perf(bls12-381-gurvy): Optimize BLS12-381-GURVY Zr using fr.Element (reduce allocations)

driver/common/curve.go

@@ -119,3 +119,15 @@ func (p *CurveBase) ModAddMul3(a1 driver.Zr, a2 driver.Zr, b1 driver.Zr, b2 driv
 		m,
 	)
 }
+
+func (p *CurveBase) ModMulInPlace(result, a, b, m driver.Zr) {
+	result.Clone(p.ModMul(a, b, m))
+}
+
+func (p *CurveBase) ModAddMul2InPlace(result driver.Zr, a1, c1, b1, c2, m driver.Zr) {
+	result.Clone(p.ModAddMul2(a1, c1, b1, c2, m))
+}
+
+func (p *CurveBase) ModAddMul3InPlace(result driver.Zr, a1, a2, b1, b2, c1, c2, m driver.Zr) {
+	result.Clone(p.ModAddMul3(a1, a2, b1, b2, c1, c2, m))
+}

driver/gurvy/bls12381/bipool.go

@@ -0,0 +1,36 @@
+/*
+Copyright IBM Corp. All Rights Reserved.
+
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package bls12381
+
+import (
+	"math/big"
+	"sync"
+)
+
+// bigIntPool is a shared *big.Int memory pool for temporary conversions
+var bigIntPool biPool
+
+var _bigIntPool = sync.Pool{
+	New: func() interface{} {
+		return new(big.Int)
+	},
+}
+
+type biPool struct{}
+
+func (biPool) Get() *big.Int {
+	return _bigIntPool.Get().(*big.Int)
+}
+
+func (biPool) Put(v *big.Int) {
+	if v == nil {
+		panic("put called with nil value")
+	}
+	// reset v before putting it back
+	v.SetInt64(0)
+	_bigIntPool.Put(v)
+}