ARM: make sure FastISel bails on f64 operations for Cortex-M4.

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.

llvm-svn: 296031
2 files changed