[Mesa-dev] [PATCH 4/5] draw/so: account for holes in the stream output

[Zack Rusin]

The spec says that the stream output can have holes if the register
index is the maximum possible value, in which case writes to the
buffer should be skipped but everything else should be processed
as usual.

Signed-off-by: Zack Rusin <zackr at vmware.com>
---
 src/gallium/auxiliary/draw/draw_pt_so_emit.c |   15 ++++++++++-----
 src/gallium/include/pipe/p_state.h           |    2 ++
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/src/gallium/auxiliary/draw/draw_pt_so_emit.c b/src/gallium/auxiliary/draw/draw_pt_so_emit.c
index fc69017..563bf65 100644
--- a/src/gallium/auxiliary/draw/draw_pt_so_emit.c
+++ b/src/gallium/auxiliary/draw/draw_pt_so_emit.c
@@ -168,11 +168,16 @@ static void so_emit_prim(struct pt_so_emit *so,
          buffer = (float *)((char *)draw->so.targets[ob]->mapping +
                             draw->so.targets[ob]->target.buffer_offset +
                             draw->so.targets[ob]->internal_offset) + state->output[slot].dst_offset;
-         
-         if (idx == so->pos_idx && pcp_ptr)
-            memcpy(buffer, &pre_clip_pos[start_comp], num_comps * sizeof(float));
-         else
-            memcpy(buffer, &input[idx][start_comp], num_comps * sizeof(float));
+
+         /* the maximum register index simply means that this is
+          * a hole that should be skipped */
+         if (idx != PIPE_MAX_SO_REGISTER_INDEX) {
+            if (idx == so->pos_idx && pcp_ptr) {
+               memcpy(buffer, &pre_clip_pos[start_comp], num_comps * sizeof(float));
+            } else {
+               memcpy(buffer, &input[idx][start_comp], num_comps * sizeof(float));
+            }
+         }
       }
       for (ob = 0; ob < draw->so.num_targets; ++ob) {
          draw->so.targets[ob]->internal_offset += state->stride[ob] * sizeof(float);
diff --git a/src/gallium/include/pipe/p_state.h b/src/gallium/include/pipe/p_state.h
index 5830dff..155bfad 100644
--- a/src/gallium/include/pipe/p_state.h
+++ b/src/gallium/include/pipe/p_state.h
@@ -65,6 +65,7 @@ extern "C" {
 #define PIPE_MAX_TEXTURE_LEVELS   16
 #define PIPE_MAX_SO_BUFFERS        4
 #define PIPE_MAX_SO_OUTPUT_COMPONENT_COUNT 128
+#define PIPE_MAX_SO_REGISTER_INDEX    0xff
 
 
 struct pipe_reference
@@ -194,6 +195,7 @@ struct pipe_stream_output_info
     * Selected components are tightly packed into the output buffer.
     */
    struct {
+      /* Update PIPE_MAX_SO_REGISTER_INDEX when changing the size */
       unsigned register_index:8;  /**< 0 to PIPE_MAX_SHADER_OUTPUTS */
       unsigned start_component:2; /** 0 to 3 */
       unsigned num_components:3;  /** 1 to 4 */
-- 
1.7.10.4