Fix floating point issues on Windows.

runtime/platform/floating_point_win.cc

Index: runtime/platform/floating_point_win.cc
diff --git a/runtime/platform/floating_point_win.cc b/runtime/platform/floating_point_win.cc
new file mode 100644
index 0000000000000000000000000000000000000000..01c3ff6773e9e60d1b1b149ed0f12bbec8bd2c03
--- /dev/null
+++ b/runtime/platform/floating_point_win.cc
@@ -0,0 +1,55 @@
+// Copyright (c) 2012, 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.
+
+#include <math.h>
+#include <limits>
+
+#include "platform/globals.h"
+
+// Taken from third_party/v8/src/platform-win32.cc
+double modulo(double x, double y) {
+  // Workaround MS fmod bugs. ECMA-262 says:

[Mads Ager (google), 2012/11/27 08:43:23]

Please remove the reference to the JavaScript spec here. This is not JS
specific.

[aam-me, 2012/11/28 00:45:34]

Done.

+  // dividend is finite and divisor is an infinity => result equals dividend
+  // dividend is a zero and divisor is nonzero finite => result equals dividend
+  if (!(_finite(x) && (!_finite(y) && !isnan(y))) &&
+      !(x == 0 && (y != 0 && _finite(y)))) {
+    x = fmod(x, y);
+  }
+  return x;
+}
+
+double round(double x) {
+  if (!_finite(x)) {
+    return x;
+  }
+
+  double intpart;
+  double fractpart = modf(x, &intpart);
+
+  if (fractpart >= 0.5) {
+    return (intpart + 1);

[Mads Ager (google), 2012/11/27 08:43:23]

I would remove the parenthesis here.

[aam-me, 2012/11/28 00:45:34]

Done.

+  } else if (fractpart > -0.5) {
+    return intpart;
+  } else {
+    return (intpart - 1);

[Mads Ager (google), 2012/11/27 08:43:23]

Ditto.

[aam-me, 2012/11/28 00:45:34]

Done.

+  }
+}
+
+
+// Bring MSVC atan2 behavior in line with standard.

[Mads Ager (google), 2012/11/27 08:43:23]

Expand comment to state that MSVC atan2 does not agree with standard at
infinities.

[aam-me, 2012/11/28 00:45:34]

Done.

+double atan2_ieee(double x, double y) {
+  int cls_x = _fpclass(x);
+  int cls_y = _fpclass(y);
+  if (((cls_x & (_FPCLASS_PINF | _FPCLASS_NINF)) != 0) &&
+      ((cls_y & (_FPCLASS_PINF | _FPCLASS_NINF)) != 0)) {
+    bool x_negative = (cls_x & _FPCLASS_NINF) != 0;
+    bool y_negative = (cls_y & _FPCLASS_NINF) != 0;
+    static double atans_at_infinities[2][2] =
+      { { atan2(1.,  1.), atan2(1.,  -1.) },
+        { atan2(-1., 1.), atan2(-1., -1.) } };
+    return atans_at_infinities[x_negative][y_negative];

[Mads Ager (google), 2012/11/27 08:43:23]

Please index with integers instead of booleans here.

[aam-me, 2012/11/28 00:45:34]

Done.

+  } else {
+    return atan2(x, y);
+  }
+}