- /* From the ARB_enhanced_layouts spec:
- *
- * "If the shader used to record output variables for transform feedback
- * varyings uses the "xfb_buffer", "xfb_offset", or "xfb_stride" layout
- * qualifiers, the values specified by TransformFeedbackVaryings are
- * ignored, and the set of variables captured for transform feedback is
- * instead derived from the specified layout qualifiers."
- */
- for (int i = MESA_SHADER_FRAGMENT - 1; i >= 0; i--) {
- /* Find last stage before fragment shader */
- if (prog->_LinkedShaders[i]) {
- has_xfb_qualifiers =
- process_xfb_layout_qualifiers(mem_ctx, prog->_LinkedShaders[i],
- &num_tfeedback_decls,
- &varying_names);
- break;
- }
- }
-
- if (!has_xfb_qualifiers) {
- num_tfeedback_decls = prog->TransformFeedback.NumVarying;
- varying_names = prog->TransformFeedback.VaryingNames;
- }
-
- if (num_tfeedback_decls != 0) {
- /* From GL_EXT_transform_feedback:
- * A program will fail to link if:
- *
- * * the <count> specified by TransformFeedbackVaryingsEXT is
- * non-zero, but the program object has no vertex or geometry
- * shader;
- */
- if (first >= MESA_SHADER_FRAGMENT) {
- linker_error(prog, "Transform feedback varyings specified, but "
- "no vertex, tessellation, or geometry shader is "
- "present.\n");
- return false;
- }
-
- tfeedback_decls = rzalloc_array(mem_ctx, tfeedback_decl,
- num_tfeedback_decls);
- if (!parse_tfeedback_decls(ctx, prog, mem_ctx, num_tfeedback_decls,
- varying_names, tfeedback_decls))
- return false;
- }
-
- /* If there is no fragment shader we need to set transform feedback.
- *
- * For SSO we also need to assign output locations. We assign them here
- * because we need to do it for both single stage programs and multi stage
- * programs.
- */
- if (last < MESA_SHADER_FRAGMENT &&
- (num_tfeedback_decls != 0 || prog->SeparateShader)) {
- const uint64_t reserved_out_slots =
- reserved_varying_slot(prog->_LinkedShaders[last], ir_var_shader_out);
- if (!assign_varying_locations(ctx, mem_ctx, prog,
- prog->_LinkedShaders[last], NULL,
- num_tfeedback_decls, tfeedback_decls,
- reserved_out_slots))
- return false;
- }
-
- if (last <= MESA_SHADER_FRAGMENT) {
- /* Remove unused varyings from the first/last stage unless SSO */
- remove_unused_shader_inputs_and_outputs(prog->SeparateShader,
- prog->_LinkedShaders[first],
- ir_var_shader_in);
- remove_unused_shader_inputs_and_outputs(prog->SeparateShader,
- prog->_LinkedShaders[last],
- ir_var_shader_out);
-
- /* If the program is made up of only a single stage */
- if (first == last) {
- gl_linked_shader *const sh = prog->_LinkedShaders[last];
-
- do_dead_builtin_varyings(ctx, NULL, sh, 0, NULL);
- do_dead_builtin_varyings(ctx, sh, NULL, num_tfeedback_decls,
- tfeedback_decls);
-
- if (prog->SeparateShader) {
- const uint64_t reserved_slots =
- reserved_varying_slot(sh, ir_var_shader_in);
-
- /* Assign input locations for SSO, output locations are already
- * assigned.
- */
- if (!assign_varying_locations(ctx, mem_ctx, prog,
- NULL /* producer */,
- sh /* consumer */,
- 0 /* num_tfeedback_decls */,
- NULL /* tfeedback_decls */,
- reserved_slots))
- return false;
- }
- } else {
- /* Linking the stages in the opposite order (from fragment to vertex)
- * ensures that inter-shader outputs written to in an earlier stage
- * are eliminated if they are (transitively) not used in a later
- * stage.
- */
- int next = last;
- for (int i = next - 1; i >= 0; i--) {
- if (prog->_LinkedShaders[i] == NULL && i != 0)
- continue;
-
- gl_linked_shader *const sh_i = prog->_LinkedShaders[i];
- gl_linked_shader *const sh_next = prog->_LinkedShaders[next];
-
- const uint64_t reserved_out_slots =
- reserved_varying_slot(sh_i, ir_var_shader_out);
- const uint64_t reserved_in_slots =
- reserved_varying_slot(sh_next, ir_var_shader_in);
-
- do_dead_builtin_varyings(ctx, sh_i, sh_next,
- next == MESA_SHADER_FRAGMENT ? num_tfeedback_decls : 0,
- tfeedback_decls);
-
- if (!assign_varying_locations(ctx, mem_ctx, prog, sh_i, sh_next,
- next == MESA_SHADER_FRAGMENT ? num_tfeedback_decls : 0,
- tfeedback_decls,
- reserved_out_slots | reserved_in_slots))
- return false;
-
- /* This must be done after all dead varyings are eliminated. */
- if (sh_i != NULL) {
- unsigned slots_used = _mesa_bitcount_64(reserved_out_slots);
- if (!check_against_output_limit(ctx, prog, sh_i, slots_used)) {
- return false;
- }
- }
-
- unsigned slots_used = _mesa_bitcount_64(reserved_in_slots);
- if (!check_against_input_limit(ctx, prog, sh_next, slots_used))
- return false;