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 static inline unsigned int
  65 align(unsigned int a, unsigned int align)
  66 {
  67    return (a + align - 1) / align * align;
  68 }
  69
  70 void
  71 lower_ubo_reference_visitor::handle_rvalue(ir_rvalue **rvalue)
  72 {
  73    if (!*rvalue)
  74       return;
  75
  76    ir_dereference *deref = (*rvalue)->as_dereference();
  77    if (!deref)
  78       return;
  79
  80    ir_variable *var = deref->variable_referenced();
  81    if (!var || var->uniform_block == -1)
  82       return;
  83
  84    mem_ctx = ralloc_parent(*rvalue);
  85    uniform_block = var->uniform_block;
  86    struct gl_uniform_block *block = &shader->UniformBlocks[uniform_block];
  87    this->ubo_var = &block->Uniforms[var->location];
  88    ir_rvalue *offset = new(mem_ctx) ir_constant(0u);
  89    unsigned const_offset = 0;
  90    bool row_major = ubo_var->RowMajor;
  91
  92    /* Calculate the offset to the start of the region of the UBO
  93     * dereferenced by *rvalue.  This may be a variable offset if an
  94     * array dereference has a variable index.
  95     */
  96    while (deref) {
  97       switch (deref->ir_type) {
  98       case ir_type_dereference_variable: {
  99          const_offset += ubo_var->Offset;
 100          deref = NULL;
 101          break;
 102       }
 103
 104       case ir_type_dereference_array: {
 105          ir_dereference_array *deref_array = (ir_dereference_array *)deref;
 106          unsigned array_stride;
 107          if (deref_array->array->type->is_matrix() && row_major) {
 108             /* When loading a vector out of a row major matrix, the
 109              * step between the columns (vectors) is the size of a
 110              * float, while the step between the rows (elements of a
 111              * vector) is handled below in emit_ubo_loads.
 112              */
 113             array_stride = 4;
 114          } else {
 115             array_stride = deref_array->type->std140_size(row_major);
 116             array_stride = align(array_stride, 16);
 117          }
 118
 119          ir_constant *const_index = deref_array->array_index->as_constant();
 120          if (const_index) {
 121             const_offset += array_stride * const_index->value.i[0];
 122          } else {
 123             offset = add(offset,
 124                          mul(deref_array->array_index,
 125                              new(mem_ctx) ir_constant(array_stride)));
 126          }
 127          deref = deref_array->array->as_dereference();
 128          break;
 129       }
 130
 131       case ir_type_dereference_record: {
 132          ir_dereference_record *deref_record = (ir_dereference_record *)deref;
 133          const glsl_type *struct_type = deref_record->record->type;
 134          unsigned intra_struct_offset = 0;
 135
 136          unsigned max_field_align = 16;
 137          for (unsigned int i = 0; i < struct_type->length; i++) {
 138             const glsl_type *type = struct_type->fields.structure[i].type;
 139             unsigned field_align = type->std140_base_alignment(row_major);
 140             max_field_align = MAX2(field_align, max_field_align);
 141             intra_struct_offset = align(intra_struct_offset, field_align);
 142
 143             if (strcmp(struct_type->fields.structure[i].name,
 144                        deref_record->field) == 0)
 145                break;
 146             intra_struct_offset += type->std140_size(row_major);
 147          }
 148
 149          const_offset = align(const_offset, max_field_align);
 150          const_offset += intra_struct_offset;
 151
 152          deref = deref_record->record->as_dereference();
 153          break;
 154       }
 155       default:
 156          assert(!"not reached");
 157          deref = NULL;
 158          break;
 159       }
 160    }
 161
 162    /* Now that we've calculated the offset to the start of the
 163     * dereference, walk over the type and emit loads into a temporary.
 164     */
 165    const glsl_type *type = (*rvalue)->type;
 166    ir_variable *load_var = new(mem_ctx) ir_variable(type,
 167                                                     "ubo_load_temp",
 168                                                     ir_var_temporary);
 169    base_ir->insert_before(load_var);
 170
 171    ir_variable *load_offset = new(mem_ctx) ir_variable(glsl_type::uint_type,
 172                                                        "ubo_load_temp_offset",
 173                                                        ir_var_temporary);
 174    base_ir->insert_before(load_offset);
 175    base_ir->insert_before(assign(load_offset, offset));
 176
 177    deref = new(mem_ctx) ir_dereference_variable(load_var);
 178    emit_ubo_loads(deref, load_offset, const_offset);
 179    *rvalue = deref;
 180
 181    progress = true;
 182 }
 183
 184 ir_expression *
 185 lower_ubo_reference_visitor::ubo_load(const glsl_type *type,
 186                                       ir_rvalue *offset)
 187 {
 188    return new(mem_ctx)
 189       ir_expression(ir_binop_ubo_load,
 190                     type,
 191                     new(mem_ctx) ir_constant(this->uniform_block),
 192                     offset);
 193
 194 }
 195
 196 /**
 197  * Takes LHS and emits a series of assignments into its components
 198  * from the UBO variable at variable_offset + deref_offset.
