RFR (XS) 8214426 [lworld][C1] aaload doesn't work with constant index

[Ioi Lam]

https://bugs.openjdk.java.net/browse/JDK-8214426
http://cr.openjdk.java.net/~iklam/valhalla/8214426-aaload-const-index-crash.v01/

The fix is to properly move the constant index into a register.

With this fix, all tests in TestBasicFunctionality passed for C1:

     $ jtreg $OPTIONS -Dtest.c1=true TestBasicFunctionality.java
     pass compiler/valhalla/valuetypes/TestBasicFunctionality.java
          Test results:   passed: 1

Thanks
- Ioi