Index: cmake/modules/HandleLLVMOptions.cmake
===================================================================
--- cmake/modules/HandleLLVMOptions.cmake
+++ cmake/modules/HandleLLVMOptions.cmake
@@ -643,12 +643,4 @@
 
 # Plugin support
 # FIXME: Make this configurable.
-if(WIN32 OR CYGWIN)
-  if(BUILD_SHARED_LIBS)
-    set(LLVM_ENABLE_PLUGINS ON)
-  else()
-    set(LLVM_ENABLE_PLUGINS OFF)
-  endif()
-else()
-  set(LLVM_ENABLE_PLUGINS ON)
-endif()
+set(LLVM_ENABLE_PLUGINS ON)
Index: include/llvm/Support/Registry.h
===================================================================
--- include/llvm/Support/Registry.h
+++ include/llvm/Support/Registry.h
@@ -135,12 +135,17 @@
         // current Registry.
         typedef std::pair<const node *, const node *> Info;
         Info *I = static_cast<Info *>(Getter());
-        iterator begin(I->first);
-        iterator end(I->second);
-        for (++end; begin != end; ++begin) {
-          // This Node object needs to remain alive for the
-          // duration of the program.
-          add_node(new node(*begin));
+        // We need to check I->first != Head for mingw, which build DLLs
+        // sharing extern symbols when using LLVM_BUILD_SHARED, so we don't
+        // copy the Registry in itself.
+        if (I->first != nullptr && I->first != Head) {
+          iterator begin(I->first);
+          iterator end(I->second);
+          for (++end; begin != end; ++begin) {
+            // This Node object needs to remain alive for the
+            // duration of the program.
+            add_node(new node(*begin));
+          }
         }
       }
     }