[llvm] [IR] Initial introduction of memset_pattern (PR #97583)

[Yingwei Zheng via llvm-commits]

================
@@ -1263,6 +1263,41 @@ class MemSetInlineInst : public MemSetInst {
   }
 };
 
+/// This is the base class for llm.experimental.memset.pattern
----------------
dtcxzyw wrote:

```suggestion
/// This is the base class for llvm.experimental.memset.pattern
```

https://github.com/llvm/llvm-project/pull/97583