Benchmark Timestamp Pallet (#4891)

* Add selected_benchmark! macro.

* Use selected_benchmark! in Identity pallet.

* Implement timestamp pallet benchmark.

* Fix some nits.

* Bump impl_version.

substrate/primitives/runtime/src/traits.rs

@@ -1333,6 +1333,55 @@ pub trait BenchmarkingSetup<T, Call, RawOrigin> {
 	fn instance(&self, components: &[(BenchmarkParameter, u32)]) -> Result<(Call, RawOrigin), &'static str>;
 }
 
+/// Creates a `SelectedBenchmark` enum implementing `BenchmarkingSetup`.
+///
+/// Every variant must implement [`BenchmarkingSetup`](crate::traits::BenchmarkingSetup).
+///
+/// ```nocompile
+///
+/// struct Transfer;
+/// impl BenchmarkingSetup for Transfer { ... }
+///
+/// struct SetBalance;
+/// impl BenchmarkingSetup for SetBalance { ... }
+///
+/// selected_benchmark!(Transfer, SetBalance);
+/// ```
+#[macro_export]
+macro_rules! selected_benchmark {
+	($($bench:ident),*) => {
+		// The list of available benchmarks for this pallet.
+		enum SelectedBenchmark {
+			$( $bench, )*
+		}
+
+		// Allow us to select a benchmark from the list of available benchmarks.
+		impl<T: Trait> $crate::traits::BenchmarkingSetup<T, Call<T>, RawOrigin<T::AccountId>> for SelectedBenchmark {
+			fn components(&self) -> Vec<(BenchmarkParameter, u32, u32)> {
+				match self {
+					$( Self::$bench => <$bench as $crate::traits::BenchmarkingSetup<
+						T,
+						Call<T>,
+						RawOrigin<T::AccountId>,
+					>>::components(&$bench), )*
+				}
+			}
+
+			fn instance(&self, components: &[(BenchmarkParameter, u32)])
+				-> Result<(Call<T>, RawOrigin<T::AccountId>), &'static str>
+			{
+				match self {
+					$( Self::$bench => <$bench as $crate::traits::BenchmarkingSetup<
+						T,
+						Call<T>,
+						RawOrigin<T::AccountId>,
+					>>::instance(&$bench, components), )*
+				}
+			}
+		}
+	};
+}
+
 #[cfg(test)]
 mod tests {
 	use super::*;