Exploit sharing when comparing and copying groups in ComputedStyle.

Exploit sharing when comparing and copying groups in ComputedStyle.

Groups inside ComputedStyle, such as StyleSurroundData, are stored as
pointers. When we copy the StyleSurroundData of a ComputedStyle, instead
of copying each member inside StyleSurroundData, we can copy the pointer
itself and do a copy when we write to it (copy-on-write). Similarly,
when we compare two StyleSurroundData pointers, we can first check if
they're pointing to the same object. If so, then we know that the two
StyleSurroundDatas are equal without having to compare each member
inside StyleSurroundData.

This patch introduces two macros: fieldwise_compare and fieldwise_copy,
which generate the code to do this optimisation. These macros take a
a list of fields to compare/copy and generate the cheapest set of code
for that task, taking advantage of group sharing.

This patch removes the perf cost of:
https://codereview.chromium.org/2786883002

by generating the exact same code as what was originally handwritten.

Diff of generated code:
https://gist.github.com/darrnshn/fe97404e680016753030fc788fcf24ff/revisions

BUG=628043
Review-Url: https://codereview.chromium.org/2826633002
Cr-Commit-Position: refs/heads/master@{#467243}
Committed: https://chromium.googlesource.com/chromium/src/+/51ad943c5fac355ab0166e1f47a104e8bc0b3bc6

[shend, 2017-04-19 02:56:27]

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

[commit-bot: I haz the power, 2017-04-19 02:56:53]

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

[shend, 2017-04-19 03:06:19]

Description was changed from

==========
Add fast path

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

to

==========
Exploit sharing when comparing and copying groups in ComputedStyle.

Groups inside ComputedStyle, such as StyleSurroundData, are stored as
pointers. When we copy the StyleSurroundData of a ComputedStyle, instead
of copying each member inside StyleSurroundData, we can copy the pointer
itself and do a copy when we write to it (copy-on-write). Similarly,
when we compare two StyleSurroundData pointers, we can first check if
they're pointing to the same object. If so, then we know that the two
StyleSurroundDatas are equal without having to compare each member
inside StyleSurroundData.

This patch introduces two macros: fieldwise_compare and fieldwise_copy,
which generate the code to do this optimisation. These macros take a
a list of fields to compare/copy and generate the cheapest set of code
for that task, taking advantage of group sharing.

This patch removes the perf cost of:
https://codereview.chromium.org/2786883002

by generating the exact same code as what was originally handwritten.

BUG=628043
==========

[shend, 2017-04-19 03:07:38]

Description was changed from

==========
Exploit sharing when comparing and copying groups in ComputedStyle.

Groups inside ComputedStyle, such as StyleSurroundData, are stored as
pointers. When we copy the StyleSurroundData of a ComputedStyle, instead
of copying each member inside StyleSurroundData, we can copy the pointer
itself and do a copy when we write to it (copy-on-write). Similarly,
when we compare two StyleSurroundData pointers, we can first check if
they're pointing to the same object. If so, then we know that the two
StyleSurroundDatas are equal without having to compare each member
inside StyleSurroundData.

This patch introduces two macros: fieldwise_compare and fieldwise_copy,
which generate the code to do this optimisation. These macros take a
a list of fields to compare/copy and generate the cheapest set of code
for that task, taking advantage of group sharing.

This patch removes the perf cost of:
https://codereview.chromium.org/2786883002

by generating the exact same code as what was originally handwritten.

BUG=628043
==========

to

==========
Exploit sharing when comparing and copying groups in ComputedStyle.

Groups inside ComputedStyle, such as StyleSurroundData, are stored as
pointers. When we copy the StyleSurroundData of a ComputedStyle, instead
of copying each member inside StyleSurroundData, we can copy the pointer
itself and do a copy when we write to it (copy-on-write). Similarly,
when we compare two StyleSurroundData pointers, we can first check if
they're pointing to the same object. If so, then we know that the two
StyleSurroundDatas are equal without having to compare each member
inside StyleSurroundData.

This patch introduces two macros: fieldwise_compare and fieldwise_copy,
which generate the code to do this optimisation. These macros take a
a list of fields to compare/copy and generate the cheapest set of code
for that task, taking advantage of group sharing.

This patch removes the perf cost of:
https://codereview.chromium.org/2786883002

by generating the exact same code as what was originally handwritten.

