[Mesa-dev] [PATCH] glsl/linker: Link all out vars from a shader objects on a single stage

[Vadym Shovkoplias]

From: "vadym.shovkoplias" <vadym.shovkoplias at globallogic.com>

During intra stage linking some out variables can be dropped because
it is not used in a shader with the main function. But these out vars
can be referenced on later stages which can lead to further linking
errors.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105731
Signed-off-by: Vadym Shovkoplias <vadym.shovkoplias at globallogic.com>
---
 src/compiler/glsl/linker.cpp | 37 ++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/src/compiler/glsl/linker.cpp b/src/compiler/glsl/linker.cpp
index 3ce78fe642..dbd76b7fcc 100644
--- a/src/compiler/glsl/linker.cpp
+++ b/src/compiler/glsl/linker.cpp
@@ -2187,6 +2187,40 @@ link_cs_input_layout_qualifiers(struct gl_shader_program *prog,
    }
 }
 
+/**
+ * Link all out variables on a single stage which are not
+ * directly used in a shader with the main function.
+ */
+static void
+link_output_variables(struct gl_linked_shader *linked_shader,
+                      struct gl_shader **shader_list,
+                      unsigned num_shaders)
+{
+   struct glsl_symbol_table *symbols = linked_shader->symbols;
+
+   for (unsigned i = 0; i < num_shaders; i++) {
+
+      /* Skip shader object with main function */
+      if (shader_list[i]->symbols->get_function("main"))
+         continue;
+
+      foreach_in_list (ir_instruction, ir, shader_list[i]->ir) {
+         if (ir->ir_type != ir_type_variable)
+            continue;
+
+         ir_variable *const var = (ir_variable *) ir;
+
+         if (var->data.mode == ir_var_shader_out &&
+               !symbols->get_variable(var->name)) {
+            symbols->add_variable(var);
+            linked_shader->ir->push_head(var);
+         }
+      }
+   }
+
+   return;
+}
+
 
 /**
  * Combine a group of shaders for a single stage to generate a linked shader
@@ -2352,6 +2386,9 @@ link_intrastage_shaders(void *mem_ctx,
       return NULL;
    }
 
+   if (linked->Stage != MESA_SHADER_FRAGMENT)
+      link_output_variables(linked, shader_list, num_shaders);
+
    /* Make a pass over all variable declarations to ensure that arrays with
     * unspecified sizes have a size specified.  The size is inferred from the
     * max_array_access field.
-- 
2.18.0