RFR: 8076467: AARCH64: assertion fail with -XX:+UseG1GC

[Andrew Haley]

UseG1GC doesn't work on AArch64 debug builds because of an assertion
failure.

Register::bit(bool) returns a bit for ORing into a bitmask which
represents a set of registers.  The bool passed to bit() may be true
or false; if it is false the passed register may be noreg, in which
case we should not call Register::encoding().

http://cr.openjdk.java.net/~aph/8076467/

Andrew.