Diff of generated code:
https://gist.github.com/darrnshn/4361186d78f859296bd109a71b182774/revisions

BUG=628043
==========

[shend, 2017-04-19 03:12:53]

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

[commit-bot: I haz the power, 2017-04-19 03:13:06]

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

[shend, 2017-04-19 04:16:40]

shend@chromium.org changed reviewers:
+ nainar@chromium.org

[shend, 2017-04-19 04:16:41]

Hi Naina, PTAL. The macro is a bit complicated, lemme know what I can do to make
this easier to understand :)

[nainar, 2017-04-19 04:46:39]

lgtm with the nit

https://codereview.chromium.org/2826633002/diff/80001/third_party/WebKit/Sour...
File third_party/WebKit/Source/build/scripts/templates/fields/field.tmpl
(right):

https://codereview.chromium.org/2826633002/diff/80001/third_party/WebKit/Sour...
third_party/WebKit/Source/build/scripts/templates/fields/field.tmpl:78:
{{getter_expression(field)}} = other.{{getter_expression(field)}};
setter_expression(field)

[shend, 2017-04-20 00:17:33]

https://codereview.chromium.org/2826633002/diff/80001/third_party/WebKit/Sour...
File third_party/WebKit/Source/build/scripts/templates/fields/field.tmpl
(right):

https://codereview.chromium.org/2826633002/diff/80001/third_party/WebKit/Sour...
third_party/WebKit/Source/build/scripts/templates/fields/field.tmpl:78:
{{getter_expression(field)}} = other.{{getter_expression(field)}};
On 2017/04/19 at 04:46:39, nainar wrote:
> setter_expression(field)

Done.

[shend, 2017-04-20 03:39:00]

shend@chromium.org changed reviewers:
+ meade@chromium.org

[shend, 2017-04-20 03:39:00]

Hi Eddy, this is a patch that I'll land together with groups. The macro is a bit
complicated, lemme know if I can make it easier to understand.

[shend, 2017-04-20 04:26:41]

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

[commit-bot: I haz the power, 2017-04-20 04:27:18]

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, 2017-04-20 06:15:40]

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

[commit-bot: I haz the power, 2017-04-20 06:15:41]

Dry run: This issue passed the CQ dry run.

[shend, 2017-04-24 02:02:48]

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

[commit-bot: I haz the power, 2017-04-24 02:02:53]

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, 2017-04-24 02:14:23]

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

[commit-bot: I haz the power, 2017-04-24 02:14:24]

Dry run: Try jobs failed on following builders:
  linux_chromium_chromeos_ozone_rel_ng on master.tryserver.chromium.linux
(JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[shend, 2017-04-24 03:43:34]

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

[commit-bot: I haz the power, 2017-04-24 03:43:50]

Dry run: CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[shend, 2017-04-24 03:44:57]

The CQ bit was unchecked by shend@chromium.org

[shend, 2017-04-24 03:59:22]

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

[commit-bot: I haz the power, 2017-04-24 03:59:36]

Dry run: CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[shend, 2017-04-24 04:00:07]

Description was changed from

==========
Exploit sharing when comparing and copying groups in ComputedStyle.

Groups inside ComputedStyle, such as StyleSurroundData, are stored as
pointers. When we copy the StyleSurroundData of a ComputedStyle, instead
of copying each member inside StyleSurroundData, we can copy the pointer
itself and do a copy when we write to it (copy-on-write). Similarly,
when we compare two StyleSurroundData pointers, we can first check if
they're pointing to the same object. If so, then we know that the two
StyleSurroundDatas are equal without having to compare each member
inside StyleSurroundData.

This patch introduces two macros: fieldwise_compare and fieldwise_copy,
which generate the code to do this optimisation. These macros take a
a list of fields to compare/copy and generate the cheapest set of code
for that task, taking advantage of group sharing.

This patch removes the perf cost of:
https://codereview.chromium.org/2786883002

by generating the exact same code as what was originally handwritten.

Diff of generated code:
https://gist.github.com/darrnshn/4361186d78f859296bd109a71b182774/revisions

BUG=628043
==========

to

==========
Exploit sharing when comparing and copying groups in ComputedStyle.

Groups inside ComputedStyle, such as StyleSurroundData, are stored as
pointers. When we copy the StyleSurroundData of a ComputedStyle, instead
of copying each member inside StyleSurroundData, we can copy the pointer
itself and do a copy when we write to it (copy-on-write). Similarly,
when we compare two StyleSurroundData pointers, we can first check if
they're pointing to the same object. If so, then we know that the two
StyleSurroundDatas are equal without having to compare each member
inside StyleSurroundData.

