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_constant_folding.cpp
26 * Replace constant-valued expressions with references to constant values.
30 #include "ir_visitor.h"
31 #include "ir_rvalue_visitor.h"
32 #include "ir_optimization.h"
33 #include "glsl_types.h"
38 * Visitor class for replacing expressions with ir_constant values.
41 class ir_constant_folding_visitor
: public ir_rvalue_visitor
{
43 ir_constant_folding_visitor()
45 this->progress
= false;
48 virtual ~ir_constant_folding_visitor()
53 virtual ir_visitor_status
visit_enter(ir_assignment
*ir
);
54 virtual ir_visitor_status
visit_enter(ir_call
*ir
);
56 virtual void handle_rvalue(ir_rvalue
**rvalue
);
61 } /* unnamed namespace */
64 ir_constant_folding_visitor::handle_rvalue(ir_rvalue
**rvalue
)
66 if (*rvalue
== NULL
|| (*rvalue
)->ir_type
== ir_type_constant
)
69 /* Note that we do rvalue visitoring on leaving. So if an
70 * expression has a non-constant operand, no need to go looking
71 * down it to find if it's constant. This cuts the time of this
72 * pass down drastically.
74 ir_expression
*expr
= (*rvalue
)->as_expression();
76 for (unsigned int i
= 0; i
< expr
->get_num_operands(); i
++) {
77 if (!expr
->operands
[i
]->as_constant())
82 /* Ditto for swizzles. */
83 ir_swizzle
*swiz
= (*rvalue
)->as_swizzle();
84 if (swiz
&& !swiz
->val
->as_constant())
87 ir_constant
*constant
= (*rvalue
)->constant_expression_value();
90 this->progress
= true;
92 (*rvalue
)->accept(this);
97 ir_constant_folding_visitor::visit_enter(ir_assignment
*ir
)
99 ir
->rhs
->accept(this);
100 handle_rvalue(&ir
->rhs
);
103 ir
->condition
->accept(this);
104 handle_rvalue(&ir
->condition
);
106 ir_constant
*const_val
= ir
->condition
->as_constant();
107 /* If the condition is constant, either remove the condition or
108 * remove the never-executed assignment.
111 if (const_val
->value
.b
[0])
112 ir
->condition
= NULL
;
115 this->progress
= true;
119 /* Don't descend into the LHS because we want it to stay as a
120 * variable dereference. FINISHME: We probably should to get array
123 return visit_continue_with_parent
;
127 ir_constant_folding_visitor::visit_enter(ir_call
*ir
)
129 /* Attempt to constant fold parameters */
130 foreach_two_lists(formal_node
, &ir
->callee
->parameters
,
131 actual_node
, &ir
->actual_parameters
) {
132 ir_rvalue
*param_rval
= (ir_rvalue
*) actual_node
;
133 ir_variable
*sig_param
= (ir_variable
*) formal_node
;
135 if (sig_param
->data
.mode
== ir_var_function_in
136 || sig_param
->data
.mode
== ir_var_const_in
) {
137 ir_rvalue
*new_param
= param_rval
;
139 handle_rvalue(&new_param
);
140 if (new_param
!= param_rval
) {
141 param_rval
->replace_with(new_param
);
146 /* Next, see if the call can be replaced with an assignment of a constant */
147 ir_constant
*const_val
= ir
->constant_expression_value();
149 if (const_val
!= NULL
) {
150 ir_assignment
*assignment
=
151 new(ralloc_parent(ir
)) ir_assignment(ir
->return_deref
, const_val
);
152 ir
->replace_with(assignment
);
155 return visit_continue_with_parent
;
159 do_constant_folding(exec_list
*instructions
)
161 ir_constant_folding_visitor constant_folding
;
163 visit_list_elements(&constant_folding
, instructions
);
165 return constant_folding
.progress
;