I was trying to compile code with -march=+nosimd and hit various
instruction predicate verification errors, this patch should address the
ones I saw in integer to floating-pointer conversions.
I noticed that for signed conversions, some non-NEON instruction sequences
are shorter. I don't know if the longer one is still faster on current
architectures (the patterns date back to the initial backend import)
Perhaps just extend the previous HasNeon block? I'm not sure that's clearer though.