I think the best solution is either `iq == ip` must be rewritten to false, or in the body of the branch the p and q regions are concatenated and then the alias

I think the best solution is either `iq == ip` must be rewritten to false, or in the body of the branch the p and q regions are concatenated and then the alias analysis doesn't work. In general I like an approach of starting with the optomizations we want to do, and other sources non-determinism such as arbitrary layout we want to support, and then working backwards to fine the preconditions are program must abide by in order to for the compilation to not go wrong.