 199  *
 200  * Recursively calls itself to break the deref down to the point that
 201  * the ir_binop_ubo_load expressions generated are contiguous scalars
 202  * or vectors.
 203  */
 204 void
 205 lower_ubo_reference_visitor::emit_ubo_loads(ir_dereference *deref,
 206                                             ir_variable *base_offset,
 207                                             unsigned int deref_offset)
 208 {
 209    if (deref->type->is_record()) {
 210       unsigned int field_offset = 0;
 211
 212       for (unsigned i = 0; i < deref->type->length; i++) {
 213          const struct glsl_struct_field *field =
 214             &deref->type->fields.structure[i];
 215          ir_dereference *field_deref =
 216             new(mem_ctx) ir_dereference_record(deref->clone(mem_ctx, NULL),
 217                                                field->name);
 218
 219          field_offset =
 220             align(field_offset,
 221                   field->type->std140_base_alignment(ubo_var->RowMajor));
 222
 223          emit_ubo_loads(field_deref, base_offset, deref_offset + field_offset);
 224
 225          field_offset += field->type->std140_size(ubo_var->RowMajor);
 226       }
 227       return;
 228    }
 229
 230    if (deref->type->is_array()) {
 231       unsigned array_stride =
 232          align(deref->type->fields.array->std140_size(ubo_var->RowMajor), 16);
 233
 234       for (unsigned i = 0; i < deref->type->length; i++) {
 235          ir_constant *element = new(mem_ctx) ir_constant(i);
 236          ir_dereference *element_deref =
 237             new(mem_ctx) ir_dereference_array(deref->clone(mem_ctx, NULL),
 238                                               element);
 239          emit_ubo_loads(element_deref, base_offset,
 240                         deref_offset + i * array_stride);
 241       }
 242       return;
 243    }
 244
 245    if (deref->type->is_matrix()) {
 246       for (unsigned i = 0; i < deref->type->matrix_columns; i++) {
 247          ir_constant *col = new(mem_ctx) ir_constant(i);
 248          ir_dereference *col_deref =
 249             new(mem_ctx) ir_dereference_array(deref->clone(mem_ctx, NULL),
 250                                               col);
 251
 252          /* std140 always rounds the stride of arrays (and matrices)
 253           * to a vec4, so matrices are always 16 between columns/rows.
 254           */
 255          emit_ubo_loads(col_deref, base_offset, deref_offset + i * 16);
 256       }
 257       return;
 258    }
 259
 260    assert(deref->type->is_scalar() ||
 261           deref->type->is_vector());
 262
 263    if (!ubo_var->RowMajor) {
 264       ir_rvalue *offset = add(base_offset,
 265                               new(mem_ctx) ir_constant(deref_offset));
 266       base_ir->insert_before(assign(deref->clone(mem_ctx, NULL),
 267                                     ubo_load(deref->type, offset)));
 268    } else {
 269       /* We're dereffing a column out of a row-major matrix, so we
 270        * gather the vector from each stored row.
 271       */
 272       assert(deref->type->base_type == GLSL_TYPE_FLOAT);
 273       /* Matrices, row_major or not, are stored as if they were
 274        * arrays of vectors of the appropriate size in std140.
 275        * Arrays have their strides rounded up to a vec4, so the
 276        * matrix stride is always 16.
 277        */
 278       unsigned matrix_stride = 16;
 279
 280       for (unsigned i = 0; i < deref->type->vector_elements; i++) {
 281          ir_rvalue *chan = new(mem_ctx) ir_constant((int)i);
 282          ir_dereference *deref_chan =
 283             new(mem_ctx) ir_dereference_array(deref->clone(mem_ctx, NULL),
 284                                               chan);
 285
 286          ir_rvalue *chan_offset =
 287             add(base_offset,
 288                 new(mem_ctx) ir_constant(deref_offset + i * matrix_stride));
 289
 290          base_ir->insert_before(assign(deref_chan,
 291                                        ubo_load(glsl_type::float_type,
 292                                                 chan_offset)));
 293       }
 294    }
 295 }
 296
 297 } /* unnamed namespace */
 298
 299 void
 300 lower_ubo_reference(struct gl_shader *shader, exec_list *instructions)
 301 {
 302    lower_ubo_reference_visitor v(shader);
 303
 304    /* Loop over the instructions lowering references, because we take
 305     * a deref of a UBO array using a UBO dereference as the index will
 306     * produce a collection of instructions all of which have cloned
 307     * UBO dereferences for that array index.
 308     */
 309    do {
 310       v.progress = false;
 311       visit_list_elements(&v, instructions);
 312    } while (v.progress);
 313 }