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25 * \file lower_buffer_access.cpp
27 * Helper for IR lowering pass to replace dereferences of buffer object based
28 * shader variables with intrinsic function calls.
30 * This helper is used by lowering passes for UBOs, SSBOs and compute shader
34 #include "lower_buffer_access.h"
35 #include "ir_builder.h"
36 #include "main/macros.h"
37 #include "util/list.h"
38 #include "glsl_parser_extras.h"
41 using namespace ir_builder
;
43 namespace lower_buffer_access
{
46 writemask_for_size(unsigned n
)
48 return ((1 << n
) - 1);
52 * Takes a deref and recursively calls itself to break the deref down to the
53 * point that the reads or writes generated are contiguous scalars or vectors.
56 lower_buffer_access::emit_access(void *mem_ctx
,
58 ir_dereference
*deref
,
59 ir_variable
*base_offset
,
60 unsigned int deref_offset
,
62 const glsl_type
*matrix_type
,
63 enum glsl_interface_packing packing
,
64 unsigned int write_mask
)
66 if (deref
->type
->is_record()) {
67 unsigned int field_offset
= 0;
69 for (unsigned i
= 0; i
< deref
->type
->length
; i
++) {
70 const struct glsl_struct_field
*field
=
71 &deref
->type
->fields
.structure
[i
];
72 ir_dereference
*field_deref
=
73 new(mem_ctx
) ir_dereference_record(deref
->clone(mem_ctx
, NULL
),
77 if (packing
== GLSL_INTERFACE_PACKING_STD430
)
78 field_align
= field
->type
->std430_base_alignment(row_major
);
80 field_align
= field
->type
->std140_base_alignment(row_major
);
81 field_offset
= glsl_align(field_offset
, field_align
);
83 emit_access(mem_ctx
, is_write
, field_deref
, base_offset
,
84 deref_offset
+ field_offset
,
85 row_major
, NULL
, packing
,
86 writemask_for_size(field_deref
->type
->vector_elements
));
88 if (packing
== GLSL_INTERFACE_PACKING_STD430
)
89 field_offset
+= field
->type
->std430_size(row_major
);
91 field_offset
+= field
->type
->std140_size(row_major
);
96 if (deref
->type
->is_array()) {
97 unsigned array_stride
= packing
== GLSL_INTERFACE_PACKING_STD430
?
98 deref
->type
->fields
.array
->std430_array_stride(row_major
) :
99 glsl_align(deref
->type
->fields
.array
->std140_size(row_major
), 16);
101 for (unsigned i
= 0; i
< deref
->type
->length
; i
++) {
102 ir_constant
*element
= new(mem_ctx
) ir_constant(i
);
103 ir_dereference
*element_deref
=
104 new(mem_ctx
) ir_dereference_array(deref
->clone(mem_ctx
, NULL
),
106 emit_access(mem_ctx
, is_write
, element_deref
, base_offset
,
107 deref_offset
+ i
* array_stride
,
108 row_major
, NULL
, packing
,
109 writemask_for_size(element_deref
->type
->vector_elements
));
114 if (deref
->type
->is_matrix()) {
115 for (unsigned i
= 0; i
< deref
->type
->matrix_columns
; i
++) {
116 ir_constant
*col
= new(mem_ctx
) ir_constant(i
);
117 ir_dereference
*col_deref
=
118 new(mem_ctx
) ir_dereference_array(deref
->clone(mem_ctx
, NULL
), col
);
120 /* For a row-major matrix, the next column starts at the next
121 * element. Otherwise it is offset by the matrix stride.
123 const unsigned size_mul
= row_major
124 ? (deref
->type
->is_double() ? 8 : 4)
125 : link_calculate_matrix_stride(deref
->type
, row_major
, packing
);
127 emit_access(mem_ctx
, is_write
, col_deref
, base_offset
,
128 deref_offset
+ i
* size_mul
,
129 row_major
, deref
->type
, packing
,
130 writemask_for_size(col_deref
->type
->vector_elements
));
135 assert(deref
->type
->is_scalar() || deref
->type
->is_vector());
139 add(base_offset
, new(mem_ctx
) ir_constant(deref_offset
));
141 is_write
? write_mask
: (1 << deref
->type
->vector_elements
) - 1;
142 insert_buffer_access(mem_ctx
, deref
, deref
->type
, offset
, mask
, -1);
144 /* We're dereffing a column out of a row-major matrix, so we
145 * gather the vector from each stored row.
