Index: docs/ReleaseNotes.rst
===================================================================
--- docs/ReleaseNotes.rst
+++ docs/ReleaseNotes.rst
@@ -63,9 +63,16 @@
            indirect(a, n);
        }
 
-
 -  ...
 
+Improvements to ThinLTO (-flto=thin)
+------------------------------------
+- Integration with profile data (PGO). When available, profile data enables
+  more accurate function importing decisions, as well as cross-module indirect
+  call promotion.
+- Significant build-time and binary-size improvements when compiling with debug
+  info (-g).
+
 Improvements to Clang's diagnostics
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^