diff --git a/tools/versioner/src/Driver.cpp b/tools/versioner/src/Driver.cpp
new file mode 100644
index 0000000..dad8a1e
--- /dev/null
+++ b/tools/versioner/src/Driver.cpp
@@ -0,0 +1,251 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "Driver.h"
+
+#include <err.h>
+#include <string.h>
+
+#include <chrono>
+#include <mutex>
+#include <string>
+#include <thread>
+#include <unordered_map>
+#include <vector>
+
+#include <clang/AST/ASTConsumer.h>
+#include <clang/Basic/Diagnostic.h>
+#include <clang/Basic/TargetInfo.h>
+#include <clang/Driver/Compilation.h>
+#include <clang/Driver/Driver.h>
+#include <clang/Frontend/CompilerInstance.h>
+#include <clang/Frontend/CompilerInvocation.h>
+#include <clang/Frontend/FrontendAction.h>
+#include <clang/Frontend/FrontendActions.h>
+#include <clang/Frontend/TextDiagnosticPrinter.h>
+#include <clang/Frontend/Utils.h>
+#include <clang/FrontendTool/Utils.h>
+#include <llvm/ADT/IntrusiveRefCntPtr.h>
+#include <llvm/ADT/SmallVector.h>
+#include <llvm/ADT/StringRef.h>
+
+#include "Arch.h"
+#include "DeclarationDatabase.h"
+#include "versioner.h"
+
+using namespace std::chrono_literals;
+using namespace std::string_literals;
+
+using namespace clang;
+
+class VersionerASTConsumer : public clang::ASTConsumer {
+ public:
+  HeaderDatabase* header_database;
+  CompilationType type;
+
+  VersionerASTConsumer(HeaderDatabase* header_database, CompilationType type)
+      : header_database(header_database), type(type) {
+  }
+
+  virtual void HandleTranslationUnit(ASTContext& ctx) override {
+    header_database->parseAST(type, ctx);
+  }
+};
+
+class VersionerASTAction : public clang::ASTFrontendAction {
+ public:
+  HeaderDatabase* header_database;
+  CompilationType type;
+
+  VersionerASTAction(HeaderDatabase* header_database, CompilationType type)
+      : header_database(header_database), type(type) {
+  }
+
+  std::unique_ptr<ASTConsumer> CreateASTConsumer(CompilerInstance&, llvm::StringRef) override {
+    return std::make_unique<VersionerASTConsumer>(header_database, type);
+  }
+};
+
+static IntrusiveRefCntPtr<DiagnosticsEngine> constructDiags() {
+  IntrusiveRefCntPtr<DiagnosticOptions> diag_opts(new DiagnosticOptions());
+  auto diag_printer = std::make_unique<TextDiagnosticPrinter>(llvm::errs(), diag_opts.get());
+  IntrusiveRefCntPtr<DiagnosticIDs> diag_ids(new DiagnosticIDs());
+  IntrusiveRefCntPtr<DiagnosticsEngine> diags(
+      new DiagnosticsEngine(diag_ids.get(), diag_opts.get(), diag_printer.release()));
+  return diags;
+}
+
+// clang's driver is slow compared to the work it performs to compile our headers.
+// Run it once to generate flags for each target, and memoize the results.
+static std::unordered_map<CompilationType, std::vector<std::string>> cc1_flags;
+static const char* filename_placeholder = "__VERSIONER_PLACEHOLDER__";
+static void generateTargetCC1Flags(CompilationType type,
+                                   const std::vector<std::string>& include_dirs) {
+  std::vector<std::string> cmd = { "versioner" };
+  cmd.push_back("-std=c11");
+  cmd.push_back("-x");
+  cmd.push_back("c-header");
+  cmd.push_back("-fsyntax-only");
+
+  cmd.push_back("-Wall");
+  cmd.push_back("-Wextra");
+  cmd.push_back("-Werror");
+  cmd.push_back("-Wundef");
+  cmd.push_back("-Wno-unused-macros");
+  cmd.push_back("-Wno-unused-function");
+  cmd.push_back("-Wno-unused-variable");
+  cmd.push_back("-Wno-unknown-attributes");
+  cmd.push_back("-Wno-pragma-once-outside-header");
+
+  cmd.push_back("-target");
+  cmd.push_back(arch_targets[type.arch]);
+
+  cmd.push_back("-DANDROID");
+  cmd.push_back("-D__ANDROID_API__="s + std::to_string(type.api_level));
+  cmd.push_back("-D_FORTIFY_SOURCE=2");
+  cmd.push_back("-D_GNU_SOURCE");
+  cmd.push_back("-D_FILE_OFFSET_BITS="s + std::to_string(type.file_offset_bits));
+
+  cmd.push_back("-nostdinc");
+
+  if (add_include) {
+    const char* top = getenv("ANDROID_BUILD_TOP");
+    if (!top) {
+      errx(1, "-i passed, but ANDROID_BUILD_TOP is unset");
+    }
+    cmd.push_back("-include");
+    cmd.push_back(to_string(top) + "/bionic/libc/include/android/versioning.h");
