[turbofan] Use cmn on ARM64 for negated rhs cmp

[turbofan] Use cmn on ARM64 for negated rhs cmp

Use compare-negate instruction if the right-hand input to a compare is a
negate operation.

BUG=

Committed: https://crrev.com/eb991c66e545a2c1c322450ffc674f6ced3bc375
Cr-Commit-Position: refs/heads/master@{#31866}

[martyn.capewell, 2015-11-06 18:25:33]

martyn.capewell@arm.com changed reviewers:
+ bmeurer@chromium.org, danno@chromium.org, jarin@chromium.org

[martyn.capewell, 2015-11-06 18:25:33]

I'm not entirely happy with the way in which I duplicate the input to the negate
in the instruction selector, but I can't see a better way to do it at this
point.

The CanCover() is needed in TryMatchAnyShift() to avoided duplicating shift
operands unnecessarily, so I need to remove the shift as an input to the negate.

[Benedikt Meurer, 2015-11-07 07:02:06]

The CQ bit was checked by bmeurer@chromium.org

[Benedikt Meurer, 2015-11-07 07:02:06]

lgtm

[commit-bot: I haz the power, 2015-11-07 07:02:09]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1410123009/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1410123009/1

[commit-bot: I haz the power, 2015-11-07 07:20:06]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-07 07:20:33]

Patchset 1 (id:??) landed as
https://crrev.com/eb991c66e545a2c1c322450ffc674f6ced3bc375
Cr-Commit-Position: refs/heads/master@{#31866}