On Wed, Mar 13, 2019 at 10:40:28AM -0700, Conrad Meyer wrote: > Hi John, > > On Wed, Mar 13, 2019 at 10:17 AM John Baldwin <j...@freebsd.org> wrote: > > One issue I'm aware of is that clang does not have any support for the > > special arrangement FreeBSD/i386 uses where it uses different precision > > for registers vs in-memory for some of the floating point types (GCC has > > a special hack that is only used on FreeBSD for this but isn't used on > > any other OS's). I wonder if that could be a factor? Volatile probably > > forces a round trip between memory which might explain why this is the > > case. > > > > I wonder what your test program does on i386 Linux with GCC? > > $ uname -sr > Linux 4.20.4 > $ gcc --version > gcc (GCC) 8.2.1 20181215 (Red Hat 8.2.1-6) > ... > $ rpm -qf /usr/lib/libm-2.27.so > glibc-2.27-37.fc28.i686 > > $ gcc -m32 -fno-builtin -o z kargl.c -lm && ./z > Max ULP: 1.959975 > Count: 0 > $ gcc -O -m32 -fno-builtin -o z kargl.c -lm && ./z > Max ULP: 1.959975 > Count: 0 > $ gcc -O1 -m32 -fno-builtin -o z kargl.c -lm && ./z > Max ULP: 1.959975 > Count: 0 > $ gcc -O2 -m32 -fno-builtin -o z kargl.c -lm && ./z > Max ULP: nan > Count: 0 > $ gcc -O3 -m32 -fno-builtin -o z kargl.c -lm && ./z > Max ULP: nan > Count: 0 > > Uh. > > kargl.c: In function ‘main’: > kargl.c:80:10: warning: ‘u’ may be used uninitialized in this function > [-Wmaybe-uninitialized] > if (ur > u) u = ur; > ^
Whoops. There are a number of variations on a theme named a.c. Initializing u to 0 doesn't change the outcome with clang on FreeBSD. -- Steve _______________________________________________ freebsd-toolchain@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-toolchain To unsubscribe, send any mail to "freebsd-toolchain-unsubscr...@freebsd.org"
