[llvm] [LangRef] asm clobber constrains: '~memory' allows reads and synchronization (PR #150191)

[Eli Friedman via llvm-commits]

https://github.com/efriedma-quic approved this pull request.

I'm fine with tightening the definition this way, as long as we think existing transforms aren't impacted.

]If there are impacted transforms, we'd probably need to dig a bit more; we might do it anyway, but I'd want to think about it.  But I don't think there are?  I'd appreciate it if you could confirm that it gets mapped to something sufficiently conservative in the SelectionDAG code...

https://github.com/llvm/llvm-project/pull/150191