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25 * \file opt_constant_variable.cpp
27 * Marks variables assigned a single constant value over the course
28 * of the program as constant.
30 * The goal here is to trigger further constant folding and then dead
31 * code elimination. This is common with vector/matrix constructors
32 * and calls to builtin functions.
36 #include "ir_visitor.h"
37 #include "ir_optimization.h"
38 #include "glsl_types.h"
40 struct assignment_entry
{
44 ir_constant
*constval
;
48 class ir_constant_variable_visitor
: public ir_hierarchical_visitor
{
50 virtual ir_visitor_status
visit_enter(ir_dereference_variable
*);
51 virtual ir_visitor_status
visit(ir_variable
*);
52 virtual ir_visitor_status
visit_enter(ir_assignment
*);
53 virtual ir_visitor_status
visit_enter(ir_call
*);
58 static struct assignment_entry
*
59 get_assignment_entry(ir_variable
*var
, exec_list
*list
)
61 struct assignment_entry
*entry
;
63 foreach_list_typed(struct assignment_entry
, entry
, link
, list
) {
64 if (entry
->var
== var
)
68 entry
= (struct assignment_entry
*)calloc(1, sizeof(*entry
));
70 list
->push_head(&entry
->link
);
75 ir_constant_variable_visitor::visit(ir_variable
*ir
)
77 struct assignment_entry
*entry
= get_assignment_entry(ir
, &this->list
);
78 entry
->our_scope
= true;
79 return visit_continue
;
82 /* Skip derefs of variables so that we can detect declarations. */
84 ir_constant_variable_visitor::visit_enter(ir_dereference_variable
*ir
)
87 return visit_continue_with_parent
;
91 ir_constant_variable_visitor::visit_enter(ir_assignment
*ir
)
93 ir_constant
*constval
;
94 struct assignment_entry
*entry
;
96 entry
= get_assignment_entry(ir
->lhs
->variable_referenced(), &this->list
);
98 entry
->assignment_count
++;
100 /* If it's already constant, don't do the work. */
101 if (entry
->var
->constant_value
)
102 return visit_continue
;
104 /* OK, now find if we actually have all the right conditions for
105 * this to be a constant value assigned to the var.
108 return visit_continue
;
110 ir_variable
*var
= ir
->whole_variable_written();
112 return visit_continue
;
114 constval
= ir
->rhs
->constant_expression_value();
116 return visit_continue
;
118 /* Mark this entry as having a constant assignment (if the
119 * assignment count doesn't go >1). do_constant_variable will fix
120 * up the variable with the constant value later.
122 entry
->constval
= constval
;
124 return visit_continue
;
128 ir_constant_variable_visitor::visit_enter(ir_call
*ir
)
130 exec_list_iterator sig_iter
= ir
->get_callee()->parameters
.iterator();
131 foreach_iter(exec_list_iterator
, iter
, *ir
) {
132 ir_rvalue
*param_rval
= (ir_rvalue
*)iter
.get();
133 ir_variable
*param
= (ir_variable
*)sig_iter
.get();
135 if (param
->mode
== ir_var_out
||
136 param
->mode
== ir_var_inout
) {
137 ir_variable
*var
= param_rval
->variable_referenced();
138 struct assignment_entry
*entry
;
141 entry
= get_assignment_entry(var
, &this->list
);
142 entry
->assignment_count
++;
146 return visit_continue
;
150 * Does a copy propagation pass on the code present in the instruction stream.
153 do_constant_variable(exec_list
*instructions
)
155 bool progress
= false;
156 ir_constant_variable_visitor v
;
160 while (!v
.list
.is_empty()) {
162 struct assignment_entry
*entry
;
163 entry
= exec_node_data(struct assignment_entry
, v
.list
.head
, link
);
165 if (entry
->assignment_count
== 1 && entry
->constval
&& entry
->our_scope
) {
166 entry
->var
->constant_value
= entry
->constval
;
169 entry
->link
.remove();
177 do_constant_variable_unlinked(exec_list
*instructions
)
179 bool progress
= false;
181 foreach_iter(exec_list_iterator
, iter
, *instructions
) {
182 ir_instruction
*ir
= (ir_instruction
*)iter
.get();
183 ir_function
*f
= ir
->as_function();
185 foreach_iter(exec_list_iterator
, sigiter
, *f
) {
186 ir_function_signature
*sig
=
187 (ir_function_signature
*) sigiter
.get();
188 if (do_constant_variable(&sig
->body
))