2 * Copyright © 2010 Intel Corporation
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:
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
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.
25 * \file opt_dead_code.cpp
27 * Eliminates dead assignments and variable declarations from the code.
31 #include "ir_visitor.h"
32 #include "ir_variable_refcount.h"
33 #include "compiler/glsl_types.h"
34 #include "util/hash_table.h"
36 static bool debug
= false;
39 * Do a dead code pass over instructions and everything that instructions
42 * Note that this will remove assignments to globals, so it is not suitable
43 * for usage on an unlinked instruction stream.
46 do_dead_code(exec_list
*instructions
, bool uniform_locations_assigned
)
48 ir_variable_refcount_visitor v
;
49 bool progress
= false;
53 hash_table_foreach(v
.ht
, e
) {
54 ir_variable_refcount_entry
*entry
= (ir_variable_refcount_entry
*)e
->data
;
56 /* Since each assignment is a reference, the refereneced count must be
57 * greater than or equal to the assignment count. If they are equal,
58 * then all of the references are assignments, and the variable is
61 * Note that if the variable is neither assigned nor referenced, both
62 * counts will be zero and will be caught by the equality test.
64 assert(entry
->referenced_count
>= entry
->assigned_count
);
67 printf("%s@%p: %d refs, %d assigns, %sdeclared in our scope\n",
68 entry
->var
->name
, (void *) entry
->var
,
69 entry
->referenced_count
, entry
->assigned_count
,
70 entry
->declaration
? "" : "not ");
73 if ((entry
->referenced_count
> entry
->assigned_count
)
74 || !entry
->declaration
)
77 /* Section 7.4.1 (Shader Interface Matching) of the OpenGL 4.5
78 * (Core Profile) spec says:
80 * "With separable program objects, interfaces between shader
81 * stages may involve the outputs from one program object and the
82 * inputs from a second program object. For such interfaces, it is
83 * not possible to detect mismatches at link time, because the
84 * programs are linked separately. When each such program is
85 * linked, all inputs or outputs interfacing with another program
86 * stage are treated as active."
88 if (entry
->var
->data
.always_active_io
)
91 if (!entry
->assign_list
.is_empty()) {
92 /* Remove all the dead assignments to the variable we found.
93 * Don't do so if it's a shader or function output, though.
95 if (entry
->var
->data
.mode
!= ir_var_function_out
&&
96 entry
->var
->data
.mode
!= ir_var_function_inout
&&
97 entry
->var
->data
.mode
!= ir_var_shader_out
&&
98 entry
->var
->data
.mode
!= ir_var_shader_storage
) {
100 while (!entry
->assign_list
.is_empty()) {
101 struct assignment_entry
*assignment_entry
=
102 exec_node_data(struct assignment_entry
,
103 entry
->assign_list
.get_head_raw(), link
);
105 assignment_entry
->assign
->remove();
108 printf("Removed assignment to %s@%p\n",
109 entry
->var
->name
, (void *) entry
->var
);
112 assignment_entry
->link
.remove();
113 free(assignment_entry
);
119 if (entry
->assign_list
.is_empty()) {
120 /* If there are no assignments or references to the variable left,
121 * then we can remove its declaration.
124 /* uniform initializers are precious, and could get used by another
125 * stage. Also, once uniform locations have been assigned, the
126 * declaration cannot be deleted.
128 if (entry
->var
->data
.mode
== ir_var_uniform
||
129 entry
->var
->data
.mode
== ir_var_shader_storage
) {
130 if (uniform_locations_assigned
|| entry
->var
->constant_initializer
)
133 /* Section 2.11.6 (Uniform Variables) of the OpenGL ES 3.0.3 spec
136 * "All members of a named uniform block declared with a
137 * shared or std140 layout qualifier are considered active,
138 * even if they are not referenced in any shader in the
139 * program. The uniform block itself is also considered
140 * active, even if no member of the block is referenced."
142 * If the variable is in a uniform block with one of those
143 * layouts, do not eliminate it.
145 if (entry
->var
->is_in_buffer_block()) {
146 if (entry
->var
->get_interface_type_packing() !=
147 GLSL_INTERFACE_PACKING_PACKED
)
151 if (entry
->var
->type
->is_subroutine())
155 entry
->var
->remove();
159 printf("Removed declaration of %s@%p\n",
160 entry
->var
->name
, (void *) entry
->var
);
169 * Does a dead code pass on the functions present in the instruction stream.
171 * This is suitable for use while the program is not linked, as it will
172 * ignore variable declarations (and the assignments to them) for variables
176 do_dead_code_unlinked(exec_list
*instructions
)
178 bool progress
= false;
180 foreach_in_list(ir_instruction
, ir
, instructions
) {
181 ir_function
*f
= ir
->as_function();
183 foreach_in_list(ir_function_signature
, sig
, &f
->signatures
) {
184 /* The setting of the uniform_locations_assigned flag here is
185 * irrelevent. If there is a uniform declaration encountered
186 * inside the body of the function, something has already gone
187 * terribly, terribly wrong.
189 if (do_dead_code(&sig
->body
, false))