triton/lib/codegen/analysis/layout.cc

#include <algorithm>
#include <numeric>
#include <iostream>
#include "triton/codegen/analysis/axes.h"
#include "triton/codegen/analysis/align.h"
#include "triton/codegen/analysis/layout.h"
#include "triton/ir/function.h"
#include "triton/ir/module.h"
#include "triton/ir/utils.h"

namespace triton{
namespace codegen{
namespace analysis{

/* -------------------------------- *
 *          Helper Functions        *
 * -------------------------------- */

inline unsigned clamp(unsigned x, unsigned a, unsigned b) {
  unsigned lo = std::min(a, b);
  unsigned hi = std::max(a, b);
  return std::min(std::max(x, lo), hi);
}

inline bool is_hmma_c(ir::value *v){
  bool result = false;
  if(auto *x = dynamic_cast<ir::dot_inst*>(v)){
    ir::value *a = x->get_operand(0);
    ir::type *a_ty = a->get_type();
    ir::value *b = x->get_operand(1);
    ir::type *b_ty = b->get_type();
    result = a_ty->get_scalar_ty()->is_half_ty() &&
             b_ty->get_scalar_ty()->is_half_ty();
  }
  return result;
}

inline void extract_io_use(ir::value *v, std::set<ir::value*>& result) {
  for(ir::user* u: v->get_users()){
    auto i = dynamic_cast<ir::io_inst*>(u);
    if(i && i->get_pointer_operand() == v)
      result.insert(v);
  }
}

inline void extract_dot_use(ir::value *v, ir::value*& result, size_t n) {
  for(ir::user* u: v->get_users()){
    auto i = dynamic_cast<ir::dot_inst*>(u);
    if(i && i->get_operand(n) == v)
      result = v;
  }
}

inline void extract_hmma_dot_use(ir::value *v, ir::value*& result, size_t n) {
  for(ir::user* u: v->get_users()){
    auto i = dynamic_cast<ir::dot_inst*>(u);
    if(i && is_hmma_c(i) && i->get_operand(n) == v)
      result = v;
  }
}


inline bool is_trans(ir::value *v) {
  if(dynamic_cast<ir::trans_inst *>(v)) {
    return true;
  }
  if(auto *phi = dynamic_cast<ir::instruction *>(v)) {
    bool result = true;
    for(ir::value *op: phi->ops())
      result = result && is_trans(op);
    return result;
  }
  return false;
}


/* -------------------------------- *
 *          Layout Visitor          *
 * -------------------------------- */

void layout_visitor::visit_layout(data_layout *layout) {
  layout->accept(this);
}


/* -------------------------------- *
 *        Base Data Layout          *
 * -------------------------------- */

data_layout::data_layout(id_t id,
                         const std::vector<int> &axes,
                         const std::vector<unsigned> &shape,
                         const std::vector<ir::value *> &values,
                         analysis::align* align): id_(id), axes_(axes), shape_(shape), values_(values) {
  // io pointer
  std::set<ir::value*> ptr;
  for(ir::value* v: values_)
    extract_io_use(v, ptr);
  order_.resize(axes_.size());
  std::iota(order_.begin(), order_.end(), 0);
  auto largest = std::max_element(ptr.begin(), ptr.end(), [&](ir::value *x, ir::value *y){
    std::pair<int, int> xx = {x->get_type()->get_tile_rank(), x->get_type()->get_tile_num_elements()};
    std::pair<int, int> yy = {y->get_type()->get_tile_rank(), y->get_type()->get_tile_num_elements()};
    return xx < yy;
  });
  if(*largest){
    auto max_contiguous = align->contiguous(*largest);
    std::sort(order_.begin(), order_.end(), [&](unsigned a, unsigned b) {
      return max_contiguous[a] > max_contiguous[b];
    });
  }
}

size_t data_layout::find_axis(int to_find) const {
  auto it = std::find(axes_.begin(), axes_.end(), to_find);
  return std::distance(axes_.begin(), it);
}


/* -------------------------------- *
 *           MMA Layout             *
 * -------------------------------- */

mma884_layout::mma884_layout(size_t num_warps,
                                     const std::vector<int>& axes,
                                     const std::vector<unsigned>& shape,
                                     const std::vector<ir::value *> &values,
                                     analysis::align* align): data_layout(HMMA_884, axes, shape, values, align) {
  /* fragments per warp */
  // try to make things as square as possible to maximize data re-use
  fpw_ = {1, 1, 1};
  std::vector<int> fpw_nm1;
  unsigned num_fragments = std::min<unsigned>((shape_[0]/8)*(shape_[1]/8), 4);
  do {
    fpw_nm1 = fpw_;
    if(fpw_[0]*fpw_[1] < num_fragments)
      fpw_[0] = clamp(fpw_[0]*2, 1, shape_[0] / 8);
    if(fpw_[0]*fpw_[1] < num_fragments)
      fpw_[1] = clamp(fpw_[1]*2, 1, shape_[1] / 8);
  }while(fpw_nm1 != fpw_);

