[clang] nonblocking/nonallocating attributes (was: nolock/noalloc) (PR #84983)

[Andrew Pinski via cfe-commits]

pinskia wrote:

Well assume attribute is a good example of where gcc and clang disagree and might cause issues. Gcc implemented the assume attribute just the same as the standard one. While clang implemented before standardization and now they differ and could cause issues. This is why I requested using clang_ here.

https://github.com/llvm/llvm-project/pull/84983