Contracts: Only exec parsed code in benchmarks (#3915)

[Weights
compare](https://weights.tasty.limo/compare?unit=weight&ignore_errors=true&threshold=10&method=asymptotic&repo=polkadot-sdk&old=master&new=pg%2Fbench_tweaks&path_pattern=substrate%2Fframe%2F**%2Fsrc%2Fweights.rs%2Cpolkadot%2Fruntime%2F*%2Fsrc%2Fweights%2F**%2F*.rs%2Cpolkadot%2Fbridges%2Fmodules%2F*%2Fsrc%2Fweights.rs%2Ccumulus%2F**%2Fweights%2F*.rs%2Ccumulus%2F**%2Fweights%2Fxcm%2F*.rs%2Ccumulus%2F**%2Fsrc%2Fweights.rs)

Note: Raw weights change does not mean much here, as this PR reduce the
scope of what is benchmarked, they are therefore decreased by a good
margin. One should instead print the Schedule using

cargo test --features runtime-benchmarks bench_print_schedule --
--nocapture
or following the instructions from the
[README](https://github.com/paritytech/polkadot-sdk/tree/pg/bench_tweaks/substrate/frame/contracts#schedule)
for looking at the Schedule of a specific runtime

---------

Co-authored-by: command-bot <>

substrate/frame/contracts/src/benchmarking/call_builder.rs

@@ -0,0 +1,170 @@
+// This file is part of Substrate.
+
+// Copyright (C) Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use crate::{
+	benchmarking::{Contract, WasmModule},
+	exec::Stack,
+	storage::meter::Meter,
+	wasm::Runtime,
+	BalanceOf, Config, DebugBufferVec, Determinism, ExecReturnValue, GasMeter, Origin, Schedule,
+	TypeInfo, WasmBlob, Weight,
+};
+use codec::{Encode, HasCompact};
+use core::fmt::Debug;
+use sp_core::Get;
+use sp_std::prelude::*;
+
+type StackExt<'a, T> = Stack<'a, T, WasmBlob<T>>;
+
+/// A prepared contract call ready to be executed.
+pub struct PreparedCall<'a, T: Config> {
+	func: wasmi::Func,
+	store: wasmi::Store<Runtime<'a, StackExt<'a, T>>>,
+}
+
+impl<'a, T: Config> PreparedCall<'a, T> {
+	pub fn call(mut self) -> ExecReturnValue {
+		let result = self.func.call(&mut self.store, &[], &mut []);
+		WasmBlob::<T>::process_result(self.store, result).unwrap()
+	}
+}
+
+/// A builder used to prepare a contract call.
+pub struct CallSetup<T: Config> {
+	contract: Contract<T>,
+	dest: T::AccountId,
+	origin: Origin<T>,
+	gas_meter: GasMeter<T>,
+	storage_meter: Meter<T>,
+	schedule: Schedule<T>,
+	value: BalanceOf<T>,
+	debug_message: Option<DebugBufferVec<T>>,
+	determinism: Determinism,
+	data: Vec<u8>,
+}
+
+impl<T> CallSetup<T>
+where
+	T: Config + pallet_balances::Config,
+	<BalanceOf<T> as HasCompact>::Type: Clone + Eq + PartialEq + Debug + TypeInfo + Encode,
+{
+	/// Setup a new call for the given module.
+	pub fn new(module: WasmModule<T>) -> Self {
+		let contract = Contract::<T>::new(module.clone(), vec![]).unwrap();
+		let dest = contract.account_id.clone();
+		let origin = Origin::from_account_id(contract.caller.clone());
+
+		let storage_meter = Meter::new(&origin, None, 0u32.into()).unwrap();
+
+		Self {
+			contract,
+			dest,
+			origin,
+			gas_meter: GasMeter::new(Weight::MAX),
+			storage_meter,
+			schedule: T::Schedule::get(),
+			value: 0u32.into(),
+			debug_message: None,
+			determinism: Determinism::Enforced,
+			data: vec![],
+		}
+	}
+
+	/// Set the meter's storage deposit limit.
+	pub fn set_storage_deposit_limit(&mut self, balance: BalanceOf<T>) {
+		self.storage_meter = Meter::new(&self.origin, Some(balance), 0u32.into()).unwrap();
+	}
+
+	/// Set the call's origin.
+	pub fn set_origin(&mut self, origin: Origin<T>) {
+		self.origin = origin;
+	}
+
+	/// Set the contract's balance.
+	pub fn set_balance(&mut self, value: BalanceOf<T>) {
+		self.contract.set_balance(value);
+	}
+
+	/// Set the call's input data.
+	pub fn set_data(&mut self, value: Vec<u8>) {
+		self.data = value;
+	}
+
+	/// Set the debug message.
+	pub fn enable_debug_message(&mut self) {
+		self.debug_message = Some(Default::default());
+	}
+
+	/// Get the debug message.
+	pub fn debug_message(&self) -> Option<DebugBufferVec<T>> {
+		self.debug_message.clone()
+	}
+
+	/// Get the call's input data.
+	pub fn data(&self) -> Vec<u8> {
+		self.data.clone()
+	}
+
+	/// Get the call's contract.
+	pub fn contract(&self) -> Contract<T> {
+		self.contract.clone()
+	}
+
+	/// Build the call stack.
+	pub fn ext(&mut self) -> (StackExt<'_, T>, WasmBlob<T>) {
+		StackExt::bench_new_call(
+			self.dest.clone(),
+			self.origin.clone(),
+			&mut self.gas_meter,
+			&mut self.storage_meter,
+			&self.schedule,
+			self.value,
+			self.debug_message.as_mut(),
+			self.determinism,
+		)
+	}
+
+	/// Prepare a call to the module.
+	pub fn prepare_call<'a>(
+		ext: &'a mut StackExt<'a, T>,
+		module: WasmBlob<T>,
+		input: Vec<u8>,
+	) -> PreparedCall<'a, T> {
+		let (func, store) = module.bench_prepare_call(ext, input);
+		PreparedCall { func, store }
+	}
+}
+
+#[macro_export]
+macro_rules! call_builder(
+	($func: ident, $module:expr) => {
+		$crate::call_builder!($func, _contract, $module);
+	};
+	($func: ident, $contract: ident, $module:expr) => {
+		let mut setup = CallSetup::<T>::new($module);
+		$crate::call_builder!($func, $contract, setup: setup);
+	};
+    ($func:ident, setup: $setup: ident) => {
+		$crate::call_builder!($func, _contract, setup: $setup);
+	};
+    ($func:ident, $contract: ident, setup: $setup: ident) => {
+		let data = $setup.data();
+		let $contract = $setup.contract();
+		let (mut ext, module) = $setup.ext();
+		let $func = CallSetup::<T>::prepare_call(&mut ext, module, data);
+	};
+);