Re: [PATCH 08/24] target/sparc: Use tcg_gen_movcond_i64 in gen_edge

[Peter Maydell]

On Tue, 8 Aug 2023 at 04:14, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> The setcond + neg + or sequence is a complex method of
> performing a conditional move.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  target/sparc/translate.c | 17 ++++-------------
>  1 file changed, 4 insertions(+), 13 deletions(-)
>
> diff --git a/target/sparc/translate.c b/target/sparc/translate.c
> index bd877a5e4a..fa80a91161 100644
> --- a/target/sparc/translate.c
> +++ b/target/sparc/translate.c
> @@ -2916,7 +2916,7 @@ static void gen_edge(DisasContext *dc, TCGv dst, TCGv 
> s1, TCGv s2,
>
>      tcg_gen_shr_tl(lo1, tcg_constant_tl(tabl), lo1);
>      tcg_gen_shr_tl(lo2, tcg_constant_tl(tabr), lo2);
> -    tcg_gen_andi_tl(dst, lo1, omask);
> +    tcg_gen_andi_tl(lo1, lo1, omask);
>      tcg_gen_andi_tl(lo2, lo2, omask);
>
>      amask = -8;
> @@ -2926,18 +2926,9 @@ static void gen_edge(DisasContext *dc, TCGv dst, TCGv 
> s1, TCGv s2,
>      tcg_gen_andi_tl(s1, s1, amask);
>      tcg_gen_andi_tl(s2, s2, amask);
>
> -    /* We want to compute
> -        dst = (s1 == s2 ? lo1 : lo1 & lo2).
> -       We've already done dst = lo1, so this reduces to
> -        dst &= (s1 == s2 ? -1 : lo2)
> -       Which we perform by
> -        lo2 |= -(s1 == s2)
> -        dst &= lo2
> -    */
> -    tcg_gen_setcond_tl(TCG_COND_EQ, lo1, s1, s2);
> -    tcg_gen_neg_tl(lo1, lo1);
> -    tcg_gen_or_tl(lo2, lo2, lo1);
> -    tcg_gen_and_tl(dst, dst, lo2);
> +    /* Compute dst = (s1 == s2 ? lo1 : lo1 & lo2). */
> +    tcg_gen_and_tl(lo2, lo2, lo1);
> +    tcg_gen_movcond_tl(TCG_COND_EQ, dst, s1, s2, lo1, lo2);
>  }

I'm glad I didn't have to figure out exactly what this
exciting instruction actually does to review this :-)

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM