src/compiler/nir/nir_lower_locals_to_regs.c

   1 /*
   2  * Copyright © 2014 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 DEALINGS
  21  * IN THE SOFTWARE.
  22  *
  23  * Authors:
  24  *    Jason Ekstrand (jason@jlekstrand.net)
  25  *
  26  */
  27
  28 #include "nir.h"
  29 #include "nir_array.h"
  30
  31 struct locals_to_regs_state {
  32    nir_shader *shader;
  33    nir_function_impl *impl;
  34
  35    /* A hash table mapping derefs to registers */
  36    struct hash_table *regs_table;
  37
  38    bool progress;
  39 };
  40
  41 /* The following two functions implement a hash and equality check for
  42  * variable dreferences.  When the hash or equality function encounters an
  43  * array, it ignores the offset and whether it is direct or indirect
  44  * entirely.
  45  */
  46 static uint32_t
  47 hash_deref(const void *void_deref)
  48 {
  49    uint32_t hash = _mesa_fnv32_1a_offset_bias;
  50
  51    const nir_deref_var *deref_var = void_deref;
  52    hash = _mesa_fnv32_1a_accumulate(hash, deref_var->var);
  53
  54    for (const nir_deref *deref = deref_var->deref.child;
  55         deref; deref = deref->child) {
  56       if (deref->deref_type == nir_deref_type_struct) {
  57          const nir_deref_struct *deref_struct = nir_deref_as_struct(deref);
  58          hash = _mesa_fnv32_1a_accumulate(hash, deref_struct->index);
  59       }
  60    }
  61
  62    return hash;
  63 }
  64
  65 static bool
  66 derefs_equal(const void *void_a, const void *void_b)
  67 {
  68    const nir_deref_var *a_var = void_a;
  69    const nir_deref_var *b_var = void_b;
  70
  71    if (a_var->var != b_var->var)
  72       return false;
  73
  74    for (const nir_deref *a = a_var->deref.child, *b = b_var->deref.child;
  75         a != NULL; a = a->child, b = b->child) {
  76       if (a->deref_type != b->deref_type)
  77          return false;
  78
  79       if (a->deref_type == nir_deref_type_struct) {
  80          if (nir_deref_as_struct(a)->index != nir_deref_as_struct(b)->index)
  81             return false;
  82       }
  83       /* Do nothing for arrays.  They're all the same. */
  84
  85       assert((a->child == NULL) == (b->child == NULL));
  86       if((a->child == NULL) != (b->child == NULL))
  87          return false;
  88    }
  89
  90    return true;
  91 }
  92
  93 static nir_register *
  94 get_reg_for_deref(nir_deref_var *deref, struct locals_to_regs_state *state)
  95 {
  96    uint32_t hash = hash_deref(deref);
  97
  98    assert(deref->var->constant_initializer == NULL);
  99
 100    struct hash_entry *entry =
 101       _mesa_hash_table_search_pre_hashed(state->regs_table, hash, deref);
 102    if (entry)
 103       return entry->data;
 104
 105    unsigned array_size = 1;
 106    nir_deref *tail = &deref->deref;
 107    while (tail->child) {
 108       if (tail->child->deref_type == nir_deref_type_array)
 109          array_size *= glsl_get_length(tail->type);
 110       tail = tail->child;
 111    }
 112
 113    assert(glsl_type_is_vector(tail->type) || glsl_type_is_scalar(tail->type));
 114
 115    nir_register *reg = nir_local_reg_create(state->impl);
 116    reg->num_components = glsl_get_vector_elements(tail->type);
 117    reg->num_array_elems = array_size > 1 ? array_size : 0;
 118    reg->bit_size = glsl_get_bit_size(tail->type);
 119
 120    _mesa_hash_table_insert_pre_hashed(state->regs_table, hash, deref, reg);
 121
 122    return reg;
 123 }
 124
 125 static nir_src
 126 get_deref_reg_src(nir_deref_var *deref, nir_instr *instr,
 127                   struct locals_to_regs_state *state)
 128 {
 129    nir_src src;
 130
 131    src.is_ssa = false;
 132    src.reg.reg = get_reg_for_deref(deref, state);
 133    src.reg.base_offset = 0;
 134    src.reg.indirect = NULL;
 135
 136    /* It is possible for a user to create a shader that has an array with a
 137     * single element and then proceed to access it indirectly.  Indirectly
 138     * accessing a non-array register is not allowed in NIR.  In order to
 139     * handle this case we just convert it to a direct reference.
