[llvm] [ValueTracking] Conservative nosync check prevents vectorization (PR #190249)

[Nikita Popov via llvm-commits]

nikic wrote:

I'm unable to leave review comments on this PR, it may be necessary to file a new one.

Note that you can now use I.maySynchronize() instead of isOrderedAtomic. I also think we should keep the old willNotFreeBetween name, as sync is just another way to free. (We're changing the definition of nofree to also forbid free via synchronization, so these are no longer really separate properties anymore.)

https://github.com/llvm/llvm-project/pull/190249