Z:gnu-www-ja-stallman-kth--eb91b1-Sometimes depending on whether/en

Sometimes depending on whether the result of the first instruction had any further use, it might be necessary to make a combined instruction with two assignment operators. One for this value [pointing at ???]and another one with this value [pointing at ???] substituted in it with what came from the second instruction. But if this value was only used that once, you could eliminate it after substituting for it; there'd be no need to compute it any more. So it's actually somewhat complicated doing the substitution correctly checking that the intervening instructions don't change any of these values and other such things. When you support such things as auto-increment and auto-decrement addressing, which I do now, you also have to do various checks for those to check for situations where what you're doing is not value preserving.