2021-01-21 15:20:22 +00:00
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from opcodes import BYTE, SHR, DIV
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2020-06-04 09:11:53 +00:00
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from rule import Rule
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2021-01-21 15:20:22 +00:00
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from z3 import BitVec, ULT
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2020-06-04 09:11:53 +00:00
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"""
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byte(A, shr(B, X))
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2020-08-04 09:25:09 +00:00
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given A < B / 8
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2020-06-04 09:11:53 +00:00
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->
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0
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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 = 0
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rule.require(ULT(A, DIV(B,8)))
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rule.check(nonopt, opt)
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