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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_rvalue_visitor.h"
34 #include "ir_optimization.h"
35 #include "compiler/glsl_types.h"
36 #include "main/macros.h"
40 class ir_vec_index_to_swizzle_visitor
: public ir_rvalue_visitor
{
42 ir_vec_index_to_swizzle_visitor()
47 ir_rvalue
*convert_vector_extract_to_swizzle(ir_rvalue
*val
);
49 virtual void handle_rvalue(ir_rvalue
**);
54 } /* anonymous namespace */
57 ir_vec_index_to_swizzle_visitor::handle_rvalue(ir_rvalue
**rv
)
62 ir_expression
*const expr
= (*rv
)->as_expression();
63 if (expr
== NULL
|| expr
->operation
!= ir_binop_vector_extract
)
66 ir_constant
*const idx
= expr
->operands
[1]->constant_expression_value();
70 void *ctx
= ralloc_parent(expr
);
71 this->progress
= true;
73 /* Page 40 of the GLSL 1.20 spec says:
75 * "When indexing with non-constant expressions, behavior is undefined
76 * if the index is negative, or greater than or equal to the size of
79 * The quoted spec text mentions non-constant expressions, but this code
80 * operates on constants. These constants are the result of non-constant
81 * expressions that have been optimized to constants. The common case here
82 * is a loop counter from an unrolled loop that is used to index a vector.
84 * The ir_swizzle constructor gets angry if the index is negative or too
85 * large. For simplicity sake, just clamp the index to [0, size-1].
87 const int i
= CLAMP(idx
->value
.i
[0], 0,
88 (int) expr
->operands
[0]->type
->vector_elements
- 1);
90 *rv
= new(ctx
) ir_swizzle(expr
->operands
[0], i
, 0, 0, 0, 1);
94 do_vec_index_to_swizzle(exec_list
*instructions
)
96 ir_vec_index_to_swizzle_visitor v
;