Constant term pre-evaluation

[nielstron]

This proposes a single optimization, that improves two things at once:

• constant complex expressions that work in python are pre-evaluated and will work in OpShin too (i.e. bytes.fromhex("0011") and list(range(0,10,3)))
• runtime is improved because at a high level constant values are precomputed (i.e. 2**24 is not computed on-chain but at compile time)

One final thing that needs to be addressed here is that we need to keep track of user-defined scopes (potentially re-assigned variables)

[nielstron]

@juliusfrost Do you think you can get some numbers on how this affects compile time? And maybe places (i.e. in the pioneer program) that benefit from this? Most likely stuff like hardcoded keys that can now be written as "bytes.fromhex"

[nielstron]

I just checked the examples and they have converged to a state where there is almost nothing that could be constant folded (except for some PlutusData constants). Might be a results of this feature missing so far though.

[juliusfrost]

@juliusfrost Do you think you can get some numbers on how this affects compile time? And maybe places (i.e. in the pioneer program) that benefit from this? Most likely stuff like hardcoded keys that can now be written as "bytes.fromhex"

Maybe stuff in the interval api? Would methods like make_from be folded?

[nielstron]

As of the current state, thats not the case. I guess constant folding is a bit misleading as we are just preevaluating static expressions. What would be interesting is to propagate/fold properly, but this requires more sophisticated analysis 😅

[nielstron]

Since this only adds 0.1s to the testbench, I will merge this feature. Notably, proper constant folding is still a desired feature and may follow later (potentially even based on this implementation).

Hopefully users won't get too confused about the fact that certain statements work as long as they are constant (i.e. bytes.fromhex("00") but not when they are dynamic (i.e. bytes.fromhex(a)). The fact that smart contract authors now don't have to worry about the cost of evaluating constant statements should greatly improve readability though.