src/amd/compiler/aco_lower_phis.cpp

   1 /*
   2  * Copyright © 2019 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  * Authors:
  24  *    Rhys Perry (pendingchaos02@gmail.com)
  25  *
  26  */
  27
  28 #include <map>
  29
  30 #include "aco_ir.h"
  31 #include "aco_builder.h"
  32 #include <algorithm>
  33
  34
  35 namespace aco {
  36
  37 struct ssa_state {
  38    bool checked_preds_for_uniform;
  39    bool all_preds_uniform;
  40
  41    bool needs_init;
  42    uint64_t cur_undef_operands;
  43
  44    unsigned phi_block_idx;
  45    unsigned loop_nest_depth;
  46    std::map<unsigned, unsigned> writes;
  47    std::vector<unsigned> latest;
  48 };
  49
  50 Operand get_ssa(Program *program, unsigned block_idx, ssa_state *state, bool before_write)
  51 {
  52    if (!before_write) {
  53       auto it = state->writes.find(block_idx);
  54       if (it != state->writes.end())
  55          return Operand(Temp(it->second, program->lane_mask));
  56       if (state->latest[block_idx])
  57          return Operand(Temp(state->latest[block_idx], program->lane_mask));
  58    }
  59
  60    Block& block = program->blocks[block_idx];
  61    size_t pred = block.linear_preds.size();
  62    if (pred == 0 || block.loop_nest_depth < state->loop_nest_depth) {
  63       return Operand(program->lane_mask);
  64    } else if (block.loop_nest_depth > state->loop_nest_depth) {
  65       Operand op = get_ssa(program, block_idx - 1, state, false);
  66       assert(!state->latest[block_idx]);
  67       state->latest[block_idx] = op.tempId();
  68       return op;
  69    } else if (pred == 1 || block.kind & block_kind_loop_exit) {
  70       Operand op = get_ssa(program, block.linear_preds[0], state, false);
  71       assert(!state->latest[block_idx]);
  72       state->latest[block_idx] = op.tempId();
  73       return op;
  74    } else if (block.kind & block_kind_loop_header &&
  75               !(program->blocks[state->phi_block_idx].kind & block_kind_loop_exit)) {
  76       return Operand(program->lane_mask);
  77    } else {
  78       unsigned res = program->allocateId();
  79       assert(!state->latest[block_idx]);
  80       state->latest[block_idx] = res;
  81
  82       aco_ptr<Pseudo_instruction> phi{create_instruction<Pseudo_instruction>(aco_opcode::p_linear_phi, Format::PSEUDO, pred, 1)};
  83       for (unsigned i = 0; i < pred; i++)
  84          phi->operands[i] = get_ssa(program, block.linear_preds[i], state, false);
  85       phi->definitions[0] = Definition(Temp{res, program->lane_mask});
  86       block.instructions.emplace(block.instructions.begin(), std::move(phi));
  87
  88       return Operand(Temp(res, program->lane_mask));
  89    }
  90 }
  91
  92 void insert_before_logical_end(Block *block, aco_ptr<Instruction> instr)
  93 {
  94    auto IsLogicalEnd = [] (const aco_ptr<Instruction>& instr) -> bool {
  95       return instr->opcode == aco_opcode::p_logical_end;
  96    };
  97    auto it = std::find_if(block->instructions.crbegin(), block->instructions.crend(), IsLogicalEnd);
  98
  99    if (it == block->instructions.crend()) {
 100       assert(block->instructions.back()->format == Format::PSEUDO_BRANCH);
 101       block->instructions.insert(std::prev(block->instructions.end()), std::move(instr));
 102    } else {
 103       block->instructions.insert(std::prev(it.base()), std::move(instr));
 104    }
 105 }
 106
 107 void build_merge_code(Program *program, Block *block, Definition dst, Operand prev, Operand cur)
 108 {
 109    Builder bld(program);
 110
 111    auto IsLogicalEnd = [] (const aco_ptr<Instruction>& instr) -> bool {
 112       return instr->opcode == aco_opcode::p_logical_end;
 113    };
 114    auto it = std::find_if(block->instructions.rbegin(), block->instructions.rend(), IsLogicalEnd);
 115    assert(it != block->instructions.rend());
 116    bld.reset(&block->instructions, std::prev(it.base()));
 117
 118    if (prev.isUndefined()) {
 119       bld.sop1(Builder::s_mov, dst, cur);
 120       return;
 121    }
 122
 123    bool prev_is_constant = prev.isConstant() && prev.constantValue64(true) + 1u < 2u;
 124    bool cur_is_constant = cur.isConstant() && cur.constantValue64(true) + 1u < 2u;
 125
 126    if (!prev_is_constant) {
 127       if (!cur_is_constant) {
 128          Temp tmp1 = bld.tmp(bld.lm), tmp2 = bld.tmp(bld.lm);
 129          bld.sop2(Builder::s_andn2, Definition(tmp1), bld.def(s1, scc), prev, Operand(exec, bld.lm));
 130          bld.sop2(Builder::s_and, Definition(tmp2), bld.def(s1, scc), cur, Operand(exec, bld.lm));
 131          bld.sop2(Builder::s_or, dst, bld.def(s1, scc), tmp1, tmp2);
 132       } else if (cur.constantValue64(true)) {
 133          bld.sop2(Builder::s_or, dst, bld.def(s1, scc), prev, Operand(exec, bld.lm));
 134       } else {
 135          bld.sop2(Builder::s_andn2, dst, bld.def(s1, scc), prev, Operand(exec, bld.lm));
 136       }
 137    } else if (prev.constantValue64(true)) {
 138       if (!cur_is_constant)
 139          bld.sop2(Builder::s_orn2, dst, bld.def(s1, scc), cur, Operand(exec, bld.lm));
 140       else if (cur.constantValue64(true))
 141          bld.sop1(Builder::s_mov, dst, program->wave_size == 64 ? Operand(UINT64_MAX) : Operand(UINT32_MAX));
 142       else
 143          bld.sop1(Builder::s_not, dst, bld.def(s1, scc), Operand(exec, bld.lm));
 144    } else {
 145       if (!cur_is_constant)
 146          bld.sop2(Builder::s_and, dst, bld.def(s1, scc), cur, Operand(exec, bld.lm));
 147       else if (cur.constantValue64(true))
 148          bld.sop1(Builder::s_mov, dst, Operand(exec, bld.lm));
 149       else
 150          bld.sop1(Builder::s_mov, dst, program->wave_size == 64 ? Operand((uint64_t)0u) : Operand(0u));
 151    }
 152 }
 153
 154 void lower_divergent_bool_phi(Program *program, ssa_state *state, Block *block, aco_ptr<Instruction>& phi)
 155 {
 156    Builder bld(program);
 157
 158    if (!state->checked_preds_for_uniform) {
 159       state->all_preds_uniform = !(block->kind & block_kind_merge);
 160       for (unsigned pred : block->logical_preds)
 161          state->all_preds_uniform = state->all_preds_uniform && (program->blocks[pred].kind & block_kind_uniform);
 162       state->checked_preds_for_uniform = true;
 163    }
 164
 165    if (state->all_preds_uniform) {
 166       assert(block->logical_preds.size() == block->linear_preds.size());
 167       phi->opcode = aco_opcode::p_linear_phi;
 168       return;
 169    }
 170
 171    state->latest.resize(program->blocks.size());
 172
 173    uint64_t undef_operands = 0;
 174    for (unsigned i = 0; i < phi->operands.size(); i++)
 175       undef_operands |= phi->operands[i].isUndefined() << i;
 176
 177    if (state->needs_init || undef_operands != state->cur_undef_operands ||
 178        block->logical_preds.size() > 64) {
 179       /* this only has to be done once per block unless the set of predecessors
 180        * which are undefined changes */
 181       state->cur_undef_operands = undef_operands;
 182       state->phi_block_idx = block->index;
 183       state->loop_nest_depth = block->loop_nest_depth;
 184       if (block->kind & block_kind_loop_exit) {
 185          state->loop_nest_depth += 1;
 186       }
 187       state->writes.clear();
 188       state->needs_init = false;
 189    }
 190    std::fill(state->latest.begin(), state->latest.end(), 0);
 191
 192    for (unsigned i = 0; i < phi->operands.size(); i++) {
 193       if (phi->operands[i].isUndefined())
