Introduce FeedbackNexus for vector-based ics.

Introduce FeedbackNexus for vector-based ics.

A FeedbackNexus is the combination of a feedback vector, a slot(s) in
the vector, along with methods to query and manipulate that information
in a type-correct way.

A CallIC will have a CallICNexus, a LoadIC a LoadICNexus, etc.,
reflecting the fact that different types of ICs configure their data
in unique ways.

This CL limits itself to introducing and using the nexus type only for
CallICs. A follow-up will use them for Load and KeyedLoadICs for the
case when the --vector-ics flag is turned on.

The notion of a Nexus is also embedded at the lowest level of the IC
class. This makes sense because more ICs should become vector-based
in the future.

R=ishell@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=24952

[mvstanton, 2014-10-28 15:52:57]

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

[mvstanton, 2014-10-28 15:54:21]

Hi Igor,
Here is 2nd try, thanks for the help! The only change is in
type-feedback-vector.h, the definition of class FeedbackNexus: I got rid of the
union. PTAL,
thanks,
--Michael

[Igor Sheludko, 2014-10-28 15:59:06]

lgtm

[mvstanton, 2014-10-28 16:05:21]

Committed patchset #1 (id:1) manually as 24952 (presubmit successful).