend/FrontendActions.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/ASTDiagnostic.h"
+#include "clang/AST/ASTImporter.h"
+
+using namespace clang;
+
+ASTConsumer *ASTMergeAction::CreateASTConsumer(CompilerInstance &CI,
+                                               llvm::StringRef InFile) {
+  return AdaptedAction->CreateASTConsumer(CI, InFile);
+}
+
+bool ASTMergeAction::BeginSourceFileAction(CompilerInstance &CI,
+                                           llvm::StringRef Filename) {
+  // FIXME: This is a hack. We need a better way to communicate the
+  // AST file, compiler instance, and file name than member variables
+  // of FrontendAction.
+  AdaptedAction->setCurrentFile(getCurrentFile(), takeCurrentASTUnit());
+  AdaptedAction->setCompilerInstance(&CI);
+  return AdaptedAction->BeginSourceFileAction(CI, Filename);
+}
+
+void ASTMergeAction::ExecuteAction() {
+  CompilerInstance &CI = getCompilerInstance();
+  CI.getDiagnostics().SetArgToStringFn(&FormatASTNodeDiagnosticArgument,
+                                       &CI.getASTContext());
+  for (unsigned I = 0, N = ASTFiles.size(); I != N; ++I) {
+    Diagnostic ASTDiags(CI.getDiagnostics().getClient());
+    
+    ASTUnit *Unit = ASTUnit::LoadFromPCHFile(ASTFiles[I], ASTDiags,
+                                             false, true);
+    if (!Unit)
+      continue;
+
+    ASTDiags.SetArgToStringFn(&FormatASTNodeDiagnosticArgument,
+                              &Unit->getASTContext());
+    ASTImporter Importer(CI.getASTContext(), 
+                         CI.getFileManager(),
+                         CI.getDiagnostics(),
+                         Unit->getASTContext(), 
+                         Unit->getFileManager(),
+                         ASTDiags);
+
+    TranslationUnitDecl *TU = Unit->getASTContext().getTranslationUnitDecl();
+    for (DeclContext::decl_iterator D = TU->decls_begin(), 
+                                 DEnd = TU->decls_end();
+         D != DEnd; ++D) {
+      // FIXME: We only merge variables whose names start with x. Why
+      // would anyone want anything else?
+      if (VarDecl *VD = dyn_cast<VarDecl>(*D))
+        if (VD->getIdentifier() && 
+            *VD->getIdentifier()->getNameStart() == 'x') {
+          Decl *Merged = Importer.Import(VD);
+          (void)Merged;
+        }
+    }
+
+    delete Unit;
+  }
+
+
+  return AdaptedAction->ExecuteAction();
+}
+
+void ASTMergeAction::EndSourceFileAction() {
+  return AdaptedAction->EndSourceFileAction();
+}
+
+ASTMergeAction::ASTMergeAction(FrontendAction *AdaptedAction,
+                               std::string *ASTFiles, unsigned NumASTFiles)
+  : AdaptedAction(AdaptedAction), ASTFiles(ASTFiles, ASTFiles + NumASTFiles) {
+  assert(AdaptedAction && "ASTMergeAction needs an action to adapt");
+}
+
+ASTMergeAction::~ASTMergeAction() { 
+  delete AdaptedAction;
+}
+
+bool ASTMergeAction::usesPreprocessorOnly() const {
+  return AdaptedAction->usesPreprocessorOnly();
+}
+
+bool ASTMergeAction::usesCompleteTranslationUnit() {
+  return AdaptedAction->usesCompleteTranslationUnit();
+}
+
+bool ASTMergeAction::hasPCHSupport() const {
+  return AdaptedAction->hasPCHSupport();
+}
+
+bool ASTMergeAction::hasASTSupport() const {
+  return AdaptedAction->hasASTSupport();
+}
+
+bool ASTMergeAction::hasCodeCompletionSupport() const {
+  return AdaptedAction->hasCodeCompletionSupport();
+}