[Pixman] [PATCH] vmx: implement fast path vmx_composite_over_n_8888

[Oded Gabbay]

On Fri, Sep 4, 2015 at 3:39 PM, Siarhei Siamashka
<siarhei.siamashka at gmail.com> wrote:
> Running "lowlevel-blt-bench over_n_8888" on Playstation3 3.2GHz,
> Gentoo ppc (32-bit userland) gave the following results:
>
> before:  over_n_8888 =  L1: 147.47  L2: 205.86  M:121.07
> after:   over_n_8888 =  L1: 287.27  L2: 261.09  M:133.48
>
> Signed-off-by: Siarhei Siamashka <siarhei.siamashka at gmail.com>
> ---
>  pixman/pixman-vmx.c |   54 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 54 insertions(+), 0 deletions(-)
>
> diff --git a/pixman/pixman-vmx.c b/pixman/pixman-vmx.c
> index a9bd024..9e551b3 100644
> --- a/pixman/pixman-vmx.c
> +++ b/pixman/pixman-vmx.c
> @@ -2745,6 +2745,58 @@ vmx_composite_src_x888_8888 (pixman_implementation_t *imp,
>  }
>
>  static void
> +vmx_composite_over_n_8888 (pixman_implementation_t *imp,
> +                           pixman_composite_info_t *info)
> +{
> +    PIXMAN_COMPOSITE_ARGS (info);
> +    uint32_t *dst_line, *dst;
> +    uint32_t src, ia;
> +    int      i, w, dst_stride;
> +    vector unsigned int vdst, vsrc, via;
> +
> +    src = _pixman_image_get_solid (imp, src_image, dest_image->bits.format);
> +
> +    if (src == 0)
> +       return;
> +
> +    PIXMAN_IMAGE_GET_LINE (
> +       dest_image, dest_x, dest_y, uint32_t, dst_stride, dst_line, 1);
> +
> +    vsrc = (vector unsigned int){src, src, src, src};
> +    via = negate (splat_alpha (vsrc));
If we will use the over function (see my next comment), we need to
remove the negate() from the above statement, as it is done in the
over function.

> +    ia = ALPHA_8 (~src);
> +
> +    while (height--)
> +    {
> +       dst = dst_line;
> +       dst_line += dst_stride;
> +       w = width;
> +
> +       while (w && ((uintptr_t)dst & 15))
> +       {
> +           uint32_t d = *dst;
> +           UN8x4_MUL_UN8_ADD_UN8x4 (d, ia, src);
> +           *dst++ = d;
> +           w--;
> +       }
> +
> +       for (i = w / 4; i > 0; i--)
> +       {
> +           vdst = pix_multiply (load_128_aligned (dst), via);
> +           save_128_aligned (dst, pix_add (vsrc, vdst));

Instead of the above two lines, I would simply use the over function
in vmx, which does exactly that. So:
                vdst = over(vsrc, via, load_128_aligned(dst))
                save_128_aligned (dst, vdst);

I prefer this as it reuses an existing function which helps
maintainability, and using it has no impact on performance.

> +           dst += 4;
> +       }
> +
> +       for (i = w % 4; --i >= 0;)
> +       {
> +           uint32_t d = dst[i];
> +           UN8x4_MUL_UN8_ADD_UN8x4 (d, ia, src);
> +           dst[i] = d;
> +       }
> +    }
> +}
> +
> +static void
>  vmx_composite_over_8888_8888 (pixman_implementation_t *imp,
>                                 pixman_composite_info_t *info)
>  {
> @@ -3079,6 +3131,8 @@ FAST_NEAREST_MAINLOOP (vmx_8888_8888_normal_OVER,
>
>  static const pixman_fast_path_t vmx_fast_paths[] =
>  {
> +    PIXMAN_STD_FAST_PATH (OVER, solid,    null, a8r8g8b8, vmx_composite_over_n_8888),
> +    PIXMAN_STD_FAST_PATH (OVER, solid,    null, x8r8g8b8, vmx_composite_over_n_8888),
>      PIXMAN_STD_FAST_PATH (OVER, a8r8g8b8, null, a8r8g8b8, vmx_composite_over_8888_8888),
>      PIXMAN_STD_FAST_PATH (OVER, a8r8g8b8, null, x8r8g8b8, vmx_composite_over_8888_8888),
>      PIXMAN_STD_FAST_PATH (OVER, a8b8g8r8, null, a8b8g8r8, vmx_composite_over_8888_8888),
> --
> 1.7.8.6
>

Indeed, this implementation is much better than what I did.
Apparently, converting sse2 to vmx calls isn't the optimal way.
On my POWER8 machine, I get:

reference memcpy speed = 24764.8MB/s (6191.2MP/s for 32bpp fills)
L1              572.29          1539.47         +169.00%
L2              1038.08          1549.04         +49.22%
M              1104.1          1522.22         +37.87%
HT              447.45          676.32         +51.15%
VT              520.82          764.82         +46.85%
R              407.92          570.54         +39.87%
RT              148.9          208.77         +40.21%
Kops/s              1100          1418         +28.91%

So, assuming the change above, this patch is:

Reviewed-by: Oded Gabbay <oded.gabbay at gmail.com>