src/glsl/lower_ubo_reference.cpp

   1 /*
   2  * Copyright © 2012 Intel Corporation
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  21  * DEALINGS IN THE SOFTWARE.
  22  */
  23
  24 /**
  25  * \file lower_ubo_reference.cpp
  26  *
  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.
  30  *
  31  * This relieves drivers of the responsibility to deal with tricky UBO
  32  * layout issues like std140 structures and row_major matrices on
  33  * their own.
  34  */
  35
  36 #include "ir.h"
  37 #include "ir_builder.h"
  38 #include "ir_rvalue_visitor.h"
  39 #include "main/macros.h"
  40
  41 using namespace ir_builder;
  42
  43 namespace {
  44 class lower_ubo_reference_visitor : public ir_rvalue_enter_visitor {
  45 public:
  46    lower_ubo_reference_visitor(struct gl_shader *shader)
  47    : shader(shader)
  48    {
  49    }
  50
  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,
  55                            ir_rvalue *offset);
  56
  57    void *mem_ctx;
  58    struct gl_shader *shader;
  59    struct gl_uniform_buffer_variable *ubo_var;
  60    unsigned uniform_block;
  61    bool progress;
  62 };
  63
  64 /**
  65  * Determine the name of the interface block field
  66  *
  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.
  70  */
  71 static const char *
  72 interface_field_name(void *mem_ctx, char *base_name, ir_dereference *d)
  73 {
  74    ir_constant *previous_index = NULL;
  75
  76    while (d != NULL) {
  77       switch (d->ir_type) {
  78       case ir_type_dereference_variable: {
  79          ir_dereference_variable *v = (ir_dereference_variable *) d;
  80          if (previous_index
  81              && v->var->is_interface_instance()
  82              && v->var->type->is_array())
  83             return ralloc_asprintf(mem_ctx,
  84                                    "%s[%d]",
  85                                    base_name,
  86                                    previous_index->get_uint_component(0));
  87          else
  88             return base_name;
  89
  90          break;
  91       }
  92
  93       case ir_type_dereference_record: {
  94          ir_dereference_record *r = (ir_dereference_record *) d;
  95
  96          d = r->record->as_dereference();
  97          break;
  98       }
  99
 100       case ir_type_dereference_array: {
 101          ir_dereference_array *a = (ir_dereference_array *) d;
 102
 103          d = a->array->as_dereference();
 104          previous_index = a->array_index->as_constant();
 105          break;
 106       }
 107
 108       default:
 109          assert(!"Should not get here.");
 110          break;
 111       }
 112    }
 113
 114    assert(!"Should not get here.");
 115    return NULL;
 116 }
 117
 118 void
 119 lower_ubo_reference_visitor::handle_rvalue(ir_rvalue **rvalue)
 120 {
 121    if (!*rvalue)
 122       return;
 123
 124    ir_dereference *deref = (*rvalue)->as_dereference();
 125    if (!deref)
 126       return;
 127
 128    ir_variable *var = deref->variable_referenced();
 129    if (!var || !var->is_in_uniform_block())
 130       return;
 131
 132    mem_ctx = ralloc_parent(*rvalue);
 133
 134    const char *const field_name =
 135       interface_field_name(mem_ctx, (char *) var->interface_type->name, deref);
 136
 137    this->uniform_block = -1;
 138    for (unsigned i = 0; i < shader->NumUniformBlocks; i++) {
 139       if (strcmp(field_name, shader->UniformBlocks[i].Name) == 0) {
 140          this->uniform_block = i;
 141
 142          struct gl_uniform_block *block = &shader->UniformBlocks[i];
 143
 144          this->ubo_var = var->is_interface_instance()
 145             ? &block->Uniforms[0] : &block->Uniforms[var->location];
 146
 147          break;
 148       }
 149    }
 150
 151    assert(this->uniform_block != (unsigned) -1);
 152
 153    ir_rvalue *offset = new(mem_ctx) ir_constant(0u);
 154    unsigned const_offset = 0;
 155    bool row_major = ubo_var->RowMajor;
 156
 157    /* Calculate the offset to the start of the region of the UBO
 158     * dereferenced by *rvalue.  This may be a variable offset if an
 159     * array dereference has a variable index.
