Update llvm::Registry to work for LLVM shared library builds on windows (#109024)

This is part of the effort to support for enabling plugins on windows by
adding better support for building llvm and clang as a DLL.

Since windows doesn't implicitly import and merge exported symbols
across shared libraries like other platforms we need to explicitly add a
extern template declaration for each instantiation of llvm::Registry to
force the registry symbols to be dllimport'ed.
I've added a new visibility macro that doesn't switch between dllimport
and dllexport on windows since the existing macro would be in the wrong
mode for llvm::Registry's declared in Clang. This PR also depends Clang
symbol visibility macros that will be added by #108276

---------

Co-authored-by: Saleem Abdulrasool <[email protected]>

Author: fsfod

clang/include/clang/Basic/ParsedAttrInfo.h

@@ -17,6 +17,7 @@
 
 #include "clang/Basic/AttrSubjectMatchRules.h"
 #include "clang/Basic/AttributeCommonInfo.h"
+#include "clang/Support/Compiler.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/Support/Registry.h"
 #include <climits>
@@ -175,4 +176,8 @@ const std::list<std::unique_ptr<ParsedAttrInfo>> &getAttributePluginInstances();
 
 } // namespace clang
 
+namespace llvm {
+extern template class CLANG_TEMPLATE_ABI Registry<clang::ParsedAttrInfo>;
+} // namespace llvm
+
 #endif // LLVM_CLANG_BASIC_PARSEDATTRINFO_H

clang/include/clang/Frontend/FrontendPluginRegistry.h

@@ -14,6 +14,7 @@
 #define LLVM_CLANG_FRONTEND_FRONTENDPLUGINREGISTRY_H
 
 #include "clang/Frontend/FrontendAction.h"
+#include "clang/Support/Compiler.h"
 #include "llvm/Support/Registry.h"
 
 namespace clang {
@@ -23,4 +24,8 @@ using FrontendPluginRegistry = llvm::Registry<PluginASTAction>;
 
 } // namespace clang
 
+namespace llvm {
+extern template class CLANG_TEMPLATE_ABI Registry<clang::PluginASTAction>;
+} // namespace llvm
+
 #endif // LLVM_CLANG_FRONTEND_FRONTENDPLUGINREGISTRY_H

clang/include/clang/Lex/Preprocessor.h

@@ -32,6 +32,7 @@
 #include "clang/Lex/PPEmbedParameters.h"
 #include "clang/Lex/Token.h"
 #include "clang/Lex/TokenLexer.h"
+#include "clang/Support/Compiler.h"
 #include "llvm/ADT/APSInt.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/DenseMap.h"
@@ -3060,4 +3061,8 @@ using PragmaHandlerRegistry = llvm::Registry<PragmaHandler>;
 
 } // namespace clang
 
+namespace llvm {
+extern template class CLANG_TEMPLATE_ABI Registry<clang::PragmaHandler>;
+} // namespace llvm
+
 #endif // LLVM_CLANG_LEX_PREPROCESSOR_H

clang/include/clang/Tooling/CompilationDatabasePluginRegistry.h

@@ -9,6 +9,7 @@
 #ifndef LLVM_CLANG_TOOLING_COMPILATIONDATABASEPLUGINREGISTRY_H
 #define LLVM_CLANG_TOOLING_COMPILATIONDATABASEPLUGINREGISTRY_H
 
+#include "clang/Support/Compiler.h"
 #include "clang/Tooling/CompilationDatabase.h"
 #include "llvm/Support/Registry.h"
 
@@ -42,4 +43,9 @@ using CompilationDatabasePluginRegistry =
 } // namespace tooling
 } // namespace clang
 
+namespace llvm {
+extern template class CLANG_TEMPLATE_ABI
+    Registry<clang::tooling::CompilationDatabasePlugin>;
+} // namespace llvm
+
 #endif // LLVM_CLANG_TOOLING_COMPILATIONDATABASEPLUGINREGISTRY_H

clang/include/clang/Tooling/ToolExecutorPluginRegistry.h

@@ -9,6 +9,7 @@
 #ifndef LLVM_CLANG_TOOLING_TOOLEXECUTORPLUGINREGISTRY_H
 #define LLVM_CLANG_TOOLING_TOOLEXECUTORPLUGINREGISTRY_H
 
