Re: [Qemu-devel] [PATCH] tcg: Improve tcg_gen_muli_i32/i64

[Philippe Mathieu-Daudé]

On 02/11/2018 05:39 PM, Richard Henderson wrote:
> Convert multiplication by power of two to left shift.
> 
> Signed-off-by: Richard Henderson <address@hidden>

Reviewed-by: Philippe Mathieu-Daudé <address@hidden>

> ---
>  tcg/tcg-op.c | 24 ++++++++++++++++++------
>  1 file changed, 18 insertions(+), 6 deletions(-)
> 
> diff --git a/tcg/tcg-op.c b/tcg/tcg-op.c
> index 3467787323..34b96d68f3 100644
> --- a/tcg/tcg-op.c
> +++ b/tcg/tcg-op.c
> @@ -277,9 +277,15 @@ void tcg_gen_setcondi_i32(TCGCond cond, TCGv_i32 ret,
>  
>  void tcg_gen_muli_i32(TCGv_i32 ret, TCGv_i32 arg1, int32_t arg2)
>  {
> -    TCGv_i32 t0 = tcg_const_i32(arg2);
> -    tcg_gen_mul_i32(ret, arg1, t0);
> -    tcg_temp_free_i32(t0);
> +    if (arg2 == 0) {
> +        tcg_gen_movi_i32(ret, 0);
> +    } else if (is_power_of_2(arg2)) {
> +        tcg_gen_shli_i32(ret, arg1, ctz32(arg2));
> +    } else {
> +        TCGv_i32 t0 = tcg_const_i32(arg2);
> +        tcg_gen_mul_i32(ret, arg1, t0);
> +        tcg_temp_free_i32(t0);
> +    }
>  }
>  
>  void tcg_gen_div_i32(TCGv_i32 ret, TCGv_i32 arg1, TCGv_i32 arg2)
> @@ -1430,9 +1436,15 @@ void tcg_gen_setcondi_i64(TCGCond cond, TCGv_i64 ret,
>  
>  void tcg_gen_muli_i64(TCGv_i64 ret, TCGv_i64 arg1, int64_t arg2)
>  {
> -    TCGv_i64 t0 = tcg_const_i64(arg2);
> -    tcg_gen_mul_i64(ret, arg1, t0);
> -    tcg_temp_free_i64(t0);
> +    if (arg2 == 0) {
> +        tcg_gen_movi_i64(ret, 0);
> +    } else if (is_power_of_2(arg2)) {
> +        tcg_gen_shli_i64(ret, arg1, ctz64(arg2));
> +    } else {
> +        TCGv_i64 t0 = tcg_const_i64(arg2);
> +        tcg_gen_mul_i64(ret, arg1, t0);
> +        tcg_temp_free_i64(t0);
> +    }
>  }
>  
>  void tcg_gen_div_i64(TCGv_i64 ret, TCGv_i64 arg1, TCGv_i64 arg2)
>