[llvm] [llvm][LICM] Add flag to control re-association (PR #149829)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

So generally, what this transform is doing for the multi-use case is somewhat iffy. It goes against our usual policy to not increase instruction count.

This already came up in the discussion on the original PR in https://github.com/llvm/llvm-project/pull/81608 and https://github.com/llvm/llvm-project/pull/102114 later restricted it to at most two uses.

Ideally we'd find a way here to provide good behavior for everyone without toolchains having to specify non-default options. For example, I'm wondering whether it makes sense to limit the multi-use case to FP ops only, but not integers ops?

https://github.com/llvm/llvm-project/pull/149829