[ValueTracking] refactor: extract method haveNoCommonBitsSet
Summary:
Extract method haveNoCommonBitsSet so that we don't have to duplicate this logic in
InstCombine and SeparateConstOffsetFromGEP.
This patch also makes SeparateConstOffsetFromGEP more precise by passing
DominatorTree to computeKnownBits.
Test Plan: value-tracking-domtree.ll that tests ValueTracking indeed leverages dominating conditions
Reviewers: broune, meheff, majnemer
Reviewed By: majnemer
Subscribers: jholewinski, llvm-commits
Differential Revision: http://reviews.llvm.org/D9734
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237407
91177308-0d34-0410-b5e6-
96231b3b80d8