EIP-8024: Backward compatible SWAPN, DUPN, EXCHANGE

[frangio]

Discussion topic for EIP-8024.

This is a fork of EIP-663 without a dependency on EOF.

Update Log

• 2025-09-06: initial proposal to update EIP-663
• 2025-09-15: decision to fork as new EIP
• 2025-11-04: updated encode_pair, decode_pair to fix inconsistency between spec and examples

[frangio]

Discussion of alternatives:

EVM Immediates

All current EVM instructions other than the push opcodes take all of their operands from the stack. Many instructions have been proposed in the past that would’ve liked to use immediate operands, where the operand value is a constant hardcoded in the bytecode instead. No such instruction has been accepted yet because it would imply a breaking change to existing EVM bytecode. EOFv1 (EIP-7692) would have addressed this, but the proposal was ultimately rejected. This post looks at the problem ane…