  /* warps per tile */
  // try to make things as square as possible to maximize data re-use
  wpt_ = {1, 1, 1};
  std::vector<int> wpt_nm1;
  do{
    wpt_nm1 = wpt_;
    if(wpt_[0] * wpt_[1] * wpt_[2] < num_warps)
      wpt_[0] = clamp(wpt_[0]*2, 1, shape_[0] / (fpw_[0]*8));
    if(wpt_[0] * wpt_[1] * wpt_[2] < num_warps)
      wpt_[1] = clamp(wpt_[1]*2, 1, shape_[1] / (fpw_[1]*8));
  }while(wpt_nm1 != wpt_);

  /* sanity check */
  unsigned effective_num_warps = 1;
  for(size_t d = 0; d < shape.size(); d++)
    effective_num_warps *= wpt_[d];
//  if(num_warps != effective_num_warps)
//    throw std::runtime_error("cannot create a kernel with this amount of warps");
}


/* -------------------------------- *
 *         Scanline Layout          *
 * -------------------------------- */

scanline_layout::scanline_layout(size_t num_warps,
                                 const std::vector<int>& axes,
                                 const std::vector<unsigned>& shape,
                                 const std::vector<ir::value *> &values,
                                 analysis::align* align, target *tgt): data_layout(SCANLINE, axes, shape, values, align){
  unsigned size = std::accumulate(shape_.begin(), shape_.end(), 1, std::multiplies<int>());
  unsigned num_threads = tgt->is_gpu() ? num_warps * 32 : 1;
  nts_.resize(shape_.size());
  mts_.resize(shape_.size());
  bool is_dot = std::any_of(values.begin(), values.end(),
                            [&](ir::value* v) { return dynamic_cast<ir::dot_inst*>(v); });

  ir::value *ptr = nullptr;
  for(ir::value *v: values)
    for(ir::user *usr: v->get_users())
      if(auto *st = dynamic_cast<ir::store_inst*>(usr))
        ptr = st->get_pointer_operand();

  unsigned i = order_[0];
  int contiguous = 4;
  if(ptr)
    contiguous = std::min<int>(align->contiguous(ptr)[i], 4);

  nts_[i] = clamp(size / num_threads, 1, std::min<int>(contiguous, shape_[i]));
  mts_[i] = clamp(num_threads, 1, shape_[i] / nts_[i]);
  size /= shape_[i];
  num_threads /= mts_[i];
  if(is_dot)
    nts_[order_[1]] = clamp(size / num_threads, 1, std::min<int>(4, shape_[order_[1]]));
  for(size_t d = 1; d < shape_.size(); d++){
    i = order_[d];
    if(d > 1 || !is_dot)
      nts_[i] = 1;
    mts_[i] = clamp(num_threads, 1, shape_[i] / nts_[i]);
    num_threads = num_threads / mts_[i];
  }
  /* sanity check */
  unsigned effective_num_threads = 1;
  for(size_t d = 0; d < shape_.size(); d++)
    effective_num_threads *= mts_[d];

//  std::cout <<values.size() << " " << num_warps << " " << effective_num_threads << std::endl;
//  if(num_warps * 32 != effective_num_threads)
//    throw std::runtime_error("cannot create a kernel with this amount of warps");
}


/* -------------------------------- *
 *          Shared Layout           *
 * -------------------------------- */

bool shared_layout::is_loop_latch(ir::phi_node *phi, ir::instruction *terminator){
  if(phi->get_parent() != terminator->get_parent())
    return false;
  if(auto *br = dynamic_cast<ir::cond_branch_inst*>(terminator))
    return br->get_true_dest() == phi->get_parent()
           || br->get_false_dest() == phi->get_parent();
  else if(dynamic_cast<ir::uncond_branch_inst*>(terminator))
    return false;
  else
    throw std::runtime_error("unreachable");
}


