src/amd/compiler/aco_opt_value_numbering.cpp

   1 /*
   2  * Copyright © 2018 Valve 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  */
  24
  25 #include <map>
  26 #include <unordered_map>
  27 #include "aco_ir.h"
  28
  29 /*
  30  * Implements the algorithm for dominator-tree value numbering
  31  * from "Value Numbering" by Briggs, Cooper, and Simpson.
  32  */
  33
  34 namespace aco {
  35 namespace {
  36
  37 inline
  38 uint32_t murmur_32_scramble(uint32_t h, uint32_t k) {
  39    k *= 0xcc9e2d51;
  40    k = (k << 15) | (k >> 17);
  41    h ^= k * 0x1b873593;
  42    h = (h << 13) | (h >> 19);
  43    h = h * 5 + 0xe6546b64;
  44    return h;
  45 }
  46
  47 template<typename T>
  48 uint32_t hash_murmur_32(Instruction* instr)
  49 {
  50    uint32_t hash = uint32_t(instr->format) << 16 | uint32_t(instr->opcode);
  51
  52    for (const Operand& op : instr->operands)
  53       hash = murmur_32_scramble(hash, op.constantValue());
  54
  55    /* skip format, opcode and pass_flags */
  56    for (unsigned i = 2; i < (sizeof(T) >> 2); i++) {
  57       uint32_t u;
  58       /* Accesses it though a byte array, so doesn't violate the strict aliasing rule */
  59       memcpy(&u, reinterpret_cast<uint8_t *>(instr) + i * 4, 4);
  60       hash = murmur_32_scramble(hash, u);
  61    }
  62
  63    /* Finalize. */
  64    uint32_t len = instr->operands.size() + instr->definitions.size() + sizeof(T);
  65    hash ^= len;
  66    hash ^= hash >> 16;
  67    hash *= 0x85ebca6b;
  68    hash ^= hash >> 13;
  69    hash *= 0xc2b2ae35;
  70    hash ^= hash >> 16;
  71    return hash;
  72 }
  73
  74 struct InstrHash {
  75    /* This hash function uses the Murmur3 algorithm written by Austin Appleby
  76     * https://github.com/aappleby/smhasher/blob/master/src/MurmurHash3.cpp
  77     *
  78     * In order to calculate the expression set, only the right-hand-side of an
  79     * instruction is used for the hash, i.e. everything except the definitions.
  80     */
  81    std::size_t operator()(Instruction* instr) const
  82    {
  83       if (instr->isVOP3())
  84          return hash_murmur_32<VOP3A_instruction>(instr);
  85
  86       if (instr->isDPP())
  87          return hash_murmur_32<DPP_instruction>(instr);
  88
  89       if (instr->isSDWA())
  90          return hash_murmur_32<SDWA_instruction>(instr);
  91
  92       switch (instr->format) {
  93       case Format::SMEM:
  94          return hash_murmur_32<SMEM_instruction>(instr);
  95       case Format::VINTRP:
  96          return hash_murmur_32<Interp_instruction>(instr);
  97       case Format::DS:
  98          return hash_murmur_32<DS_instruction>(instr);
  99       case Format::SOPP:
 100          return hash_murmur_32<SOPP_instruction>(instr);
 101       case Format::SOPK:
 102          return hash_murmur_32<SOPK_instruction>(instr);
 103       case Format::EXP:
 104          return hash_murmur_32<Export_instruction>(instr);
 105       case Format::MUBUF:
 106          return hash_murmur_32<MUBUF_instruction>(instr);
 107       case Format::MIMG:
 108          return hash_murmur_32<MIMG_instruction>(instr);
 109       case Format::MTBUF:
 110          return hash_murmur_32<MTBUF_instruction>(instr);
 111       case Format::FLAT:
 112          return hash_murmur_32<FLAT_instruction>(instr);
 113       case Format::PSEUDO_BRANCH:
 114          return hash_murmur_32<Pseudo_branch_instruction>(instr);
 115       case Format::PSEUDO_REDUCTION:
 116          return hash_murmur_32<Pseudo_reduction_instruction>(instr);
 117       default:
 118          return hash_murmur_32<Instruction>(instr);
 119       }
 120    }
 121 };
 122
 123 struct InstrPred {
 124    bool operator()(Instruction* a, Instruction* b) const
 125    {
 126       if (a->format != b->format)
 127          return false;
 128       if (a->opcode != b->opcode)
 129          return false;
 130       if (a->operands.size() != b->operands.size() || a->definitions.size() != b->definitions.size())
 131          return false; /* possible with pseudo-instructions */
