src/compiler/nir/nir_search.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 <inttypes.h>
  29 #include "nir_search.h"
  30 #include "util/half_float.h"
  31
  32 struct match_state {
  33    bool inexact_match;
  34    bool has_exact_alu;
  35    unsigned variables_seen;
  36    nir_alu_src variables[NIR_SEARCH_MAX_VARIABLES];
  37 };
  38
  39 static bool
  40 match_expression(const nir_search_expression *expr, nir_alu_instr *instr,
  41                  unsigned num_components, const uint8_t *swizzle,
  42                  struct match_state *state);
  43
  44 static const uint8_t identity_swizzle[NIR_MAX_VEC_COMPONENTS] = { 0, 1, 2, 3 };
  45
  46 /**
  47  * Check if a source produces a value of the given type.
  48  *
  49  * Used for satisfying 'a@type' constraints.
  50  */
  51 static bool
  52 src_is_type(nir_src src, nir_alu_type type)
  53 {
  54    assert(type != nir_type_invalid);
  55
  56    if (!src.is_ssa)
  57       return false;
  58
  59    /* Turn nir_type_bool32 into nir_type_bool...they're the same thing. */
  60    if (nir_alu_type_get_base_type(type) == nir_type_bool)
  61       type = nir_type_bool;
  62
  63    if (src.ssa->parent_instr->type == nir_instr_type_alu) {
  64       nir_alu_instr *src_alu = nir_instr_as_alu(src.ssa->parent_instr);
  65       nir_alu_type output_type = nir_op_infos[src_alu->op].output_type;
  66
  67       if (type == nir_type_bool) {
  68          switch (src_alu->op) {
  69          case nir_op_iand:
  70          case nir_op_ior:
  71          case nir_op_ixor:
  72             return src_is_type(src_alu->src[0].src, nir_type_bool) &&
  73                    src_is_type(src_alu->src[1].src, nir_type_bool);
  74          case nir_op_inot:
  75             return src_is_type(src_alu->src[0].src, nir_type_bool);
  76          default:
  77             break;
  78          }
  79       }
  80
  81       return nir_alu_type_get_base_type(output_type) == type;
  82    } else if (src.ssa->parent_instr->type == nir_instr_type_intrinsic) {
  83       nir_intrinsic_instr *intr = nir_instr_as_intrinsic(src.ssa->parent_instr);
  84
  85       if (type == nir_type_bool) {
  86          return intr->intrinsic == nir_intrinsic_load_front_face ||
  87                 intr->intrinsic == nir_intrinsic_load_helper_invocation;
  88       }
  89    }
  90
  91    /* don't know */
  92    return false;
  93 }
  94
  95 static bool
  96 match_value(const nir_search_value *value, nir_alu_instr *instr, unsigned src,
  97             unsigned num_components, const uint8_t *swizzle,
  98             struct match_state *state)
  99 {
 100    uint8_t new_swizzle[NIR_MAX_VEC_COMPONENTS];
 101
 102    /* Searching only works on SSA values because, if it's not SSA, we can't
 103     * know if the value changed between one instance of that value in the
 104     * expression and another.  Also, the replace operation will place reads of
 105     * that value right before the last instruction in the expression we're
 106     * replacing so those reads will happen after the original reads and may
 107     * not be valid if they're register reads.
 108     */
 109    if (!instr->src[src].src.is_ssa)
 110       return false;
 111
 112    /* If the source is an explicitly sized source, then we need to reset
 113     * both the number of components and the swizzle.
