Re: [Qemu-devel] [PATCH] target-arm: Set carry flag correctly for Thumb2 ORNS

[Aurelien Jarno]

On Wed, Mar 02, 2011 at 05:34:08PM +0000, Peter Maydell wrote:
> The code for Thumb2 ORNS (or negated and set flags) was trashing
> a TCG input register which was needed later for use in calculating
> flags, with the effect that the carry flag was always set with
> the wrong sense. Fix this by using a TCG temporary instead.
> 
> Signed-off-by: Peter Maydell <address@hidden>
> ---
>  target-arm/translate.c |   11 +++++++++--
>  1 files changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/target-arm/translate.c b/target-arm/translate.c
> index dbd958b..8f4e16b 100644
> --- a/target-arm/translate.c
> +++ b/target-arm/translate.c
> @@ -7326,10 +7326,17 @@ gen_thumb2_data_op(DisasContext *s, int op, int 
> conds, uint32_t shifter_out, TCG
>          logic_cc = conds;
>          break;
>      case 3: /* orn */
> -        tcg_gen_not_i32(t1, t1);
> -        tcg_gen_or_i32(t0, t0, t1);
> +    {
> +        /* We can't just invert t1 in place because we might need it
> +         * to calculate the carry flag later.
> +         */
> +        TCGv tmp = tcg_temp_new_i32();
> +        tcg_gen_not_i32(tmp, t1);
> +        tcg_gen_or_i32(t0, t0, tmp);
> +        tcg_temp_free_i32(tmp);

You may want to use tcg_gen_orc_i32() instead, which as a bonus might be
implemented directly on some hosts (currently ia64, powerpc and sparc).

>          logic_cc = conds;
>          break;
> +    }
>      case 4: /* eor */
>          tcg_gen_xor_i32(t0, t0, t1);
>          logic_cc = conds;
> -- 
> 1.7.1
> 
> 
> 

-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
address@hidden                 http://www.aurel32.net