The post-dominance property is not sufficient to guarantee that a restore point
inside a loop is safe.
E.g.,
while(1) {
Save
Restore
if (...)
break;
use/def CSRs
}
All the uses/defs of CSRs are dominated by Save and post-dominated
by Restore. However, the CSRs uses are still reachable after
Restore and before Save are executed.
This fixes PR25824
llvm-svn: 255613
