amd/compiler/aco_statistics.cpp

/*
 * Copyright © 2020 Valve Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 *
 */

#include "aco_ir.h"

#include "util/crc32.h"

#include <algorithm>
#include <deque>
#include <set>
#include <vector>

namespace aco {

/* sgpr_presched/vgpr_presched */
void
collect_presched_stats(Program* program)
{
   RegisterDemand presched_demand;
   for (Block& block : program->blocks)
      presched_demand.update(block.register_demand);
   program->statistics[statistic_sgpr_presched] = presched_demand.sgpr;
   program->statistics[statistic_vgpr_presched] = presched_demand.vgpr;
}

class BlockCycleEstimator {
public:
   enum resource {
      null = 0,
      scalar,
      branch_sendmsg,
      valu,
      valu_complex,
      lds,
      export_gds,
      vmem,
      resource_count,
   };

   BlockCycleEstimator(Program* program_) : program(program_) {}

   Program* program;

   int32_t cur_cycle = 0;
   int32_t res_available[(int)BlockCycleEstimator::resource_count] = {0};
   unsigned res_usage[(int)BlockCycleEstimator::resource_count] = {0};
   int32_t reg_available[512] = {0};
   std::deque<int32_t> lgkm;
   std::deque<int32_t> exp;
   std::deque<int32_t> vm;
   std::deque<int32_t> vs;

   unsigned predict_cost(aco_ptr<Instruction>& instr);
   void add(aco_ptr<Instruction>& instr);
   void join(const BlockCycleEstimator& other);

private:
   unsigned get_waitcnt_cost(wait_imm imm);
   unsigned get_dependency_cost(aco_ptr<Instruction>& instr);

   void use_resources(aco_ptr<Instruction>& instr);
   int32_t cycles_until_res_available(aco_ptr<Instruction>& instr);
};

struct wait_counter_info {
   wait_counter_info(unsigned vm_, unsigned exp_, unsigned lgkm_, unsigned vs_)
       : vm(vm_), exp(exp_), lgkm(lgkm_), vs(vs_)
   {}

   unsigned vm;
   unsigned exp;
   unsigned lgkm;
   unsigned vs;
};

struct perf_info {
   int latency;

   BlockCycleEstimator::resource rsrc0;
   unsigned cost0;

   BlockCycleEstimator::resource rsrc1;
   unsigned cost1;
};

static perf_info
get_perf_info(Program* program, aco_ptr<Instruction>& instr)
{
   instr_class cls = instr_info.classes[(int)instr->opcode];

#define WAIT(res)          BlockCycleEstimator::res, 0
#define WAIT_USE(res, cnt) BlockCycleEstimator::res, cnt

   if (program->gfx_level >= GFX10) {
      /* fp64 might be incorrect */
      switch (cls) {
      case instr_class::valu32:
      case instr_class::valu_convert32:
      case instr_class::valu_fma: return {5, WAIT_USE(valu, 1)};
      case instr_class::valu64: return {6, WAIT_USE(valu, 2), WAIT_USE(valu_complex, 2)};
      case instr_class::valu_quarter_rate32:
         return {8, WAIT_USE(valu, 4), WAIT_USE(valu_complex, 4)};
      case instr_class::valu_transcendental32:
         return {10, WAIT_USE(valu, 1), WAIT_USE(valu_complex, 4)};
      case instr_class::valu_double: return {22, WAIT_USE(valu, 16), WAIT_USE(valu_complex, 16)};
      case instr_class::valu_double_add:
         return {22, WAIT_USE(valu, 16), WAIT_USE(valu_complex, 16)};
      case instr_class::valu_double_convert:
         return {22, WAIT_USE(valu, 16), WAIT_USE(valu_complex, 16)};
      case instr_class::valu_double_transcendental:
         return {24, WAIT_USE(valu, 16), WAIT_USE(valu_complex, 16)};
      case instr_class::salu: return {2, WAIT_USE(scalar, 1)};
      case instr_class::smem: return {0, WAIT_USE(scalar, 1)};
      case instr_class::branch:
      case instr_class::sendmsg: return {0, WAIT_USE(branch_sendmsg, 1)};
      case instr_class::ds:
         return instr->ds().gds ? perf_info{0, WAIT_USE(export_gds, 1)}
                                : perf_info{0, WAIT_USE(lds, 1)};
      case instr_class::exp: return {0, WAIT_USE(export_gds, 1)};
      case instr_class::vmem: return {0, WAIT_USE(vmem, 1)};
      case instr_class::barrier:
      case instr_class::waitcnt:
      case instr_class::other:
      default: return {0};
      }
   } else {
      switch (cls) {
      case instr_class::valu32: return {4, WAIT_USE(valu, 4)};
      case instr_class::valu_convert32: return {16, WAIT_USE(valu, 16)};
      case instr_class::valu64: return {8, WAIT_USE(valu, 8)};
      case instr_class::valu_quarter_rate32: return {16, WAIT_USE(valu, 16)};
      case instr_class::valu_fma:
         return program->dev.has_fast_fma32 ? perf_info{4, WAIT_USE(valu, 4)}
                                            : perf_info{16, WAIT_USE(valu, 16)};
      case instr_class::valu_transcendental32: return {16, WAIT_USE(valu, 16)};
      case instr_class::valu_double: return {64, WAIT_USE(valu, 64)};
      case instr_class::valu_double_add: return {32, WAIT_USE(valu, 32)};
      case instr_class::valu_double_convert: return {16, WAIT_USE(valu, 16)};
      case instr_class::valu_double_transcendental: return {64, WAIT_USE(valu, 64)};
      case instr_class::salu: return {4, WAIT_USE(scalar, 4)};
      case instr_class::smem: return {4, WAIT_USE(scalar, 4)};
      case instr_class::branch:
         return {8, WAIT_USE(branch_sendmsg, 8)};
         return {4, WAIT_USE(branch_sendmsg, 4)};
      case instr_class::ds:
         return instr->ds().gds ? perf_info{4, WAIT_USE(export_gds, 4)}
                                : perf_info{4, WAIT_USE(lds, 4)};
      case instr_class::exp: return {16, WAIT_USE(export_gds, 16)};
      case instr_class::vmem: return {4, WAIT_USE(vmem, 4)};
      case instr_class::barrier:
      case instr_class::waitcnt:
      case instr_class::other:
      default: return {4};
      }
   }

