function f(cond)
     for ...
         If cond
              cond & true # Could maybe be moved, but tricky since we need to reconstruct the branch.
         else if I > 5
             cond & true # Can't be moved
      end
end

It may be easier to do if cond as a separate loop-unswitch pass. And for now just punt on this in the context of LICM.

Memory operations are only eligible to be hoisted if they are proven to not alias any memory written to within the loops.

This may also require per argument memory effects.

cc: @aviatesk

The biggest known-unkown is how to work with multiple loops in one function.

extract_loopinfo finds all loops at all levels, but for LICM we also need the nesting order so that we can work on the innermost loop first.

Secondly we need to maintain the correctness of LoopInfo itself under CFG manipulations.

So maybe we need to separate LoopInfo and Loop as two separate structs, the former representing the loop nests within the function.