st/xa: scissor to help tilers

Keep track of the maximal bounds of all the operations and set scissor
accordingly.  For tiling GPU's this can be a big win by reducing the
memory bandwidth spent moving pixels from system memory to tile buffer
and back.

You could imagine being more sophisticated and splitting up disjoint
operations.  But this simplistic approach is good enough for the common
cases.

Signed-off-by: Rob Clark <robclark@freedesktop.org>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>

src/gallium/state_trackers/xa/xa_composite.c

@@ -512,6 +512,8 @@ xa_composite_rect(struct xa_context *ctx,
 	const float *src_matrix = NULL;
 	const float *mask_matrix = NULL;
 
+	xa_scissor_update(ctx, dstX, dstY, dstX + width, dstY + height);
+
 	if (comp->src->has_transform)
 	    src_matrix = comp->src->transform;
 	if (comp->mask && comp->mask->has_transform)

src/gallium/state_trackers/xa/xa_context.c

@@ -238,6 +238,8 @@ xa_copy(struct xa_context *ctx,
 {
     struct pipe_box src_box;
 
+    xa_scissor_update(ctx, dx, dy, dx + width, dy + height);
+
     if (ctx->simple_copy) {
 	u_box_2d(sx, sy, width, height, &src_box);
 	ctx->pipe->resource_copy_region(ctx->pipe,
@@ -324,6 +326,7 @@ xa_solid_prepare(struct xa_context *ctx, struct xa_surface *dst,
 XA_EXPORT void
 xa_solid(struct xa_context *ctx, int x, int y, int width, int height)
 {
+    xa_scissor_update(ctx, x, y, x + width, y + height);
     renderer_solid(ctx, x, y, x + width, y + height, ctx->solid_color);
 }
 

src/gallium/state_trackers/xa/xa_priv.h

@@ -38,6 +38,8 @@
 #include "pipe/p_context.h"
 #include "pipe/p_state.h"
 
+#include "util/u_math.h"
+
 #if defined(__GNUC__) && __GNUC__ >= 4
 #define XA_EXPORT __attribute__ ((visibility("default")))
 #else
@@ -105,6 +107,12 @@ struct xa_context {
     struct xa_surface *dst;
     struct pipe_surface *srf;
 
+    /* destination scissor state.. we scissor out untouched parts
+     * of the dst for the benefit of tilers:
+     */
+    struct pipe_scissor_state scissor;
+    int scissor_valid;
+
     int simple_copy;
 
     int has_solid_color;
@@ -115,6 +123,27 @@ struct xa_context {
     const struct xa_composite *comp;
 };
 
+static INLINE void
+xa_scissor_reset(struct xa_context *ctx)
+{
+    ctx->scissor.maxx = 0;
+    ctx->scissor.maxy = 0;
+    ctx->scissor.minx = ~0;
+    ctx->scissor.miny = ~0;
+    ctx->scissor_valid = FALSE;
+}
+
+static INLINE void
+xa_scissor_update(struct xa_context *ctx, unsigned minx, unsigned miny,
+		unsigned maxx, unsigned maxy)
+{
+    ctx->scissor.maxx = MAX2(ctx->scissor.maxx, maxx);
+    ctx->scissor.maxy = MAX2(ctx->scissor.maxy, maxy);
+    ctx->scissor.minx = MIN2(ctx->scissor.minx, minx);
+    ctx->scissor.miny = MIN2(ctx->scissor.miny, miny);
+    ctx->scissor_valid = TRUE;
+}
+
 enum xa_vs_traits {
     VS_COMPOSITE = 1 << 0,
     VS_MASK = 1 << 1,

src/gallium/state_trackers/xa/xa_renderer.c

@@ -79,11 +79,22 @@ renderer_draw(struct xa_context *r)
     if (!r->buffer_size)
 	return;
 
+    if (!r->scissor_valid) {
+	r->scissor.minx = 0;
+	r->scissor.miny = 0;
+	r->scissor.maxx = r->dst->tex->width0;
+	r->scissor.maxy = r->dst->tex->height0;
+    }
+
+    r->pipe->set_scissor_states(r->pipe, 0, 1, &r->scissor);
+
     cso_set_vertex_elements(r->cso, r->attrs_per_vertex, r->velems);
     util_draw_user_vertex_buffer(r->cso, r->buffer, PIPE_PRIM_QUADS,
                                  num_verts,	/* verts */
                                  r->attrs_per_vertex);	/* attribs/vert */
     r->buffer_size = 0;
+
+    xa_scissor_reset(r);
 }
 
 static INLINE void
@@ -111,6 +122,7 @@ renderer_init_state(struct xa_context *r)
     raster.half_pixel_center = 1;
     raster.bottom_edge_rule = 1;
     raster.depth_clip = 1;
+    raster.scissor = 1;
     cso_set_rasterizer(r->cso, &raster);
 
     /* vertex elements state */
@@ -333,6 +345,8 @@ renderer_bind_destination(struct xa_context *r,
     struct pipe_framebuffer_state fb;
     struct pipe_viewport_state viewport;
 
+    xa_scissor_reset(r);
+
     /* Framebuffer uses actual surface width/height
      */
     memset(&fb, 0, sizeof fb);