Looking for the name of an optimization

I've seen this optimization mentioned a few places, but nobody seems to
agree on the name.

So, I thought I'd ask and see if someone else seen a definitive name for
it.

    if (x == 1 && y == 2)
        z = 300 / (x + y)

==>

    if (x == 1 && y == 2)
        z = 100


Can anyone help me name that optimization?

Thanks,
Chris