RFR: fix for PhaseIdealLoop::clone_loop_predicates_fix_mem()

[Aleksey Shipilev]

On 10/22/2018 11:09 AM, Roland Westrelin wrote:
> http://cr.openjdk.java.net/~roland/shenandoah/clone_loop_predicates_fix_mem-fix/webrev.00/

Looks good to me. I think we need to protect the entry to
PhaseIdealLoop::clone_loop_predicates_fix_mem with UseShenandoahGC too, unless this is going away
from shared code. Like we did in sh/jdk11.

-Aleksey