Re: [Qemu-ppc] [Qemu-devel] Floating point unit bugs

[Aurelien Jarno]

On 2017-05-08 18:09, G 3 wrote:
> 
> On May 8, 2017, at 5:54 PM, Aurelien Jarno wrote:
> 
> > On 2017-05-07 17:48, G 3 wrote:
> > > I made a diagnostic program for the floating point unit. It will test
> > > various PowerPC floating point instructions for compatibility with
> > > the
> > > PowerPC G3 processor. It was tested on a PowerPC G3 and G5 system.
> > > The
> > > results of the program in qemu-system-ppc were pretty bad. About
> > > every
> > > instruction tested is not implemented correctly.
> > 
> > I don't say that qemu-system-ppc is bug free, but this looks suspicious
> > that about every instruction is buggy.
> 
> I really hope you don't think I'm blaming anyone. I'm only reporting the
> results of the test.
> 
> > Have you tried to run your
> > program on a real G3 or G5 system?
> 
> Yes. I made sure it ran on a real G3 and G5 system without problem before
> testing it on QEMU. I suspect the Motorola designed G4 processor will not be
> compatible. I don't have a working G4 system to verify this unfortunately.
> 
> > 
> > [ snip ]
> > 
> > > 
> > > Here is the full test results after running this program in 
> > > qemu-system-ppc
> > > with a Mac OS 10.4 guest:
> > > 
> > > 
> > > 
> > > 
> > > fadd test failed
> > > expected answer: 0x3ff3333333333334
> > >   actual answer: 0x8200400000000024
> > > expected fpscr: 0x82064000
> > >   actual fpscr: 0x82004000
> > 
> > This looks highly suspicious that the actual answer match the expected
> > answer.
> 
> You can use this web page to find the decimal value: 
> http://www6.uniovi.es/~antonio/uned/ieee754/IEEE-754hex64.html
> 
> 0x3ff3333333333334 = 1.2000000000000002
> 0x8200400000000024 = -4.8529708162167760e-299
> 
> The expected answer and actual answer are very far from each other.

Yes, I made a typo in my comment. I wanted to say that I found very
suspicious that the actual answer match the actual fpscr. See my other
mail for the reason.

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
address@hidden                 http://www.aurel32.net