On 2018-02-06 17:14:38 +0100, Vincent Lefevre wrote: > Now, I've just found a "regression" when comparing Sipe results with > MPFR results, but it is the Sipe result with SIPE_FLOAT equal to 1 > (float) or 2 (double) that is incorrect, 3 (long double) being OK. > Bug triggered with -O2 -march=native on an Intel Xeon E5-2609 v3 > machine. At least from 4.9 to 8.0.1 20180124 [trunk revision 257009] > are affected. I'll try to find a simple test case for a bug report. > I suspect that the regression comes from the fact this is a new > machine + the use (as in the past) of -march=native.
Well, if I add -std=c99 or -std=c11, the failure disappears. The reason is that GCC generates a FMA (indeed, this new machine has a FMA), but this occurs across different C statements. So, maybe not a bug, but a bad feature, IMHO. -- Vincent Lefèvre <vinc...@vinc17.net> - Web: <https://www.vinc17.net/> 100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/> Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)
