Re: [Qemu-devel] [PATCH v2] target-sh4: add atomic tas

[Paolo Bonzini]

On 03/11/2016 15:07, Laurent Vivier wrote:
> Implement real atomic tas:
> 
>     When (Rn) = 0, 1 -> T
>     Otherwise, 0 -> T
>     In both cases, 1 -> MSB of (Rn)
> 
> using atomic_fetch_or_i32() and setcondi_i32().
> 
> Tested with image from:
> http://wiki.qemu.org/download/sh-test-0.2.tar.bz2
> 
> This image contains a "tas_test" that runs without
> error with this change.
> 
> Signed-off-by: Laurent Vivier <address@hidden>
> ---
> v2:
> - don't use helper but atomic_fetch_or_i32
>   Thank you Paolo!
> 
>  target-sh4/translate.c | 19 ++++++++-----------
>  1 file changed, 8 insertions(+), 11 deletions(-)
> 
> diff --git a/target-sh4/translate.c b/target-sh4/translate.c
> index c89a147..1b83d59 100644
> --- a/target-sh4/translate.c
> +++ b/target-sh4/translate.c
> @@ -1640,18 +1640,15 @@ static void _decode_opc(DisasContext * ctx)
>       tcg_gen_shri_i32(REG(B11_8), REG(B11_8), 16);
>       return;
>      case 0x401b:             /* tas.b @Rn */
> -     {
> -         TCGv addr, val;
> -         addr = tcg_temp_local_new();
> -         tcg_gen_mov_i32(addr, REG(B11_8));
> -         val = tcg_temp_local_new();
> -            tcg_gen_qemu_ld_i32(val, addr, ctx->memidx, MO_UB);
> +        {
> +            TCGv val = tcg_temp_new();
> +            TCGv msb = tcg_const_i32(0x80);
> +            tcg_gen_atomic_fetch_or_i32(val, REG(B11_8), msb,
> +                                        ctx->memidx, MO_UB);
> +            tcg_temp_free(msb);
>              tcg_gen_setcondi_i32(TCG_COND_EQ, cpu_sr_t, val, 0);
> -         tcg_gen_ori_i32(val, val, 0x80);
> -            tcg_gen_qemu_st_i32(val, addr, ctx->memidx, MO_UB);
> -         tcg_temp_free(val);
> -         tcg_temp_free(addr);
> -     }
> +            tcg_temp_free(val);
> +        }
>       return;
>      case 0xf00d: /* fsts FPUL,FRn - FPSCR: Nothing */
>       CHECK_FPU_ENABLED
> 

For 2.8?

Paolo