 114     */
 115    if (nir_op_infos[instr->op].input_sizes[src] != 0) {
 116       num_components = nir_op_infos[instr->op].input_sizes[src];
 117       swizzle = identity_swizzle;
 118    }
 119
 120    for (unsigned i = 0; i < num_components; ++i)
 121       new_swizzle[i] = instr->src[src].swizzle[swizzle[i]];
 122
 123    /* If the value has a specific bit size and it doesn't match, bail */
 124    if (value->bit_size &&
 125        nir_src_bit_size(instr->src[src].src) != value->bit_size)
 126       return false;
 127
 128    switch (value->type) {
 129    case nir_search_value_expression:
 130       if (instr->src[src].src.ssa->parent_instr->type != nir_instr_type_alu)
 131          return false;
 132
 133       return match_expression(nir_search_value_as_expression(value),
 134                               nir_instr_as_alu(instr->src[src].src.ssa->parent_instr),
 135                               num_components, new_swizzle, state);
 136
 137    case nir_search_value_variable: {
 138       nir_search_variable *var = nir_search_value_as_variable(value);
 139       assert(var->variable < NIR_SEARCH_MAX_VARIABLES);
 140
 141       if (state->variables_seen & (1 << var->variable)) {
 142          if (state->variables[var->variable].src.ssa != instr->src[src].src.ssa)
 143             return false;
 144
 145          assert(!instr->src[src].abs && !instr->src[src].negate);
 146
 147          for (unsigned i = 0; i < num_components; ++i) {
 148             if (state->variables[var->variable].swizzle[i] != new_swizzle[i])
 149                return false;
 150          }
 151
 152          return true;
 153       } else {
 154          if (var->is_constant &&
 155              instr->src[src].src.ssa->parent_instr->type != nir_instr_type_load_const)
 156             return false;
 157
 158          if (var->cond && !var->cond(instr, src, num_components, new_swizzle))
 159             return false;
 160
 161          if (var->type != nir_type_invalid &&
 162              !src_is_type(instr->src[src].src, var->type))
 163             return false;
 164
 165          state->variables_seen |= (1 << var->variable);
 166          state->variables[var->variable].src = instr->src[src].src;
 167          state->variables[var->variable].abs = false;
 168          state->variables[var->variable].negate = false;
 169
 170          for (unsigned i = 0; i < NIR_MAX_VEC_COMPONENTS; ++i) {
 171             if (i < num_components)
 172                state->variables[var->variable].swizzle[i] = new_swizzle[i];
 173             else
 174                state->variables[var->variable].swizzle[i] = 0;
 175          }
 176
 177          return true;
 178       }
 179    }
 180
 181    case nir_search_value_constant: {
 182       nir_search_constant *const_val = nir_search_value_as_constant(value);
 183
 184       if (!nir_src_is_const(instr->src[src].src))
 185          return false;
 186
 187       switch (const_val->type) {
 188       case nir_type_float:
 189          for (unsigned i = 0; i < num_components; ++i) {
 190             double val = nir_src_comp_as_float(instr->src[src].src,
 191                                                new_swizzle[i]);
 192             if (val != const_val->data.d)
 193                return false;
 194          }
 195          return true;
 196
 197       case nir_type_int:
 198       case nir_type_uint:
 199       case nir_type_bool32: {
 200          unsigned bit_size = nir_src_bit_size(instr->src[src].src);
 201          uint64_t mask = bit_size == 64 ? UINT64_MAX : (1ull << bit_size) - 1;
 202          for (unsigned i = 0; i < num_components; ++i) {
 203             uint64_t val = nir_src_comp_as_uint(instr->src[src].src,
 204                                                 new_swizzle[i]);
 205             if ((val & mask) != (const_val->data.u & mask))
 206                return false;
 207          }
 208          return true;
 209       }
 210
 211       default:
 212          unreachable("Invalid alu source type");
 213       }
 214    }
 215
 216    default:
 217       unreachable("Invalid search value type");
 218    }
 219 }
 220
 221 static bool
 222 match_expression(const nir_search_expression *expr, nir_alu_instr *instr,
 223                  unsigned num_components, const uint8_t *swizzle,
 224                  struct match_state *state)
 225 {
 226    if (expr->cond && !expr->cond(instr))
 227       return false;
 228
 229    if (instr->op != expr->opcode)
 230       return false;
 231
 232    assert(instr->dest.dest.is_ssa);
 233
 234    if (expr->value.bit_size &&
 235        instr->dest.dest.ssa.bit_size != expr->value.bit_size)
 236       return false;
 237
 238    state->inexact_match = expr->inexact || state->inexact_match;
 239    state->has_exact_alu = instr->exact || state->has_exact_alu;
 240    if (state->inexact_match && state->has_exact_alu)
 241       return false;
 242
 243    assert(!instr->dest.saturate);
 244    assert(nir_op_infos[instr->op].num_inputs > 0);
 245
 246    /* If we have an explicitly sized destination, we can only handle the
 247     * identity swizzle.  While dot(vec3(a, b, c).zxy) is a valid
 248     * expression, we don't have the information right now to propagate that
 249     * swizzle through.  We can only properly propagate swizzles if the
 250     * instruction is vectorized.
 251     */
 252    if (nir_op_infos[instr->op].output_size != 0) {
 253       for (unsigned i = 0; i < num_components; i++) {
 254          if (swizzle[i] != i)
 255             return false;
 256       }
 257    }
 258
 259    /* Stash off the current variables_seen bitmask.  This way we can
 260     * restore it prior to matching in the commutative case below.
