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optimization: replace division/multiplication by 2^x with shifts #15151

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Merged
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May 19, 2025
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optimization: replace division/multiplication by 2^x with shifts #15151

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16 changes: 6 additions & 10 deletions core/vm/contracts.go
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Original file line number Diff line number Diff line change
Expand Up @@ -342,12 +342,8 @@ type bigModExp struct {

var (
big1 = big.NewInt(1)
big2 = big.NewInt(2)
big3 = big.NewInt(3)
big4 = big.NewInt(4)
big7 = big.NewInt(7)
big8 = big.NewInt(8)
big16 = big.NewInt(16)
big20 = big.NewInt(20)
big32 = big.NewInt(32)
big64 = big.NewInt(64)
Expand All @@ -374,13 +370,13 @@ func modExpMultComplexityEip198(x *big.Int) *big.Int {
case x.Cmp(big1024) <= 0:
// (x ** 2 // 4 ) + ( 96 * x - 3072)
x = new(big.Int).Add(
new(big.Int).Div(new(big.Int).Mul(x, x), big4),
new(big.Int).Rsh(new(big.Int).Mul(x, x), 2),
new(big.Int).Sub(new(big.Int).Mul(big96, x), big3072),
)
default:
// (x ** 2 // 16) + (480 * x - 199680)
x = new(big.Int).Add(
new(big.Int).Div(new(big.Int).Mul(x, x), big16),
new(big.Int).Rsh(new(big.Int).Mul(x, x), 4),
new(big.Int).Sub(new(big.Int).Mul(big480, x), big199680),
)
}
Expand All @@ -397,7 +393,7 @@ func modExpMultComplexityEip198(x *big.Int) *big.Int {
// where is x is max(length_of_MODULUS, length_of_BASE)
func modExpMultComplexityEip2565(x *big.Int) *big.Int {
x.Add(x, big7)
x.Div(x, big8)
x.Rsh(x, 3) // ÷8
return x.Mul(x, x)
}

Expand All @@ -418,7 +414,7 @@ func modExpMultComplexityEip7883(x *big.Int) *big.Int {
if lessOrEq32 {
return x
} else {
return x.Mul(x, big2)
return x.Lsh(x, 1) // ×2
}
}

Expand Down Expand Up @@ -454,9 +450,9 @@ func (c *bigModExp) RequiredGas(input []byte) uint64 {
if expLen.Cmp(big32) > 0 {
adjExpLen.Sub(expLen, big32)
if c.eip7883 {
adjExpLen.Mul(big16, adjExpLen)
adjExpLen.Lsh(adjExpLen, 4) // ×16
} else {
adjExpLen.Mul(big8, adjExpLen)
adjExpLen.Lsh(adjExpLen, 3) // ×8
}
}
adjExpLen.Add(adjExpLen, big.NewInt(int64(msb)))
Expand Down
16 changes: 8 additions & 8 deletions erigon-lib/types/transaction_signing.go
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Expand Up @@ -56,30 +56,30 @@ func MakeSigner(config *chain.Config, blockNumber uint64, blockTime uint64) *Sig
signer.blob = true
signer.setCode = true
signer.chainID.Set(&chainId)
signer.chainIDMul.Mul(&chainId, u256.Num2)
signer.chainIDMul.Lsh(&chainId, 1) // ×2
case config.IsCancun(blockTime):
// All transaction types are still supported
signer.protected = true
signer.accessList = true
signer.dynamicFee = true
signer.blob = true
signer.chainID.Set(&chainId)
signer.chainIDMul.Mul(&chainId, u256.Num2)
signer.chainIDMul.Lsh(&chainId, 1) // ×2
case config.IsLondon(blockNumber):
signer.protected = true
signer.accessList = true
signer.dynamicFee = true
signer.chainID.Set(&chainId)
signer.chainIDMul.Mul(&chainId, u256.Num2)
signer.chainIDMul.Lsh(&chainId, 1) // ×2
case config.IsBerlin(blockNumber):
signer.protected = true
signer.accessList = true
signer.chainID.Set(&chainId)
signer.chainIDMul.Mul(&chainId, u256.Num2)
signer.chainIDMul.Lsh(&chainId, 1) // ×2
case config.IsSpuriousDragon(blockNumber):
signer.protected = true
signer.chainID.Set(&chainId)
signer.chainIDMul.Mul(&chainId, u256.Num2)
signer.chainIDMul.Lsh(&chainId, 1) // ×2
case config.IsHomestead(blockNumber):
default:
// Only allow malleable transactions in Frontier
Expand Down Expand Up @@ -110,7 +110,7 @@ func LatestSigner(config *chain.Config) *Signer {
panic("chainID higher than 2^256-1")
}
signer.chainID.Set(chainId)
signer.chainIDMul.Mul(chainId, u256.Num2)
signer.chainIDMul.Lsh(chainId, 1) // ×2
if config.ChainID != nil {
if config.CancunTime != nil {
signer.blob = true
Expand Down Expand Up @@ -149,7 +149,7 @@ func LatestSignerForChainID(chainID *big.Int) *Signer {
panic("chainID higher than 2^256-1")
}
signer.chainID.Set(chainId)
signer.chainIDMul.Mul(chainId, u256.Num2)
signer.chainIDMul.Lsh(chainId, 1) // ×2
signer.protected = true
signer.accessList = true
signer.dynamicFee = true
Expand Down Expand Up @@ -397,5 +397,5 @@ func DeriveChainId(v *uint256.Int) *uint256.Int {
return new(uint256.Int).SetUint64((v - 35) / 2)
}
r := new(uint256.Int).Sub(v, u256.Num35)
return r.Div(r, u256.Num2)
return r.Rsh(r, 1) // ÷2
}
4 changes: 2 additions & 2 deletions execution/consensus/ethash/consensus.go
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Original file line number Diff line number Diff line change
Expand Up @@ -658,10 +658,10 @@ func AccumulateRewards(config *chain.Config, header *types.Header, uncles []*typ
r.Add(uncleNum, u256.Num8)
r.Sub(r, headerNum)
r.Mul(r, blockReward)
r.Div(r, u256.Num8)
r.Rsh(r, 3) // ÷8
uncleRewards = append(uncleRewards, *r)

r.Div(blockReward, u256.Num32)
r.Rsh(blockReward, 5) // ÷32
reward.Add(reward, r)
}
return *reward, uncleRewards
Expand Down
3 changes: 1 addition & 2 deletions txnprovider/shutter/internal/crypto/encryption.go
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Original file line number Diff line number Diff line change
Expand Up @@ -96,7 +96,6 @@ func fp12Exp(base *blst.Fp12, exp *big.Int) *blst.Fp12 {
result := &resultValue

zero := big.NewInt(0)
two := big.NewInt(2)

baseCopyValue := blst.Fp12One()
baseCopy := &baseCopyValue
Expand All @@ -108,7 +107,7 @@ func fp12Exp(base *blst.Fp12, exp *big.Int) *blst.Fp12 {
result.MulAssign(baseCopy)
}
baseCopy.MulAssign(baseCopy)
expCopy.Div(expCopy, two)
expCopy.Rsh(expCopy, 1) // ÷2
}

return result
Expand Down
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