tree-loop-distribution.c (classify_partition): New parameter and better handle reduct...

[thirdparty/gcc.git] / gcc / tree-loop-distribution.c

/* Loop distribution.
   Copyright (C) 2006-2017 Free Software Foundation, Inc.
   Contributed by Georges-Andre Silber <Georges-Andre.Silber@ensmp.fr>
   and Sebastian Pop <sebastian.pop@amd.com>.

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/>.  */

/* This pass performs loop distribution: for example, the loop

   |DO I = 2, N
   |    A(I) = B(I) + C
   |    D(I) = A(I-1)*E
   |ENDDO

   is transformed to

   |DOALL I = 2, N
   |   A(I) = B(I) + C
   |ENDDO
   |
   |DOALL I = 2, N
   |   D(I) = A(I-1)*E
   |ENDDO

   This pass uses an RDG, Reduced Dependence Graph built on top of the
   data dependence relations.  The RDG is then topologically sorted to
   obtain a map of information producers/consumers based on which it
   generates the new loops.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "backend.h"
#include "tree.h"
#include "gimple.h"
#include "cfghooks.h"
#include "tree-pass.h"
#include "ssa.h"
#include "gimple-pretty-print.h"
#include "fold-const.h"
#include "cfganal.h"
#include "gimple-iterator.h"
#include "gimplify-me.h"
#include "stor-layout.h"
#include "tree-cfg.h"
#include "tree-ssa-loop-manip.h"
#include "tree-ssa-loop.h"
#include "tree-into-ssa.h"
#include "tree-ssa.h"
#include "cfgloop.h"
#include "tree-scalar-evolution.h"
#include "params.h"
#include "tree-vectorizer.h"


#define MAX_DATAREFS_NUM \
	((unsigned) PARAM_VALUE (PARAM_LOOP_MAX_DATAREFS_FOR_DATADEPS))

/* Hashtable helpers.  */

struct ddr_hasher : nofree_ptr_hash <struct data_dependence_relation>
{
  static inline hashval_t hash (const data_dependence_relation *);
  static inline bool equal (const data_dependence_relation *,
			    const data_dependence_relation *);
};

/* Hash function for data dependence.  */

inline hashval_t
ddr_hasher::hash (const data_dependence_relation *ddr)
{
  inchash::hash h;
  h.add_ptr (DDR_A (ddr));
  h.add_ptr (DDR_B (ddr));
  return h.end ();
}

/* Hash table equality function for data dependence.  */

inline bool
ddr_hasher::equal (const data_dependence_relation *ddr1,
		   const data_dependence_relation *ddr2)
{
  return (DDR_A (ddr1) == DDR_A (ddr2) && DDR_B (ddr1) == DDR_B (ddr2));
}

/* The loop (nest) to be distributed.  */
static vec<loop_p> loop_nest;

/* Vector of data references in the loop to be distributed.  */
static vec<data_reference_p> datarefs_vec;

/* Store index of data reference in aux field.  */
#define DR_INDEX(dr)      ((uintptr_t) (dr)->aux)

/* Hash table for data dependence relation in the loop to be distributed.  */
static hash_table<ddr_hasher> ddrs_table (389);


/* A Reduced Dependence Graph (RDG) vertex representing a statement.  */
struct rdg_vertex
{
  /* The statement represented by this vertex.  */
  gimple *stmt;

  /* Vector of data-references in this statement.  */
  vec<data_reference_p> datarefs;

  /* True when the statement contains a write to memory.  */
  bool has_mem_write;

  /* True when the statement contains a read from memory.  */
  bool has_mem_reads;
};

#define RDGV_STMT(V)     ((struct rdg_vertex *) ((V)->data))->stmt
#define RDGV_DATAREFS(V) ((struct rdg_vertex *) ((V)->data))->datarefs
#define RDGV_HAS_MEM_WRITE(V) ((struct rdg_vertex *) ((V)->data))->has_mem_write
#define RDGV_HAS_MEM_READS(V) ((struct rdg_vertex *) ((V)->data))->has_mem_reads
#define RDG_STMT(RDG, I) RDGV_STMT (&(RDG->vertices[I]))
#define RDG_DATAREFS(RDG, I) RDGV_DATAREFS (&(RDG->vertices[I]))
#define RDG_MEM_WRITE_STMT(RDG, I) RDGV_HAS_MEM_WRITE (&(RDG->vertices[I]))
#define RDG_MEM_READS_STMT(RDG, I) RDGV_HAS_MEM_READS (&(RDG->vertices[I]))

/* Data dependence type.  */

enum rdg_dep_type
{
  /* Read After Write (RAW).  */
  flow_dd = 'f',

  /* Control dependence (execute conditional on).  */
  control_dd = 'c'
};

/* Dependence information attached to an edge of the RDG.  */

struct rdg_edge
{
  /* Type of the dependence.  */
  enum rdg_dep_type type;
};

#define RDGE_TYPE(E)        ((struct rdg_edge *) ((E)->data))->type

/* Dump vertex I in RDG to FILE.  */

static void
dump_rdg_vertex (FILE *file, struct graph *rdg, int i)
{
  struct vertex *v = &(rdg->vertices[i]);
  struct graph_edge *e;

  fprintf (file, "(vertex %d: (%s%s) (in:", i,
	   RDG_MEM_WRITE_STMT (rdg, i) ? "w" : "",
	   RDG_MEM_READS_STMT (rdg, i) ? "r" : "");

  if (v->pred)
    for (e = v->pred; e; e = e->pred_next)
      fprintf (file, " %d", e->src);

  fprintf (file, ") (out:");

  if (v->succ)
    for (e = v->succ; e; e = e->succ_next)
      fprintf (file, " %d", e->dest);

  fprintf (file, ")\n");
  print_gimple_stmt (file, RDGV_STMT (v), 0, TDF_VOPS|TDF_MEMSYMS);
  fprintf (file, ")\n");
}

/* Call dump_rdg_vertex on stderr.  */

DEBUG_FUNCTION void
debug_rdg_vertex (struct graph *rdg, int i)
{
  dump_rdg_vertex (stderr, rdg, i);
}

/* Dump the reduced dependence graph RDG to FILE.  */

static void
dump_rdg (FILE *file, struct graph *rdg)
{
  fprintf (file, "(rdg\n");
  for (int i = 0; i < rdg->n_vertices; i++)
    dump_rdg_vertex (file, rdg, i);
  fprintf (file, ")\n");
}

/* Call dump_rdg on stderr.  */

DEBUG_FUNCTION void
debug_rdg (struct graph *rdg)
{
  dump_rdg (stderr, rdg);
}

static void
dot_rdg_1 (FILE *file, struct graph *rdg)
{
  int i;
  pretty_printer buffer;
  pp_needs_newline (&buffer) = false;
  buffer.buffer->stream = file;

  fprintf (file, "digraph RDG {\n");

  for (i = 0; i < rdg->n_vertices; i++)
    {
      struct vertex *v = &(rdg->vertices[i]);
      struct graph_edge *e;

      fprintf (file, "%d [label=\"[%d] ", i, i);
      pp_gimple_stmt_1 (&buffer, RDGV_STMT (v), 0, TDF_SLIM);
      pp_flush (&buffer);
      fprintf (file, "\"]\n");

      /* Highlight reads from memory.  */
      if (RDG_MEM_READS_STMT (rdg, i))
       fprintf (file, "%d [style=filled, fillcolor=green]\n", i);

      /* Highlight stores to memory.  */
      if (RDG_MEM_WRITE_STMT (rdg, i))
       fprintf (file, "%d [style=filled, fillcolor=red]\n", i);

      if (v->succ)
       for (e = v->succ; e; e = e->succ_next)
         switch (RDGE_TYPE (e))
           {
           case flow_dd:
             /* These are the most common dependences: don't print these. */
             fprintf (file, "%d -> %d \n", i, e->dest);
             break;

	   case control_dd:
             fprintf (file, "%d -> %d [label=control] \n", i, e->dest);
             break;

           default:
             gcc_unreachable ();
           }
    }

  fprintf (file, "}\n\n");
}

/* Display the Reduced Dependence Graph using dotty.  */

DEBUG_FUNCTION void
dot_rdg (struct graph *rdg)
{
  /* When debugging, you may want to enable the following code.  */
#ifdef HAVE_POPEN
  FILE *file = popen ("dot -Tx11", "w");
  if (!file)
    return;
  dot_rdg_1 (file, rdg);
  fflush (file);
  close (fileno (file));
  pclose (file);
#else
  dot_rdg_1 (stderr, rdg);
#endif
}

/* Returns the index of STMT in RDG.  */

static int
rdg_vertex_for_stmt (struct graph *rdg ATTRIBUTE_UNUSED, gimple *stmt)
{
  int index = gimple_uid (stmt);
  gcc_checking_assert (index == -1 || RDG_STMT (rdg, index) == stmt);
  return index;
}

