ReleaseNotes: GVNHoist; by Sepastian Pop

git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_40@295743 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/docs/ReleaseNotes.rst b/docs/ReleaseNotes.rst
index da86be3f96ff7575206286604543289fac462dcc..6efa4813d7703bb7381032a9af3c7a9dcf2b3d0d 100644 (file)
--- a/docs/ReleaseNotes.rst
+++ b/docs/ReleaseNotes.rst
@@ -61,6 +61,13 @@ Non-comprehensive list of changes in this release
   with LLVM option -adce-remove-loops when the loop body otherwise has
   no live operations.
 
+* The GVNHoist pass is now enabled by default. The new pass based on Global
+  Value Numbering detects similar computations in branch code and replaces
+  multiple instances of the same computation with a unique expression.  The
+  transform benefits code size and generates better schedules.  GVNHoist is
+  more aggressive at -Os and -Oz, hoisting more expressions at the expense of
+  execution time degradations.
+
  * The llvm-cov tool can now export coverage data as json. Its html output mode
    has also improved.