Re: [PATCH for-5.0, v1] target/mips: Fix loongson multimedia condition instructions

[Philippe Mathieu-Daudé]

Hi Jiaxun Yang,

On 3/24/20 1:22 PM, Jiaxun Yang wrote:
> Loongson multimedia condition instructions were previously implemented as
> write 0 to rd due to lack of documentation. So I just confirmed with Loongson
> about their encoding and implemented them correctly.

If you have a binary using loongson multimedia instructions, can you add 
a test? So this code won't bitrot.

I'm in particular interested by a test covering the MAC2008 
instructions. You can look at examples in the tests/tcg/mips/ directory, 
Aleksandar added a lot of tests there.

Thanks,

Phil.

> Signed-off-by: Jiaxun Yang <address@hidden>
> Acked-by: Huacai Chen <address@hidden>
> ---
> v1: Use deposit opreations according to Richard's suggestion.
> ---
>   target/mips/translate.c | 35 +++++++++++++++++++++++++++++++----
>   1 file changed, 31 insertions(+), 4 deletions(-)
>
> diff --git a/target/mips/translate.c b/target/mips/translate.c
> index d745bd2803..25b595a17d 100644
> --- a/target/mips/translate.c
> +++ b/target/mips/translate.c
> @@ -5529,6 +5529,7 @@ static void gen_loongson_multimedia(DisasContext *ctx, 
> int rd, int rs, int rt)
>   {
>       uint32_t opc, shift_max;
>       TCGv_i64 t0, t1;
> +    TCGCond cond;
>   
>       opc = MASK_LMI(ctx->opcode);
>       switch (opc) {
> @@ -5862,14 +5863,39 @@ static void gen_loongson_multimedia(DisasContext *ctx, 
> int rd, int rs, int rt)
>   
>       case OPC_SEQU_CP2:
>       case OPC_SEQ_CP2:
> +        cond = TCG_COND_EQ;
> +        goto do_cc_cond;
> +        break;
>       case OPC_SLTU_CP2:
> +        cond = TCG_COND_LTU;
> +        goto do_cc_cond;
> +        break;
>       case OPC_SLT_CP2:
> +        cond = TCG_COND_LT;
> +        goto do_cc_cond;
> +        break;
>       case OPC_SLEU_CP2:
> +        cond = TCG_COND_LEU;
> +        goto do_cc_cond;
> +        break;
>       case OPC_SLE_CP2:
> -        /*
> -         * ??? Document is unclear: Set FCC[CC].  Does that mean the
> -         * FD field is the CC field?
> -         */
> +        cond = TCG_COND_LE;
> +    do_cc_cond:
> +        {
> +            int cc = (ctx->opcode >> 8) & 0x7;
> +            TCGv_i64 t64 = tcg_temp_new_i64();
> +            TCGv_i32 t32 = tcg_temp_new_i32();
> +
> +            tcg_gen_setcond_i64(cond, t64, t0, t1);
> +            tcg_gen_extrl_i64_i32(t32, t64);
> +            tcg_gen_deposit_i32(fpu_fcr31, fpu_fcr31, t32,
> +                                get_fp_bit(cc), 1);
> +
> +            tcg_temp_free_i32(t32);
> +            tcg_temp_free_i64(t64);
> +        }
> +        goto no_rd;
> +        break;
>       default:
>           MIPS_INVAL("loongson_cp2");
>           generate_exception_end(ctx, EXCP_RI);
> @@ -5878,6 +5904,7 @@ static void gen_loongson_multimedia(DisasContext *ctx, 
> int rd, int rs, int rt)
>   
>       gen_store_fpr64(ctx, t0, rd);
>   
> +no_rd:
>       tcg_temp_free_i64(t0);
>       tcg_temp_free_i64(t1);
>   }