Artyom: That's precisely the point. The true IEEE754 variants where precision does matter should be part of a different class. What Edward and Yitz want is an "optimized" multiply-add where the semantics is the same but one that goes faster.

On Mon, May 4, 2015 at 10:40 AM, Artyom <yom@artyom.me> wrote:
On 05/04/2015 08:36 PM, Levent Erkok wrote:
In particular, the compiler should be free to substitute "a*b+c" with "mulAccum a b c".
 But isn't it unacceptable in some cases? For instance, in this case (taken from Wikipedia):
If x2 − y2 is evaluated as ((x×x) − y×y) using fused multiply–add, then the result may be negative even when x = y due to the first multiplication discarding low significance bits. This could then lead to an error if, for instance, the square root of the result is then evaluated.


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