 132       for (unsigned i = 0; i < a->operands.size(); i++) {
 133          if (a->operands[i].isConstant()) {
 134             if (!b->operands[i].isConstant())
 135                return false;
 136             if (a->operands[i].constantValue() != b->operands[i].constantValue())
 137                return false;
 138          }
 139          else if (a->operands[i].isTemp()) {
 140             if (!b->operands[i].isTemp())
 141                return false;
 142             if (a->operands[i].tempId() != b->operands[i].tempId())
 143                return false;
 144          }
 145          else if (a->operands[i].isUndefined() ^ b->operands[i].isUndefined())
 146             return false;
 147          if (a->operands[i].isFixed()) {
 148             if (!b->operands[i].isFixed())
 149                return false;
 150             if (a->operands[i].physReg() != b->operands[i].physReg())
 151                return false;
 152             if (a->operands[i].physReg() == exec && a->pass_flags != b->pass_flags)
 153                return false;
 154          }
 155       }
 156       for (unsigned i = 0; i < a->definitions.size(); i++) {
 157          if (a->definitions[i].isTemp()) {
 158             if (!b->definitions[i].isTemp())
 159                return false;
 160             if (a->definitions[i].regClass() != b->definitions[i].regClass())
 161                return false;
 162          }
 163          if (a->definitions[i].isFixed()) {
 164             if (!b->definitions[i].isFixed())
 165                return false;
 166             if (a->definitions[i].physReg() != b->definitions[i].physReg())
 167                return false;
 168             if (a->definitions[i].physReg() == exec)
 169                return false;
 170          }
 171       }
 172
 173       if (a->opcode == aco_opcode::v_readfirstlane_b32)
 174          return a->pass_flags == b->pass_flags;
 175
 176       /* The results of VOPC depend on the exec mask if used for subgroup operations. */
 177       if ((uint32_t) a->format & (uint32_t) Format::VOPC && a->pass_flags != b->pass_flags)
 178          return false;
 179
 180       if (a->isVOP3()) {
 181          VOP3A_instruction* a3 = static_cast<VOP3A_instruction*>(a);
 182          VOP3A_instruction* b3 = static_cast<VOP3A_instruction*>(b);
 183          for (unsigned i = 0; i < 3; i++) {
 184             if (a3->abs[i] != b3->abs[i] ||
 185                 a3->neg[i] != b3->neg[i])
 186                return false;
 187          }
 188          return a3->clamp == b3->clamp &&
 189                 a3->omod == b3->omod &&
 190                 a3->opsel == b3->opsel;
 191       }
 192       if (a->isDPP()) {
 193          DPP_instruction* aDPP = static_cast<DPP_instruction*>(a);
 194          DPP_instruction* bDPP = static_cast<DPP_instruction*>(b);
 195          return aDPP->pass_flags == bDPP->pass_flags &&
 196                 aDPP->dpp_ctrl == bDPP->dpp_ctrl &&
 197                 aDPP->bank_mask == bDPP->bank_mask &&
 198                 aDPP->row_mask == bDPP->row_mask &&
 199                 aDPP->bound_ctrl == bDPP->bound_ctrl &&
 200                 aDPP->abs[0] == bDPP->abs[0] &&
 201                 aDPP->abs[1] == bDPP->abs[1] &&
 202                 aDPP->neg[0] == bDPP->neg[0] &&
 203                 aDPP->neg[1] == bDPP->neg[1];
 204       }
 205       if (a->isSDWA()) {
 206          SDWA_instruction* aSDWA = static_cast<SDWA_instruction*>(a);
 207          SDWA_instruction* bSDWA = static_cast<SDWA_instruction*>(b);
 208          return aSDWA->sel[0] == bSDWA->sel[0] &&
 209                 aSDWA->sel[1] == bSDWA->sel[1] &&
 210                 aSDWA->dst_sel == bSDWA->dst_sel &&
 211                 aSDWA->abs[0] == bSDWA->abs[0] &&
 212                 aSDWA->abs[1] == bSDWA->abs[1] &&
 213                 aSDWA->neg[0] == bSDWA->neg[0] &&
 214                 aSDWA->neg[1] == bSDWA->neg[1] &&
 215                 aSDWA->dst_preserve == bSDWA->dst_preserve &&
 216                 aSDWA->clamp == bSDWA->clamp &&
 217                 aSDWA->omod == bSDWA->omod;
