Re: [PATCH] softfloat: Fix the incorrect computation in float32_exp2()

[Shivaprasad G Bhat]

Hi Richard,


On 5/3/23 01:11, Richard Henderson wrote:
> On 5/2/23 16:25, Shivaprasad G Bhat wrote:
> > The float32_exp2() is computing wrong exponent of 2.
> > For example, with the following set of values {0.1, 2.0, 2.0, -1.0},
> > the expected output would be {1.071773, 4.000000, 4.000000, 0.500000}.
> > Instead, the function is computing {1.119102, 3.382044, 3.382044, 
> > -0.191022}
<snip>
> > his is because instead of the xnp which holds the numerator,
> > parts_muladd is using the xp which is just 'x'. The commit 
> > '572c4d862ff2'
> > refactored this function, and it seems mistakenly using xp instead of 
> > xnp.
> >
> > The patches fixes this possible typo.
> >
> > Fixes: 572c4d862ff2 "softfloat: Convert float32_exp2 to FloatParts"
> > Partially-Resolves:https://gitlab.com/qemu-project/qemu/-/issues/1623
> > Reported-By: Luca Barbato (https://gitlab.com/lu-zero)
> > Signed-off-by: Shivaprasad G Bhat<sbhat@linux.ibm.com>
> > Signed-off-by: Vaibhav Jain<vaibhat@linux.ibm.com>
> > ---
> >   fpu/softfloat.c |    2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
>
> Whoops.  Good catch.

If you are fine with the patch, could you fix the mail id for Vaibhav 
Jain as

 <vaibhav@linux.ibm.com> while pulling ?

If you have other comments, I will fix it in the next version otherwise.


Thanks,

Shivaprasad


H

> r~