[clang] Add clang atomic control options and attribute (PR #114841)

[Erich Keane via cfe-commits]

================
@@ -625,6 +625,43 @@ static Attr *handleHLSLControlFlowHint(Sema &S, Stmt *St, const ParsedAttr &A,
   return ::new (S.Context) HLSLControlFlowHintAttr(S.Context, A);
 }
 
+static Attr *handleAtomicAttr(Sema &S, Stmt *St, const ParsedAttr &A,
+                              SourceRange Range) {
+  if (!isa<CompoundStmt>(St)) {
----------------
erichkeane wrote:

I mean the `CompoundStmt` check.  The `Subject` in the `Attr.td` should have already prevent anything wiht a `CompoundStmt` Statement from getting here.

https://github.com/llvm/llvm-project/pull/114841