Re: [Qemu-devel] [PATCH v4 59/69] target/arm: Convert T16, nop hints

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 9/4/19 9:30 PM, Richard Henderson wrote:
> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  target/arm/translate.c |  3 +--
>  target/arm/t16.decode  | 17 +++++++++++++++++
>  2 files changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/target/arm/translate.c b/target/arm/translate.c
> index b70491d39e..69092c12c3 100644
> --- a/target/arm/translate.c
> +++ b/target/arm/translate.c
> @@ -10891,8 +10891,7 @@ static void disas_thumb_insn(DisasContext *s, uint32_t insn)
>  
>          case 15: /* IT, nop-hint.  */
>              if ((insn & 0xf) == 0) {
> -                gen_nop_hint(s, (insn >> 4) & 0xf);
> -                break;
> +                goto illegal_op; /* nop hint, in decodetree */
>              }
>              /*
>               * IT (If-Then)
> diff --git a/target/arm/t16.decode b/target/arm/t16.decode
> index 19a442b894..5829b9a58c 100644
> --- a/target/arm/t16.decode
> +++ b/target/arm/t16.decode
> @@ -19,6 +19,7 @@
>  # This file is processed by scripts/decodetree.py
>  #
>  
> +&empty           !extern
>  &s_rrr_shi       !extern s rd rn rm shim shty
>  &s_rrr_shr       !extern s rn rd rm rs shty
>  &s_rri_rot       !extern s rn rd imm rot
> @@ -204,3 +205,19 @@ SETEND          1011 0110 010 1 E:1 000         &setend
>  REV             1011 1010 00 ... ...            @rdm
>  REV16           1011 1010 01 ... ...            @rdm
>  REVSH           1011 1010 11 ... ...            @rdm
> +
> +# Hints
> +
> +{
> +  YIELD         1011 1111 0001 0000
> +  WFE           1011 1111 0010 0000
> +  WFI           1011 1111 0011 0000
> +
> +  # TODO: Implement SEV, SEVL; may help SMP performance.
> +  # SEV         1011 1111 0100 0000
> +  # SEVL        1011 1111 0101 0000
> +
> +  # The canonical nop has the second nibble as 0000, but the whole of the
> +  # rest of the space is a reserved hint, behaves as nop.
> +  NOP           1011 1111 ---- 0000
> +}
> 

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>