 160     */
 161    while (deref) {
 162       switch (deref->ir_type) {
 163       case ir_type_dereference_variable: {
 164          const_offset += ubo_var->Offset;
 165          deref = NULL;
 166          break;
 167       }
 168
 169       case ir_type_dereference_array: {
 170          ir_dereference_array *deref_array = (ir_dereference_array *)deref;
 171          unsigned array_stride;
 172          if (deref_array->array->type->is_matrix() && row_major) {
 173             /* When loading a vector out of a row major matrix, the
 174              * step between the columns (vectors) is the size of a
 175              * float, while the step between the rows (elements of a
 176              * vector) is handled below in emit_ubo_loads.
 177              */
 178             array_stride = 4;
 179          } else if (deref_array->type->is_interface()) {
 180             /* We're processing an array dereference of an interface instance
 181              * array.  The thing being dereferenced *must* be a variable
 182              * dereference because intefaces cannot be embedded an other
 183              * types.  In terms of calculating the offsets for the lowering
 184              * pass, we don't care about the array index.  All elements of an
 185              * interface instance array will have the same offsets relative to
 186              * the base of the block that backs them.
 187              */
 188             assert(deref_array->array->as_dereference_variable());
 189             deref = deref_array->array->as_dereference();
 190             break;
 191          } else {
 192             array_stride = deref_array->type->std140_size(row_major);
 193             array_stride = glsl_align(array_stride, 16);
 194          }
 195
 196          ir_constant *const_index = deref_array->array_index->as_constant();
 197          if (const_index) {
 198             const_offset += array_stride * const_index->value.i[0];
 199          } else {
 200             offset = add(offset,
 201                          mul(deref_array->array_index,
 202                              new(mem_ctx) ir_constant(array_stride)));
 203          }
 204          deref = deref_array->array->as_dereference();
 205          break;
 206       }
 207
 208       case ir_type_dereference_record: {
 209          ir_dereference_record *deref_record = (ir_dereference_record *)deref;
 210          const glsl_type *struct_type = deref_record->record->type;
 211          unsigned intra_struct_offset = 0;
 212
 213          unsigned max_field_align = 16;
 214          for (unsigned int i = 0; i < struct_type->length; i++) {
 215             const glsl_type *type = struct_type->fields.structure[i].type;
 216             unsigned field_align = type->std140_base_alignment(row_major);
 217             max_field_align = MAX2(field_align, max_field_align);
 218             intra_struct_offset = glsl_align(intra_struct_offset, field_align);
 219
 220             if (strcmp(struct_type->fields.structure[i].name,
 221                        deref_record->field) == 0)
 222                break;
 223             intra_struct_offset += type->std140_size(row_major);
 224          }
 225
 226          const_offset = glsl_align(const_offset, max_field_align);
 227          const_offset += intra_struct_offset;
 228
 229          deref = deref_record->record->as_dereference();
 230          break;
 231       }
 232       default:
 233          assert(!"not reached");
 234          deref = NULL;
 235          break;
 236       }
 237    }
 238
 239    /* Now that we've calculated the offset to the start of the
 240     * dereference, walk over the type and emit loads into a temporary.
 241     */
 242    const glsl_type *type = (*rvalue)->type;
 243    ir_variable *load_var = new(mem_ctx) ir_variable(type,
 244                                                     "ubo_load_temp",
 245                                                     ir_var_temporary);
 246    base_ir->insert_before(load_var);
 247
 248    ir_variable *load_offset = new(mem_ctx) ir_variable(glsl_type::uint_type,
 249                                                        "ubo_load_temp_offset",
 250                                                        ir_var_temporary);
 251    base_ir->insert_before(load_offset);
 252    base_ir->insert_before(assign(load_offset, offset));
 253
 254    deref = new(mem_ctx) ir_dereference_variable(load_var);
 255    emit_ubo_loads(deref, load_offset, const_offset);
 256    *rvalue = deref;
 257
 258    progress = true;
 259 }
 260
 261 ir_expression *
 262 lower_ubo_reference_visitor::ubo_load(const glsl_type *type,
 263                                       ir_rvalue *offset)
 264 {
 265    return new(mem_ctx)
 266       ir_expression(ir_binop_ubo_load,
 267                     type,
 268                     new(mem_ctx) ir_constant(this->uniform_block),
 269                     offset);
 270
 271 }
 272
 273 /**
 274  * Takes LHS and emits a series of assignments into its components
 275  * from the UBO variable at variable_offset + deref_offset.
