[Mesa-dev] [PATCH 16/28] glsl: don't pack tessellation stages like we do other stages

[Timothy Arceri]

Tessellation shaders treat varyings as shared memory and invocations
can access each others varyings therefore we can't use the existing
method to lower them.

This adds a check for these stages as following patches will
allow explicit locations to be lowered even when the driver and existing
tesselation checks ask for it to be disabled, we do this to enable support
for the component layout qualifier.
---
 src/glsl/lower_packed_varyings.cpp | 62 +++++++++++++++++++++-----------------
 1 file changed, 34 insertions(+), 28 deletions(-)

diff --git a/src/glsl/lower_packed_varyings.cpp b/src/glsl/lower_packed_varyings.cpp
index 2899846..e4e9a35 100644
--- a/src/glsl/lower_packed_varyings.cpp
+++ b/src/glsl/lower_packed_varyings.cpp
@@ -737,40 +737,46 @@ lower_packed_varyings(void *mem_ctx, unsigned locations_used,
                       ir_variable_mode mode, unsigned gs_input_vertices,
                       gl_shader *shader, bool disable_varying_packing)
 {
-   exec_list *instructions = shader->ir;
    ir_function *main_func = shader->symbols->get_function("main");
    exec_list void_parameters;
    ir_function_signature *main_func_sig
       = main_func->matching_signature(NULL, &void_parameters, false);
-   exec_list new_instructions, new_variables;
-   lower_packed_varyings_visitor visitor(mem_ctx, locations_used, mode,
-                                         gs_input_vertices,
-                                         &new_instructions,
-                                         &new_variables,
-                                         disable_varying_packing);
-   visitor.run(shader);
-   if (mode == ir_var_shader_out) {
-      if (shader->Stage == MESA_SHADER_GEOMETRY) {
-         /* For geometry shaders, outputs need to be lowered before each call
-          * to EmitVertex()
-          */
-         lower_packed_varyings_gs_splicer splicer(mem_ctx, &new_instructions);
-
-         /* Add all the variables in first. */
-         main_func_sig->body.head->insert_before(&new_variables);
 
-         /* Now update all the EmitVertex instances */
-         splicer.run(instructions);
+   if (!(shader->Stage == MESA_SHADER_TESS_CTRL ||
+         shader->Stage == MESA_SHADER_TESS_EVAL)) {
+      exec_list *instructions = shader->ir;
+      exec_list new_instructions, new_variables;
+
+      lower_packed_varyings_visitor visitor(mem_ctx, locations_used, mode,
+                                            gs_input_vertices,
+                                            &new_instructions,
+                                            &new_variables,
+                                            disable_varying_packing);
+      visitor.run(shader);
+      if (mode == ir_var_shader_out) {
+         if (shader->Stage == MESA_SHADER_GEOMETRY) {
+            /* For geometry shaders, outputs need to be lowered before each
+             * call to EmitVertex()
+             */
+            lower_packed_varyings_gs_splicer splicer(mem_ctx,
+                                                     &new_instructions);
+
+            /* Add all the variables in first. */
+            main_func_sig->body.head->insert_before(&new_variables);
+
+            /* Now update all the EmitVertex instances */
+            splicer.run(instructions);
+         } else {
+            /* For other shader types, outputs need to be lowered at the end
+             * of main()
+             */
+            main_func_sig->body.append_list(&new_variables);
+            main_func_sig->body.append_list(&new_instructions);
+         }
       } else {
-         /* For other shader types, outputs need to be lowered at the end of
-          * main()
-          */
-         main_func_sig->body.append_list(&new_variables);
-         main_func_sig->body.append_list(&new_instructions);
+         /* Shader inputs need to be lowered at the beginning of main() */
+         main_func_sig->body.head->insert_before(&new_instructions);
+         main_func_sig->body.head->insert_before(&new_variables);
       }
-   } else {
-      /* Shader inputs need to be lowered at the beginning of main() */
-      main_func_sig->body.head->insert_before(&new_instructions);
-      main_func_sig->body.head->insert_before(&new_variables);
    }
 }
-- 
2.4.3