Index: include/llvm/Support/DynamicLibrary.h
===================================================================
--- include/llvm/Support/DynamicLibrary.h
+++ include/llvm/Support/DynamicLibrary.h
@@ -68,6 +68,14 @@
     static DynamicLibrary getPermanentLibrary(const char *filename,
                                               std::string *errMsg = nullptr);
 
+    /// Registers an externally loaded library. The library will be unloaded
+    /// when the program terminates.
+    ///
+    /// It is safe to call this function multiple times for the same library.
+    ///
+    /// \returns An empty \p DynamicLibrary on failure.
+    static DynamicLibrary addPermanentLibrary(void *handle);
+
     /// This function permanently loads the dynamic library at the given path.
     /// Use this instead of getPermanentLibrary() when you won't need to get
     /// symbols from the library itself.
Index: lib/Support/DynamicLibrary.cpp
===================================================================
--- lib/Support/DynamicLibrary.cpp
+++ lib/Support/DynamicLibrary.cpp
@@ -53,12 +53,15 @@
 
 DynamicLibrary DynamicLibrary::getPermanentLibrary(const char *filename,
                                                    std::string *errMsg) {
-  SmartScopedLock<true> lock(*SymbolsMutex);
+  void *handle = nullptr;
+  {
+    SmartScopedLock<true> lock(*SymbolsMutex);
 
-  void *handle = dlopen(filename, RTLD_LAZY|RTLD_GLOBAL);
-  if (!handle) {
-    if (errMsg) *errMsg = dlerror();
-    return DynamicLibrary();
+    void *handle = dlopen(filename, RTLD_LAZY|RTLD_GLOBAL);
+    if (!handle) {
+      if (errMsg) *errMsg = dlerror();
+      return DynamicLibrary();
+    }
   }
 
 #ifdef __CYGWIN__
@@ -67,14 +70,25 @@
   if (!filename)
     handle = RTLD_DEFAULT;
 #endif
-
-  if (!OpenedHandles)
-    OpenedHandles = new DenseSet<void *>();
-
+  DynamicLibrary dyLib = addPermanentLibrary(handle);
   // If we've already loaded this library, dlclose() the handle in order to
   // keep the internal refcount at +1.
-  if (!OpenedHandles->insert(handle).second)
+  if (!dyLib.isValid()) {
+    if (errMsg)
+      *errMsg = std::string(filename) + ": Library already registered";
+    SmartScopedLock<true> lock(*SymbolsMutex);
     dlclose(handle);
+  }
+
+  return dyLib;
+}
+
+DynamicLibrary DynamicLibrary::addPermanentLibrary(void *handle) {
+  SmartScopedLock<true> lock(*SymbolsMutex);
+
+  // If we've already loaded this library, tell the caller.
+  if (!OpenedHandles->insert(handle).second)
+    return DynamicLibrary();
 
   return DynamicLibrary(handle);
 }
Index: lib/Support/Windows/DynamicLibrary.inc
===================================================================
--- lib/Support/Windows/DynamicLibrary.inc
+++ lib/Support/Windows/DynamicLibrary.inc
@@ -89,15 +89,27 @@
     return DynamicLibrary();
   }
 
-  if (OpenedHandles == 0)
-    OpenedHandles = new DenseSet<HMODULE>();
-
+  DynamicLibrary dyLib = addPermanentLibrary(a_handle);
   // If we've already loaded this library, FreeLibrary() the handle in order to
   // keep the internal refcount at +1.
-  if (!OpenedHandles->insert(a_handle).second)
+  if (!dyLib.isValid()) {
+    MakeErrMsg(errMsg, std::string(filename) + ": Already loaded");
     FreeLibrary(a_handle);
+  }
+
+  return dyLib;
+}
+
+DynamicLibrary DynamicLibrary::addPermanentLibrary(void *handle) {
+  SmartScopedLock<true> lock(*SymbolsMutex);
+  if (OpenedHandles == 0)
+    OpenedHandles = new DenseSet<HMODULE>();
+
+  // If we've already loaded this library, tell the caller.
+  if (!OpenedHandles->insert((const HMODULE)handle).second)
+    return DynamicLibrary();
 
-  return DynamicLibrary(a_handle);
+  return DynamicLibrary((HMODULE)handle);
 }
 
 // Stack probing routines are in the support library (e.g. libgcc), but we don't