[llvm] [AMDGPU][Doc] GFX12.5 Barrier Execution Model (PR #185632)

[Sameer Sahasrabuddhe via llvm-commits]

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@@ -6767,117 +6789,155 @@ Execution Barriers
 
 .. note::
 
-  This specification is a work-in-progress (see lines annotated with :sup:`WIP`), and is not complete for GFX12.5.
+  The barrier execution model is experimental and subject to change.
 
 Threads can synchronize execution by performing barrier operations on barrier *objects* as described below:
 
 * Each barrier *object* has the following state:
 
-  * An unsigned positive integer *expected count*: counts the number of *signal* operations
+  * An unsigned positive integer *expected count*: counts the number of *arrive* operations
     expected for this barrier *object*.
-  * An unsigned non-negative integer *signal count*: counts the number of *signal* operations
+  * An unsigned non-negative integer *arrive count*: counts the number of *arrive* operations
     already performed on this barrier *object*.
 
-      * The initial value of *signal count* is zero.
-      * When an operation causes *signal count* to be equal to *expected count*, the barrier is completed,
-        and the *signal count* is reset to zero.
+      * The initial value of *arrive count* is zero.
+      * When an operation causes *arrive count* to be equal to *expected count*, the barrier is completed,
+        and the *arrive count* is reset to zero.
 
+* *Barrier-mutually-exclusive* is a symmetric relation between barrier *objects* that represents barrier
+  *objects* that share resources in a way that prevents a thread from using them at the same time.
 * Barrier operations are performed on barrier *objects*. A barrier operation is a dynamic instance
   of one of the following:
 
-  * Barrier *init*.
+  * Barrier *init*
+
+    * Barrier *init* takes an additional unsigned positive integer argument *k*.
+    * Sets the *expected count* of the *barrier object* to *k*.
+    * Resets the *arrive count* of the *barrier object* to zero.
+
   * Barrier *join*.
-  * Barrier *leave*.
+  * Barrier *drop*.
 
     * Decrements *expected count* of the barrier *object* by one.
 
-  * Barrier *signal*.
+  * Barrier *arrive*.
 
-    * Increments *signal count* of the barrier *object* by one.
+    * Increments the *arrive count* of the barrier *object* by one.
+    * Depending on the implementation, *arrive* can also update the *expected count* of the
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ssahasra wrote:

```suggestion
    * If supported, an additional argument to *arrive* can also be used to update the *expected count* of the
```

https://github.com/llvm/llvm-project/pull/185632