[llvm] Port gisel cse analysis to npm (PR #179815)

[Aiden Grossman via llvm-commits]

https://github.com/boomanaiden154 approved this pull request.

LGTM.

PR title needs to be updated to something more proper like "[GISel][X86] Port CSE analysis to NPM".

https://github.com/llvm/llvm-project/pull/179815