Add a comment about the DIDescriptor class hierarchy.

llvm-svn: 205358

1 files changed, 4 insertions, 2 deletions

diff --git a/llvm/lib/IR/DebugInfo.cpp b/llvm/lib/IR/DebugInfo.cpp
index f9bc63b389e..c9d68afa445 100644
--- a/llvm/lib/IR/DebugInfo.cpp
+++ b/llvm/lib/IR/DebugInfo.cpp
@@ -429,8 +429,10 @@ static bool fieldIsTypeRef(const MDNode *DbgNode, unsigned Elt) {
 /// Check if a value can be a ScopeRef.
 static bool isScopeRef(const Value *Val) {
   return !Val ||
-         (isa<MDString>(Val) && !cast<MDString>(Val)->getString().empty()) ||
-         isa<MDNode>(Val);
+    (isa<MDString>(Val) && !cast<MDString>(Val)->getString().empty()) ||
+    // Not checking for Val->isScope() here, because it would work
+    // only for lexical scopes and not all subclasses of DIScope.
+    isa<MDNode>(Val);
 }
 
 /// Check if a field at position Elt of a MDNode can be a ScopeRef.