draw: clean up d3d style point clipping

Instead of skipping x/y clipping completely if there's point_tri_clip points
use guard band clipping. This should be easier (previously we could not disable
generating the x/y bits in the clip mask for llvm path, hence requiring custom
clip path), and it also allows us to enable this for tris-as-points more easily
too (this would require custom tri clip filtering too otherwise). Moreover,
some unexpected things could have happen if there's a NaN or just a huge number
in some tri-turned-point, as the driver's rasterizer would need to deal with it
and that might well lead to undefined behavior in typical rasterizers (which
need to convert these numbers to fixed point). Using a guardband should hence
be more robust, while "usually" guaranteeing the same results. (Only "usually"
because unlike hw guardbands draw guardband is always just twice the vp size,
hence small vp but large points could still lead to different results.)
Unfortunately because the clipmask generated is completely unaffected by guard
band clipping, we still need a custom clip stage for points (but not for tris,
as the actual clipping there takes guard band into account).

Reviewed-by: Jose Fonseca <[email protected]>

5 files changed, 42 insertions, 25 deletions

diff --git a/src/gallium/auxiliary/draw/draw_context.c b/src/gallium/auxiliary/draw/draw_context.c
index baebc16036c..da1e958900c 100644
--- a/src/gallium/auxiliary/draw/draw_context.c
+++ b/src/gallium/auxiliary/draw/draw_context.c
@@ -262,10 +262,10 @@ static void update_clip_flags( struct draw_context *draw )
                    draw->rasterizer && draw->rasterizer->depth_clip);
    draw->clip_user = draw->rasterizer &&
                      draw->rasterizer->clip_plane_enable != 0;
-   draw->clip_points_xy = draw->clip_xy &&
-                          (!draw->driver.bypass_clip_points ||
-                          (draw->rasterizer &&
-                          !draw->rasterizer->point_tri_clip));
+   draw->guard_band_points_xy = draw->guard_band_xy ||
+                                (draw->driver.bypass_clip_points &&
+                                (draw->rasterizer &&
+                                 draw->rasterizer->point_tri_clip));
 }
 
 /**
diff --git a/src/gallium/auxiliary/draw/draw_pipe_clip.c b/src/gallium/auxiliary/draw/draw_pipe_clip.c
index b0794583e96..8bdb882218b 100644
--- a/src/gallium/auxiliary/draw/draw_pipe_clip.c
+++ b/src/gallium/auxiliary/draw/draw_pipe_clip.c
@@ -615,19 +615,33 @@ clip_point( struct draw_stage *stage,
       stage->next->point( stage->next, header );
 }
 
+
 /*
  * Clip points but ignore the first 4 (xy) clip planes.
- * (This is necessary because we don't generate a different shader variant
- * just for points hence xy clip bits are still generated. This is not really
- * optimal because of the extra calculations both in generating clip masks
- * and executing the clip stage but it gets the job done.)
+ * (Because the generated clip mask is completely unaffacted by guard band,
+ * we still need to manually evaluate the x/y planes if they are outside
+ * the guard band and not just outside the vp.)
  */
 static void
-clip_point_no_xy( struct draw_stage *stage,
-                  struct prim_header *header )
+clip_point_guard_xy( struct draw_stage *stage,
+                     struct prim_header *header )
 {
-   if ((header->v[0]->clipmask & 0xfffffff0) == 0)
-      stage->next->point( stage->next, header );
+   unsigned clipmask = header->v[0]->clipmask;
+   if ((clipmask & 0xffffffff) == 0)
+      stage->next->point(stage->next, header);
+   else if ((clipmask & 0xfffffff0) == 0) {
+      while (clipmask) {
+         const unsigned plane_idx = ffs(clipmask)-1;
+         clipmask &= ~(1 << plane_idx);  /* turn off this plane's bit */
+         /* TODO: this should really do proper guardband clipping,
+          * currently just throw out infs/nans.
+          */
+         if (util_is_inf_or_nan(header->v[0]->clip[0]) ||
+             util_is_inf_or_nan(header->v[0]->clip[1]))
+            return;
+      }
+      stage->next->point(stage->next, header);
+   }
 }
 
 
@@ -636,7 +650,7 @@ static void
 clip_first_point( struct draw_stage *stage,
                   struct prim_header *header )
 {
-   stage->point = stage->draw->clip_points_xy ? clip_point : clip_point_no_xy;
+   stage->point = stage->draw->guard_band_points_xy ? clip_point_guard_xy : clip_point;
    stage->point(stage, header);
 }
 
