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 #include "linker_util.h"
28
29 /**
30 * Pre-linking, optimize unused built-in variables
31 *
32 * Uniforms, constants, system values, inputs (vertex shader only), and
33 * outputs (fragment shader only) that are not used can be removed.
34 */
35 void
optimize_dead_builtin_variables(exec_list * instructions,enum ir_variable_mode other)36 optimize_dead_builtin_variables(exec_list *instructions,
37 enum ir_variable_mode other)
38 {
39 foreach_in_list_safe(ir_instruction, inst, instructions) {
40 ir_variable *var = inst->as_variable();
41 if (!var || var->data.used)
42 continue;
43
44 if (var->data.mode != ir_var_uniform
45 && var->data.mode != ir_var_auto
46 && var->data.mode != ir_var_system_value
47 && var->data.mode != other)
48 continue;
49
50 /* So that linker rules can later be enforced, we cannot elimate
51 * variables that were redeclared in the shader code.
52 */
53 if ((var->data.mode == other || var->data.mode == ir_var_system_value)
54 && var->data.how_declared != ir_var_declared_implicitly)
55 continue;
56
57 if (!is_gl_identifier(var->name))
58 continue;
59
60 /* gl_ModelViewProjectionMatrix and gl_Vertex are special because they
61 * are used by ftransform. No other built-in variable is used by a
62 * built-in function. The forward declarations of these variables in
63 * the built-in function shader does not have the "state slot"
64 * information, so removing these variables from the user shader will
65 * cause problems later.
66 *
67 * Matrix uniforms with "Transpose" are not eliminated because there's
68 * an optimization pass that can turn references to the regular matrix
69 * into references to the transpose matrix. Eliminating the transpose
70 * matrix would cause that pass to generate references to undeclareds
71 * variables (thank you, ir_validate).
72 *
73 * It doesn't seem worth the effort to track when the transpose could be
74 * eliminated (i.e., when the non-transpose was eliminated).
75 */
76 if (strcmp(var->name, "gl_ModelViewProjectionMatrix") == 0
77 || strcmp(var->name, "gl_Vertex") == 0
78 || strstr(var->name, "Transpose") != NULL)
79 continue;
80
81 var->remove();
82 }
83 }
84