/* Creates dependence edges in RDG for all the uses of DEF.  IDEF is
   the index of DEF in RDG.  */

static void
create_rdg_edges_for_scalar (struct graph *rdg, tree def, int idef)
{
  use_operand_p imm_use_p;
  imm_use_iterator iterator;

  FOR_EACH_IMM_USE_FAST (imm_use_p, iterator, def)
    {
      struct graph_edge *e;
      int use = rdg_vertex_for_stmt (rdg, USE_STMT (imm_use_p));

      if (use < 0)
	continue;

      e = add_edge (rdg, idef, use);
      e->data = XNEW (struct rdg_edge);
      RDGE_TYPE (e) = flow_dd;
    }
}

/* Creates an edge for the control dependences of BB to the vertex V.  */

static void
create_edge_for_control_dependence (struct graph *rdg, basic_block bb,
				    int v, control_dependences *cd)
{
  bitmap_iterator bi;
  unsigned edge_n;
  EXECUTE_IF_SET_IN_BITMAP (cd->get_edges_dependent_on (bb->index),
			    0, edge_n, bi)
    {
      basic_block cond_bb = cd->get_edge_src (edge_n);
      gimple *stmt = last_stmt (cond_bb);
      if (stmt && is_ctrl_stmt (stmt))
	{
	  struct graph_edge *e;
	  int c = rdg_vertex_for_stmt (rdg, stmt);
	  if (c < 0)
	    continue;

	  e = add_edge (rdg, c, v);
	  e->data = XNEW (struct rdg_edge);
	  RDGE_TYPE (e) = control_dd;
	}
    }
}

/* Creates the edges of the reduced dependence graph RDG.  */

static void
create_rdg_flow_edges (struct graph *rdg)
{
  int i;
  def_operand_p def_p;
  ssa_op_iter iter;

  for (i = 0; i < rdg->n_vertices; i++)
    FOR_EACH_PHI_OR_STMT_DEF (def_p, RDG_STMT (rdg, i),
			      iter, SSA_OP_DEF)
      create_rdg_edges_for_scalar (rdg, DEF_FROM_PTR (def_p), i);
}

/* Creates the edges of the reduced dependence graph RDG.  */

static void
create_rdg_cd_edges (struct graph *rdg, control_dependences *cd, loop_p loop)
{
  int i;

  for (i = 0; i < rdg->n_vertices; i++)
    {
      gimple *stmt = RDG_STMT (rdg, i);
      if (gimple_code (stmt) == GIMPLE_PHI)
	{
	  edge_iterator ei;
	  edge e;
	  FOR_EACH_EDGE (e, ei, gimple_bb (stmt)->preds)
	    if (flow_bb_inside_loop_p (loop, e->src))
	      create_edge_for_control_dependence (rdg, e->src, i, cd);
	}
      else
	create_edge_for_control_dependence (rdg, gimple_bb (stmt), i, cd);
    }
}

/* Build the vertices of the reduced dependence graph RDG.  Return false
   if that failed.  */

static bool
create_rdg_vertices (struct graph *rdg, vec<gimple *> stmts, loop_p loop)
{
  int i;
  gimple *stmt;

  FOR_EACH_VEC_ELT (stmts, i, stmt)
    {
      struct vertex *v = &(rdg->vertices[i]);

      /* Record statement to vertex mapping.  */
      gimple_set_uid (stmt, i);

      v->data = XNEW (struct rdg_vertex);
      RDGV_STMT (v) = stmt;
      RDGV_DATAREFS (v).create (0);
      RDGV_HAS_MEM_WRITE (v) = false;
      RDGV_HAS_MEM_READS (v) = false;
      if (gimple_code (stmt) == GIMPLE_PHI)
	continue;

      unsigned drp = datarefs_vec.length ();
      if (!find_data_references_in_stmt (loop, stmt, &datarefs_vec))
	return false;
      for (unsigned j = drp; j < datarefs_vec.length (); ++j)
	{
	  data_reference_p dr = datarefs_vec[j];
	  if (DR_IS_READ (dr))
	    RDGV_HAS_MEM_READS (v) = true;
	  else
	    RDGV_HAS_MEM_WRITE (v) = true;
	  RDGV_DATAREFS (v).safe_push (dr);
	}
    }
  return true;
}

/* Array mapping basic block's index to its topological order.  */
static int *bb_top_order_index;
/* And size of the array.  */
static int bb_top_order_index_size;

/* If X has a smaller topological sort number than Y, returns -1;
   if greater, returns 1.  */

static int
bb_top_order_cmp (const void *x, const void *y)
{
  basic_block bb1 = *(const basic_block *) x;
  basic_block bb2 = *(const basic_block *) y;

  gcc_assert (bb1->index < bb_top_order_index_size
	      && bb2->index < bb_top_order_index_size);
  gcc_assert (bb1 == bb2
	      || bb_top_order_index[bb1->index]
		 != bb_top_order_index[bb2->index]);

  return (bb_top_order_index[bb1->index] - bb_top_order_index[bb2->index]);
}

/* Initialize STMTS with all the statements of LOOP.  We use topological
   order to discover all statements.  The order is important because
   generate_loops_for_partition is using the same traversal for identifying
   statements in loop copies.  */

static void
stmts_from_loop (struct loop *loop, vec<gimple *> *stmts)
{
  unsigned int i;
  basic_block *bbs = get_loop_body_in_custom_order (loop, bb_top_order_cmp);

  for (i = 0; i < loop->num_nodes; i++)
    {
      basic_block bb = bbs[i];

      for (gphi_iterator bsi = gsi_start_phis (bb); !gsi_end_p (bsi);
	   gsi_next (&bsi))
	if (!virtual_operand_p (gimple_phi_result (bsi.phi ())))
	  stmts->safe_push (bsi.phi ());

      for (gimple_stmt_iterator bsi = gsi_start_bb (bb); !gsi_end_p (bsi);
	   gsi_next (&bsi))
	{
	  gimple *stmt = gsi_stmt (bsi);
	  if (gimple_code (stmt) != GIMPLE_LABEL && !is_gimple_debug (stmt))
	    stmts->safe_push (stmt);
	}
    }

  free (bbs);
}

/* Free the reduced dependence graph RDG.  */

static void
free_rdg (struct graph *rdg)
{
  int i;

  for (i = 0; i < rdg->n_vertices; i++)
    {
      struct vertex *v = &(rdg->vertices[i]);
      struct graph_edge *e;

      for (e = v->succ; e; e = e->succ_next)
	free (e->data);

      if (v->data)
	{
	  gimple_set_uid (RDGV_STMT (v), -1);
	  (RDGV_DATAREFS (v)).release ();
	  free (v->data);
	}
    }

  free_graph (rdg);
}

/* Build the Reduced Dependence Graph (RDG) with one vertex per statement of
   LOOP, and one edge per flow dependence or control dependence from control
   dependence CD.  During visiting each statement, data references are also
   collected and recorded in global data DATAREFS_VEC.  */

static struct graph *
build_rdg (struct loop *loop, control_dependences *cd)
{
  struct graph *rdg;

  /* Create the RDG vertices from the stmts of the loop nest.  */
  auto_vec<gimple *, 10> stmts;
  stmts_from_loop (loop, &stmts);
  rdg = new_graph (stmts.length ());
  if (!create_rdg_vertices (rdg, stmts, loop))
    {
      free_rdg (rdg);
      return NULL;
    }
  stmts.release ();

  create_rdg_flow_edges (rdg);
  if (cd)
    create_rdg_cd_edges (rdg, cd, loop);

  return rdg;
}


/* Kind of distributed loop.  */
enum partition_kind {
    PKIND_NORMAL, PKIND_MEMSET, PKIND_MEMCPY, PKIND_MEMMOVE
};

/* Type of distributed loop.  */
enum partition_type {
    /* The distributed loop can be executed parallelly.  */
    PTYPE_PARALLEL = 0,
    /* The distributed loop has to be executed sequentially.  */
    PTYPE_SEQUENTIAL
};

/* Partition for loop distribution.  */
struct partition
{
  /* Statements of the partition.  */
  bitmap stmts;
  /* Loops of the partition.  */
  bitmap loops;
  /* True if the partition defines variable which is used outside of loop.  */
  bool reduction_p;
  /* For builtin partition, true if it executes one iteration more than
     number of loop (latch) iterations.  */
  bool plus_one;
  enum partition_kind kind;
  enum partition_type type;
  /* data-references a kind != PKIND_NORMAL partition is about.  */
  data_reference_p main_dr;
  data_reference_p secondary_dr;
  /* Number of loop (latch) iterations.  */
  tree niter;
  /* Data references in the partition.  */
  bitmap datarefs;
};


