So basically your changes to `e->E2` are being ignored if `e->E2` is a CSE?  I'm guessing it's too late to be changing the elems directly, you should probably just tell it to do a constant load instead of going through `scodelem` when you've picked a new value.  Alternatively, add new `OPmemcmp16/32/64` ops and pick a multi-byte one from the optimizer.