diff --git a/llvm/include/llvm/DebugInfo/DIContext.h b/llvm/include/llvm/DebugInfo/DIContext.h
--- a/llvm/include/llvm/DebugInfo/DIContext.h
+++ b/llvm/include/llvm/DebugInfo/DIContext.h
@@ -90,6 +90,8 @@
 public:
   DIInliningInfo() = default;
 
+  /// Returns the frame at `Index`. Frames are stored in bottom-up, i.e.
+  /// leaf-to-root order with increasing index.
   const DILineInfo &getFrame(unsigned Index) const {
     assert(Index < Frames.size());
     return Frames[Index];