This patch introduces two macros: fieldwise_compare and fieldwise_copy,
which generate the code to do this optimisation. These macros take a
a list of fields to compare/copy and generate the cheapest set of code
for that task, taking advantage of group sharing.

This patch removes the perf cost of:
https://codereview.chromium.org/2786883002

by generating the exact same code as what was originally handwritten.

Diff of generated code:
https://gist.github.com/darrnshn/fe97404e680016753030fc788fcf24ff/revisions

BUG=628043
==========

[commit-bot: I haz the power, 2017-04-24 05:48:58]

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

[commit-bot: I haz the power, 2017-04-24 05:48:59]

Dry run: This issue passed the CQ dry run.

[meade_UTC10, 2017-04-24 07:10:21]

lgtm

[shend, 2017-04-25 23:58:07]

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

[commit-bot: I haz the power, 2017-04-25 23:59:13]

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, 2017-04-26 02:27:00]

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

[commit-bot: I haz the power, 2017-04-26 02:27:01]

Dry run: This issue passed the CQ dry run.

[shend, 2017-04-26 05:20:37]

The CQ bit was checked by shend@chromium.org

[shend, 2017-04-26 05:20:38]

The patchset sent to the CQ was uploaded after l-g-t-m from nainar@chromium.org
Link to the patchset: https://codereview.chromium.org/2826633002/#ps180001
(title: "Rebase")

[commit-bot: I haz the power, 2017-04-26 05:20:55]

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, 2017-04-26 05:26:27]

CQ is committing da patch.

Bot data: {"patchset_id": 180001, "attempt_start_ts": 1493184037911110,
"parent_rev": "56432d951bee9e8162561899c3ac2f0cd524d528", "commit_rev":
"51ad943c5fac355ab0166e1f47a104e8bc0b3bc6"}

[commit-bot: I haz the power, 2017-04-26 05:26:37]

Description was changed from

==========
Exploit sharing when comparing and copying groups in ComputedStyle.

Groups inside ComputedStyle, such as StyleSurroundData, are stored as
pointers. When we copy the StyleSurroundData of a ComputedStyle, instead
of copying each member inside StyleSurroundData, we can copy the pointer
itself and do a copy when we write to it (copy-on-write). Similarly,
when we compare two StyleSurroundData pointers, we can first check if
they're pointing to the same object. If so, then we know that the two
StyleSurroundDatas are equal without having to compare each member
inside StyleSurroundData.

This patch introduces two macros: fieldwise_compare and fieldwise_copy,
which generate the code to do this optimisation. These macros take a
a list of fields to compare/copy and generate the cheapest set of code
for that task, taking advantage of group sharing.

This patch removes the perf cost of:
https://codereview.chromium.org/2786883002

by generating the exact same code as what was originally handwritten.

Diff of generated code:
https://gist.github.com/darrnshn/fe97404e680016753030fc788fcf24ff/revisions

BUG=628043
==========

to

==========
Exploit sharing when comparing and copying groups in ComputedStyle.

Groups inside ComputedStyle, such as StyleSurroundData, are stored as
pointers. When we copy the StyleSurroundData of a ComputedStyle, instead
of copying each member inside StyleSurroundData, we can copy the pointer
itself and do a copy when we write to it (copy-on-write). Similarly,
when we compare two StyleSurroundData pointers, we can first check if
they're pointing to the same object. If so, then we know that the two
StyleSurroundDatas are equal without having to compare each member
inside StyleSurroundData.

This patch introduces two macros: fieldwise_compare and fieldwise_copy,
which generate the code to do this optimisation. These macros take a
a list of fields to compare/copy and generate the cheapest set of code
for that task, taking advantage of group sharing.

This patch removes the perf cost of:
https://codereview.chromium.org/2786883002

by generating the exact same code as what was originally handwritten.

Diff of generated code:
https://gist.github.com/darrnshn/fe97404e680016753030fc788fcf24ff/revisions

BUG=628043

Review-Url: https://codereview.chromium.org/2826633002
Cr-Commit-Position: refs/heads/master@{#467243}
Committed:
https://chromium.googlesource.com/chromium/src/+/51ad943c5fac355ab0166e1f47a1...
==========

[commit-bot: I haz the power, 2017-04-26 05:26:38]

Committed patchset #10 (id:180001) as
https://chromium.googlesource.com/chromium/src/+/51ad943c5fac355ab0166e1f47a1...