[turbofan] Improve representation selection for HeapObject checking.

[turbofan] Improve representation selection for HeapObject checking.

For lowering CheckHeapObject, always report TaggedPointer representation
and let the RepresentationChanger come up with a reasonable conversion from
whatever input representation to TaggedPointer. This way we no longer insert
the useless ChangeSomethingToTagged and then check the result for HeapObject,
i.e. mostly reduces the amount of useless code being generated.

Note there are now two operators ChangeFloat64ToTaggedPointer and the old
ChangeFloat64ToTagged, because their semantics different wrt. the strength
reduction in the SimplifiedOperatorReducer.

Also set the output MachineRepresentation::kTaggedPointer properly in
SimplifiedLowering whenever we know that we produce a HeapObject.

R=jarin@chromium.org
BUG=v8:5267
Committed: https://crrev.com/6322bf41613fd0df785ae4341e674fa9ee09c9d4
Cr-Commit-Position: refs/heads/master@{#40725}

[Benedikt Meurer, 2016-11-03 10:28:00]

The CQ bit was checked by bmeurer@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-11-03 10:28:02]

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

[Jarin, 2016-11-03 10:33:44]

lgtm

[Benedikt Meurer, 2016-11-03 10:36:25]

The CQ bit was unchecked by bmeurer@chromium.org

[Benedikt Meurer, 2016-11-03 10:36:31]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2016-11-03 10:36:35]

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, 2016-11-03 11:01:04]

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

[commit-bot: I haz the power, 2016-11-03 11:01:05]

Try jobs failed on following builders:
  v8_linux_dbg_ng on master.tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux_dbg_ng/builds/15603)
  v8_linux_dbg_ng_triggered on master.tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux_dbg_ng_triggered/b...)

[Benedikt Meurer, 2016-11-03 12:25:46]

The CQ bit was checked by bmeurer@chromium.org

[Benedikt Meurer, 2016-11-03 12:25:46]

The patchset sent to the CQ was uploaded after l-g-t-m from jarin@chromium.org
Link to the patchset: https://codereview.chromium.org/2476593002/#ps20001
(title: "REBASE and fix.")

[commit-bot: I haz the power, 2016-11-03 12:25:55]

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, 2016-11-03 12:52:21]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-11-17 22:20:35]

Description was changed from

==========
[turbofan] Improve representation selection for HeapObject checking.

For lowering CheckHeapObject, always report TaggedPointer representation
and let the RepresentationChanger come up with a reasonable conversion from
whatever input representation to TaggedPointer. This way we no longer insert
the useless ChangeSomethingToTagged and then check the result for HeapObject,
i.e. mostly reduces the amount of useless code being generated.

Note there are now two operators ChangeFloat64ToTaggedPointer and the old
ChangeFloat64ToTagged, because their semantics different wrt. the strength
reduction in the SimplifiedOperatorReducer.

Also set the output MachineRepresentation::kTaggedPointer properly in
SimplifiedLowering whenever we know that we produce a HeapObject.

R=jarin@chromium.org
BUG=v8:5267
==========

to

==========
[turbofan] Improve representation selection for HeapObject checking.

For lowering CheckHeapObject, always report TaggedPointer representation
and let the RepresentationChanger come up with a reasonable conversion from
whatever input representation to TaggedPointer. This way we no longer insert
the useless ChangeSomethingToTagged and then check the result for HeapObject,
i.e. mostly reduces the amount of useless code being generated.

Note there are now two operators ChangeFloat64ToTaggedPointer and the old
ChangeFloat64ToTagged, because their semantics different wrt. the strength
reduction in the SimplifiedOperatorReducer.

Also set the output MachineRepresentation::kTaggedPointer properly in
SimplifiedLowering whenever we know that we produce a HeapObject.

R=jarin@chromium.org
BUG=v8:5267

Committed: https://crrev.com/6322bf41613fd0df785ae4341e674fa9ee09c9d4
Cr-Commit-Position: refs/heads/master@{#40725}
==========

[commit-bot: I haz the power, 2016-11-17 22:20:38]

Patchset 2 (id:??) landed as
https://crrev.com/6322bf41613fd0df785ae4341e674fa9ee09c9d4
Cr-Commit-Position: refs/heads/master@{#40725}