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25 * \file lower_vec_index_to_cond_assign.cpp
27 * Turns indexing into vector types to a series of conditional moves
28 * of each channel's swizzle into a temporary.
30 * Most GPUs don't have a native way to do this operation, and this
31 * works around that. For drivers using both this pass and
32 * ir_vec_index_to_swizzle, there's a risk that this pass will happen
33 * before sufficient constant folding to find that the array index is
34 * constant. However, we hope that other optimization passes,
35 * particularly constant folding of assignment conditions and copy
36 * propagation, will result in the same code in the end.
40 #include "ir_visitor.h"
41 #include "ir_optimization.h"
42 #include "compiler/glsl_types.h"
43 #include "ir_builder.h"
45 using namespace ir_builder
;
50 * Visitor class for replacing expressions with ir_constant values.
53 class ir_vec_index_to_cond_assign_visitor
: public ir_hierarchical_visitor
{
55 ir_vec_index_to_cond_assign_visitor()
61 ir_rvalue
*convert_vec_index_to_cond_assign(void *mem_ctx
,
62 ir_rvalue
*orig_vector
,
63 ir_rvalue
*orig_index
,
64 const glsl_type
*type
);
66 ir_rvalue
*convert_vector_extract_to_cond_assign(ir_rvalue
*ir
);
68 virtual ir_visitor_status
visit_enter(ir_expression
*);
69 virtual ir_visitor_status
visit_enter(ir_swizzle
*);
70 virtual ir_visitor_status
visit_leave(ir_assignment
*);
71 virtual ir_visitor_status
visit_enter(ir_return
*);
72 virtual ir_visitor_status
visit_enter(ir_call
*);
73 virtual ir_visitor_status
visit_enter(ir_if
*);
78 } /* anonymous namespace */
81 ir_vec_index_to_cond_assign_visitor::convert_vec_index_to_cond_assign(void *mem_ctx
,
82 ir_rvalue
*orig_vector
,
83 ir_rvalue
*orig_index
,
84 const glsl_type
*type
)
87 ir_factory
body(&list
, base_ir
);
89 /* Store the index to a temporary to avoid reusing its tree. */
90 assert(orig_index
->type
== glsl_type::int_type
||
91 orig_index
->type
== glsl_type::uint_type
);
92 ir_variable
*const index
=
93 body
.make_temp(orig_index
->type
, "vec_index_tmp_i");
95 body
.emit(assign(index
, orig_index
));
97 /* Store the value inside a temp, thus avoiding matrixes duplication */
98 ir_variable
*const value
=
99 body
.make_temp(orig_vector
->type
, "vec_value_tmp");
101 body
.emit(assign(value
, orig_vector
));
104 /* Temporary where we store whichever value we swizzle out. */
105 ir_variable
*const var
= body
.make_temp(type
, "vec_index_tmp_v");
107 /* Generate a single comparison condition "mask" for all of the components
110 ir_variable
*const cond
=
111 compare_index_block(body
, index
, 0, orig_vector
->type
->vector_elements
);
113 /* Generate a conditional move of each vector element to the temp. */
114 for (unsigned i
= 0; i
< orig_vector
->type
->vector_elements
; i
++)
115 body
.emit(assign(var
, swizzle(value
, i
, 1), swizzle(cond
, i
, 1)));
117 /* Put all of the new instructions in the IR stream before the old
120 base_ir
->insert_before(&list
);
122 this->progress
= true;
123 return deref(var
).val
;
127 ir_vec_index_to_cond_assign_visitor::convert_vector_extract_to_cond_assign(ir_rvalue
*ir
)
129 ir_expression
*const expr
= ir
->as_expression();
134 if (expr
->operation
== ir_unop_interpolate_at_centroid
||
135 expr
->operation
== ir_binop_interpolate_at_offset
||
136 expr
->operation
== ir_binop_interpolate_at_sample
) {
137 /* Lower interpolateAtXxx(some_vec[idx], ...) to
138 * interpolateAtXxx(some_vec, ...)[idx] before lowering to conditional
139 * assignments, to maintain the rule that the interpolant is an l-value
140 * referring to a (part of a) shader input.
142 * This is required when idx is dynamic (otherwise it gets lowered to
145 ir_expression
*const interpolant
= expr
->operands
[0]->as_expression();
146 if (!interpolant
|| interpolant
->operation
!= ir_binop_vector_extract
)
149 ir_rvalue
*vec_input
= interpolant
->operands
[0];
150 ir_expression
*const vec_interpolate
=
151 new(base_ir
) ir_expression(expr
->operation
, vec_input
->type
,
152 vec_input
, expr
->operands
[1]);
154 return convert_vec_index_to_cond_assign(ralloc_parent(ir
),
156 interpolant
->operands
[1],
160 if (expr
->operation
!= ir_binop_vector_extract
)
163 return convert_vec_index_to_cond_assign(ralloc_parent(ir
),
170 ir_vec_index_to_cond_assign_visitor::visit_enter(ir_expression
*ir
)
172 for (unsigned i
= 0; i
< ir
->num_operands
; i
++)
173 ir
->operands
[i
] = convert_vector_extract_to_cond_assign(ir
->operands
[i
]);
175 return visit_continue
;
179 ir_vec_index_to_cond_assign_visitor::visit_enter(ir_swizzle
*ir
)
181 /* Can't be hit from normal GLSL, since you can't swizzle a scalar (which
182 * the result of indexing a vector is. But maybe at some point we'll end up
183 * using swizzling of scalars for vector construction.
185 ir
->val
= convert_vector_extract_to_cond_assign(ir
->val
);
187 return visit_continue
;
191 ir_vec_index_to_cond_assign_visitor::visit_leave(ir_assignment
*ir
)
193 ir
->rhs
= convert_vector_extract_to_cond_assign(ir
->rhs
);
196 ir
->condition
= convert_vector_extract_to_cond_assign(ir
->condition
);
198 return visit_continue
;
202 ir_vec_index_to_cond_assign_visitor::visit_enter(ir_call
*ir
)
204 foreach_in_list_safe(ir_rvalue
, param
, &ir
->actual_parameters
) {
205 ir_rvalue
*new_param
= convert_vector_extract_to_cond_assign(param
);
207 if (new_param
!= param
) {
208 param
->replace_with(new_param
);
212 return visit_continue
;
216 ir_vec_index_to_cond_assign_visitor::visit_enter(ir_return
*ir
)
219 ir
->value
= convert_vector_extract_to_cond_assign(ir
->value
);
221 return visit_continue
;
225 ir_vec_index_to_cond_assign_visitor::visit_enter(ir_if
*ir
)
227 ir
->condition
= convert_vector_extract_to_cond_assign(ir
->condition
);
229 return visit_continue
;
233 do_vec_index_to_cond_assign(exec_list
*instructions
)
235 ir_vec_index_to_cond_assign_visitor v
;
237 visit_list_elements(&v
, instructions
);