Re: [Qemu-devel] [PATCH 4/8] tcg: Emit XORI as NOT for appropriate constants

[Aurelien Jarno <aurelien@aurel32.net>]

On Fri, Sep 21, 2012 at 05:18:12PM -0700, Richard Henderson wrote:
> Note that xori_i64 failed to perform even the minimal
> optimizations promised by the README.
> 
> Signed-off-by: Richard Henderson <rth@twiddle.net>
> ---
>  tcg/tcg-op.h | 19 +++++++++++++++----
>  1 file changed, 15 insertions(+), 4 deletions(-)
> 
> diff --git a/tcg/tcg-op.h b/tcg/tcg-op.h
> index fd16499..bcfb60b 100644
> --- a/tcg/tcg-op.h
> +++ b/tcg/tcg-op.h
> @@ -582,9 +582,12 @@ static inline void tcg_gen_xor_i32(TCGv_i32 ret, TCGv_i32 arg1, TCGv_i32 arg2)
>  
>  static inline void tcg_gen_xori_i32(TCGv_i32 ret, TCGv_i32 arg1, int32_t arg2)
>  {
> -    /* some cases can be optimized here */
> +    /* Some cases can be optimized here.  */
>      if (arg2 == 0) {
>          tcg_gen_mov_i32(ret, arg1);
> +    } else if (arg2 == -1 && TCG_TARGET_HAS_not_i32) {
> +        /* Don't recurse with tcg_gen_not_i32.  */
> +        tcg_gen_op2_i32(INDEX_op_not_i32, ret, arg1);
>      } else {
>          TCGv_i32 t0 = tcg_const_i32(arg2);
>          tcg_gen_xor_i32(ret, arg1, t0);
> @@ -1206,9 +1209,17 @@ static inline void tcg_gen_xor_i64(TCGv_i64 ret, TCGv_i64 arg1, TCGv_i64 arg2)
>  
>  static inline void tcg_gen_xori_i64(TCGv_i64 ret, TCGv_i64 arg1, int64_t arg2)
>  {
> -    TCGv_i64 t0 = tcg_const_i64(arg2);
> -    tcg_gen_xor_i64(ret, arg1, t0);
> -    tcg_temp_free_i64(t0);
> +    /* Some cases can be optimized here.  */
> +    if (arg2 == 0) {
> +        tcg_gen_mov_i64(ret, arg1);
> +    } else if (arg2 == -1 && TCG_TARGET_HAS_not_i64) {
> +        /* Don't recurse with tcg_gen_not_i64.  */
> +        tcg_gen_op2_i64(INDEX_op_not_i64, ret, arg1);
> +    } else {
> +        TCGv_i64 t0 = tcg_const_i64(arg2);
> +        tcg_gen_xor_i64(ret, arg1, t0);
> +        tcg_temp_free_i64(t0);
> +    }
>  }
>  
>  static inline void tcg_gen_shl_i64(TCGv_i64 ret, TCGv_i64 arg1, TCGv_i64 arg2)
> -- 
> 1.7.11.4
> 

Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>

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