[docs] Mention that the legacy PM is deprecated and will be removed after 14

Per https://lists.llvm.org/pipermail/llvm-dev/2021-August/152305.html.

Reviewed By: MaskRay, fhahn

Differential Revision: https://reviews.llvm.org/D109080

diff --git a/llvm/docs/ReleaseNotes.rst b/llvm/docs/ReleaseNotes.rst
index 3364766..6408f63 100644 (file)
--- a/llvm/docs/ReleaseNotes.rst
+++ b/llvm/docs/ReleaseNotes.rst
@@ -56,7 +56,9 @@ Non-comprehensive list of changes in this release
 Changes to the LLVM IR
 ----------------------
 
-* ...
+* Using the legacy pass manager for the optimization pipeline is deprecated and
+  will be removed after LLVM 14. In the meantime, only minimal effort will be
+  made to maintain the legacy pass manager for the optimization pipeline.
 
 Changes to building LLVM
 ------------------------