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_test.go

@@ -0,0 +1,55 @@
+// Copyright 2018 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package vm
+
+import (
+	"testing"
+)
+
+func TestIntPoolPoolGet(t *testing.T) {
+	poolOfIntPools.pools = make([]*intPool, 0, poolDefaultCap)
+
+	nip := poolOfIntPools.get()
+	if nip == nil {
+		t.Fatalf("Invalid pool allocation")
+	}
+}
+
+func TestIntPoolPoolPut(t *testing.T) {
+	poolOfIntPools.pools = make([]*intPool, 0, poolDefaultCap)
+
+	nip := poolOfIntPools.get()
+	if len(poolOfIntPools.pools) != 0 {
+		t.Fatalf("Pool got added to list when none should have been")
+	}
+
+	poolOfIntPools.put(nip)
+	if len(poolOfIntPools.pools) == 0 {
+		t.Fatalf("Pool did not get added to list when one should have been")
+	}
+}
+
+func TestIntPoolPoolReUse(t *testing.T) {
+	poolOfIntPools.pools = make([]*intPool, 0, poolDefaultCap)
+	nip := poolOfIntPools.get()
+	poolOfIntPools.put(nip)
+	poolOfIntPools.get()
+
+	if len(poolOfIntPools.pools) != 0 {
+		t.Fatalf("Invalid number of pools. Got %d, expected %d", len(poolOfIntPools.pools), 0)
+	}
+}