Re: [Qemu-devel] [PATCH 17/19] target-ppc: fix SPE comparison functions

[Aurelien Jarno <aurelien@aurel32.net>]

On Tue, Apr 12, 2011 at 07:40:33PM -0700, Nathan Froyd wrote:
> On Tue, Apr 12, 2011 at 11:59:29PM +0200, Aurelien Jarno wrote:
> > Given that float32_*() functions are IEEE754 compliant, the efscmp*()
> > functions are correctly implemented, while efstst*() are not. This
> > patch reverse the implementation of this two groups of functions and
> > fix the comments. It also use float32_eq() instead of float32_eq_quiet()
> > as qNaNs should not be ignored.
> 
> Thanks for addressing this; the E500 emulation in QEMU is more like how
> we wish the hardware acted, rather than how it actually acts. :)
> 
> It's late here, but I think this change:
> 
> > -static inline uint32_t efscmplt(uint32_t op1, uint32_t op2)
> > +static inline uint32_t efststlt(uint32_t op1, uint32_t op2)
> >  {
> > -    /* XXX: TODO: test special values (NaN, infinites, ...) */
> > +    /* XXX: TODO: ignore special values (NaN, infinites, ...) */
> >      return efststlt(op1, op2);
> >  }
> 
> is not correct, as you've just turned this into an infinite (inlined!)
> loop.  You'd want to change the efststlt call into an efscmplt call.
> Similarly for efstst{gt,eq}.
> 

Thanks for catching that, I'll fix that in the next version.

-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
aurelien@aurel32.net                 http://www.aurel32.net