Rewrite this test properly with a FileCheck instead of greps


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173997 91177308-0d34-0410-b5e6-96231b3b80d8
stripAndComputeConstantOffsets is only called on pointers; check this
with an assert instead of failing and requiring callers to check for failure.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173998 91177308-0d34-0410-b5e6-96231b3b80d8