ethereum.forks.bpo5.vm.instructions.arithmeticethereum.forks.amsterdam.vm.instructions.arithmetic
Ethereum Virtual Machine (EVM) Arithmetic Instructions.
.. contents:: Table of Contents :backlinks: none :local:
Introduction
Implementations of the EVM Arithmetic instructions.
add ¶
Adds the top two elements of the stack together, and pushes the result back on the stack.
Parameters
evm : The current EVM frame.
sub ¶
Subtracts the top two elements of the stack, and pushes the result back on the stack.
Parameters
evm : The current EVM frame.
mul ¶
Multiplies the top two elements of the stack, and pushes the result back on the stack.
Parameters
evm : The current EVM frame.
div ¶
Integer division of the top two elements of the stack. Pushes the result back on the stack.
Parameters
evm : The current EVM frame.
def div(evm: Evm) -> None:
| 107 | <snip> |
|---|---|
| 117 | # STACK |
| 118 | dividend = pop(evm.stack) |
| 119 | divisor = pop(evm.stack) |
| 120 | |
| 121 | # GAS |
| 122 | charge_gas(evm, GasCosts.OPCODE_DIV) |
| 123 | |
| 124 | # OPERATION |
| 125 | if divisor == 0: |
| 126 | quotient = U256(0) |
| 127 | else: |
| 128 | quotient = dividend // divisor |
| 129 | |
| 130 | push(evm.stack, quotient) |
| 131 | |
| 132 | # PROGRAM COUNTER |
| 133 | evm.pc += Uint(1) |
U255_CEIL_VALUE¶
| 136 | U255_CEIL_VALUE = 2**255 |
|---|
sdiv ¶
Signed integer division of the top two elements of the stack. Pushes the result back on the stack.
Parameters
evm : The current EVM frame.
def sdiv(evm: Evm) -> None:
| 140 | <snip> |
|---|---|
| 150 | # STACK |
| 151 | dividend = pop(evm.stack).to_signed() |
| 152 | divisor = pop(evm.stack).to_signed() |
| 153 | |
| 154 | # GAS |
| 155 | charge_gas(evm, GasCosts.OPCODE_SDIV) |
| 156 | |
| 157 | # OPERATION |
| 158 | if divisor == 0: |
| 159 | quotient = 0 |
| 160 | elif dividend == -U255_CEIL_VALUE and divisor == -1: |
| 161 | quotient = -U255_CEIL_VALUE |
| 162 | else: |
| 163 | sign = get_sign(dividend * divisor) |
| 164 | quotient = sign * (abs(dividend) // abs(divisor)) |
| 165 | |
| 166 | push(evm.stack, U256.from_signed(quotient)) |
| 167 | |
| 168 | # PROGRAM COUNTER |
| 169 | evm.pc += Uint(1) |
mod ¶
Modulo remainder of the top two elements of the stack. Pushes the result back on the stack.
Parameters
evm : The current EVM frame.
def mod(evm: Evm) -> None:
| 173 | <snip> |
|---|---|
| 183 | # STACK |
| 184 | x = pop(evm.stack) |
| 185 | y = pop(evm.stack) |
| 186 | |
| 187 | # GAS |
| 188 | charge_gas(evm, GasCosts.OPCODE_MOD) |
| 189 | |
| 190 | # OPERATION |
| 191 | if y == 0: |
| 192 | remainder = U256(0) |
| 193 | else: |
| 194 | remainder = x % y |
| 195 | |
| 196 | push(evm.stack, remainder) |
| 197 | |
| 198 | # PROGRAM COUNTER |
| 199 | evm.pc += Uint(1) |
smod ¶
Signed modulo remainder of the top two elements of the stack. Pushes the result back on the stack.
Parameters
evm : The current EVM frame.
def smod(evm: Evm) -> None:
| 203 | <snip> |
|---|---|
| 213 | # STACK |
| 214 | x = pop(evm.stack).to_signed() |
| 215 | y = pop(evm.stack).to_signed() |
| 216 | |
| 217 | # GAS |
| 218 | charge_gas(evm, GasCosts.OPCODE_SMOD) |
| 219 | |
| 220 | # OPERATION |
| 221 | if y == 0: |
| 222 | remainder = 0 |
| 223 | else: |
| 224 | remainder = get_sign(x) * (abs(x) % abs(y)) |
| 225 | |
| 226 | push(evm.stack, U256.from_signed(remainder)) |
| 227 | |
| 228 | # PROGRAM COUNTER |
| 229 | evm.pc += Uint(1) |
addmod ¶
Modulo addition of the top 2 elements with the 3rd element. Pushes the result back on the stack.