+#include "clang/Support/Compiler.h"
 #include "clang/Tooling/Execution.h"
 #include "llvm/Support/Registry.h"
 
@@ -20,4 +21,9 @@ using ToolExecutorPluginRegistry = llvm::Registry<ToolExecutorPlugin>;
 } // namespace tooling
 } // namespace clang
 
+namespace llvm {
+extern template class CLANG_TEMPLATE_ABI
+    Registry<clang::tooling::ToolExecutorPlugin>;
+} // namespace llvm
+
 #endif // LLVM_CLANG_TOOLING_TOOLEXECUTORPLUGINREGISTRY_H

llvm/include/llvm/CodeGen/GCMetadataPrinter.h

@@ -34,6 +34,8 @@ class StackMaps;
 /// defaults from Registry.
 using GCMetadataPrinterRegistry = Registry<GCMetadataPrinter>;
 
+extern template class LLVM_TEMPLATE_ABI Registry<GCMetadataPrinter>;
+
 /// GCMetadataPrinter - Emits GC metadata as assembly code.  Instances are
 /// created, managed, and owned by the AsmPrinter.
 class GCMetadataPrinter {

llvm/include/llvm/IR/GCStrategy.h

@@ -141,6 +141,8 @@ class GCStrategy {
 /// GCMetadataPrinterRegistery as well.
 using GCRegistry = Registry<GCStrategy>;
 
+extern template class LLVM_TEMPLATE_ABI Registry<GCStrategy>;
+
 /// Lookup the GCStrategy object associated with the given gc name.
 std::unique_ptr<GCStrategy> getGCStrategy(const StringRef Name);
 

llvm/include/llvm/Support/Compiler.h

@@ -153,6 +153,12 @@
 /// exported when llvm is built as a shared library with everything else that is
 /// unannotated will have internal visibility.
 ///
+/// LLVM_ABI_EXPORT is for the special case for things like plugin symbol
+/// declarations or definitions where we don't want the macro to be switching
+/// between dllexport and dllimport on windows based on what codebase is being
+/// built, it will only be dllexport. For non windows platforms this macro
+/// behaves the same as LLVM_ABI.
+///
 /// LLVM_EXPORT_TEMPLATE is used on explicit template instantiations in source
 /// files that were declared extern in a header. This macro is only set as a
 /// compiler export attribute on windows, on other platforms it does nothing.
@@ -179,6 +185,7 @@
 #define LLVM_ABI
 #define LLVM_TEMPLATE_ABI
 #define LLVM_EXPORT_TEMPLATE
+#define LLVM_ABI_EXPORT
 #elif defined(_WIN32) && !defined(__MINGW32__)
 #if defined(LLVM_EXPORTS)
 #define LLVM_ABI __declspec(dllexport)
@@ -189,19 +196,23 @@
 #define LLVM_TEMPLATE_ABI __declspec(dllimport)
 #define LLVM_EXPORT_TEMPLATE
 #endif
+#define LLVM_ABI_EXPORT __declspec(dllexport)
 #elif defined(__ELF__) || defined(__MINGW32__) || defined(_AIX)
 #define LLVM_ABI LLVM_ATTRIBUTE_VISIBILITY_DEFAULT
 #define LLVM_TEMPLATE_ABI LLVM_ATTRIBUTE_VISIBILITY_DEFAULT
 #define LLVM_EXPORT_TEMPLATE
+#define LLVM_ABI_EXPORT LLVM_ATTRIBUTE_VISIBILITY_DEFAULT
 #elif defined(__MACH__) || defined(__WASM__)
 #define LLVM_ABI LLVM_ATTRIBUTE_VISIBILITY_DEFAULT
 #define LLVM_TEMPLATE_ABI
 #define LLVM_EXPORT_TEMPLATE
+#define LLVM_ABI_EXPORT LLVM_ATTRIBUTE_VISIBILITY_DEFAULT
 #endif
 #else
 #define LLVM_ABI
 #define LLVM_TEMPLATE_ABI
 #define LLVM_EXPORT_TEMPLATE
+#define LLVM_ABI_EXPORT
 #endif
 #define LLVM_C_ABI LLVM_ABI
 #endif

