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25 * \file lower_vec_index_to_swizzle.cpp
27 * Turns constant indexing into vector types to swizzles. This will
28 * let other swizzle-aware optimization passes catch these constructs,
29 * and codegen backends not have to worry about this case.
33 #include "ir_visitor.h"
34 #include "ir_optimization.h"
35 #include "glsl_types.h"
36 #include "main/macros.h"
39 * Visitor class for replacing expressions with ir_constant values.
44 class ir_vec_index_to_swizzle_visitor
: public ir_hierarchical_visitor
{
46 ir_vec_index_to_swizzle_visitor()
51 ir_rvalue
*convert_vector_extract_to_swizzle(ir_rvalue
*val
);
53 virtual ir_visitor_status
visit_enter(ir_expression
*);
54 virtual ir_visitor_status
visit_enter(ir_swizzle
*);
55 virtual ir_visitor_status
visit_enter(ir_assignment
*);
56 virtual ir_visitor_status
visit_enter(ir_return
*);
57 virtual ir_visitor_status
visit_enter(ir_call
*);
58 virtual ir_visitor_status
visit_enter(ir_if
*);
63 } /* anonymous namespace */
66 ir_vec_index_to_swizzle_visitor::convert_vector_extract_to_swizzle(ir_rvalue
*ir
)
68 ir_expression
*const expr
= ir
->as_expression();
69 if (expr
== NULL
|| expr
->operation
!= ir_binop_vector_extract
)
72 ir_constant
*const idx
= expr
->operands
[1]->constant_expression_value();
76 void *ctx
= ralloc_parent(ir
);
77 this->progress
= true;
79 /* Page 40 of the GLSL 1.20 spec says:
81 * "When indexing with non-constant expressions, behavior is undefined
82 * if the index is negative, or greater than or equal to the size of
85 * The quoted spec text mentions non-constant expressions, but this code
86 * operates on constants. These constants are the result of non-constant
87 * expressions that have been optimized to constants. The common case here
88 * is a loop counter from an unrolled loop that is used to index a vector.
90 * The ir_swizzle constructor gets angry if the index is negative or too
91 * large. For simplicity sake, just clamp the index to [0, size-1].
93 const int i
= CLAMP(idx
->value
.i
[0], 0,
94 (int) expr
->operands
[0]->type
->vector_elements
- 1);
96 return new(ctx
) ir_swizzle(expr
->operands
[0], i
, 0, 0, 0, 1);
100 ir_vec_index_to_swizzle_visitor::visit_enter(ir_expression
*ir
)
104 for (i
= 0; i
< ir
->get_num_operands(); i
++) {
105 ir
->operands
[i
] = convert_vector_extract_to_swizzle(ir
->operands
[i
]);
108 return visit_continue
;
112 ir_vec_index_to_swizzle_visitor::visit_enter(ir_swizzle
*ir
)
114 /* Can't be hit from normal GLSL, since you can't swizzle a scalar (which
115 * the result of indexing a vector is. But maybe at some point we'll end up
116 * using swizzling of scalars for vector construction.
118 ir
->val
= convert_vector_extract_to_swizzle(ir
->val
);
120 return visit_continue
;
124 ir_vec_index_to_swizzle_visitor::visit_enter(ir_assignment
*ir
)
126 ir
->rhs
= convert_vector_extract_to_swizzle(ir
->rhs
);
128 return visit_continue
;
132 ir_vec_index_to_swizzle_visitor::visit_enter(ir_call
*ir
)
134 foreach_iter(exec_list_iterator
, iter
, *ir
) {
135 ir_rvalue
*param
= (ir_rvalue
*)iter
.get();
136 ir_rvalue
*new_param
= convert_vector_extract_to_swizzle(param
);
138 if (new_param
!= param
) {
139 param
->replace_with(new_param
);
143 return visit_continue
;
147 ir_vec_index_to_swizzle_visitor::visit_enter(ir_return
*ir
)
150 ir
->value
= convert_vector_extract_to_swizzle(ir
->value
);
153 return visit_continue
;
157 ir_vec_index_to_swizzle_visitor::visit_enter(ir_if
*ir
)
159 ir
->condition
= convert_vector_extract_to_swizzle(ir
->condition
);
161 return visit_continue
;
165 do_vec_index_to_swizzle(exec_list
*instructions
)
167 ir_vec_index_to_swizzle_visitor v
;