I'd like to do it, but I'd need some help as I don't have so much free personal time :) I already tried it and it's not so trivial since I have no idea about most of the changes made to gcc/binutils and I don't know what I'd need to take into updated gcc. That's why I asked in my other email what svn version exactly was taken as baseline for current cegcc 4.4.0 so that I could make a diff and apply same changes to latest gcc to see it works or not. I think log2 is fixed in other versions of gcc; Android build at least doesn't have that log2 problem.
> -----Original Message----- > From: Zack [mailto:f...@comcast.net] > Sent: Saturday, July 10, 2010 23:19 > To: Pavel Pavlov > Subject: Re: [Cegcc-devel] Are math functions busted??.. (4.1.0 & 4.4.0) > > I only tried using log2. Perhaps a more comprehensive test is in order... > > I don't know why people would abandon Cegcc, unless perhaps they were > using it for professional projects, and selling their products to phone users. > Hobbyists like myself would not care so much what Microsoft does or when. > But if they are using it for professional projects, why is log2 broken? It's a > contradiction. > > It may be worth updating to the latest gcc. My question is, how much work is > involved... and who will do it? > -Zack > > >> -----Original Message----- > >> From: Zack [mailto:f...@comcast.net] > >> Sent: Saturday, July 10, 2010 23:08 > >> To: Pavel Pavlov > >> Subject: Re: [Cegcc-devel] Are math functions busted??.. (4.1.0& > >> 4.4.0) > >> > >> I reported the log2 problem a couple months ago to this mailing > >> list but no one responded. > >> -Zack > > > > Hi Zack, did you have any similar problems with any other math functions? > > It seems that people are not interested in cegcc since MS plans not to > > support native development on their upcoming WinPhone7 (I doubt that > > anyways) > > > > > >>> I tried to compile x264 out of curiosity and when I finally built it > >>> I tried to run > >> the code and got error message from x264 encoder saying that it was > >> miscompiled. > >>> After debugging the code I found out what was the source of error > >>> and > >> what code was miscompiled. > >>> Basically, log2 and log2f function return wrong results. So, I'm > >>> curios if it's a > >> known issue and if there might be some other unpleasant surprises > >> with some other math functions. > >>> A simple test to verify wrong results: > >>> > >>> #include<math.h> > >>> > >>> #define log2f_correct(x) (logf(x) * 1.44269504088896340736f) > >>> > >>> for(int lambda=0; lambda<5; ++lambda){ > >>> for(int i=2010; i<2020; ++i){ > >>> printf ("TEST1: lambda: %d, xxx => %f; log2f(i+1) => %f\n", > >> lambda, lambda * (log2f(i+1)*2 + 0.718f + !!i) + .5f, log2f(i+1)); > >>> printf("TEST2: lambda: %d, xxx => %f; log2f_correct (i+1) => > >> %f\n", lambda, lambda * (log2f_correct (i+1)*2 + 0.718f + !!i) + .5f, > >> log2f_correct(i+1)); > >>> } > >>> } > >>> > >>> Results are always incorrect, here's a sample output: > >>> [INFO ] [-2071554222] 18:28:17: x264: TEST2: lambda: 1, 2013 xxx => > >>> 24.168262; log2f_correct (i+1) => 10.975131 [INFO ] [-2071554222] > >>> 18:28:17: x264: TEST1: lambda: 1, 2013 xxx => 12.764759; log2f(i+1) > >>> => 5.273379 > >>> > >>> > >>> > >>> > >>> It has to be some sort of loop with expression, otherwise gcc will > >>> compute log2f at compile time and will produce correct output (that > >>> matches results of log2f_correct) > >>> > >>> I verified it with both builds of cegcc and had identical errors. > >>> > > ------------------------------------------------------------------------------ This SF.net email is sponsored by Sprint What will you do first with EVO, the first 4G phone? Visit sprint.com/first -- http://p.sf.net/sfu/sprint-com-first _______________________________________________ Cegcc-devel mailing list Cegcc-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/cegcc-devel
