Index: include/llvm/Passes/PassPlugin.h
===================================================================
--- /dev/null
+++ include/llvm/Passes/PassPlugin.h
@@ -0,0 +1,72 @@
+//===- llvm/Passes/PassPlugin.h - Public Plugin API -----------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This defines the public entry point for new-PM pass plugins.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_PASSES_PASSPLUGIN_H
+#define LLVM_PASSES_PASSPLUGIN_H
+
+#include "llvm/Support/Compiler.h"
+#include <cstdint>
+#include <functional>
+
+namespace llvm {
+class PassBuilder;
+
+/// \macro LLVM_PLUGIN_API_VERSION
+/// \brief Identifies the API version understood by this plugin.
+///
+/// When a plugin is loaded, the driver will check it's supported plugin version
+/// against that of the plugin. A mismatch is an error. The supported version
+/// will integrated for ABI-breaking changes to the \c PluginInfo struct, i.e.
+/// when callbacks are added, removed, or reordered.
+#define LLVM_PLUGIN_API_VERSION 1
+
+extern "C" {
+/// \brief Information about the plugin required to load its passes
+struct PluginInfo {
+  /// \brief The API version understood by this plugin, usually \c
+  /// LLVM_PLUGIN_API_VERSION
+  uint32_t APIVersion;
+  /// \brief A meaningful name of the plugin.
+  const char *PluginName;
+  /// \brief The version of the plugin.
+  const char *PluginVersion;
+
+  /// \brief The callback for registering plugin passes with a \c PassBuilder
+  /// instance
+  void (*RegisterPassBuilderCallbacks)(PassBuilder &);
+};
+
+/// \brief The public entry point for a pass plugin.
+///
+/// When a plugin is loaded by the driver, it will call this entry point to
+/// obtain information about this plugin and about how to register its passes.
+/// This function needs to be implemented by the plugin, either manually or
+/// using the \c LLVM_PLUGIN macro.
+PluginInfo LLVM_ATTRIBUTE_WEAK LLVM_PLUGIN_EXPORT llvmPluginGetInfo();
+}
+}
+
+/// \macro LLVM_PLUGIN
+/// \brief A utility macro to implement a default entry point
+/// Example usage:
+///
+///      LLVM_PLUGIN("MyAwesomePlugin", "0.1", registerMyPasses)
+#define LLVM_PLUGIN(NAME, PLUGIN_VERSION, REGISTER_CALLBACKS)                  \
+  extern "C" {                                                                 \
+  ::llvm::PluginInfo LLVM_PLUGIN_EXPORT llvmPluginGetInfo() {                  \
+    return {LLVM_PLUGIN_API_VERSION, NAME, PLUGIN_VERSION,                     \
+            REGISTER_CALLBACKS};                                               \
+  }                                                                            \
+  }
+
+#endif /* LLVM_PASSES_PASSPLUGIN_H */
Index: include/llvm/Passes/PassPluginLoader.h
===================================================================
--- /dev/null
+++ include/llvm/Passes/PassPluginLoader.h
@@ -0,0 +1,45 @@
+//===- llvm/Passes/PassPluginLoader.h - Load Plugins for New PM Passes ----===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_PASSES_PASSPLUGINLOADER_H
+#define LLVM_PASSES_PASSPLUGINLOADER_H
+
+#include "llvm/ADT/Optional.h"
+#include "llvm/Passes/PassPlugin.h"
+#include "llvm/Support/DynamicLibrary.h"
+#include "llvm/Support/Error.h"
+
+namespace llvm {
+/// \brief Load pass plugins from a file
+class PassPlugin {
+public:
+  /// \brief Attempts to load a pass plugin from a given file.
+  ///
+  /// \returns Returns an error if either the library cannot be found or loaded,
+  /// there is no public entry point, or the plugin implements the wrong API
+  /// version.
+  static Expected<PassPlugin> Load(const std::string &Filename);
+
+  /// \brief Get the filename of the loaded plugin.
+  std::string &getFilename() { return Filename; }
+
+  /// \brief Get the \c PluginInfo information of the plugin.
