[image] Discard redundant clears

On slow machines the call to pixman_fill_sse2() on similar surfaces that
we know are already zeroed takes a significant amount of time [12.77% of
the profile for a firefox trace, cf to just 3% of the profile is spent
inside memset].

Rather than solve why the pixman_fill_sse2() is so slow, simply skip the
redundant clears.

2 files changed, 35 insertions, 1 deletions

diff --git a/src/cairo-image-surface.c b/src/cairo-image-surface.c
index e7efdca1..627f9edd 100644
--- a/src/cairo-image-surface.c
+++ b/src/cairo-image-surface.c
@@ -172,6 +172,7 @@ _cairo_image_surface_create_for_pixman_image (pixman_image_t		*pixman_image,
     surface->height = pixman_image_get_height (pixman_image);
     surface->stride = pixman_image_get_stride (pixman_image);
     surface->depth = pixman_image_get_depth (pixman_image);
+    surface->is_clear = FALSE;
 
     surface->clip_region = NULL;
 
@@ -358,6 +359,8 @@ _cairo_image_surface_create_with_pixman_format (unsigned char		*data,
 							    pixman_format);
     if (cairo_surface_status (surface))
 	pixman_image_unref (pixman_image);
+    else
+	((cairo_image_surface_t *)surface)->is_clear = TRUE;
 
     return surface;
 }
@@ -1113,6 +1116,8 @@ _cairo_image_surface_composite (cairo_operator_t	 op,
 	_cairo_pattern_release_surface (mask_pattern, &mask->base, &mask_attr);
 
     _cairo_pattern_release_surface (src_pattern, &src->base, &src_attr);
+    if (op != CAIRO_OPERATOR_CLEAR)
+	dst->is_clear = FALSE;
 
     return status;
 }
@@ -1171,6 +1176,9 @@ _cairo_image_surface_fill_rectangles (void		      *abstract_surface,
     if (pixman_rects != stack_rects)
 	free (pixman_rects);
 
+    if (op != CAIRO_OPERATOR_CLEAR)
+	surface->is_clear = FALSE;
+
     return status;
 }
 
@@ -1300,6 +1308,9 @@ _cairo_image_surface_composite_trapezoids (cairo_operator_t	op,
 
     pixman_image_unref (mask);
 
+    if (op != CAIRO_OPERATOR_CLEAR)
+	dst->is_clear = FALSE;
+
     if (! _cairo_operator_bounded_by_mask (op)) {
 	status = _cairo_surface_composite_shape_fixup_unbounded (&dst->base,
 								 &attributes,
@@ -1458,6 +1469,9 @@ _cairo_image_surface_span_renderer_finish (void *abstract_renderer)
 		rects->width, rects->height,
 		dst->clip_region);
 	}
+
+	if (renderer->op != CAIRO_OPERATOR_CLEAR)
+	    dst->is_clear = FALSE;
     }
     if (status != CAIRO_STATUS_SUCCESS)
 	return _cairo_span_renderer_set_error (abstract_renderer,
@@ -1567,6 +1581,25 @@ _cairo_image_surface_get_font_options (void                  *abstract_surface,
     cairo_font_options_set_hint_metrics (options, CAIRO_HINT_METRICS_ON);
 }
 
+static cairo_int_status_t
+_cairo_image_surface_paint (void *abstract_surface,
+			    cairo_operator_t	 op,
+			    const cairo_pattern_t *source,
+			    cairo_clip_t	    *clip)
+{
+    /* we know that surfaces are calloc, so ignore any redundant clears */
+    if (op == CAIRO_OPERATOR_CLEAR && clip == NULL) {
+	cairo_image_surface_t *surface = abstract_surface;
+
+	if (surface->is_clear)
+	    return CAIRO_STATUS_SUCCESS;
+
+	surface->is_clear = TRUE;
+    }
+
+    return CAIRO_INT_STATUS_UNSUPPORTED;
+}
+
 /**
  * _cairo_surface_is_image:
  * @surface: a #cairo_surface_t
@@ -1605,7 +1638,7 @@ const cairo_surface_backend_t _cairo_image_surface_backend = {
     NULL, /* font_fini */
     NULL, /* glyph_fini */
 
-    NULL, /* paint */
+    _cairo_image_surface_paint,
     NULL, /* mask */
     NULL, /* stroke */
     NULL, /* fill */
diff --git a/src/cairoint.h b/src/cairoint.h
index 3cd0cb37..6010e20f 100644
--- a/src/cairoint.h
+++ b/src/cairoint.h
@@ -857,6 +857,7 @@ struct _cairo_image_surface {
     pixman_image_t *pixman_image;
     cairo_region_t *clip_region;
 
+    unsigned is_clear : 1;
     unsigned owns_data : 1;
     unsigned transparency : 2;
 };