tighten up checks

tighten up checks

We manage to generate all of the matching instructions (and a lot more) via
the reciprocal optimization function - even if we completely remove the square
root optimization. With CHECK_NEXT, we assure that we're executing the
expected square root optimization paths and not generating extra insts.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218284 91177308-0d34-0410-b5e6-96231b3b80d8