#undef WAIT_USE
#undef WAIT
}

void
BlockCycleEstimator::use_resources(aco_ptr<Instruction>& instr)
{
   perf_info perf = get_perf_info(program, instr);

   if (perf.rsrc0 != resource_count) {
      res_available[(int)perf.rsrc0] = cur_cycle + perf.cost0;
      res_usage[(int)perf.rsrc0] += perf.cost0;
   }

   if (perf.rsrc1 != resource_count) {
      res_available[(int)perf.rsrc1] = cur_cycle + perf.cost1;
      res_usage[(int)perf.rsrc1] += perf.cost1;
   }
}

int32_t
BlockCycleEstimator::cycles_until_res_available(aco_ptr<Instruction>& instr)
{
   perf_info perf = get_perf_info(program, instr);

   int32_t cost = 0;
   if (perf.rsrc0 != resource_count)
      cost = MAX2(cost, res_available[(int)perf.rsrc0] - cur_cycle);
   if (perf.rsrc1 != resource_count)
      cost = MAX2(cost, res_available[(int)perf.rsrc1] - cur_cycle);

   return cost;
}

static wait_counter_info
get_wait_counter_info(aco_ptr<Instruction>& instr)
{
   /* These numbers are all a bit nonsense. LDS/VMEM/SMEM/EXP performance
    * depends a lot on the situation. */

   if (instr->isEXP())
      return wait_counter_info(0, 16, 0, 0);

   if (instr->isFlatLike()) {
      unsigned lgkm = instr->isFlat() ? 20 : 0;
      if (!instr->definitions.empty())
         return wait_counter_info(320, 0, lgkm, 0);
      else
         return wait_counter_info(0, 0, lgkm, 320);
   }

   if (instr->isSMEM()) {
      if (instr->definitions.empty())
         return wait_counter_info(0, 0, 200, 0);
      if (instr->operands.empty()) /* s_memtime and s_memrealtime */
         return wait_counter_info(0, 0, 1, 0);

      bool likely_desc_load = instr->operands[0].size() == 2;
      bool soe = instr->operands.size() >= (!instr->definitions.empty() ? 3 : 4);
      bool const_offset =
         instr->operands[1].isConstant() && (!soe || instr->operands.back().isConstant());

      if (likely_desc_load || const_offset)
         return wait_counter_info(0, 0, 30, 0); /* likely to hit L0 cache */

      return wait_counter_info(0, 0, 200, 0);
   }

   if (instr->format == Format::DS)
      return wait_counter_info(0, 0, 20, 0);

   if (instr->isVMEM() && !instr->definitions.empty())
      return wait_counter_info(320, 0, 0, 0);

   if (instr->isVMEM() && instr->definitions.empty())
      return wait_counter_info(0, 0, 0, 320);