 261     */
 262    unsigned variables_seen_stash = state->variables_seen;
 263
 264    bool matched = true;
 265    for (unsigned i = 0; i < nir_op_infos[instr->op].num_inputs; i++) {
 266       if (!match_value(expr->srcs[i], instr, i, num_components,
 267                        swizzle, state)) {
 268          matched = false;
 269          break;
 270       }
 271    }
 272
 273    if (matched)
 274       return true;
 275
 276    if (nir_op_infos[instr->op].algebraic_properties & NIR_OP_IS_COMMUTATIVE) {
 277       assert(nir_op_infos[instr->op].num_inputs == 2);
 278
 279       /* Restore the variables_seen bitmask.  If we don't do this, then we
 280        * could end up with an erroneous failure due to variables found in the
 281        * first match attempt above not matching those in the second.
 282        */
 283       state->variables_seen = variables_seen_stash;
 284
 285       if (!match_value(expr->srcs[0], instr, 1, num_components,
 286                        swizzle, state))
 287          return false;
 288
 289       return match_value(expr->srcs[1], instr, 0, num_components,
 290                          swizzle, state);
 291    } else {
 292       return false;
 293    }
 294 }
 295
 296 typedef struct bitsize_tree {
 297    unsigned num_srcs;
 298    struct bitsize_tree *srcs[4];
 299
 300    unsigned common_size;
 301    bool is_src_sized[4];
 302    bool is_dest_sized;
 303
 304    unsigned dest_size;
 305    unsigned src_size[4];
 306 } bitsize_tree;
 307
 308 static bitsize_tree *
 309 build_bitsize_tree(void *mem_ctx, struct match_state *state,
 310                    const nir_search_value *value)
 311 {
 312    bitsize_tree *tree = rzalloc(mem_ctx, bitsize_tree);
 313
 314    switch (value->type) {
 315    case nir_search_value_expression: {
 316       nir_search_expression *expr = nir_search_value_as_expression(value);
 317       nir_op_info info = nir_op_infos[expr->opcode];
 318       tree->num_srcs = info.num_inputs;
 319       tree->common_size = 0;
 320       for (unsigned i = 0; i < info.num_inputs; i++) {
 321          tree->is_src_sized[i] = !!nir_alu_type_get_type_size(info.input_types[i]);
 322          if (tree->is_src_sized[i])
 323             tree->src_size[i] = nir_alu_type_get_type_size(info.input_types[i]);
 324          tree->srcs[i] = build_bitsize_tree(mem_ctx, state, expr->srcs[i]);
 325       }
 326       tree->is_dest_sized = !!nir_alu_type_get_type_size(info.output_type);
 327       if (tree->is_dest_sized)
 328          tree->dest_size = nir_alu_type_get_type_size(info.output_type);
 329       break;
 330    }
 331
 332    case nir_search_value_variable: {
 333       nir_search_variable *var = nir_search_value_as_variable(value);
 334       tree->num_srcs = 0;
 335       tree->is_dest_sized = true;
 336       tree->dest_size = nir_src_bit_size(state->variables[var->variable].src);
 337       break;
 338    }
 339
 340    case nir_search_value_constant: {
 341       tree->num_srcs = 0;
 342       tree->is_dest_sized = false;
 343       tree->common_size = 0;
 344       break;
 345    }
 346    }
 347
 348    if (value->bit_size) {
 349       assert(!tree->is_dest_sized || tree->dest_size == value->bit_size);
 350       tree->common_size = value->bit_size;
 351    }
 352
 353    return tree;
 354 }
 355
 356 static unsigned
 357 bitsize_tree_filter_up(bitsize_tree *tree)
 358 {
 359    for (unsigned i = 0; i < tree->num_srcs; i++) {
 360       unsigned src_size = bitsize_tree_filter_up(tree->srcs[i]);
 361       if (src_size == 0)
 362          continue;
 363
 364       if (tree->is_src_sized[i]) {
 365          assert(src_size == tree->src_size[i]);
 366       } else if (tree->common_size != 0) {
 367          assert(src_size == tree->common_size);
 368          tree->src_size[i] = src_size;
 369       } else {
 370          tree->common_size = src_size;
 371          tree->src_size[i] = src_size;
 372       }
 373    }
 374
 375    if (tree->num_srcs && tree->common_size) {
 376       if (tree->dest_size == 0)
 377          tree->dest_size = tree->common_size;
 378       else if (!tree->is_dest_sized)
 379          assert(tree->dest_size == tree->common_size);
 380
