[clang] [Clang] Add __builtin_bswapg (PR #162433)

[Oliver Hunt via cfe-commits]

ojhunt wrote:

@clingfei I've put a PR up that guards int128 on availability - I tested locally by modifying the test to force a non-int128 supporting target, but actually landing such a change exposes other issues in the test, but maybe a future change could fix it to be better than the current x86_64 specific behaviour. It's set to automerge once the bots are happy so will hopefully land overnight (PST)

https://github.com/llvm/llvm-project/pull/162433