 194          continue;
 195
 196       state->writes[block->logical_preds[i]] = program->allocateId();
 197    }
 198
 199    bool uniform_merge = block->kind & block_kind_loop_header;
 200
 201    for (unsigned i = 0; i < phi->operands.size(); i++) {
 202       Block *pred = &program->blocks[block->logical_preds[i]];
 203
 204       bool need_get_ssa = !uniform_merge;
 205       if (block->kind & block_kind_loop_header && !(pred->kind & block_kind_uniform))
 206          uniform_merge = false;
 207
 208       if (phi->operands[i].isUndefined())
 209          continue;
 210
 211       Operand cur(bld.lm);
 212       if (need_get_ssa)
 213          cur = get_ssa(program, pred->index, state, true);
 214       assert(cur.regClass() == bld.lm);
 215
 216       Temp new_cur = {state->writes.at(pred->index), program->lane_mask};
 217       assert(new_cur.regClass() == bld.lm);
 218
 219       if (i == 1 && (block->kind & block_kind_merge) && phi->operands[0].isConstant())
 220          cur = phi->operands[0];
 221       build_merge_code(program, pred, Definition(new_cur), cur, phi->operands[i]);
 222    }
 223
 224    unsigned num_preds = block->linear_preds.size();
 225    if (phi->operands.size() != num_preds) {
 226       Pseudo_instruction* new_phi{create_instruction<Pseudo_instruction>(aco_opcode::p_linear_phi, Format::PSEUDO, num_preds, 1)};
 227       new_phi->definitions[0] = phi->definitions[0];
 228       phi.reset(new_phi);
 229    } else {
 230       phi->opcode = aco_opcode::p_linear_phi;
 231    }
 232    assert(phi->operands.size() == num_preds);
 233
 234    for (unsigned i = 0; i < num_preds; i++)
 235       phi->operands[i] = get_ssa(program, block->linear_preds[i], state, false);
 236
 237    return;
 238 }
 239
 240 void lower_subdword_phis(Program *program, Block *block, aco_ptr<Instruction>& phi)
 241 {
 242    Builder bld(program);
 243    for (unsigned i = 0; i < phi->operands.size(); i++) {
 244       if (phi->operands[i].isUndefined())
 245          continue;
 246       if (phi->operands[i].regClass() == phi->definitions[0].regClass())
 247          continue;
 248
 249       assert(phi->operands[i].isTemp());
 250       Block *pred = &program->blocks[block->logical_preds[i]];
 251       Temp phi_src = phi->operands[i].getTemp();
 252
 253       assert(phi_src.regClass().type() == RegType::sgpr);
 254       Temp tmp = bld.tmp(RegClass(RegType::vgpr, phi_src.size()));
 255       insert_before_logical_end(pred, bld.pseudo(aco_opcode::p_create_vector, Definition(tmp), phi_src).get_ptr());
 256       Temp new_phi_src = bld.tmp(phi->definitions[0].regClass());
 257       insert_before_logical_end(pred, bld.pseudo(aco_opcode::p_extract_vector, Definition(new_phi_src), tmp, Operand(0u)).get_ptr());
 258
 259       phi->operands[i].setTemp(new_phi_src);
 260    }
 261    return;
 262 }
 263
 264 void lower_phis(Program* program)
 265 {
 266    ssa_state state;
 267
 268    for (Block& block : program->blocks) {
 269       state.checked_preds_for_uniform = false;
 270       state.needs_init = true;
 271       for (aco_ptr<Instruction>& phi : block.instructions) {
 272          if (phi->opcode == aco_opcode::p_phi) {
 273             assert(program->wave_size == 64 ? phi->definitions[0].regClass() != s1 : phi->definitions[0].regClass() != s2);
 274             if (phi->definitions[0].regClass() == program->lane_mask)
 275                lower_divergent_bool_phi(program, &state, &block, phi);
 276             else if (phi->definitions[0].regClass().is_subdword())
 277                lower_subdword_phis(program, &block, phi);
 278          } else if (!is_phi(phi)) {
 279             break;
 280          }
 281       }
 282    }
 283 }
 284
 285 }