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core/vm: add shortcuts for trivial exp cases (#16851)

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Martin Holst Swende 2018-10-16 00:51:39 +02:00 committed by Felix Lange
parent 6a7695e367
commit a352de6a08
1 changed files with 16 additions and 4 deletions
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20
core/vm/instructions.go
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@ -124,10 +124,22 @@ func opSmod(pc *uint64, interpreter *EVMInterpreter, contract *Contract, memory
func opExp(pc *uint64, interpreter *EVMInterpreter, contract *Contract, memory *Memory, stack *Stack) ([]byte, error) {
base, exponent := stack.pop(), stack.pop()
stack.push(math.Exp(base, exponent))
interpreter.intPool.put(base, exponent)
// some shortcuts
cmpToOne := exponent.Cmp(big1)
if cmpToOne < 0 { // Exponent is zero
// x ^ 0 == 1
stack.push(base.SetUint64(1))
} else if base.Sign() == 0 {
// 0 ^ y, if y != 0, == 0
stack.push(base.SetUint64(0))
} else if cmpToOne == 0 { // Exponent is one
// x ^ 1 == x
stack.push(base)
} else {
stack.push(math.Exp(base, exponent))
interpreter.intPool.put(base)
}
interpreter.intPool.put(exponent)
return nil, nil
}