[turbofan][x64] Fix instruction selection for Word32Equal.

[turbofan][x64] Fix instruction selection for Word32Equal.

The InstructionSelector on x64 didn't properly implement
VisitWord32Equal via VisitWordCompareZero, and thus it didn't
properly combined useless Word32Equal comparisons with zero
(which we use to implement bit negation).

R=jarin@chromium.org
BUG=v8:5267
Review-Url: https://codereview.chromium.org/2662123004
Cr-Commit-Position: refs/heads/master@{#42841}
Committed: https://chromium.googlesource.com/v8/v8/+/ad9dfc09113f5bd23c49c4968abcc1678d17b1de

[Benedikt Meurer, 2017-01-31 19:20:55]

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

[commit-bot: I haz the power, 2017-01-31 19:21:06]

Dry run: 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, 2017-01-31 19:43:00]

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

[commit-bot: I haz the power, 2017-01-31 19:43:01]

Dry run: This issue passed the CQ dry run.

[Jarin, 2017-02-01 08:39:56]

lgtm, although this will break if we feed result of 64bit op (such as Word64And)
into Word32Equal. Perhaps we need some protection against this. I am pretty sure
this used to happen.

https://codereview.chromium.org/2662123004/diff/1/src/compiler/x64/instructio...
File src/compiler/x64/instruction-selector-x64.cc (left):

https://codereview.chromium.org/2662123004/diff/1/src/compiler/x64/instructio...
src/compiler/x64/instruction-selector-x64.cc:2075: return
VisitWord64Compare(selector, value, cont);
UNREACHABLE() ?

https://codereview.chromium.org/2662123004/diff/1/src/compiler/x64/instructio...
src/compiler/x64/instruction-selector-x64.cc:2079: return
VisitWordCompare(selector, value, kX64Test, cont);
UNREACHABLE() ?

[Benedikt Meurer, 2017-02-01 08:42:16]

The CQ bit was checked by bmeurer@chromium.org

[Benedikt Meurer, 2017-02-01 08:42:16]

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/2662123004/#ps20001
(title: "Address comment as per offline discussion.")

[commit-bot: I haz the power, 2017-02-01 08:42:23]

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, 2017-02-01 09:08:41]

CQ is committing da patch.

Bot data: {"patchset_id": 20001, "attempt_start_ts": 1485938536061510,
"parent_rev": "a7ba61fdb56240b0157254a4e56e698a0fcfa4a1", "commit_rev":
"ad9dfc09113f5bd23c49c4968abcc1678d17b1de"}

[commit-bot: I haz the power, 2017-02-01 09:08:45]

Description was changed from

==========
[turbofan][x64] Fix instruction selection for Word32Equal.

The InstructionSelector on x64 didn't properly implement
VisitWord32Equal via VisitWordCompareZero, and thus it didn't
properly combined useless Word32Equal comparisons with zero
(which we use to implement bit negation).

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

to

==========
[turbofan][x64] Fix instruction selection for Word32Equal.

The InstructionSelector on x64 didn't properly implement
VisitWord32Equal via VisitWordCompareZero, and thus it didn't
properly combined useless Word32Equal comparisons with zero
(which we use to implement bit negation).

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

Review-Url: https://codereview.chromium.org/2662123004
Cr-Commit-Position: refs/heads/master@{#42841}
Committed:
https://chromium.googlesource.com/v8/v8/+/ad9dfc09113f5bd23c49c4968abcc1678d1...
==========

[commit-bot: I haz the power, 2017-02-01 09:08:46]

Committed patchset #2 (id:20001) as
https://chromium.googlesource.com/v8/v8/+/ad9dfc09113f5bd23c49c4968abcc1678d1...