+  const PluginInfo &getInfo() const { return Info; }
+
+private:
+  PassPlugin(const std::string &Filename, const sys::DynamicLibrary &Library)
+      : Filename(Filename), Library(Library), Info() {}
+
+  std::string Filename;
+  sys::DynamicLibrary Library;
+  PluginInfo Info;
+};
+}
+
+#endif /* LLVM_PASSES_PASSPLUGINLOADER_H */
Index: include/llvm/Support/Compiler.h
===================================================================
--- include/llvm/Support/Compiler.h
+++ include/llvm/Support/Compiler.h
@@ -503,4 +503,13 @@
 #define LLVM_ENABLE_EXCEPTIONS 1
 #endif
 
+/// \macro LLVM_PLUGIN_EXPORT
+/// \brief Used to export the well-known entry point for registering loaded pass
+/// plugins
+#ifdef WIN32
+#define LLVM_PLUGIN_EXPORT __declspec(dllexport)
+#else
+#define LLVM_PLUGIN_EXPORT
+#endif
+
 #endif
Index: lib/Passes/CMakeLists.txt
===================================================================
--- lib/Passes/CMakeLists.txt
+++ lib/Passes/CMakeLists.txt
@@ -1,5 +1,6 @@
 add_llvm_library(LLVMPasses
   PassBuilder.cpp
+  PassPluginLoader.cpp
 
   ADDITIONAL_HEADER_DIRS
   ${LLVM_MAIN_INCLUDE_DIR}/llvm/Passes
Index: lib/Passes/PassPluginLoader.cpp
===================================================================
--- /dev/null
+++ lib/Passes/PassPluginLoader.cpp
@@ -0,0 +1,46 @@
+//===- lib/Passes/PassPluginLoader.cpp - Load Plugins for New PM Passes ---===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Passes/PassPluginLoader.h"
+#include "llvm/ADT/Optional.h"
+#include "llvm/Passes/PassPlugin.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace llvm;
+
+Expected<PassPlugin> PassPlugin::Load(const std::string &Filename) {
+  std::string Error;
+  auto Library =
+      sys::DynamicLibrary::getPermanentLibrary(Filename.c_str(), &Error);
+  if (!Library.isValid())
+    return make_error<StringError>("Could not load library '" + Filename + "'",
+                                   inconvertibleErrorCode());
+
+  PassPlugin P{Filename, Library};
+  auto *getDetailsFn = Library.SearchForAddressOfSymbol("llvmPluginGetInfo");
+
+  if (!getDetailsFn)
+    // If the symbol isn't found, this is probably a legacy plugin, which is an
+    // error
+    return make_error<StringError>("Plugin entry point not found in '" +
+                                       Filename + "'. Is this a legacy plugin?",
+                                   inconvertibleErrorCode());
+
+  P.Info = reinterpret_cast<decltype(llvmPluginGetInfo) *>(getDetailsFn)();
+
+  if (P.Info.APIVersion != LLVM_PLUGIN_API_VERSION) {
+    return make_error<StringError>(
+        "Wrong API version on plugin '" + Filename + "'. Got version " +
+            std::to_string(P.Info.APIVersion) + ", supported version is " +
+            std::to_string(LLVM_PLUGIN_API_VERSION) + ".",
+        inconvertibleErrorCode());
+  }
+
+  return P;
+}
Index: tools/opt/NewPMDriver.cpp
===================================================================
--- tools/opt/NewPMDriver.cpp
+++ tools/opt/NewPMDriver.cpp
@@ -27,6 +27,8 @@
 #include "llvm/IR/PassManager.h"
 #include "llvm/IR/Verifier.h"
 #include "llvm/Passes/PassBuilder.h"
+#include "llvm/Passes/PassPlugin.h"
+#include "llvm/Passes/PassPluginLoader.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/ToolOutputFile.h"
@@ -41,6 +43,9 @@
     DebugPM("debug-pass-manager", cl::Hidden,
             cl::desc("Print pass management debugging information"));
 
+static cl::list<std::string>
+    PassPlugins("load-pass-plugin", cl::desc("Load passes from plugin library"));
+
 // This flag specifies a textual description of the alias analysis pipeline to
 // use when querying for aliasing information. It only works in concert with
 // the "passes" flag above.
@@ -210,6 +215,16 @@
   PassBuilder PB(TM, P);
   registerEPCallbacks(PB, VerifyEachPass, DebugPM);
 
+  // Call pass plugins
+  for (auto &PluginFN : PassPlugins) {
+    auto PassPlugin = PassPlugin::Load(PluginFN);
+    if (!PassPlugin)
+      errs() << "Failed to load passes from '" << PluginFN
+             << "'. Request ignored.\n";
+    else
+      PassPlugin->getInfo().RegisterPassBuilderCallbacks(PB);
+  }
+
   // Register a callback that creates the debugify passes as needed.
