Fix 23563: double unary- operator unstable for NANs

tests/language/nan_identical_test.dart

+// Copyright (c) 2015, 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.
+// Test a new statement by itself.
+// VMOptions=--optimization-counter-threshold=4 --no-use-osr
+
+import 'dart:typed_data';
+
+import "package:expect/expect.dart";
+
+double uint64toDouble(int i) {
+  var buffer = new Uint8List(8).buffer;
+  var bdata = new ByteData.view(buffer);
+  bdata.setUint64(0, i);
+  return bdata.getFloat64(0);
+}
+
+double createOtherNAN() {
+  return uint64toDouble((1 << 64) - 2);
+}
+
+main() {
+  var otherNAN = createOtherNAN();
+  for (int i = 0; i < 100; i++) {
+    Expect.isFalse(checkIdentical(double.NAN, -double.NAN));
+    Expect.isTrue(checkIdentical(double.NAN, double.NAN));
+    Expect.isTrue(checkIdentical(-double.NAN, -double.NAN));
+
+    Expect.isFalse(checkIdentical(otherNAN, -otherNAN));
+    Expect.isTrue(checkIdentical(otherNAN, otherNAN));
+    Expect.isTrue(checkIdentical(-otherNAN, -otherNAN));
+
+    var a = otherNAN;
+    var b = double.NAN;
+    Expect.isFalse(checkIdentical(a, b));
+    Expect.isFalse(checkIdentical(-a, -b));
+    Expect.isFalse(checkIdentical(-a, b));
+    Expect.isFalse(checkIdentical(a, -b));
+
+    a = -a;
+    Expect.isFalse(checkIdentical(a, b));
+    Expect.isFalse(checkIdentical(-a, -b));
+    Expect.isFalse(checkIdentical(-a, b));
+    Expect.isFalse(checkIdentical(a, -b));
+
+    Expect.isTrue(checkIdentical(-(-a), a));
+    Expect.isTrue(checkIdentical(-(-b), b));
+  }
+}
+
+checkIdentical(a, b) => identical(a, b);