Method ComputeLoopRegisterPressure

source/opt/register_pressure.cpp:287–334

}

void RegisterLiveness::ComputeLoopRegisterPressure(
    const Loop& loop, RegionRegisterLiveness* loop_reg_pressure) const {
  loop_reg_pressure->Clear();

  const RegionRegisterLiveness* header_live_inout = Get(loop.GetHeaderBlock());
  loop_reg_pressure->live_in_ = header_live_inout->live_in_;

  std::unordered_set<uint32_t> exit_blocks;
  loop.GetExitBlocks(&exit_blocks);

  for (uint32_t bb_id : exit_blocks) {
    const RegionRegisterLiveness* live_inout = Get(bb_id);
    loop_reg_pressure->live_out_.insert(live_inout->live_in_.begin(),
                                        live_inout->live_in_.end());
  }

  std::unordered_set<uint32_t> seen_insn;
  for (Instruction* insn : loop_reg_pressure->live_out_) {
    loop_reg_pressure->AddRegisterClass(insn);
    seen_insn.insert(insn->result_id());
  }
  for (Instruction* insn : loop_reg_pressure->live_in_) {
    if (!seen_insn.count(insn->result_id())) {
      continue;
    }
    loop_reg_pressure->AddRegisterClass(insn);
    seen_insn.insert(insn->result_id());
  }

  loop_reg_pressure->used_registers_ = 0;

  for (uint32_t bb_id : loop.GetBlocks()) {
    BasicBlock* bb = context_->cfg()->block(bb_id);

    const RegionRegisterLiveness* live_inout = Get(bb_id);
    assert(live_inout != nullptr && "Basic block not processed");
    loop_reg_pressure->used_registers_ = std::max(
        loop_reg_pressure->used_registers_, live_inout->used_registers_);

    for (Instruction& insn : *bb) {
      if (insn.opcode() == spv::Op::OpPhi || !CreatesRegisterUsage(&insn) ||
          seen_insn.count(insn.result_id())) {
        continue;
      }
      loop_reg_pressure->AddRegisterClass(&insn);
    }
  }
}

void RegisterLiveness::SimulateFusion(
    const Loop& l1, const Loop& l2, RegionRegisterLiveness* sim_result) const {