glsl/linker: prevent segfaults in packed varyings when linking SPIR-V shaders

We could actually disable (most?) of lower_packed_varyings entirely,
because SPIR-V mandates explicit locations for varyings. Anyway, we don't
have a main function in the IR, so skip the corresponding insertions.

1 files changed, 22 insertions, 7 deletions

diff --git a/src/compiler/glsl/lower_packed_varyings.cpp b/src/compiler/glsl/lower_packed_varyings.cpp
index 1aec7ee7dc..789658a7a7 100644
--- a/src/compiler/glsl/lower_packed_varyings.cpp
+++ b/src/compiler/glsl/lower_packed_varyings.cpp
@@ -874,7 +874,7 @@ lower_packed_varyings(void *mem_ctx, unsigned locations_used,
    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);
+      = main_func ? main_func->matching_signature(NULL, &void_parameters, false) : NULL;
    exec_list new_instructions, new_variables;
    lower_packed_varyings_visitor visitor(mem_ctx,
                                          locations_used,
@@ -893,8 +893,12 @@ lower_packed_varyings(void *mem_ctx, unsigned locations_used,
           */
          lower_packed_varyings_gs_splicer splicer(mem_ctx, &new_instructions);
 
-         /* Add all the variables in first. */
-         main_func_sig->body.get_head_raw()->insert_before(&new_variables);
+         assert(new_variables.is_empty() || main_func_sig != NULL);
+
+         if (!new_variables.is_empty()) {
+            /* Add all the variables in first. */
+            main_func_sig->body.get_head_raw()->insert_before(&new_variables);
+         }
 
          /* Now update all the EmitVertex instances */
          splicer.run(instructions);
@@ -905,20 +909,31 @@ lower_packed_varyings(void *mem_ctx, unsigned locations_used,
 
          lower_packed_varyings_return_splicer splicer(mem_ctx, &new_instructions);
 
-         main_func_sig->body.get_head_raw()->insert_before(&new_variables);
+         assert(new_variables.is_empty() || main_func_sig != NULL);
+
+         if (!new_variables.is_empty())
+            main_func_sig->body.get_head_raw()->insert_before(&new_variables);
 
          splicer.run(instructions);
 
+         assert(new_instructions.is_empty() || main_func_sig != NULL);
+
          /* Lower outputs at the end of main() if the last instruction is not
           * a return statement
           */
-         if (((ir_instruction*)instructions->get_tail())->ir_type != ir_type_return) {
+         if (main_func_sig != NULL &&
+             ((ir_instruction*)instructions->get_tail())->ir_type != ir_type_return) {
             main_func_sig->body.append_list(&new_instructions);
          }
       }
    } else {
+      assert((new_instructions.is_empty() && new_variables.is_empty()) ||
+             main_func_sig != NULL);
+
       /* Shader inputs need to be lowered at the beginning of main() */
-      main_func_sig->body.get_head_raw()->insert_before(&new_instructions);
-      main_func_sig->body.get_head_raw()->insert_before(&new_variables);
+      if (!new_instructions.is_empty())
+         main_func_sig->body.get_head_raw()->insert_before(&new_instructions);
+      if (!new_variables.is_empty())
+         main_func_sig->body.get_head_raw()->insert_before(&new_variables);
    }
 }