[arm64] Avoid signed arithmetic in AddWithCarry.

[arm64] Avoid signed arithmetic in AddWithCarry.

This avoids implementation-defined signed overflow in the simulator's
AddWithCarry implementation. The implementation of AddWithCarry now uses
unsigned arithmetic exclusively.

Testing coverage is also significantly improved.

BUG=

Committed: https://crrev.com/6ae7f2b5d8df71a97bdcec6294bce060a4a7fb99
Cr-Commit-Position: refs/heads/master@{#37895}

[jbramley, 2016-07-19 13:03:20]

jacob.bramley@arm.com changed reviewers:
+ bmeurer@chromium.org, jarin@chromium.org, titzer@chromium.org

[titzer, 2016-07-19 13:41:20]

LGTM. Thanks!

[jbramley, 2016-07-20 08:50:19]

The CQ bit was checked by jacob.bramley@arm.com

[commit-bot: I haz the power, 2016-07-20 08:50:27]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-07-20 09:15:05]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-07-20 09:15:43]

Description was changed from

==========
[arm64] Avoid signed arithmetic in AddWithCarry.

This avoids implementation-defined signed overflow in the simulator's
AddWithCarry implementation. The implementation of AddWithCarry now uses
unsigned arithmetic exclusively.

Testing coverage is also significantly improved.

BUG=
==========

to

==========
[arm64] Avoid signed arithmetic in AddWithCarry.

This avoids implementation-defined signed overflow in the simulator's
AddWithCarry implementation. The implementation of AddWithCarry now uses
unsigned arithmetic exclusively.

Testing coverage is also significantly improved.

BUG=

Committed: https://crrev.com/6ae7f2b5d8df71a97bdcec6294bce060a4a7fb99
Cr-Commit-Position: refs/heads/master@{#37895}
==========

[commit-bot: I haz the power, 2016-07-20 09:15:44]

Patchset 1 (id:??) landed as
https://crrev.com/6ae7f2b5d8df71a97bdcec6294bce060a4a7fb99
Cr-Commit-Position: refs/heads/master@{#37895}