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

[Erich Keane via cfe-commits]

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@@ -764,6 +764,73 @@ void Parser::ParseGNUAttributeArgs(
                            ScopeLoc, Form);
 }
 
+void Parser::ParseAtomicAttribute(
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erichkeane wrote:

I'm very much beginning to dislike the syntax for this, if it needs this much special handling.  We shoudl find a way to spell this attribute in a way that WORKS with our existing attribute formats.  Else this becomes REALLY difficult for other compilers to ignore.

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