Add a benchmark for protocol conformance testing.

Author: mikeash

benchmark/CMakeLists.txt

@@ -136,6 +136,7 @@ set(SWIFT_BENCH_MODULES
     single-source/PrefixWhile
     single-source/Prims
     single-source/PrimsNonStrongRef
+    single-source/ProtocolConformance
     single-source/ProtocolDispatch
     single-source/ProtocolDispatch2
     single-source/Queue

benchmark/single-source/ProtocolConformance.swift

@@ -0,0 +1,76 @@
+//===--- ProtocolDispatch.swift -------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2020 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import TestsUtils
+
+public let ProtocolConformance = BenchmarkInfo (
+  name: "ProtocolConformance",
+  runFunction: run_ProtocolConformance,
+  tags: [.validation, .runtime])
+
+protocol P {}
+
+struct One: P {}
+struct Two {}
+
+struct Cat<T, U> {}
+
+extension Cat: P where T: P, U: P {}
+
+protocol Growable {}
+extension Growable {
+  func grow() -> (Growable, Growable) {
+    return (Cat<Self, One>(), Cat<Self, Two>())
+  }
+}
+
+extension One: Growable {}
+extension Two: Growable {}
+extension Cat: Growable {}
+
+@inline(never)
+public func run_ProtocolConformance(_ N: Int) {
+  var array: [Growable] = [One(), Two()]
+  var i = 0
+  var checks = 0
+
+  // The expected number of times we expect `elt is P` to be true.
+  var expectedConforms = 0
+
+  // The expected number of times we expect `elt is P` to be true
+  // per iteration, at the current time.
+  var expectedConformsPerIter = 1
+
+  // The number of times we've actually seen `elt is P` be true.
+  var conforms = 0
+  while checks < N * 500 {
+    let (a, b) = array[i].grow()
+    array.append(a)
+    array.append(b)
+
+    // The number of times `elt is P` is true per outer iteration
+    // goes up by 1 when the array's count is a power of 2.
+    if array.count & (array.count - 1) == 0 {
+      expectedConformsPerIter += 1
+    }
+    expectedConforms += expectedConformsPerIter
+
+    for elt in array {
+      if elt is P {
+        conforms += 1
+      }
+      checks += 1
+    }
+    i += 1
+  }
+  CheckResults(expectedConforms == conforms)
+}

benchmark/utils/main.swift

@@ -131,6 +131,7 @@ import PrefixWhile
 import Prims
 import PrimsNonStrongRef
 import PrimsSplit
+import ProtocolConformance
 import ProtocolDispatch
 import ProtocolDispatch2
 import Queue
@@ -317,6 +318,7 @@ registerBenchmark(PrefixWhile)
 registerBenchmark(Prims)
 registerBenchmark(PrimsNonStrongRef)
 registerBenchmark(PrimsSplit)
+registerBenchmark(ProtocolConformance)
 registerBenchmark(ProtocolDispatch)
 registerBenchmark(ProtocolDispatch2)
 registerBenchmark(QueueGeneric)