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Member "mesa-20.1.8/src/compiler/glsl/opt_dead_builtin_variables.cpp" (16 Sep 2020, 3398 Bytes) of package /linux/misc/mesa-20.1.8.tar.xz:


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    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 }