/* Allocate and initialize a partition from BITMAP.  */

static partition *
partition_alloc (void)
{
  partition *partition = XCNEW (struct partition);
  partition->stmts = BITMAP_ALLOC (NULL);
  partition->loops = BITMAP_ALLOC (NULL);
  partition->reduction_p = false;
  partition->kind = PKIND_NORMAL;
  partition->datarefs = BITMAP_ALLOC (NULL);
  return partition;
}

/* Free PARTITION.  */

static void
partition_free (partition *partition)
{
  BITMAP_FREE (partition->stmts);
  BITMAP_FREE (partition->loops);
  BITMAP_FREE (partition->datarefs);
  free (partition);
}

/* Returns true if the partition can be generated as a builtin.  */

static bool
partition_builtin_p (partition *partition)
{
  return partition->kind != PKIND_NORMAL;
}

/* Returns true if the partition contains a reduction.  */

static bool
partition_reduction_p (partition *partition)
{
  return partition->reduction_p;
}

/* Partitions are fused because of different reasons.  */
enum fuse_type
{
  FUSE_NON_BUILTIN = 0,
  FUSE_REDUCTION = 1,
  FUSE_SHARE_REF = 2,
  FUSE_SAME_SCC = 3,
  FUSE_FINALIZE = 4
};

/* Description on different fusing reason.  */
static const char *fuse_message[] = {
  "they are non-builtins",
  "they have reductions",
  "they have shared memory refs",
  "they are in the same dependence scc",
  "there is no point to distribute loop"};

static void
update_type_for_merge (struct graph *, partition *, partition *);

/* Merge PARTITION into the partition DEST.  RDG is the reduced dependence
   graph and we update type for result partition if it is non-NULL.  */

static void
partition_merge_into (struct graph *rdg, partition *dest,
		      partition *partition, enum fuse_type ft)
{
  if (dump_file && (dump_flags & TDF_DETAILS))
    {
      fprintf (dump_file, "Fuse partitions because %s:\n", fuse_message[ft]);
      fprintf (dump_file, "  Part 1: ");
      dump_bitmap (dump_file, dest->stmts);
      fprintf (dump_file, "  Part 2: ");
      dump_bitmap (dump_file, partition->stmts);
    }

  dest->kind = PKIND_NORMAL;
  if (dest->type == PTYPE_PARALLEL)
    dest->type = partition->type;

  bitmap_ior_into (dest->stmts, partition->stmts);
  if (partition_reduction_p (partition))
    dest->reduction_p = true;

  /* Further check if any data dependence prevents us from executing the
     new partition parallelly.  */
  if (dest->type == PTYPE_PARALLEL && rdg != NULL)
    update_type_for_merge (rdg, dest, partition);

  bitmap_ior_into (dest->datarefs, partition->datarefs);
}


/* Returns true when DEF is an SSA_NAME defined in LOOP and used after
   the LOOP.  */

static bool
ssa_name_has_uses_outside_loop_p (tree def, loop_p loop)
{
  imm_use_iterator imm_iter;
  use_operand_p use_p;

  FOR_EACH_IMM_USE_FAST (use_p, imm_iter, def)
    {
      gimple *use_stmt = USE_STMT (use_p);
      if (!is_gimple_debug (use_stmt)
	  && loop != loop_containing_stmt (use_stmt))
	return true;
    }

  return false;
}

/* Returns true when STMT defines a scalar variable used after the
   loop LOOP.  */

static bool
stmt_has_scalar_dependences_outside_loop (loop_p loop, gimple *stmt)
{
  def_operand_p def_p;
  ssa_op_iter op_iter;

  if (gimple_code (stmt) == GIMPLE_PHI)
    return ssa_name_has_uses_outside_loop_p (gimple_phi_result (stmt), loop);

  FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, op_iter, SSA_OP_DEF)
    if (ssa_name_has_uses_outside_loop_p (DEF_FROM_PTR (def_p), loop))
      return true;

  return false;
}

/* Return a copy of LOOP placed before LOOP.  */

static struct loop *
copy_loop_before (struct loop *loop)
{
  struct loop *res;
  edge preheader = loop_preheader_edge (loop);

  initialize_original_copy_tables ();
  res = slpeel_tree_duplicate_loop_to_edge_cfg (loop, NULL, preheader);
  gcc_assert (res != NULL);
  free_original_copy_tables ();
  delete_update_ssa ();

  return res;
}

/* Creates an empty basic block after LOOP.  */

static void
create_bb_after_loop (struct loop *loop)
{
  edge exit = single_exit (loop);

  if (!exit)
    return;

  split_edge (exit);
}

/* Generate code for PARTITION from the code in LOOP.  The loop is
   copied when COPY_P is true.  All the statements not flagged in the
   PARTITION bitmap are removed from the loop or from its copy.  The
   statements are indexed in sequence inside a basic block, and the
   basic blocks of a loop are taken in dom order.  */

static void
generate_loops_for_partition (struct loop *loop, partition *partition,
			      bool copy_p)
{
  unsigned i;
  basic_block *bbs;

  if (copy_p)
    {
      loop = copy_loop_before (loop);
      gcc_assert (loop != NULL);
      create_preheader (loop, CP_SIMPLE_PREHEADERS);
      create_bb_after_loop (loop);
    }

  /* Remove stmts not in the PARTITION bitmap.  */
  bbs = get_loop_body_in_dom_order (loop);

  if (MAY_HAVE_DEBUG_STMTS)
    for (i = 0; i < loop->num_nodes; i++)
      {
	basic_block bb = bbs[i];

	for (gphi_iterator bsi = gsi_start_phis (bb); !gsi_end_p (bsi);
	     gsi_next (&bsi))
	  {
	    gphi *phi = bsi.phi ();
	    if (!virtual_operand_p (gimple_phi_result (phi))
		&& !bitmap_bit_p (partition->stmts, gimple_uid (phi)))
	      reset_debug_uses (phi);
	  }

	for (gimple_stmt_iterator bsi = gsi_start_bb (bb); !gsi_end_p (bsi); gsi_next (&bsi))
	  {
	    gimple *stmt = gsi_stmt (bsi);
	    if (gimple_code (stmt) != GIMPLE_LABEL
		&& !is_gimple_debug (stmt)
		&& !bitmap_bit_p (partition->stmts, gimple_uid (stmt)))
	      reset_debug_uses (stmt);
	  }
      }

  for (i = 0; i < loop->num_nodes; i++)
    {
      basic_block bb = bbs[i];

      for (gphi_iterator bsi = gsi_start_phis (bb); !gsi_end_p (bsi);)
	{
	  gphi *phi = bsi.phi ();
	  if (!virtual_operand_p (gimple_phi_result (phi))
	      && !bitmap_bit_p (partition->stmts, gimple_uid (phi)))
	    remove_phi_node (&bsi, true);
	  else
	    gsi_next (&bsi);
	}

      for (gimple_stmt_iterator bsi = gsi_start_bb (bb); !gsi_end_p (bsi);)
	{
	  gimple *stmt = gsi_stmt (bsi);
	  if (gimple_code (stmt) != GIMPLE_LABEL
	      && !is_gimple_debug (stmt)
	      && !bitmap_bit_p (partition->stmts, gimple_uid (stmt)))
	    {
	      /* Choose an arbitrary path through the empty CFG part
		 that this unnecessary control stmt controls.  */
	      if (gcond *cond_stmt = dyn_cast <gcond *> (stmt))
		{
		  gimple_cond_make_false (cond_stmt);
		  update_stmt (stmt);
		}
	      else if (gimple_code (stmt) == GIMPLE_SWITCH)
		{
		  gswitch *switch_stmt = as_a <gswitch *> (stmt);
		  gimple_switch_set_index
		      (switch_stmt, CASE_LOW (gimple_switch_label (switch_stmt, 1)));
		  update_stmt (stmt);
		}
	      else
		{
		  unlink_stmt_vdef (stmt);
		  gsi_remove (&bsi, true);
		  release_defs (stmt);
		  continue;
		}
	    }
	  gsi_next (&bsi);
	}
    }

  free (bbs);
}

/* Build the size argument for a memory operation call.  */

static tree
build_size_arg_loc (location_t loc, data_reference_p dr, tree nb_iter,
		    bool plus_one)
{
  tree size = fold_convert_loc (loc, sizetype, nb_iter);
  if (plus_one)
    size = size_binop (PLUS_EXPR, size, size_one_node);
  size = fold_build2_loc (loc, MULT_EXPR, sizetype, size,
			  TYPE_SIZE_UNIT (TREE_TYPE (DR_REF (dr))));
  size = fold_convert_loc (loc, size_type_node, size);
  return size;
}

/* Build an address argument for a memory operation call.  */

static tree
build_addr_arg_loc (location_t loc, data_reference_p dr, tree nb_bytes)
{
  tree addr_base;

  addr_base = size_binop_loc (loc, PLUS_EXPR, DR_OFFSET (dr), DR_INIT (dr));
  addr_base = fold_convert_loc (loc, sizetype, addr_base);

