What is acceptable for -ffast-math? (Was: associative law in combine)

[Gabriel Dos_Reis]

| Gabriel.Dos_Reis@sophia.inria.fr said:
| > | and probably a whole lot of other things that are equally "dubious".
| > |  |  | > But then, if they would have written that form in the first
| > place. |  | But, as I said, there might be cases where you can't write
| > it in an | optimized way in the first place, such as in |   inline
| > double f() { return a/b; } |   inline double g() { return c;   } |   x
| > = f()/g(); | plus inlining. 
| 
| > But then is 0.0 is acceptable for 0.125 for speed? 
| 
| Yes, if you know by advance that this cannot happen because of your 
| input data accuracy. Then you will get the speed advantage without 
| the loss of accuracy since it cannot happen.

Data for the supposed speed in such case are still missing.

-- Gaby