[Mesa-dev] [PATCH 2/2] mesa: Speedup the xrgb -> argb special case in fast_read_rgba_pixels_memcpy

[Jose Fonseca]

I'm surprised this is is faster.

In particular, for big things we'll be touching memory twice.

Did you measure the speed up?

Jose

----- Original Message -----
> ---
>  src/mesa/main/readpix.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/src/mesa/main/readpix.c b/src/mesa/main/readpix.c
> index 349b0bc..0f5c84c 100644
> --- a/src/mesa/main/readpix.c
> +++ b/src/mesa/main/readpix.c
> @@ -285,11 +285,12 @@ fast_read_rgba_pixels_memcpy( struct gl_context *ctx,
>        }
>     } else if (copy_xrgb) {
>        /* convert xrgb -> argb */
> +      int alphaOffset = texelBytes - 1;
>        for (j = 0; j < height; j++) {
> -         GLuint *dst4 = (GLuint *) dst, *map4 = (GLuint *) map;
> +         memcpy(dst, map, width * texelBytes);
>           int i;
>           for (i = 0; i < width; i++) {
> -            dst4[i] = map4[i] | 0xff000000;  /* set A=0xff */
> +            dst[i * texelBytes + alphaOffset] = 0xff;  /* set A=0xff */
>           }
>           dst += dstStride;
>           map += stride;
> --
> 1.8.1.5
> 
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