[llvm] [IR] Initial introduction of memset_pattern (PR #97583)

[Alex Bradbury via llvm-commits]

asb wrote:

I believe all review comments are now addressed. Thank you.

@bjope yes I agree it could be useful for that case. I don't think there's anything in the current description that would prevent moving in the direction you suggest in the future.

https://github.com/llvm/llvm-project/pull/97583