core/vm: reuse bigint pools across transactions (#17070)

* core/vm: A pool for int pools

* core/vm: fix rebase issue

* core/vm: push leftover stack items after execution, not before

core/vm/intpool.go

@@ -16,7 +16,10 @@
 
 package vm
 
-import "math/big"
+import (
+	"math/big"
+	"sync"
+)
 
 var checkVal = big.NewInt(-42)
 
@@ -65,3 +68,39 @@ func (p *intPool) put(is ...*big.Int) {
 		p.pool.push(i)
 	}
 }
+
+// The intPool pool's default capacity
+const poolDefaultCap = 25
+
+// intPoolPool manages a pool of intPools.
+type intPoolPool struct {
+	pools []*intPool
+	lock  sync.Mutex
+}
+
+var poolOfIntPools = &intPoolPool{
+	pools: make([]*intPool, 0, poolDefaultCap),
+}
+
+// get is looking for an available pool to return.
+func (ipp *intPoolPool) get() *intPool {
+	ipp.lock.Lock()
+	defer ipp.lock.Unlock()
+
+	if len(poolOfIntPools.pools) > 0 {
+		ip := ipp.pools[len(ipp.pools)-1]
+		ipp.pools = ipp.pools[:len(ipp.pools)-1]
+		return ip
+	}
+	return newIntPool()
+}
+
+// put a pool that has been allocated with get.
+func (ipp *intPoolPool) put(ip *intPool) {
+	ipp.lock.Lock()
+	defer ipp.lock.Unlock()
+
+	if len(ipp.pools) < cap(ipp.pools) {
+		ipp.pools = append(ipp.pools, ip)
+	}
+}