147 assert(deref
->type
->is_float() || deref
->type
->is_double());
148 assert(matrix_type
!= NULL
);
150 const unsigned matrix_stride
=
151 link_calculate_matrix_stride(matrix_type
, row_major
, packing
);
153 const glsl_type
*deref_type
= deref
->type
->get_scalar_type();
155 for (unsigned i
= 0; i
< deref
->type
->vector_elements
; i
++) {
156 ir_rvalue
*chan_offset
=
158 new(mem_ctx
) ir_constant(deref_offset
+ i
* matrix_stride
));
159 if (!is_write
|| ((1U << i
) & write_mask
))
160 insert_buffer_access(mem_ctx
, deref
, deref_type
, chan_offset
,
167 * Determine if a thing being dereferenced is row-major
169 * There is some trickery here.
171 * If the thing being dereferenced is a member of uniform block \b without an
172 * instance name, then the name of the \c ir_variable is the field name of an
173 * interface type. If this field is row-major, then the thing referenced is
176 * If the thing being dereferenced is a member of uniform block \b with an
177 * instance name, then the last dereference in the tree will be an
178 * \c ir_dereference_record. If that record field is row-major, then the
179 * thing referenced is row-major.
182 lower_buffer_access::is_dereferenced_thing_row_major(const ir_rvalue
*deref
)
185 const ir_rvalue
*ir
= deref
;
188 matrix
= matrix
|| ir
->type
->without_array()->is_matrix();
190 switch (ir
->ir_type
) {
191 case ir_type_dereference_array
: {
192 const ir_dereference_array
*const array_deref
=
193 (const ir_dereference_array
*) ir
;
195 ir
= array_deref
->array
;
199 case ir_type_dereference_record
: {
200 const ir_dereference_record
*const record_deref
=
201 (const ir_dereference_record
*) ir
;
203 ir
= record_deref
->record
;
205 const int idx
= record_deref
->field_idx
;
208 const enum glsl_matrix_layout matrix_layout
=
209 glsl_matrix_layout(ir
->type
->fields
.structure
[idx
].matrix_layout
);
211 switch (matrix_layout
) {
212 case GLSL_MATRIX_LAYOUT_INHERITED
:
214 case GLSL_MATRIX_LAYOUT_COLUMN_MAJOR
:
216 case GLSL_MATRIX_LAYOUT_ROW_MAJOR
:
217 return matrix
|| deref
->type
->without_array()->is_record();
223 case ir_type_dereference_variable
: {
224 const ir_dereference_variable
*const var_deref
=
225 (const ir_dereference_variable
*) ir
;
227 const enum glsl_matrix_layout matrix_layout
=
228 glsl_matrix_layout(var_deref
->var
->data
.matrix_layout
);
230 switch (matrix_layout
) {
231 case GLSL_MATRIX_LAYOUT_INHERITED
: {
232 /* For interface block matrix variables we handle inherited
233 * layouts at HIR generation time, but we don't do that for shared
234 * variables, which are always column-major
236 MAYBE_UNUSED ir_variable
*var
= deref
->variable_referenced();
237 assert((var
->is_in_buffer_block() && !matrix
) ||
238 var
->data
.mode
== ir_var_shader_shared
);
241 case GLSL_MATRIX_LAYOUT_COLUMN_MAJOR
:
243 case GLSL_MATRIX_LAYOUT_ROW_MAJOR
:
244 return matrix
|| deref
->type
->without_array()->is_record();
247 unreachable("invalid matrix layout");
256 /* The tree must have ended with a dereference that wasn't an
257 * ir_dereference_variable. That is invalid, and it should be impossible.
259 unreachable("invalid dereference tree");
264 * This function initializes various values that will be used later by
265 * emit_access when actually emitting loads or stores.
267 * Note: const_offset is an input as well as an output, clients must
268 * initialize it to the offset of the variable in the underlying block, and
269 * this function will adjust it by adding the constant offset of the member
270 * being accessed into that variable.
273 lower_buffer_access::setup_buffer_access(void *mem_ctx
,
276 unsigned *const_offset
,
278 const glsl_type
**matrix_type
,
279 const glsl_struct_field
**struct_field
,
280 enum glsl_interface_packing packing
)
282 *offset
= new(mem_ctx
) ir_constant(0u);
283 *row_major
= is_dereferenced_thing_row_major(deref
);
286 /* Calculate the offset to the start of the region of the UBO
287 * dereferenced by *rvalue. This may be a variable offset if an
288 * array dereference has a variable index.
291 switch (deref
->ir_type
) {
292 case ir_type_dereference_variable
: {
297 case ir_type_dereference_array
: {
298 ir_dereference_array
*deref_array
= (ir_dereference_array
*) deref
;
299 unsigned array_stride
;
300 if (deref_array
->array
->type
->is_vector()) {
301 /* We get this when storing or loading a component out of a vector
302 * with a non-constant index. This happens for v[i] = f where v is
303 * a vector (or m[i][j] = f where m is a matrix). If we don't
304 * lower that here, it gets turned into v = vector_insert(v, i,
305 * f), which loads the entire vector, modifies one component and
306 * then write the entire thing back. That breaks if another
307 * thread or SIMD channel is modifying the same vector.
