From 39f874d03f3d327acb377273b6ad43cf9427376a Mon Sep 17 00:00:00 2001
From: Roman Khimov <roman@nspcc.ru>
Date: Thu, 5 Aug 2021 09:59:48 +0300
Subject: [PATCH] core: don't recalculate witness script hash
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We know it already, but with current loading code VM will hash it once
more. It doesn't help a lot and still it costs nothing to avoid this
overhead.

name             old time/op    new time/op    delta
VerifyWitness-8    93.4µs ± 3%    92.7µs ± 2%    ~     (p=0.353 n=10+10)

name             old alloc/op   new alloc/op   delta
VerifyWitness-8    3.43kB ± 0%    3.40kB ± 0%  -0.70%  (p=0.000 n=9+9)

name             old allocs/op  new allocs/op  delta
VerifyWitness-8      67.0 ± 0%      66.0 ± 0%  -1.49%  (p=0.000 n=10+10)
---
 pkg/core/bench_test.go | 24 ++++++++++++++++++++++++
 pkg/core/blockchain.go |  2 +-
 2 files changed, 25 insertions(+), 1 deletion(-)
 create mode 100644 pkg/core/bench_test.go

diff --git a/pkg/core/bench_test.go b/pkg/core/bench_test.go
new file mode 100644
index 000000000..24beadb32
--- /dev/null
+++ b/pkg/core/bench_test.go
@@ -0,0 +1,24 @@
+package core
+
+import (
+	"testing"
+
+	"github.com/nspcc-dev/neo-go/pkg/config/netmode"
+	"github.com/nspcc-dev/neo-go/pkg/vm/opcode"
+	"github.com/nspcc-dev/neo-go/pkg/wallet"
+	"github.com/stretchr/testify/require"
+)
+
+func BenchmarkVerifyWitness(t *testing.B) {
+	bc := newTestChain(t)
+	acc, err := wallet.NewAccount()
+	require.NoError(t, err)
+
+	tx := bc.newTestTx(acc.Contract.ScriptHash(), []byte{byte(opcode.PUSH1)})
+	require.NoError(t, acc.SignTx(netmode.UnitTestNet, tx))
+
+	t.ResetTimer()
+	for n := 0; n < t.N; n++ {
+		_ = bc.VerifyWitness(tx.Signers[0].Account, tx, &tx.Scripts[0], 100000000)
+	}
+}
diff --git a/pkg/core/blockchain.go b/pkg/core/blockchain.go
index 00a7f58be..f9e9f3072 100644
--- a/pkg/core/blockchain.go
+++ b/pkg/core/blockchain.go
@@ -1837,7 +1837,7 @@ func (bc *Blockchain) InitVerificationVM(v *vm.VM, getContract func(util.Uint160
 		if err != nil {
 			return fmt.Errorf("%w: %v", ErrInvalidVerification, err)
 		}
-		v.LoadScriptWithFlags(witness.VerificationScript, callflag.ReadOnly)
+		v.LoadScriptWithHash(witness.VerificationScript, hash, callflag.ReadOnly)
 	} else {
 		cs, err := getContract(hash)
 		if err != nil {