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25 * \file lower_ubo_reference.cpp
27 * IR lower pass to replace dereferences of variables in a uniform
28 * buffer object with usage of ir_binop_ubo_load expressions, each of
29 * which can read data up to the size of a vec4.
31 * This relieves drivers of the responsibility to deal with tricky UBO
32 * layout issues like std140 structures and row_major matrices on
37 #include "ir_builder.h"
38 #include "ir_rvalue_visitor.h"
39 #include "main/macros.h"
41 using namespace ir_builder
;
44 class lower_ubo_reference_visitor
: public ir_rvalue_enter_visitor
{
46 lower_ubo_reference_visitor(struct gl_shader
*shader
)
51 void handle_rvalue(ir_rvalue
**rvalue
);
52 void emit_ubo_loads(ir_dereference
*deref
, ir_variable
*base_offset
,
53 unsigned int deref_offset
);
54 ir_expression
*ubo_load(const struct glsl_type
*type
,
58 struct gl_shader
*shader
;
59 struct gl_uniform_buffer_variable
*ubo_var
;
60 unsigned uniform_block
;
65 * Determine the name of the interface block field
67 * This is the name of the specific member as it would appear in the
68 * \c gl_uniform_buffer_variable::Name field in the shader's
69 * \c UniformBlocks array.
72 interface_field_name(void *mem_ctx
, char *base_name
, ir_dereference
*d
)
74 ir_constant
*previous_index
= NULL
;
78 case ir_type_dereference_variable
: {
79 ir_dereference_variable
*v
= (ir_dereference_variable
*) d
;
81 && v
->var
->is_interface_instance()
82 && v
->var
->type
->is_array())
83 return ralloc_asprintf(mem_ctx
,
86 previous_index
->get_uint_component(0));
93 case ir_type_dereference_record
: {
94 ir_dereference_record
*r
= (ir_dereference_record
*) d
;
96 d
= r
->record
->as_dereference();
100 case ir_type_dereference_array
: {
101 ir_dereference_array
*a
= (ir_dereference_array
*) d
;
103 d
= a
->array
->as_dereference();
104 previous_index
= a
->array_index
->as_constant();
109 assert(!"Should not get here.");
114 assert(!"Should not get here.");
119 lower_ubo_reference_visitor::handle_rvalue(ir_rvalue
**rvalue
)
124 ir_dereference
*deref
= (*rvalue
)->as_dereference();
128 ir_variable
*var
= deref
->variable_referenced();
129 if (!var
|| !var
->is_in_uniform_block())
132 mem_ctx
= ralloc_parent(*rvalue
);
134 const char *const field_name
=
135 interface_field_name(mem_ctx
, (char *) var
->get_interface_type()->name
,
138 this->uniform_block
= -1;
139 for (unsigned i
= 0; i
< shader
->NumUniformBlocks
; i
++) {
140 if (strcmp(field_name
, shader
->UniformBlocks
[i
].Name
) == 0) {
141 this->uniform_block
= i
;
143 struct gl_uniform_block
*block
= &shader
->UniformBlocks
[i
];
145 this->ubo_var
= var
->is_interface_instance()
146 ? &block
->Uniforms
[0] : &block
->Uniforms
[var
->data
.location
];
152 assert(this->uniform_block
!= (unsigned) -1);
154 ir_rvalue
*offset
= new(mem_ctx
) ir_constant(0u);
155 unsigned const_offset
= 0;
156 bool row_major
= ubo_var
->RowMajor
;
158 /* Calculate the offset to the start of the region of the UBO
159 * dereferenced by *rvalue. This may be a variable offset if an
160 * array dereference has a variable index.
163 switch (deref
->ir_type
) {
164 case ir_type_dereference_variable
: {
165 const_offset
+= ubo_var
->Offset
;
170 case ir_type_dereference_array
: {
171 ir_dereference_array
*deref_array
= (ir_dereference_array
*)deref
;
172 unsigned array_stride
;
173 if (deref_array
->array
->type
->is_matrix() && row_major
) {
174 /* When loading a vector out of a row major matrix, the
175 * step between the columns (vectors) is the size of a
176 * float, while the step between the rows (elements of a
177 * vector) is handled below in emit_ubo_loads.
180 } else if (deref_array
->type
->is_interface()) {
181 /* We're processing an array dereference of an interface instance
182 * array. The thing being dereferenced *must* be a variable
183 * dereference because intefaces cannot be embedded an other
184 * types. In terms of calculating the offsets for the lowering
185 * pass, we don't care about the array index. All elements of an
186 * interface instance array will have the same offsets relative to
187 * the base of the block that backs them.
189 assert(deref_array
->array
->as_dereference_variable());
190 deref
= deref_array
->array
->as_dereference();
193 array_stride
= deref_array
->type
->std140_size(row_major
);
194 array_stride
= glsl_align(array_stride
, 16);
197 ir_constant
*const_index
= deref_array
->array_index
->as_constant();
199 const_offset
+= array_stride
* const_index
->value
.i
[0];
202 mul(deref_array
->array_index
,
203 new(mem_ctx
) ir_constant(array_stride
)));
205 deref
= deref_array
->array
->as_dereference();
209 case ir_type_dereference_record
: {
210 ir_dereference_record
*deref_record
= (ir_dereference_record
*)deref
;
211 const glsl_type
*struct_type
= deref_record
->record
->type
;
212 unsigned intra_struct_offset
= 0;
214 unsigned max_field_align
= 16;
215 for (unsigned int i
= 0; i
< struct_type
->length
; i
++) {
216 const glsl_type
*type
= struct_type
->fields
.structure
[i
].type
;
217 unsigned field_align
= type
->std140_base_alignment(row_major
);
218 max_field_align
= MAX2(field_align
, max_field_align
);
219 intra_struct_offset
= glsl_align(intra_struct_offset
, field_align
);
221 if (strcmp(struct_type
->fields
.structure
[i
].name
,
222 deref_record
->field
) == 0)
224 intra_struct_offset
+= type
->std140_size(row_major
);
227 const_offset
= glsl_align(const_offset
, max_field_align
);
228 const_offset
+= intra_struct_offset
;
230 deref
= deref_record
->record
->as_dereference();
234 assert(!"not reached");
240 /* Now that we've calculated the offset to the start of the
241 * dereference, walk over the type and emit loads into a temporary.
