[RDF] Implement Liveness::getNearestAliasedRef(Reg, Inst)

This function will find the closest ref node aliased to Reg that is
in an instruction preceding Inst. This could be used to identify the
hypothetical reaching def of Reg, if Reg was a member of Inst.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297524 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed