Add benchmark for effect merging (#1310)

* Add benchmark for effect merging

* wip

* wip

* wip

(cherry picked from commit 2389b821a8ab1f4b549788ff1f4678cc6a2e75e4)

Author: stephencelis

Sources/swift-composable-architecture-benchmark/Common.swift

@@ -0,0 +1,54 @@
+import Benchmark
+
+extension BenchmarkSuite {
+  func benchmark(
+    _ name: String,
+    run: @escaping () throws -> Void,
+    setUp: @escaping () -> Void = {},
+    tearDown: @escaping () -> Void
+  ) {
+    self.register(
+      benchmark: Benchmarking(name: name, run: run, setUp: setUp, tearDown: tearDown)
+    )
+  }
+}
+
+struct Benchmarking: AnyBenchmark {
+  let name: String
+  let settings: [BenchmarkSetting] = []
+  private let _run: () throws -> Void
+  private let _setUp: () -> Void
+  private let _tearDown: () -> Void
+
+  init(
+    name: String,
+    run: @escaping () throws -> Void,
+    setUp: @escaping () -> Void = {},
+    tearDown: @escaping () -> Void = {}
+  ) {
+    self.name = name
+    self._run = run
+    self._setUp = setUp
+    self._tearDown = tearDown
+  }
+
+  func setUp() {
+    self._setUp()
+  }
+
+  func run(_ state: inout BenchmarkState) throws {
+    try self._run()
+  }
+
+  func tearDown() {
+    self._tearDown()
+  }
+}
+
+@inline(__always)
+func doNotOptimizeAway<T>(_ x: T) {
+  @_optimize(none)
+  func assumePointeeIsRead(_ x: UnsafeRawPointer) {}
+
+  withUnsafePointer(to: x) { assumePointeeIsRead($0) }
+}

Sources/swift-composable-architecture-benchmark/Effects.swift

@@ -0,0 +1,28 @@
+import Benchmark
+import Combine
+import ComposableArchitecture
+import Foundation
+
+let effectSuite = BenchmarkSuite(name: "Effects") {
+  $0.benchmark("Merged Effect.none (create, flat)") {
+    doNotOptimizeAway(Effect<Int, Never>.merge((1...100).map { _ in .none }))
+  }
+
+  $0.benchmark("Merged Effect.none (create, nested)") {
+    var effect = Effect<Int, Never>.none
+    for _ in 1...100 {
+      effect = .merge(effect, .none)
+    }
+    doNotOptimizeAway(effect)
+  }
+
+  let effect = Effect<Int, Never>.merge((1...100).map { _ in .none })
+  var didComplete = false
+  $0.benchmark("Merged Effect.none (sink)") {
+    doNotOptimizeAway(
+      effect.sink(receiveCompletion: { _ in didComplete = true }, receiveValue: { _ in })
+    )
+  } tearDown: {
+    precondition(didComplete)
+  }
+}

Sources/swift-composable-architecture-benchmark/main.swift

@@ -39,4 +39,7 @@ benchmark("Scoping (4)") {
   viewStore4.send(true)
 }
 
-Benchmark.main()
+Benchmark.main([
+  defaultBenchmarkSuite,
+  effectSuite,
+])