  /* Test for a negative stride, iterating over every element.  */
  if (tree_int_cst_sgn (DR_STEP (dr)) == -1)
    {
      addr_base = size_binop_loc (loc, MINUS_EXPR, addr_base,
				  fold_convert_loc (loc, sizetype, nb_bytes));
      addr_base = size_binop_loc (loc, PLUS_EXPR, addr_base,
				  TYPE_SIZE_UNIT (TREE_TYPE (DR_REF (dr))));
    }

  return fold_build_pointer_plus_loc (loc, DR_BASE_ADDRESS (dr), addr_base);
}

/* If VAL memory representation contains the same value in all bytes,
   return that value, otherwise return -1.
   E.g. for 0x24242424 return 0x24, for IEEE double
   747708026454360457216.0 return 0x44, etc.  */

static int
const_with_all_bytes_same (tree val)
{
  unsigned char buf[64];
  int i, len;

  if (integer_zerop (val)
      || (TREE_CODE (val) == CONSTRUCTOR
          && !TREE_CLOBBER_P (val)
          && CONSTRUCTOR_NELTS (val) == 0))
    return 0;

  if (real_zerop (val))
    {
      /* Only return 0 for +0.0, not for -0.0, which doesn't have
	 an all bytes same memory representation.  Don't transform
	 -0.0 stores into +0.0 even for !HONOR_SIGNED_ZEROS.  */
      switch (TREE_CODE (val))
	{
	case REAL_CST:
	  if (!real_isneg (TREE_REAL_CST_PTR (val)))
	    return 0;
	  break;
	case COMPLEX_CST:
	  if (!const_with_all_bytes_same (TREE_REALPART (val))
	      && !const_with_all_bytes_same (TREE_IMAGPART (val)))
	    return 0;
	  break;
	case VECTOR_CST:
	  unsigned int j;
	  for (j = 0; j < VECTOR_CST_NELTS (val); ++j)
	    if (const_with_all_bytes_same (VECTOR_CST_ELT (val, j)))
	      break;
	  if (j == VECTOR_CST_NELTS (val))
	    return 0;
	  break;
	default:
	  break;
	}
    }

  if (CHAR_BIT != 8 || BITS_PER_UNIT != 8)
    return -1;

  len = native_encode_expr (val, buf, sizeof (buf));
  if (len == 0)
    return -1;
  for (i = 1; i < len; i++)
    if (buf[i] != buf[0])
      return -1;
  return buf[0];
}

/* Generate a call to memset for PARTITION in LOOP.  */

static void
generate_memset_builtin (struct loop *loop, partition *partition)
{
  gimple_stmt_iterator gsi;
  gimple *stmt, *fn_call;
  tree mem, fn, nb_bytes;
  location_t loc;
  tree val;

  stmt = DR_STMT (partition->main_dr);
  loc = gimple_location (stmt);

  /* The new statements will be placed before LOOP.  */
  gsi = gsi_last_bb (loop_preheader_edge (loop)->src);

  nb_bytes = build_size_arg_loc (loc, partition->main_dr, partition->niter,
				 partition->plus_one);
  nb_bytes = force_gimple_operand_gsi (&gsi, nb_bytes, true, NULL_TREE,
				       false, GSI_CONTINUE_LINKING);
  mem = build_addr_arg_loc (loc, partition->main_dr, nb_bytes);
  mem = force_gimple_operand_gsi (&gsi, mem, true, NULL_TREE,
				  false, GSI_CONTINUE_LINKING);

  /* This exactly matches the pattern recognition in classify_partition.  */
  val = gimple_assign_rhs1 (stmt);
  /* Handle constants like 0x15151515 and similarly
     floating point constants etc. where all bytes are the same.  */
  int bytev = const_with_all_bytes_same (val);
  if (bytev != -1)
    val = build_int_cst (integer_type_node, bytev);
  else if (TREE_CODE (val) == INTEGER_CST)
    val = fold_convert (integer_type_node, val);
  else if (!useless_type_conversion_p (integer_type_node, TREE_TYPE (val)))
    {
      tree tem = make_ssa_name (integer_type_node);
      gimple *cstmt = gimple_build_assign (tem, NOP_EXPR, val);
      gsi_insert_after (&gsi, cstmt, GSI_CONTINUE_LINKING);
      val = tem;
    }

  fn = build_fold_addr_expr (builtin_decl_implicit (BUILT_IN_MEMSET));
  fn_call = gimple_build_call (fn, 3, mem, val, nb_bytes);
  gsi_insert_after (&gsi, fn_call, GSI_CONTINUE_LINKING);

  if (dump_file && (dump_flags & TDF_DETAILS))
    {
      fprintf (dump_file, "generated memset");
      if (bytev == 0)
	fprintf (dump_file, " zero\n");
      else
	fprintf (dump_file, "\n");
    }
}

/* Generate a call to memcpy for PARTITION in LOOP.  */

static void
generate_memcpy_builtin (struct loop *loop, partition *partition)
{
  gimple_stmt_iterator gsi;
  gimple *stmt, *fn_call;
  tree dest, src, fn, nb_bytes;
  location_t loc;
  enum built_in_function kind;

  stmt = DR_STMT (partition->main_dr);
  loc = gimple_location (stmt);

  /* The new statements will be placed before LOOP.  */
  gsi = gsi_last_bb (loop_preheader_edge (loop)->src);

  nb_bytes = build_size_arg_loc (loc, partition->main_dr, partition->niter,
				 partition->plus_one);
  nb_bytes = force_gimple_operand_gsi (&gsi, nb_bytes, true, NULL_TREE,
				       false, GSI_CONTINUE_LINKING);
  dest = build_addr_arg_loc (loc, partition->main_dr, nb_bytes);
  src = build_addr_arg_loc (loc, partition->secondary_dr, nb_bytes);
  if (partition->kind == PKIND_MEMCPY
      || ! ptr_derefs_may_alias_p (dest, src))
    kind = BUILT_IN_MEMCPY;
  else
    kind = BUILT_IN_MEMMOVE;

  dest = force_gimple_operand_gsi (&gsi, dest, true, NULL_TREE,
				   false, GSI_CONTINUE_LINKING);
  src = force_gimple_operand_gsi (&gsi, src, true, NULL_TREE,
				  false, GSI_CONTINUE_LINKING);
  fn = build_fold_addr_expr (builtin_decl_implicit (kind));
  fn_call = gimple_build_call (fn, 3, dest, src, nb_bytes);
  gsi_insert_after (&gsi, fn_call, GSI_CONTINUE_LINKING);

  if (dump_file && (dump_flags & TDF_DETAILS))
    {
      if (kind == BUILT_IN_MEMCPY)
	fprintf (dump_file, "generated memcpy\n");
      else
	fprintf (dump_file, "generated memmove\n");
    }
}

/* Remove and destroy the loop LOOP.  */

static void
destroy_loop (struct loop *loop)
{
  unsigned nbbs = loop->num_nodes;
  edge exit = single_exit (loop);
  basic_block src = loop_preheader_edge (loop)->src, dest = exit->dest;
  basic_block *bbs;
  unsigned i;

  bbs = get_loop_body_in_dom_order (loop);

  redirect_edge_pred (exit, src);
  exit->flags &= ~(EDGE_TRUE_VALUE|EDGE_FALSE_VALUE);
  exit->flags |= EDGE_FALLTHRU;
  cancel_loop_tree (loop);
  rescan_loop_exit (exit, false, true);

  i = nbbs;
  do
    {
      /* We have made sure to not leave any dangling uses of SSA
         names defined in the loop.  With the exception of virtuals.
	 Make sure we replace all uses of virtual defs that will remain
	 outside of the loop with the bare symbol as delete_basic_block
	 will release them.  */
      --i;
      for (gphi_iterator gsi = gsi_start_phis (bbs[i]); !gsi_end_p (gsi);
	   gsi_next (&gsi))
	{
	  gphi *phi = gsi.phi ();
	  if (virtual_operand_p (gimple_phi_result (phi)))
	    mark_virtual_phi_result_for_renaming (phi);
	}
      for (gimple_stmt_iterator gsi = gsi_start_bb (bbs[i]); !gsi_end_p (gsi);
	   gsi_next (&gsi))
	{
	  gimple *stmt = gsi_stmt (gsi);
	  tree vdef = gimple_vdef (stmt);
	  if (vdef && TREE_CODE (vdef) == SSA_NAME)
	    mark_virtual_operand_for_renaming (vdef);
	}
      delete_basic_block (bbs[i]);
    }
  while (i != 0);

  free (bbs);

  set_immediate_dominator (CDI_DOMINATORS, dest,
			   recompute_dominator (CDI_DOMINATORS, dest));
}

