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_builder.h"
  30
  31 struct locals_to_regs_state {
  32    nir_builder builder;
  33
  34    /* A hash table mapping derefs to registers */
  35    struct hash_table *regs_table;
  36
  37    bool progress;
  38 };
  39
  40 /* The following two functions implement a hash and equality check for
  41  * variable dreferences.  When the hash or equality function encounters an
  42  * array, it ignores the offset and whether it is direct or indirect
  43  * entirely.
  44  */
  45 static uint32_t
  46 hash_deref(const void *void_deref)
  47 {
  48    uint32_t hash = _mesa_fnv32_1a_offset_bias;
  49
  50    for (const nir_deref_instr *deref = void_deref; deref;
  51         deref = nir_deref_instr_parent(deref)) {
  52       switch (deref->deref_type) {
  53       case nir_deref_type_var:
  54          return _mesa_fnv32_1a_accumulate(hash, deref->var);
  55
  56       case nir_deref_type_array:
  57          continue; /* Do nothing */
  58
  59       case nir_deref_type_struct:
  60          hash = _mesa_fnv32_1a_accumulate(hash, deref->strct.index);
  61          continue;
  62
  63       default:
  64          unreachable("Invalid deref type");
  65       }
  66    }
  67
  68    unreachable("We should have hit a variable dereference");
  69 }
  70
  71 static bool
  72 derefs_equal(const void *void_a, const void *void_b)
  73 {
  74    for (const nir_deref_instr *a = void_a, *b = void_b; a || b;
  75         a = nir_deref_instr_parent(a), b = nir_deref_instr_parent(b)) {
  76       if (a->deref_type != b->deref_type)
  77          return false;
  78
  79       switch (a->deref_type) {
  80       case nir_deref_type_var:
  81          return a->var == b->var;
  82
  83       case nir_deref_type_array:
  84          continue; /* Do nothing */
  85
  86       case nir_deref_type_struct:
  87          if (a->strct.index != b->strct.index)
  88             return false;
  89          continue;
  90
  91       default:
  92          unreachable("Invalid deref type");
  93       }
  94    }
  95
  96    unreachable("We should have hit a variable dereference");
  97 }
  98
  99 static nir_register *
 100 get_reg_for_deref(nir_deref_instr *deref, struct locals_to_regs_state *state)
 101 {
 102    uint32_t hash = hash_deref(deref);
 103
 104    assert(nir_deref_instr_get_variable(deref)->constant_initializer == NULL &&
 105           nir_deref_instr_get_variable(deref)->pointer_initializer == NULL);
 106
 107    struct hash_entry *entry =
 108       _mesa_hash_table_search_pre_hashed(state->regs_table, hash, deref);
 109    if (entry)
 110       return entry->data;
 111
 112    unsigned array_size = 1;
 113    for (nir_deref_instr *d = deref; d; d = nir_deref_instr_parent(d)) {
 114       if (d->deref_type == nir_deref_type_array)
 115          array_size *= glsl_get_length(nir_deref_instr_parent(d)->type);
 116    }
 117
 118    assert(glsl_type_is_vector_or_scalar(deref->type));
 119
 120    nir_register *reg = nir_local_reg_create(state->builder.impl);
 121    reg->num_components = glsl_get_vector_elements(deref->type);
 122    reg->num_array_elems = array_size > 1 ? array_size : 0;
 123    reg->bit_size = glsl_get_bit_size(deref->type);
 124
 125    _mesa_hash_table_insert_pre_hashed(state->regs_table, hash, deref, reg);
 126
 127    return reg;
 128 }
 129
 130 static nir_src
 131 get_deref_reg_src(nir_deref_instr *deref, struct locals_to_regs_state *state)
 132 {
 133    nir_builder *b = &state->builder;
 134
 135    nir_src src;
 136
 137    src.is_ssa = false;
 138    src.reg.reg = get_reg_for_deref(deref, state);
 139    src.reg.base_offset = 0;
 140    src.reg.indirect = NULL;
 141
 142    /* It is possible for a user to create a shader that has an array with a
 143     * single element and then proceed to access it indirectly.  Indirectly
 144     * accessing a non-array register is not allowed in NIR.  In order to
 145     * handle this case we just convert it to a direct reference.
