src/compiler/glsl/ir_array_refcount.cpp

   1 /*
   2  * Copyright © 2016 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 ir_array_refcount.cpp
  26  *
  27  * Provides a visitor which produces a list of variables referenced.
  28  */
  29
  30 #include "ir.h"
  31 #include "ir_visitor.h"
  32 #include "ir_array_refcount.h"
  33 #include "compiler/glsl_types.h"
  34 #include "util/hash_table.h"
  35
  36 ir_array_refcount_visitor::ir_array_refcount_visitor()
  37    : last_array_deref(0), derefs(0), num_derefs(0), derefs_size(0)
  38 {
  39    this->mem_ctx = ralloc_context(NULL);
  40    this->ht = _mesa_pointer_hash_table_create(NULL);
  41 }
  42
  43 static void
  44 free_entry(struct hash_entry *entry)
  45 {
  46    ir_array_refcount_entry *ivre = (ir_array_refcount_entry *) entry->data;
  47    delete ivre;
  48 }
  49
  50 ir_array_refcount_visitor::~ir_array_refcount_visitor()
  51 {
  52    ralloc_free(this->mem_ctx);
  53    _mesa_hash_table_destroy(this->ht, free_entry);
  54 }
  55
  56 ir_array_refcount_entry::ir_array_refcount_entry(ir_variable *var)
  57    : var(var), is_referenced(false)
  58 {
  59    num_bits = MAX2(1, var->type->arrays_of_arrays_size());
  60    bits = new BITSET_WORD[BITSET_WORDS(num_bits)];
  61    memset(bits, 0, BITSET_WORDS(num_bits) * sizeof(bits[0]));
  62
  63    /* Count the "depth" of the arrays-of-arrays. */
  64    array_depth = 0;
  65    for (const glsl_type *type = var->type;
  66         type->is_array();
  67         type = type->fields.array) {
  68       array_depth++;
  69    }
  70 }
  71
  72
  73 ir_array_refcount_entry::~ir_array_refcount_entry()
  74 {
  75    delete [] bits;
  76 }
  77
  78
  79 void
  80 ir_array_refcount_entry::mark_array_elements_referenced(const array_deref_range *dr,
  81                                                         unsigned count)
  82 {
  83    if (count != array_depth)
  84       return;
  85
  86    mark_array_elements_referenced(dr, count, 1, 0);
  87 }
  88
  89 void
  90 ir_array_refcount_entry::mark_array_elements_referenced(const array_deref_range *dr,
  91                                                         unsigned count,
  92                                                         unsigned scale,
  93                                                         unsigned linearized_index)
  94 {
  95    /* Walk through the list of array dereferences in least- to
  96     * most-significant order.  Along the way, accumulate the current
  97     * linearized offset and the scale factor for each array-of-.
  98     */
  99    for (unsigned i = 0; i < count; i++) {
 100       if (dr[i].index < dr[i].size) {
 101          linearized_index += dr[i].index * scale;
 102          scale *= dr[i].size;
 103       } else {
 104          /* For each element in the current array, update the count and
 105           * offset, then recurse to process the remaining arrays.
 106           *
 107           * There is some inefficency here if the last element in the
 108           * array_deref_range list specifies the entire array.  In that case,
 109           * the loop will make recursive calls with count == 0.  In the call,
 110           * all that will happen is the bit will be set.
