Fix GCC build.

llvm-svn: 260317
diff --git a/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp b/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
index 92f119b..e131326 100644
--- a/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
+++ b/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
@@ -177,6 +177,8 @@
 
 }
 
+namespace llvm {
+
 template <> struct DenseMapInfo<VTableSlot> {
   static VTableSlot getEmptyKey() {
     return {DenseMapInfo<Metadata *>::getEmptyKey(),
@@ -196,6 +198,8 @@
   }
 };
 
+}
+
 namespace {
 
 // A virtual call site. VTable is the loaded virtual table pointer, and CS is