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 68bd0f4..8b533e6 100644
--- a/docs/ReleaseNotes.html
+++ b/docs/ReleaseNotes.html
@@ -752,6 +752,9 @@
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.
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