 276  *
 277  * Recursively calls itself to break the deref down to the point that
 278  * the ir_binop_ubo_load expressions generated are contiguous scalars
 279  * or vectors.
 280  */
 281 void
 282 lower_ubo_reference_visitor::emit_ubo_loads(ir_dereference *deref,
 283                                             ir_variable *base_offset,
 284                                             unsigned int deref_offset)
 285 {
 286    if (deref->type->is_record()) {
 287       unsigned int field_offset = 0;
 288
 289       for (unsigned i = 0; i < deref->type->length; i++) {
 290          const struct glsl_struct_field *field =
 291             &deref->type->fields.structure[i];
 292          ir_dereference *field_deref =
 293             new(mem_ctx) ir_dereference_record(deref->clone(mem_ctx, NULL),
 294                                                field->name);
 295
 296          field_offset =
 297             glsl_align(field_offset,
 298                        field->type->std140_base_alignment(ubo_var->RowMajor));
 299
 300          emit_ubo_loads(field_deref, base_offset, deref_offset + field_offset);
 301
 302          field_offset += field->type->std140_size(ubo_var->RowMajor);
 303       }
 304       return;
 305    }
 306
 307    if (deref->type->is_array()) {
 308       unsigned array_stride =
 309          glsl_align(deref->type->fields.array->std140_size(ubo_var->RowMajor),
 310                     16);
 311
 312       for (unsigned i = 0; i < deref->type->length; i++) {
 313          ir_constant *element = new(mem_ctx) ir_constant(i);
 314          ir_dereference *element_deref =
 315             new(mem_ctx) ir_dereference_array(deref->clone(mem_ctx, NULL),
 316                                               element);
 317          emit_ubo_loads(element_deref, base_offset,
 318                         deref_offset + i * array_stride);
 319       }
 320       return;
 321    }
 322
 323    if (deref->type->is_matrix()) {
 324       for (unsigned i = 0; i < deref->type->matrix_columns; i++) {
 325          ir_constant *col = new(mem_ctx) ir_constant(i);
 326          ir_dereference *col_deref =
 327             new(mem_ctx) ir_dereference_array(deref->clone(mem_ctx, NULL),
 328                                               col);
 329
 330          /* std140 always rounds the stride of arrays (and matrices)
 331           * to a vec4, so matrices are always 16 between columns/rows.
 332           */
 333          emit_ubo_loads(col_deref, base_offset, deref_offset + i * 16);
 334       }
 335       return;
 336    }
 337
 338    assert(deref->type->is_scalar() ||
 339           deref->type->is_vector());
 340
 341    if (!ubo_var->RowMajor) {
 342       ir_rvalue *offset = add(base_offset,
 343                               new(mem_ctx) ir_constant(deref_offset));
 344       base_ir->insert_before(assign(deref->clone(mem_ctx, NULL),
 345                                     ubo_load(deref->type, offset)));
 346    } else {
 347       /* We're dereffing a column out of a row-major matrix, so we
 348        * gather the vector from each stored row.
 349       */
 350       assert(deref->type->base_type == GLSL_TYPE_FLOAT);
 351       /* Matrices, row_major or not, are stored as if they were
 352        * arrays of vectors of the appropriate size in std140.
 353        * Arrays have their strides rounded up to a vec4, so the
 354        * matrix stride is always 16.
 355        */
 356       unsigned matrix_stride = 16;
 357
 358       for (unsigned i = 0; i < deref->type->vector_elements; i++) {
 359          ir_rvalue *chan_offset =
 360             add(base_offset,
 361                 new(mem_ctx) ir_constant(deref_offset + i * matrix_stride));
 362
 363          base_ir->insert_before(assign(deref->clone(mem_ctx, NULL),
 364                                        ubo_load(glsl_type::float_type,
 365                                                 chan_offset),
 366                                        (1U << i)));
 367       }
 368    }
 369 }
 370
 371 } /* unnamed namespace */
 372
 373 void
 374 lower_ubo_reference(struct gl_shader *shader, exec_list *instructions)
 375 {
 376    lower_ubo_reference_visitor v(shader);
 377
 378    /* Loop over the instructions lowering references, because we take
 379     * a deref of a UBO array using a UBO dereference as the index will
 380     * produce a collection of instructions all of which have cloned
 381     * UBO dereferences for that array index.
 382     */
 383    do {
 384       v.progress = false;
 385       visit_list_elements(&v, instructions);
 386    } while (v.progress);
 387 }