RFR(S): 8035283 Second phase of branch shortening doesn't account for loop alignment

[Igor Veresov]

Branch shortening should take care of the case when a there is an “avoid-back-to-back” instruction in the loop header preceded by the block with another “avoid-back-to-back” instruction with the loop padding. The machinery did not account for the fact the padding can be completely eliminated during the emission.

Webrev: http://cr.openjdk.java.net/~iveresov/8035283/webrev.00/
JBS: https://bugs.openjdk.java.net/browse/JDK-8035283

Testing: the affected application, CTW, jtreg (on SPARC-T4 with loop alignment 4 and 16), jprt

Thanks!
igor