[crankshaft] DCE must not eliminate (observable) math operations.

[crankshaft] DCE must not eliminate (observable) math operations.

The HUnaryMathOperation cannot be eliminated in general, because the
spec requires a ToNumber conversion on the input, which is observable
of course.

BUG=v8:4389
LOG=y

Committed: https://crrev.com/fef38c21e8e119e3bbf5423fd6fc2c03fd1f6c39
Cr-Commit-Position: refs/heads/master@{#30343}

[Benedikt Meurer, 2015-08-25 06:00:48]

bmeurer@chromium.org changed reviewers:
+ hpayer@chromium.org

[Benedikt Meurer, 2015-08-25 06:00:48]

Hannes: PTAL
Andreas, Bill: FYI

[Hannes Payer (out of office), 2015-08-25 06:04:37]

rubber-stamped LGTM

[Hannes Payer (out of office), 2015-08-25 06:04:42]

The CQ bit was checked by hpayer@chromium.org

[commit-bot: I haz the power, 2015-08-25 06:04:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1307413003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1307413003/1

[commit-bot: I haz the power, 2015-08-25 06:24:45]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-08-25 06:25:05]

Patchset 1 (id:??) landed as
https://crrev.com/fef38c21e8e119e3bbf5423fd6fc2c03fd1f6c39
Cr-Commit-Position: refs/heads/master@{#30343}