RFR: JDK-8231447: Shenandoah: Compilation-time regression after JDK-8231086

[Roman Kennke]

With JDK-8231086, compilation time of fastdebug build regressed from 
~3:30m to ~5:00m here. See also:

https://mail.openjdk.java.net/pipermail/shenandoah-dev/2019-September/010622.html

The problem appears to be the presence of clone-barrier code in 
shenandoahBarrierSet.inline.hpp which is then subsequently processed by 
anything that includes that file (incl.  and in particular the Access API).

I propose to fix it by breaking out the clone_barrier() code into its 
own file, and only include that where we need it shenandoahRuntime.cpp, 
and let the access-API clone() call a non-inlined entry point that 
resides in shenandoahBarrierSet.cpp. This brings compile-time back to 
what it was before.

http://cr.openjdk.java.net/~rkennke/JDK-8231447/webrev.00/

Testing: hotspot_gc_shenandoah

Ok?

Roman