incorrect order of evaluation of side effects for some builtins

Impact

The order of evaluation of the arguments of the builtin functions uint256_addmod, uint256_mulmod, ecadd and ecmul does not follow source order. • For uint256_addmod(a,b,c) and uint256_mulmod(a,b,c), the order is c,a,b. • For ecadd(a,b) and ecmul(a,b), the order is b,a.

Note that this behaviour is problematic when the evaluation of one of the arguments produces side effects that other arguments depend on.

Patches

https://github.com/vyperlang/vyper/pull/3583

Workarounds

When using builtins from the list above, make sure that the arguments of the expression do not produce side effects or, if one does, that no other argument is dependent on those side effects.