Port fdlibm implementation for Math.cosh.

test/mjsunit/es6/math-hyperbolic.js

 // Copyright 2013 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
@@ skipping 84 matching lines @@
 assertEquals(0, Math.acosh(1));
 assertEquals("Infinity", String(Math.acosh(Infinity)));
 
 // Math.acosh(x) is NaN for x < 1
 [0.99999999999, 0.2, -1000, 0, -0].forEach(function(x) {
   assertTrue(isNaN(Math.acosh(x)));
 });
 
 
 // Some random samples.
-assertEqualsDelta(74.203210577788, Math.sinh(5), 1E-12);
-assertEqualsDelta(-74.203210577788, Math.sinh(-5), 1E-12);
+assertEqualsDelta(74.20321057778875, Math.sinh(5), 1E-12);
+assertEqualsDelta(-74.20321057778875, Math.sinh(-5), 1E-12);
 
-assertEqualsDelta(1.1276259652063, Math.cosh(0.5), 1E-12);
-assertEqualsDelta(74.209948524787, Math.cosh(5), 1E-12);
-assertEqualsDelta(1.1276259652063, Math.cosh(-0.5), 1E-12);
-assertEqualsDelta(74.209948524787, Math.cosh(-5), 1E-12);
+assertEqualsDelta(1.1276259652063807, Math.cosh(0.5), 1E-12);
+assertEqualsDelta(74.20994852478785, Math.cosh(5), 1E-12);
+assertEqualsDelta1.1276259652063807, Math.cosh(-0.5), 1E-12);
+assertEqualsDelta(74.20994852478785, Math.cosh(-5), 1E-12);
 
 assertEqualsDelta(0.4621171572600, Math.tanh(0.5), 1E-12);
 assertEqualsDelta(0.9999092042625, Math.tanh(5), 1E-12);
 assertEqualsDelta(-0.4621171572600, Math.tanh(-0.5), 1E-12);
 assertEqualsDelta(-0.9999092042625, Math.tanh(-5), 1E-12);
 
 assertEqualsDelta(0.4812118250596, Math.asinh(0.5), 1E-12);
 assertEqualsDelta(2.3124383412727, Math.asinh(5), 1E-12);
 assertEqualsDelta(-0.4812118250596, Math.asinh(-0.5), 1E-12);
 assertEqualsDelta(-2.3124383412727, Math.asinh(-5), 1E-12);
@@ skipping 37 matching lines @@
 assertEquals(1.3440585709080678e43, Math.sinh(100));
 assertEquals(-1.3440585709080678e43, Math.sinh(-100));
 // No overflow, case |x| in [log(maxdouble), threshold]
 assertEquals(1.7976931348621744e308, Math.sinh(710.4758600739439));
 assertEquals(-1.7976931348621744e308, Math.sinh(-710.4758600739439));
 // Overflow, case |x| > threshold
 assertEquals(Infinity, Math.sinh(710.475860073944));
 assertEquals(-Infinity, Math.sinh(-710.475860073944));
 assertEquals(Infinity, Math.sinh(1000));
 assertEquals(-Infinity, Math.sinh(-1000));
+
+// Implementation-specific tests for cosh.
+// Case |x| < 2^-55
+assertEquals(1, Math.cosh(Math.pow(2, -56)));
+assertEquals(1, Math.cosh(-Math.pow(2, -56)));
+// Case |x| < 1/2*log(2). cosh(Math.LN2/4) = (sqrt(2)+1)/2^(5/4)
+assertEquals(1.0150517651282178, Math.cosh(Math.LN2/4));
+assertEquals(1.0150517651282178, Math.cosh(-Math.LN2/4));
+// Case 1/2*log(2) < |x| < 22. cosh(10*Math.LN2) = 1048577/2048
+assertEquals(512.00048828125, Math.cosh(10*Math.LN2));
+assertEquals(512.00048828125, Math.cosh(-10*Math.LN2));
+// Case 22 <= |x| < log(maxdouble)
+assertEquals(2.1474836479999983e9, Math.cosh(32*Math.LN2));
+assertEquals(2.1474836479999983e9, Math.cosh(-32*Math.LN2));
+// Case log(maxdouble) <= |x| <= overflowthreshold
+assertEquals(1.7976931348621744e308, Math.cosh(710.4758600739439));
+assertEquals(1.7976931348621744e308, Math.cosh(-710.4758600739439));
+// Overflow.
+assertEquals(Infinity, Math.cosh(710.475860073944));
+assertEquals(Infinity, Math.cosh(-710.475860073944));