DebugInfo: provide the ability to add members to a class after it has been constructed

This is necessary to allow Clang to only emit implicit members when
there is code generated for them, rather than whenever they are ODR
used.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188082 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/IR/DebugInfo.cpp b/lib/IR/DebugInfo.cpp
index fc93249..0f7ddb5 100644
--- a/lib/IR/DebugInfo.cpp
+++ b/lib/IR/DebugInfo.cpp
@@ -647,6 +647,19 @@
   DbgNode = N;
 }
 
+void DICompositeType::addMember(DISubprogram S) {
+  SmallVector<llvm::Value *, 16> M;
+  DIArray OrigM = getTypeArray();
+  unsigned Elements = OrigM.getNumElements();
+  if (Elements == 1 && !OrigM.getElement(0))
+    Elements = 0;
+  M.reserve(Elements + 1);
+  for (unsigned i = 0; i != Elements; ++i)
+    M.push_back(OrigM.getElement(i));
+  M.push_back(S);
+  setTypeArray(DIArray(MDNode::get(DbgNode->getContext(), M)));
+}
+
 /// \brief Set the containing type.
 void DICompositeType::setContainingType(DICompositeType ContainingType) {
   TrackingVH<MDNode> N(*this);