draw: rework handling of non-existing outputs in emit code

Previously the code would just redirect requests for attributes which
don't exist to use output 0. Rework this to output all zeros instead which
seems more useful - in particular some extensions like
ARB_fragment_layer_viewport require 0 in the fs even if it wasn't output by
previous stages. That way, drivers don't have to special case this depending
if the vs/gs outputs some attribute or not.

Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Jose Fonseca <jfonseca@vmware.com>
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>

3 files changed, 46 insertions, 23 deletions

diff --git a/src/gallium/auxiliary/draw/draw_pipe_vbuf.c b/src/gallium/auxiliary/draw/draw_pipe_vbuf.c
index f36706cee01..6df7149b531 100644
--- a/src/gallium/auxiliary/draw/draw_pipe_vbuf.c
+++ b/src/gallium/auxiliary/draw/draw_pipe_vbuf.c
@@ -74,9 +74,10 @@ struct vbuf_stage {
    unsigned max_indices;
    unsigned nr_indices;
 
-   /* Cache point size somewhere it's address won't change:
+   /* Cache point size somewhere its address won't change:
     */
    float point_size;
+   float zero4[4];
 
    struct translate_cache *cache;
 };
@@ -205,6 +206,7 @@ vbuf_start_prim( struct vbuf_stage *vbuf, uint prim )
    struct translate_key hw_key;
    unsigned dst_offset;
    unsigned i;
+   const struct vertex_info *vinfo;
 
    vbuf->render->set_primitive(vbuf->render, prim);
 
@@ -215,27 +217,33 @@ vbuf_start_prim( struct vbuf_stage *vbuf, uint prim )
     * state change.
     */
    vbuf->vinfo = vbuf->render->get_vertex_info(vbuf->render);
-   vbuf->vertex_size = vbuf->vinfo->size * sizeof(float);
+   vinfo = vbuf->vinfo;
+   vbuf->vertex_size = vinfo->size * sizeof(float);
 
    /* Translate from pipeline vertices to hw vertices.
     */
    dst_offset = 0;
 
-   for (i = 0; i < vbuf->vinfo->num_attribs; i++) {
+   for (i = 0; i < vinfo->num_attribs; i++) {
       unsigned emit_sz = 0;
       unsigned src_buffer = 0;
       enum pipe_format output_format;
-      unsigned src_offset = (vbuf->vinfo->attrib[i].src_index * 4 * sizeof(float) );
+      unsigned src_offset = (vinfo->attrib[i].src_index * 4 * sizeof(float) );
 
-      output_format = draw_translate_vinfo_format(vbuf->vinfo->attrib[i].emit);
-      emit_sz = draw_translate_vinfo_size(vbuf->vinfo->attrib[i].emit);
+      output_format = draw_translate_vinfo_format(vinfo->attrib[i].emit);
+      emit_sz = draw_translate_vinfo_size(vinfo->attrib[i].emit);
 
       /* doesn't handle EMIT_OMIT */
       assert(emit_sz != 0);
 
-      if (vbuf->vinfo->attrib[i].emit == EMIT_1F_PSIZE) {
-	 src_buffer = 1;
-	 src_offset = 0;
+      if (vinfo->attrib[i].emit == EMIT_1F_PSIZE) {
+         src_buffer = 1;
+         src_offset = 0;
+      }
+      else if (vinfo->attrib[i].src_index == DRAW_ATTR_NONEXIST) {
+         /* elements which don't exist will get assigned zeros */
+         src_buffer = 2;
+         src_offset = 0;
       }
 
       hw_key.element[i].type = TRANSLATE_ELEMENT_NORMAL;
@@ -249,7 +257,7 @@ vbuf_start_prim( struct vbuf_stage *vbuf, uint prim )
       dst_offset += emit_sz;
    }
 
-   hw_key.nr_elements = vbuf->vinfo->num_attribs;
+   hw_key.nr_elements = vinfo->num_attribs;
    hw_key.output_stride = vbuf->vertex_size;
 
