Alexander Monakov schrieb:
> This transformation is indeed included into -ffast-math. I checked with
>
> $ gcc --version
> gcc (GCC) 4.1.1 20070105 (Red Hat 4.1.1-52)
>
> and it does eliminate the calculation. What does generated assembly code look
> like in your case? Note you may as well check on this code:
>
> double f(double a, double c)
> {
> return c - (c - a);
> }
That's interesting. After your answer I checked with a gcc from Fedora
Core (Werewolf) and this removes it also. It seems like a backported
enhancement from vanilla gcc, version 4.3.0 does it as well.
Cheers,
Christian
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