RFR(S):8242429:Better implementation for signed extract

[Eric Liu]

Hi Tobias,

Thanks for your review, and sorry for the extreme delay. I took a holiday in the last couple of days:P



> Could you convert that test to a jtreg test and add it to the webrev?

> And maybe also add test cases for the "0-(A>>31)" into "(A>>>31)" optimization.

Add a jtreg test only,  no other files has been changed.



JBS: https://bugs.openjdk.java.net/browse/JDK-8242429
Webrev: http://cr.openjdk.java.net/~yzhang/ericliu/8242429/webrev.02/

Thanks,
Eric