Eliminate special keyed load string stub in favor of uniform handlers.

Eliminate special keyed load string stub in favor of uniform handlers.

KeyedLoadIC installs a special case if the receiver is a string.
Although there are several maps for strings, in practice we seem to
be able to treat them individually because a given KeyedLoad site
only sees 1-2 string types.

R=yangguo@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=24661

[mvstanton, 2014-09-26 12:46:12]

mvstanton@chromium.org changed reviewers:
+ yangguo@chromium.org

[mvstanton, 2014-09-26 12:46:12]

Hi Yang here is the string handler cl.

* Some assembly code just had to move into a stub
* The StringCharAtGenerator needed another option (it can eliminate instance
type check in the handler)
* Some deft changes in the MISS handler
* Had to adjust how the feedback is gathered for crankshaft.

Thanks for the look!
--Michael

[Yang, 2014-09-30 13:32:34]

On 2014/09/26 12:46:12, mvstanton wrote:
> Hi Yang here is the string handler cl.
> 
> * Some assembly code just had to move into a stub
> * The StringCharAtGenerator needed another option (it can eliminate instance
> type check in the handler)
> * Some deft changes in the MISS handler
> * Had to adjust how the feedback is gathered for crankshaft.
> 
> Thanks for the look!
> --Michael

looking good. now on to platform ports!

[mvstanton, 2014-10-01 13:22:48]

Thanks Yang, here are the ports, all the best,
--Michael

[Yang, 2014-10-08 13:43:50]

On 2014/10/01 13:22:48, mvstanton wrote:
> Thanks Yang, here are the ports, all the best,
> --Michael

LGTM.

[mvstanton, 2014-10-16 11:43:09]

Committed patchset #2 (id:20001) manually as 24661 (presubmit successful).