http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46080
--- Comment #3 from Uros Bizjak <ubizjak at gmail dot com> 2010-10-20 08:28:57
UTC ---
(In reply to comment #2)
> Created attachment 22089 [details]
> sh script to test sqrtf
>
> Similar problems can also be found with:
>
> printf ("%.60f\n%.60f\n%.60f\n", sqrtf(x), sqrtf(x), sqrtf(x));
>
> I've found that every GCC version I could test was showing some incorrect
> behavior (but GCC 4.2.4 was the most consistent one). With the attached
> script,
> I get:
>
> -DSEP -O0 -O1 -O2
> GCC 3.4.6 SSS SSS SDD SDD
> GCC 4.1.3 SSS SSS DSS DDS
> GCC 4.2.4 SSS SSS DDD DDD (x86)
> GCC 4.3.5 SSS SSS DSS DDD (ditto with GCC 4.3.2 on x86)
> GCC 4.4.5 DSS SSD DSS DDD
>
> where S means that one gets the result in single precision (as expected) and D
> means that one gets the result in double precision.
You should use -ffloat-store to remove excess precision.
