Bug#781892: (Hardware?) problem with denormal values on mipsel

Hi,

On Tue, May 26, 2015 at 10:13:35AM +0100, James Cowgill wrote:
> On Sun, 2015-05-24 at 22:32 +0300, Aaro Koskinen wrote:
> > On Fri, May 22, 2015 at 11:00:18PM +0100, James Cowgill wrote:
> > > On Sat, 2015-05-23 at 00:04 +0300, Aaro Koskinen wrote:
> > > > On Fri, May 22, 2015 at 05:27:14PM +0100, James Cowgill wrote:
> > > > > Yep it's a hardware problem. The following assembly dies (raises SIGILL)
> > > > > at 'sqrt.s' on the Loongsons and works everywhere else:
> > > > > 
> > > > > ===
> > > > >         .set mips2
> > > > >         .text
> > > > >         .global main
> > > > >         .type main, @function
> > > > > main:
> > > > >         lui $t0, %hi(value)
> > > > >         lwc1 $f0, %lo(value)($t0)
> > > > >         nop
> > > > >         sqrt.s $f0, $f0
> > > > >         jr $ra
> > > > > 
> > > > >         .data
> > > > > value:
> > > > >         .float 1.1342362e-39
> > > > > ===
> > > > 
> > > > Is this a standalone reproducer program for the problem? Because
> > > > I tried it on on my Loongson box and didn't get any SIGILL...
> > > 
> > > It should be. I tried it on some 3A machines at work and it crashed
> > > there (and then some other machines which didn't crash). There's a 2F I
> > > can try on Tuesday.
> > 
> > My Loongson is 2F...
> 
> I tried it on my 2F (it's a Lemote Fuloong) and it crashed there as well
> (both the gfortran and my testcase). It's running up to date jessie.
> 
> What compiler versions do you have?
> What does the 'cpu model' line say in /proc/cpuinfo?

I'm using binutils 2.25, GCC 5.1, Linux 4.1-rc5. The cpu model is:

cpu model               : ICT Loongson-2 V0.3  FPU V0.1

> > > Does the original gfortran code crash for you?
> > 
> > I don't have gfortran available on my system.
> 
> Don't you run Debian?

Not at the moment.

A.