S390: Fix Register conflict in CEntryStub

S390: Fix Register conflict in CEntryStub

when needs_return_buffer == true and result_size() > 2, the 3rd return value
is placed in r4 register. But when debug code is emited, it uses r4 register
for checking exceptions, which corrupts the 3rd return value.

R=joransiu@ca.ibm.com, mbrandy@us.ibm.com, michael_dawson@ca.ibm.com
BUG=

Committed: https://crrev.com/d65c8cbf2d90798303f1293e0d6d4eab8ea2cfee
Cr-Commit-Position: refs/heads/master@{#35084}

[john.yan, 2016-03-28 16:54:40]

The CQ bit was checked by jyan@ca.ibm.com to run a CQ dry run

[commit-bot: I haz the power, 2016-03-28 16:54:49]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1839663002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1839663002/1

[john.yan, 2016-03-28 16:54:50]

PTAL

[commit-bot: I haz the power, 2016-03-28 17:18:00]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-03-28 17:18:01]

Dry run: This issue passed the CQ dry run.

[JoranSiu, 2016-03-28 17:27:19]

On 2016/03/28 17:18:01, commit-bot: I haz the power wrote:
> Dry run: This issue passed the CQ dry run.

lgtm

[john.yan, 2016-03-28 17:31:39]

The CQ bit was checked by jyan@ca.ibm.com

[commit-bot: I haz the power, 2016-03-28 17:31:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1839663002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1839663002/1

[commit-bot: I haz the power, 2016-03-28 17:35:33]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-03-28 17:37:36]

Description was changed from

==========
S390: Fix Register conflict in CEntryStub

when needs_return_buffer == true and result_size() > 2, the 3rd return value
is placed in r4 register. But when debug code is emited, it uses r4 register
for checking exceptions, which corrupts the 3rd return value.

R=joransiu@ca.ibm.com, mbrandy@us.ibm.com, michael_dawson@ca.ibm.com
BUG=
==========

to

==========
S390: Fix Register conflict in CEntryStub

when needs_return_buffer == true and result_size() > 2, the 3rd return value
is placed in r4 register. But when debug code is emited, it uses r4 register
for checking exceptions, which corrupts the 3rd return value.

R=joransiu@ca.ibm.com, mbrandy@us.ibm.com, michael_dawson@ca.ibm.com
BUG=

Committed: https://crrev.com/d65c8cbf2d90798303f1293e0d6d4eab8ea2cfee
Cr-Commit-Position: refs/heads/master@{#35084}
==========

[commit-bot: I haz the power, 2016-03-28 17:37:37]

Patchset 1 (id:??) landed as
https://crrev.com/d65c8cbf2d90798303f1293e0d6d4eab8ea2cfee
Cr-Commit-Position: refs/heads/master@{#35084}