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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"
36 * Visitor class for replacing expressions with ir_constant values.
39 class ir_constant_folding_visitor : public ir_rvalue_visitor {
41 ir_constant_folding_visitor()
43 this->progress = false;
46 virtual ~ir_constant_folding_visitor()
51 virtual ir_visitor_status visit_enter(ir_assignment *ir);
52 virtual ir_visitor_status visit_enter(ir_call *ir);
54 virtual void handle_rvalue(ir_rvalue **rvalue);
60 ir_constant_folding_visitor::handle_rvalue(ir_rvalue **rvalue)
62 if (*rvalue == NULL || (*rvalue)->ir_type == ir_type_constant)
65 /* Note that we do rvalue visitoring on leaving. So if an
66 * expression has a non-constant operand, no need to go looking
67 * down it to find if it's constant. This cuts the time of this
68 * pass down drastically.
70 ir_expression *expr = (*rvalue)->as_expression();
72 for (unsigned int i = 0; i < expr->get_num_operands(); i++) {
73 if (!expr->operands[i]->as_constant())
78 ir_constant *constant = (*rvalue)->constant_expression_value();
81 this->progress = true;
83 (*rvalue)->accept(this);
88 ir_constant_folding_visitor::visit_enter(ir_assignment *ir)
90 ir->rhs->accept(this);
91 handle_rvalue(&ir->rhs);
94 ir->condition->accept(this);
95 handle_rvalue(&ir->condition);
97 ir_constant *const_val = ir->condition->as_constant();
98 /* If the condition is constant, either remove the condition or
99 * remove the never-executed assignment.
102 if (const_val->value.b[0])
103 ir->condition = NULL;
106 this->progress = true;
110 /* Don't descend into the LHS because we want it to stay as a
111 * variable dereference. FINISHME: We probably should to get array
114 return visit_continue_with_parent;
118 ir_constant_folding_visitor::visit_enter(ir_call *ir)
120 exec_list_iterator sig_iter = ir->get_callee()->parameters.iterator();
121 foreach_iter(exec_list_iterator, iter, *ir) {
122 ir_rvalue *param_rval = (ir_rvalue *)iter.get();
123 ir_variable *sig_param = (ir_variable *)sig_iter.get();
125 if (sig_param->mode == ir_var_in || sig_param->mode == ir_var_const_in) {
126 ir_rvalue *new_param = param_rval;
128 handle_rvalue(&new_param);
129 if (new_param != param_rval) {
130 param_rval->replace_with(new_param);
136 return visit_continue_with_parent;
140 do_constant_folding(exec_list *instructions)
142 ir_constant_folding_visitor constant_folding;
144 visit_list_elements(&constant_folding, instructions);
146 return constant_folding.progress;