PING On Wed, Mar 14, 2012 at 01:03, Janne Blomqvist <blomqvist.ja...@gmail.com> wrote: > Hi, > > the attached patch implements a few fixes and cleanups for the MOD and > MODULO intrinsics. > > - When the arguments are constant, use mpfr_fmod instead of the naive > algorithms which are numerically unstable for large arguments. This > extends the PR 24518 fix to constant arguments as well, and makes the > compile-time evaluation match the runtime implementation which also > uses fmod in the same manner. > > - Remove the old fallback path for the case builtin_fmod is not > available, as the builtin is AFAICS always available. > > The patch does not per se fix the corner-case bug as reported in PR > 49010, in fact it makes it worse in a way as with the patch the result > if the arguments are parameters is the same as the runtime result > (previously, the compile-time result was correct). But, I think we > should leave it as it is. Due to the reasons above, we're not using > the naive algorithms anyway, and IMHO -0.0 is quite a good > approximation for +0.0 anyway. One might even argue that due to the > numerical instability, specifying the naive algorithms is a bug in the > standard. > > The patch adds notes to the documentation about the usage of fmod, so > users interested in corner-case behavior can look up how that function > is supposed to behave on their target. FWIW, AFAICS MPFR and glibc > fmod conform to the behavior specified in C99 Annex F. > > Regtested on x86_64-unknown-linux-gnu, Ok for trunk? > > 2012-03-14 Janne Blomqvist <j...@gcc.gnu.org> > > PR fortran/49010 > PR fortran/24518 > * intrinsic.texi (MOD,MODULO): Mention usage of fmod instead of > naive algorithm. > * simplify.c (gfc_simplify_mod): Use mpfr_fmod. > (gfc_simplify_modulo): Likewise. > * trans-intrinsic.c (gfc_conv_intrinsic_mod): Remove fallback as > builtin_fmod is always available. > > > -- > Janne Blomqvist
-- Janne Blomqvist
