[Turbofan] Make the -0 deopt case more efficient in multiplication.

[Turbofan] Make the -0 deopt case more efficient in multiplication.

After multiplying two integers we emit code like:

  if (result == 0) {
    if (OR_OPERATION(rhs, lhs) < 0) {
      DEOPT;
    }
  }

This CL allows us to eliminate the OR and comparison if either rhs or
lhs is a negative number, reducing the code to:

  if (result == 0) DEOPT;

BUG=

Committed: https://crrev.com/0a36b5cd2c87a9827537bc91f0d0777efeb714fd
Cr-Commit-Position: refs/heads/master@{#38016}

[mvstanton, 2016-07-20 12:01:26]

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

[mvstanton, 2016-07-20 12:01:27]

Hi Benedikt,
Here is the strength reduction operation you described. Thanks for the look!
--Mike

[Benedikt Meurer, 2016-07-20 17:37:44]

Nice, thanks. LGTM once comments addressed.

https://codereview.chromium.org/2167643002/diff/1/src/compiler/machine-operat...
File src/compiler/machine-operator-reducer.cc (right):

https://codereview.chromium.org/2167643002/diff/1/src/compiler/machine-operat...
src/compiler/machine-operator-reducer.cc:268: // This targets the check for -0
after multiplication.
This is a detail that is not necessarily relevant. I'd prefer to have a single
comment like this instead:

// (x | K) < 0 => true or (K | x) < 0 => true iff K < 0

https://codereview.chromium.org/2167643002/diff/1/src/compiler/machine-operat...
src/compiler/machine-operator-reducer.cc:270: if
((mleftmatcher.left().HasValue() &&
Please add a IsNegative() helper to the Int32Matcher (similar to what we have
for Float64Matcher already) and use that here for left and right checks.

https://codereview.chromium.org/2167643002/diff/1/test/unittests/compiler/mac...
File test/unittests/compiler/machine-operator-reducer-unittest.cc (right):

https://codereview.chromium.org/2167643002/diff/1/test/unittests/compiler/mac...
test/unittests/compiler/machine-operator-reducer-unittest.cc:1511: // Node*
control = graph()->start();
Nit: Remove this line.

[mvstanton, 2016-07-25 07:54:12]

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

[mvstanton, 2016-07-25 07:54:18]

The CQ bit was checked by mvstanton@chromium.org

[mvstanton, 2016-07-25 07:54:18]

The patchset sent to the CQ was uploaded after l-g-t-m from bmeurer@chromium.org
Link to the patchset: https://codereview.chromium.org/2167643002/#ps20001
(title: "Code comments.")

[commit-bot: I haz the power, 2016-07-25 07:54:25]

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, 2016-07-25 07:57:52]

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

[commit-bot: I haz the power, 2016-07-25 07:57:53]

Try jobs failed on following builders:
  v8_presubmit on master.tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_presubmit/builds/20098)

[mvstanton, 2016-07-25 11:52:30]

The CQ bit was checked by mvstanton@chromium.org

[mvstanton, 2016-07-25 11:52:30]

The patchset sent to the CQ was uploaded after l-g-t-m from bmeurer@chromium.org
Link to the patchset: https://codereview.chromium.org/2167643002/#ps40001
(title: "Fix nit.")

[commit-bot: I haz the power, 2016-07-25 11:52:40]

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, 2016-07-25 12:13:21]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2016-07-25 12:15:29]

Description was changed from

==========
[Turbofan] Make the -0 deopt case more efficient in multiplication.

After multiplying two integers we emit code like:

  if (result == 0) {
    if (OR_OPERATION(rhs, lhs) < 0) {
      DEOPT;
    }
  }

This CL allows us to eliminate the OR and comparison if either rhs or
lhs is a negative number, reducing the code to:

  if (result == 0) DEOPT;


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

to

==========
[Turbofan] Make the -0 deopt case more efficient in multiplication.

After multiplying two integers we emit code like:

  if (result == 0) {
    if (OR_OPERATION(rhs, lhs) < 0) {
      DEOPT;
    }
  }

This CL allows us to eliminate the OR and comparison if either rhs or
lhs is a negative number, reducing the code to:

  if (result == 0) DEOPT;

BUG=

Committed: https://crrev.com/0a36b5cd2c87a9827537bc91f0d0777efeb714fd
Cr-Commit-Position: refs/heads/master@{#38016}
==========

[commit-bot: I haz the power, 2016-07-25 12:15:30]

Patchset 3 (id:??) landed as
https://crrev.com/0a36b5cd2c87a9827537bc91f0d0777efeb714fd
Cr-Commit-Position: refs/heads/master@{#38016}