 218       }
 219
 220       switch (a->format) {
 221          case Format::SOPK: {
 222             SOPK_instruction* aK = static_cast<SOPK_instruction*>(a);
 223             SOPK_instruction* bK = static_cast<SOPK_instruction*>(b);
 224             return aK->imm == bK->imm;
 225          }
 226          case Format::SMEM: {
 227             SMEM_instruction* aS = static_cast<SMEM_instruction*>(a);
 228             SMEM_instruction* bS = static_cast<SMEM_instruction*>(b);
 229             /* isel shouldn't be creating situations where this assertion fails */
 230             assert(aS->prevent_overflow == bS->prevent_overflow);
 231             return aS->can_reorder && bS->can_reorder &&
 232                    aS->glc == bS->glc && aS->nv == bS->nv &&
 233                    aS->prevent_overflow == bS->prevent_overflow;
 234          }
 235          case Format::VINTRP: {
 236             Interp_instruction* aI = static_cast<Interp_instruction*>(a);
 237             Interp_instruction* bI = static_cast<Interp_instruction*>(b);
 238             if (aI->attribute != bI->attribute)
 239                return false;
 240             if (aI->component != bI->component)
 241                return false;
 242             return true;
 243          }
 244          case Format::PSEUDO_REDUCTION: {
 245             Pseudo_reduction_instruction *aR = static_cast<Pseudo_reduction_instruction*>(a);
 246             Pseudo_reduction_instruction *bR = static_cast<Pseudo_reduction_instruction*>(b);
 247             return aR->pass_flags == bR->pass_flags &&
 248                    aR->reduce_op == bR->reduce_op &&
 249                    aR->cluster_size == bR->cluster_size;
 250          }
 251          case Format::MTBUF: {
 252             MTBUF_instruction* aM = static_cast<MTBUF_instruction *>(a);
 253             MTBUF_instruction* bM = static_cast<MTBUF_instruction *>(b);
 254             return aM->can_reorder && bM->can_reorder &&
 255                    aM->barrier == bM->barrier &&
 256                    aM->dfmt == bM->dfmt &&
 257                    aM->nfmt == bM->nfmt &&
 258                    aM->offset == bM->offset &&
 259                    aM->offen == bM->offen &&
 260                    aM->idxen == bM->idxen &&
 261                    aM->glc == bM->glc &&
 262                    aM->dlc == bM->dlc &&
 263                    aM->slc == bM->slc &&
 264                    aM->tfe == bM->tfe &&
 265                    aM->disable_wqm == bM->disable_wqm;
 266          }
 267          case Format::MUBUF: {
 268             MUBUF_instruction* aM = static_cast<MUBUF_instruction *>(a);
 269             MUBUF_instruction* bM = static_cast<MUBUF_instruction *>(b);
 270             return aM->can_reorder && bM->can_reorder &&
 271                    aM->barrier == bM->barrier &&
 272                    aM->offset == bM->offset &&
 273                    aM->offen == bM->offen &&
 274                    aM->idxen == bM->idxen &&
 275                    aM->glc == bM->glc &&
 276                    aM->dlc == bM->dlc &&
 277                    aM->slc == bM->slc &&
 278                    aM->tfe == bM->tfe &&
 279                    aM->lds == bM->lds &&
 280                    aM->disable_wqm == bM->disable_wqm;
 281          }
 282          /* we want to optimize these in NIR and don't hassle with load-store dependencies */
 283          case Format::FLAT:
 284          case Format::GLOBAL:
 285          case Format::SCRATCH:
 286          case Format::EXP:
 287          case Format::SOPP:
 288          case Format::PSEUDO_BRANCH:
 289          case Format::PSEUDO_BARRIER:
 290             return false;
 291          case Format::DS: {
 292             if (a->opcode != aco_opcode::ds_bpermute_b32 &&
 293                 a->opcode != aco_opcode::ds_permute_b32 &&
 294                 a->opcode != aco_opcode::ds_swizzle_b32)
 295                return false;
 296             DS_instruction* aD = static_cast<DS_instruction *>(a);
 297             DS_instruction* bD = static_cast<DS_instruction *>(b);
