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Joe Savona
dce5371763
Implements constant propagation/constant folding for a conservative subset of the language. The approach is described in detail in the comments in the file itself, a key note here is that this pass currently emits what looks like garbage: ``` // input const x = 1; const y = x + 1; // output const x = 1; 2; // <---- you'll see a bunch of lines like this const y = 2; ``` These useless lines occur where previously there was a temporary getting calculated that was used later (so we saved it until it was used), but now it isn't used later so we just emit it in-place. Dead code elimination (DCE) can eliminate these and other useless statements later. Note that a key motivation for implementing this pass is to reduce memoization blocks to what is strictly required for dynamic computations. Why memoize at runtime when we compute at build time?