EIP-8024: DUPN, SWAPN, EXCHANGE opcodes - #2874
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Add the three backward-compatible stack opcodes (EIP-8024): DUPN (0xe6), SWAPN (0xe7), EXCHANGE (0xe8), each with a 1-byte immediate and Gverylow (3) cost, gated on the new Ghaseip8024 flag (true at AMSTERDAM). Modeled as StackOps that read and decode their immediate from <program> at exec time (like PUSH): decode_single ((x+145)%256, valid x in [0,90]u[128,255]) for DUPN/SWAPN, decode_pair (k=x^143; divmod(k,16)) for EXCHANGE. DUPN(n)/SWAPN(n) reuse the DUP/SWAP stack logic; EXCHANGE swaps two arbitrary positions. Out-of-range immediates halt EVMC_INVALID_INSTRUCTION, insufficient depth halts EVMC_STACK_UNDERFLOW; #widthOp is 2 (pc advances past the immediate). Jumpdest analysis (#widthOpCode) is intentionally left unchanged: EIP-8024's immediates are constrained to never be a JUMPDEST or PUSH byte, so scanning the immediate as an ordinary opcode keeps old jumpdest analysis valid (the backward-compatibility property; confirmed by the jump_to_immediate_byte fixtures). Unmask all 53 eip8024 fixtures. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Implements EIP-8024: immediate-operand stack manipulation opcodes for legacy EVM.
evm.md:DUPN/SWAPN/EXCHANGEwith one-byte immediates;schedule.md:Ghaseip8024+ gas.Added helpers based on the EIP's reference functions:
#immByte(PGM, PC)reads the operand like PUSH does (#range, total, zero-padding at end-of-code),#decodeSingleis the EIP'sdecode_single((x+145) mod 256, mapping the valid bytes onto the contiguous depth range17..235),#decodePairA/#decodePairBare the two components ofdecode_pair(the pair is exposed as two projections; each dispatches to an arity-2 overload on the nibbles ofx^0x8F, with complementaryQ <Int R/Q >=Int Rrequires clauses).#validSingle/#validPairimplement the EIP's valid-immediate byte ranges; invalid immediates halt withEVMC_INVALID_INSTRUCTION, insufficient depth withEVMC_STACK_UNDERFLOW.Jumpdest analysis is intentionally unchanged: valid immediates can never be a
JUMPDESTorPUSHbyte, which is the EIP's backward-compatibility property.