We have not synced up sh/jdk for a while now. Let's pick up to the latest upstream tag, jdk-13+17.
Merge is trivial, because sh/jdk has no diffs against jdk/jdk, except tags.
Changesets:
http://cr.openjdk.java.net/~shade/shenandoah/merges/jdk-13%2b19/changesets.txt
Testing: tier1_gc_shenandoah {fastdebug, release}
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Thanks,
-Aleksey