Re: [Qemu-devel] [PATCH v2 2/2] target/mips: Make the results of MOD_<U|S>.<B|H|W|D> the same as on hardware

[Aleksandar Markovic]

> From: Mateja Marjanovic <address@hidden>
> Subject: [PATCH v2 2/2] target/mips: Make the results of MOD_<U|S>.<B|H|W|D> 
> the same as on hardware
> 
> From: Mateja Marjanovic <address@hidden>
>
> MSA instructions MOD_<U|S>.<B|H|W|D> when dividing by zero,
> didn't return the same value when executed on a referent hardware
> (FPGA MIPS 64 r6, little endian) and when executed on QEMU, which
> is not a real bug, because the result when dividing by zero is
> UNPREDICTABLE [1] (page 255, 256).
> 
> [1] MIPS Architecture for Programmers
>     Volume IV-j: The MIPS64 SIMD
>     Architecture Module, Revision 1.12
> 
> Signed-off-by: Mateja Marjanovic <address@hidden>
> ---

Reviewed-by: Aleksandar Markovic <address@hidden>

>  target/mips/msa_helper.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/target/mips/msa_helper.c b/target/mips/msa_helper.c
> index 8c77f12..6693ba6 100644
> --- a/target/mips/msa_helper.c
> +++ b/target/mips/msa_helper.c
> @@ -657,14 +657,14 @@ static inline int64_t msa_mod_s_df(uint32_t df, int64_t 
> arg1, int64_t > arg2)
>      if (arg1 == DF_MIN_INT(df) && arg2 == -1) {
>          return 0;
>      }
> -    return arg2 ? arg1 % arg2 : 0;
> +    return arg2 ? arg1 % arg2 : arg1;
>  }
> 
>  static inline int64_t msa_mod_u_df(uint32_t df, int64_t arg1, int64_t arg2)
>  {
>      uint64_t u_arg1 = UNSIGNED(arg1, df);
>      uint64_t u_arg2 = UNSIGNED(arg2, df);
> -    return u_arg2 ? u_arg1 % u_arg2 : 0;
> +    return u_arg2 ? u_arg1 % u_arg2 : u_arg1;
>  }
> 
>  #define SIGNED_EVEN(a, df) \
> --
> 2.7.4