[SSADestroyHoisting] Note barrier access scopes.
[SSADestroyHoisting] Note barrier access scopes.

Added a second backward reachability data flow that determines whether
any open access scopes contain barriers.  The end_access instructions
for those access scopes are themselves barriers.

benlangmuir/swift,JGiola/swift,glessard/swift,rudkx/swift,rudkx/swift,apple/swift,rudkx/swift,gregomni/swift,roambotics/swift,roambotics/swift,roambotics/swift,ahoppen/swift,roambotics/swift,benlangmuir/swift,roambotics/swift,apple/swift,glessard/swift,JGiola/swift,rudkx/swift,ahoppen/swift,apple/swift,gregomni/swift,apple/swift,gregomni/swift,benlangmuir/swift,atrick/swift,glessard/swift,benlangmuir/swift,ahoppen/swift,JGiola/swift,ahoppen/swift,benlangmuir/swift,atrick/swift,ahoppen/swift,rudkx/swift,glessard/swift,glessard/swift,gregomni/swift,gregomni/swift,roambotics/swift,JGiola/swift,glessard/swift,JGiola/swift,atrick/swift,atrick/swift,atrick/swift,ahoppen/swift,rudkx/swift,JGiola/swift,gregomni/swift,apple/swift,atrick/swift,benlangmuir/swift,apple/swift