[turbofan] fix validator in face of phi optimizations.

[turbofan] fix validator in face of phi optimizations.

This fixes an issue encountered in wasm payloads, where we do not
(yet) optimize away duplicate phi definitions - phis in the same block
with the same operand list; and when move optimizations merge phi-
defining moves into the block defining the phi. If all this happens, the
register allocation validator back-propagation fails because it can't
distinguish the duplicate phis, when traversing backwards.

BUG=

Committed: https://crrev.com/5ae02268bec405347312b2d912cb6fa5e179704b
Cr-Commit-Position: refs/heads/master@{#34207}

[Mircea Trofin, 2016-02-22 18:06:28]

Description was changed from

==========
[turbofan] fix validator in face of phi optimizations.

BUG=
==========

to

==========
[turbofan] fix validator in face of phi optimizations.

This fixes an issue encountered in wasm payloads, where we do not
(yet) optimize away duplicate phi definitions - phis in the same block
with the same operand list; and when move optimizations merge phi-
defining moves into the block defining the phi. If all this happens, the
register allocation validator back-propagation fails because it can't
distinguish the duplicate phis, when traversing backwards.

BUG=
==========

[Mircea Trofin, 2016-02-22 18:06:28]

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

[Benedikt Meurer, 2016-02-23 05:30:17]

lgtm

[Mircea Trofin, 2016-02-23 07:51:10]

The CQ bit was checked by mtrofin@chromium.org

[commit-bot: I haz the power, 2016-02-23 07:51:22]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1720003002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1720003002/1

[commit-bot: I haz the power, 2016-02-23 07:52:59]

Description was changed from

==========
[turbofan] fix validator in face of phi optimizations.

This fixes an issue encountered in wasm payloads, where we do not
(yet) optimize away duplicate phi definitions - phis in the same block
with the same operand list; and when move optimizations merge phi-
defining moves into the block defining the phi. If all this happens, the
register allocation validator back-propagation fails because it can't
distinguish the duplicate phis, when traversing backwards.

BUG=
==========

to

==========
[turbofan] fix validator in face of phi optimizations.

This fixes an issue encountered in wasm payloads, where we do not
(yet) optimize away duplicate phi definitions - phis in the same block
with the same operand list; and when move optimizations merge phi-
defining moves into the block defining the phi. If all this happens, the
register allocation validator back-propagation fails because it can't
distinguish the duplicate phis, when traversing backwards.

BUG=
==========

[commit-bot: I haz the power, 2016-02-23 07:53:00]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-02-23 07:53:54]

Description was changed from

==========
[turbofan] fix validator in face of phi optimizations.

This fixes an issue encountered in wasm payloads, where we do not
(yet) optimize away duplicate phi definitions - phis in the same block
with the same operand list; and when move optimizations merge phi-
defining moves into the block defining the phi. If all this happens, the
register allocation validator back-propagation fails because it can't
distinguish the duplicate phis, when traversing backwards.

BUG=
==========

to

==========
[turbofan] fix validator in face of phi optimizations.

This fixes an issue encountered in wasm payloads, where we do not
(yet) optimize away duplicate phi definitions - phis in the same block
with the same operand list; and when move optimizations merge phi-
defining moves into the block defining the phi. If all this happens, the
register allocation validator back-propagation fails because it can't
distinguish the duplicate phis, when traversing backwards.

BUG=

Committed: https://crrev.com/5ae02268bec405347312b2d912cb6fa5e179704b
Cr-Commit-Position: refs/heads/master@{#34207}
==========

[commit-bot: I haz the power, 2016-02-23 07:53:55]

Patchset 1 (id:??) landed as
https://crrev.com/5ae02268bec405347312b2d912cb6fa5e179704b
Cr-Commit-Position: refs/heads/master@{#34207}