[Docs][OpenCL][SPIR-V] Release 15 notes for Clang

[Anastasia]

Summary

Added list of functional changes to release notes.

[Anastasia]

@svenvh as you made quite a lot of changes in the headers feel free to expand the description if you feel we should document some of those in more detail.

[Anastasia]

Minor formatting changes

[svenvh]

In D132473#3742688, @Anastasia wrote:

@svenvh as you made quite a lot of changes in the headers feel free to expand the description if you feel we should document some of those in more detail.

I think you have captured it quite well already; they were mostly small fixes (although many).

clang/docs/ReleaseNotes.rst

676

Should we say anything about opaque pointers? Something like:

- Although LLVM has switched to opaque pointers with this release, SPIR-V generation still relies on typed pointers in this release.

[Anastasia]

• Added clarification about the opaque pointers in SPIR-V.

[Anastasia]

clang/docs/ReleaseNotes.rst

676

Sure, good point! I have added an item to clarify this. Does it look ok to you?

[svenvh]

LGTM, thanks!

clang/docs/ReleaseNotes.rst

676

generation -> generator I'd say, which you can address at commit time. For the rest it looks good!

[Anastasia]

Committed in https://github.com/llvm/llvm-project/commit/5e1b36ced538cfc80f2400b27e346d2175b04092.

clang/docs/ReleaseNotes.rst

 Objective-C Language Changes in Clang
 -------------------------------------
 
-OpenCL C Language Changes in Clang
-----------------------------------
-
-...
+OpenCL Kernel Language Changes in Clang
+---------------------------------------
+
+- Improved/fixed misc issues in the builtin function support and diagnostics.
+- Improved diagnostics for unknown extension pragma, subgroup functions and
+  implicit function prototype.
+- Added ``-cl-ext`` flag to the Clang driver to toggle extensions/features
+  compiled for.
+- Added ``cl_khr_subgroup_rotate`` extension.
+- Removed some ``printf`` and ``hostcall`` related diagnostics when compiling
+  for AMDGPU.
+- Fixed alignment of pointer types in kernel arguments.
 
 ABI Changes in Clang
 --------------------

   Operations found in the :ref:`Clang Language Extensions <Vector Operations>`
   document.
 
+SPIR-V Support in Clang
+-----------------------
+
+- Added flag ``-fintegrated-objemitter`` to enable use of experimental
+  integrated LLVM backend when generating SPIR-V binary.
+- The SPIR-V generation continues to produce typed pointers in this release
+  despite the general switch of LLVM to opaque pointers.
+
 Floating Point Support in Clang
 -------------------------------