On Sun, 8 Mar 2009, Sylvain Pion wrote: > this pragma. I nevertheless try to find grants for funding > people to implement some related things in GCC. And I also > contribute time to help in the guidance of GCC with my > expertise in this particular area, even if it requires a lot > of time to convince people. So, please...
Finding funding for implementing standard pragmas and completing the -frounding-math implementation is likely to be more productive than arguing about a default for an option that is known to have problems. All the people discussing the issue are familiar with the floating point optimization issues in GCC. (I have added many such bugs to the dependencies of bug 16989 in the past to help track them, and just added some more.) Since as far as I know all work done on the floating-point issues has been done as volunteers, time spent discussing the defaults is only going to mean time not available for implementing this or other features. > > The default is in accordance with standard requirements, and more more > > conservative than other compilers which tend to enable their -ffast-math > > equivalents by default rather than just -fno-rounding-math. > > At least these others have chosen to do it more consistently. > They don't claim their default is anything sane at all for > serious FP computations, which at least is clear. GCC does not try to make such a claim; it depends entirely on your definition of "serious FP computations", which is clearly a bikeshed discussion even if the discussion of defaults isn't. GCC provides various options and documents the defaults. The defaults are deliberate decisions (and as such the adoption of those decisions cannot meaningfully be considered a regression: it's not a bug but a feature), but are more likely to change in the other direction from what you want. > Moreover, standards are far from saying anything about the best default > for -frounding-math, it's a GCC matter. And GCC maintainers should > be able to listen to expert users to help them making good choices. GCC maintainers must also bear in mind the bulk of users for whom the default options, complete with other issues such as x87 excess precision, are just fine, and the value of good benchmark scores in marketing GCC. (You will of course nevertheless note that I have fixed PR 323 for C for 4.5.) -- Joseph S. Myers jos...@codesourcery.com