@@ -662,7 +676,7 @@ clip_line( struct draw_stage *stage,
 
 static void
 clip_tri( struct draw_stage *stage,
-	  struct prim_header *header )
+          struct prim_header *header )
 {
    unsigned clipmask = (header->v[0]->clipmask | 
                         header->v[1]->clipmask | 
diff --git a/src/gallium/auxiliary/draw/draw_private.h b/src/gallium/auxiliary/draw/draw_private.h
index bbc22dc091e..801d0090908 100644
--- a/src/gallium/auxiliary/draw/draw_private.h
+++ b/src/gallium/auxiliary/draw/draw_private.h
@@ -232,7 +232,7 @@ struct draw_context
    boolean clip_z;
    boolean clip_user;
    boolean guard_band_xy;
-   boolean clip_points_xy;
+   boolean guard_band_points_xy;
 
    boolean force_passthrough; /**< never clip or shade */
 
diff --git a/src/gallium/auxiliary/draw/draw_pt_fetch_shade_pipeline.c b/src/gallium/auxiliary/draw/draw_pt_fetch_shade_pipeline.c
index 2a2e13b8458..a3dc8bed6fc 100644
--- a/src/gallium/auxiliary/draw/draw_pt_fetch_shade_pipeline.c
+++ b/src/gallium/auxiliary/draw/draw_pt_fetch_shade_pipeline.c
@@ -60,7 +60,7 @@ struct fetch_pipeline_middle_end {
  */
 static void fetch_pipeline_prepare( struct draw_pt_middle_end *middle,
                                     unsigned prim,
-				    unsigned opt,
+                                    unsigned opt,
                                     unsigned *max_vertices )
 {
    struct fetch_pipeline_middle_end *fpme = (struct fetch_pipeline_middle_end *)middle;
@@ -72,8 +72,10 @@ static void fetch_pipeline_prepare( struct draw_pt_middle_end *middle,
 
    const unsigned gs_out_prim = (gs ? gs->output_primitive :
                                  u_assembled_prim(prim));
-   unsigned nr = MAX2( vs->info.num_inputs,
-		       draw_total_vs_outputs(draw) );
+   unsigned nr = MAX2(vs->info.num_inputs,
+                      draw_total_vs_outputs(draw));
+   unsigned point_clip = draw->rasterizer->fill_front == PIPE_POLYGON_MODE_POINT ||
+                         gs_out_prim == PIPE_PRIM_POINTS;
 
    if (gs) {
       nr = MAX2(nr, gs->info.num_outputs + 1);
@@ -97,18 +99,17 @@ static void fetch_pipeline_prepare( struct draw_pt_middle_end *middle,
     */
    fpme->vertex_size = sizeof(struct vertex_header) + nr * 4 * sizeof(float);
 
-   
 
    draw_pt_fetch_prepare( fpme->fetch, 
                           vs->info.num_inputs,
                           fpme->vertex_size,
                           instance_id_index );
    draw_pt_post_vs_prepare( fpme->post_vs,
-                            gs_out_prim == PIPE_PRIM_POINTS ?
-                                           draw->clip_points_xy : draw->clip_xy,
+                            draw->clip_xy,
                             draw->clip_z,
                             draw->clip_user,
-                            draw->guard_band_xy,
+                            point_clip ? draw->guard_band_points_xy :
+                                         draw->guard_band_xy,
                             draw->identity_viewport,
                             draw->rasterizer->clip_halfz,
                             (draw->vs.edgeflag_output ? TRUE : FALSE) );
diff --git a/src/gallium/auxiliary/draw/draw_pt_fetch_shade_pipeline_llvm.c b/src/gallium/auxiliary/draw/draw_pt_fetch_shade_pipeline_llvm.c
index 4789cda931f..65cb26dadb5 100644
--- a/src/gallium/auxiliary/draw/draw_pt_fetch_shade_pipeline_llvm.c
+++ b/src/gallium/auxiliary/draw/draw_pt_fetch_shade_pipeline_llvm.c
@@ -143,6 +143,8 @@ llvm_middle_end_prepare( struct draw_pt_middle_end *middle,
       u_assembled_prim(in_prim);
    const unsigned nr = MAX2(vs->info.num_inputs,
                             draw_total_vs_outputs(draw));
+   unsigned point_clip = draw->rasterizer->fill_front == PIPE_POLYGON_MODE_POINT ||
+                         out_prim == PIPE_PRIM_POINTS;
 
    fpme->input_prim = in_prim;
    fpme->opt = opt;
@@ -155,11 +157,11 @@ llvm_middle_end_prepare( struct draw_pt_middle_end *middle,
 
 
    draw_pt_post_vs_prepare( fpme->post_vs,
-                            out_prim == PIPE_PRIM_POINTS ?
-                                        draw->clip_points_xy : draw->clip_xy,
+                            draw->clip_xy,
                             draw->clip_z,
                             draw->clip_user,
-                            draw->guard_band_xy,
+                            point_clip ? draw->guard_band_points_xy :
+                                         draw->guard_band_xy,
                             draw->identity_viewport,
                             draw->rasterizer->clip_halfz,
                             (draw->vs.edgeflag_output ? TRUE : FALSE) );