Parameters
evm : The current EVM frame.
def addmod(evm: Evm) -> None:
| 233 | <snip> |
|---|---|
| 243 | # STACK |
| 244 | x = Uint(pop(evm.stack)) |
| 245 | y = Uint(pop(evm.stack)) |
| 246 | z = Uint(pop(evm.stack)) |
| 247 | |
| 248 | # GAS |
| 249 | charge_gas(evm, GasCosts.OPCODE_ADDMOD) |
| 250 | |
| 251 | # OPERATION |
| 252 | if z == 0: |
| 253 | result = U256(0) |
| 254 | else: |
| 255 | result = U256((x + y) % z) |
| 256 | |
| 257 | push(evm.stack, result) |
| 258 | |
| 259 | # PROGRAM COUNTER |
| 260 | evm.pc += Uint(1) |
mulmod ¶
Modulo multiplication of the top 2 elements with the 3rd element. Pushes the result back on the stack.
Parameters
evm : The current EVM frame.
def mulmod(evm: Evm) -> None:
| 264 | <snip> |
|---|---|
| 274 | # STACK |
| 275 | x = Uint(pop(evm.stack)) |
| 276 | y = Uint(pop(evm.stack)) |
| 277 | z = Uint(pop(evm.stack)) |
| 278 | |
| 279 | # GAS |
| 280 | charge_gas(evm, GasCosts.OPCODE_MULMOD) |
| 281 | |
| 282 | # OPERATION |
| 283 | if z == 0: |
| 284 | result = U256(0) |
| 285 | else: |
| 286 | result = U256((x * y) % z) |
| 287 | |
| 288 | push(evm.stack, result) |
| 289 | |
| 290 | # PROGRAM COUNTER |
| 291 | evm.pc += Uint(1) |
exp ¶
Exponential operation of the top 2 elements. Pushes the result back on the stack.
Parameters
evm : The current EVM frame.
def exp(evm: Evm) -> None:
| 295 | <snip> |
|---|---|
| 305 | # STACK |
| 306 | base = Uint(pop(evm.stack)) |
| 307 | exponent = Uint(pop(evm.stack)) |
| 308 | |
| 309 | # GAS |
| 310 | # This is equivalent to 1 + floor(log(y, 256)). But in python the log |
| 311 | # function is inaccurate leading to wrong results. |
| 312 | exponent_bits = exponent.bit_length() |
| 313 | exponent_bytes = (exponent_bits + Uint(7)) // Uint(8) |
| 314 | charge_gas( |
| 315 | evm, |
| 315 | GasCosts.OPCODE_EXP_BASE |
| 316 | + GasCosts.OPCODE_EXP_PER_BYTE * exponent_bytes, |
| 316 | ExecutionGas( |
| 317 | GasCosts.OPCODE_EXP_BASE |
| 318 | + GasCosts.OPCODE_EXP_PER_BYTE * exponent_bytes |
| 319 | ), |
| 320 | ) |
| 321 | |
| 322 | # OPERATION |
| 323 | result = U256(pow(base, exponent, Uint(U256.MAX_VALUE) + Uint(1))) |
| 324 | |
| 325 | push(evm.stack, result) |
| 326 | |
| 327 | # PROGRAM COUNTER |
| 328 | evm.pc += Uint(1) |
signextend ¶
Sign extend operation. In other words, extend a signed number which fits in N bytes to 32 bytes.
Parameters
evm : The current EVM frame.
def signextend(evm: Evm) -> None:
| 332 | <snip> |
|---|---|
| 342 | # STACK |
| 343 | byte_num = pop(evm.stack) |
| 344 | value = pop(evm.stack) |
| 345 | |
| 346 | # GAS |
| 347 | charge_gas(evm, GasCosts.OPCODE_SIGNEXTEND) |
| 348 | |
| 349 | # OPERATION |
| 350 | if byte_num > U256(31): |
| 351 | # Can't extend any further |
| 352 | result = value |
| 353 | else: |
| 354 | # U256(0).to_be_bytes() gives b'' instead of b'\x00'. |
| 355 | value_bytes = Bytes(value.to_be_bytes32()) |
| 356 | # Now among the obtained value bytes, consider only |
| 357 | # N `least significant bytes`, where N is `byte_num + 1`. |
| 358 | value_bytes = value_bytes[31 - int(byte_num) :] |
| 359 | sign_bit = value_bytes[0] >> 7 |
| 360 | if sign_bit == 0: |
| 361 | result = U256.from_be_bytes(value_bytes) |
| 362 | else: |
| 363 | num_bytes_prepend = U256(32) - (byte_num + U256(1)) |
| 364 | result = U256.from_be_bytes( |
| 365 | bytearray([0xFF] * num_bytes_prepend) + value_bytes |
| 366 | ) |
| 367 | |
| 368 | push(evm.stack, result) |
| 369 | |
| 370 | # PROGRAM COUNTER |
| 371 | evm.pc += Uint(1) |