Performance: no lazy_static or const fn about sputnikvm HOT 4 OPEN

Moved to https://github.com/ethereumproject/sputnikvm/wiki/Performance-Improvements due to #175.

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lazy_static deps is now used in the core sputnikvm crate.

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@sorpaas So all these precompiled gas functions need to be utilized with lazy_static right?

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Actually originally this was related to all const variables here (https://github.com/ethereumproject/sputnikvm/blob/master/src/eval/cost.rs#L9). Because Gas needs to be constructed on the fly and it's not free, it might be a performance issue. (See all the Into::into() below.)

Still, however, I just realized that Gas implements Copy trait, so even if when it is lazy-static-ed it might still not help a lot. A constraint on the Ethereum blockchain is that Gas, although its theoretical max value is U256::max_value(), it in practice cannot exceed usize::max_value(). A better way to handle this is probably to make Gas a type parameter in all VM structs. After that, track the initial provided gas, if that value exceeds usize::max_value(), use usize as the type parameter, otherwise, fallback to the full U256 (the conditional check does not need to be in the sputnikvm library).

The type parameter of gas G usually only needs Add + Mul + Sub + From<usize>. In the calculation of memory cost, however, there needs to be a checked multiply which does not belong to a trait, so a custom trait might need to be created for that.

Oops sorry I probably should be more careful when labeling an issue as "good first issue".

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