[clang] [llvm] [HLSL] Add `Increment`/`DecrementCounter` methods to structured buffers (PR #114148)

[Tex Riddell via cfe-commits]

================
@@ -35,6 +35,9 @@ def int_dx_typedBufferLoad_checkbit
 def int_dx_typedBufferStore
     : DefaultAttrsIntrinsic<[], [llvm_any_ty, llvm_i32_ty, llvm_anyvector_ty]>;
 
+def int_dx_bufferUpdateCounter
+    : DefaultAttrsIntrinsic<[llvm_i32_ty], [llvm_any_ty, llvm_i32_ty], [IntrWriteMem]>;
----------------
tex3d wrote:

No attribute would indicate may read/write memory.  However, what about `IntrInaccessibleMemOrArgMemOnly`?  I wonder if that attribute would more accurately capture what we want.  This counter memory is unique and cannot alias any other memory operations in the module.

https://github.com/llvm/llvm-project/pull/114148