Re: fpu/softfloat: a question on BFloat 16 support on QEMU

[LIU Zhiwei]

On 2020/6/8 23:50, Alex Bennée wrote:

> LIU Zhiwei <zhiwei_liu@c-sky.com> writes:
>
> > Hi Richard,
> >
> > I am doing bfloat16 support on QEMU.
> >
> > Once I tried to reuse float32 interface, but I couldn't properly process 
> > rounding in some insns like fadd.
> >       
> What do you mean by re-use the float32 interface? Isn't bfloat16 going
> to be pretty much the same as float16 but with some slightly different
> float parameters for the different encoding?
>
> Like the float16 code it won't have to deal with any of the hardfloat
> wrappers so it should look pretty similar.
>
> > What's your opinion about it? Should I expand the fpu/softfloat?
> >       
> bfloat16 is certainly going to become more common that we should have
> common softfloat code to handle it. It would be nice is TestFloat could
> exercise it as well.
>     
    Hi Alex,
    
    I have add the bfloat16 interfaces in QEMU softfloat.  Now I moved
    forward to test the bfloat16 interfaces.
    
    When I looked into the fp-test.c and the berkeley-testfloat-3, I
    found it's some difficult to add bfloat16 interfaces test cases.
    
    There are no corresponding bfloat16 slow_X interlaces in
    slowfloat.c. Nor there is bfloat16 test_X interfaces in
    berkeley-testfloat-3.
     
case F16_MULADD:
 test_abcz_f16(slow_f16_mulAdd, qemu_f16_mulAdd);
 break;
    
    If I want to test bfloat16 interfaces, could you give some advice?
    Should I need to modify berkeley-testfloat-3 to support the bfloat16
    test.
    
    Best Regards, 
    Zhiwei
    
> > Best Regards,
> > Zhiwei
> >       
>
>