Merge array allocation and List._copyFromObjectArray to provide fast path for large arrays.

Improve List.sublist and List.toList for large lists.

- Merge array allocation and List._copyFromObjectArray to provide memmove fast path;

- In optimizer given v2 = CreateArray(v0, v1) fold v2.length load to v1;

BUG=
R=iposva@google.com, srdjan@google.com

Committed: https://code.google.com/p/dart/source/detail?r=39831

[Vyacheslav Egorov (Google), 2014-09-03 17:54:06]

vegorov@google.com changed reviewers:
+ iposva@google.com, srdjan@google.com

[Vyacheslav Egorov (Google), 2014-09-03 17:54:19]

Please take a look.

[srdjan, 2014-09-03 18:08:11]

lgtm

https://codereview.chromium.org/536043002/diff/1/runtime/lib/array.cc
File runtime/lib/array.cc (right):

https://codereview.chromium.org/536043002/diff/1/runtime/lib/array.cc#newcode59
runtime/lib/array.cc:59: GET_NON_NULL_NATIVE_ARGUMENT(Bool, need_type_arg,
arguments->NativeArgAt(3));
optional: needs_type_arg

https://codereview.chromium.org/536043002/diff/1/runtime/lib/array.dart
File runtime/lib/array.dart (right):

https://codereview.chromium.org/536043002/diff/1/runtime/lib/array.dart#newco...
runtime/lib/array.dart:21: List _slice(int start, int count, bool
needTypeArgument) {
optional: needsTypeArgument.

https://codereview.chromium.org/536043002/diff/1/runtime/lib/array.dart#newco...
runtime/lib/array.dart:24: : new _List(count);
What is the performance degradation if we always allocate with type argument E?
Or is there a correctness issue?

https://codereview.chromium.org/536043002/diff/1/runtime/vm/bootstrap_natives.h
File runtime/vm/bootstrap_natives.h (right):

https://codereview.chromium.org/536043002/diff/1/runtime/vm/bootstrap_natives...
runtime/vm/bootstrap_natives.h:95: V(List_slice, 4)                             
                 \
Fix formatting

[Ivan Posva, 2014-09-03 19:10:00]

LGTM except that we seem to be missing tests verifying the type of empty
sublists.

-Ivan

https://codereview.chromium.org/536043002/diff/1/runtime/lib/array.cc
File runtime/lib/array.cc (right):

https://codereview.chromium.org/536043002/diff/1/runtime/lib/array.cc#newcode65
runtime/lib/array.cc:65: return Array::empty_array().raw();
What if you need to return an empty array of T?

https://codereview.chromium.org/536043002/diff/1/runtime/vm/object.cc
File runtime/vm/object.cc (right):

https://codereview.chromium.org/536043002/diff/1/runtime/vm/object.cc#newcode...
runtime/vm/object.cc:18103: Array& dest = Array::Handle(Array::New(count));
Please add a TODO to allocate new arrays, which will be set with memmove as
uninitialized.

[Vyacheslav Egorov (Google), 2014-09-03 20:35:17]

Thanks for the reviews! Landing.

https://codereview.chromium.org/536043002/diff/1/runtime/lib/array.cc
File runtime/lib/array.cc (right):

https://codereview.chromium.org/536043002/diff/1/runtime/lib/array.cc#newcode59
runtime/lib/array.cc:59: GET_NON_NULL_NATIVE_ARGUMENT(Bool, need_type_arg,
arguments->NativeArgAt(3));
On 2014/09/03 18:08:11, srdjan wrote:
> optional: needs_type_arg

Done.

https://codereview.chromium.org/536043002/diff/1/runtime/lib/array.cc#newcode65
runtime/lib/array.cc:65: return Array::empty_array().raw();
On 2014/09/03 19:10:00, Ivan Posva wrote:
> What if you need to return an empty array of T?

Good catch! This case fortunately is never hit because it is handled outside. 

I am going to merge this case into icount < 0.

https://codereview.chromium.org/536043002/diff/1/runtime/lib/array.dart
File runtime/lib/array.dart (right):

https://codereview.chromium.org/536043002/diff/1/runtime/lib/array.dart#newco...
runtime/lib/array.dart:21: List _slice(int start, int count, bool
needTypeArgument) {
On 2014/09/03 18:08:11, srdjan wrote:
> optional: needsTypeArgument.

Done.

https://codereview.chromium.org/536043002/diff/1/runtime/lib/array.dart#newco...
runtime/lib/array.dart:24: : new _List(count);
On 2014/09/03 18:08:11, srdjan wrote:
> What is the performance degradation if we always allocate with type argument
E?
> Or is there a correctness issue?

I have not measured performance impact. I doubt there is any in unchecked code.
I am just mimicking behavior of the old code in this decision.

https://codereview.chromium.org/536043002/diff/1/runtime/vm/bootstrap_natives.h
File runtime/vm/bootstrap_natives.h (right):

https://codereview.chromium.org/536043002/diff/1/runtime/vm/bootstrap_natives...
runtime/vm/bootstrap_natives.h:95: V(List_slice, 4)                             
                 \
On 2014/09/03 18:08:11, srdjan wrote:
> Fix formatting

Done.

https://codereview.chromium.org/536043002/diff/1/runtime/vm/object.cc
File runtime/vm/object.cc (right):

https://codereview.chromium.org/536043002/diff/1/runtime/vm/object.cc#newcode...
runtime/vm/object.cc:18103: Array& dest = Array::Handle(Array::New(count));
On 2014/09/03 19:10:00, Ivan Posva wrote:
> Please add a TODO to allocate new arrays, which will be set with memmove as
> uninitialized.

Done.

[Vyacheslav Egorov (Google), 2014-09-03 20:36:13]

Committed patchset #2 (id:20001) manually as 39831 (presubmit successful).