glsl: Support transform feedback of varying structs.

Since transform feedback needs to be able to access individual fields
of varying structs, we can no longer match up the arguments to
glTransformFeedbackVaryings() with variables in the vertex shader.

Instead, we build up a hashtable which records information about each
possible name that is a candidate for transform feedback, and then
match up the arguments to glTransformFeedbackVaryings() with the
contents of that hashtable.

Populating the hashtable uses the program_resource_visitor
infrastructure, so the logic is shared with how we handle uniforms.

NOTE: This is a candidate for the 9.1 branch.

Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>

1 files changed, 53 insertions, 4 deletions

diff --git a/src/glsl/link_varyings.h b/src/glsl/link_varyings.h
index 806bd1c..ee1010a 100644
--- a/src/glsl/link_varyings.h
+++ b/src/glsl/link_varyings.h
@@ -42,6 +42,49 @@ class ir_variable;
 
 
 /**
+ * Data structure describing a varying which is available for use in transform
+ * feedback.
+ *
+ * For example, if the vertex shader contains:
+ *
+ *     struct S {
+ *       vec4 foo;
+ *       float[3] bar;
+ *     };
+ *
+ *     varying S[2] v;
+ *
+ * Then there would be tfeedback_candidate objects corresponding to the
+ * following varyings:
+ *
+ *     v[0].foo
+ *     v[0].bar
+ *     v[1].foo
+ *     v[1].bar
+ */
+struct tfeedback_candidate
+{
+   /**
+    * Toplevel variable containing this varying.  In the above example, this
+    * would point to the declaration of the varying v.
+    */
+   ir_variable *toplevel_var;
+
+   /**
+    * Type of this varying.  In the above example, this would point to the
+    * glsl_type for "vec4" or "float[3]".
+    */
+   const glsl_type *type;
+
+   /**
+    * Offset within the toplevel variable where this varying occurs (counted
+    * in multiples of the size of a float).
+    */
+   unsigned offset;
+};
+
+
+/**
  * Data structure tracking information about a transform feedback declaration
  * during linking.
  */
@@ -51,14 +94,14 @@ public:
    void init(struct gl_context *ctx, struct gl_shader_program *prog,
              const void *mem_ctx, const char *input);
    static bool is_same(const tfeedback_decl &x, const tfeedback_decl &y);
-   bool assign_location(struct gl_context *ctx, struct gl_shader_program *prog,
-                        ir_variable *output_var);
+   bool assign_location(struct gl_context *ctx,
+                        struct gl_shader_program *prog);
    unsigned get_num_outputs() const;
    bool store(struct gl_context *ctx, struct gl_shader_program *prog,
               struct gl_transform_feedback_info *info, unsigned buffer,
               const unsigned max_outputs) const;
-   ir_variable *find_output_var(gl_shader_program *prog,
-                                gl_shader *producer) const;
+   const tfeedback_candidate *find_candidate(gl_shader_program *prog,
+                                             hash_table *tfeedback_candidates);
 
    bool is_next_buffer_separator() const
    {
@@ -158,6 +201,12 @@ private:
     * Whether this is gl_NextBuffer from ARB_transform_feedback3.
     */
    bool next_buffer_separator;
+
+   /**
+    * If find_candidate() has been called, pointer to the tfeedback_candidate
+    * data structure that was found.  Otherwise NULL.
+    */
+   const tfeedback_candidate *matched_candidate;
 };