[base] Optimise hashmaps with simple key equality

[base] Optimise hashmaps with simple key equality

Hashmaps with a simple key equality method (comparing pointers) don't
need to waste cycles (and branches) comparing hash values, as the key
comparison is cheap.

This patch modifies the hashmap's MatchFun to take the hashes as well as
the keys, thus allowing the MatchFun to ignore the hashes. This allows
slightly cleaner generated code, especially when the MatchFun is
inlined.

BUG=

Committed: https://crrev.com/306f83119b404eecaf28697e81fa8360a5237e5f
Cr-Commit-Position: refs/heads/master@{#39932}

[Leszek Swirski, 2016-09-30 11:35:24]

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

[commit-bot: I haz the power, 2016-09-30 11:35:27]

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, 2016-09-30 11:40:17]

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

[commit-bot: I haz the power, 2016-09-30 11:40:18]

Dry run: Try jobs failed on following builders:
  v8_linux_mipsel_compile_rel on master.tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux_mipsel_compile_rel...)

[Leszek Swirski, 2016-09-30 12:04:08]

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

[commit-bot: I haz the power, 2016-09-30 12:04:11]

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, 2016-09-30 12:09:00]

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

[commit-bot: I haz the power, 2016-09-30 12:09:01]

Dry run: Try jobs failed on following builders:
  v8_android_arm_compile_rel on master.tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_android_arm_compile_rel/...)
  v8_linux_arm_rel_ng on master.tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux_arm_rel_ng/builds/...)

[Leszek Swirski, 2016-09-30 13:50:03]

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

[commit-bot: I haz the power, 2016-09-30 13:50:09]

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, 2016-09-30 14:19:55]

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

[commit-bot: I haz the power, 2016-09-30 14:19:56]

Dry run: This issue passed the CQ dry run.

[Leszek Swirski, 2016-09-30 15:00:33]

leszeks@chromium.org changed reviewers:
+ rmcilroy@chromium.org

[Leszek Swirski, 2016-09-30 15:00:33]

Probably the last hashmap optimisation for now.

[rmcilroy, 2016-09-30 16:07:15]

Just nits, LGTM.

https://codereview.chromium.org/2381303002/diff/40001/src/base/hashmap.h
File src/base/hashmap.h (right):

https://codereview.chromium.org/2381303002/diff/40001/src/base/hashmap.h#newc...
src/base/hashmap.h:343: struct HashKeyComp {
Not sure on the name, how about HashEqualityThenKeyMatcher (bit of a mouthful
but I can't come up with anything better.

https://codereview.chromium.org/2381303002/diff/40001/src/base/hashmap.h#newc...
src/base/hashmap.h:357: struct KeyEqual {
nit - KeyEqualityMatcher (also move down to just about where it's first used in
PointerTemplateHashMapImpl)

[Leszek Swirski, 2016-10-03 14:33:28]

https://codereview.chromium.org/2381303002/diff/40001/src/base/hashmap.h
File src/base/hashmap.h (right):

https://codereview.chromium.org/2381303002/diff/40001/src/base/hashmap.h#newc...
src/base/hashmap.h:343: struct HashKeyComp {
On 2016/09/30 16:07:15, rmcilroy wrote:
> Not sure on the name, how about HashEqualityThenKeyMatcher (bit of a mouthful
> but I can't come up with anything better.

Neither could I, so done.

https://codereview.chromium.org/2381303002/diff/40001/src/base/hashmap.h#newc...
src/base/hashmap.h:357: struct KeyEqual {
On 2016/09/30 16:07:15, rmcilroy wrote:
> nit - KeyEqualityMatcher (also move down to just about where it's first used
in
> PointerTemplateHashMapImpl)

Done.

[Leszek Swirski, 2016-10-03 14:33:32]

The CQ bit was checked by leszeks@chromium.org

[Leszek Swirski, 2016-10-03 14:33:32]

The patchset sent to the CQ was uploaded after l-g-t-m from
rmcilroy@chromium.org
Link to the patchset: https://codereview.chromium.org/2381303002/#ps60001
(title: "Rename matcher structs to something more... verbose")

[commit-bot: I haz the power, 2016-10-03 14:33:36]

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, 2016-10-03 14:36:45]

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

[commit-bot: I haz the power, 2016-10-03 14:36:46]

Try jobs failed on following builders:
  v8_linux64_avx2_rel_ng on master.tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux64_avx2_rel_ng/buil...)
  v8_linux64_rel_ng on master.tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux64_rel_ng/builds/13842)
  v8_linux_nodcheck_rel_ng on master.tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_linux_nodcheck_rel_ng/bu...)

[Leszek Swirski, 2016-10-03 14:41:19]

The CQ bit was checked by leszeks@chromium.org

[Leszek Swirski, 2016-10-03 14:41:19]

The patchset sent to the CQ was uploaded after l-g-t-m from
rmcilroy@chromium.org
Link to the patchset: https://codereview.chromium.org/2381303002/#ps80001
(title: "Whoops, patches should compile")

[commit-bot: I haz the power, 2016-10-03 14:41:26]

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, 2016-10-03 15:07:19]

Committed patchset #5 (id:80001)

[commit-bot: I haz the power, 2016-10-03 15:07:45]

Description was changed from

==========
[base] Optimise hashmaps with simple key equality

Hashmaps with a simple key equality method (comparing pointers) don't
need to waste cycles (and branches) comparing hash values, as the key
comparison is cheap.

This patch modifies the hashmap's MatchFun to take the hashes as well as
the keys, thus allowing the MatchFun to ignore the hashes. This allows
slightly cleaner generated code, especially when the MatchFun is
inlined.

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

to

==========
[base] Optimise hashmaps with simple key equality

Hashmaps with a simple key equality method (comparing pointers) don't
need to waste cycles (and branches) comparing hash values, as the key
comparison is cheap.

This patch modifies the hashmap's MatchFun to take the hashes as well as
the keys, thus allowing the MatchFun to ignore the hashes. This allows
slightly cleaner generated code, especially when the MatchFun is
inlined.

BUG=

Committed: https://crrev.com/306f83119b404eecaf28697e81fa8360a5237e5f
Cr-Commit-Position: refs/heads/master@{#39932}
==========

[commit-bot: I haz the power, 2016-10-03 15:07:46]

Patchset 5 (id:??) landed as
https://crrev.com/306f83119b404eecaf28697e81fa8360a5237e5f
Cr-Commit-Position: refs/heads/master@{#39932}