 146     */
 147    if (src.reg.reg->num_array_elems == 0)
 148       return src;
 149
 150    unsigned inner_array_size = 1;
 151    for (const nir_deref_instr *d = deref; d; d = nir_deref_instr_parent(d)) {
 152       if (d->deref_type != nir_deref_type_array)
 153          continue;
 154
 155       if (nir_src_is_const(d->arr.index) && !src.reg.indirect) {
 156          src.reg.base_offset += nir_src_as_uint(d->arr.index) *
 157                                 inner_array_size;
 158       } else {
 159          if (src.reg.indirect) {
 160             assert(src.reg.base_offset == 0);
 161          } else {
 162             src.reg.indirect = ralloc(b->shader, nir_src);
 163             *src.reg.indirect =
 164                nir_src_for_ssa(nir_imm_int(b, src.reg.base_offset));
 165             src.reg.base_offset = 0;
 166          }
 167
 168          assert(src.reg.indirect->is_ssa);
 169          nir_ssa_def *index = nir_i2i(b, nir_ssa_for_src(b, d->arr.index, 1), 32);
 170          src.reg.indirect->ssa =
 171             nir_iadd(b, src.reg.indirect->ssa,
 172                         nir_imul(b, index, nir_imm_int(b, inner_array_size)));
 173       }
 174
 175       inner_array_size *= glsl_get_length(nir_deref_instr_parent(d)->type);
 176    }
 177
 178    return src;
 179 }
 180
 181 static bool
 182 lower_locals_to_regs_block(nir_block *block,
 183                            struct locals_to_regs_state *state)
 184 {
 185    nir_builder *b = &state->builder;
 186
 187    nir_foreach_instr_safe(instr, block) {
 188       if (instr->type != nir_instr_type_intrinsic)
 189          continue;
 190
 191       nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
 192
 193       switch (intrin->intrinsic) {
 194       case nir_intrinsic_load_deref: {
 195          nir_deref_instr *deref = nir_src_as_deref(intrin->src[0]);
 196          if (deref->mode != nir_var_function_temp)
 197             continue;
 198
 199          b->cursor = nir_before_instr(&intrin->instr);
 200
 201          nir_alu_instr *mov = nir_alu_instr_create(b->shader, nir_op_mov);
 202          mov->src[0].src = get_deref_reg_src(deref, state);
 203          mov->dest.write_mask = (1 << intrin->num_components) - 1;
 204          if (intrin->dest.is_ssa) {
 205             nir_ssa_dest_init(&mov->instr, &mov->dest.dest,
 206                               intrin->num_components,
 207                               intrin->dest.ssa.bit_size, NULL);
 208             nir_ssa_def_rewrite_uses(&intrin->dest.ssa,
 209                                      nir_src_for_ssa(&mov->dest.dest.ssa));
 210          } else {
 211             nir_dest_copy(&mov->dest.dest, &intrin->dest, &mov->instr);
 212          }
 213          nir_builder_instr_insert(b, &mov->instr);
 214
 215          nir_instr_remove(&intrin->instr);
 216          state->progress = true;
 217          break;
 218       }
 219
 220       case nir_intrinsic_store_deref: {
 221          nir_deref_instr *deref = nir_src_as_deref(intrin->src[0]);
 222          if (deref->mode != nir_var_function_temp)
 223             continue;
 224
 225          b->cursor = nir_before_instr(&intrin->instr);
 226
 227          nir_src reg_src = get_deref_reg_src(deref, state);
 228
 229          nir_alu_instr *mov = nir_alu_instr_create(b->shader, nir_op_mov);
 230          nir_src_copy(&mov->src[0].src, &intrin->src[1], mov);
 231          mov->dest.write_mask = nir_intrinsic_write_mask(intrin);
 232          mov->dest.dest.is_ssa = false;
 233          mov->dest.dest.reg.reg = reg_src.reg.reg;
 234          mov->dest.dest.reg.base_offset = reg_src.reg.base_offset;
 235          mov->dest.dest.reg.indirect = reg_src.reg.indirect;
 236
 237          nir_builder_instr_insert(b, &mov->instr);
 238
 239          nir_instr_remove(&intrin->instr);
 240          state->progress = true;
 241          break;
 242       }
 243
 244       case nir_intrinsic_copy_deref:
 245          unreachable("There should be no copies whatsoever at this point");
 246          break;
 247
 248       default:
 249          continue;
 250       }
 251    }
 252
 253    return true;
 254 }
 255
 256 static bool
 257 nir_lower_locals_to_regs_impl(nir_function_impl *impl)
 258 {
 259    struct locals_to_regs_state state;
 260
 261    nir_builder_init(&state.builder, impl);
 262    state.progress = false;
 263    state.regs_table = _mesa_hash_table_create(NULL, hash_deref, derefs_equal);
 264
 265    nir_metadata_require(impl, nir_metadata_dominance);
 266
 267    nir_foreach_block(block, impl) {
 268       lower_locals_to_regs_block(block, &state);
 269    }
 270
 271    nir_metadata_preserve(impl, nir_metadata_block_index |
 272                                nir_metadata_dominance);
 273
 274    _mesa_hash_table_destroy(state.regs_table, NULL);
 275
 276    return state.progress;
 277 }
 278
 279 bool
 280 nir_lower_locals_to_regs(nir_shader *shader)
 281 {
 282    bool progress = false;
 283
 284    nir_foreach_function(function, shader) {
 285       if (function->impl)
 286          progress = nir_lower_locals_to_regs_impl(function->impl) || progress;
 287    }
 288
 289    return progress;
 290 }