Make smi.toString() do its work faster using native string helpers.

Make smi.toString() do its work faster using native string helpers.

BUG= http://dartbug.com/13450
R=fschneider@google.com

Committed: https://code.google.com/p/dart/source/detail?r=27808

[Lasse Reichstein Nielsen, 2013-09-23 11:25:18]

https://codereview.chromium.org/24359002/diff/1/runtime/lib/integers.cc
File runtime/lib/integers.cc (right):

https://codereview.chromium.org/24359002/diff/1/runtime/lib/integers.cc#newco...
runtime/lib/integers.cc:352: // Maximal number of digits of a 63 bit number is
19. Add one for minus sign.
I decided against using OS::SNPrint(characters, 0, "%ld", signed_value) because
I assume it will have some kind of overhead in parsing the format.
We should try that too, and see what's faster.

And I should make some timings of this change as well.

[kasperl, 2013-09-23 13:13:30]

As we talked about offline, I'd suggest using a statically allocated buffer of
some sort to build the digits and then use _OneByteString._allocate and
_OneByteString._setAt to build the string in pure Dart code.

[Lasse Reichstein Nielsen, 2013-09-24 11:03:53]

PTAL

[Florian Schneider, 2013-09-24 11:12:34]

Lgtm.

The issue description is not accurate anymore since you're using Dart instead of
C++ now.

[Lasse Reichstein Nielsen, 2013-09-24 11:20:03]

Good point, description changed.

[Lasse Reichstein Nielsen, 2013-09-24 11:21:22]

Committed patchset #3 manually as r27808 (presubmit successful).

[kasperl, 2013-09-24 11:22:09]

https://codereview.chromium.org/24359002/diff/10001/runtime/lib/integers.dart
File runtime/lib/integers.dart (right):

https://codereview.chromium.org/24359002/diff/10001/runtime/lib/integers.dart...
runtime/lib/integers.dart:241: if (this < 0) {
Use val < 0?

[Lasse Reichstein Nielsen, 2013-09-24 19:48:48]

https://codereview.chromium.org/24359002/diff/10001/runtime/lib/integers.dart
File runtime/lib/integers.dart (right):

https://codereview.chromium.org/24359002/diff/10001/runtime/lib/integers.dart...
runtime/lib/integers.dart:241: if (this < 0) {
good point.