243 const glsl_type
*type
= (*rvalue
)->type
;
244 ir_variable
*load_var
= new(mem_ctx
) ir_variable(type
,
247 base_ir
->insert_before(load_var
);
249 ir_variable
*load_offset
= new(mem_ctx
) ir_variable(glsl_type::uint_type
,
250 "ubo_load_temp_offset",
252 base_ir
->insert_before(load_offset
);
253 base_ir
->insert_before(assign(load_offset
, offset
));
255 deref
= new(mem_ctx
) ir_dereference_variable(load_var
);
256 emit_ubo_loads(deref
, load_offset
, const_offset
);
263 lower_ubo_reference_visitor::ubo_load(const glsl_type
*type
,
267 ir_expression(ir_binop_ubo_load
,
269 new(mem_ctx
) ir_constant(this->uniform_block
),
275 * Takes LHS and emits a series of assignments into its components
276 * from the UBO variable at variable_offset + deref_offset.
278 * Recursively calls itself to break the deref down to the point that
279 * the ir_binop_ubo_load expressions generated are contiguous scalars
283 lower_ubo_reference_visitor::emit_ubo_loads(ir_dereference
*deref
,
284 ir_variable
*base_offset
,
285 unsigned int deref_offset
)
287 if (deref
->type
->is_record()) {
288 unsigned int field_offset
= 0;
290 for (unsigned i
= 0; i
< deref
->type
->length
; i
++) {
291 const struct glsl_struct_field
*field
=
292 &deref
->type
->fields
.structure
[i
];
293 ir_dereference
*field_deref
=
294 new(mem_ctx
) ir_dereference_record(deref
->clone(mem_ctx
, NULL
),
298 glsl_align(field_offset
,
299 field
->type
->std140_base_alignment(ubo_var
->RowMajor
));
301 emit_ubo_loads(field_deref
, base_offset
, deref_offset
+ field_offset
);
303 field_offset
+= field
->type
->std140_size(ubo_var
->RowMajor
);
308 if (deref
->type
->is_array()) {
309 unsigned array_stride
=
310 glsl_align(deref
->type
->fields
.array
->std140_size(ubo_var
->RowMajor
),
313 for (unsigned i
= 0; i
< deref
->type
->length
; i
++) {
314 ir_constant
*element
= new(mem_ctx
) ir_constant(i
);
315 ir_dereference
*element_deref
=
316 new(mem_ctx
) ir_dereference_array(deref
->clone(mem_ctx
, NULL
),
318 emit_ubo_loads(element_deref
, base_offset
,
319 deref_offset
+ i
* array_stride
);
324 if (deref
->type
->is_matrix()) {
325 for (unsigned i
= 0; i
< deref
->type
->matrix_columns
; i
++) {
326 ir_constant
*col
= new(mem_ctx
) ir_constant(i
);
327 ir_dereference
*col_deref
=
328 new(mem_ctx
) ir_dereference_array(deref
->clone(mem_ctx
, NULL
),
331 /* std140 always rounds the stride of arrays (and matrices)
332 * to a vec4, so matrices are always 16 between columns/rows.
334 emit_ubo_loads(col_deref
, base_offset
, deref_offset
+ i
* 16);
339 assert(deref
->type
->is_scalar() ||
340 deref
->type
->is_vector());
342 if (!ubo_var
->RowMajor
) {
343 ir_rvalue
*offset
= add(base_offset
,
344 new(mem_ctx
) ir_constant(deref_offset
));
345 base_ir
->insert_before(assign(deref
->clone(mem_ctx
, NULL
),
346 ubo_load(deref
->type
, offset
)));
348 /* We're dereffing a column out of a row-major matrix, so we
349 * gather the vector from each stored row.
351 assert(deref
->type
->base_type
== GLSL_TYPE_FLOAT
);
352 /* Matrices, row_major or not, are stored as if they were
353 * arrays of vectors of the appropriate size in std140.
354 * Arrays have their strides rounded up to a vec4, so the
355 * matrix stride is always 16.
357 unsigned matrix_stride
= 16;
359 for (unsigned i
= 0; i
< deref
->type
->vector_elements
; i
++) {
360 ir_rvalue
*chan_offset
=
362 new(mem_ctx
) ir_constant(deref_offset
+ i
* matrix_stride
));
364 base_ir
->insert_before(assign(deref
->clone(mem_ctx
, NULL
),
365 ubo_load(glsl_type::float_type
,
372 } /* unnamed namespace */
375 lower_ubo_reference(struct gl_shader
*shader
, exec_list
*instructions
)
377 lower_ubo_reference_visitor
v(shader
);
379 /* Loop over the instructions lowering references, because we take
380 * a deref of a UBO array using a UBO dereference as the index will
381 * produce a collection of instructions all of which have cloned
382 * UBO dereferences for that array index.
386 visit_list_elements(&v
, instructions
);
387 } while (v
.progress
);