[PATCH] PR16258 - fadd with undef not folded

[Stephen Canon]

On Jun 10, 2013, at 8:50 AM, Duncan Sands <baldrick at free.fr> wrote:

>>> If undef can't be achieved, it might still be possible to fold to a NaN
>>> or some other special value.
>> 
>> Folding to NaN sounds workable to me.
> 
> So if Y is a well-chosen NaN (or will any NaN do?) then fadd X, Y will always
> be equal to Y?  Does the same go for fmul, fsub and fdiv?

If Y is any NaN, then the result of any IEEE-754 basic operation (add, sub, mul, div, sqrt, ... ) will be NaN (it will not “be equal to Y", because NaNs compare unequal to everything).

- Steve
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