Move the logic to avoid double global emission from Sema to CodeGen

Reverts the code changes from r234675 but keeps the test case.

We were already maintaining a DenseMap of globals with dynamic
initializers anyway.

Fixes the test case from PR23234.

llvm-svn: 234961
diff --git a/clang/lib/CodeGen/CodeGenModule.h b/clang/lib/CodeGen/CodeGenModule.h
index e5e52b5..feef6c2 100644
--- a/clang/lib/CodeGen/CodeGenModule.h
+++ b/clang/lib/CodeGen/CodeGenModule.h
@@ -400,7 +400,8 @@
   /// When a C++ decl with an initializer is deferred, null is
   /// appended to CXXGlobalInits, and the index of that null is placed
   /// here so that the initializer will be performed in the correct
-  /// order.
+  /// order. Once the decl is emitted, the index is replaced with ~0U to ensure
+  /// that we don't re-emit the initializer.
   llvm::DenseMap<const Decl*, unsigned> DelayedCXXInitPosition;
   
   typedef std::pair<OrderGlobalInits, llvm::Function*> GlobalInitData;