310 if (deref_array
->array
->type
->is_64bit())
312 } else if (deref_array
->array
->type
->is_matrix() && *row_major
) {
313 /* When loading a vector out of a row major matrix, the
314 * step between the columns (vectors) is the size of a
315 * float, while the step between the rows (elements of a
316 * vector) is handled below in emit_ubo_loads.
319 if (deref_array
->array
->type
->is_64bit())
321 *matrix_type
= deref_array
->array
->type
;
322 } else if (deref_array
->type
->without_array()->is_interface()) {
323 /* We're processing an array dereference of an interface instance
324 * array. The thing being dereferenced *must* be a variable
325 * dereference because interfaces cannot be embedded in other
326 * types. In terms of calculating the offsets for the lowering
327 * pass, we don't care about the array index. All elements of an
328 * interface instance array will have the same offsets relative to
329 * the base of the block that backs them.
331 deref
= deref_array
->array
->as_dereference();
334 /* Whether or not the field is row-major (because it might be a
335 * bvec2 or something) does not affect the array itself. We need
336 * to know whether an array element in its entirety is row-major.
338 const bool array_row_major
=
339 is_dereferenced_thing_row_major(deref_array
);
341 /* The array type will give the correct interface packing
344 if (packing
== GLSL_INTERFACE_PACKING_STD430
) {
345 array_stride
= deref_array
->type
->std430_array_stride(array_row_major
);
347 array_stride
= deref_array
->type
->std140_size(array_row_major
);
348 array_stride
= glsl_align(array_stride
, 16);
352 ir_rvalue
*array_index
= deref_array
->array_index
;
353 if (array_index
->type
->base_type
== GLSL_TYPE_INT
)
354 array_index
= i2u(array_index
);
356 ir_constant
*const_index
=
357 array_index
->constant_expression_value(mem_ctx
, NULL
);
359 *const_offset
+= array_stride
* const_index
->value
.u
[0];
361 *offset
= add(*offset
,
363 new(mem_ctx
) ir_constant(array_stride
)));
365 deref
= deref_array
->array
->as_dereference();
369 case ir_type_dereference_record
: {
370 ir_dereference_record
*deref_record
= (ir_dereference_record
*) deref
;
371 const glsl_type
*struct_type
= deref_record
->record
->type
;
372 unsigned intra_struct_offset
= 0;
374 for (unsigned int i
= 0; i
< struct_type
->length
; i
++) {
375 const glsl_type
*type
= struct_type
->fields
.structure
[i
].type
;
377 ir_dereference_record
*field_deref
= new(mem_ctx
)
378 ir_dereference_record(deref_record
->record
,
379 struct_type
->fields
.structure
[i
].name
);
380 const bool field_row_major
=
381 is_dereferenced_thing_row_major(field_deref
);
383 ralloc_free(field_deref
);
385 unsigned field_align
= 0;
387 if (packing
== GLSL_INTERFACE_PACKING_STD430
)
388 field_align
= type
->std430_base_alignment(field_row_major
);
390 field_align
= type
->std140_base_alignment(field_row_major
);
392 if (struct_type
->fields
.structure
[i
].offset
!= -1) {
393 intra_struct_offset
= struct_type
->fields
.structure
[i
].offset
;
396 intra_struct_offset
= glsl_align(intra_struct_offset
, field_align
);
398 assert(deref_record
->field_idx
>= 0);
399 if (i
== (unsigned) deref_record
->field_idx
) {
401 *struct_field
= &struct_type
->fields
.structure
[i
];
405 if (packing
== GLSL_INTERFACE_PACKING_STD430
)
406 intra_struct_offset
+= type
->std430_size(field_row_major
);
408 intra_struct_offset
+= type
->std140_size(field_row_major
);
410 /* If the field just examined was itself a structure, apply rule
413 * "The structure may have padding at the end; the base offset
414 * of the member following the sub-structure is rounded up to
415 * the next multiple of the base alignment of the structure."
417 if (type
->without_array()->is_record()) {
418 intra_struct_offset
= glsl_align(intra_struct_offset
,
424 *const_offset
+= intra_struct_offset
;
425 deref
= deref_record
->record
->as_dereference();
429 case ir_type_swizzle
: {
430 ir_swizzle
*deref_swizzle
= (ir_swizzle
*) deref
;
432 assert(deref_swizzle
->mask
.num_components
== 1);
434 *const_offset
+= deref_swizzle
->mask
.x
* sizeof(int);
435 deref
= deref_swizzle
->val
->as_dereference();
440 assert(!"not reached");
447 } /* namespace lower_buffer_access */