Harmony: implement Math.sign.

Harmony: implement Math.sign.

R=dslomov@chromium.org
BUG=v8:2938
Committed: https://code.google.com/p/v8/source/detail?r=17279

[Dmitry Lomov (no reviews), 2013-10-21 06:57:58]

LGTM with a request for test.

https://codereview.chromium.org/28723002/diff/40001/test/mjsunit/harmony/math...
File test/mjsunit/harmony/math-sign.js (right):

https://codereview.chromium.org/28723002/diff/40001/test/mjsunit/harmony/math...
test/mjsunit/harmony/math-sign.js:30: assertEquals("Infinity",
String(1/Math.sign(0)));
Needs tests for +0 and -0:
var x = 1e-200
var y = -1e-200
var z = x*y // -0, confirm by 1/z == -Infinity
Math.sign(z);

[Sven Panne, 2013-10-21 07:18:38]

https://codereview.chromium.org/28723002/diff/40001/test/mjsunit/harmony/math...
File test/mjsunit/harmony/math-sign.js (right):

https://codereview.chromium.org/28723002/diff/40001/test/mjsunit/harmony/math...
test/mjsunit/harmony/math-sign.js:30: assertEquals("Infinity",
String(1/Math.sign(0)));
On 2013/10/21 06:57:58, Dmitry Lomov (chromium) wrote:
> Needs tests for +0 and -0:
> var x = 1e-200
> var y = -1e-200
> var z = x*y // -0, confirm by 1/z == -Infinity
> Math.sign(z);

Why do we need this? I thought the line below already tests exactly this.

[Yang, 2013-10-21 07:53:22]

https://codereview.chromium.org/28723002/diff/40001/test/mjsunit/harmony/math...
File test/mjsunit/harmony/math-sign.js (right):

https://codereview.chromium.org/28723002/diff/40001/test/mjsunit/harmony/math...
test/mjsunit/harmony/math-sign.js:30: assertEquals("Infinity",
String(1/Math.sign(0)));
On 2013/10/21 07:18:39, Sven Panne wrote:
> On 2013/10/21 06:57:58, Dmitry Lomov (chromium) wrote:
> > Needs tests for +0 and -0:
> > var x = 1e-200
> > var y = -1e-200
> > var z = x*y // -0, confirm by 1/z == -Infinity
> > Math.sign(z);
> 
> Why do we need this? I thought the line below already tests exactly this.

The line below does test the -0 case. Using actual -0 seems better than going
out of the double range to get it.

[Dmitry Lomov (no reviews), 2013-10-21 08:11:06]

On 2013/10/21 07:53:22, Yang wrote:
>
https://codereview.chromium.org/28723002/diff/40001/test/mjsunit/harmony/math...
> File test/mjsunit/harmony/math-sign.js (right):
> 
>
https://codereview.chromium.org/28723002/diff/40001/test/mjsunit/harmony/math...
> test/mjsunit/harmony/math-sign.js:30: assertEquals("Infinity",
> String(1/Math.sign(0)));
> On 2013/10/21 07:18:39, Sven Panne wrote:
> > On 2013/10/21 06:57:58, Dmitry Lomov (chromium) wrote:
> > > Needs tests for +0 and -0:
> > > var x = 1e-200
> > > var y = -1e-200
> > > var z = x*y // -0, confirm by 1/z == -Infinity
> > > Math.sign(z);
> > 
> > Why do we need this? I thought the line below already tests exactly this.
> 
> The line below does test the -0 case. Using actual -0 seems better than going
> out of the double range to get it.

Ok, fair enough.

[Yang, 2013-10-21 09:16:39]

Committed patchset #2 manually as r17279 (presubmit successful).