diff --git a/lib/Frontend/FrontendAction.cpp b/lib/Frontend/FrontendAction.cpp
new file mode 100644
index 0000000..2629b44
--- /dev/null
+++ b/lib/Frontend/FrontendAction.cpp
@@ -0,0 +1,225 @@
+//===--- FrontendAction.cpp -----------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Frontend/FrontendAction.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/Lex/HeaderSearch.h"
+#include "clang/Lex/Preprocessor.h"
+#include "clang/Frontend/ASTUnit.h"
+#include "clang/Frontend/CompilerInstance.h"
+#include "clang/Frontend/FrontendDiagnostic.h"
+#include "clang/Sema/ParseAST.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/Timer.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/raw_ostream.h"
+using namespace clang;
+
+FrontendAction::FrontendAction() : Instance(0), CurrentTimer(0) {}
+
+FrontendAction::~FrontendAction() {}
+
+void FrontendAction::setCurrentFile(llvm::StringRef Value, ASTUnit *AST) {
+  CurrentFile = Value;
+  CurrentASTUnit.reset(AST);
+}
+
+bool FrontendAction::BeginSourceFile(CompilerInstance &CI,
+                                     llvm::StringRef Filename,
+                                     bool IsAST) {
+  assert(!Instance && "Already processing a source file!");
+  assert(!Filename.empty() && "Unexpected empty filename!");
+  setCurrentFile(Filename);
+  setCompilerInstance(&CI);
+
+  // AST files follow a very different path, since they share objects via the
+  // AST unit.
+  if (IsAST) {
+    assert(!usesPreprocessorOnly() &&
+           "Attempt to pass AST file to preprocessor only action!");
+    assert(hasASTSupport() && "This action does not have AST support!");
+
+    std::string Error;
+    ASTUnit *AST = ASTUnit::LoadFromPCHFile(Filename, &Error);
+    if (!AST) {
+      CI.getDiagnostics().Report(diag::err_fe_invalid_ast_file) << Error;
+      goto failure;
+    }
+
+    setCurrentFile(Filename, AST);
+
+    // Set the shared objects, these are reset when we finish processing the
+    // file, otherwise the CompilerInstance will happily destroy them.
+    CI.setFileManager(&AST->getFileManager());
+    CI.setSourceManager(&AST->getSourceManager());
+    CI.setPreprocessor(&AST->getPreprocessor());
+    CI.setASTContext(&AST->getASTContext());
+
+    // Initialize the action.
+    if (!BeginSourceFileAction(CI, Filename))
+      goto failure;
+
+    /// Create the AST consumer.
+    CI.setASTConsumer(CreateASTConsumer(CI, Filename));
+    if (!CI.hasASTConsumer())
+      goto failure;
+
+    return true;
+  }
+
+  // Inform the diagnostic client we are processing a source file.
+  CI.getDiagnosticClient().BeginSourceFile(CI.getLangOpts(),
+                                           &CI.getPreprocessor());
+
+  // Initialize the action.
+  if (!BeginSourceFileAction(CI, Filename))
+    goto failure;
+
+  /// Create the AST context and consumer unless this is a preprocessor only
+  /// action.
+  if (!usesPreprocessorOnly()) {
+    CI.createASTContext();
+    CI.setASTConsumer(CreateASTConsumer(CI, Filename));
+    if (!CI.hasASTConsumer())
+      goto failure;
+
+    /// Use PCH?
+    if (!CI.getPreprocessorOpts().getImplicitPCHInclude().empty()) {
+      assert(hasPCHSupport() && "This action does not have PCH support!");
+      CI.createPCHExternalASTSource(
+        CI.getPreprocessorOpts().getImplicitPCHInclude());
+      if (!CI.getASTContext().getExternalSource())
+        goto failure;
+    }
+  }
+
+  // Initialize builtin info as long as we aren't using an external AST
+  // source.
+  if (!CI.hasASTContext() || !CI.getASTContext().getExternalSource()) {
+    Preprocessor &PP = CI.getPreprocessor();
+    PP.getBuiltinInfo().InitializeBuiltins(PP.getIdentifierTable(),
+                                           PP.getLangOptions().NoBuiltin);
+  }
+
+  return true;
+
+  // If we failed, reset state since the client will not end up calling the
+  // matching EndSourceFile().
