DebugInfo: more support for mutating DICompositeType to reduce magic number usage in Clang

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178090 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/IR/DebugInfo.cpp b/lib/IR/DebugInfo.cpp
index 1916f5e..b74522f 100644
--- a/lib/IR/DebugInfo.cpp
+++ b/lib/IR/DebugInfo.cpp
@@ -616,7 +616,7 @@
   return dyn_cast_or_null<MDNode>(DbgNode->getOperand(10));
 }
 
-/// \brief Set the array of member DITypes
+/// \brief Set the array of member DITypes.
 void DICompositeType::setTypeArray(DIArray Elements, DIArray TParams) {
   assert(!TParams || DbgNode->getNumOperands() == 14 && "If you're setting the template parameters this should include a slot for that");
   TrackingVH<MDNode> N(*this);
@@ -626,6 +626,13 @@
   DbgNode = N;
 }
 
+/// \brief Set the containing type.
+void DICompositeType::setContainingType(DICompositeType ContainingType) {
+  TrackingVH<MDNode> N(*this);
+  N->replaceOperandWith(12, ContainingType);
+  DbgNode = N;
+}
+
 /// isInlinedFnArgument - Return true if this variable provides debugging
 /// information for an inlined function arguments.
 bool DIVariable::isInlinedFnArgument(const Function *CurFn) {