Fix a bug that Math.round() returns incorrect results for huge integers.

test/mjsunit/math-round.js

Index: test/mjsunit/math-round.js
===================================================================
--- test/mjsunit/math-round.js	(revision 0)
+++ test/mjsunit/math-round.js	(revision 0)
@@ -0,0 +1,51 @@
+// Copyright 2010 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+assertEquals(0, Math.round(0));
+assertEquals(-0, Math.round(-0));
+assertEquals(Infinity, Math.round(Infinity));
+assertEquals(-Infinity, Math.round(-Infinity));
+assertNaN(Math.round(NaN));
+
+assertEquals(1, Math.round(0.5));
+assertEquals(1, Math.round(0.7));
+assertEquals(1, Math.round(1));
+assertEquals(1, Math.round(1.1));
+assertEquals(1, Math.round(1.49999));
+assertEquals(-Infinity, 1/Math.round(-0.5));
+assertEquals(-1, Math.round(-0.7));
+assertEquals(-1, Math.round(-1));
+assertEquals(-1, Math.round(-1.1));
+assertEquals(-1, Math.round(-1.49999));
+assertEquals(-1, Math.round(-1.5));
+
+assertEquals(9007199254740990, Math.round(9007199254740990));
+assertEquals(9007199254740991, Math.round(9007199254740991));
+assertEquals(-9007199254740990, Math.round(-9007199254740990));
+assertEquals(-9007199254740991, Math.round(-9007199254740991));
+assertEquals(Number.MAX_VALUE, Math.round(Number.MAX_VALUE));
+assertEquals(-Number.MAX_VALUE, Math.round(-Number.MAX_VALUE));