 381       for (unsigned i = 0; i < tree->num_srcs; i++) {
 382          if (!tree->src_size[i])
 383             tree->src_size[i] = tree->common_size;
 384       }
 385    }
 386
 387    return tree->dest_size;
 388 }
 389
 390 static void
 391 bitsize_tree_filter_down(bitsize_tree *tree, unsigned size)
 392 {
 393    if (tree->dest_size)
 394       assert(tree->dest_size == size);
 395    else
 396       tree->dest_size = size;
 397
 398    if (!tree->is_dest_sized) {
 399       if (tree->common_size)
 400          assert(tree->common_size == size);
 401       else
 402          tree->common_size = size;
 403    }
 404
 405    for (unsigned i = 0; i < tree->num_srcs; i++) {
 406       if (!tree->src_size[i]) {
 407          assert(tree->common_size);
 408          tree->src_size[i] = tree->common_size;
 409       }
 410       bitsize_tree_filter_down(tree->srcs[i], tree->src_size[i]);
 411    }
 412 }
 413
 414 static nir_alu_src
 415 construct_value(const nir_search_value *value,
 416                 unsigned num_components, bitsize_tree *bitsize,
 417                 struct match_state *state,
 418                 nir_instr *instr, void *mem_ctx)
 419 {
 420    switch (value->type) {
 421    case nir_search_value_expression: {
 422       const nir_search_expression *expr = nir_search_value_as_expression(value);
 423
 424       if (nir_op_infos[expr->opcode].output_size != 0)
 425          num_components = nir_op_infos[expr->opcode].output_size;
 426
 427       nir_alu_instr *alu = nir_alu_instr_create(mem_ctx, expr->opcode);
 428       nir_ssa_dest_init(&alu->instr, &alu->dest.dest, num_components,
 429                         bitsize->dest_size, NULL);
 430       alu->dest.write_mask = (1 << num_components) - 1;
 431       alu->dest.saturate = false;
 432
 433       /* We have no way of knowing what values in a given search expression
 434        * map to a particular replacement value.  Therefore, if the
 435        * expression we are replacing has any exact values, the entire
 436        * replacement should be exact.
 437        */
 438       alu->exact = state->has_exact_alu;
 439
 440       for (unsigned i = 0; i < nir_op_infos[expr->opcode].num_inputs; i++) {
 441          /* If the source is an explicitly sized source, then we need to reset
 442           * the number of components to match.
 443           */
 444          if (nir_op_infos[alu->op].input_sizes[i] != 0)
 445             num_components = nir_op_infos[alu->op].input_sizes[i];
 446
 447          alu->src[i] = construct_value(expr->srcs[i],
 448                                        num_components, bitsize->srcs[i],
 449                                        state, instr, mem_ctx);
 450       }
 451
 452       nir_instr_insert_before(instr, &alu->instr);
 453
 454       nir_alu_src val;
 455       val.src = nir_src_for_ssa(&alu->dest.dest.ssa);
 456       val.negate = false;
 457       val.abs = false,
 458       memcpy(val.swizzle, identity_swizzle, sizeof val.swizzle);
 459
 460       return val;
 461    }
 462
 463    case nir_search_value_variable: {
 464       const nir_search_variable *var = nir_search_value_as_variable(value);
 465       assert(state->variables_seen & (1 << var->variable));
 466
 467       nir_alu_src val = { NIR_SRC_INIT };
 468       nir_alu_src_copy(&val, &state->variables[var->variable], mem_ctx);
 469
 470       assert(!var->is_constant);
 471
 472       return val;
 473    }
 474
 475    case nir_search_value_constant: {
 476       const nir_search_constant *c = nir_search_value_as_constant(value);
 477       nir_load_const_instr *load =
 478          nir_load_const_instr_create(mem_ctx, 1, bitsize->dest_size);
 479
 480       switch (c->type) {
 481       case nir_type_float:
 482          load->def.name = ralloc_asprintf(load, "%f", c->data.d);
 483          switch (bitsize->dest_size) {
 484          case 16:
 485             load->value.u16[0] = _mesa_float_to_half(c->data.d);
 486             break;
 487          case 32:
 488             load->value.f32[0] = c->data.d;
 489             break;
 490          case 64:
 491             load->value.f64[0] = c->data.d;
 492             break;
 493          default:
