[clang] [clang][AMDGPU] Clean-up handling of named barrier type (PR #207687)

[Sameer Sahasrabuddhe via cfe-commits]

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@@ -30,3 +30,38 @@ Please note that the specific architecture and feature names will vary depending
 
 Clang exposes AMDGPU hardware intrinsics as target-specific builtins with the
 `__builtin_amdgcn_` prefix. These are documented in {doc}`AMDGPUBuiltinReference`.
+
+## Target-Specific Types
+
+### Named Workgroup Barrier Type
+
+The `__amdgpu_named_workgroup_barrier_t` type is used to represent the GFX12.5 named barriers.
+Example usage:
+
+```c
+__amdgpu_named_workgroup_barrier_t x;
+__amdgpu_named_workgroup_barrier_t arr[2]; // Arrays are also fine
+
+void foo(int a)
+{
+  __builtin_amdgcn_s_barrier_init(&x, a);
+}
+```
+
+A "named barrier wrapper" is a class that contains exactly one field, which is either
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ssahasra wrote:

Should the field be non-static?

https://github.com/llvm/llvm-project/pull/207687