[Mesa-dev] [PATCH 5/9] i965: gl_BaseVertex must be zero for non-indexed draw calls

[Antia Puentes]

- From the OpenGL 4.6 (11.1.3.9 Shader Inputs) specification:

"gl_BaseVertex holds the integer value passed to the baseVertex parameter to the
command that resulted in the current shader invocation. In the case where the
command has no baseVertex parameter, the value of gl_BaseVertex is zero."

- Fixes CTS tests:

* KHR-GL45.shader_draw_parameters_tests.ShaderDrawArraysParameters
* KHR-GL45.shader_draw_parameters_tests.ShaderDrawArraysInstancedParameters
* KHR-GL45.shader_draw_parameters_tests.ShaderMultiDrawArraysParameters
* KHR-GL45.shader_draw_parameters_tests.ShaderMultiDrawArraysIndirectParameters
* KHR-GL45.shader_draw_parameters_tests.MultiDrawArraysIndirectCountParameters

Reviewed-by: Neil Roberts <nroberts at igalia.com>
---
 src/mesa/drivers/dri/i965/brw_draw.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/mesa/drivers/dri/i965/brw_draw.c b/src/mesa/drivers/dri/i965/brw_draw.c
index 8c26273035b..54d35c0522c 100644
--- a/src/mesa/drivers/dri/i965/brw_draw.c
+++ b/src/mesa/drivers/dri/i965/brw_draw.c
@@ -239,6 +239,13 @@ brw_emit_prim(struct brw_context *brw,
                                prim->indirect_offset + 12);
          brw_load_register_mem(brw, GEN7_3DPRIM_START_INSTANCE, bo,
                                prim->indirect_offset + 16);
+
+         if (brw->draw.derived_draw_params_bo != NULL) {
+            brw_store_register_mem32(brw, brw->draw.derived_draw_params_bo,
+                                     GEN7_3DPRIM_BASE_VERTEX,
+                                     brw->draw.derived_draw_params_offset + 4);
+            brw_emit_mi_flush(brw);
+         }
       } else {
          brw_load_register_mem(brw, GEN7_3DPRIM_START_INSTANCE, bo,
                                prim->indirect_offset + 12);
@@ -809,7 +816,7 @@ brw_draw_single_prim(struct gl_context *ctx,
     * valid vs_prog_data, but we always flag BRW_NEW_VERTICES before
     * the loop.
     */
-   const int new_basevertex = prim->indexed ? prim->basevertex : prim->start;
+   const int new_basevertex = prim->indexed ? prim->basevertex : 0;
 
    if (prim_id > 0 &&
        (vs_prog_data->uses_drawid ||
-- 
2.14.1