FastISel wasn't checking the isFPOnlySP subtarget feature before emitting
double-precision operations, so it got completely invalid CodeGen for doubles
on Cortex-M4F.
The normal ISel testing wasn't spectacular either so I added a second RUN line
to improve that while I was in the area.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@296031 91177308-0d34-0410-b5e6-96231b3b80d8
Tim Northover