x + 0.0      simplify gives unchanged
x + (-0.0)   simplify gives x
x * 1.0      simplify gives x
x * 0.0      simplify gives unchanged
   at x = -0.0:  x+0.0 -> 0.0   x*0.0 -> -0.0
   at x = inf:  x+0.0 -> inf   x*0.0 -> nan
   at x = nan:  x+0.0 -> nan   x*0.0 -> nan