void shared_layout::extract_double_bufferable(ir::value *v, std::shared_ptr<double_buffer_info_t>& res) {
  auto* phi = dynamic_cast<ir::phi_node*>(v);
  if(!phi || phi->get_num_incoming() != 2)
    return;
  ir::basic_block *block_0 = phi->get_incoming_block(0);
  ir::basic_block *block_1 = phi->get_incoming_block(1);
  ir::instruction *terminator_0 = block_0->get_inst_list().back();
  ir::instruction *terminator_1 = block_1->get_inst_list().back();
  bool is_latch_0 = is_loop_latch(phi, terminator_0);
  bool is_latch_1 = is_loop_latch(phi, terminator_1);
  ir::value *value_0 = phi->get_incoming_value(0);
  ir::value *value_1 = phi->get_incoming_value(1);
  ir::instruction *i_0 = dynamic_cast<ir::instruction*>(value_0);
  ir::instruction *i_1 = dynamic_cast<ir::instruction*>(value_1);
  if(!i_0 || !i_1 ||
     !dynamic_cast<ir::copy_to_shared_inst*>(i_0) ||
     !dynamic_cast<ir::copy_to_shared_inst*>(i_1) )
    return;
  if(is_latch_1)
    res.reset(new double_buffer_info_t{value_0, value_1, phi});
  if(is_latch_0)
    res.reset(new double_buffer_info_t{value_1, value_0, phi});
}


shared_layout::shared_layout(const data_layout *arg,
                                 const std::vector<int>& axes,
                                 const std::vector<unsigned>& shape,
                                 const std::vector<ir::value *> &values,
                                 ir::type *ty,
                                 analysis::align* align): data_layout(SHARED, axes, shape, values, align), ty_(ty) {

  size_ = 0;

  // double-buffering
  for(ir::value *v: values)
    extract_double_bufferable(v, double_buffer_);

  // order
  std::vector<int> arg_order = arg ? arg->get_order() : std::vector<int>{0};
  order_ = arg_order;

  ir::value* dot_a = nullptr;
  ir::value* dot_b = nullptr;
  ir::value* hmma_dot_a = nullptr;
  ir::value* hmma_dot_b = nullptr;
  for(ir::value* v: values){
    extract_dot_use(v, dot_a, 0);
    extract_dot_use(v, dot_b, 1);
    extract_hmma_dot_use(v, hmma_dot_a, 0);
    extract_hmma_dot_use(v, hmma_dot_b, 1);
  }


  // non-mma ordering
  std::vector<int> col = {0, 1};
  std::vector<int> row = {1, 0};
  for(size_t s = 2; s < get_rank(); s++){
    col.push_back(s);
    row.push_back(s);
  }
  bool is_nonhmma_dot_a = dot_a && !hmma_dot_a;
  bool is_nonhmma_dot_b = dot_b && !hmma_dot_b;
  if(is_nonhmma_dot_a)
    order_ = is_trans(dot_a) ? row : col;
  else if(is_nonhmma_dot_b)
    order_ = is_trans(dot_b) ? col : row;

  // padding
  size_t pad = 0;
  if(hmma_dot_a){
    bool row = is_trans(hmma_dot_a) ^ order_[0] != 0;
    pad = 24 - shape_[row ? 0 : 1] % 32;
  }
  else if(hmma_dot_b){
    bool row = is_trans(hmma_dot_b) ^ order_[0] != 0;
    pad = 24 - shape_[row ? 1 : 0] % 32;
  }
  else if(order_ != arg_order) {
    pad = 4;
  }
  shape_[order_[0]] += pad;

  // size
  size_ = ty_->get_primitive_size_in_bits() / 8;
  for(auto s: shape_)
     size_ *= s;
  if(double_buffer_)
    size_ *= 2;
}


/* -------------------------------- *
 * ---- Layouts Inference Pass ---- *
 * -------------------------------- */

layouts::layouts(analysis::axes *axes, analysis::align *align, size_t num_warps, target* tgt)
  : axes_(axes), align_(align), num_warps_(num_warps), tgt_(tgt){ }


void layouts::connect(ir::value *x, ir::value *y) {
  if(x == y)
    return;
  if(!x->get_type()->is_tile_ty())
    return;
  if(!y->get_type()->is_tile_ty())
    return;
  std::vector<int> x_axes = axes_->get(x);
  std::vector<int> y_axes = axes_->get(y);
  std::set<int> sx_axes(x_axes.begin(), x_axes.end());
  std::set<int> sy_axes(y_axes.begin(), y_axes.end());
  std::set<int> common;
  std::set_intersection(sx_axes.begin(), sx_axes.end(),
                        sy_axes.begin(), sy_axes.end(),
                        std::inserter(common, common.begin()));
  graph_.add_edge(x, x);
  graph_.add_edge(y, y);
  if(!common.empty())
    graph_.add_edge(x, y);
}

