st/nir: Disable varying packing when doing transform feedback.

The varying packing would result in st_nir_assign_var_locations() picking
new driver_locations, despite the pipe_stream_output already being set up
for the old driver location.  This left the gallium driver with no way to
work back to what varying was referenced by pipe_stream_output.

Fixes these tests on V3D:
dEQP-GLES3.functional.transform_feedback.random.separate.points.3
dEQP-GLES3.functional.transform_feedback.random.separate.points.7
dEQP-GLES3.functional.transform_feedback.random.separate.points.9
dEQP-GLES3.functional.transform_feedback.random.separate.triangles.3
dEQP-GLES3.functional.transform_feedback.random.separate.triangles.8

Reviewed-by: Timothy Arceri <[email protected]>

1 files changed, 9 insertions, 1 deletions

diff --git a/src/mesa/state_tracker/st_glsl_to_nir.cpp b/src/mesa/state_tracker/st_glsl_to_nir.cpp
index fc4bba3fb96..1985fe1d532 100644
--- a/src/mesa/state_tracker/st_glsl_to_nir.cpp
+++ b/src/mesa/state_tracker/st_glsl_to_nir.cpp
@@ -745,7 +745,15 @@ st_link_nir(struct gl_context *ctx,
       shader->Program->info = nir->info;
 
       if (prev != -1) {
-         nir_compact_varyings(shader_program->_LinkedShaders[prev]->Program->nir,
+         struct gl_program *prev_shader =
+            shader_program->_LinkedShaders[prev]->Program;
+
+         /* We can't use nir_compact_varyings with transform feedback, since
+          * the pipe_stream_output->output_register field is based on the
+          * pre-compacted driver_locations.
+          */
+         if (!prev_shader->sh.LinkedTransformFeedback)
+            nir_compact_varyings(shader_program->_LinkedShaders[prev]->Program->nir,
                               nir, ctx->API != API_OPENGL_COMPAT);
       }
       prev = i;