Mesa (master): i965: Fix gl_VertexID when there are no other vertex inputs.

[Paul Berry]

Module: Mesa
Branch: master
Commit: 1b37fc40fc1d443e7ab9f930f78af9a32525698a
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=1b37fc40fc1d443e7ab9f930f78af9a32525698a

Author: Paul Berry <stereotype441 at gmail.com>
Date:   Mon Dec 17 09:55:48 2012 -0800

i965: Fix gl_VertexID when there are no other vertex inputs.

brw_emit_vertices contains special case logic to handle the case where
a vertex shader doesn't read any inputs.  This special case logic was
incorrectly activating in the case were the only vertex input is
gl_VertexID.  As a result, if a shader used gl_VertexID but used no
other inputs, then all vertices got a gl_VertexID of zero.

Fixes oglconform test "ubo-usage advanced.transform_feedback".

Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>

---

 src/mesa/drivers/dri/i965/brw_draw_upload.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_draw_upload.c b/src/mesa/drivers/dri/i965/brw_draw_upload.c
index b6ce0bd..515a7a8 100644
--- a/src/mesa/drivers/dri/i965/brw_draw_upload.c
+++ b/src/mesa/drivers/dri/i965/brw_draw_upload.c
@@ -571,6 +571,8 @@ static void brw_emit_vertices(struct brw_context *brw)
 
    brw_emit_query_begin(brw);
 
+   nr_elements = brw->vb.nr_enabled + brw->vs.prog_data->uses_vertexid;
+
    /* If the VS doesn't read any inputs (calculating vertex position from
     * a state variable for some reason, for example), emit a single pad
     * VERTEX_ELEMENT struct and bail.
@@ -578,7 +580,7 @@ static void brw_emit_vertices(struct brw_context *brw)
     * The stale VB state stays in place, but they don't do anything unless
     * a VE loads from them.
     */
-   if (brw->vb.nr_enabled == 0) {
+   if (nr_elements == 0) {
       BEGIN_BATCH(3);
       OUT_BATCH((_3DSTATE_VERTEX_ELEMENTS << 16) | 1);
       if (intel->gen >= 6) {
@@ -642,8 +644,6 @@ static void brw_emit_vertices(struct brw_context *brw)
       ADVANCE_BATCH();
    }
 
-   nr_elements = brw->vb.nr_enabled + brw->vs.prog_data->uses_vertexid;
-
    /* The hardware allows one more VERTEX_ELEMENTS than VERTEX_BUFFERS, presumably
     * for VertexID/InstanceID.
     */