[clang] [llvm] New calling convention preserve_none (PR #76868)

[Erich Keane via cfe-commits]

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@@ -2868,6 +2868,11 @@ def M68kRTD: DeclOrTypeAttr {
   let Documentation = [M68kRTDDocs];
 }
 
+def PreserveNone : DeclOrTypeAttr {
+  let Spellings = [Clang<"preserve_none">];
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erichkeane wrote:

This should have a subjectlist set, since this is on functions, it should probably have a function subject.  Since it is target specific, it should ALSO be a target specific attribute.

https://github.com/llvm/llvm-project/pull/76868