Re: [Qemu-devel] [PATCH 00/11] implement 680x0 FPU (part 5)

[Richard Henderson]

On 03/13/2018 04:27 AM, Laurent Vivier wrote:
> I have compared results of these instructions from a real m68040 and from
> QEMU, and they match (sincos differs [1] because in QEMU we compute it as
> sin and cos, and on m68040 sin and cos results differ also with
> sincos results. It looks like a rounding problem, perhaps a bug in m68040
> FPU? or in my test program?)
> 
> I know this will need more work, but for the moment I only would
> like to provide these new instructions to the maintream of QEMU.
> 
> [1] Example:
> 
> sincos -6.125952 -> (0.156586, 0.987664)
> 
> QEMU:
> 
>   sincos c0010000c407cd1182c2bb27 -> 3ffc0000a05812beea449a4d
>                                      3ffe0000fcd791d65887d19a
>   sin c0010000c407cd1182c2bb27    -> 3ffc0000a05812beea449a4d
>   cos c0010000c407cd1182c2bb27    -> 3ffe0000fcd791d65887d19a
> 
> m68040:
> 
>   sincos c0010000c407cd1182c2bb27 -> 3ffc0000a05812beea449a4d
>                                      3ffe0000fcd791d65887d199 <<--
>   sin c0010000c407cd1182c2bb27    -> 3ffc0000a05812beea449a4d
>   cos c0010000c407cd1182c2bb27    -> 3ffe0000fcd791d65887d19a

Wow, this does seem like a processor bug.

Anyway, I've looked through the patch set and nothing stands out,

Reviewed-by: Richard Henderson <address@hidden>


r~