/* Generates code for PARTITION.  Return whether LOOP needs to be destroyed.  */

static bool 
generate_code_for_partition (struct loop *loop,
			     partition *partition, bool copy_p)
{
  switch (partition->kind)
    {
    case PKIND_NORMAL:
      /* Reductions all have to be in the last partition.  */
      gcc_assert (!partition_reduction_p (partition)
		  || !copy_p);
      generate_loops_for_partition (loop, partition, copy_p);
      return false;

    case PKIND_MEMSET:
      generate_memset_builtin (loop, partition);
      break;

    case PKIND_MEMCPY:
    case PKIND_MEMMOVE:
      generate_memcpy_builtin (loop, partition);
      break;

    default:
      gcc_unreachable ();
    }

  /* Common tail for partitions we turn into a call.  If this was the last
     partition for which we generate code, we have to destroy the loop.  */
  if (!copy_p)
    return true;
  return false;
}

/* Return data dependence relation for data references A and B.  The two
   data references must be in lexicographic order wrto reduced dependence
   graph RDG.  We firstly try to find ddr from global ddr hash table.  If
   it doesn't exist, compute the ddr and cache it.  */

static data_dependence_relation *
get_data_dependence (struct graph *rdg, data_reference_p a, data_reference_p b)
{
  struct data_dependence_relation ent, **slot;
  struct data_dependence_relation *ddr;

  gcc_assert (DR_IS_WRITE (a) || DR_IS_WRITE (b));
  gcc_assert (rdg_vertex_for_stmt (rdg, DR_STMT (a))
	      <= rdg_vertex_for_stmt (rdg, DR_STMT (b)));
  ent.a = a;
  ent.b = b;
  slot = ddrs_table.find_slot (&ent, INSERT);
  if (*slot == NULL)
    {
      ddr = initialize_data_dependence_relation (a, b, loop_nest);
      compute_affine_dependence (ddr, loop_nest[0]);
      *slot = ddr;
    }

  return *slot;
}

/* In reduced dependence graph RDG for loop distribution, return true if
   dependence between references DR1 and DR2 leads to a dependence cycle
   and such dependence cycle can't be resolved by runtime alias check.  */

static bool
data_dep_in_cycle_p (struct graph *rdg,
		     data_reference_p dr1, data_reference_p dr2)
{
  struct data_dependence_relation *ddr;

  /* Re-shuffle data-refs to be in topological order.  */
  if (rdg_vertex_for_stmt (rdg, DR_STMT (dr1))
      > rdg_vertex_for_stmt (rdg, DR_STMT (dr2)))
    std::swap (dr1, dr2);

  ddr = get_data_dependence (rdg, dr1, dr2);

  /* In case of no data dependence.  */
  if (DDR_ARE_DEPENDENT (ddr) == chrec_known)
    return false;
  /* For unknown data dependence or known data dependence which can't be
     expressed in classic distance vector, we check if it can be resolved
     by runtime alias check.  If yes, we still consider data dependence
     as won't introduce data dependence cycle.  */
  else if (DDR_ARE_DEPENDENT (ddr) == chrec_dont_know
	   || DDR_NUM_DIST_VECTS (ddr) == 0)
    return !runtime_alias_check_p (ddr, NULL, true);
  else if (DDR_NUM_DIST_VECTS (ddr) > 1)
    return true;
  else if (DDR_REVERSED_P (ddr)
	   || lambda_vector_zerop (DDR_DIST_VECT (ddr, 0), 1))
    return false;

  return true;
}

/* Given reduced dependence graph RDG, PARTITION1 and PARTITION2, update
   PARTITION1's type after merging PARTITION2 into PARTITION1.  */

static void
update_type_for_merge (struct graph *rdg,
		       partition *partition1, partition *partition2)
{
  unsigned i, j;
  bitmap_iterator bi, bj;
  data_reference_p dr1, dr2;

  EXECUTE_IF_SET_IN_BITMAP (partition1->datarefs, 0, i, bi)
    {
      unsigned start = (partition1 == partition2) ? i + 1 : 0;

      dr1 = datarefs_vec[i];
      EXECUTE_IF_SET_IN_BITMAP (partition2->datarefs, start, j, bj)
	{
	  dr2 = datarefs_vec[j];
	  if (DR_IS_READ (dr1) && DR_IS_READ (dr2))
	    continue;

	  /* Partition can only be executed sequentially if there is any
	     data dependence cycle.  */
	  if (data_dep_in_cycle_p (rdg, dr1, dr2))
	    {
	      partition1->type = PTYPE_SEQUENTIAL;
	      return;
	    }
	}
    }
}

/* Returns a partition with all the statements needed for computing
   the vertex V of the RDG, also including the loop exit conditions.  */

static partition *
build_rdg_partition_for_vertex (struct graph *rdg, int v)
{
  partition *partition = partition_alloc ();
  auto_vec<int, 3> nodes;
  unsigned i, j;
  int x;
  data_reference_p dr;

  graphds_dfs (rdg, &v, 1, &nodes, false, NULL);

  FOR_EACH_VEC_ELT (nodes, i, x)
    {
      bitmap_set_bit (partition->stmts, x);
      bitmap_set_bit (partition->loops,
		      loop_containing_stmt (RDG_STMT (rdg, x))->num);

      for (j = 0; RDG_DATAREFS (rdg, x).iterate (j, &dr); ++j)
	{
	  unsigned idx = (unsigned) DR_INDEX (dr);
	  gcc_assert (idx < datarefs_vec.length ());

	  /* Partition can only be executed sequentially if there is any
	     unknown data reference.  */
	  if (!DR_BASE_ADDRESS (dr) || !DR_OFFSET (dr)
	      || !DR_INIT (dr) || !DR_STEP (dr))
	    partition->type = PTYPE_SEQUENTIAL;

	  bitmap_set_bit (partition->datarefs, idx);
	}
    }

  if (partition->type == PTYPE_SEQUENTIAL)
    return partition;

  /* Further check if any data dependence prevents us from executing the
     partition parallelly.  */
  update_type_for_merge (rdg, partition, partition);

  return partition;
}

/* Classifies the builtin kind we can generate for PARTITION of RDG and LOOP.
   For the moment we detect memset, memcpy and memmove patterns.  Bitmap
   STMT_IN_ALL_PARTITIONS contains statements belonging to all partitions.  */

static void
classify_partition (loop_p loop, struct graph *rdg, partition *partition,
		    bitmap stmt_in_all_partitions)
{
  bitmap_iterator bi;
  unsigned i;
  tree nb_iter;
  data_reference_p single_load, single_store;
  bool volatiles_p = false, plus_one = false, has_reduction = false;

  partition->kind = PKIND_NORMAL;
  partition->main_dr = NULL;
  partition->secondary_dr = NULL;
  partition->niter = NULL_TREE;
  partition->plus_one = false;

  EXECUTE_IF_SET_IN_BITMAP (partition->stmts, 0, i, bi)
    {
      gimple *stmt = RDG_STMT (rdg, i);

      if (gimple_has_volatile_ops (stmt))
	volatiles_p = true;

      /* If the stmt is not included by all partitions and there is uses
	 outside of the loop, then mark the partition as reduction.  */
      if (stmt_has_scalar_dependences_outside_loop (loop, stmt))
	{
	  /* Due to limitation in the transform phase we have to fuse all
	     reduction partitions.  As a result, this could cancel valid
	     loop distribution especially for loop that induction variable
	     is used outside of loop.  To workaround this issue, we skip
	     marking partition as reudction if the reduction stmt belongs
	     to all partitions.  In such case, reduction will be computed
	     correctly no matter how partitions are fused/distributed.  */
	  if (!bitmap_bit_p (stmt_in_all_partitions, i))
	    {
	      partition->reduction_p = true;
	      return;
	    }
	  has_reduction = true;
	}
    }

  /* Perform general partition disqualification for builtins.  */
  if (volatiles_p
      /* Simple workaround to prevent classifying the partition as builtin
	 if it contains any use outside of loop.  */
      || has_reduction
      || !flag_tree_loop_distribute_patterns)
    return;

  /* Detect memset and memcpy.  */
  single_load = NULL;
  single_store = NULL;
  EXECUTE_IF_SET_IN_BITMAP (partition->stmts, 0, i, bi)
    {
      gimple *stmt = RDG_STMT (rdg, i);
      data_reference_p dr;
      unsigned j;

      if (gimple_code (stmt) == GIMPLE_PHI)
	continue;

      /* Any scalar stmts are ok.  */
      if (!gimple_vuse (stmt))
	continue;

      /* Otherwise just regular loads/stores.  */
      if (!gimple_assign_single_p (stmt))
	return;

      /* But exactly one store and/or load.  */
      for (j = 0; RDG_DATAREFS (rdg, i).iterate (j, &dr); ++j)
	{
	  tree type = TREE_TYPE (DR_REF (dr));

