logic in Math.nextAfter for handling -0.0 input

[Deneau, Tom]

The JDK method Math.nextAfter contains the logic shown below to handle an input of -0.0

When the graal compiler compiles this for the hsail backend, it makes the reasonable
assumption that "start + 0.0d" can be reduced to "start" which is a problem for this algorithm.

>From what I could tell, c2 or graal for amd64 backend do not do this optimization
and so get the right answer for -0.0 input.  How do they know not to do this optimization?


        } else {        // start > direction or start < direction
            // Add +0.0 to get rid of a -0.0 (+0.0 + -0.0 => +0.0)
            // then bitwise convert start to integer.
            long transducer = Double.doubleToRawLongBits(start + 0.0d);         <==============

            if (direction > start) { // Calculate next greater value
                transducer = transducer + (transducer >= 0L ? 1L:-1L);
            } else  { // Calculate next lesser value
                  ....

-- Tom