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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 "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;
54 hash_table_foreach(v
.ht
, e
) {
55 ir_variable_refcount_entry
*entry
= (ir_variable_refcount_entry
*)e
->data
;
57 /* Since each assignment is a reference, the refereneced count must be
58 * greater than or equal to the assignment count. If they are equal,
59 * then all of the references are assignments, and the variable is
62 * Note that if the variable is neither assigned nor referenced, both
63 * counts will be zero and will be caught by the equality test.
65 assert(entry
->referenced_count
>= entry
->assigned_count
);
68 printf("%s@%p: %d refs, %d assigns, %sdeclared in our scope\n",
69 entry
->var
->name
, (void *) entry
->var
,
70 entry
->referenced_count
, entry
->assigned_count
,
71 entry
->declaration
? "" : "not ");
74 if ((entry
->referenced_count
> entry
->assigned_count
)
75 || !entry
->declaration
)
78 if (!entry
->assign_list
.is_empty()) {
79 /* Remove all the dead assignments to the variable we found.
80 * Don't do so if it's a shader or function output, though.
82 if (entry
->var
->data
.mode
!= ir_var_function_out
&&
83 entry
->var
->data
.mode
!= ir_var_function_inout
&&
84 entry
->var
->data
.mode
!= ir_var_shader_out
&&
85 entry
->var
->data
.mode
!= ir_var_shader_storage
) {
87 while (!entry
->assign_list
.is_empty()) {
88 struct assignment_entry
*assignment_entry
=
89 exec_node_data(struct assignment_entry
,
90 entry
->assign_list
.head
, link
);
92 assignment_entry
->assign
->remove();
95 printf("Removed assignment to %s@%p\n",
96 entry
->var
->name
, (void *) entry
->var
);
99 assignment_entry
->link
.remove();
100 free(assignment_entry
);
106 if (entry
->assign_list
.is_empty()) {
107 /* If there are no assignments or references to the variable left,
108 * then we can remove its declaration.
111 /* uniform initializers are precious, and could get used by another
112 * stage. Also, once uniform locations have been assigned, the
113 * declaration cannot be deleted.
115 if (entry
->var
->data
.mode
== ir_var_uniform
||
116 entry
->var
->data
.mode
== ir_var_shader_storage
) {
117 if (uniform_locations_assigned
|| entry
->var
->constant_initializer
)
120 /* Section 2.11.6 (Uniform Variables) of the OpenGL ES 3.0.3 spec
123 * "All members of a named uniform block declared with a
124 * shared or std140 layout qualifier are considered active,
125 * even if they are not referenced in any shader in the
126 * program. The uniform block itself is also considered
127 * active, even if no member of the block is referenced."
129 * If the variable is in a uniform block with one of those
130 * layouts, do not eliminate it.
132 if (entry
->var
->is_in_buffer_block()) {
133 if (entry
->var
->get_interface_type()->interface_packing
!=
134 GLSL_INTERFACE_PACKING_PACKED
)
138 if (entry
->var
->type
->is_subroutine())
142 entry
->var
->remove();
146 printf("Removed declaration of %s@%p\n",
147 entry
->var
->name
, (void *) entry
->var
);
156 * Does a dead code pass on the functions present in the instruction stream.
158 * This is suitable for use while the program is not linked, as it will
159 * ignore variable declarations (and the assignments to them) for variables
163 do_dead_code_unlinked(exec_list
*instructions
)
165 bool progress
= false;
167 foreach_in_list(ir_instruction
, ir
, instructions
) {
168 ir_function
*f
= ir
->as_function();
170 foreach_in_list(ir_function_signature
, sig
, &f
->signatures
) {
171 /* The setting of the uniform_locations_assigned flag here is
172 * irrelevent. If there is a uniform declaration encountered
173 * inside the body of the function, something has already gone
174 * terribly, terribly wrong.
176 if (do_dead_code(&sig
->body
, false))