 494             unreachable("unknown bit size");
 495          }
 496          break;
 497
 498       case nir_type_int:
 499          load->def.name = ralloc_asprintf(load, "%" PRIi64, c->data.i);
 500          switch (bitsize->dest_size) {
 501          case 8:
 502             load->value.i8[0] = c->data.i;
 503             break;
 504          case 16:
 505             load->value.i16[0] = c->data.i;
 506             break;
 507          case 32:
 508             load->value.i32[0] = c->data.i;
 509             break;
 510          case 64:
 511             load->value.i64[0] = c->data.i;
 512             break;
 513          default:
 514             unreachable("unknown bit size");
 515          }
 516          break;
 517
 518       case nir_type_uint:
 519          load->def.name = ralloc_asprintf(load, "%" PRIu64, c->data.u);
 520          switch (bitsize->dest_size) {
 521          case 8:
 522             load->value.u8[0] = c->data.u;
 523             break;
 524          case 16:
 525             load->value.u16[0] = c->data.u;
 526             break;
 527          case 32:
 528             load->value.u32[0] = c->data.u;
 529             break;
 530          case 64:
 531             load->value.u64[0] = c->data.u;
 532             break;
 533          default:
 534             unreachable("unknown bit size");
 535          }
 536          break;
 537
 538       case nir_type_bool32:
 539          load->value.u32[0] = c->data.u;
 540          break;
 541       default:
 542          unreachable("Invalid alu source type");
 543       }
 544
 545       nir_instr_insert_before(instr, &load->instr);
 546
 547       nir_alu_src val;
 548       val.src = nir_src_for_ssa(&load->def);
 549       val.negate = false;
 550       val.abs = false,
 551       memset(val.swizzle, 0, sizeof val.swizzle);
 552
 553       return val;
 554    }
 555
 556    default:
 557       unreachable("Invalid search value type");
 558    }
 559 }
 560
 561 nir_alu_instr *
 562 nir_replace_instr(nir_alu_instr *instr, const nir_search_expression *search,
 563                   const nir_search_value *replace, void *mem_ctx)
 564 {
 565    uint8_t swizzle[NIR_MAX_VEC_COMPONENTS] = { 0 };
 566
 567    for (unsigned i = 0; i < instr->dest.dest.ssa.num_components; ++i)
 568       swizzle[i] = i;
 569
 570    assert(instr->dest.dest.is_ssa);
 571
 572    struct match_state state;
 573    state.inexact_match = false;
 574    state.has_exact_alu = false;
 575    state.variables_seen = 0;
 576
 577    if (!match_expression(search, instr, instr->dest.dest.ssa.num_components,
 578                          swizzle, &state))
 579       return NULL;
 580
 581    void *bitsize_ctx = ralloc_context(NULL);
 582    bitsize_tree *tree = build_bitsize_tree(bitsize_ctx, &state, replace);
 583    bitsize_tree_filter_up(tree);
 584    bitsize_tree_filter_down(tree, instr->dest.dest.ssa.bit_size);
 585
 586    /* Inserting a mov may be unnecessary.  However, it's much easier to
 587     * simply let copy propagation clean this up than to try to go through
 588     * and rewrite swizzles ourselves.
 589     */
 590    nir_alu_instr *mov = nir_alu_instr_create(mem_ctx, nir_op_imov);
 591    mov->dest.write_mask = instr->dest.write_mask;
 592    nir_ssa_dest_init(&mov->instr, &mov->dest.dest,
 593                      instr->dest.dest.ssa.num_components,
 594                      instr->dest.dest.ssa.bit_size, NULL);
 595
 596    mov->src[0] = construct_value(replace,
 597                                  instr->dest.dest.ssa.num_components, tree,
 598                                  &state, &instr->instr, mem_ctx);
 599    nir_instr_insert_before(&instr->instr, &mov->instr);
 600
 601    nir_ssa_def_rewrite_uses(&instr->dest.dest.ssa,
 602                             nir_src_for_ssa(&mov->dest.dest.ssa));
 603
 604    /* We know this one has no more uses because we just rewrote them all,
 605     * so we can remove it.  The rest of the matched expression, however, we
 606     * don't know so much about.  We'll just let dead code clean them up.
 607     */
 608    nir_instr_remove(&instr->instr);
 609
 610    ralloc_free(bitsize_ctx);
 611
 612    return mov;
 613 }