[PassManagerBuilder] Remove global extension when a plugin is unloaded

This commit fixes PR39321.

GlobalExtensions is not guaranteed to be destroyed when optimizer plugins are unloaded. If it is indeed destroyed after a plugin is dlclose-d, the destructor of the corresponding ExtensionFn is not mapped anymore, causing a call to unmapped memory during destruction.

This commit guarantees that extensions coming from external plugins are removed from GlobalExtensions when the plugin is unloaded if GlobalExtensions has not been destroyed yet.

Differential Revision: https://reviews.llvm.org/D71959

(cherry picked from commit ab2300bc154f7bed43f85f74fd3fe31be71d90e0)

1 files changed, 25 insertions, 3 deletions

diff --git a/llvm/include/llvm/Transforms/IPO/PassManagerBuilder.h b/llvm/include/llvm/Transforms/IPO/PassManagerBuilder.h
index 63ff00afc2a..ababa1d61f6 100644
--- a/llvm/include/llvm/Transforms/IPO/PassManagerBuilder.h
+++ b/llvm/include/llvm/Transforms/IPO/PassManagerBuilder.h
@@ -62,6 +62,8 @@ public:
   typedef std::function<void(const PassManagerBuilder &Builder,
                              legacy::PassManagerBase &PM)>
       ExtensionFn;
+  typedef int GlobalExtensionID;
+
   enum ExtensionPointTy {
     /// EP_EarlyAsPossible - This extension point allows adding passes before
     /// any other transformations, allowing them to see the code as it is coming
@@ -193,7 +195,17 @@ public:
   /// Adds an extension that will be used by all PassManagerBuilder instances.
   /// This is intended to be used by plugins, to register a set of
   /// optimisations to run automatically.
-  static void addGlobalExtension(ExtensionPointTy Ty, ExtensionFn Fn);
+  ///
+  /// \returns A global extension identifier that can be used to remove the
+  /// extension.
+  static GlobalExtensionID addGlobalExtension(ExtensionPointTy Ty,
+                                              ExtensionFn Fn);
+  /// Removes an extension that was previously added using addGlobalExtension.
+  /// This is also intended to be used by plugins, to remove any extension that
+  /// was previously registered before being unloaded.
+  ///
+  /// \param ExtensionID Identifier of the extension to be removed.
+  static void removeGlobalExtension(GlobalExtensionID ExtensionID);
   void addExtension(ExtensionPointTy Ty, ExtensionFn Fn);
 
 private:
@@ -222,10 +234,20 @@ public:
 /// used by optimizer plugins to allow all front ends to transparently use
 /// them.  Create a static instance of this class in your plugin, providing a
 /// private function that the PassManagerBuilder can use to add your passes.
-struct RegisterStandardPasses {
+class RegisterStandardPasses {
+  PassManagerBuilder::GlobalExtensionID ExtensionID;
+
+public:
   RegisterStandardPasses(PassManagerBuilder::ExtensionPointTy Ty,
                          PassManagerBuilder::ExtensionFn Fn) {
-    PassManagerBuilder::addGlobalExtension(Ty, std::move(Fn));
+    ExtensionID = PassManagerBuilder::addGlobalExtension(Ty, std::move(Fn));
+  }
+
+  ~RegisterStandardPasses() {
+    // If the collection holding the global extensions is destroyed after the
+    // plugin is unloaded, the extension has to be removed here. Indeed, the
+    // destructor of the ExtensionFn may reference code in the plugin.
+    PassManagerBuilder::removeGlobalExtension(ExtensionID);
   }
 };