We have the following problem: when function call argument expressions mutate some of the variables that are being passed as arguments, the left-to-right semantics isn't obeyed. The problem is that the funcction call simply refers to the registers that hold the variables, rather than to the evaluated values. For instance (fun a (inc a)) will translate to something like (gcall <n> (v 3) (v 3)) which is incorrect: both argument positions refer to the current value of a, whereas we need the left argument to refer to the value before the increment. * stdlib/compiler.tl (compiler comp-var): Do not assert the variable as the output register, with null code. Indicate that the value is in the caller's output register, and if necessary generate the move. (compiler comp-setq): When compiling the right-hand-side, use the original output register, so that we don't end up reporting the variable as the result location.