i965: Separate gl_InstanceID and gl_VertexID uploading.

We always uploaded them together, mostly out of laziness - both required
an additional vertex element.  However, gl_VertexID now also requires an
additional vertex buffer for storing gl_BaseVertex; for non-indirect
draws this also means uploading (a small amount of) data.  This is extra
overhead we don't need if the shader only uses gl_InstanceID.

In particular, our clear shaders currently use gl_InstanceID for doing
layered clears, but don't need gl_VertexID.

Signed-off-by: Kenneth Graunke <[email protected]>
Cc: "10.3" <[email protected]>
Reviewed-by: Ian Romanick <[email protected]>
Tested-by: Ian Romanick <[email protected]>

1 files changed, 1 insertions, 0 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_context.h b/src/mesa/drivers/dri/i965/brw_context.h
index 39cb8566b63..5830aa993d5 100644
--- a/src/mesa/drivers/dri/i965/brw_context.h
+++ b/src/mesa/drivers/dri/i965/brw_context.h
@@ -553,6 +553,7 @@ struct brw_vs_prog_data {
    GLbitfield64 inputs_read;
 
    bool uses_vertexid;
+   bool uses_instanceid;
 };