dart2js: Constant folding and specialization for remainder

tests/compiler/dart2js/modulo_remainder_test.dart

+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:async';
+import 'package:expect/expect.dart';
+import 'package:async_helper/async_helper.dart';
+import 'compiler_helper.dart';
+
+const String MOD1 = r"""
+foo(param) {
+  var a = param ? 0xFFFFFFFF : 1;
+  return a % 2;
+  // Unoptimized.
+  // present: '$mod'
+  // absent: '%'
+}
+""";
+
+const String MOD2 = r"""
+foo(param) {
+  var a = param ? 0xFFFFFFFF : 1;
+  return (a + 1) % 2;
+  // 'a + 1' cannot be -0.0, so we can optimize.
+  // present: ' % 2'
+  // absent: '$mod'
+}
+""";
+
+const String REM1 = r"""
+foo(param) {
+  var a = param ? 0xFFFFFFFF : 1;
+  return a.remainder(2);
+  // Above can be compiled to '%'.
+  // present: ' % 2'
+  // absent: 'remainder'
+}
+""";
+
+const String REM2 = r"""
+foo(param) {
+  var a = param ? 123.4 : -1;
+  return a.remainder(3);
+  // Above can be compiled to '%'.
+  // present: ' % 3'
+  // absent: 'remainder'
+}
+""";
+
+const String REM3 = r"""
+foo(param) {
+  var a = param ? 123 : null;
+  return 100.remainder(a);
+  // No specialization for possibly null inputs.
+  // present: 'remainder'
+  // absent: '%'
+}
+""";
+
+main() {
+  RegExp directivePattern = new RegExp(
+      //      \1                    \2        \3
+      r'''// *(present|absent): (?:"([^"]*)"|'([^'']*)')''',
+      multiLine: true);
+
+  Future check(String test) {
+    return compile(test, entry: 'foo', check: (String generated) {
+      for (Match match in directivePattern.allMatches(test)) {
+        String directive = match.group(1);
+        String pattern = match.groups([2, 3]).where((s) => s != null).single;
+        if (directive == 'present') {
+          Expect.isTrue(generated.contains(pattern),
+              "Cannot find '$pattern' in:\n$generated");
+        } else {
+          assert(directive == 'absent');
+          Expect.isFalse(generated.contains(pattern),
+              "Must not find '$pattern' in:\n$generated");
+        }
+      }
+    });
+  }
+
+  asyncTest(() => Future.wait([
+        check(MOD1),
+        check(MOD2),
+        check(REM1),
+        check(REM2),
+        check(REM3),
+      ]));
+}