Fix a typo where we were creating <def,kill> operands instead of

<def,dead> ones.

Add an assertion to make sure we catch this in the future.

Fixes <rdar://problem/15464559>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195401 91177308-0d34-0410-b5e6-96231b3b80d8