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 void
  65 lower_ubo_reference_visitor::handle_rvalue(ir_rvalue **rvalue)
  66 {
  67    if (!*rvalue)
  68       return;
  69
  70    ir_dereference *deref = (*rvalue)->as_dereference();
  71    if (!deref)
  72       return;
  73
  74    ir_variable *var = deref->variable_referenced();
  75    if (!var || !var->is_in_uniform_block())
  76       return;
  77
  78    mem_ctx = ralloc_parent(*rvalue);
  79    uniform_block = var->uniform_block;
  80    struct gl_uniform_block *block = &shader->UniformBlocks[uniform_block];
  81    this->ubo_var = &block->Uniforms[var->location];
  82    ir_rvalue *offset = new(mem_ctx) ir_constant(0u);
  83    unsigned const_offset = 0;
  84    bool row_major = ubo_var->RowMajor;
  85
  86    /* Calculate the offset to the start of the region of the UBO
  87     * dereferenced by *rvalue.  This may be a variable offset if an
  88     * array dereference has a variable index.
  89     */
  90    while (deref) {
  91       switch (deref->ir_type) {
  92       case ir_type_dereference_variable: {
  93          const_offset += ubo_var->Offset;
  94          deref = NULL;
  95          break;
  96       }
  97
  98       case ir_type_dereference_array: {
  99          ir_dereference_array *deref_array = (ir_dereference_array *)deref;
 100          unsigned array_stride;
 101          if (deref_array->array->type->is_matrix() && row_major) {
 102             /* When loading a vector out of a row major matrix, the
 103              * step between the columns (vectors) is the size of a
 104              * float, while the step between the rows (elements of a
 105              * vector) is handled below in emit_ubo_loads.
 106              */
 107             array_stride = 4;
 108          } else {
 109             array_stride = deref_array->type->std140_size(row_major);
 110             array_stride = glsl_align(array_stride, 16);
 111          }
 112
 113          ir_constant *const_index = deref_array->array_index->as_constant();
 114          if (const_index) {
 115             const_offset += array_stride * const_index->value.i[0];
 116          } else {
 117             offset = add(offset,
 118                          mul(deref_array->array_index,
 119                              new(mem_ctx) ir_constant(array_stride)));
 120          }
 121          deref = deref_array->array->as_dereference();
 122          break;
 123       }
 124
 125       case ir_type_dereference_record: {
 126          ir_dereference_record *deref_record = (ir_dereference_record *)deref;
 127          const glsl_type *struct_type = deref_record->record->type;
 128          unsigned intra_struct_offset = 0;
 129
 130          unsigned max_field_align = 16;
 131          for (unsigned int i = 0; i < struct_type->length; i++) {
 132             const glsl_type *type = struct_type->fields.structure[i].type;
 133             unsigned field_align = type->std140_base_alignment(row_major);
 134             max_field_align = MAX2(field_align, max_field_align);
 135             intra_struct_offset = glsl_align(intra_struct_offset, field_align);
 136
 137             if (strcmp(struct_type->fields.structure[i].name,
 138                        deref_record->field) == 0)
 139                break;
 140             intra_struct_offset += type->std140_size(row_major);
 141          }
 142
 143          const_offset = glsl_align(const_offset, max_field_align);
 144          const_offset += intra_struct_offset;
 145
 146          deref = deref_record->record->as_dereference();
 147          break;
 148       }
 149       default:
 150          assert(!"not reached");
 151          deref = NULL;
 152          break;
 153       }
 154    }
 155
 156    /* Now that we've calculated the offset to the start of the
 157     * dereference, walk over the type and emit loads into a temporary.
 158     */
 159    const glsl_type *type = (*rvalue)->type;
 160    ir_variable *load_var = new(mem_ctx) ir_variable(type,
 161                                                     "ubo_load_temp",
 162                                                     ir_var_temporary);
 163    base_ir->insert_before(load_var);
 164
 165    ir_variable *load_offset = new(mem_ctx) ir_variable(glsl_type::uint_type,
 166                                                        "ubo_load_temp_offset",
 167                                                        ir_var_temporary);
 168    base_ir->insert_before(load_offset);
 169    base_ir->insert_before(assign(load_offset, offset));
 170
 171    deref = new(mem_ctx) ir_dereference_variable(load_var);
 172    emit_ubo_loads(deref, load_offset, const_offset);
 173    *rvalue = deref;
 174
 175    progress = true;
 176 }
 177
 178 ir_expression *
 179 lower_ubo_reference_visitor::ubo_load(const glsl_type *type,
 180                                       ir_rvalue *offset)
 181 {
 182    return new(mem_ctx)
 183       ir_expression(ir_binop_ubo_load,
 184                     type,
 185                     new(mem_ctx) ir_constant(this->uniform_block),
 186                     offset);
 187
 188 }
 189
 190 /**
 191  * Takes LHS and emits a series of assignments into its components
 192  * from the UBO variable at variable_offset + deref_offset.
