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vm: optimize EXP

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Optimize EXP performance by using simple algorithm that replaces division with
a bit mask.
This commit is contained in:
Paweł Bylica 2016-10-19 17:16:06 +02:00
parent 8048f4d4f6
commit 2ae2a78f38
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GPG key ID: 7A0C037434FE77EF
1 changed files with 10 additions and 2 deletions
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12
core/vm/instructions.go
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@ -192,8 +192,16 @@ func opSmod(instr instruction, pc *uint64, env Environment, contract *Contract,
}
func opExp(instr instruction, pc *uint64, env Environment, contract *Contract, memory *Memory, stack *Stack) {
x, y := stack.pop(), stack.pop()
stack.push(U256(x.Exp(x, y, Pow256)))
base, exponent := stack.pop(), stack.pop()
result := big.NewInt(1)
for exponent.Cmp(common.Big0) != 0 {
if exponent.Bit(0) == 1 {
U256(result.Mul(result, base))
}
U256(base.Mul(base, base))
exponent.Rsh(exponent, 1)
}
stack.push(result)
}
func opSignExtend(instr instruction, pc *uint64, env Environment, contract *Contract, memory *Memory, stack *Stack) {