Revert "DebugInfo: remove unused helper function getDICompositeType."

This reverts commit r185876 as the functions appear to still be used
by dragonegg.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185890 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/IR/DebugInfo.cpp b/lib/IR/DebugInfo.cpp
index c55d68f..25d4ea4 100644
--- a/lib/IR/DebugInfo.cpp
+++ b/lib/IR/DebugInfo.cpp
@@ -844,6 +844,17 @@
   return DISubprogram();
 }
 
+/// getDICompositeType - Find underlying composite type.
+DICompositeType llvm::getDICompositeType(DIType T) {
+  if (T.isCompositeType())
+    return DICompositeType(T);
+
+  if (T.isDerivedType())
+    return getDICompositeType(DIDerivedType(T).getTypeDerivedFrom());
+
+  return DICompositeType();
+}
+
 /// isSubprogramContext - Return true if Context is either a subprogram
 /// or another context nested inside a subprogram.
 bool llvm::isSubprogramContext(const MDNode *Context) {