[ImplicitNullChecks] Account for implicit-defs as well when updating the liveness.

The replaced load may have implicit-defs and those defs may be used
in the block of the original load. Make sure to update the liveness
accordingly.

This is a generalization of r267817.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@268412 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed