[AArch64] Add some release notes items (llvm#79983)

Author: momchil-velikov

clang/docs/ReleaseNotes.rst

@@ -1235,6 +1235,11 @@ Arm and AArch64 Support
  - The C23 ``_BitInt`` implementation has been brought into compliance
    with AAPCS32 and AAPCS64.
 
+- Alpha support has been added for SVE2.1 intrinsics.
+
+- Support has been added for `-fstack-clash-protection` and `-mstack-probe-size`
+  command line options.
+
 - Function Multi Versioning has been extended to support Load-Acquire RCpc
   instructions v3 (rcpc3) as well as Memory Copy and Memory Set Acceleration
   instructions (mops) when targeting AArch64. The feature identifiers (in

llvm/docs/ReleaseNotes.rst

@@ -146,6 +146,14 @@ Changes to the AArch64 Backend
 * Added codegeneration support for ``llvm.ptrauth.auth`` and
   ``llvm.ptrauth.resign`` intrinsics.
 
+* Assembler/disassembler support has been added for 2023 architecture
+  extensions.
+
+* Support has been added for Stack Clash Protection. During function frame
+  creation and dynamic stack allocations, the compiler will issue memory
+  accesses at reguilar intervals so that a guard area at the top of the stack
+  can't be skipped over.
+
 Changes to the AMDGPU Backend
 -----------------------------