Re: [Qemu-ppc] [PATCH 14/15] target-ppc: Use tcg_gen_extract_*

[David Gibson]

On Sat, Oct 15, 2016 at 08:37:49PM -0700, Richard Henderson wrote:
> Use the new primitives for RDWINM and RLDICL.
> 
> Cc: address@hidden
> Signed-off-by: Richard Henderson <address@hidden>
> ---
>  target-ppc/translate.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/target-ppc/translate.c b/target-ppc/translate.c
> index bfc1301..724d95c 100644
> --- a/target-ppc/translate.c
> +++ b/target-ppc/translate.c
> @@ -1977,9 +1977,8 @@ static void gen_rlwinm(DisasContext *ctx)
>      if (mb == 0 && me == (31 - sh)) {
>          tcg_gen_shli_tl(t_ra, t_rs, sh);
>          tcg_gen_ext32u_tl(t_ra, t_ra);
> -    } else if (sh != 0 && me == 31 && sh == (32 - mb)) {
> -        tcg_gen_ext32u_tl(t_ra, t_rs);
> -        tcg_gen_shri_tl(t_ra, t_ra, mb);
> +    } else if (me == 31 && (me - mb + 1) + sh <= 32) {

I'm having trouble figuring out what the second part of this condition
is supposed to be checking for, and it seems like it's too
restrictive.

For example, everything except the LSB of a word would be:
        rlwnim rT,rA,31,1,31
which would fail the test, but it should be fine to implement that
with an extract op.

> +        tcg_gen_extract_tl(t_ra, t_rs, sh, me - mb + 1);
>      } else {
>          target_ulong mask;
>  #if defined(TARGET_PPC64)
> @@ -2094,8 +2093,8 @@ static void gen_rldinm(DisasContext *ctx, int mb, int 
> me, int sh)
>  
>      if (sh != 0 && mb == 0 && me == (63 - sh)) {
>          tcg_gen_shli_tl(t_ra, t_rs, sh);
> -    } else if (sh != 0 && me == 63 && sh == (64 - mb)) {
> -        tcg_gen_shri_tl(t_ra, t_rs, mb);
> +    } else if (me == 63 && (me - mb + 1) + sh <= 64) {
> +        tcg_gen_extract_tl(t_ra, t_rs, sh, me - mb + 1);
>      } else {
>          tcg_gen_rotli_tl(t_ra, t_rs, sh);
>          tcg_gen_andi_tl(t_ra, t_ra, MASK(mb, me));

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

signature.asc
Description: PGP signature