8219807: C2 crash in IfNode::up_one_dom(Node*, bool)
Summary: Guard against regions degraded to copies.
Reviewed-by: kvn
/build/
/dist/
/.idea/
nbproject/private/
/webrev
/.src-rev
/.jib/
.DS_Store
.metadata/
.recommenders/
test/nashorn/script/external
test/nashorn/lib
NashornProfile.txt
**/JTreport/**
**/JTwork/**