[llvm] [DAG] Teach SelectionDAGBuilder to read parameter alignment of compressstore/expandload. (PR #83763)

[Yeting Kuo via llvm-commits]

yetingk wrote:

> what happened to the LangRef change?

Sorry, do you mean why I changed LangRef? I changed it because @efriedma-quic asked for. And I opened another PR for this just I think changing ir document is a little exceed the scope of this patch.  

> It's probably worth documenting the behavior in LangRef, like we do for other intrinsics that support "align" markings.



https://github.com/llvm/llvm-project/pull/83763