add some notes

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145135 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/docs/ReleaseNotes.html b/docs/ReleaseNotes.html
index 68bd0f4aa10ad1b77c159366450fb793b1936567..8b533e62a43002b6deb916ed31c839b182b71b2d 100644 (file)
--- a/docs/ReleaseNotes.html
+++ b/docs/ReleaseNotes.html
@@ -752,6 +752,9 @@ be used to verify some algorithms.
  Better code generation for Cortex-A9
  Many APIs take ArrayRef's now.
  Pass manager extension API.
+
+
+Information about branch probability and basic block frequency is now available within LLVM based on a combination of static branch prediction heuristics and __builtin_expect calls.  That information is currently used for register spill placement and if-conversion, with additional optimizations planned for future releases.  The same frameworks are intended for eventual use with profile-guided optimization, but that is not yet implemented.
  
  -->