core: optimize contractCallEx

Provide script hash upon script load.

pkg/core/interop_system.go

@@ -442,7 +442,7 @@ func contractCallExInternal(ic *interop.Context, v *vm.VM, h []byte, method stac
 			return errors.New("disallowed method call")
 		}
 	}
-	v.LoadScript(cs.Script)
+	v.LoadScriptWithHash(cs.Script, u)
 	v.Estack().PushVal(args)
 	v.Estack().PushVal(method)
 	return nil

pkg/vm/vm.go

@@ -268,6 +268,15 @@ func (v *VM) LoadScript(b []byte) {
 	v.istack.PushVal(ctx)
 }
 
+// LoadScriptWithHash if similar to the LoadScript method, but it also loads
+// given script hash directly into the Context to avoid its recalculations. It's
+// up to user of this function to make sure the script and hash match each other.
+func (v *VM) LoadScriptWithHash(b []byte, hash util.Uint160) {
+	v.LoadScript(b)
+	ctx := v.Context()
+	ctx.scriptHash = hash
+}
+
 // Context returns the current executed context. Nil if there is no context,
 // which implies no program is loaded.
 func (v *VM) Context() *Context {