clang-cl: Support loading plugins on Windows

This builds on the support being added to LLVM to import and export
registries from DLLs.  This will allow us to pick up the registry
entries added in the DLL's copy of FrontendPluginRegistry.

This will allow us to use plugins on Windows using:
$ clang-cl -Xclang -load -Xclang plugin.dll \
           -Xclang -add-plugin -Xclang foo

llvm-svn: 260265

3 files changed, 13 insertions, 2 deletions

diff --git a/clang/docs/ClangPlugins.rst b/clang/docs/ClangPlugins.rst
index 9a5bc142130..1aeff62e2fd 100644
--- a/clang/docs/ClangPlugins.rst
+++ b/clang/docs/ClangPlugins.rst
@@ -37,11 +37,14 @@ Registering a plugin
 ====================
 
 A plugin is loaded from a dynamic library at runtime by the compiler. To
-register a plugin in a library, use ``FrontendPluginRegistry::Add<>``:
+register a plugin in a library, use ``FrontendPluginRegistry::Add<>``.
+On Windows, you also need to export your plugin registry using
+``LLVM_EXPORT_REGISTRY``.  Here is an example:
 
 .. code-block:: c++
 
   static FrontendPluginRegistry::Add<MyPlugin> X("my-plugin-name", "my plugin description");
+  LLVM_EXPORT_REGISTRY(FrontendPluginRegistry)
 
 Putting it all together
 =======================
diff --git a/clang/examples/PrintFunctionNames/PrintFunctionNames.cpp b/clang/examples/PrintFunctionNames/PrintFunctionNames.cpp
index 9f8f6e3f050..e2834b9ad23 100644
--- a/clang/examples/PrintFunctionNames/PrintFunctionNames.cpp
+++ b/clang/examples/PrintFunctionNames/PrintFunctionNames.cpp
@@ -121,3 +121,4 @@ protected:
 
 static FrontendPluginRegistry::Add<PrintFunctionNamesAction>
 X("print-fns", "print function names");
+LLVM_EXPORT_REGISTRY(FrontendPluginRegistry)
diff --git a/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp b/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp
index 116590e5375..90642abb5d5 100644
--- a/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp
+++ b/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp
@@ -189,9 +189,16 @@ bool clang::ExecuteCompilerInvocation(CompilerInstance *Clang) {
          e = Clang->getFrontendOpts().Plugins.size(); i != e; ++i) {
     const std::string &Path = Clang->getFrontendOpts().Plugins[i];
     std::string Error;
-    if (llvm::sys::DynamicLibrary::LoadLibraryPermanently(Path.c_str(), &Error))
+    llvm::sys::DynamicLibrary DL(
+        llvm::sys::DynamicLibrary::getPermanentLibrary(Path.c_str(), &Error));
+    if (DL.isValid()) {
+      // On Windows, we need to import the plugin front-end action
+      // dynamically.
+      LLVM_IMPORT_REGISTRY(FrontendPluginRegistry, DL);
+    } else {
       Clang->getDiagnostics().Report(diag::err_fe_unable_to_load_plugin)
         << Path << Error;
+    }
   }
 
   // Honor -mllvm.