[clang] [Clang] Accept vector types in the atomic builtins (PR #214653)

[Erich Keane via cfe-commits]

erichkeane wrote:

The bug has been updated to show that this is something that would require an RFC, and thus is something we cannot accept.  Closing until an RFC is proposed/accepted.

https://github.com/llvm/llvm-project/pull/214653