Use comdats to avoid double initialization of weak data

Initializers of global data that can appear multiple TUs (static data
members of class templates or __declspec(selectany) data) are now in a
comdat group keyed on the global variable being initialized.  On
non-Windows platforms, this is a code size and startup time
optimization.  On Windows, this is necessary for ABI compatibility with
MSVC.

Fixes PR16959.

Reviewers: rsmith

Differential Revision: http://reviews.llvm.org/D3811

llvm-svn: 209555

1 files changed, 15 insertions, 3 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.h b/clang/lib/CodeGen/CodeGenModule.h
index eff51cea8bd..9e5835132ae 100644
--- a/clang/lib/CodeGen/CodeGenModule.h
+++ b/clang/lib/CodeGen/CodeGenModule.h
@@ -233,7 +233,18 @@ class CodeGenModule : public CodeGenTypeCache {
   CodeGenModule(const CodeGenModule &) LLVM_DELETED_FUNCTION;
   void operator=(const CodeGenModule &) LLVM_DELETED_FUNCTION;
 
-  typedef std::vector<std::pair<llvm::Constant*, int> > CtorList;
+  struct Structor {
+    Structor() : Priority(0), Initializer(nullptr), AssociatedData(nullptr) {}
+    Structor(int Priority, llvm::Constant *Initializer,
+             llvm::Constant *AssociatedData)
+        : Priority(Priority), Initializer(Initializer),
+          AssociatedData(AssociatedData) {}
+    int Priority;
+    llvm::Constant *Initializer;
+    llvm::Constant *AssociatedData;
+  };
+
+  typedef std::vector<Structor> CtorList;
 
   ASTContext &Context;
   const LangOptions &LangOpts;
@@ -1081,8 +1092,9 @@ private:
                                     bool PerformInit);
 
   // FIXME: Hardcoding priority here is gross.
-  void AddGlobalCtor(llvm::Function *Ctor, int Priority=65535);
-  void AddGlobalDtor(llvm::Function *Dtor, int Priority=65535);
+  void AddGlobalCtor(llvm::Function *Ctor, int Priority = 65535,
+                     llvm::Constant *AssociatedData = 0);
+  void AddGlobalDtor(llvm::Function *Dtor, int Priority = 65535);
 
   /// Generates a global array of functions and priorities using the given list
   /// and name. This array will have appending linkage and is suitable for use