We currently do not seem to handle differential returns that are pointer types. e.g. a call %x = float* foo() where %x is not a constant value. A test case for this is attached --- if you look at the test case please spend a moment to verify that I set it up correctly as it was extracted from a larger file generated from eigen code. If the general fix isn't easy we should discuss exactly what we want to do here (e.g. create a wrapper function for such calls that put all of our differentiable calls into a common form where certain return values are additional arguments)

eigen-small-test.ll.txt