Harmony: implement Math.cbrt, Math.expm1 and Math.log1p.

test/mjsunit/harmony/math-log1p.js

+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --harmony-maths
+
+assertTrue(isNaN(Math.log1p(NaN)));
+assertTrue(isNaN(Math.log1p(function() {})));
+assertTrue(isNaN(Math.log1p({ toString: function() { return NaN; } })));
+assertTrue(isNaN(Math.log1p({ valueOf: function() { return "abc"; } })));
+assertEquals("Infinity", String(1/Math.log1p(0)));
+assertEquals("-Infinity", String(1/Math.log1p(-0)));
+assertEquals("Infinity", String(Math.log1p(Infinity)));
+assertEquals("-Infinity", String(Math.log1p(-1)));
+assertTrue(isNaN(Math.log1p(-2)));
+assertTrue(isNaN(Math.log1p(-Infinity)));
+
+for (var x = 1E300; x > 1E-1; x *= 0.8) {
+  var expected = Math.log(x + 1);
+  assertEqualsDelta(expected, Math.log1p(x), expected * 1E-14);
+}
+
+// Values close to 0:
+// Use Taylor expansion at 1 for log(x) as test expectation:
+// log1p(x) == log(x + 1) == 0 + x / 1 - x^2 / 2 + x^3 / 3 - ...
+function log1p(x) {
+  var terms = [];
+  var prod = x;
+  for (var i = 1; i <= 20; i++) {
+    terms.push(prod / i);
+    prod *= -x;
+  }
+  var sum = 0;
+  while (terms.length > 0) sum += terms.pop();
+  return sum;
+}
+
+for (var x = 1E-1; x > 1E-300; x *= 0.8) {
+  var expected = log1p(x);
+  assertEqualsDelta(expected, Math.log1p(x), expected * 1E-14);
+}