void layouts::make_graph(ir::instruction *i) {
  for(ir::value* opx: i->ops())
  for(ir::value* opy: i->ops()){
    connect(i, opx);
    connect(opx, opy);
  }
}

void layouts::create(size_t id, const std::vector<ir::value*>& values) {
  auto it_hmma_c = std::find_if(values.begin(), values.end(), &is_hmma_c);
  auto cmp = [](ir::value* x, ir::value *y) {
    std::pair<int, int> xx = {x->get_type()->get_tile_rank(), x->get_type()->get_tile_num_elements()};
    std::pair<int, int> yy = {y->get_type()->get_tile_rank(), y->get_type()->get_tile_num_elements()};
    return xx < yy;
  };
  std::vector<ir::value*> lvalue = values;
  std::remove_if(lvalue.begin(), lvalue.end(), [&](ir::value* v) { return dynamic_cast<ir::trans_inst*>(v); });
  ir::value *largest = *std::max_element(lvalue.begin(), lvalue.end(), cmp);
  const auto& axes = axes_->get(largest);
  const auto& shapes = largest->get_type()->get_tile_shapes();
  auto it_cts = std::find_if(values.begin(), values.end(), [](ir::value* v) {
      return dynamic_cast<ir::copy_to_shared_inst*>(v);
  });
  // type
  if(it_hmma_c != values.end())
    layouts_[id] = new mma884_layout(num_warps_, axes, shapes, values, align_);
  else if(it_cts != values.end()){
    ir::copy_to_shared_inst *cts = (ir::copy_to_shared_inst*)*it_cts;
    ir::value *arg = cts->get_operand(0);
    create(groups_.at(arg), values_.at(groups_.at(arg)));
    layouts_[id] = new shared_layout(get(arg), axes, shapes, values, largest->get_type()->get_scalar_ty(), align_);
  }
  else
    layouts_[id] = new scanline_layout(num_warps_, axes, shapes, values, align_, tgt_);
}

void layouts::run(ir::module &mod) {
  // make graph
  graph_.clear();
  ir::for_each_instruction(mod, [this](ir::instruction* i) {
    make_graph(i);
  });

  // connected components
  graph_.connected_components(&values_, &groups_);

  // create layouts
  for(const auto& x: values_)
    create(x.first, x.second);

  // create temporaries
  size_t id = values_.size();
  ir::for_each_instruction(mod, [this, &id](ir::instruction* i) {
    if(auto *red = dynamic_cast<ir::reduce_inst*>(i)) {
      id++;
      ir::value *arg = red->get_operand(0);
      unsigned axis = red->get_axis();
      // shape
      auto shapes = arg->get_type()->get_tile_shapes();
      scanline_layout *layout = get(arg)->to_scanline();
      shapes[axis] = layout->mts(axis);
      // create layout
      layouts_[id] = new shared_layout(layout, axes_->get(arg), shapes, {red}, red->get_type()->get_scalar_ty(), align_);
      tmp_[red] = id;
    }
    if(auto *recoalasce = dynamic_cast<ir::recoalesce_inst*>(i)){
      ir::value *val = recoalasce->get_operand(0);
      mma884_layout* in_layout = get(val)->to_mma884();
      scanline_layout* out_layout = get(i)->to_scanline();
      if(!in_layout || !out_layout)
        return;
      id++;
      ir::type::tile_shapes_t in_shape = val->get_type()->get_tile_shapes();
      ir::type::tile_shapes_t shape(in_shape.size());
      size_t ld = out_layout->get_order(0);
      shape[ld] = in_shape[ld];
      for(size_t k = 0; k < in_shape.size(); k++)
        if(k != ld)
          shape[k] = 4*in_layout->to_mma884()->fpw(k)*in_layout->to_mma884()->wpt(k);
      // create layout
      layouts_[id] = new shared_layout(out_layout, axes_->get(val), shape, {recoalasce}, val->get_type()->get_scalar_ty(), align_);
      tmp_[recoalasce] = id;
    }
    if(auto *atom = dynamic_cast<ir::atomic_cas_inst*>(i)){
      id++;
      layouts_[id] = new shared_layout(nullptr, {}, {1}, {atom}, atom->get_type()->get_scalar_ty(), align_);
      tmp_[atom] = id;
    }
  });
}

}
}
}