Re: [PATCH 5/5] target/loongarch: div if x/0 set dividend to 0

[Qi Hu]

On 2022/9/17 15:59, Song Gao wrote:
> div.d, div.du, div,w, div.wu, the LoongArch host if x/0  the result is 0.

The message has a typo: "div,w" => "div.w"

Also I don't know why we need to do this, since the manual say: "When 
the divisor is 0, the result can be any value".

> So we set the divisor to 1 and the dividend to 0.
>
> Signed-off-by: Song Gao <gaosong@loongson.cn>
> ---
>   target/loongarch/insn_trans/trans_arith.c.inc | 34 +++++++++++++++----
>   1 file changed, 27 insertions(+), 7 deletions(-)
>
> diff --git a/target/loongarch/insn_trans/trans_arith.c.inc 
> b/target/loongarch/insn_trans/trans_arith.c.inc
> index 8e45eadbc8..c97afb16f9 100644
> --- a/target/loongarch/insn_trans/trans_arith.c.inc
> +++ b/target/loongarch/insn_trans/trans_arith.c.inc
> @@ -147,12 +147,28 @@ static void prep_divisor_du(TCGv ret, TCGv src2)
>       tcg_gen_movcond_tl(TCG_COND_EQ, ret, src2, zero, one, src2);
>   }
>   
> +static void prep_div(TCGv divisor, TCGv dividend, TCGv src1, TCGv src2)
> +{
> +    TCGv zero = tcg_constant_tl(0);
> +    TCGv one = tcg_constant_tl(1);
> +
> +    /*
> +     * If x / 0, set the diviend to 0 set the divisor to 1
> +     * this is the same with LoongArch host.
> +     */
> +    tcg_gen_movcond_tl(TCG_COND_EQ, dividend, src2, zero, zero, src1);
> +    tcg_gen_movcond_tl(TCG_COND_EQ, divisor, src2, zero, one, src2);
> +}
> +
>   static void gen_div_d(TCGv dest, TCGv src1, TCGv src2)
>   {
>       TCGv t0 = tcg_temp_new();
> -    prep_divisor_d(t0, src1, src2);
> -    tcg_gen_div_tl(dest, src1, t0);
> +    TCGv t1 = tcg_temp_new();
> +
> +    prep_div(t0, t1, src1, src2);
> +    tcg_gen_div_tl(dest, t1, t0);
>       tcg_temp_free(t0);
> +    tcg_temp_free(t1);
>   }
>   
>   static void gen_rem_d(TCGv dest, TCGv src1, TCGv src2)
> @@ -166,9 +182,11 @@ static void gen_rem_d(TCGv dest, TCGv src1, TCGv src2)
>   static void gen_div_du(TCGv dest, TCGv src1, TCGv src2)
>   {
>       TCGv t0 = tcg_temp_new();
> -    prep_divisor_du(t0, src2);
> -    tcg_gen_divu_tl(dest, src1, t0);
> +    TCGv t1 = tcg_temp_new();
> +    prep_div(t0, t1, src1, src2);
> +    tcg_gen_divu_tl(dest, t1, t0);
>       tcg_temp_free(t0);
> +    tcg_temp_free(t1);
>   }
>   
>   static void gen_rem_du(TCGv dest, TCGv src1, TCGv src2)
> @@ -182,10 +200,12 @@ static void gen_rem_du(TCGv dest, TCGv src1, TCGv src2)
>   static void gen_div_w(TCGv dest, TCGv src1, TCGv src2)
>   {
>       TCGv t0 = tcg_temp_new();
> -    /* We need not check for integer overflow for div_w. */
> -    prep_divisor_du(t0, src2);
> -    tcg_gen_div_tl(dest, src1, t0);
> +    TCGv t1 = tcg_temp_new();
> +
> +    prep_div(t0, t1, src1, src2);
> +    tcg_gen_div_tl(dest, t1, t0);
>       tcg_temp_free(t0);
> +    tcg_temp_free(t1);
>   }
>   
>   static void gen_rem_w(TCGv dest, TCGv src1, TCGv src2)