    /* Don't bother with caching at this stage:
@@ -261,6 +269,7 @@ vbuf_start_prim( struct vbuf_stage *vbuf, uint prim )
       vbuf->translate = translate_cache_find(vbuf->cache, &hw_key);
 
       vbuf->translate->set_buffer(vbuf->translate, 1, &vbuf->point_size, 0, ~0);
+      vbuf->translate->set_buffer(vbuf->translate, 2, &vbuf->zero4[0], 0, ~0);
    }
 
    vbuf->point_size = vbuf->stage.draw->rasterizer->point_size;
@@ -428,7 +437,7 @@ struct draw_stage *draw_vbuf_stage( struct draw_context *draw,
    struct vbuf_stage *vbuf = CALLOC_STRUCT(vbuf_stage);
    if (!vbuf)
       goto fail;
-   
+
    vbuf->stage.draw = draw;
    vbuf->stage.name = "vbuf";
    vbuf->stage.point = vbuf_first_point;
@@ -437,29 +446,30 @@ struct draw_stage *draw_vbuf_stage( struct draw_context *draw,
    vbuf->stage.flush = vbuf_flush;
    vbuf->stage.reset_stipple_counter = vbuf_reset_stipple_counter;
    vbuf->stage.destroy = vbuf_destroy;
-   
+
    vbuf->render = render;
    vbuf->max_indices = MIN2(render->max_indices, UNDEFINED_VERTEX_ID-1);
 
-   vbuf->indices = (ushort *) align_malloc( vbuf->max_indices * 
-					    sizeof(vbuf->indices[0]), 
-					    16 );
+   vbuf->indices = (ushort *) align_malloc(vbuf->max_indices *
+                    sizeof(vbuf->indices[0]),
+                    16);
    if (!vbuf->indices)
       goto fail;
 
    vbuf->cache = translate_cache_create();
-   if (!vbuf->cache) 
+   if (!vbuf->cache)
       goto fail;
-      
-   
+
    vbuf->vertices = NULL;
    vbuf->vertex_ptr = vbuf->vertices;
-   
+
+   vbuf->zero4[0] = vbuf->zero4[1] = vbuf->zero4[2] = vbuf->zero4[3] = 0.0f;
+
    return &vbuf->stage;
 
- fail:
+fail:
    if (vbuf)
       vbuf_destroy(&vbuf->stage);
-   
+
    return NULL;
 }
diff --git a/src/gallium/auxiliary/draw/draw_pt_emit.c b/src/gallium/auxiliary/draw/draw_pt_emit.c
index 0b9fab5721c..6fb630b5498 100644
--- a/src/gallium/auxiliary/draw/draw_pt_emit.c
+++ b/src/gallium/auxiliary/draw/draw_pt_emit.c
@@ -44,6 +44,9 @@ struct pt_emit {
    unsigned prim;
 
    const struct vertex_info *vinfo;
+
+   float zero4[4];
+
 };
 
 
@@ -92,6 +95,11 @@ draw_pt_emit_prepare(struct pt_emit *emit,
          src_buffer = 1;
          src_offset = 0;
       }
+      else if (vinfo->attrib[i].src_index == DRAW_ATTR_NONEXIST) {
+         /* elements which don't exist will get assigned zeros */
+         src_buffer = 2;
+         src_offset = 0;
+      }
 
       hw_key.element[i].type = TRANSLATE_ELEMENT_NORMAL;
       hw_key.element[i].input_format = PIPE_FORMAT_R32G32B32A32_FLOAT;
@@ -111,6 +119,8 @@ draw_pt_emit_prepare(struct pt_emit *emit,
        translate_key_compare(&emit->translate->key, &hw_key) != 0) {
       translate_key_sanitize(&hw_key);
       emit->translate = translate_cache_find(emit->cache, &hw_key);
+
+      emit->translate->set_buffer(emit->translate, 2, &emit->zero4[0], 0, ~0);
    }
 
    if (!vinfo->size)
@@ -287,6 +297,8 @@ draw_pt_emit_create(struct draw_context *draw)
       return NULL;
    }
 
+   emit->zero4[0] = emit->zero4[1] = emit->zero4[2] = emit->zero4[3] = 0.0f;
+
    return emit;
 }
 
diff --git a/src/gallium/auxiliary/draw/draw_vertex.h b/src/gallium/auxiliary/draw/draw_vertex.h
index ee11d2f9276..ae207e2b0b3 100644
--- a/src/gallium/auxiliary/draw/draw_vertex.h
+++ b/src/gallium/auxiliary/draw/draw_vertex.h
@@ -44,6 +44,7 @@
 #include "util/u_debug.h"
 #include "util/u_memory.h"
 
+#define DRAW_ATTR_NONEXIST 255
 
 /**
  * Vertex attribute emit modes
@@ -130,9 +131,9 @@ draw_emit_vertex_attr(struct vertex_info *vinfo,
    const uint n = vinfo->num_attribs;
 
    /* If the src_index is negative, meaning it hasn't been found
-    * lets just redirect it to the first output slot */
+    * we'll assign it all zeros later - set to DRAW_ATTR_NONEXIST */
    if (src_index < 0) {
-      src_index = 0;
+      src_index = DRAW_ATTR_NONEXIST;
    }
 
    assert(n < Elements(vinfo->attrib));