[PATCH 5/7] glamor: Provide a fallback path for using an index buffer to do quads.

[Dave Airlie]

On 20 June 2015 at 12:09, Eric Anholt <eric at anholt.net> wrote:
> Improves x11perf -aa10text performance by 1377.59% +/- 23.8198% (n=93)
> on Intel with GLES2.
>

Do we destroy glamor_priv->ib anywhere?

Other than that, this seems sane, it might be nice to have more structured index
buffer support if we need to use it elsewhere in the future.

but otherwise,
Reviewed-by: Dave Airlie <airlied at redhat.com>
>
> +void
> +glamor_gldrawarrays_quads_using_indices(glamor_screen_private *glamor_priv,
> +                                        unsigned count)
> +{
> +    unsigned i;
> +
> +    /* For a single quad, don't bother with an index buffer. */
> +    if (count ==  1)
> +        goto fallback;
> +
> +    if (glamor_priv->ib_size < count) {
> +        /* Basic GLES2 doesn't have any way to map buffer objects for
> +         * writing, but it's long past time for drivers to have
> +         * MapBufferRange.
> +         */
> +        if (!glamor_priv->has_map_buffer_range)
> +            goto fallback;
> +
> +        /* Lazy create the buffer name, and only bind it once since
> +         * none of the glamor code binds it to anything else.
> +         */
> +        if (!glamor_priv->ib) {
> +            glGenBuffers(1, &glamor_priv->ib);
> +            glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, glamor_priv->ib);
> +        }
> +
> +        /* For now, only support GL_UNSIGNED_SHORTs. */
> +        if (count > ((1 << 16) - 1) / 4) {
> +            goto fallback;
> +        } else {
> +            uint16_t *data;
> +            size_t size = count * 6 * sizeof(GLushort);
> +
> +            glBufferData(GL_ELEMENT_ARRAY_BUFFER, size, NULL, GL_STATIC_DRAW);
> +            data = glMapBufferRange(GL_ELEMENT_ARRAY_BUFFER,
> +                                    0, size,
> +                                    GL_MAP_WRITE_BIT |
> +                                    GL_MAP_INVALIDATE_BUFFER_BIT);
> +            for (i = 0; i < count; i++) {
> +                data[i * 6 + 0] = i * 4 + 0;
> +                data[i * 6 + 1] = i * 4 + 1;
> +                data[i * 6 + 2] = i * 4 + 2;
> +                data[i * 6 + 3] = i * 4 + 0;
> +                data[i * 6 + 4] = i * 4 + 2;
> +                data[i * 6 + 5] = i * 4 + 3;
> +            }
> +            glUnmapBuffer(GL_ELEMENT_ARRAY_BUFFER);
> +
> +            glamor_priv->ib_size = count;
> +            glamor_priv->ib_type = GL_UNSIGNED_SHORT;
> +        }
> +    }
> +
> +    glDrawElements(GL_TRIANGLES, count * 6, glamor_priv->ib_type, NULL);
> +    return;
> +
> +fallback:
> +    for (i = 0; i < count; i++)
> +        glDrawArrays(GL_TRIANGLE_FAN, i * 4, 4);
> +}
> +
> +
>  /**
>   * Creates any pixmaps used internally by glamor, since those can't be
>   * allocated at ScreenInit time.
> diff --git a/glamor/glamor_priv.h b/glamor/glamor_priv.h
> index c80df22..17f8253 100644
> --- a/glamor/glamor_priv.h
> +++ b/glamor/glamor_priv.h
> @@ -261,6 +261,14 @@ typedef struct glamor_screen_private {
>       */
>      char *vb;
>      int vb_stride;
> +
> +    /** Cached index buffer for translating GL_QUADS to triangles. */
> +    GLuint ib;
> +    /** Index buffer type: GL_UNSIGNED_SHORT or GL_UNSIGNED_INT */
> +    GLenum ib_type;
> +    /** Number of quads the index buffer has indices for. */
> +    unsigned ib_size;
> +
>      Bool has_source_coords, has_mask_coords;
>      int render_nr_quads;
>      glamor_composite_shader composite_shader[SHADER_SOURCE_COUNT]
> @@ -643,6 +651,9 @@ glamor_pixmap_fbo *glamor_create_fbo_array(glamor_screen_private *glamor_priv,
>                                             int flag, int block_w, int block_h,
>                                             glamor_pixmap_private *);
>
> +void glamor_gldrawarrays_quads_using_indices(glamor_screen_private *glamor_priv,
> +                                             unsigned count);
> +
>  /* glamor_core.c */
>  void glamor_init_finish_access_shaders(ScreenPtr screen);
>
> diff --git a/glamor/glamor_utils.h b/glamor/glamor_utils.h
> index 0927ffb..73cda9c 100644
> --- a/glamor/glamor_utils.h
> +++ b/glamor/glamor_utils.h
> @@ -1403,9 +1403,7 @@ glamor_glDrawArrays_GL_QUADS(glamor_screen_private *glamor_priv, unsigned count)
>      if (glamor_priv->gl_flavor == GLAMOR_GL_DESKTOP) {
>          glDrawArrays(GL_QUADS, 0, count * 4);
>      } else {
> -        unsigned i;
> -        for (i = 0; i < count; i++)
> -            glDrawArrays(GL_TRIANGLE_FAN, i * 4, 4);
> +        glamor_gldrawarrays_quads_using_indices(glamor_priv, count);
>      }
>  }
>
> --
> 2.1.4
>
> _______________________________________________
> xorg-devel at lists.x.org: X.Org development
> Archives: http://lists.x.org/archives/xorg-devel
> Info: http://lists.x.org/mailman/listinfo/xorg-devel