[DAG] Integrate findBaseOffset address analyses to BaseIndexOffset. NFCI.

BaseIndexOffset supercedes findBaseOffset analysis save only Constant
Pool addresses. Migrate analysis to BaseIndexOffset.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@321364 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed