[turbofan] Add support for Math.round to the JSBuiltinReducer.

[turbofan] Add support for Math.round to the JSBuiltinReducer.

We can reduce Math.round(v) to a sequence of

  let i = Float64RoundUp(v);
  let r = i - v;
  return r > 0.5 ? 1.0 + i : i;

if the target supports the Float64RoundUp machine operator (i.e.
roundsd with RoundUp rounding on Intel processors with SSE4.1).

R=jarin@chromium.org

Committed: https://crrev.com/f8ece9a01384d83737ba7f79999fc95bf5529efa
Cr-Commit-Position: refs/heads/master@{#33572}

[Benedikt Meurer, 2016-01-27 18:39:44]

Hey Jaro,

Another easy one. We're even better than Crankshaft in this case, which just
tries to represent the result as int32 and runs into a deopt loop if the result
cannot be represented as int32.
Please take a look.

Thanks,
Benedikt

[Jarin, 2016-01-28 05:19:17]

lgtm

[Benedikt Meurer, 2016-01-28 05:20:58]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2016-01-28 05:21:08]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1640393002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1640393002/1

[commit-bot: I haz the power, 2016-01-28 05:23:12]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-01-28 05:23:22]

Description was changed from

==========
[turbofan] Add support for Math.round to the JSBuiltinReducer.

We can reduce Math.round(v) to a sequence of

  let i = Float64RoundUp(v);
  let r = i - v;
  return r > 0.5 ? 1.0 + i : i;

if the target supports the Float64RoundUp machine operator (i.e.
roundsd with RoundUp rounding on Intel processors with SSE4.1).

R=jarin@chromium.org
==========

to

==========
[turbofan] Add support for Math.round to the JSBuiltinReducer.

We can reduce Math.round(v) to a sequence of

  let i = Float64RoundUp(v);
  let r = i - v;
  return r > 0.5 ? 1.0 + i : i;

if the target supports the Float64RoundUp machine operator (i.e.
roundsd with RoundUp rounding on Intel processors with SSE4.1).

R=jarin@chromium.org

Committed: https://crrev.com/f8ece9a01384d83737ba7f79999fc95bf5529efa
Cr-Commit-Position: refs/heads/master@{#33572}
==========

[commit-bot: I haz the power, 2016-01-28 05:23:23]

Patchset 1 (id:??) landed as
https://crrev.com/f8ece9a01384d83737ba7f79999fc95bf5529efa
Cr-Commit-Position: refs/heads/master@{#33572}