   PB.registerPipelineParsingCallback(
       [](StringRef Name, ModulePassManager &MPM,
Index: unittests/CMakeLists.txt
===================================================================
--- unittests/CMakeLists.txt
+++ unittests/CMakeLists.txt
@@ -22,6 +22,7 @@
 add_subdirectory(BinaryFormat)
 add_subdirectory(ObjectYAML)
 add_subdirectory(Option)
+add_subdirectory(Passes)
 add_subdirectory(ProfileData)
 add_subdirectory(Support)
 add_subdirectory(Target)
Index: unittests/Passes/CMakeLists.txt
===================================================================
--- /dev/null
+++ unittests/Passes/CMakeLists.txt
@@ -0,0 +1,21 @@
+set(LLVM_LINK_COMPONENTS Support Passes Core)
+
+add_llvm_unittest(PluginsTests PluginsTest.cpp)
+export_executable_symbols(PluginsTests)
+
+add_library(TestPlugin SHARED Plugin.cxx)
+
+set_output_directory(TestPlugin
+  BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR}/${CMAKE_CFG_INTDIR}
+  LIBRARY_DIR ${CMAKE_CURRENT_BINARY_DIR}/${CMAKE_CFG_INTDIR}
+  )
+
+set_target_properties(TestPlugin
+  PROPERTIES PREFIX ""
+  SUFFIX ".so"
+  )
+
+llvm_map_components_to_libnames(LLVMDependencies ${LLVM_LINK_COMPONENTS})
+target_link_libraries(TestPlugin ${LLVMDependencies})
+
+add_dependencies(PluginsTests TestPlugin)
Index: unittests/Passes/Plugin.cxx
===================================================================
--- /dev/null
+++ unittests/Passes/Plugin.cxx
@@ -0,0 +1,36 @@
+//===- unittests/Passes/Plugins/Plugin.cxx --------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Config/config.h"
+#include "llvm/Passes/PassBuilder.h"
+#include "llvm/Passes/PassPlugin.h"
+
+#include "TestPlugin.h"
+
+using namespace llvm;
+
+struct TestModulePass : public PassInfoMixin<TestModulePass> {
+  PreservedAnalyses run(Module &M, ModuleAnalysisManager &MAM) {
+    return PreservedAnalyses::all();
+  }
+};
+
+void registerCallbacks(PassBuilder &PB) {
+  PB.registerPipelineParsingCallback(
+      [](StringRef Name, ModulePassManager &PM,
+         ArrayRef<PassBuilder::PipelineElement> InnerPipeline) {
+        if (Name == "plugin-pass") {
+          PM.addPass(TestModulePass());
+          return true;
+        }
+        return false;
+      });
+}
+
+LLVM_PLUGIN(TEST_PLUGIN_NAME, TEST_PLUGIN_VERSION, registerCallbacks)
Index: unittests/Passes/PluginsTest.cpp
===================================================================
--- /dev/null
+++ unittests/Passes/PluginsTest.cpp
@@ -0,0 +1,60 @@
+//===- unittests/Passes/Plugins/PluginsTest.cpp ---------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/CGSCCPassManager.h"
+#include "llvm/Config/config.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/Passes/PassBuilder.h"
+#include "llvm/Passes/PassPlugin.h"
+#include "llvm/Passes/PassPluginLoader.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/ManagedStatic.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Transforms/Scalar/LoopPassManager.h"
+#include "gtest/gtest.h"
+
+#include "TestPlugin.h"
+
+using namespace llvm;
+
+void anchor() {}
+
+static std::string LibPath(const std::string Name = "TestPlugin") {
+  const std::vector<testing::internal::string> &Argvs =
+      testing::internal::GetArgvs();
+  const char *Argv0 = Argvs.size() > 0 ? Argvs[0].c_str() : "PluginsTests";
+  void *Ptr = (void *)anchor;
+  std::string Path = sys::fs::getMainExecutable(Argv0, Ptr);
+  llvm::SmallString<256> Buf{sys::path::parent_path(Path)};
+  sys::path::append(Buf, (Name + ".so").c_str());
+  return Buf.str();
+}
+
+static std::string StdString(const char *c_str) { return c_str ? c_str : ""; }
+
+TEST(PluginsTests, LoadPlugin) {
+  auto PluginPath = LibPath();
+  ASSERT_NE("", PluginPath);
+
+  Expected<PassPlugin> Plugin = PassPlugin::Load(PluginPath);
+  ASSERT_TRUE(!!Plugin) << "Plugin path: " << PluginPath;
+
+  const auto &Info = Plugin->getInfo();
+
+  ASSERT_EQ(TEST_PLUGIN_NAME, StdString(Info.PluginName));
+  ASSERT_EQ(TEST_PLUGIN_VERSION, StdString(Info.PluginVersion));
+  ASSERT_NE(nullptr, Info.RegisterPassBuilderCallbacks);
+
+  PassBuilder PB;
+  ModulePassManager PM;
+  ASSERT_FALSE(PB.parsePassPipeline(PM, "plugin-pass"));
+
+  Info.RegisterPassBuilderCallbacks(PB);
+  ASSERT_TRUE(PB.parsePassPipeline(PM, "plugin-pass"));
+}
Index: unittests/Passes/TestPlugin.h
===================================================================
--- /dev/null
+++ unittests/Passes/TestPlugin.h
@@ -0,0 +1,2 @@
+#define TEST_PLUGIN_NAME "TestPlugin"
+#define TEST_PLUGIN_VERSION "0.1-unit"