glsl/lower_if: don't lower branches touching tess control outputs

Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>

src/compiler/glsl/ir_optimization.h

@@ -108,7 +108,8 @@ bool do_lower_texture_projection(exec_list *instructions);
 bool do_if_simplification(exec_list *instructions);
 bool opt_flatten_nested_if_blocks(exec_list *instructions);
 bool do_discard_simplification(exec_list *instructions);
-bool lower_if_to_cond_assign(exec_list *instructions, unsigned max_depth = 0);
+bool lower_if_to_cond_assign(gl_shader_stage stage, exec_list *instructions,
+                             unsigned max_depth = 0);
 bool do_mat_op_to_vec(exec_list *instructions);
 bool do_minmax_prune(exec_list *instructions);
 bool do_noop_swizzle(exec_list *instructions);

src/compiler/glsl/lower_if_to_cond_assign.cpp

@@ -54,9 +54,11 @@ namespace {
 
 class ir_if_to_cond_assign_visitor : public ir_hierarchical_visitor {
 public:
-   ir_if_to_cond_assign_visitor(unsigned max_depth)
+   ir_if_to_cond_assign_visitor(gl_shader_stage stage,
+                                unsigned max_depth)
    {
       this->progress = false;
+      this->stage = stage;
       this->max_depth = max_depth;
       this->depth = 0;
 
@@ -75,6 +77,7 @@ public:
 
    bool found_unsupported_op;
    bool progress;
+   gl_shader_stage stage;
    unsigned max_depth;
    unsigned depth;
 
@@ -84,12 +87,13 @@ public:
 } /* anonymous namespace */
 
 bool
-lower_if_to_cond_assign(exec_list *instructions, unsigned max_depth)
+lower_if_to_cond_assign(gl_shader_stage stage, exec_list *instructions,
+                        unsigned max_depth)
 {
    if (max_depth == UINT_MAX)
       return false;
 
-   ir_if_to_cond_assign_visitor v(max_depth);
+   ir_if_to_cond_assign_visitor v(stage, max_depth);
 
    visit_list_elements(&v, instructions);
 
@@ -112,6 +116,19 @@ check_ir_node(ir_instruction *ir, void *data)
    case ir_type_barrier:
       v->found_unsupported_op = true;
       break;
+
+   case ir_type_dereference_variable: {
+      ir_variable *var = ir->as_dereference_variable()->variable_referenced();
+
+      /* Lowering branches with TCS output accesses breaks many piglit tests,
+       * so don't touch them for now.
+       */
+      if (v->stage == MESA_SHADER_TESS_CTRL &&
+          var->data.mode == ir_var_shader_out)
+         v->found_unsupported_op = true;
+      break;
+   }
+
    default:
       break;
    }

src/compiler/glsl/test_optpass.cpp

@@ -99,7 +99,7 @@ do_optimization(struct exec_list *ir, const char *optimization,
       return do_if_simplification(ir);
    } else if (sscanf(optimization, "lower_if_to_cond_assign ( %d ) ",
                      &int_0) == 1) {
-      return lower_if_to_cond_assign(ir, int_0);
+      return lower_if_to_cond_assign(MESA_SHADER_VERTEX, ir, int_0);
    } else if (strcmp(optimization, "do_mat_op_to_vec") == 0) {
       return do_mat_op_to_vec(ir);
    } else if (strcmp(optimization, "do_noop_swizzle") == 0) {

src/mesa/drivers/dri/i965/brw_link.cpp

@@ -125,7 +125,7 @@ process_glsl_ir(struct brw_context *brw,
     * if-statements need to be flattened.
     */
    if (brw->gen < 6)
-      lower_if_to_cond_assign(shader->ir, 16);
+      lower_if_to_cond_assign(shader->Stage, shader->ir, 16);
 
    do_lower_texture_projection(shader->ir);
    brw_lower_texture_gradients(brw, shader->ir);

src/mesa/program/ir_to_mesa.cpp

@@ -2995,7 +2995,8 @@ _mesa_ir_link_shader(struct gl_context *ctx, struct gl_shader_program *prog)
 	 if (options->MaxIfDepth == 0)
 	    progress = lower_discard(ir) || progress;
 
-	 progress = lower_if_to_cond_assign(ir, options->MaxIfDepth) || progress;
+	 progress = lower_if_to_cond_assign((gl_shader_stage)i, ir,
+                                            options->MaxIfDepth) || progress;
 
          progress = lower_noise(ir) || progress;
 

src/mesa/state_tracker/st_glsl_to_tgsi.cpp

@@ -6864,7 +6864,8 @@ st_link_shader(struct gl_context *ctx, struct gl_shader_program *prog)
                                            ctx->Const.NativeIntegers)
            || progress;
 
-         progress = lower_if_to_cond_assign(ir, options->MaxIfDepth) || progress;
+         progress = lower_if_to_cond_assign((gl_shader_stage)i, ir,
+                                            options->MaxIfDepth) || progress;
 
       } while (progress);