[InstSimplify] Deduce correct type for vector GEP.

InstSimplify returned the wrong type when simplifying a vector GEP
and we ended up crashing when trying to replace all uses with the
new value. Fixes PR32697.

Differential Revision: https://reviews.llvm.org/D32180

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300693 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed