src/compiler/glsl/opt_dead_builtin_variables.cpp

   1 /*
   2  * Copyright © 2014 Intel Corporation
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  21  * DEALINGS IN THE SOFTWARE.
  22  */
  23
  24 #include "ir.h"
  25 #include "ir_visitor.h"
  26 #include "ir_optimization.h"
  27
  28 /**
  29  * Pre-linking, optimize unused built-in variables
  30  *
  31  * Uniforms, constants, system values, inputs (vertex shader only), and
  32  * outputs (fragment shader only) that are not used can be removed.
  33  */
  34 void
  35 optimize_dead_builtin_variables(exec_list *instructions,
  36                                 enum ir_variable_mode other)
  37 {
  38    foreach_in_list_safe(ir_variable, var, instructions) {
  39       if (var->ir_type != ir_type_variable || var->data.used)
  40          continue;
  41
  42       if (var->data.mode != ir_var_uniform
  43           && var->data.mode != ir_var_auto
  44           && var->data.mode != ir_var_system_value
  45           && var->data.mode != other)
  46          continue;
  47
  48       /* So that linker rules can later be enforced, we cannot elimate
  49        * variables that were redeclared in the shader code.
  50        */
  51       if ((var->data.mode == other || var->data.mode == ir_var_system_value)
  52           && var->data.how_declared != ir_var_declared_implicitly)
  53          continue;
  54
  55       if (!is_gl_identifier(var->name))
  56          continue;
  57
  58       /* gl_ModelViewProjectionMatrix and gl_Vertex are special because they
  59        * are used by ftransform.  No other built-in variable is used by a
  60        * built-in function.  The forward declarations of these variables in
  61        * the built-in function shader does not have the "state slot"
  62        * information, so removing these variables from the user shader will
  63        * cause problems later.
  64        *
  65        * Matrix uniforms with "Transpose" are not eliminated because there's
  66        * an optimization pass that can turn references to the regular matrix
  67        * into references to the transpose matrix.  Eliminating the transpose
  68        * matrix would cause that pass to generate references to undeclareds
  69        * variables (thank you, ir_validate).
  70        *
  71        * It doesn't seem worth the effort to track when the transpose could be
  72        * eliminated (i.e., when the non-transpose was eliminated).
  73        */
  74       if (strcmp(var->name, "gl_ModelViewProjectionMatrix") == 0
  75           || strcmp(var->name, "gl_Vertex") == 0
  76           || strstr(var->name, "Transpose") != NULL)
  77          continue;
  78
  79       var->remove();
  80    }
  81 }