PPC/s390: Reland [heap] Avoid the use of cells to point from code to new-space objects.

PPC/s390: Reland [heap] Avoid the use of cells to point from code to new-space objects.

Port 5e058540192eaf95e8d1c2c3d0920219491cde15

Original commit message:

    The reason for reverting is: This breaks gc-stress bot:
    https://chromegw.corp.google.com/i/client.v8/builders/V8%20Linux64%20GC%20Stress%20-%20custom%20snapshot

    Abortion of compaction could cause duplicate entries in the typed-old-to-new remembered set.
    These duplicates could cause a DCHECK to trigger which checks that slots recorded in the
    remembered set never point to to-space. This reland-CL allows duplicates in the remembered
    set by removing the DCHECK, and additionally clears entries in the remembered set if objects are moved.

    Original issue's description:

    Cells were needed originally because there was no typed remembered set to
    record direct pointers from code space to new space. A previous
    CL (https://codereview.chromium.org/2003553002/) already introduced
    the remembered set, this CL uses it.

    This CL
    * stores direct pointers in code objects, even if the target is in new space,
    * records the slot of the pointer in typed-old-to-new remembered set,
    * adds a list which stores weak code-to-new-space references,
    * adds a test to test-heap.cc for weak code-to-new-space references,
    * removes prints in tail-call-megatest.js

R=ahaas@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, mbrandy@us.ibm.com

BUG=
LOG=N

Committed: https://crrev.com/85cebe7389fe47f0efebf0cbb6e71526cc98f94c
Cr-Commit-Position: refs/heads/master@{#37346}

[JaideepBajwa, 2016-06-28 18:29:51]

PTAL

[john.yan, 2016-06-28 18:33:36]

lgtm

[JaideepBajwa, 2016-06-28 18:34:02]

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

[commit-bot: I haz the power, 2016-06-28 18:34:07]

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, 2016-06-28 18:56:55]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-06-28 18:59:12]

Description was changed from

==========
PPC/s390: Reland [heap] Avoid the use of cells to point from code to new-space
objects.

Port 5e058540192eaf95e8d1c2c3d0920219491cde15

Original commit message:

    The reason for reverting is: This breaks gc-stress bot:
   
https://chromegw.corp.google.com/i/client.v8/builders/V8%20Linux64%20GC%20Str...

    Abortion of compaction could cause duplicate entries in the typed-old-to-new
remembered set.
    These duplicates could cause a DCHECK to trigger which checks that slots
recorded in the
    remembered set never point to to-space. This reland-CL allows duplicates in
the remembered
    set by removing the DCHECK, and additionally clears entries in the
remembered set if objects are moved.

    Original issue's description:

    Cells were needed originally because there was no typed remembered set to
    record direct pointers from code space to new space. A previous
    CL (https://codereview.chromium.org/2003553002/) already introduced
    the remembered set, this CL uses it.

    This CL
    * stores direct pointers in code objects, even if the target is in new
space,
    * records the slot of the pointer in typed-old-to-new remembered set,
    * adds a list which stores weak code-to-new-space references,
    * adds a test to test-heap.cc for weak code-to-new-space references,
    * removes prints in tail-call-megatest.js

R=ahaas@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com,
michael_dawson@ca.ibm.com, mbrandy@us.ibm.com

BUG=
LOG=N
==========

to

==========
PPC/s390: Reland [heap] Avoid the use of cells to point from code to new-space
objects.

Port 5e058540192eaf95e8d1c2c3d0920219491cde15

Original commit message:

    The reason for reverting is: This breaks gc-stress bot:
   
https://chromegw.corp.google.com/i/client.v8/builders/V8%20Linux64%20GC%20Str...

    Abortion of compaction could cause duplicate entries in the typed-old-to-new
remembered set.
    These duplicates could cause a DCHECK to trigger which checks that slots
recorded in the
    remembered set never point to to-space. This reland-CL allows duplicates in
the remembered
    set by removing the DCHECK, and additionally clears entries in the
remembered set if objects are moved.

    Original issue's description:

    Cells were needed originally because there was no typed remembered set to
    record direct pointers from code space to new space. A previous
    CL (https://codereview.chromium.org/2003553002/) already introduced
    the remembered set, this CL uses it.

    This CL
    * stores direct pointers in code objects, even if the target is in new
space,
    * records the slot of the pointer in typed-old-to-new remembered set,
    * adds a list which stores weak code-to-new-space references,
    * adds a test to test-heap.cc for weak code-to-new-space references,
    * removes prints in tail-call-megatest.js

R=ahaas@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com,
michael_dawson@ca.ibm.com, mbrandy@us.ibm.com

BUG=
LOG=N

Committed: https://crrev.com/85cebe7389fe47f0efebf0cbb6e71526cc98f94c
Cr-Commit-Position: refs/heads/master@{#37346}
==========

[commit-bot: I haz the power, 2016-06-28 18:59:13]

Patchset 1 (id:??) landed as
https://crrev.com/85cebe7389fe47f0efebf0cbb6e71526cc98f94c
Cr-Commit-Position: refs/heads/master@{#37346}