[llvm] [AMDGPU][doc] Refactor Barrier Execution Model (PR #204566)

[Fabian Ritter via llvm-commits]

================
@@ -272,24 +264,85 @@ The following code sequences can be used to implement the barrier operations def
     ===================== ====================== ===========================================================
 
 GFX12
-+++++
+-----
 
 GFX12 targets have the split-barrier feature, and also allow ``s_barrier`` instructions to use
 one of multiple barrier *objects* available per workgroup. ``s_barrier`` instruction use the
 barrier ID operand to determine the barrier *object* they operate on.
 
 GFX12.5 additionally introduces new barrier *objects* that offer more flexibility for synchronizing the execution
 of a subset of waves of a workgroup, or synchronizing execution across workgroups within a workgroup cluster, via
-``s_barrier``.
+``s_barrier``. These are called "named barriers".
 
 .. note::
 
   Check the :ref:`the table below<amdgpu-execution-synchronization-barriers-sbarrier-ids-gfx12>` to determine
   which barrier IDs are available to ``s_barrier`` instructions on a given target.
 
+.. _amdgpu-execution-synchronization-barriers-execution-model-gfx12-sbarrier:
+
+"Named Barriers" Model Extensions
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+In order to reason about the execution of ``s_barrier`` "named barriers" on GFX12 and up,
----------------
ritter-x2a wrote:

```suggestion
In order to reason about the execution of ``s_barrier`` "named barriers" on GFX12.5 and up,
```
?

https://github.com/llvm/llvm-project/pull/204566