+  }
+
+  for (const auto& dir : include_dirs) {
+    cmd.push_back("-isystem");
+    cmd.push_back(dir);
+  }
+
+  cmd.push_back(filename_placeholder);
+
+  auto diags = constructDiags();
+  driver::Driver driver("versioner", llvm::sys::getDefaultTargetTriple(), *diags);
+  driver.setCheckInputsExist(false);
+
+  llvm::SmallVector<const char*, 32> driver_args;
+  for (const std::string& str : cmd) {
+    driver_args.push_back(str.c_str());
+  }
+
+  std::unique_ptr<driver::Compilation> Compilation(driver.BuildCompilation(driver_args));
+  const driver::JobList& jobs = Compilation->getJobs();
+  if (jobs.size() != 1) {
+    errx(1, "driver returned %zu jobs for %s", jobs.size(), to_string(type).c_str());
+  }
+
+  const driver::Command& driver_cmd = llvm::cast<driver::Command>(*jobs.begin());
+  const driver::ArgStringList& cc_args = driver_cmd.getArguments();
+
+  if (cc_args.size() == 0) {
+    errx(1, "driver returned empty command for %s", to_string(type).c_str());
+  }
+
+  std::vector<std::string> result(cc_args.begin(), cc_args.end());
+
+  {
+    static std::mutex cc1_init_mutex;
+    std::unique_lock<std::mutex> lock(cc1_init_mutex);
+    if (cc1_flags.count(type) > 0) {
+      errx(1, "attemped to generate cc1 flags for existing CompilationType %s",
+           to_string(type).c_str());
+    }
+
+    cc1_flags.emplace(std::make_pair(type, std::move(result)));
+  }
+}
+
+static std::vector<const char*> getCC1Command(CompilationType type, const std::string& filename) {
+  const auto& target_flag_it = cc1_flags.find(type);
+  if (target_flag_it == cc1_flags.end()) {
+    errx(1, "failed to find target flags for CompilationType %s", to_string(type).c_str());
+  }
+
+  std::vector<const char*> result;
+  for (const std::string& flag : target_flag_it->second) {
+    if (flag == "-disable-free") {
+      continue;
+    } else if (flag == filename_placeholder) {
+      result.push_back(filename.c_str());
+    } else {
+      result.push_back(flag.c_str());
+    }
+  }
+  return result;
+}
+
+void initializeTargetCC1FlagCache(const std::set<CompilationType>& types,
+                                  const std::unordered_map<Arch, CompilationRequirements>& reqs) {
+  if (!cc1_flags.empty()) {
+    errx(1, "reinitializing target CC1 flag cache?");
+  }
+
+  auto start = std::chrono::high_resolution_clock::now();
+  std::vector<std::thread> threads;
+  for (const CompilationType type : types) {
+    threads.emplace_back([type, &reqs]() {
+      const auto& arch_req_it = reqs.find(type.arch);
+      if (arch_req_it == reqs.end()) {
+        errx(1, "CompilationRequirement map missing entry for CompilationType %s",
+             to_string(type).c_str());
+      }
+
+      generateTargetCC1Flags(type, arch_req_it->second.dependencies);
+    });
+  }
+  for (auto& thread : threads) {
+    thread.join();
+  }
+  auto end = std::chrono::high_resolution_clock::now();
+
+  if (verbose) {
+    auto diff = (end - start) / 1.0ms;
+    printf("Generated compiler flags for %zu targets in %0.2Lfms\n", types.size(), diff);
+  }
+
+  if (cc1_flags.empty()) {
+    errx(1, "failed to initialize target CC1 flag cache");
+  }
+}
+
+void compileHeader(HeaderDatabase* header_database, CompilationType type,
+                   const std::string& filename) {
+  auto diags = constructDiags();
+  std::vector<const char*> cc1_flags = getCC1Command(type, filename);
+  auto invocation = std::make_unique<CompilerInvocation>();
+  if (!CompilerInvocation::CreateFromArgs(*invocation.get(), &cc1_flags.front(),
+                                          &cc1_flags.front() + cc1_flags.size(), *diags)) {
+    errx(1, "failed to create CompilerInvocation");
+  }
+
+  clang::CompilerInstance Compiler;
+  Compiler.setInvocation(invocation.release());
+  Compiler.setDiagnostics(diags.get());
+
+  VersionerASTAction versioner_action(header_database, type);
+  if (!Compiler.ExecuteAction(versioner_action)) {
+    errx(1, "compilation generated warnings or errors");
+  }
+
+  if (diags->getNumWarnings() || diags->hasErrorOccurred()) {
+    errx(1, "compilation generated warnings or errors");
+  }
+}