gcc/gcc/graphite-optimize-isl.c

/* A scheduling optimizer for Graphite
   Copyright (C) 2012-2015 Free Software Foundation, Inc.
   Contributed by Tobias Grosser <tobias@grosser.es>.

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.

GCC is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

#define USES_ISL

#include "config.h"

#ifdef HAVE_isl

#include "system.h"
#include "coretypes.h"
#include "backend.h"
#include "cfghooks.h"
#include "tree.h"
#include "gimple.h"
#include "fold-const.h"
#include "gimple-iterator.h"
#include "tree-ssa-loop.h"
#include "cfgloop.h"
#include "tree-data-ref.h"
#include "params.h"
#include "dumpfile.h"

#include <isl/constraint.h>
#include <isl/set.h>
#include <isl/union_set.h>
#include <isl/map.h>
#include <isl/union_map.h>
#include <isl/schedule.h>
#include <isl/band.h>
#include <isl/aff.h>
#include <isl/options.h>
#include <isl/ctx.h>
#ifdef HAVE_ISL_OPTIONS_SET_SCHEDULE_SERIALIZE_SCCS
/* isl 0.15 or later.  */
#include <isl/schedule_node.h>
#include <isl/ast_build.h>
#endif

#include "graphite.h"

#ifdef HAVE_ISL_OPTIONS_SET_SCHEDULE_SERIALIZE_SCCS
/* isl 0.15 or later.  */

/* get_schedule_for_node_st - Improve schedule for the schedule node.
   Only Simple loop tiling is considered.  */

static __isl_give isl_schedule_node *
get_schedule_for_node_st (__isl_take isl_schedule_node *node, void *user)
{
  if (user)
    return node;

  if (isl_schedule_node_get_type (node) != isl_schedule_node_band
      || isl_schedule_node_n_children (node) != 1)
    return node;

  isl_space *space = isl_schedule_node_band_get_space (node);
  unsigned dims = isl_space_dim (space, isl_dim_set);
  isl_schedule_node *child = isl_schedule_node_get_child (node, 0);
  isl_schedule_node_type type = isl_schedule_node_get_type (child);
  isl_space_free (space);
  isl_schedule_node_free (child);

  if (type != isl_schedule_node_leaf)
    return node;

  if (dims <= 1 || !isl_schedule_node_band_get_permutable (node))
    {
      if (dump_file && dump_flags)
	fprintf (dump_file, "not tiled\n");
      return node;
    }

  /* Tile loops.  */
  space = isl_schedule_node_band_get_space (node);
  isl_multi_val *sizes = isl_multi_val_zero (space);
  long tile_size = PARAM_VALUE (PARAM_LOOP_BLOCK_TILE_SIZE);
  isl_ctx *ctx = isl_schedule_node_get_ctx (node);

  for (unsigned i = 0; i < dims; i++)
    {
      sizes = isl_multi_val_set_val (sizes, i,
				     isl_val_int_from_si (ctx, tile_size));
      if (dump_file && dump_flags)
	fprintf (dump_file, "tiled by %ld\n", tile_size);
    }

  node = isl_schedule_node_band_tile (node, sizes);
  node = isl_schedule_node_child (node, 0);

  return node;
}

/* get_schedule_map_st - Improve the schedule by performing other loop
   optimizations. _st ending is for schedule tree version of this
   function (see get_schedule_map below for the band forest version).

   Do a depth-first post-order traversal of the nodes in a schedule
   tree and apply get_schedule_for_node_st on them to improve the schedule.
  */

static __isl_give isl_union_map *
get_schedule_map_st (__isl_keep isl_schedule *schedule)
{

  schedule = isl_schedule_map_schedule_node_bottom_up (schedule,
						       get_schedule_for_node_st,
						       NULL);
  isl_union_map *schedule_map = isl_schedule_get_map (schedule);
  return schedule_map;
}
#else

/* get_tile_map - Create a map that describes a n-dimensonal tiling.

   get_tile_map creates a map from a n-dimensional scattering space into an
   2*n-dimensional scattering space. The map describes a rectangular tiling.