   return wait_counter_info(0, 0, 0, 0);
}

static wait_imm
get_wait_imm(Program* program, aco_ptr<Instruction>& instr)
{
   if (instr->opcode == aco_opcode::s_endpgm) {
      return wait_imm(0, 0, 0, 0);
   } else if (instr->opcode == aco_opcode::s_waitcnt) {
      return wait_imm(GFX10_3, instr->sopp().imm);
   } else if (instr->opcode == aco_opcode::s_waitcnt_vscnt) {
      return wait_imm(0, 0, 0, instr->sopk().imm);
   } else {
      unsigned max_lgkm_cnt = program->gfx_level >= GFX10 ? 62 : 14;
      unsigned max_exp_cnt = 6;
      unsigned max_vm_cnt = program->gfx_level >= GFX9 ? 62 : 14;
      unsigned max_vs_cnt = 62;

      wait_counter_info wait_info = get_wait_counter_info(instr);
      wait_imm imm;
      imm.lgkm = wait_info.lgkm ? max_lgkm_cnt : wait_imm::unset_counter;
      imm.exp = wait_info.exp ? max_exp_cnt : wait_imm::unset_counter;
      imm.vm = wait_info.vm ? max_vm_cnt : wait_imm::unset_counter;
      imm.vs = wait_info.vs ? max_vs_cnt : wait_imm::unset_counter;
      return imm;
   }
}

unsigned
BlockCycleEstimator::get_dependency_cost(aco_ptr<Instruction>& instr)
{
   int deps_available = cur_cycle;

   wait_imm imm = get_wait_imm(program, instr);
   if (imm.vm != wait_imm::unset_counter) {
      for (int i = 0; i < (int)vm.size() - imm.vm; i++)
         deps_available = MAX2(deps_available, vm[i]);
   }
   if (imm.exp != wait_imm::unset_counter) {
      for (int i = 0; i < (int)exp.size() - imm.exp; i++)
         deps_available = MAX2(deps_available, exp[i]);
   }
   if (imm.lgkm != wait_imm::unset_counter) {
      for (int i = 0; i < (int)lgkm.size() - imm.lgkm; i++)
         deps_available = MAX2(deps_available, lgkm[i]);
   }
   if (imm.vs != wait_imm::unset_counter) {
      for (int i = 0; i < (int)vs.size() - imm.vs; i++)
         deps_available = MAX2(deps_available, vs[i]);
   }

   if (instr->opcode == aco_opcode::s_endpgm) {
      for (unsigned i = 0; i < 512; i++)
         deps_available = MAX2(deps_available, reg_available[i]);
   } else if (program->gfx_level >= GFX10) {
      for (Operand& op : instr->operands) {
         if (op.isConstant() || op.isUndefined())
            continue;
         for (unsigned i = 0; i < op.size(); i++)
            deps_available = MAX2(deps_available, reg_available[op.physReg().reg() + i]);
      }
   }

   if (program->gfx_level < GFX10)
      deps_available = align(deps_available, 4);

   return deps_available - cur_cycle;
}

unsigned
BlockCycleEstimator::predict_cost(aco_ptr<Instruction>& instr)
{
   int32_t dep = get_dependency_cost(instr);
   return dep + std::max(cycles_until_res_available(instr) - dep, 0);
}

static bool
is_vector(aco_opcode op)
{
   switch (instr_info.classes[(int)op]) {
   case instr_class::valu32:
   case instr_class::valu_convert32:
   case instr_class::valu_fma:
   case instr_class::valu_double:
   case instr_class::valu_double_add:
   case instr_class::valu_double_convert:
   case instr_class::valu_double_transcendental:
   case instr_class::vmem:
   case instr_class::ds:
   case instr_class::exp:
   case instr_class::valu64:
   case instr_class::valu_quarter_rate32:
   case instr_class::valu_transcendental32: return true;
   default: return false;
   }
}

void
BlockCycleEstimator::add(aco_ptr<Instruction>& instr)
{
   perf_info perf = get_perf_info(program, instr);

   cur_cycle += get_dependency_cost(instr);

   unsigned start;
   bool dual_issue = program->gfx_level >= GFX10 && program->wave_size == 64 &&
                     is_vector(instr->opcode) && program->workgroup_size > 32;
   for (unsigned i = 0; i < (dual_issue ? 2 : 1); i++) {
      cur_cycle += cycles_until_res_available(instr);

      start = cur_cycle;
      use_resources(instr);

