------- Additional Comments From paolo dot bonzini at lu dot unisi dot ch 2005-09-30 14:13 ------- Subject: Re: [4.1 Regression] Massive performance regression for -ffast-math due to the recip tree pass
>Currently, there seems to be some problems, i.e.: > >double pov::f_polytubes(double*, unsigned int) (ptr, D.22748) > >- D.22787_46 = -6.28318530717958623199592693708837032318115234375e+0 / >D.22783_80; >+ reciptmp.882_72 = 1.0e+0 / D.22783_80; >+ D.22787_46 = -6.28318530717958623199592693708837032318115234375e+0 * >reciptmp.882_72; > >Not needed, only one user. > > no, there is another user in another basic block. >Function double pov::POVFPU_RunDefault(pov::FUNCTION) > > <L193>:; >- r0_1660 = r0_89 / r0_89; >+ reciptmp.492_84 = 1.0e+0 / r0_89; >+ r0_1660 = r0_89 * reciptmp.492_84; > goto <bb 1062> (<L1339>); > >The result of above confusion is (1.0)! We are in fast-math, so no NaNs, etc.. > >void pov::Simulate_Media(pov::IMEDIA**, pov::RAY*, pov::INTERSECTION* >- reciptmp.1152_907 = 1.0e+0 / prephitmp.1124_293; >- reciptmp.1153_1046 = 1.0e+0 / prephitmp.1124_293; >- reciptmp.1154_1041 = 1.0e+0 / prephitmp.1124_293; >+ reciptmp.1275_1270 = 1.0e+0 / prephitmp.1124_293; >+ reciptmp.1152_907 = 1.0e+0 * reciptmp.1275_1270; >+ reciptmp.1153_1046 = 1.0e+0 * reciptmp.1275_1270; >+ reciptmp.1154_1041 = 1.0e+0 * reciptmp.1275_1270; > >These are all the same? There are already reciptmp variables in loopdone that >are all the same. And there are quite some places that have this problem. > > I think the final DOM run ought to simplify the other problems. Paolo -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24123
