[PATCH]: PR29335 use MPFR for builtins fma, fmin and fmax

[Paolo Bonzini]

> 'If just one argument is NaN, the fmax functions return the other
> argument (if both
> arguments are NaNs, the functions return NaN).
> 
> The body of the fmax function might be
>   { return (isgreater (x, y) || isnan(y)) ? x : y; }
> "
> 
> but I agree that the one-argument NaN thing is stupid and not what would be
> usually expected.

Yeah, NaN propagation would be the expected behavior in that case!  And 
Java got it right, actually: grep for min(float or max(float in 
libjava/java/lang/Math.java.

> In a footnote it says
> 
> "Ideally, fmax would be sensitive to the sign of zero, for example
> fmax (-0.0, 0.0)
> would return 0; however, implementation in software might be impractical."

<ironic>
They mean, as impractical as "a == b ? a & b : (a > b ? a : b)" (I 
really mean & as bitwise AND)?  Or likewise, "a == b ? a | b : (a < b ? 
a : b)" for fmin?
</ironic>

Java BTW also got this right, though they have no &/| on float and they 
resort to a special case for a == 0 && b == 0.

Paolo