Add some comments to r184252.

rdar://problem/14101097

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@184259 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGDebugInfo.cpp b/lib/CodeGen/CGDebugInfo.cpp
index a5e9e4e..563faa4 100644
--- a/lib/CodeGen/CGDebugInfo.cpp
+++ b/lib/CodeGen/CGDebugInfo.cpp
@@ -1379,7 +1379,12 @@
 /// CreateType - get structure or union type.
 llvm::DIType CGDebugInfo::CreateType(const RecordType *Ty, bool Declaration) {
   RecordDecl *RD = Ty->getDecl();
+  // Limited debug info should only remove struct definitions that can
+  // safely be replaced by a forward declaration in the source code.
   if (DebugKind <= CodeGenOptions::LimitedDebugInfo && Declaration) {
+    // FIXME: This implementation is problematic; there are some test
+    // cases where we violate the above principle, such as
+    // test/CodeGen/debug-info-records.c .
     llvm::DIDescriptor FDContext =
       getContextDescriptor(cast<Decl>(RD->getDeclContext()));
     llvm::DIType RetTy = createRecordFwdDecl(RD, FDContext);