PPC: [runtime] Use "the hole" instead of smi 0 as sentinel for context extension.

PPC: [runtime] Use "the hole" instead of smi 0 as sentinel for context extension.

Port 9e6448813d41858c3f879ecde41b13bda0770673

Original commit message:
    This way we avoid the %_IsSmi magic that is required in TurboFan to
    (efficiently) check abitrary context slots for smi 0. Checking against
    "the hole" is common in the AstGraphBuilder and "the hole" is also used
    to mark other context slots as not initialized.

R=bmeurer@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=

Committed: https://crrev.com/45e29ac25ea1fa6e562ef7707e461b00456fa10b
Cr-Commit-Position: refs/heads/master@{#32438}

[michael_dawson, 2015-11-30 21:34:11]

On 2015/11/30 21:06:21, mtbrandyberry wrote:

lgtm

[john.yan, 2015-11-30 22:53:06]

lgtm

[MTBrandyberry, 2015-12-01 04:17:33]

The CQ bit was checked by mbrandy@us.ibm.com

[commit-bot: I haz the power, 2015-12-01 04:17:44]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1491453002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1491453002/1

[commit-bot: I haz the power, 2015-12-01 04:35:59]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-12-01 04:37:00]

Description was changed from

==========
PPC: [runtime] Use "the hole" instead of smi 0 as sentinel for context
extension.

Port 9e6448813d41858c3f879ecde41b13bda0770673

Original commit message:
    This way we avoid the %_IsSmi magic that is required in TurboFan to
    (efficiently) check abitrary context slots for smi 0. Checking against
    "the hole" is common in the AstGraphBuilder and "the hole" is also used
    to mark other context slots as not initialized.

R=bmeurer@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com,
michael_dawson@ca.ibm.com
BUG=
==========

to

==========
PPC: [runtime] Use "the hole" instead of smi 0 as sentinel for context
extension.

Port 9e6448813d41858c3f879ecde41b13bda0770673

Original commit message:
    This way we avoid the %_IsSmi magic that is required in TurboFan to
    (efficiently) check abitrary context slots for smi 0. Checking against
    "the hole" is common in the AstGraphBuilder and "the hole" is also used
    to mark other context slots as not initialized.

R=bmeurer@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com,
michael_dawson@ca.ibm.com
BUG=

Committed: https://crrev.com/45e29ac25ea1fa6e562ef7707e461b00456fa10b
Cr-Commit-Position: refs/heads/master@{#32438}
==========

[commit-bot: I haz the power, 2015-12-01 04:37:01]

Patchset 1 (id:??) landed as
https://crrev.com/45e29ac25ea1fa6e562ef7707e461b00456fa10b
Cr-Commit-Position: refs/heads/master@{#32438}