i965/vec4: Allow for dispatch_grf_start_reg to vary.

Both 3DSTATE_VS and 3DSTATE_GS have a dispatch_grf_start_reg control,
which determines the register where the hardware delivers data sourced
from the URB (push constants followed by per-vertex input data).

For vertex shaders, we always set dispatch_grf_start_reg to 1, since
R1 is always the first register available for push constants in vertex
shaders.

For geometry shaders, we'll need the flexibility to set
dispatch_grf_start_reg to different values depending on the behvaiour
of the geometry shader; if it accesses gl_PrimitiveIDIn, we'll need to
set it to 2 to allow the primitive ID to be delivered to the thread in
R1.

This patch eliminates the assumption that dispatch_grf_start_reg is
always 1.  In vec4_visitor, we record the regnum that was passed to
vec4_visitor::setup_uniforms() in prog_data for later use.  In
vec4_generator, we consult this value when converting an abstract
UNIFORM register to a concrete hardware register.  And in the code
that emits 3DSTATE_VS, we set dispatch_grf_start_reg based on the
value recorded in prog_data.

This will allow us to set dispatch_grf_start_reg to the appropriate
value when compiling geometry shaders.  Vertex shaders will continue
to always use a dispatch_grf_start_reg of 1.

v2: Make dispatch_grf_start_reg "unsigned" rather than "GLuint".

Reviewed-by: Ian Romanick <[email protected]>
Reviewed-by: Kenneth Graunke <[email protected]>
Reviewed-by: Matt Turner <[email protected]>

1 files changed, 3 insertions, 1 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_vec4.cpp b/src/mesa/drivers/dri/i965/brw_vec4.cpp
index 36527cd7972..bfef8e0829b 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4.cpp
@@ -1260,6 +1260,8 @@ vec4_vs_visitor::setup_attributes(int payload_reg)
 int
 vec4_visitor::setup_uniforms(int reg)
 {
+   prog_data->dispatch_grf_start_reg = reg;
+
    /* The pre-gen6 VS requires that some push constants get loaded no
     * matter what, or the GPU would hang.
     */
@@ -1280,7 +1282,7 @@ vec4_visitor::setup_uniforms(int reg)
 
    prog_data->nr_params = this->uniforms * 4;
 
-   prog_data->curb_read_length = reg - 1;
+   prog_data->curb_read_length = reg - prog_data->dispatch_grf_start_reg;
 
    return reg;
 }