 111           */
 112          for (unsigned j = 0; j < dr[i].size; j++) {
 113             mark_array_elements_referenced(&dr[i + 1],
 114                                            count - (i + 1),
 115                                            scale * dr[i].size,
 116                                            linearized_index + (j * scale));
 117          }
 118
 119          return;
 120       }
 121    }
 122
 123    BITSET_SET(bits, linearized_index);
 124 }
 125
 126 ir_array_refcount_entry *
 127 ir_array_refcount_visitor::get_variable_entry(ir_variable *var)
 128 {
 129    assert(var);
 130
 131    struct hash_entry *e = _mesa_hash_table_search(this->ht, var);
 132    if (e)
 133       return (ir_array_refcount_entry *)e->data;
 134
 135    ir_array_refcount_entry *entry = new ir_array_refcount_entry(var);
 136    _mesa_hash_table_insert(this->ht, var, entry);
 137
 138    return entry;
 139 }
 140
 141
 142 array_deref_range *
 143 ir_array_refcount_visitor::get_array_deref()
 144 {
 145    if ((num_derefs + 1) * sizeof(array_deref_range) > derefs_size) {
 146       void *ptr = reralloc_size(mem_ctx, derefs, derefs_size + 4096);
 147
 148       if (ptr == NULL)
 149          return NULL;
 150
 151       derefs_size += 4096;
 152       derefs = (array_deref_range *)ptr;
 153    }
 154
 155    array_deref_range *d = &derefs[num_derefs];
 156    num_derefs++;
 157
 158    return d;
 159 }
 160
 161 ir_visitor_status
 162 ir_array_refcount_visitor::visit_enter(ir_dereference_array *ir)
 163 {
 164    /* It could also be a vector or a matrix.  Individual elements of vectors
 165     * are natrices are not tracked, so bail.
 166     */
 167    if (!ir->array->type->is_array())
 168       return visit_continue;
 169
 170    /* If this array dereference is a child of an array dereference that was
 171     * already visited, just continue on.  Otherwise, for an arrays-of-arrays
 172     * dereference like x[1][2][3][4], we'd process the [1][2][3][4] sequence,
 173     * the [1][2][3] sequence, the [1][2] sequence, and the [1] sequence.  This
 174     * ensures that we only process the full sequence.
 175     */
 176    if (last_array_deref && last_array_deref->array == ir) {
 177       last_array_deref = ir;
 178       return visit_continue;
 179    }
 180
 181    last_array_deref = ir;
 182
 183    num_derefs = 0;
 184
 185    ir_rvalue *rv = ir;
 186    while (rv->ir_type == ir_type_dereference_array) {
 187       ir_dereference_array *const deref = rv->as_dereference_array();
 188
 189       assert(deref != NULL);
 190       assert(deref->array->type->is_array());
 191
 192       ir_rvalue *const array = deref->array;
 193       const ir_constant *const idx = deref->array_index->as_constant();
 194       array_deref_range *const dr = get_array_deref();
 195
 196       dr->size = array->type->array_size();
 197
 198       if (idx != NULL) {
 199          dr->index = idx->get_int_component(0);
 200       } else {
 201          /* An unsized array can occur at the end of an SSBO.  We can't track
 202           * accesses to such an array, so bail.
 203           */
 204          if (array->type->array_size() == 0)
 205             return visit_continue;
 206
 207          dr->index = dr->size;
 208       }
 209
 210       rv = array;
 211    }
 212
 213    ir_dereference_variable *const var_deref = rv->as_dereference_variable();
 214
 215    /* If the array being dereferenced is not a variable, bail.  At the very
 216     * least, ir_constant and ir_dereference_record are possible.
 217     */
 218    if (var_deref == NULL)
 219       return visit_continue;
 220
 221    ir_array_refcount_entry *const entry =
 222       this->get_variable_entry(var_deref->var);
 223
 224    if (entry == NULL)
 225       return visit_stop;
 226
 227    entry->mark_array_elements_referenced(derefs, num_derefs);
 228
 229    return visit_continue;
 230 }
 231
 232
 233 ir_visitor_status
 234 ir_array_refcount_visitor::visit(ir_dereference_variable *ir)
 235 {
 236    ir_variable *const var = ir->variable_referenced();
 237    ir_array_refcount_entry *entry = this->get_variable_entry(var);
 238
 239    entry->is_referenced = true;
 240
 241    return visit_continue;
 242 }
 243
 244
 245 ir_visitor_status
 246 ir_array_refcount_visitor::visit_enter(ir_function_signature *ir)
 247 {
 248    /* We don't want to descend into the function parameters and
 249     * dead-code eliminate them, so just accept the body here.
 250     */
 251    visit_list_elements(this, &ir->body);
 252    return visit_continue_with_parent;
 253 }