[Attributor] Use the AANoNull attribute directly in AADereferenceable
Summary:
Instead of constantly keeping track of the nonnull status with the
dereferenceable information we can simply query the nonnull attribute
whenever we need the information (debug + manifest).
Reviewers: sstefan1, uenoku
Subscribers: hiraditya, bollu, jfb, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D66113
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@368924
91177308-0d34-0410-b5e6-
96231b3b80d8