Redundant dereferences in C2 shenandoah_wb?

[Aleksey Shipilev]

Hi,

I am studying the generated code for Shenandoah barriers. These two
dereferences seem excessive:
  http://cr.openjdk.java.net/~shade/shenandoah/wb.deref.1/webrev.00/

C1 and interpreter code for both x86_64 and AArch64 do not seem to do
the additional read barrier before testing evacuation_in_progress, doing
that only after. Am I missing something?

Thanks,
-Aleksey