	  /* The memset, memcpy and memmove library calls are only
	     able to deal with generic address space.  */
	  if (!ADDR_SPACE_GENERIC_P (TYPE_ADDR_SPACE (type)))
	    return;

	  if (DR_IS_READ (dr))
	    {
	      if (single_load != NULL)
		return;
	      single_load = dr;
	    }
	  else
	    {
	      if (single_store != NULL)
		return;
	      single_store = dr;
	    }
	}
    }

  if (!single_store)
    return;

  nb_iter = number_of_latch_executions (loop);
  if (!nb_iter || nb_iter == chrec_dont_know)
    return;
  if (dominated_by_p (CDI_DOMINATORS, single_exit (loop)->src,
		      gimple_bb (DR_STMT (single_store))))
    plus_one = true;

  if (single_store && !single_load)
    {
      gimple *stmt = DR_STMT (single_store);
      tree rhs = gimple_assign_rhs1 (stmt);
      if (const_with_all_bytes_same (rhs) == -1
	  && (!INTEGRAL_TYPE_P (TREE_TYPE (rhs))
	      || (TYPE_MODE (TREE_TYPE (rhs))
		  != TYPE_MODE (unsigned_char_type_node))))
	return;
      if (TREE_CODE (rhs) == SSA_NAME
	  && !SSA_NAME_IS_DEFAULT_DEF (rhs)
	  && flow_bb_inside_loop_p (loop, gimple_bb (SSA_NAME_DEF_STMT (rhs))))
	return;
      if (!adjacent_dr_p (single_store)
	  || !dominated_by_p (CDI_DOMINATORS,
			      loop->latch, gimple_bb (stmt)))
	return;
      partition->kind = PKIND_MEMSET;
      partition->main_dr = single_store;
      partition->niter = nb_iter;
      partition->plus_one = plus_one;
    }
  else if (single_store && single_load)
    {
      gimple *store = DR_STMT (single_store);
      gimple *load = DR_STMT (single_load);
      /* Direct aggregate copy or via an SSA name temporary.  */
      if (load != store
	  && gimple_assign_lhs (load) != gimple_assign_rhs1 (store))
	return;
      if (!adjacent_dr_p (single_store)
	  || !adjacent_dr_p (single_load)
	  || !operand_equal_p (DR_STEP (single_store),
			       DR_STEP (single_load), 0)
	  || !dominated_by_p (CDI_DOMINATORS,
			      loop->latch, gimple_bb (store)))
	return;
      /* Now check that if there is a dependence this dependence is
         of a suitable form for memmove.  */
      ddr_p ddr = get_data_dependence (rdg, single_load, single_store);
      if (DDR_ARE_DEPENDENT (ddr) == chrec_dont_know)
	return;

      if (DDR_ARE_DEPENDENT (ddr) != chrec_known)
	{
	  if (DDR_NUM_DIST_VECTS (ddr) == 0)
	    return;

	  lambda_vector dist_v;
	  FOR_EACH_VEC_ELT (DDR_DIST_VECTS (ddr), i, dist_v)
	    {
	      int dist = dist_v[index_in_loop_nest (loop->num,
						    DDR_LOOP_NEST (ddr))];
	      if (dist > 0 && !DDR_REVERSED_P (ddr))
		return;
	    }
	  partition->kind = PKIND_MEMMOVE;
	}
      else
	partition->kind = PKIND_MEMCPY;
      partition->main_dr = single_store;
      partition->secondary_dr = single_load;
      partition->niter = nb_iter;
      partition->plus_one = plus_one;
    }
}

/* Returns true when PARTITION1 and PARTITION2 access the same memory
   object in RDG.  */

static bool
share_memory_accesses (struct graph *rdg,
		       partition *partition1, partition *partition2)
{
  unsigned i, j;
  bitmap_iterator bi, bj;
  data_reference_p dr1, dr2;

  /* First check whether in the intersection of the two partitions are
     any loads or stores.  Common loads are the situation that happens
     most often.  */
  EXECUTE_IF_AND_IN_BITMAP (partition1->stmts, partition2->stmts, 0, i, bi)
    if (RDG_MEM_WRITE_STMT (rdg, i)
	|| RDG_MEM_READS_STMT (rdg, i))
      return true;

  /* Then check whether the two partitions access the same memory object.  */
  EXECUTE_IF_SET_IN_BITMAP (partition1->datarefs, 0, i, bi)
    {
      dr1 = datarefs_vec[i];

      if (!DR_BASE_ADDRESS (dr1)
	  || !DR_OFFSET (dr1) || !DR_INIT (dr1) || !DR_STEP (dr1))
	continue;

      EXECUTE_IF_SET_IN_BITMAP (partition2->datarefs, 0, j, bj)
	{
	  dr2 = datarefs_vec[j];

	  if (!DR_BASE_ADDRESS (dr2)
	      || !DR_OFFSET (dr2) || !DR_INIT (dr2) || !DR_STEP (dr2))
	    continue;

	  if (operand_equal_p (DR_BASE_ADDRESS (dr1), DR_BASE_ADDRESS (dr2), 0)
	      && operand_equal_p (DR_OFFSET (dr1), DR_OFFSET (dr2), 0)
	      && operand_equal_p (DR_INIT (dr1), DR_INIT (dr2), 0)
	      && operand_equal_p (DR_STEP (dr1), DR_STEP (dr2), 0))
	    return true;
	}
    }

  return false;
}

/* For each seed statement in STARTING_STMTS, this function builds
   partition for it by adding depended statements according to RDG.
   All partitions are recorded in PARTITIONS.  */

static void
rdg_build_partitions (struct graph *rdg,
		      vec<gimple *> starting_stmts,
		      vec<partition *> *partitions)
{
  auto_bitmap processed;
  int i;
  gimple *stmt;

  FOR_EACH_VEC_ELT (starting_stmts, i, stmt)
    {
      int v = rdg_vertex_for_stmt (rdg, stmt);

      if (dump_file && (dump_flags & TDF_DETAILS))
	fprintf (dump_file,
		 "ldist asked to generate code for vertex %d\n", v);

      /* If the vertex is already contained in another partition so
         is the partition rooted at it.  */
      if (bitmap_bit_p (processed, v))
	continue;

      partition *partition = build_rdg_partition_for_vertex (rdg, v);
      bitmap_ior_into (processed, partition->stmts);

      if (dump_file && (dump_flags & TDF_DETAILS))
	{
	  fprintf (dump_file, "ldist creates useful %s partition:\n",
		   partition->type == PTYPE_PARALLEL ? "parallel" : "sequent");
	  bitmap_print (dump_file, partition->stmts, "  ", "\n");
	}

      partitions->safe_push (partition);
    }

  /* All vertices should have been assigned to at least one partition now,
     other than vertices belonging to dead code.  */
}

/* Dump to FILE the PARTITIONS.  */

static void
dump_rdg_partitions (FILE *file, vec<partition *> partitions)
{
  int i;
  partition *partition;

  FOR_EACH_VEC_ELT (partitions, i, partition)
    debug_bitmap_file (file, partition->stmts);
}

/* Debug PARTITIONS.  */
extern void debug_rdg_partitions (vec<partition *> );

DEBUG_FUNCTION void
debug_rdg_partitions (vec<partition *> partitions)
{
  dump_rdg_partitions (stderr, partitions);
}

/* Returns the number of read and write operations in the RDG.  */

static int
number_of_rw_in_rdg (struct graph *rdg)
{
  int i, res = 0;

  for (i = 0; i < rdg->n_vertices; i++)
    {
      if (RDG_MEM_WRITE_STMT (rdg, i))
	++res;

      if (RDG_MEM_READS_STMT (rdg, i))
	++res;
    }

  return res;
}

/* Returns the number of read and write operations in a PARTITION of
   the RDG.  */

static int
number_of_rw_in_partition (struct graph *rdg, partition *partition)
{
  int res = 0;
  unsigned i;
  bitmap_iterator ii;

  EXECUTE_IF_SET_IN_BITMAP (partition->stmts, 0, i, ii)
    {
      if (RDG_MEM_WRITE_STMT (rdg, i))
	++res;

      if (RDG_MEM_READS_STMT (rdg, i))
	++res;
    }

  return res;
}

/* Returns true when one of the PARTITIONS contains all the read or
   write operations of RDG.  */

static bool
partition_contains_all_rw (struct graph *rdg,
			   vec<partition *> partitions)
{
  int i;
  partition *partition;
  int nrw = number_of_rw_in_rdg (rdg);

  FOR_EACH_VEC_ELT (partitions, i, partition)
    if (nrw == number_of_rw_in_partition (rdg, partition))
      return true;

  return false;
}

/* Compute partition dependence created by the data references in DRS1
   and DRS2 and modify and return DIR according to that.  */

static int
pg_add_dependence_edges (struct graph *rdg, int dir,
			 bitmap drs1, bitmap drs2)
{
  unsigned i, j;
  bitmap_iterator bi, bj;
  data_reference_p dr1, dr2, saved_dr1;

