[llvm] [AArch64] ConditionOptimizer: replace intra-block scan with map-based algorithm (PR #190455)

[Nashe Mncube via llvm-commits]

https://github.com/nasherm approved this pull request.

Thanks, LGTM. I just have one comment

Also I have a question on the use of `DenseMap`. As far as I understand this data structure may not be ideal for relatively small maps i.e. significantly less than 64 keys. It probably doesn't have too much of a bearing on performance for this pass as I do think a map search is a smarter way of spotting pairs. However, have you considered other data structures? 

https://github.com/llvm/llvm-project/pull/190455