 193  *
 194  * Recursively calls itself to break the deref down to the point that
 195  * the ir_binop_ubo_load expressions generated are contiguous scalars
 196  * or vectors.
 197  */
 198 void
 199 lower_ubo_reference_visitor::emit_ubo_loads(ir_dereference *deref,
 200                                             ir_variable *base_offset,
 201                                             unsigned int deref_offset)
 202 {
 203    if (deref->type->is_record()) {
 204       unsigned int field_offset = 0;
 205
 206       for (unsigned i = 0; i < deref->type->length; i++) {
 207          const struct glsl_struct_field *field =
 208             &deref->type->fields.structure[i];
 209          ir_dereference *field_deref =
 210             new(mem_ctx) ir_dereference_record(deref->clone(mem_ctx, NULL),
 211                                                field->name);
 212
 213          field_offset =
 214             glsl_align(field_offset,
 215                        field->type->std140_base_alignment(ubo_var->RowMajor));
 216
 217          emit_ubo_loads(field_deref, base_offset, deref_offset + field_offset);
 218
 219          field_offset += field->type->std140_size(ubo_var->RowMajor);
 220       }
 221       return;
 222    }
 223
 224    if (deref->type->is_array()) {
 225       unsigned array_stride =
 226          glsl_align(deref->type->fields.array->std140_size(ubo_var->RowMajor),
 227                     16);
 228
 229       for (unsigned i = 0; i < deref->type->length; i++) {
 230          ir_constant *element = new(mem_ctx) ir_constant(i);
 231          ir_dereference *element_deref =
 232             new(mem_ctx) ir_dereference_array(deref->clone(mem_ctx, NULL),
 233                                               element);
 234          emit_ubo_loads(element_deref, base_offset,
 235                         deref_offset + i * array_stride);
 236       }
 237       return;
 238    }
 239
 240    if (deref->type->is_matrix()) {
 241       for (unsigned i = 0; i < deref->type->matrix_columns; i++) {
 242          ir_constant *col = new(mem_ctx) ir_constant(i);
 243          ir_dereference *col_deref =
 244             new(mem_ctx) ir_dereference_array(deref->clone(mem_ctx, NULL),
 245                                               col);
 246
 247          /* std140 always rounds the stride of arrays (and matrices)
 248           * to a vec4, so matrices are always 16 between columns/rows.
 249           */
 250          emit_ubo_loads(col_deref, base_offset, deref_offset + i * 16);
 251       }
 252       return;
 253    }
 254
 255    assert(deref->type->is_scalar() ||
 256           deref->type->is_vector());
 257
 258    if (!ubo_var->RowMajor) {
 259       ir_rvalue *offset = add(base_offset,
 260                               new(mem_ctx) ir_constant(deref_offset));
 261       base_ir->insert_before(assign(deref->clone(mem_ctx, NULL),
 262                                     ubo_load(deref->type, offset)));
 263    } else {
 264       /* We're dereffing a column out of a row-major matrix, so we
 265        * gather the vector from each stored row.
 266       */
 267       assert(deref->type->base_type == GLSL_TYPE_FLOAT);
 268       /* Matrices, row_major or not, are stored as if they were
 269        * arrays of vectors of the appropriate size in std140.
 270        * Arrays have their strides rounded up to a vec4, so the
 271        * matrix stride is always 16.
 272        */
 273       unsigned matrix_stride = 16;
 274
 275       for (unsigned i = 0; i < deref->type->vector_elements; i++) {
 276          ir_rvalue *chan = new(mem_ctx) ir_constant((int)i);
 277          ir_dereference *deref_chan =
 278             new(mem_ctx) ir_dereference_array(deref->clone(mem_ctx, NULL),
 279                                               chan);
 280
 281          ir_rvalue *chan_offset =
 282             add(base_offset,
 283                 new(mem_ctx) ir_constant(deref_offset + i * matrix_stride));
 284
 285          base_ir->insert_before(assign(deref_chan,
 286                                        ubo_load(glsl_type::float_type,
 287                                                 chan_offset)));
 288       }
 289    }
 290 }
 291
 292 } /* unnamed namespace */
 293
 294 void
 295 lower_ubo_reference(struct gl_shader *shader, exec_list *instructions)
 296 {
 297    lower_ubo_reference_visitor v(shader);
 298
 299    /* Loop over the instructions lowering references, because we take
 300     * a deref of a UBO array using a UBO dereference as the index will
 301     * produce a collection of instructions all of which have cloned
 302     * UBO dereferences for that array index.
 303     */
 304    do {
 305       v.progress = false;
 306       visit_list_elements(&v, instructions);
 307    } while (v.progress);
 308 }