[llvm] [AMDGPU] Improve the description of asyncmark semantics (PR #202579)

[Sameer Sahasrabuddhe via llvm-commits]

================
@@ -220,30 +217,96 @@ correctness. But inlining such a call may result in redundant waits.
 .. code-block:: c++
 
    void foo() {
-     asyncmark(); // A
+     ...
+     asyncmark();       // X
+     ...                // no wait.asyncmark()
    }
 
    void bar() {
-     asyncmark(); // B
-     asyncmark(); // C
+     asyncmark();       // B
+     asyncmark();       // C
      foo();
-     wait.asyncmark(1);
+     wait.asyncmark(1); // D
+   }
+
+Before inlining, it is unspecified whether ``X`` is *completed-at* ``D``, while
+``C`` is **not** *completed-at* ``D``. The programmer can only rely on ``B``
+being *completed-at* ``D``.
+
+.. code-block:: c++
+
+   void bar() {
+     asyncmark();       // B
+     asyncmark();       // C
+     asyncmark();       // X
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ssahasra wrote:

Done.

https://github.com/llvm/llvm-project/pull/202579