  /* dependence direction - 0 is no dependence, -1 is back,
     1 is forth, 2 is both (we can stop then, merging will occur).  */
  EXECUTE_IF_SET_IN_BITMAP (drs1, 0, i, bi)
    {
      dr1 = datarefs_vec[i];

      EXECUTE_IF_SET_IN_BITMAP (drs2, 0, j, bj)
	{
	  dr2 = datarefs_vec[j];

	  /* Skip all <read, read> data dependence.  */
	  if (DR_IS_READ (dr1) && DR_IS_READ (dr2))
	    continue;

	  saved_dr1 = dr1;
	  int this_dir = 1;
	  ddr_p ddr;
	  /* Re-shuffle data-refs to be in dominator order.  */
	  if (rdg_vertex_for_stmt (rdg, DR_STMT (dr1))
	      > rdg_vertex_for_stmt (rdg, DR_STMT (dr2)))
	    {
	      std::swap (dr1, dr2);
	      this_dir = -this_dir;
	    }
	  ddr = get_data_dependence (rdg, dr1, dr2);
	  if (DDR_ARE_DEPENDENT (ddr) == chrec_dont_know)
	    this_dir = 2;
	  else if (DDR_ARE_DEPENDENT (ddr) == NULL_TREE)
	    {
	      if (DDR_REVERSED_P (ddr))
		{
		  std::swap (dr1, dr2);
		  this_dir = -this_dir;
		}
	      /* Known dependences can still be unordered througout the
		 iteration space, see gcc.dg/tree-ssa/ldist-16.c.  */
	      if (DDR_NUM_DIST_VECTS (ddr) != 1)
		this_dir = 2;
	      /* If the overlap is exact preserve stmt order.  */
	      else if (lambda_vector_zerop (DDR_DIST_VECT (ddr, 0), 1))
		;
	      else
		{
		  /* Else as the distance vector is lexicographic positive
		     swap the dependence direction.  */
		  this_dir = -this_dir;
		}
	    }
	  else
	    this_dir = 0;
	  if (this_dir == 2)
	    return 2;
	  else if (dir == 0)
	    dir = this_dir;
	  else if (this_dir != 0 && dir != this_dir)
	    return 2;
	  /* Shuffle "back" dr1.  */
	  dr1 = saved_dr1;
	}
    }
  return dir;
}

/* Compare postorder number of the partition graph vertices V1 and V2.  */

static int
pgcmp (const void *v1_, const void *v2_)
{
  const vertex *v1 = (const vertex *)v1_;
  const vertex *v2 = (const vertex *)v2_;
  return v2->post - v1->post;
}

/* Distributes the code from LOOP in such a way that producer
   statements are placed before consumer statements.  Tries to separate
   only the statements from STMTS into separate loops.
   Returns the number of distributed loops.  Set *DESTROY_P to whether
   LOOP needs to be destroyed.  */

static int
distribute_loop (struct loop *loop, vec<gimple *> stmts,
		 control_dependences *cd, int *nb_calls, bool *destroy_p)
{
  struct graph *rdg;
  partition *partition;
  bool any_builtin;
  int i, nbp;
  graph *pg = NULL;
  int num_sccs = 1;

  *destroy_p = false;
  *nb_calls = 0;
  loop_nest.create (0);
  if (!find_loop_nest (loop, &loop_nest))
    {
      loop_nest.release ();
      return 0;
    }

  datarefs_vec.create (20);
  rdg = build_rdg (loop, cd);
  if (!rdg)
    {
      if (dump_file && (dump_flags & TDF_DETAILS))
	fprintf (dump_file,
		 "Loop %d not distributed: failed to build the RDG.\n",
		 loop->num);

      loop_nest.release ();
      free_data_refs (datarefs_vec);
      return 0;
    }

  if (datarefs_vec.length () > MAX_DATAREFS_NUM)
    {
      if (dump_file && (dump_flags & TDF_DETAILS))
	fprintf (dump_file,
		 "Loop %d not distributed: too many memory references.\n",
		 loop->num);

      free_rdg (rdg);
      loop_nest.release ();
      free_data_refs (datarefs_vec);
      return 0;
    }

  data_reference_p dref;
  for (i = 0; datarefs_vec.iterate (i, &dref); ++i)
    dref->aux = (void *) (uintptr_t) i;

  if (dump_file && (dump_flags & TDF_DETAILS))
    dump_rdg (dump_file, rdg);

  auto_vec<struct partition *, 3> partitions;
  rdg_build_partitions (rdg, stmts, &partitions);

  auto_bitmap stmt_in_all_partitions;
  bitmap_copy (stmt_in_all_partitions, partitions[0]->stmts);
  for (i = 1; partitions.iterate (i, &partition); ++i)
    bitmap_and_into (stmt_in_all_partitions, partitions[i]->stmts);

  any_builtin = false;
  FOR_EACH_VEC_ELT (partitions, i, partition)
    {
      classify_partition (loop, rdg, partition, stmt_in_all_partitions);
      any_builtin |= partition_builtin_p (partition);
    }

  /* If we are only distributing patterns but did not detect any,
     simply bail out.  */
  if (!flag_tree_loop_distribution
      && !any_builtin)
    {
      nbp = 0;
      goto ldist_done;
    }

  /* If we are only distributing patterns fuse all partitions that
     were not classified as builtins.  This also avoids chopping
     a loop into pieces, separated by builtin calls.  That is, we
     only want no or a single loop body remaining.  */
  struct partition *into;
  if (!flag_tree_loop_distribution)
    {
      for (i = 0; partitions.iterate (i, &into); ++i)
	if (!partition_builtin_p (into))
	  break;
      for (++i; partitions.iterate (i, &partition); ++i)
	if (!partition_builtin_p (partition))
	  {
	    partition_merge_into (NULL, into, partition, FUSE_NON_BUILTIN);
	    partitions.unordered_remove (i);
	    partition_free (partition);
	    i--;
	  }
    }

  /* Due to limitations in the transform phase we have to fuse all
     reduction partitions into the last partition so the existing
     loop will contain all loop-closed PHI nodes.  */
  for (i = 0; partitions.iterate (i, &into); ++i)
    if (partition_reduction_p (into))
      break;
  for (i = i + 1; partitions.iterate (i, &partition); ++i)
    if (partition_reduction_p (partition))
      {
	partition_merge_into (rdg, into, partition, FUSE_REDUCTION);
	partitions.unordered_remove (i);
	partition_free (partition);
	i--;
      }

  /* Apply our simple cost model - fuse partitions with similar
     memory accesses.  */
  for (i = 0; partitions.iterate (i, &into); ++i)
    {
      bool changed = false;
      if (partition_builtin_p (into))
	continue;
      for (int j = i + 1;
	   partitions.iterate (j, &partition); ++j)
	{
	  if (share_memory_accesses (rdg, into, partition))
	    {
	      partition_merge_into (rdg, into, partition, FUSE_SHARE_REF);
	      partitions.unordered_remove (j);
	      partition_free (partition);
	      j--;
	      changed = true;
	    }
	}
      /* If we fused 0 1 2 in step 1 to 0,2 1 as 0 and 2 have similar
         accesses when 1 and 2 have similar accesses but not 0 and 1
	 then in the next iteration we will fail to consider merging
	 1 into 0,2.  So try again if we did any merging into 0.  */
      if (changed)
	i--;
    }

  /* Build the partition dependency graph.  */
  if (partitions.length () > 1)
    {
      pg = new_graph (partitions.length ());
      struct pgdata {
	  struct partition *partition;
      };
#define PGDATA(i) ((pgdata *)(pg->vertices[i].data))
      for (i = 0; partitions.iterate (i, &partition); ++i)
	{
	  vertex *v = &pg->vertices[i];
	  pgdata *data = new pgdata;
	  /* FIXME - leaks.  */
	  v->data = data;
	  data->partition = partition;
	}
      struct partition *partition1, *partition2;
      for (i = 0; partitions.iterate (i, &partition1); ++i)
	for (int j = i + 1; partitions.iterate (j, &partition2); ++j)
	  {
	    /* dependence direction - 0 is no dependence, -1 is back,
	       1 is forth, 2 is both (we can stop then, merging will occur).  */
	    int dir = pg_add_dependence_edges (rdg, 0,
					       partition1->datarefs,
					       partition2->datarefs);
	    if (dir == 1 || dir == 2)
	      add_edge (pg, i, j);
	    if (dir == -1 || dir == 2)
	      add_edge (pg, j, i);
	  }

      /* Add edges to the reduction partition (if any) to force it last.  */
      unsigned j;
      for (j = 0; partitions.iterate (j, &partition); ++j)
	if (partition_reduction_p (partition))
	  break;
      if (j < partitions.length ())
	{
	  for (unsigned i = 0; partitions.iterate (i, &partition); ++i)
	    if (i != j)
	      add_edge (pg, i, j);
	}

      /* Compute partitions we cannot separate and fuse them.  */
      num_sccs = graphds_scc (pg, NULL);
      for (i = 0; i < num_sccs; ++i)
	{
	  struct partition *first;
	  int j;
	  for (j = 0; partitions.iterate (j, &first); ++j)
	    if (pg->vertices[j].component == i)
	      break;
	  for (j = j + 1; partitions.iterate (j, &partition); ++j)
	    if (pg->vertices[j].component == i)
	      {
		partition_merge_into (NULL, first,
				      partition, FUSE_SAME_SCC);
		first->type = PTYPE_SEQUENTIAL;
		partitions[j] = NULL;
		partition_free (partition);
		PGDATA (j)->partition = NULL;
	      }
	}

      /* Now order the remaining nodes in postorder.  */
      qsort (pg->vertices, pg->n_vertices, sizeof (vertex), pgcmp);
      partitions.truncate (0);
      for (i = 0; i < pg->n_vertices; ++i)
	{
	  pgdata *data = PGDATA (i);
	  if (data->partition)
	    partitions.safe_push (data->partition);
	  delete data;
	}
      gcc_assert (partitions.length () == (unsigned)num_sccs);
      free_graph (pg);
    }

  nbp = partitions.length ();
  if (nbp == 0
      || (nbp == 1 && !partition_builtin_p (partitions[0]))
      || (nbp > 1 && partition_contains_all_rw (rdg, partitions)))
    {
      nbp = 0;
      goto ldist_done;
    }

  if (dump_file && (dump_flags & TDF_DETAILS))
    dump_rdg_partitions (dump_file, partitions);

  FOR_EACH_VEC_ELT (partitions, i, partition)
    {
      if (partition_builtin_p (partition))
	(*nb_calls)++;
      *destroy_p |= generate_code_for_partition (loop, partition, i < nbp - 1);
    }

 ldist_done:
  loop_nest.release ();
  free_data_refs (datarefs_vec);
  for (hash_table<ddr_hasher>::iterator iter = ddrs_table.begin ();
       iter != ddrs_table.end (); ++iter)
    {
      free_dependence_relation (*iter);
      *iter = NULL;
    }
  ddrs_table.empty ();

  FOR_EACH_VEC_ELT (partitions, i, partition)
    partition_free (partition);

  free_rdg (rdg);
  return nbp - *nb_calls;
}

/* Distribute all loops in the current function.  */

namespace {

const pass_data pass_data_loop_distribution =
{
  GIMPLE_PASS, /* type */
  "ldist", /* name */
  OPTGROUP_LOOP, /* optinfo_flags */
  TV_TREE_LOOP_DISTRIBUTION, /* tv_id */
  ( PROP_cfg | PROP_ssa ), /* properties_required */
  0, /* properties_provided */
  0, /* properties_destroyed */
  0, /* todo_flags_start */
  0, /* todo_flags_finish */
};

class pass_loop_distribution : public gimple_opt_pass
{
public:
  pass_loop_distribution (gcc::context *ctxt)
    : gimple_opt_pass (pass_data_loop_distribution, ctxt)
  {}

  /* opt_pass methods: */
  virtual bool gate (function *)
    {
      return flag_tree_loop_distribution
	|| flag_tree_loop_distribute_patterns;
    }

  virtual unsigned int execute (function *);

}; // class pass_loop_distribution

unsigned int
pass_loop_distribution::execute (function *fun)
{
  struct loop *loop;
  bool changed = false;
  basic_block bb;
  control_dependences *cd = NULL;
  auto_vec<loop_p> loops_to_be_destroyed;

  if (number_of_loops (fun) <= 1)
    return 0;

  /* Compute topological order for basic blocks.  Topological order is
     needed because data dependence is computed for data references in
     lexicographical order.  */
  if (bb_top_order_index == NULL)
    {
      int *rpo = XNEWVEC (int, last_basic_block_for_fn (cfun));

      bb_top_order_index = XNEWVEC (int, last_basic_block_for_fn (cfun));
      bb_top_order_index_size
	= pre_and_rev_post_order_compute_fn (cfun, NULL, rpo, true);
      for (int i = 0; i < bb_top_order_index_size; i++)
	bb_top_order_index[rpo[i]] = i;

      free (rpo);
    }

  FOR_ALL_BB_FN (bb, fun)
    {
      gimple_stmt_iterator gsi;
      for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
	gimple_set_uid (gsi_stmt (gsi), -1);
      for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
	gimple_set_uid (gsi_stmt (gsi), -1);
    }

  /* We can at the moment only distribute non-nested loops, thus restrict
     walking to innermost loops.  */
  FOR_EACH_LOOP (loop, LI_ONLY_INNERMOST)
    {
      auto_vec<gimple *> work_list;
      basic_block *bbs;
      int num = loop->num;
      unsigned int i;

      /* If the loop doesn't have a single exit we will fail anyway,
	 so do that early.  */
      if (!single_exit (loop))
	continue;

      /* Only optimize hot loops.  */
      if (!optimize_loop_for_speed_p (loop))
	continue;

      /* Initialize the worklist with stmts we seed the partitions with.  */
      bbs = get_loop_body_in_dom_order (loop);
      for (i = 0; i < loop->num_nodes; ++i)
	{
	  for (gphi_iterator gsi = gsi_start_phis (bbs[i]);
	       !gsi_end_p (gsi);
	       gsi_next (&gsi))
	    {
	      gphi *phi = gsi.phi ();
	      if (virtual_operand_p (gimple_phi_result (phi)))
		continue;
	      /* Distribute stmts which have defs that are used outside of
		 the loop.  */
	      if (!stmt_has_scalar_dependences_outside_loop (loop, phi))
		continue;
	      work_list.safe_push (phi);
	    }
	  for (gimple_stmt_iterator gsi = gsi_start_bb (bbs[i]);
	       !gsi_end_p (gsi);
	       gsi_next (&gsi))
	    {
	      gimple *stmt = gsi_stmt (gsi);

	      /* If there is a stmt with side-effects bail out - we
		 cannot and should not distribute this loop.  */
	      if (gimple_has_side_effects (stmt))
		{
		  work_list.truncate (0);
		  goto out;
		}

	      /* Distribute stmts which have defs that are used outside of
		 the loop.  */
	      if (stmt_has_scalar_dependences_outside_loop (loop, stmt))
		;
	      /* Otherwise only distribute stores for now.  */
	      else if (!gimple_vdef (stmt))
		continue;

	      work_list.safe_push (stmt);
	    }
	}
out:
      free (bbs);

      int nb_generated_loops = 0;
      int nb_generated_calls = 0;
      location_t loc = find_loop_location (loop);
      if (work_list.length () > 0)
	{
	  if (!cd)
	    {
	      calculate_dominance_info (CDI_DOMINATORS);
	      calculate_dominance_info (CDI_POST_DOMINATORS);
	      cd = new control_dependences ();
	      free_dominance_info (CDI_POST_DOMINATORS);
	    }
	  bool destroy_p;
	  nb_generated_loops = distribute_loop (loop, work_list, cd,
						&nb_generated_calls,
						&destroy_p);
	  if (destroy_p)
	    loops_to_be_destroyed.safe_push (loop);
	}

      if (nb_generated_loops + nb_generated_calls > 0)
	{
	  changed = true;
	  dump_printf_loc (MSG_OPTIMIZED_LOCATIONS,
			   loc, "Loop %d distributed: split to %d loops "
			   "and %d library calls.\n",
			   num, nb_generated_loops, nb_generated_calls);
	}
      else if (dump_file && (dump_flags & TDF_DETAILS))
	fprintf (dump_file, "Loop %d is the same.\n", num);
    }

  if (cd)
    delete cd;

  if (bb_top_order_index != NULL)
    {
      free (bb_top_order_index);
      bb_top_order_index = NULL;
      bb_top_order_index_size = 0;
    }

  if (changed)
    {
      /* Destroy loop bodies that could not be reused.  Do this late as we
	 otherwise can end up refering to stale data in control dependences.  */
      unsigned i;
      FOR_EACH_VEC_ELT (loops_to_be_destroyed, i, loop)
	destroy_loop (loop);

      /* Cached scalar evolutions now may refer to wrong or non-existing
	 loops.  */
      scev_reset_htab ();
      mark_virtual_operands_for_renaming (fun);
      rewrite_into_loop_closed_ssa (NULL, TODO_update_ssa);
    }

  checking_verify_loop_structure ();

  return 0;
}

} // anon namespace

gimple_opt_pass *
make_pass_loop_distribution (gcc::context *ctxt)
{
  return new pass_loop_distribution (ctxt);
}