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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"
35 static bool debug
= false;
38 * Do a dead code pass over instructions and everything that instructions
41 * Note that this will remove assignments to globals, so it is not suitable
42 * for usage on an unlinked instruction stream.
45 do_dead_code(exec_list
*instructions
, bool uniform_locations_assigned
)
47 ir_variable_refcount_visitor v
;
48 bool progress
= false;
52 foreach_iter(exec_list_iterator
, iter
, v
.variable_list
) {
53 ir_variable_refcount_entry
*entry
= (ir_variable_refcount_entry
*)iter
.get();
55 /* Since each assignment is a reference, the refereneced count must be
56 * greater than or equal to the assignment count. If they are equal,
57 * then all of the references are assignments, and the variable is
60 * Note that if the variable is neither assigned nor referenced, both
61 * counts will be zero and will be caught by the equality test.
63 assert(entry
->referenced_count
>= entry
->assigned_count
);
66 printf("%s@%p: %d refs, %d assigns, %sdeclared in our scope\n",
67 entry
->var
->name
, (void *) entry
->var
,
68 entry
->referenced_count
, entry
->assigned_count
,
69 entry
->declaration
? "" : "not ");
72 if ((entry
->referenced_count
> entry
->assigned_count
)
73 || !entry
->declaration
)
77 /* Remove a single dead assignment to the variable we found.
78 * Don't do so if it's a shader output, though.
80 if (entry
->var
->mode
!= ir_var_out
&&
81 entry
->var
->mode
!= ir_var_inout
) {
82 entry
->assign
->remove();
86 printf("Removed assignment to %s@%p\n",
87 entry
->var
->name
, (void *) entry
->var
);
91 /* If there are no assignments or references to the variable left,
92 * then we can remove its declaration.
95 /* uniform initializers are precious, and could get used by another
96 * stage. Also, once uniform locations have been assigned, the
97 * declaration cannot be deleted.
99 * Also, GL_ARB_uniform_buffer_object says that std140
100 * uniforms will not be eliminated. Since we always do
101 * std140, just don't eliminate uniforms in UBOs.
103 if (entry
->var
->mode
== ir_var_uniform
&&
104 (uniform_locations_assigned
||
105 entry
->var
->constant_value
||
106 entry
->var
->uniform_block
!= -1))
109 entry
->var
->remove();
113 printf("Removed declaration of %s@%p\n",
114 entry
->var
->name
, (void *) entry
->var
);
123 * Does a dead code pass on the functions present in the instruction stream.
125 * This is suitable for use while the program is not linked, as it will
126 * ignore variable declarations (and the assignments to them) for variables
130 do_dead_code_unlinked(exec_list
*instructions
)
132 bool progress
= false;
134 foreach_iter(exec_list_iterator
, iter
, *instructions
) {
135 ir_instruction
*ir
= (ir_instruction
*)iter
.get();
136 ir_function
*f
= ir
->as_function();
138 foreach_iter(exec_list_iterator
, sigiter
, *f
) {
139 ir_function_signature
*sig
=
140 (ir_function_signature
*) sigiter
.get();
141 /* The setting of the uniform_locations_assigned flag here is
142 * irrelevent. If there is a uniform declaration encountered
143 * inside the body of the function, something has already gone
144 * terribly, terribly wrong.
146 if (do_dead_code(&sig
->body
, false))