[turbofan] Only use Tagged machine representation for tagged state values.

[turbofan] Only use Tagged machine representation for tagged state values.

This avoids using kTaggedSigned and kTaggedPointer because the
semantic information of those type could be invalid in unreachable
code.

For example, SmiCheck(0.1) has representation TaggedSigned, but it is
later compiled to DeoptimizeUnless(ObjectIsSmi(0.1)) with the constant
0.1 directly connected to the uses. If the use is state-values, which
recorded the TaggedSigned representation of CheckSmi, the code
generator will be confused because it will see constant 0.1 that
claims to be TaggedSigned value.

BUG=chromium:675704
Review-Url: https://codereview.chromium.org/2656243004
Cr-Commit-Position: refs/heads/master@{#42756}
Committed: https://chromium.googlesource.com/v8/v8/+/6cd2d4ba41d7adc83f993620fe2e43ab8277e476

[Jarin, 2017-01-27 12:28:40]

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

[commit-bot: I haz the power, 2017-01-27 12:28:43]

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

[Jarin, 2017-01-27 12:29:11]

jarin@chromium.org changed reviewers:
+ bmeurer@chromium.org

[Jarin, 2017-01-27 12:29:12]

Could you take a look, please?

[Benedikt Meurer, 2017-01-27 12:30:24]

LGTM.

[commit-bot: I haz the power, 2017-01-27 13:01:20]

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

[Jarin, 2017-01-28 16:31:43]

The CQ bit was checked by jarin@chromium.org

[commit-bot: I haz the power, 2017-01-28 16:31:51]

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, 2017-01-28 16:36:54]

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

[commit-bot: I haz the power, 2017-01-28 16:36:55]

Try jobs failed on following builders:
  v8_linux_verify_csa_rel_ng on master.tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux_verify_csa_rel_ng/...)
  v8_linux_verify_csa_rel_ng_triggered on master.tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux_verify_csa_rel_ng_...)

[Jarin, 2017-01-28 17:05:26]

The CQ bit was checked by jarin@chromium.org

[commit-bot: I haz the power, 2017-01-28 17:05:29]

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, 2017-01-28 17:25:47]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1485623126332230, "parent_rev":
"e342ec90f05990b730b1f5b9699e74166330f1c8", "commit_rev":
"6cd2d4ba41d7adc83f993620fe2e43ab8277e476"}

[commit-bot: I haz the power, 2017-01-28 17:25:51]

Description was changed from

==========
[turbofan] Only use Tagged machine representation for tagged state values.

This avoids using kTaggedSigned and kTaggedPointer because the
semantic information of those type could be invalid in unreachable
code.

For example, SmiCheck(0.1) has representation TaggedSigned, but it is
later compiled to DeoptimizeUnless(ObjectIsSmi(0.1)) with the constant
0.1 directly connected to the uses. If the use is state-values, which
recorded the TaggedSigned representation of CheckSmi, the code
generator will be confused because it will see constant 0.1 that
claims to be TaggedSigned value.

BUG=chromium:675704
==========

to

==========
[turbofan] Only use Tagged machine representation for tagged state values.

This avoids using kTaggedSigned and kTaggedPointer because the
semantic information of those type could be invalid in unreachable
code.

For example, SmiCheck(0.1) has representation TaggedSigned, but it is
later compiled to DeoptimizeUnless(ObjectIsSmi(0.1)) with the constant
0.1 directly connected to the uses. If the use is state-values, which
recorded the TaggedSigned representation of CheckSmi, the code
generator will be confused because it will see constant 0.1 that
claims to be TaggedSigned value.

BUG=chromium:675704

Review-Url: https://codereview.chromium.org/2656243004
Cr-Commit-Position: refs/heads/master@{#42756}
Committed:
https://chromium.googlesource.com/v8/v8/+/6cd2d4ba41d7adc83f993620fe2e43ab827...
==========

[commit-bot: I haz the power, 2017-01-28 17:25:53]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/v8/v8/+/6cd2d4ba41d7adc83f993620fe2e43ab827...