 140     */
 141    if (src.reg.reg->num_array_elems == 0)
 142       return src;
 143
 144    nir_deref *tail = &deref->deref;
 145    while (tail->child != NULL) {
 146       const struct glsl_type *parent_type = tail->type;
 147       tail = tail->child;
 148
 149       if (tail->deref_type != nir_deref_type_array)
 150          continue;
 151
 152       nir_deref_array *deref_array = nir_deref_as_array(tail);
 153
 154       src.reg.base_offset *= glsl_get_length(parent_type);
 155       src.reg.base_offset += deref_array->base_offset;
 156
 157       if (src.reg.indirect) {
 158          nir_load_const_instr *load_const =
 159             nir_load_const_instr_create(state->shader, 1, 32);
 160          load_const->value.u32[0] = glsl_get_length(parent_type);
 161          nir_instr_insert_before(instr, &load_const->instr);
 162
 163          nir_alu_instr *mul = nir_alu_instr_create(state->shader, nir_op_imul);
 164          mul->src[0].src = *src.reg.indirect;
 165          mul->src[1].src.is_ssa = true;
 166          mul->src[1].src.ssa = &load_const->def;
 167          mul->dest.write_mask = 1;
 168          nir_ssa_dest_init(&mul->instr, &mul->dest.dest, 1, 32, NULL);
 169          nir_instr_insert_before(instr, &mul->instr);
 170
 171          src.reg.indirect->is_ssa = true;
 172          src.reg.indirect->ssa = &mul->dest.dest.ssa;
 173       }
 174
 175       if (deref_array->deref_array_type == nir_deref_array_type_indirect) {
 176          if (src.reg.indirect == NULL) {
 177             src.reg.indirect = ralloc(state->shader, nir_src);
 178             nir_src_copy(src.reg.indirect, &deref_array->indirect,
 179                          state->shader);
 180          } else {
 181             nir_alu_instr *add = nir_alu_instr_create(state->shader,
 182                                                       nir_op_iadd);
 183             add->src[0].src = *src.reg.indirect;
 184             nir_src_copy(&add->src[1].src, &deref_array->indirect, add);
 185             add->dest.write_mask = 1;
 186             nir_ssa_dest_init(&add->instr, &add->dest.dest, 1, 32, NULL);
 187             nir_instr_insert_before(instr, &add->instr);
 188
 189             src.reg.indirect->is_ssa = true;
 190             src.reg.indirect->ssa = &add->dest.dest.ssa;
 191          }
 192       }
 193    }
 194
 195    return src;
 196 }
 197
 198 static bool
 199 lower_locals_to_regs_block(nir_block *block,
 200                            struct locals_to_regs_state *state)
 201 {
 202    nir_foreach_instr_safe(instr, block) {
 203       if (instr->type != nir_instr_type_intrinsic)
 204          continue;
 205
 206       nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
 207
 208       switch (intrin->intrinsic) {
 209       case nir_intrinsic_load_var: {
 210          if (intrin->variables[0]->var->data.mode != nir_var_local)
 211             continue;
 212
 213          nir_alu_instr *mov = nir_alu_instr_create(state->shader, nir_op_imov);
 214          mov->src[0].src = get_deref_reg_src(intrin->variables[0],
 215                                              &intrin->instr, state);
 216          mov->dest.write_mask = (1 << intrin->num_components) - 1;
 217          if (intrin->dest.is_ssa) {
 218             nir_ssa_dest_init(&mov->instr, &mov->dest.dest,
 219                               intrin->num_components,
 220                               intrin->dest.ssa.bit_size, NULL);
 221             nir_ssa_def_rewrite_uses(&intrin->dest.ssa,
 222                                      nir_src_for_ssa(&mov->dest.dest.ssa));
 223          } else {
 224             nir_dest_copy(&mov->dest.dest, &intrin->dest, &mov->instr);
 225          }
 226          nir_instr_insert_before(&intrin->instr, &mov->instr);
 227
 228          nir_instr_remove(&intrin->instr);
 229          state->progress = true;
 230          break;
 231       }
 232
 233       case nir_intrinsic_store_var: {
 234          if (intrin->variables[0]->var->data.mode != nir_var_local)
 235             continue;
 236
 237          nir_src reg_src = get_deref_reg_src(intrin->variables[0],
 238                                              &intrin->instr, state);
 239
 240          nir_alu_instr *mov = nir_alu_instr_create(state->shader, nir_op_imov);
 241          nir_src_copy(&mov->src[0].src, &intrin->src[0], mov);
 242          mov->dest.write_mask = nir_intrinsic_write_mask(intrin);
 243          mov->dest.dest.is_ssa = false;
 244          mov->dest.dest.reg.reg = reg_src.reg.reg;
 245          mov->dest.dest.reg.base_offset = reg_src.reg.base_offset;
 246          mov->dest.dest.reg.indirect = reg_src.reg.indirect;
 247
 248          nir_instr_insert_before(&intrin->instr, &mov->instr);
 249
 250          nir_instr_remove(&intrin->instr);
 251          state->progress = true;
 252          break;
 253       }
 254
 255       case nir_intrinsic_copy_var:
 256          unreachable("There should be no copies whatsoever at this point");
 257          break;
 258
 259       default:
 260          continue;
 261       }
 262    }
 263
 264    return true;
 265 }
 266
 267 static bool
 268 nir_lower_locals_to_regs_impl(nir_function_impl *impl)
 269 {
 270    struct locals_to_regs_state state;
 271
 272    state.shader = impl->function->shader;
 273    state.impl = impl;
 274    state.progress = false;
 275    state.regs_table = _mesa_hash_table_create(NULL, hash_deref, derefs_equal);
 276
 277    nir_metadata_require(impl, nir_metadata_dominance);
 278
 279    nir_foreach_block(block, impl) {
 280       lower_locals_to_regs_block(block, &state);
 281    }
 282
 283    nir_metadata_preserve(impl, nir_metadata_block_index |
 284                                nir_metadata_dominance);
 285
 286    _mesa_hash_table_destroy(state.regs_table, NULL);
 287
 288    return state.progress;
 289 }
 290
 291 bool
 292 nir_lower_locals_to_regs(nir_shader *shader)
 293 {
 294    bool progress = false;
 295
 296    nir_foreach_function(function, shader) {
 297       if (function->impl)
 298          progress = nir_lower_locals_to_regs_impl(function->impl) || progress;
 299    }
 300
 301    return progress;
 302 }