mirror of
https://github.com/ethereum/solidity
synced 2023-10-03 13:03:40 +00:00
32 lines
559 B
Python
32 lines
559 B
Python
from opcodes import BYTE, DIV, SHR
|
|
from rule import Rule
|
|
from z3 import BitVec, UGE, ULE, ULT
|
|
|
|
"""
|
|
byte(A, shr(B, X))
|
|
given B % 8 == 0 && A < n_bits/8 && B <= n_bits && A >= B / 8
|
|
->
|
|
byte(A - B / 8, X)
|
|
"""
|
|
|
|
rule = Rule()
|
|
|
|
n_bits = 256
|
|
|
|
# Input vars
|
|
X = BitVec('X', n_bits)
|
|
A = BitVec('A', n_bits)
|
|
B = BitVec('B', n_bits)
|
|
|
|
# Non optimized result
|
|
nonopt = BYTE(A, SHR(B, X))
|
|
# Optimized result
|
|
opt = BYTE(A - B / 8, X)
|
|
|
|
rule.require(B % 8 == 0)
|
|
rule.require(ULT(A, n_bits/8))
|
|
rule.require(ULE(B, n_bits))
|
|
rule.require(UGE(A, DIV(B,8)))
|
|
|
|
rule.check(nonopt, opt)
|