Treat all kArchNop instuctions as NOPs in jump threading.

Treat all kArchNop instuctions as NOPs in jump threading.

BUG=

Committed: https://crrev.com/ede28d900caf2d63922fdc84bbb4bd05978a76a3
Cr-Commit-Position: refs/heads/master@{#38902}

[georgia.kouveli, 2016-08-25 09:33:06]

georgia.kouveli@arm.com changed reviewers:
+ bmeurer@chromium.org, epertoso@chromium.org

[georgia.kouveli, 2016-08-25 09:33:07]

This improves code generation for stubs and bytecode handlers (for example in
AddStub, SubtractStub, IncStub, DecStub), where we often get:

b.vs <overflow>
b <no_overflow>
<overflow>:
  ...
<no_overflow>:
 ...

which would be better as:

b.vc <no_overflow>
  ...
<no_overflow>:
 ...

This happens even more frequently for 32-bit targets (e.g. in
ChangeFloat64ToTagged).

Jump threading is run after register allocation so kArchNop instructions with
inputs/outputs do not seem to be useful anymore (no code is generated for them).

[Benedikt Meurer, 2016-08-25 11:15:12]

The CQ bit was checked by bmeurer@chromium.org

[Benedikt Meurer, 2016-08-25 11:15:13]

lgtm

[commit-bot: I haz the power, 2016-08-25 11:15:24]

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, 2016-08-25 11:48:52]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-08-25 11:49:19]

Description was changed from

==========
Treat all kArchNop instuctions as NOPs in jump threading.

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

to

==========
Treat all kArchNop instuctions as NOPs in jump threading.

BUG=

Committed: https://crrev.com/ede28d900caf2d63922fdc84bbb4bd05978a76a3
Cr-Commit-Position: refs/heads/master@{#38902}
==========

[commit-bot: I haz the power, 2016-08-25 11:49:20]

Patchset 1 (id:??) landed as
https://crrev.com/ede28d900caf2d63922fdc84bbb4bd05978a76a3
Cr-Commit-Position: refs/heads/master@{#38902}