 298             return aD->pass_flags == bD->pass_flags &&
 299                    aD->gds == bD->gds &&
 300                    aD->offset0 == bD->offset0 &&
 301                    aD->offset1 == bD->offset1;
 302          }
 303          case Format::MIMG: {
 304             MIMG_instruction* aM = static_cast<MIMG_instruction*>(a);
 305             MIMG_instruction* bM = static_cast<MIMG_instruction*>(b);
 306             return aM->can_reorder && bM->can_reorder &&
 307                    aM->barrier == bM->barrier &&
 308                    aM->dmask == bM->dmask &&
 309                    aM->unrm == bM->unrm &&
 310                    aM->glc == bM->glc &&
 311                    aM->slc == bM->slc &&
 312                    aM->tfe == bM->tfe &&
 313                    aM->da == bM->da &&
 314                    aM->lwe == bM->lwe &&
 315                    aM->r128 == bM->r128 &&
 316                    aM->a16 == bM->a16 &&
 317                    aM->d16 == bM->d16 &&
 318                    aM->disable_wqm == bM->disable_wqm;
 319          }
 320          default:
 321             return true;
 322       }
 323    }
 324 };
 325
 326 using expr_set = std::unordered_map<Instruction*, uint32_t, InstrHash, InstrPred>;
 327
 328 struct vn_ctx {
 329    Program* program;
 330    expr_set expr_values;
 331    std::map<uint32_t, Temp> renames;
 332
 333    /* The exec id should be the same on the same level of control flow depth.
 334     * Together with the check for dominator relations, it is safe to assume
 335     * that the same exec_id also means the same execution mask.
 336     * Discards increment the exec_id, so that it won't return to the previous value.
 337     */
 338    uint32_t exec_id = 1;
 339
 340    vn_ctx(Program* program) : program(program) {
 341       static_assert(sizeof(Temp) == 4, "Temp must fit in 32bits");
 342       unsigned size = 0;
 343       for (Block& block : program->blocks)
 344          size += block.instructions.size();
 345       expr_values.reserve(size);
 346    }
 347 };
 348
 349
 350 /* dominates() returns true if the parent block dominates the child block and
 351  * if the parent block is part of the same loop or has a smaller loop nest depth.
 352  */
 353 bool dominates(vn_ctx& ctx, uint32_t parent, uint32_t child)
 354 {
 355    unsigned parent_loop_nest_depth = ctx.program->blocks[parent].loop_nest_depth;
 356    while (parent < child && parent_loop_nest_depth <= ctx.program->blocks[child].loop_nest_depth)
 357       child = ctx.program->blocks[child].logical_idom;
 358
 359    return parent == child;
 360 }
 361
 362 void process_block(vn_ctx& ctx, Block& block)
 363 {
 364    std::vector<aco_ptr<Instruction>> new_instructions;
 365    new_instructions.reserve(block.instructions.size());
 366
 367    for (aco_ptr<Instruction>& instr : block.instructions) {
 368       /* first, rename operands */
 369       for (Operand& op : instr->operands) {
 370          if (!op.isTemp())
 371             continue;
 372          auto it = ctx.renames.find(op.tempId());
 373          if (it != ctx.renames.end())
 374             op.setTemp(it->second);
 375       }
 376
 377       if (instr->opcode == aco_opcode::p_discard_if ||
 378           instr->opcode == aco_opcode::p_demote_to_helper)
 379          ctx.exec_id++;
 380
 381       if (instr->definitions.empty() || instr->opcode == aco_opcode::p_phi || instr->opcode == aco_opcode::p_linear_phi) {
 382          new_instructions.emplace_back(std::move(instr));
 383          continue;
 384       }
 385
 386       /* simple copy-propagation through renaming */
 387       if ((instr->opcode == aco_opcode::s_mov_b32 || instr->opcode == aco_opcode::s_mov_b64 || instr->opcode == aco_opcode::v_mov_b32) &&
 388           !instr->definitions[0].isFixed() && instr->operands[0].isTemp() && instr->operands[0].regClass() == instr->definitions[0].regClass() &&
 389           !instr->isDPP() && !((int)instr->format & (int)Format::SDWA)) {
 390          ctx.renames[instr->definitions[0].tempId()] = instr->operands[0].getTemp();
