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

[Erich Keane via cfe-commits]

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@@ -1107,6 +1113,66 @@ inline void FPOptions::applyChanges(FPOptionsOverride FPO) {
   *this = FPO.applyOverrides(*this);
 }
 
+// The three atomic code-generation options.
+// The canonical (positive) names are:
+//   "remote_memory", "fine_grained_memory", and "ignore_denormal_mode".
+// In attribute or command-line parsing, a token prefixed with "no_" inverts its
+// value.
+enum class AtomicOptionKind {
+  RemoteMemory,       // true means remote memory is enabled.
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erichkeane wrote:

nit: just remove 'true means' from these three comments, it is implied.  Perhaps reform to:

`enable remote memory.`
`enable fine-grained memory.`
`ignore floating-point denormals.`

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