The following shows a problem on the Alpha whereby
the division 2/3 made on floats is flagged as exact.
Here are the details:
$ cat sf.cc
#include <fenv.h>
#include <cstdio>
int main() {
float x = 2;
float y = 3;
feclearexcept(FE_INEXACT);
x = x / y;
printf("%d %.1000g\n", fetestexcept(FE_INEXACT) != 0, x);
}
$ g++ -v
Using built-in specs.
Target: alpha-linux-gnu
Configured with: ../src/configure -v
--enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --enable-shared
--with-system-zlib --libexecdir=/usr/lib --without-included-gettext
--enable-threads=posix --enable-nls --with-gxx-include-dir=/usr/include/c++/4.2
--program-suffix=-4.2 --enable-clocale=gnu --enable-libstdcxx-debug
--enable-objc-gc --enable-mpfr --disable-libssp --with-long-double-128
--enable-checking=release --build=alpha-linux-gnu --host=alpha-linux-gnu
--target=alpha-linux-gnu
Thread model: posix
gcc version 4.2.4 (Debian 4.2.4-3)
$ g++ -mieee-with-inexact sf.cc
$ ./a.out
0 0.666666686534881591796875
$ cat /proc/cpuinfo
cpu : Alpha
cpu model : EV56
cpu variation : 7
cpu revision : 0
cpu serial number :
system type : Rawhide
system variation : Tincup
system revision : 0
system serial number : AY74642662
cycle frequency [Hz] : 399642346 est.
timer frequency [Hz] : 1200.00
page size [bytes] : 8192
phys. address bits : 40
max. addr. space # : 127
BogoMIPS : 705.16
kernel unaligned acc : 0 (pc=0,va=0)
user unaligned acc : 31 (pc=20000074c18,va=87)
platform string : AlphaServer 1200 5/400 4MB
cpus detected : 1
cpus active : 1
cpu active mask : 0000000000000001
L1 Icache : 8K, 1-way, 32b line
L1 Dcache : 8K, 1-way, 32b line
L2 cache : 96K, 3-way, 64b line
L3 cache : 4096K, 1-way, 64b line
$
I attach the generated assembly code, which shows this is not a constant
propagation issue.
--
Summary: IEEE inexact-flag not working on the Alpha
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: bagnara at cs dot unipr dot it
GCC host triplet: alphaev56-unknown-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37581
