[AArch64] Function multi-versioning release notes added. NFC.

Differential Revision: https://reviews.llvm.org/D142265

Author: ilinpv

clang/docs/ReleaseNotes.rst

@@ -96,6 +96,17 @@ C++ Language Changes
   disabled with ``-fno-assume-unique-vtables``. This optimization is not yet
   implemented for the MS C++ ABI.
 
+Attribute Changes in Clang
+--------------------------
+- Introduced new attribute ``__attribute__((target_version("cpu_features")))``
+  and expanded the functionality of the existing attribute
+  ``__attribute__((target_clones("cpu_features1","cpu_features2",...)))`` to
+  support Function Multi Versioning on AArch64 target. It detects at runtime
+  which function versions are supported by CPU and calls the one with highest
+  priority. Refer to `clang attributes
+  <https://clang.llvm.org/docs/AttributeReference.html#target-version>`_ for
+  more details.
+
 C++20 Feature Support
 ^^^^^^^^^^^^^^^^^^^^^
 - Implemented the rule introduced by `CA104 <https://wg21.link/P2103R0>`_  for comparison of

llvm/docs/ReleaseNotes.rst

@@ -124,6 +124,10 @@ Changes to the AArch64 Backend
   included in a higher level than what is specified on the command line,
   or for disabling unwanted extensions if setting it to a lower level.
   This fixes `PR32873 <https://github.com/llvm/llvm-project/issues/32220>`.
+* Implemented `Function Multi Versioning
+  <https://arm-software.github.io/acle/main/acle.html#function-multi-versioning>`_
+  in accordance with Arm C Language Extensions specification. Currently in Beta
+  state.
 
 Changes to the AMDGPU Backend
 -----------------------------