------- Comment #5 from hjl at lucon dot org 2007-06-02 00:10 ------- (In reply to comment #3) > (In reply to comment #2) > > Is that OK to transform > > > > float sf; > > ... > > sf = 500 * sf; > > for (i = 0; i < ceplen; i++) > > sum[i] *= sf; > > > > to > > > > for (i = 0; i < ceplen; i++) > > sum[i] = (sum[i]* 500)*sf; > > > > You can certainly get the different results when sf is small and sum[i] is > > large. > > with -ffast-math, this transformation is ok (although it does not seem to make > sense to do it, it moves a multiplication into a loop). >
We moved a multiply, which is outside of loop in source, into a loop. I don't think gcc should do it with any optimization flag, including -ffast-math. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32183