llvm/include/llvm/Support/Registry.h

@@ -53,7 +53,13 @@ namespace llvm {
     Registry() = delete;
 
     friend class node;
-    static node *Head, *Tail;
+    // These must be must two separate declarations to workaround a 20 year
+    // old MSVC bug with dllexport and multiple static fields in the same
+    // declaration causing error C2487 "member of dll interface class may not
+    // be declared with dll interface".
+    // https://developercommunity.visualstudio.com/t/c2487-in-dllexport-class-with-static-members/69878
+    static node *Head;
+    static node *Tail;
 
   public:
     /// Node in linked list of entries.
@@ -76,7 +82,13 @@ namespace llvm {
     /// add a node to the executable's registry. Therefore it's not defined here
     /// to avoid it being instantiated in the plugin and is instead defined in
     /// the executable (see LLVM_INSTANTIATE_REGISTRY below).
-    static void add_node(node *N);
+    static void add_node(node *N) {
+      if (Tail)
+        Tail->Next = N;
+      else
+        Head = N;
+      Tail = N;
+    }
 
     /// Iterators for registry entries.
     ///
@@ -95,7 +107,7 @@ namespace llvm {
 
     // begin is not defined here in order to avoid usage of an undefined static
     // data member, instead it's instantiated by LLVM_INSTANTIATE_REGISTRY.
-    static iterator begin();
+    static iterator begin() { return iterator(Head); }
     static iterator end()   { return iterator(nullptr); }
 
     static iterator_range<iterator> entries() {
@@ -124,36 +136,28 @@ namespace llvm {
       }
     };
   };
+
 } // end namespace llvm
 
+#ifdef _WIN32
 /// Instantiate a registry class.
-///
-/// This provides template definitions of add_node, begin, and the Head and Tail
-/// pointers, then explicitly instantiates them. We could explicitly specialize
-/// them, instead of the two-step process of define then instantiate, but
-/// strictly speaking that's not allowed by the C++ standard (we would need to
-/// have explicit specialization declarations in all translation units where the
-/// specialization is used) so we don't.
-#define LLVM_INSTANTIATE_REGISTRY(REGISTRY_CLASS) \
-  namespace llvm { \
-  template<typename T> typename Registry<T>::node *Registry<T>::Head = nullptr;\
-  template<typename T> typename Registry<T>::node *Registry<T>::Tail = nullptr;\
-  template<typename T> \
-  void Registry<T>::add_node(typename Registry<T>::node *N) { \
-    if (Tail) \
-      Tail->Next = N; \
-    else \
-      Head = N; \
-    Tail = N; \
-  } \
-  template<typename T> typename Registry<T>::iterator Registry<T>::begin() { \
-    return iterator(Head); \
-  } \
-  template REGISTRY_CLASS::node *Registry<REGISTRY_CLASS::type>::Head; \
-  template REGISTRY_CLASS::node *Registry<REGISTRY_CLASS::type>::Tail; \
-  template \
-  void Registry<REGISTRY_CLASS::type>::add_node(REGISTRY_CLASS::node*); \
-  template REGISTRY_CLASS::iterator Registry<REGISTRY_CLASS::type>::begin(); \
+#define LLVM_INSTANTIATE_REGISTRY(REGISTRY_CLASS)                              \
+  namespace llvm {                                                             \
+  template <typename T>                                                        \
+  typename Registry<T>::node *Registry<T>::Head = nullptr;                     \
+  template <typename T>                                                        \
+  typename Registry<T>::node *Registry<T>::Tail = nullptr;                     \
+  template class LLVM_ABI_EXPORT Registry<REGISTRY_CLASS::type>;               \
+  }
+#else
+#define LLVM_INSTANTIATE_REGISTRY(REGISTRY_CLASS)                              \
+  namespace llvm {                                                             \
+  template <typename T>                                                        \
+  typename Registry<T>::node *Registry<T>::Head = nullptr;                     \
+  template <typename T>                                                        \
+  typename Registry<T>::node *Registry<T>::Tail = nullptr;                     \
+  template class Registry<REGISTRY_CLASS::type>;                               \
   }
+#endif
 
 #endif // LLVM_SUPPORT_REGISTRY_H