Date: Thu, 6 Feb 2020 15:02:58 -0500 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: Re: Q: dealing with missing removal of excess precision On Thu, Feb 06, 2020 at 02:03:44PM -0500, Rich Felker wrote: > On Thu, Feb 06, 2020 at 12:46:08PM -0500, Rich Felker wrote: > > On Thu, Feb 06, 2020 at 08:15:30PM +0300, Alexander Monakov wrote: > > > On Thu, 6 Feb 2020, Rich Felker wrote: > > > > > > > I think I might like to go ahead and apply these patches now, or at > > > > least some of them -- the ones fixing excess precision -- rather > > > > waiting, because I got a report of a nasty bug stemming from excess > > > > precision of the inverse trig functions: > > > > > > That might be exactly the empty set of patches, as I did not yet post > > > any for functions that might return with excess precision. > > > > Indeed, I just discovered that... > > > > > Be advised that I found bugs in my patches, so given that no one so far > > > has pointed them out on the mailing list indicates that either nobody > > > bothered to review, or people are keeping the findings to themselves. > > > > I think it's just that I was planning to do further review after > > release rather than before since I'm trying to get the release out.. > > > > > > If writing and testing the remaining i386 functions before release is > > > > not practical, I wonder if just removing the asm for now, and adding > > > > back the new code in next release cycle would be a good idea. Or I > > > > could just leave it, but I don't like making a release with "known > > > > bugs of consequence" like this. > > > > > > I think fixing excess precision in inverse trig functions might be > > > easier than removing the asm entirely. > > > > Yes, what I'm looking at right now is fixing inverse trig and log > > functions and removing the exp asm (since the exp logic is way too > > messy for me to feel comfortable modifying right now) and possibly > > re-adding it later as inline asm with the flow control in C. > > FWIW nsz's new C exp seems considerably faster than the existing 386 > asm on my box (Atom S1260) (6.7s vs >8s for summing exp(x) from > x=-2..2 stepping 0x1p-24). Test program attached in case anyone else > wants to try it. > > So I think just removing exp*.s is the right approach for now. The > long double ones should actually be left, and that raises the issue > that expm1l is wrongly using the exp code rather than expl code nsz > added long ago in a8f73bb1a685dd7d67669c6f6ceb255cfa967790. I won't > try to fix this yet but will just move the files around so we can rm > the float/double ones and use the C for them without getting rid of > the ld asm. Attachment was missing. Rich View attachment "exptime.c" of type "text/plain" (117 bytes)
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