[turbofan] Introduce dedicated BitcastWordToTagged machine operator.

[turbofan] Introduce dedicated BitcastWordToTagged machine operator.

This operator doesn't generate any actual code, but teaches the register
allocator that a certain computed pointer value is tagged. This is
required to safely implement InnerAllocate (and we also use this for
Allocate to be sure that we don't suddenly leak a dangling pointer into
the heap somewhere).

R=epertoso@chromium.org
BUG=v8:4939
LOG=n

Committed: https://crrev.com/33c717fba4ea866939a1c02d58a7e2ed1d353f55
Cr-Commit-Position: refs/heads/master@{#35700}

[Benedikt Meurer, 2016-04-21 09:04:46]

Hey Enrico,

Quickfix for the allocate pointer map thing in CodeStubAssembler.
Please take a look.

Thanks,
Benedikt

[epertoso, 2016-04-21 09:13:26]

lgtm

[Benedikt Meurer, 2016-04-21 09:38:47]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2016-04-21 09:38:53]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1905813003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1905813003/1

[commit-bot: I haz the power, 2016-04-21 09:49:07]

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

[commit-bot: I haz the power, 2016-04-21 09:49:08]

Try jobs failed on following builders:
  v8_linux_chromium_gn_rel on tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux_chromium_gn_rel/bu...)

[Benedikt Meurer, 2016-04-21 10:43:52]

The CQ bit was checked by bmeurer@chromium.org

[Benedikt Meurer, 2016-04-21 10:43:52]

The patchset sent to the CQ was uploaded after l-g-t-m from
epertoso@chromium.org
Link to the patchset: https://codereview.chromium.org/1905813003/#ps20001
(title: "REBASE. Small fix.")

[commit-bot: I haz the power, 2016-04-21 10:43:59]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1905813003/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1905813003/20001

[commit-bot: I haz the power, 2016-04-21 11:26:28]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-04-22 19:14:37]

Description was changed from

==========
[turbofan] Introduce dedicated BitcastWordToTagged machine operator.

This operator doesn't generate any actual code, but teaches the register
allocator that a certain computed pointer value is tagged. This is
required to safely implement InnerAllocate (and we also use this for
Allocate to be sure that we don't suddenly leak a dangling pointer into
the heap somewhere).

R=epertoso@chromium.org
BUG=v8:4939
LOG=n
==========

to

==========
[turbofan] Introduce dedicated BitcastWordToTagged machine operator.

This operator doesn't generate any actual code, but teaches the register
allocator that a certain computed pointer value is tagged. This is
required to safely implement InnerAllocate (and we also use this for
Allocate to be sure that we don't suddenly leak a dangling pointer into
the heap somewhere).

R=epertoso@chromium.org
BUG=v8:4939
LOG=n

Committed: https://crrev.com/33c717fba4ea866939a1c02d58a7e2ed1d353f55
Cr-Commit-Position: refs/heads/master@{#35700}
==========

[commit-bot: I haz the power, 2016-04-22 19:14:38]

Patchset 2 (id:??) landed as
https://crrev.com/33c717fba4ea866939a1c02d58a7e2ed1d353f55
Cr-Commit-Position: refs/heads/master@{#35700}