[InstSimplify] Handle selects of GEPs with 0 offset

In particular (since it wouldn't fit nicely in the summary):
(select (icmp eq V 0) P (getelementptr P V)) -> (getelementptr P V)

Differential Revision: https://reviews.llvm.org/D31435


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@301880 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed