Make fma use of Dekker and Knuth algorithms use round-to-nearest (bug 14796)

[Richard Henderson]

On 2012-11-01 19:14, Joseph S. Myers wrote:
> +      libc_feupdateenv (&env);
> +      /* Ensure that round-to-nearest value of z + m1 is not
> +	 reused.  */
> +      asm volatile ("" : "=m" (z) : "m" (z));

We have math_opt_barrier and math_force_eval.
We should use them and not spread more raw asms.

I know there are plenty of other existing instances
that should also be fixed, but we shouldn't add more.

Otherwise the actual logic looks ok.


r~