Request for reviews (XS): 6880574

[Vladimir Kozlov]

http://cr.openjdk.java.net/~kvn/6880574/webrev.00

Fixed 6880574: C2 assert in escape.cpp:445 on linux-amd64

Problem:
Unsafe access may have several chained AddP nodes but
get_addp_base() method expects incorrectly only one.

Solution:
Look through chained AddP nodes in get_addp_base().

Reviewed by:

Fix verified (y/n): y, test

Other testing:
JPRT