Proposal to add EIP-2315 (Simple Subroutines) and EIP-4200 (Static Relative Jumps) into Shanghai.

[gcolvin]

This is an early indication to seek inclusion of EIP-2315 (Simple Subroutines) and EIP-4200 (Safer Control Flow) into Shanghai.

[gcolvin]

EIP-2315 remains substantially the same since 2017 -- one opcode to jump to a subroutine and one to return. Thanks to the Ethereum Object Format it now takes its arguments as static immediate data. It deprecates JUMP and JUMPI and together with Code Validation and Static Relative Jumps it ensures, at initialization time, that valid code will not execute invalid instructions or jump to invalid locations, will not underflow stack, will maintain consistent numbers of inputs and outputs for subroutines, and will have bounded stack height in the absence of recursion.

[timbeiko]

Closing this issue as the EOF is now a candidate replacement.