      /* GCN is in-order and doesn't begin the next instruction until the current one finishes */
      cur_cycle += program->gfx_level >= GFX10 ? 1 : perf.latency;
   }

   wait_imm imm = get_wait_imm(program, instr);
   while (lgkm.size() > imm.lgkm)
      lgkm.pop_front();
   while (exp.size() > imm.exp)
      exp.pop_front();
   while (vm.size() > imm.vm)
      vm.pop_front();
   while (vs.size() > imm.vs)
      vs.pop_front();

   wait_counter_info wait_info = get_wait_counter_info(instr);
   if (wait_info.exp)
      exp.push_back(cur_cycle + wait_info.exp);
   if (wait_info.lgkm)
      lgkm.push_back(cur_cycle + wait_info.lgkm);
   if (wait_info.vm)
      vm.push_back(cur_cycle + wait_info.vm);
   if (wait_info.vs)
      vs.push_back(cur_cycle + wait_info.vs);

   /* This is inaccurate but shouldn't affect anything after waitcnt insertion.
    * Before waitcnt insertion, this is necessary to consider memory operations.
    */
   int latency = MAX3(wait_info.exp, wait_info.lgkm, wait_info.vm);
   int32_t result_available = start + MAX2(perf.latency, latency);

   for (Definition& def : instr->definitions) {
      int32_t* available = &reg_available[def.physReg().reg()];
      for (unsigned i = 0; i < def.size(); i++)
         available[i] = MAX2(available[i], result_available);
   }
}

static void
join_queue(std::deque<int32_t>& queue, const std::deque<int32_t>& pred, int cycle_diff)
{
   for (unsigned i = 0; i < MIN2(queue.size(), pred.size()); i++)
      queue.rbegin()[i] = MAX2(queue.rbegin()[i], pred.rbegin()[i] + cycle_diff);
   for (int i = pred.size() - queue.size() - 1; i >= 0; i--)
      queue.push_front(pred[i] + cycle_diff);
}

void
BlockCycleEstimator::join(const BlockCycleEstimator& pred)
{
   assert(cur_cycle == 0);

   for (unsigned i = 0; i < (unsigned)resource_count; i++) {
      assert(res_usage[i] == 0);
      res_available[i] = MAX2(res_available[i], pred.res_available[i] - pred.cur_cycle);
   }

   for (unsigned i = 0; i < 512; i++)
      reg_available[i] = MAX2(reg_available[i], pred.reg_available[i] - pred.cur_cycle + cur_cycle);

   join_queue(lgkm, pred.lgkm, -pred.cur_cycle);
   join_queue(exp, pred.exp, -pred.cur_cycle);
   join_queue(vm, pred.vm, -pred.cur_cycle);
   join_queue(vs, pred.vs, -pred.cur_cycle);
}

/* instructions/branches/vmem_clauses/smem_clauses/cycles */
void
collect_preasm_stats(Program* program)
{
   for (Block& block : program->blocks) {
      std::set<Instruction*> vmem_clause;
      std::set<Instruction*> smem_clause;

      program->statistics[statistic_instructions] += block.instructions.size();

      for (aco_ptr<Instruction>& instr : block.instructions) {
         if (instr->isSOPP() && instr->sopp().block != -1)
            program->statistics[statistic_branches]++;

         if (instr->opcode == aco_opcode::p_constaddr)
            program->statistics[statistic_instructions] += 2;

         if ((instr->isVMEM() || instr->isScratch() || instr->isGlobal()) &&
             !instr->operands.empty()) {
            if (std::none_of(vmem_clause.begin(), vmem_clause.end(),
                             [&](Instruction* other)
                             { return should_form_clause(instr.get(), other); }))
               program->statistics[statistic_vmem_clauses]++;
            vmem_clause.insert(instr.get());
         } else {
            vmem_clause.clear();
         }

         if (instr->isSMEM() && !instr->operands.empty()) {
            if (std::none_of(smem_clause.begin(), smem_clause.end(),
                             [&](Instruction* other)
                             { return should_form_clause(instr.get(), other); }))
               program->statistics[statistic_smem_clauses]++;
            smem_clause.insert(instr.get());
         } else {
            smem_clause.clear();
         }
      }
   }

   double latency = 0;
   double usage[(int)BlockCycleEstimator::resource_count] = {0};
   std::vector<BlockCycleEstimator> blocks(program->blocks.size(), program);

   if (program->stage.has(SWStage::VS) && program->info.vs.has_prolog) {
      unsigned vs_input_latency = 320;
      for (Definition def : program->vs_inputs) {
         blocks[0].vm.push_back(vs_input_latency);
         for (unsigned i = 0; i < def.size(); i++)
            blocks[0].reg_available[def.physReg().reg() + i] = vs_input_latency;
      }
   }

   for (Block& block : program->blocks) {
      BlockCycleEstimator& block_est = blocks[block.index];
      for (unsigned pred : block.linear_preds)
         block_est.join(blocks[pred]);

      for (aco_ptr<Instruction>& instr : block.instructions) {
         unsigned before = block_est.cur_cycle;
         block_est.add(instr);
         instr->pass_flags = block_est.cur_cycle - before;
      }

