Slight change to Math.sin approximation.

src/math.js

 // Copyright 2012 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 202 matching lines @@
 var InitTrigonometricFunctions;
 
 
 // Define constants and interpolation functions.
 // Also define the initialization function that populates the lookup table
 // and then wires up the function definitions.
 function SetupTrigonometricFunctions() {
   var samples = 1800;  // Table size.
   var pi = 3.1415926535897932;
   var pi_half = pi / 2;
-  var inverse_pi_half = 1 / pi_half;
-  var two_pi = pi * 2;
+  var inverse_pi_half = 2 / pi;
+  var two_pi = 2 * pi;
+  var four_pi = 4 * pi;
   var interval = pi_half / samples;
   var inverse_interval = samples / pi_half;
   var table_sin;
   var table_cos_interval;
 
   // This implements sine using the following algorithm.
   // 1) Multiplication takes care of to-number conversion.
   // 2) Reduce x to the first quadrant [0, pi/2].
   //    Conveniently enough, in case of +/-Infinity, we get NaN.
   // 3) Replace x by (pi/2-x) if x was in the 2nd or 4th quadrant.
@@ skipping 10 matching lines @@
     var t2 = 1 - t1;
     var y1 = table_sin[index];
     var y2 = table_sin[index + 1];
     var dy = y2 - y1;
     return (t2 * y1 + t1 * y2 +
                 t1 * t2 * ((table_cos_interval[index] - dy) * t2 +
                            (dy - table_cos_interval[index + 1]) * t1));
   }
 
   var MathSinInterpolation = function(x) {
+    if (x > four_pi) x -= four_pi;

[Jakob Kummerow, 2013/11/13 16:09:28]

I think this needs a comment. Roughly:

// Sunspider @#$§ !!!

     var multiple = MathFloor(x * inverse_pi_half);
     if (%_IsMinusZero(multiple)) return multiple;
     x = (multiple & 1) * pi_half +
         (1 - ((multiple & 1) << 1)) * (x - multiple * pi_half);
     return Interpolation(x) * (1 - (multiple & 2)) + 0;
   }
 
   // Cosine is sine with a phase offset of pi/2.
   var MathCosInterpolation = function(x) {
     var multiple = MathFloor(x * inverse_pi_half);
@@ skipping 91 matching lines @@
     "min", MathMin,
     "imul", MathImul
   ));
 
   %SetInlineBuiltinFlag(MathSin);
   %SetInlineBuiltinFlag(MathCos);
   %SetInlineBuiltinFlag(MathTan);
 }
 
 SetUpMath();