Date: Wed, 5 May 2004 21:59:36 -0700 From: Marcel Moolenaar <marcel@xcllnt.net> To: David Schultz <das@FreeBSD.ORG> Cc: alpha@FreeBSD.ORG Subject: Re: Problems with floating point exception flags Message-ID: <20040506045936.GA24034@dhcp01.pn.xcllnt.net> In-Reply-To: <20040506043137.GA10641@VARK.homeunix.com> References: <20040428064116.GA7870@VARK.homeunix.com> <20040504133904.GA22084@VARK.homeunix.com> <20040506020629.GA23555@dhcp01.pn.xcllnt.net> <20040506043137.GA10641@VARK.homeunix.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On Wed, May 05, 2004 at 09:31:38PM -0700, David Schultz wrote: > On Wed, May 05, 2004, Marcel Moolenaar wrote: > > On Tue, May 04, 2004 at 06:39:04AM -0700, David Schultz wrote: > > > > > > Here is a better kernel patch. Instead of treating all the bits > > > of the FPCR as sticky, it merely treats the exception flags that > > > way. After reading the source carefully, I'm pretty sure this is > > > the right fix, but I can't test it without working hardware. > > > I also uncovered a bug in the way the software floating-point > > > routines handle underflow. See below. > > > > I built and booted a kernel with these patches. Trying to exercise the > > code with the files at http://people.freebsd.org/~das/alpha yield: > > Thanks! > > > alpha% ./te > > Should be 00: 00 > > Floating exception (core dumped) > > May 5 19:00:11 alpha kernel: pid 638 (te), uid 4152: exited on signal 8 (core dumped) > > You need to compile the program with gcc's -mieee option in order > to get floating point to work in a reasonable way on alpha. If > you could try the program compiled with -mieee, that would be great. Attached a fix for fenv.h. All files newly downloaded from ~das/alpha alpha% cc -g -mieee -o te te.c alpha% ./te Should be 00: 00 Should be 14: 14 Should be 1c: 1c Should be 1e: 1e Should be 1e: 1e alpha% cc -g -mieee -o test-fenv test-fenv.c -lm main() in test-fenv.c:111, "fetestexcept(FE_ALL_EXCEPT) == 0" main() in test-fenv.c:117, "fetestexcept(FE_ALL_EXCEPT) == 0" main() in test-fenv.c:121, "fetestexcept(ALL_STD_EXCEPT) == (ALL_STD_EXCEPT & ~FE_DIVBYZERO)" main() in test-fenv.c:125, "fetestexcept(FE_ALL_EXCEPT) == FE_INEXACT" main() in test-fenv.c:127, "fetestexcept(FE_ALL_EXCEPT) == 0" main() in test-fenv.c:131, "fetestexcept(FE_ALL_EXCEPT) == FE_INEXACT" main() in test-fenv.c:134, "fetestexcept(FE_ALL_EXCEPT) == (FE_INEXACT | FE_DIVBYZERO | FE_UNDERFLOW)" main() in test-fenv.c:136, "fetestexcept(FE_ALL_EXCEPT) == 0" main() in test-fenv.c:139, "(fegetmask() & ALL_STD_EXCEPT) == 0" main() in test-fenv.c:143, "fetestexcept(ALL_STD_EXCEPT) == FE_DIVBYZERO" main() in test-fenv.c:146, "expecting_trap == 0" main() in test-fenv.c:148, "fetestexcept(ALL_STD_EXCEPT) == 0" main() in test-fenv.c:153, "fetestexcept(ALL_STD_EXCEPT) == 0" main() in test-fenv.c:156, "expecting_trap == 0" main() in test-fenv.c:158, "fetestexcept(ALL_STD_EXCEPT) == 0" main() in test-fenv.c:160, "(fegetmask() & ALL_STD_EXCEPT) == 0" main() in test-fenv.c:165, "fegetround() == FE_DOWNWARD" main() in test-fenv.c:166, "getround() == FE_DOWNWARD" main() in test-fenv.c:168, "getround() == FE_UPWARD" main() in test-fenv.c:169, "fegetround() == FE_UPWARD" main() in test-fenv.c:171, "getround() == FE_TOWARDZERO" main() in test-fenv.c:172, "fegetround() == FE_TOWARDZERO" main() in test-fenv.c:179, "getround() == FE_DOWNWARD" main() in test-fenv.c:181, "getround() == FE_UPWARD" FYI, -- Marcel Moolenaar USPA: A-39004 marcel@xcllnt.net
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20040506045936.GA24034>