   Example:
     SCHEDULE_DIMENSIONS = 2, PARAMETER_DIMENSIONS = 1, TILE_SIZE = 32

    tile_map := [p0] -> {[s0, s1] -> [t0, t1, s0, s1]:
			 t0 % 32 = 0 and t0 <= s0 < t0 + 32 and
			 t1 % 32 = 0 and t1 <= s1 < t1 + 32}

   Before tiling:

   for (i = 0; i < N; i++)
     for (j = 0; j < M; j++)
	S(i,j)

   After tiling:

   for (t_i = 0; t_i < N; i+=32)
     for (t_j = 0; t_j < M; j+=32)
	for (i = t_i; i < min(t_i + 32, N); i++)  | Unknown that N % 32 = 0
	  for (j = t_j; j < t_j + 32; j++)        |   Known that M % 32 = 0
	    S(i,j)
  */

static isl_basic_map *
get_tile_map (isl_ctx *ctx, int schedule_dimensions, int tile_size)
{
  /* We construct

     tile_map := [p0] -> {[s0, s1] -> [t0, t1, p0, p1, a0, a1]:
			s0 = a0 * 32 and s0 = p0 and t0 <= p0 < t0 + 32 and
			s1 = a1 * 32 and s1 = p1 and t1 <= p1 < t1 + 32}

     and project out the auxilary dimensions a0 and a1.  */
  isl_space *space
    = isl_space_alloc (ctx, 0, schedule_dimensions, schedule_dimensions * 3);
  isl_basic_map *tile_map = isl_basic_map_universe (isl_space_copy (space));

  isl_local_space *local_space = isl_local_space_from_space (space);

  for (int x = 0; x < schedule_dimensions; x++)
    {
      int sX = x;
      int tX = x;
      int pX = schedule_dimensions + x;
      int aX = 2 * schedule_dimensions + x;

      isl_constraint *c;

      /* sX = aX * tile_size; */
      c = isl_equality_alloc (isl_local_space_copy (local_space));
      isl_constraint_set_coefficient_si (c, isl_dim_out, sX, 1);
      isl_constraint_set_coefficient_si (c, isl_dim_out, aX, -tile_size);
      tile_map = isl_basic_map_add_constraint (tile_map, c);

      /* pX = sX; */
      c = isl_equality_alloc (isl_local_space_copy (local_space));
      isl_constraint_set_coefficient_si (c, isl_dim_out, pX, 1);
      isl_constraint_set_coefficient_si (c, isl_dim_in, sX, -1);
      tile_map = isl_basic_map_add_constraint (tile_map, c);

      /* tX <= pX */
      c = isl_inequality_alloc (isl_local_space_copy (local_space));
      isl_constraint_set_coefficient_si (c, isl_dim_out, pX, 1);
      isl_constraint_set_coefficient_si (c, isl_dim_out, tX, -1);
      tile_map = isl_basic_map_add_constraint (tile_map, c);

      /* pX <= tX + (tile_size - 1) */
      c = isl_inequality_alloc (isl_local_space_copy (local_space));
      isl_constraint_set_coefficient_si (c, isl_dim_out, tX, 1);
      isl_constraint_set_coefficient_si (c, isl_dim_out, pX, -1);
      isl_constraint_set_constant_si (c, tile_size - 1);
      tile_map = isl_basic_map_add_constraint (tile_map, c);
    }

  /* Project out auxiliary dimensions.

     The auxiliary dimensions are transformed into existentially quantified
     ones.
     This reduces the number of visible scattering dimensions and allows isl
     to produces better code.  */
  tile_map =
      isl_basic_map_project_out (tile_map, isl_dim_out,
				 2 * schedule_dimensions, schedule_dimensions);
  isl_local_space_free (local_space);
  return tile_map;
}

/* get_schedule_for_band - Get the schedule for this BAND.

   Polly applies transformations like tiling on top of the isl calculated
   value.
   This can influence the number of scheduling dimension. The number of
   schedule dimensions is returned in DIMENSIONS.  */

static isl_union_map *
get_schedule_for_band (isl_band *band, int *dimensions)
{
  isl_union_map *partial_schedule;
  isl_ctx *ctx;
  isl_space *space;
  isl_basic_map *tile_map;
  isl_union_map *tile_umap;

  partial_schedule = isl_band_get_partial_schedule (band);
  *dimensions = isl_band_n_member (band);

  /* It does not make any sense to tile a band with just one dimension.  */
  if (*dimensions == 1)
    {
      if (dump_file && dump_flags)
	fprintf (dump_file, "not tiled\n");
      return partial_schedule;
    }

  if (dump_file && dump_flags)
    fprintf (dump_file, "tiled by %d\n",
	     PARAM_VALUE (PARAM_LOOP_BLOCK_TILE_SIZE));

  ctx = isl_union_map_get_ctx (partial_schedule);
  space = isl_union_map_get_space (partial_schedule);

  tile_map = get_tile_map (ctx, *dimensions,
			   PARAM_VALUE (PARAM_LOOP_BLOCK_TILE_SIZE));
  tile_umap = isl_union_map_from_map (isl_map_from_basic_map (tile_map));
  tile_umap = isl_union_map_align_params (tile_umap, space);
  *dimensions = 2 * *dimensions;

  return isl_union_map_apply_range (partial_schedule, tile_umap);
}


/* get_schedule_for_band_list - Get the scheduling map for a list of bands.

   We walk recursively the forest of bands to combine the schedules of the
   individual bands to the overall schedule.  In case tiling is requested,
   the individual bands are tiled.  */

static isl_union_map *
get_schedule_for_band_list (isl_band_list *band_list)
{
  int num_bands, i;
  isl_union_map *schedule;
  isl_ctx *ctx;

  ctx = isl_band_list_get_ctx (band_list);
  num_bands = isl_band_list_n_band (band_list);
  schedule = isl_union_map_empty (isl_space_params_alloc (ctx, 0));

  for (i = 0; i < num_bands; i++)
    {
      isl_band *band;
      isl_union_map *partial_schedule;
      int schedule_dimensions;
      isl_space *space;

      band = isl_band_list_get_band (band_list, i);
      partial_schedule = get_schedule_for_band (band, &schedule_dimensions);
      space = isl_union_map_get_space (partial_schedule);

      if (isl_band_has_children (band))
	{
	  isl_band_list *children = isl_band_get_children (band);
	  isl_union_map *suffixSchedule
	    = get_schedule_for_band_list (children);
	  partial_schedule
	    = isl_union_map_flat_range_product (partial_schedule,
						suffixSchedule);
	  isl_band_list_free (children);
	}

      schedule = isl_union_map_union (schedule, partial_schedule);

      isl_band_free (band);
      isl_space_free (space);
    }

  return schedule;
}

static isl_union_map *
get_schedule_map (isl_schedule *schedule)
{
  isl_band_list *bandList = isl_schedule_get_band_forest (schedule);
  isl_union_map *schedule_map = get_schedule_for_band_list (bandList);
  isl_band_list_free (bandList);
  return schedule_map;
}
#endif

static isl_stat
get_single_map (__isl_take isl_map *map, void *user)
{
  isl_map **single_map = (isl_map **)user;
  *single_map = map;
  return isl_stat_ok;
}

static void
apply_schedule_map_to_scop (scop_p scop, isl_union_map *schedule_map)
{
  int i;
  poly_bb_p pbb;

