add a note


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@27823 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/ReleaseNotes.html b/docs/ReleaseNotes.html
index d0b77b8a..483147a 100644
--- a/docs/ReleaseNotes.html
+++ b/docs/ReleaseNotes.html
@@ -711,7 +711,8 @@
 <div class="doc_text">
 
 <ul>
-<li>None yet</li>
+<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32), it does not
+    support the 64-bit SPARC ABI (-m64).</li>
 </ul>
 
 </div>