      /* TODO: it would be nice to be able to consider estimated loop trip
       * counts used for loop unrolling.
       */

      /* TODO: estimate the trip_count of divergent loops (those which break
       * divergent) higher than of uniform loops
       */

      /* Assume loops execute 8-2 times, uniform branches are taken 50% the time,
       * and any lane in the wave takes a side of a divergent branch 75% of the
       * time.
       */
      double iter = 1.0;
      iter *= block.loop_nest_depth > 0 ? 8.0 : 1.0;
      iter *= block.loop_nest_depth > 1 ? 4.0 : 1.0;
      iter *= block.loop_nest_depth > 2 ? pow(2.0, block.loop_nest_depth - 2) : 1.0;
      iter *= pow(0.5, block.uniform_if_depth);
      iter *= pow(0.75, block.divergent_if_logical_depth);

      bool divergent_if_linear_else =
         block.logical_preds.empty() && block.linear_preds.size() == 1 &&
         block.linear_succs.size() == 1 &&
         program->blocks[block.linear_preds[0]].kind & (block_kind_branch | block_kind_invert);
      if (divergent_if_linear_else)
         iter *= 0.25;

      latency += block_est.cur_cycle * iter;
      for (unsigned i = 0; i < (unsigned)BlockCycleEstimator::resource_count; i++)
         usage[i] += block_est.res_usage[i] * iter;
   }

   /* This likely exaggerates the effectiveness of parallelism because it
    * ignores instruction ordering. It can assume there might be SALU/VALU/etc
    * work to from other waves while one is idle but that might not be the case
    * because those other waves have not reached such a point yet.
    */

   double parallelism = program->num_waves;
   for (unsigned i = 0; i < (unsigned)BlockCycleEstimator::resource_count; i++) {
      if (usage[i] > 0.0)
         parallelism = MIN2(parallelism, latency / usage[i]);
   }
   double waves_per_cycle = 1.0 / latency * parallelism;
   double wave64_per_cycle = waves_per_cycle * (program->wave_size / 64.0);

   double max_utilization = 1.0;
   if (program->workgroup_size != UINT_MAX)
      max_utilization =
         program->workgroup_size / (double)align(program->workgroup_size, program->wave_size);
   wave64_per_cycle *= max_utilization;

   program->statistics[statistic_latency] = round(latency);
   program->statistics[statistic_inv_throughput] = round(1.0 / wave64_per_cycle);

   if (debug_flags & DEBUG_PERF_INFO) {
      aco_print_program(program, stderr, print_no_ssa | print_perf_info);

      fprintf(stderr, "num_waves: %u\n", program->num_waves);
      fprintf(stderr, "salu_smem_usage: %f\n", usage[(int)BlockCycleEstimator::scalar]);
      fprintf(stderr, "branch_sendmsg_usage: %f\n",
              usage[(int)BlockCycleEstimator::branch_sendmsg]);
      fprintf(stderr, "valu_usage: %f\n", usage[(int)BlockCycleEstimator::valu]);
      fprintf(stderr, "valu_complex_usage: %f\n", usage[(int)BlockCycleEstimator::valu_complex]);
      fprintf(stderr, "lds_usage: %f\n", usage[(int)BlockCycleEstimator::lds]);
      fprintf(stderr, "export_gds_usage: %f\n", usage[(int)BlockCycleEstimator::export_gds]);
      fprintf(stderr, "vmem_usage: %f\n", usage[(int)BlockCycleEstimator::vmem]);
      fprintf(stderr, "latency: %f\n", latency);
      fprintf(stderr, "parallelism: %f\n", parallelism);
      fprintf(stderr, "max_utilization: %f\n", max_utilization);
      fprintf(stderr, "wave64_per_cycle: %f\n", wave64_per_cycle);
      fprintf(stderr, "\n");
   }
}

void
collect_postasm_stats(Program* program, const std::vector<uint32_t>& code)
{
   program->statistics[aco::statistic_hash] = util_hash_crc32(code.data(), code.size() * 4);
}

} // namespace aco