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