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comparison tables for EVM opcodes to ewasm methods and wasm instructions
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‎evm_vs_ewasm_opcode_table.md

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## EVM opcodes vs ewasm methods
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These tables compares EVM opcodes with ewasm methods and wasm instructions. The EVM defines 134 opcodes (as of the Byzantium hard fork). Of these 134 opcodes, some are generic machine instructions (ADD, MUL, ISZERO, XOR, etc.) and the rest are Ethereum-specific opcodes (SLOAD, SSTORE, CALLVALUE, BLOCKHASH, etc.).
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When EVM bytecode is translated into ewasm bytecode, the Ethereum-specific opcodes translate to ewasm interface methods (Ethereum Environment Interface (EEI) methods). These interface methods are provided as "host functions" to the wasm VM. All other EVM opcodes are not Ethereum-specific and do not access data from the Ethereum environment, so they can be translated to plain wasm instructions.
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To reference EVM opcodes, try the [yellow paper](https://ethereum.github.io/yellowpaper/paper.pdf), the [readable yellow paper](https://github.com/chronaeon/beigepaper/blob/master/beigepaper.pdf), or the [pyethereum implementation](https://github.com/ethereum/pyethereum/blob/develop/ethereum/opcodes.py).
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To reference ewasm interface methods, see the [EEI spec](https://github.com/ewasm/design/blob/master/eth_interface.md).
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### EVM opcodes that translate to ewasm methods (Ethereum Environment Interface (EEI) methods)
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EVM opcode | ewasm interface method
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----------------------|-----------------------------
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0x30: ADDRESS | getAddress
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0x31: BALANCE | getBalance
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0x32: ORIGIN | getTxOrigin
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0x33: CALLER | getCaller
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0x34: CALLVALUE | getCallValue
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0x35: CALLDATALOAD | callDataCopy(resultOffset, dataOffset, 32)
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0x36: CALLDATASIZE | getCallDataSize
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0x37: CALLDATACOPY | callDataCopy(resultOffset, dataOffset, size)
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0x38: CODESIZE | getCodeSize
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0x39: CODECOPY | codeCopy
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0x3a: GASPRICE | getTxGasPrice
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0x3b: EXTCODESIZE | getExternalCodeSize
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0x3c: EXTCODECOPY | externalCodeCopy
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0x3d: RETURNDATASIZ | getReturnDataSize
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0x3e: RETURNDATACOP | returnDataCopy
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0x40: BLOCKHASH | getBlockHash
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0x41: COINBASE | getBlockCoinbase
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0x42: TIMESTAMP | getBlockTimestamp
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0x43: NUMBER | getBlockNumber
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0x44: DIFFICULTY | getBlockDifficulty
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0x45: GASLIMIT | getBlockGasLimit
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0x54: SLOAD | storageLoad
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0x55: SSTORE | storageStore
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0x58: PC | -
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0x5a: GAS | getGasLeft
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0xa0: LOG0 | log(0,..)
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... |
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0xa4: LOG4 | log(4,..)
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0xf0: CREATE | create
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0xf1: CALL | call
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0xf2: CALLCODE | callCode
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0xf3: RETURN | return
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0xf4: DELEGATECALL | callDelegate
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0xfa: STATICCALL | callStatic
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0xfd: REVERT | revert
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0xff: SELFDESTRUCT | selfDestruct
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## EVM opcodes vs WebAssembly instructions
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Whereas EVM is an untyped VM with a 256-bit word size, WebAssembly is a typed VM with 32-bit and 64-bit word sizes. The two wasm base types are integers and floats, which when combined with the two word sizes, create four types: i32, i64, f32, f64.
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Ethereum WebAssembly, or ewasm, is a subset of wasm. Only the integer types (i32 and i64) are supported, floating point types and floating point instructions are not supported. In total, 60 wasm instructions are supported in ewasm:
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* 10 control flow instructions
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* 11 basic instructions
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* 19 integer arithmetic instructions
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* 10 integer comparison instructions
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* 3 integer conversion instructions
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* 7 memory instructions (load, store, extend)
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ewasm excludes the wasm floating point instructions:
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* 14 floating point instructions
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* 6 floating point comparison instructions
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* 7 floating point conversion instructions
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To reference wasm instructions, see the [wasm spec](https://github.com/WebAssembly/design/blob/master/Semantics.md) or [reference manual](https://github.com/sunfishcode/wasm-reference-manual/blob/master/WebAssembly.md#instructions).
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### EVM opcodes that translate to wasm instructions
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EVM opcode | wasm instruction (i32/i64)
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----------------------|----------------------
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0x00: STOP | end
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0x01: ADD | i32.add
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0x02: MUL | i32.mul
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0x03: SUB | i32.sub
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0x04: DIV | i32.div_u
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0x05: SDIV | i32.div_s
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0x06: MOD | i32.rem_u
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0x07: SMOD | i32.rem_s
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0x08: ADDMOD | -
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0x09: MULMOD | -
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0x0a: EXP | -
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0x0b: SIGNEXTEND | -
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0x10: LT | i32.lt_u
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0x11: GT | i32.gt_u
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0x12: SLT | i32.lt_s
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0x13: SGT | i32.gt_s
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0x14: EQ | i32.eq
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0x15: ISZERO | i32.eqz
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0x16: AND | i32.and
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0x17: OR | i32.or
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0x18: XOR | i32.xor
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0x19: NOT | -
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0x1a: BYTE | - [i32.load8]
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0x20: SHA3 | -
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0x50: POP | drop
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0x51: MLOAD | i32.load
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0x52: MSTORE | i32.store
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0x53: MSTORE8 | i32.store
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0x56: JUMP | br
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0x57: JUMPI | br_if, br_table
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0x59: MSIZE | current_memory
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0x5b: JUMPDEST | block, loop
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0xfe: INVALID | unreachable
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0x60: PUSH1 | i32.const
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... |
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0x7f: PUSH32 | i32.const
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0x80: DUP1 | get_global, get_local
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... |
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0x8f: DUP16 | get_global, get_local
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0x90: SWAP1 | -
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... |
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0x9f: SWAP16 | -

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