Re: [Qemu-devel] [PATCH 06/26] tcg-aarch64: Special case small constants in tcg_out_movi

[Claudio Fontana <claudio.fontana@huawei.com>]

On 15.03.2014 03:48, Richard Henderson wrote:
> Signed-off-by: Richard Henderson <rth@twiddle.net>
> ---
>  tcg/aarch64/tcg-target.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/tcg/aarch64/tcg-target.c b/tcg/aarch64/tcg-target.c
> index 0f23e43..417f51a 100644
> --- a/tcg/aarch64/tcg-target.c
> +++ b/tcg/aarch64/tcg-target.c
> @@ -577,6 +577,16 @@ static void tcg_out_movi(TCGContext *s, TCGType type, TCGReg rd,
>      }
>      ivalue = ~svalue;
>  
> +    /* Speed things up by handling the common case of small positive
> +       and negative values specially.  */
> +    if ((value & ~0xffffull) == 0) {
> +        tcg_out_insn(s, 3405, MOVZ, type, rd, value, 0);
> +        return;
> +    } else if ((ivalue & ~0xffffull) == 0) {
> +        tcg_out_insn(s, 3405, MOVN, type, rd, ivalue, 0);
> +        return;
> +    }
> +
>      /* Check for bitfield immediates.  For the benefit of 32-bit quantities,
>         use the sign-extended value.  That lets us match rotated values such
>         as 0xff0000ff with the same 64-bit logic matching 0xffffffffff0000ff. */
> 

Reviewed-by: Claudio Fontana <claudio.fontana@huawei.com>