Add benchmark for UTF-8 decoding

Author: PatrickPijnappel

benchmark/CMakeLists.txt

@@ -85,6 +85,7 @@ set(SWIFT_BENCH_MODULES
     single-source/SuperChars
     single-source/TwoSum
     single-source/TypeFlood
+    single-source/UTF8Decode
     single-source/Walsh
     single-source/XorLoop
 )

benchmark/single-source/UTF8Decode.swift

@@ -0,0 +1,26 @@
+//===--- UTF8Decode.swift -------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2016 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See http://swift.org/LICENSE.txt for license information
+// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import TestsUtils
+
+@inline(never)
+public func run_UTF8Decode(N: Int) {
+  // Use test data with UTF-8 sequences of all lengths, but mainly ASCII.
+  let string = "Mainly ASCII but also some 2-byte sequences (пример),"
+    + " some 3-bytes sequences (성능 테스트) and occasionally a 🐼 (4 bytes)"
+  let data = Array(string.utf8)
+  for _ in 1...N {
+    var generator = data.generate()
+    var utf8 = UTF8()
+    while !utf8.decode(&generator).isEmptyInput() { }
+  }
+}

benchmark/utils/main.swift

@@ -90,6 +90,7 @@ import StringWalk
 import SuperChars
 import TwoSum
 import TypeFlood
+import UTF8Decode
 import Walsh
 import XorLoop
 
@@ -171,6 +172,7 @@ precommitTests = [
   "SuperChars": run_SuperChars,
   "TwoSum": run_TwoSum,
   "TypeFlood": run_TypeFlood,
+  "UTF8Decode": run_UTF8Decode,
   "Walsh": run_Walsh,
   "XorLoop": run_XorLoop,
 ]