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Implement SAR opcode #1134

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merged 1 commit into from
Aug 7, 2018
Merged

Implement SAR opcode #1134

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1 change: 1 addition & 0 deletions eth/constants.py
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,7 @@
UINT_256_CEILING = 2**256
UINT_255_MAX = 2**255 - 1
UINT_255_CEILING = 2**255
UINT_255_NEGATIVE_ONE = -1 + UINT_256_CEILING
NULL_BYTE = b'\x00'
EMPTY_WORD = NULL_BYTE * 32

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5 changes: 5 additions & 0 deletions eth/vm/forks/constantinople/opcodes.py
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Expand Up @@ -32,6 +32,11 @@
mnemonic=mnemonics.SHR,
gas_cost=constants.GAS_VERYLOW,
),
opcode_values.SAR: as_opcode(
logic_fn=arithmetic.sar,
mnemonic=mnemonics.SAR,
gas_cost=constants.GAS_VERYLOW,
),
}

CONSTANTINOPLE_OPCODES = merge(
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15 changes: 15 additions & 0 deletions eth/vm/logic/arithmetic.py
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Expand Up @@ -205,3 +205,18 @@ def shr(computation):
result = (value >> shift_length) & constants.UINT_256_MAX

computation.stack_push(result)


def sar(computation):
"""
Arithmetic bitwise right shift
"""
shift_length, value = computation.stack_pop(num_items=2, type_hint=constants.UINT256)
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Side note, I just realized that we use keyword style calling for all stack operations, and a while back @davesque uncovered that calling things with positional arguments is significantly faster than keyword style calling. We should look into updating all of these call sites to use positional arguments.

value = unsigned_to_signed(value)

if shift_length >= 256:
result = 0 if value >= 0 else constants.UINT_255_NEGATIVE_ONE
else:
result = (value >> shift_length) & constants.UINT_256_MAX

computation.stack_push(result)
1 change: 1 addition & 0 deletions eth/vm/mnemonics.py
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Expand Up @@ -15,6 +15,7 @@
SIGNEXTEND = 'SIGNEXTEND'
SHL = 'SHL'
SHR = 'SHR'
SAR = 'SAR'
#
# Comparisons
#
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1 change: 1 addition & 0 deletions eth/vm/opcode_values.py
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Expand Up @@ -31,6 +31,7 @@
BYTE = 0x1a
SHL = 0x1b
SHR = 0x1c
SAR = 0x1d


#
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113 changes: 113 additions & 0 deletions tests/core/opcodes/test_opcodes.py
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Expand Up @@ -265,3 +265,116 @@ def test_shr(vm_class, val1, val2, expected):

result = computation.stack_pop(type_hint=constants.UINT256)
assert encode_hex(pad32(int_to_big_endian(result))) == expected


@pytest.mark.parametrize(
# EIP: https://github.com/ethereum/EIPs/blob/master/EIPS/eip-145.md#sar-arithmetic-shift-right
'vm_class, val1, val2, expected',
(
(
ConstantinopleVM,
'0x0000000000000000000000000000000000000000000000000000000000000001',
'0x00',
'0x0000000000000000000000000000000000000000000000000000000000000001',
),
(
ConstantinopleVM,
'0x0000000000000000000000000000000000000000000000000000000000000001',
'0x01',
'0x0000000000000000000000000000000000000000000000000000000000000000',
),
(
ConstantinopleVM,
'0x8000000000000000000000000000000000000000000000000000000000000000',
'0x01',
'0xc000000000000000000000000000000000000000000000000000000000000000',
),
(
ConstantinopleVM,
'0x8000000000000000000000000000000000000000000000000000000000000000',
'0xff',
'0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff',
),
(
ConstantinopleVM,
'0x8000000000000000000000000000000000000000000000000000000000000000',
'0x0100',
'0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff',
),
(
ConstantinopleVM,
'0x8000000000000000000000000000000000000000000000000000000000000000',
'0x0101',
'0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff',
),
(
ConstantinopleVM,
'0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff',
'0x00',
'0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff',
),
(
ConstantinopleVM,
'0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff',
'0x01',
'0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff',
),
(
ConstantinopleVM,
'0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff',
'0xff',
'0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff',
),
(
ConstantinopleVM,
'0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff',
'0x0100',
'0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff',
),
(
ConstantinopleVM,
'0x0000000000000000000000000000000000000000000000000000000000000000',
'0x01',
'0x0000000000000000000000000000000000000000000000000000000000000000',
),

(
ConstantinopleVM,
'0x4000000000000000000000000000000000000000000000000000000000000000',
'0xfe',
'0x0000000000000000000000000000000000000000000000000000000000000001',
),
(
ConstantinopleVM,
'0x7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff',
'0xf8',
'0x000000000000000000000000000000000000000000000000000000000000007f',
),
(
ConstantinopleVM,
'0x7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff',
'0xfe',
'0x0000000000000000000000000000000000000000000000000000000000000001',
),
(
ConstantinopleVM,
'0x7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff',
'0xff',
'0x0000000000000000000000000000000000000000000000000000000000000000',
),
(
ConstantinopleVM,
'0x7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff',
'0x0100',
'0x0000000000000000000000000000000000000000000000000000000000000000',
),
)
)
def test_sar(vm_class, val1, val2, expected):
computation = prepare_computation(vm_class)
computation.stack_push(decode_hex(val1))
computation.stack_push(decode_hex(val2))
computation.opcodes[opcode_values.SAR](computation)

result = computation.stack_pop(type_hint=constants.UINT256)
assert encode_hex(pad32(int_to_big_endian(result))) == expected