[llvm] [InstCombine] Don't mix X << Y / Z << Y with X << Y / X << Z (PR #69302)

[via llvm-commits]

XChy wrote:

I think it may be also necessary to add an `IsExact`  argument for this function? To remind other developers to care about exact flag.

https://github.com/llvm/llvm-project/pull/69302