  FOR_EACH_VEC_ELT (scop->pbbs, i, pbb)
    {
      isl_set *domain = isl_set_copy (pbb->domain);
      isl_map *stmt_schedule;

      isl_union_map *stmt_band
	= isl_union_map_intersect_domain (isl_union_map_copy (schedule_map),
					  isl_union_set_from_set (domain));
      isl_union_map_foreach_map (stmt_band, get_single_map, &stmt_schedule);
      isl_map_free (pbb->transformed);
      pbb->transformed = stmt_schedule;
      isl_union_map_free (stmt_band);
    }
}

static isl_union_set *
scop_get_domains (scop_p scop ATTRIBUTE_UNUSED)
{
  int i;
  poly_bb_p pbb;
  isl_space *space = isl_set_get_space (scop->param_context);
  isl_union_set *res = isl_union_set_empty (space);

  FOR_EACH_VEC_ELT (scop->pbbs, i, pbb)
    res = isl_union_set_add_set (res, isl_set_copy (pbb->domain));

  return res;
}

static const int CONSTANT_BOUND = 20;

/* Compute the schedule for SCOP based on its parameters, domain and set of
   constraints.  Then apply the schedule to SCOP.  */

bool
optimize_isl (scop_p scop)
{
  int old_max_operations = isl_ctx_get_max_operations (scop->isl_context);
  int max_operations = PARAM_VALUE (PARAM_MAX_ISL_OPERATIONS);
  if (max_operations)
    isl_ctx_set_max_operations (scop->isl_context, max_operations);
  isl_options_set_on_error (scop->isl_context, ISL_ON_ERROR_CONTINUE);

  isl_union_set *domain = scop_get_domains (scop);
  isl_union_map *dependences = scop_get_dependences (scop);
  dependences
    = isl_union_map_gist_domain (dependences, isl_union_set_copy (domain));
  dependences
    = isl_union_map_gist_range (dependences, isl_union_set_copy (domain));
  isl_union_map *validity = dependences;
  isl_union_map *proximity = isl_union_map_copy (validity);

  isl_options_set_schedule_max_constant_term (scop->isl_context, CONSTANT_BOUND);
  isl_options_set_schedule_maximize_band_depth (scop->isl_context, 1);
#ifdef HAVE_ISL_OPTIONS_SET_SCHEDULE_SERIALIZE_SCCS
  /* isl 0.15 or later.  */
  isl_options_set_schedule_serialize_sccs (scop->isl_context, 0);
  isl_options_set_schedule_maximize_band_depth (scop->isl_context, 1);
  isl_options_set_schedule_max_constant_term (scop->isl_context, 20);
  isl_options_set_schedule_max_coefficient (scop->isl_context, 20);
  isl_options_set_tile_scale_tile_loops (scop->isl_context, 0);
  isl_options_set_coalesce_bounded_wrapping (scop->isl_context, 1);
  isl_options_set_ast_build_exploit_nested_bounds (scop->isl_context, 1);
  isl_options_set_ast_build_atomic_upper_bound (scop->isl_context, 1);
#else
  isl_options_set_schedule_fuse (scop->isl_context, ISL_SCHEDULE_FUSE_MIN);
#endif

  isl_schedule *schedule
    = isl_union_set_compute_schedule (domain, validity, proximity);
  isl_options_set_on_error (scop->isl_context, ISL_ON_ERROR_ABORT);

  isl_ctx_reset_operations (scop->isl_context);
  isl_ctx_set_max_operations (scop->isl_context, old_max_operations);
  if (!schedule || isl_ctx_last_error (scop->isl_context) == isl_error_quota)
    {
      if (dump_file && dump_flags)
	fprintf (dump_file, "isl timed out --param max-isl-operations=%d\n",
		 max_operations);
      if (schedule)
	isl_schedule_free (schedule);
      return false;
    }

#ifdef HAVE_ISL_OPTIONS_SET_SCHEDULE_SERIALIZE_SCCS
  /* isl 0.15 or later.  */
  isl_union_map *schedule_map = get_schedule_map_st (schedule);
#else
  isl_union_map *schedule_map = get_schedule_map (schedule);
#endif
  apply_schedule_map_to_scop (scop, schedule_map);

  isl_schedule_free (schedule);
  isl_union_map_free (schedule_map);
  return true;
}

#endif /* HAVE_isl */