Re: [Qemu-arm] [PATCH v4 3/9] softfloat: For Mips only, correct order in pickNaNMulAdd()

[Leon Alrae <leon.alrae@imgtec.com>]

On 12/04/16 13:58, Aleksandar Markovic wrote:
> From: Aleksandar Markovic <aleksandar.markovic@imgtec.com>
> 
> Only for Mips platform, and only for cases when snan_bit_is_one is 0,
> correct the order of argument comparisons in pickNaNMulAdd().
> 
> For more info, see [2], page 53, section "3.5.3 NaN Propagation".
> 
> [1] "MIPS® Architecture For Programmers Volume II-A:
>     The MIPS64® Instruction Set Reference Manual",
>     Imagination Technologies LTD, Revision 6.04, November 13, 2015
> 
> [2] "MIPS Architecture for Programmers Volume IV-j:
>     The MIPS32® SIMD Architecture Module",
>     Imagination Technologies LTD, Revision 1.12, February 3, 2016
> 
> Signed-off-by: Aleksandar Markovic <aleksandar.markovic@imgtec.com>
> ---
>  fpu/softfloat-specialize.h |   41 +++++++++++++++++++++++++++++------------
>  1 file changed, 29 insertions(+), 12 deletions(-)
> 
> diff --git a/fpu/softfloat-specialize.h b/fpu/softfloat-specialize.h
> index 169246e..807ecc0 100644
> --- a/fpu/softfloat-specialize.h
> +++ b/fpu/softfloat-specialize.h
> @@ -569,19 +569,36 @@ static int pickNaNMulAdd(flag aIsQNaN, flag aIsSNaN, flag bIsQNaN, flag bIsSNaN,
>          return 3;
>      }
>  
> -    /* Prefer sNaN over qNaN, in the c, a, b order. */
> -    if (cIsSNaN) {
> -        return 2;
> -    } else if (aIsSNaN) {
> -        return 0;
> -    } else if (bIsSNaN) {
> -        return 1;
> -    } else if (cIsQNaN) {
> -        return 2;
> -    } else if (aIsQNaN) {
> -        return 0;

Initially I was confused with this part of diff until I realized that
you had modified the original order in pickNaNMulAdd in patch #1 -- was
that intended?

Otherwise:

Reviewed-by: Leon Alrae <leon.alrae@imgtec.com>

> +    if (status->snan_bit_is_one) {
> +        /* Prefer sNaN over qNaN, in the a, b, c order. */
> +        if (aIsSNaN) {
> +            return 0;
> +        } else if (bIsSNaN) {
> +            return 1;
> +        } else if (cIsSNaN) {
> +            return 2;
> +        } else if (aIsQNaN) {
> +            return 0;
> +        } else if (bIsQNaN) {
> +            return 1;
> +        } else {
> +            return 2;
> +        }
>      } else {
> -        return 1;
> +        /* Prefer sNaN over qNaN, in the c, a, b order. */
> +        if (cIsSNaN) {
> +            return 2;
> +        } else if (aIsSNaN) {
> +            return 0;
> +        } else if (bIsSNaN) {
> +            return 1;
> +        } else if (cIsQNaN) {
> +            return 2;
> +        } else if (aIsQNaN) {
> +            return 0;
> +        } else {
> +            return 1;
> +        }
>      }
>  }
>  #elif defined(TARGET_PPC)
>