Adding ElementsAccessor::Slice

Adding ElementsAccessor::Slice

- Move fast paths from builtins.cc ArraySlice to ElementsAccessor
- Handle more argument types in the fast path

BUG=

Committed: https://crrev.com/f68dcc924b729405b6c12962d369220fad20bd51
Cr-Commit-Position: refs/heads/master@{#30471}

[Camillo Bruni, 2015-08-28 09:23:27]

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

[commit-bot: I haz the power, 2015-08-28 09:23:31]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1321773002/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1321773002/40001

[Camillo Bruni, 2015-08-28 09:24:41]

cbruni@chromium.org changed reviewers:
+ ishell@chromium.org

[commit-bot: I haz the power, 2015-08-28 09:33:49]

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

[commit-bot: I haz the power, 2015-08-28 09:33:50]

Dry run: Try jobs failed on following builders:
  v8_win64_rel on tryserver.v8 (JOB_FAILED,
http://build.chromium.org/p/tryserver.v8/builders/v8_win64_rel/builds/8105)

[Camillo Bruni, 2015-08-28 12:11:28]

PTAL

[Igor Sheludko, 2015-08-31 10:42:51]

https://codereview.chromium.org/1321773002/diff/60001/src/builtins.cc
File src/builtins.cc (left):

https://codereview.chromium.org/1321773002/diff/60001/src/builtins.cc#oldcode294
src/builtins.cc:294: 
Spurious change.

https://codereview.chromium.org/1321773002/diff/60001/src/builtins.cc
File src/builtins.cc (right):

https://codereview.chromium.org/1321773002/diff/60001/src/builtins.cc#newcode551
src/builtins.cc:551: if (!ClampedToInteger(args[1], &relative_start)) {
I think clamping could be wrong if we ever have a fast array larger than
kMaxInt. In this case slice(NaN) and slice(kMinInt-1) would produce wrong
results.
What about renaming it to something else and use the old logic for
IsHeapNumber() case.

[Camillo Bruni, 2015-08-31 11:10:08]

https://codereview.chromium.org/1321773002/diff/60001/src/builtins.cc
File src/builtins.cc (left):

https://codereview.chromium.org/1321773002/diff/60001/src/builtins.cc#oldcode294
src/builtins.cc:294: 
On 2015/08/31 at 10:42:51, Igor Sheludko wrote:
> Spurious change.

I moved everything in to an anonymous namespace, where static is no longer
needed (I was told ;)

https://codereview.chromium.org/1321773002/diff/60001/src/builtins.cc
File src/builtins.cc (right):

https://codereview.chromium.org/1321773002/diff/60001/src/builtins.cc#newcode551
src/builtins.cc:551: if (!ClampedToInteger(args[1], &relative_start)) {
On 2015/08/31 at 10:42:51, Igor Sheludko wrote:
> I think clamping could be wrong if we ever have a fast array larger than
kMaxInt. In this case slice(NaN) and slice(kMinInt-1) would produce wrong
results.
> What about renaming it to something else and use the old logic for
IsHeapNumber() case.

I agree that the name ClampedToInteger is not a good name... will certainly
change it.
1. slice(NaN) will produce the correct result as NaN is mapped to 0 (according
to spec)
2. MinInt-1 would be represented as a double which is out of int range, hence
ClampedToInteger would map it to kMinInt. Given that the length of a FastArray
is a signed Smi we have enough room to do proper range checks. Since:
relative_start = kMinInt - 1 = kMinInt. len is in [0, Smi::kMaxValue].

[Camillo Bruni, 2015-08-31 11:36:32]

Addressed comments.

[Igor Sheludko, 2015-08-31 11:41:09]

lgtm

[Camillo Bruni, 2015-08-31 11:41:40]

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

[commit-bot: I haz the power, 2015-08-31 11:41:51]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1321773002/80001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1321773002/80001

[commit-bot: I haz the power, 2015-08-31 12:17:33]

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

[commit-bot: I haz the power, 2015-08-31 12:17:34]

Dry run: This issue passed the CQ dry run.

[Camillo Bruni, 2015-08-31 12:17:54]

The CQ bit was checked by cbruni@chromium.org

[commit-bot: I haz the power, 2015-08-31 12:18:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1321773002/80001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1321773002/80001

[commit-bot: I haz the power, 2015-08-31 12:19:21]

Committed patchset #5 (id:80001)

[commit-bot: I haz the power, 2015-08-31 12:19:33]

Patchset 5 (id:??) landed as
https://crrev.com/f68dcc924b729405b6c12962d369220fad20bd51
Cr-Commit-Position: refs/heads/master@{#30471}