Re: where to discuss problems with IEEE 754 standard on x86 architecture?

[Petr Savicky <savicky at cs dot cas dot cz>]

> You were using -mfpmath=387 (possible as the default), and that uses
> Intel native arithmetic, which is NOT standard IEEE 754 double, but
> an extended format.
> 
> If you use -mfpmath=sse, you will get what you expect.
> 
Thank you for your reply. This explains the problem.

However, solving the problem seems to be harder.
I tried "gcc -mfpmath=sse", but obtained the warning:
 SSE instruction set disabled, using 387 arithmetics.

gcc version: 3.3.3
uname -m -p -i: i686 i686 i386
/proc/cpuinfo:
  vendor_id   : GenuineIntel
  cpu family  : 15
  model       : 2
  model name  : Intel(R) Xeon(TM) CPU 2.80GHz

I obtained the same on another computer with
gcc version: 4.1.0
uname -m -p -i: i686 i686 i386
/proc/cpuinfo:
  vendor_id   : GenuineIntel
  cpu family  : 6
  model       : 8
  model name  : Celeron (Coppermine)

man gcc says: For the i386 compiler, you need to use -march=cpu-type, -msse or -msse2 switches
               to enable SSE extensions and make this option effective.
The choices for cpu-type are the same as for -mtune. 
-mtune=cpu-type has possible values itanium, itanium1, merced, itanium2, and mckinley
   none of which seems to fit my computers.

With "gcc -mfpmath=sse -msse" I obtained no warning/error, but the program
behaves in the old wrong way.

So, I think that SSE is not available on my computers. Is this correct?

All the best, Petr.