+  failure:
+  if (isCurrentFileAST()) {
+    CI.takeASTContext();
+    CI.takePreprocessor();
+    CI.takeSourceManager();
+    CI.takeFileManager();
+  }
+
+  CI.getDiagnosticClient().EndSourceFile();
+  setCurrentFile("");
+  setCompilerInstance(0);
+  return false;
+}
+
+void FrontendAction::Execute() {
+  CompilerInstance &CI = getCompilerInstance();
+
+  // Initialize the main file entry. This needs to be delayed until after PCH
+  // has loaded.
+  if (isCurrentFileAST()) {
+    // Set the main file ID to an empty file.
+    //
+    // FIXME: We probably shouldn't need this, but for now this is the
+    // simplest way to reuse the logic in ParseAST.
+    const char *EmptyStr = "";
+    llvm::MemoryBuffer *SB =
+      llvm::MemoryBuffer::getMemBuffer(EmptyStr, EmptyStr, "<dummy input>");
+    CI.getSourceManager().createMainFileIDForMemBuffer(SB);
+  } else {
+    if (!CI.InitializeSourceManager(getCurrentFile()))
+      return;
+  }
+
+  llvm::TimeRegion Timer(CurrentTimer);
+  ExecuteAction();
+}
+
+void FrontendAction::EndSourceFile() {
+  CompilerInstance &CI = getCompilerInstance();
+
+  // Finalize the action.
+  EndSourceFileAction();
+
+  // Release the consumer and the AST, in that order since the consumer may
+  // perform actions in its destructor which require the context.
+  //
+  // FIXME: There is more per-file stuff we could just drop here?
+  if (CI.getFrontendOpts().DisableFree) {
+    CI.takeASTConsumer();
+    if (!isCurrentFileAST())
+      CI.takeASTContext();
+  } else {
+    CI.setASTConsumer(0);
+    if (!isCurrentFileAST())
+      CI.setASTContext(0);
+  }
+
+  if (CI.getFrontendOpts().ShowStats) {
+    llvm::errs() << "\nSTATISTICS FOR '" << getCurrentFile() << "':\n";
+    CI.getPreprocessor().PrintStats();
+    CI.getPreprocessor().getIdentifierTable().PrintStats();
+    CI.getPreprocessor().getHeaderSearchInfo().PrintStats();
+    CI.getSourceManager().PrintStats();
+    llvm::errs() << "\n";
+  }
+
+  // Cleanup the output streams, and erase the output files if we encountered
+  // an error.
+  CI.ClearOutputFiles(/*EraseFiles=*/CI.getDiagnostics().getNumErrors());
+
+  // Inform the diagnostic client we are done with this source file.
+  CI.getDiagnosticClient().EndSourceFile();
+
+  if (isCurrentFileAST()) {
+    CI.takeASTContext();
+    CI.takePreprocessor();
+    CI.takeSourceManager();
+    CI.takeFileManager();
+  }
+
+  setCompilerInstance(0);
+  setCurrentFile("");
+}
+
+//===----------------------------------------------------------------------===//
+// Utility Actions
+//===----------------------------------------------------------------------===//
+
+void ASTFrontendAction::ExecuteAction() {
+  CompilerInstance &CI = getCompilerInstance();
+
+  // FIXME: Move the truncation aspect of this into Sema, we delayed this till
+  // here so the source manager would be initialized.
+  if (hasCodeCompletionSupport() &&
+      !CI.getFrontendOpts().CodeCompletionAt.FileName.empty())
+    CI.createCodeCompletionConsumer();
+
+  // Use a code completion consumer?
+  CodeCompleteConsumer *CompletionConsumer = 0;
+  if (CI.hasCodeCompletionConsumer())
+    CompletionConsumer = &CI.getCodeCompletionConsumer();
+
+  ParseAST(CI.getPreprocessor(), &CI.getASTConsumer(), CI.getASTContext(),
+           CI.getFrontendOpts().ShowStats,
+           usesCompleteTranslationUnit(), CompletionConsumer);
+}
+
+ASTConsumer *
+PreprocessorFrontendAction::CreateASTConsumer(CompilerInstance &CI,
+                                              llvm::StringRef InFile) {
+  llvm::llvm_unreachable("Invalid CreateASTConsumer on preprocessor action!");
+}