 391       }
 392
 393       instr->pass_flags = ctx.exec_id;
 394       std::pair<expr_set::iterator, bool> res = ctx.expr_values.emplace(instr.get(), block.index);
 395
 396       /* if there was already an expression with the same value number */
 397       if (!res.second) {
 398          Instruction* orig_instr = res.first->first;
 399          assert(instr->definitions.size() == orig_instr->definitions.size());
 400          /* check if the original instruction dominates the current one */
 401          if (dominates(ctx, res.first->second, block.index) &&
 402              ctx.program->blocks[res.first->second].fp_mode.canReplace(block.fp_mode)) {
 403             for (unsigned i = 0; i < instr->definitions.size(); i++) {
 404                assert(instr->definitions[i].regClass() == orig_instr->definitions[i].regClass());
 405                assert(instr->definitions[i].isTemp());
 406                ctx.renames[instr->definitions[i].tempId()] = orig_instr->definitions[i].getTemp();
 407                if (instr->definitions[i].isPrecise())
 408                   orig_instr->definitions[i].setPrecise(true);
 409                /* SPIR_V spec says that an instruction marked with NUW wrapping
 410                 * around is undefined behaviour, so we can break additions in
 411                 * other contexts.
 412                 */
 413                if (instr->definitions[i].isNUW())
 414                   orig_instr->definitions[i].setNUW(true);
 415             }
 416          } else {
 417             ctx.expr_values.erase(res.first);
 418             ctx.expr_values.emplace(instr.get(), block.index);
 419             new_instructions.emplace_back(std::move(instr));
 420          }
 421       } else {
 422          new_instructions.emplace_back(std::move(instr));
 423       }
 424    }
 425
 426    block.instructions = std::move(new_instructions);
 427 }
 428
 429 void rename_phi_operands(Block& block, std::map<uint32_t, Temp>& renames)
 430 {
 431    for (aco_ptr<Instruction>& phi : block.instructions) {
 432       if (phi->opcode != aco_opcode::p_phi && phi->opcode != aco_opcode::p_linear_phi)
 433          break;
 434
 435       for (Operand& op : phi->operands) {
 436          if (!op.isTemp())
 437             continue;
 438          auto it = renames.find(op.tempId());
 439          if (it != renames.end())
 440             op.setTemp(it->second);
 441       }
 442    }
 443 }
 444 } /* end namespace */
 445
 446
 447 void value_numbering(Program* program)
 448 {
 449    vn_ctx ctx(program);
 450    std::vector<unsigned> loop_headers;
 451
 452    for (Block& block : program->blocks) {
 453       assert(ctx.exec_id > 0);
 454       /* decrement exec_id when leaving nested control flow */
 455       if (block.kind & block_kind_loop_header)
 456          loop_headers.push_back(block.index);
 457       if (block.kind & block_kind_merge) {
 458          ctx.exec_id--;
 459       } else if (block.kind & block_kind_loop_exit) {
 460          ctx.exec_id -= program->blocks[loop_headers.back()].linear_preds.size();
 461          ctx.exec_id -= block.linear_preds.size();
 462          loop_headers.pop_back();
 463       }
 464
 465       if (block.logical_idom != -1)
 466          process_block(ctx, block);
 467       else
 468          rename_phi_operands(block, ctx.renames);
 469
 470       /* increment exec_id when entering nested control flow */
 471       if (block.kind & block_kind_branch ||
 472           block.kind & block_kind_loop_preheader ||
 473           block.kind & block_kind_break ||
 474           block.kind & block_kind_continue ||
 475           block.kind & block_kind_discard)
 476          ctx.exec_id++;
 477       else if (block.kind & block_kind_continue_or_break)
 478          ctx.exec_id += 2;
 479    }
 480
 481    /* rename loop header phi operands */
 482    for (Block& block : program->blocks) {
 483       if (block.kind & block_kind_loop_header)
 484          rename_phi_operands(block, ctx.renames);
 485    }
 486 }
 487
 488 }