2015-12-01 Richard Biener <rguenther@suse.de>

[official-gcc.git] / gcc / tree-vect-data-refs.c

/* Data References Analysis and Manipulation Utilities for Vectorization.
   Copyright (C) 2003-2015 Free Software Foundation, Inc.
   Contributed by Dorit Naishlos <dorit@il.ibm.com>
   and Ira Rosen <irar@il.ibm.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/>.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "backend.h"
#include "target.h"
#include "rtl.h"
#include "tree.h"
#include "gimple.h"
#include "predict.h"
#include "tm_p.h"
#include "ssa.h"
#include "optabs-tree.h"
#include "cgraph.h"
#include "dumpfile.h"
#include "alias.h"
#include "fold-const.h"
#include "stor-layout.h"
#include "tree-eh.h"
#include "gimplify.h"
#include "gimple-iterator.h"
#include "gimplify-me.h"
#include "tree-ssa-loop-ivopts.h"
#include "tree-ssa-loop-manip.h"
#include "tree-ssa-loop.h"
#include "cfgloop.h"
#include "tree-scalar-evolution.h"
#include "tree-vectorizer.h"
#include "expr.h"
#include "builtins.h"
#include "params.h"

/* Return true if load- or store-lanes optab OPTAB is implemented for
   COUNT vectors of type VECTYPE.  NAME is the name of OPTAB.  */

static bool
vect_lanes_optab_supported_p (const char *name, convert_optab optab,
                              tree vectype, unsigned HOST_WIDE_INT count)
{
  machine_mode mode, array_mode;
  bool limit_p;

  mode = TYPE_MODE (vectype);
  limit_p = !targetm.array_mode_supported_p (mode, count);
  array_mode = mode_for_size (count * GET_MODE_BITSIZE (mode),
                              MODE_INT, limit_p);

  if (array_mode == BLKmode)
    {
      if (dump_enabled_p ())
        dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                         "no array mode for %s[" HOST_WIDE_INT_PRINT_DEC "]\n",
                         GET_MODE_NAME (mode), count);
      return false;
    }

  if (convert_optab_handler (optab, array_mode, mode) == CODE_FOR_nothing)
    {
      if (dump_enabled_p ())
        dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                         "cannot use %s<%s><%s>\n", name,
                         GET_MODE_NAME (array_mode), GET_MODE_NAME (mode));
      return false;
    }

  if (dump_enabled_p ())
    dump_printf_loc (MSG_NOTE, vect_location,
                     "can use %s<%s><%s>\n", name, GET_MODE_NAME (array_mode),
                     GET_MODE_NAME (mode));

  return true;
}


/* Return the smallest scalar part of STMT.
   This is used to determine the vectype of the stmt.  We generally set the
   vectype according to the type of the result (lhs).  For stmts whose
   result-type is different than the type of the arguments (e.g., demotion,
   promotion), vectype will be reset appropriately (later).  Note that we have
   to visit the smallest datatype in this function, because that determines the
   VF.  If the smallest datatype in the loop is present only as the rhs of a
   promotion operation - we'd miss it.
   Such a case, where a variable of this datatype does not appear in the lhs
   anywhere in the loop, can only occur if it's an invariant: e.g.:
   'int_x = (int) short_inv', which we'd expect to have been optimized away by
   invariant motion.  However, we cannot rely on invariant motion to always
   take invariants out of the loop, and so in the case of promotion we also
   have to check the rhs.
   LHS_SIZE_UNIT and RHS_SIZE_UNIT contain the sizes of the corresponding
   types.  */

tree
vect_get_smallest_scalar_type (gimple *stmt, HOST_WIDE_INT *lhs_size_unit,
                               HOST_WIDE_INT *rhs_size_unit)
{
  tree scalar_type = gimple_expr_type (stmt);
  HOST_WIDE_INT lhs, rhs;

  lhs = rhs = TREE_INT_CST_LOW (TYPE_SIZE_UNIT (scalar_type));

  if (is_gimple_assign (stmt)
      && (gimple_assign_cast_p (stmt)
          || gimple_assign_rhs_code (stmt) == WIDEN_MULT_EXPR
          || gimple_assign_rhs_code (stmt) == WIDEN_LSHIFT_EXPR
          || gimple_assign_rhs_code (stmt) == FLOAT_EXPR))
    {
      tree rhs_type = TREE_TYPE (gimple_assign_rhs1 (stmt));

      rhs = TREE_INT_CST_LOW (TYPE_SIZE_UNIT (rhs_type));
      if (rhs < lhs)
        scalar_type = rhs_type;
    }

  *lhs_size_unit = lhs;
  *rhs_size_unit = rhs;
  return scalar_type;
}


/* Insert DDR into LOOP_VINFO list of ddrs that may alias and need to be
   tested at run-time.  Return TRUE if DDR was successfully inserted.
   Return false if versioning is not supported.  */

static bool
vect_mark_for_runtime_alias_test (ddr_p ddr, loop_vec_info loop_vinfo)
{
  struct loop *loop = LOOP_VINFO_LOOP (loop_vinfo);

  if ((unsigned) PARAM_VALUE (PARAM_VECT_MAX_VERSION_FOR_ALIAS_CHECKS) == 0)
    return false;

  if (dump_enabled_p ())
    {
      dump_printf_loc (MSG_NOTE, vect_location,
                       "mark for run-time aliasing test between ");
      dump_generic_expr (MSG_NOTE, TDF_SLIM, DR_REF (DDR_A (ddr)));
      dump_printf (MSG_NOTE,  " and ");
      dump_generic_expr (MSG_NOTE, TDF_SLIM, DR_REF (DDR_B (ddr)));
      dump_printf (MSG_NOTE, "\n");
    }

  if (optimize_loop_nest_for_size_p (loop))
    {
      if (dump_enabled_p ())
        dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                         "versioning not supported when optimizing"
                         " for size.\n");
      return false;
    }

  /* FORNOW: We don't support versioning with outer-loop vectorization.  */
  if (loop->inner)
    {
      if (dump_enabled_p ())
        dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                         "versioning not yet supported for outer-loops.\n");
      return false;
    }

  /* FORNOW: We don't support creating runtime alias tests for non-constant
     step.  */
  if (TREE_CODE (DR_STEP (DDR_A (ddr))) != INTEGER_CST
      || TREE_CODE (DR_STEP (DDR_B (ddr))) != INTEGER_CST)
    {
      if (dump_enabled_p ())
        dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                         "versioning not yet supported for non-constant "
                         "step\n");
      return false;
    }

  LOOP_VINFO_MAY_ALIAS_DDRS (loop_vinfo).safe_push (ddr);
  return true;
}


/* Function vect_analyze_data_ref_dependence.

   Return TRUE if there (might) exist a dependence between a memory-reference
   DRA and a memory-reference DRB.  When versioning for alias may check a
   dependence at run-time, return FALSE.  Adjust *MAX_VF according to
   the data dependence.  */

static bool
vect_analyze_data_ref_dependence (struct data_dependence_relation *ddr,
                                  loop_vec_info loop_vinfo, int *max_vf)
{
  unsigned int i;
  struct loop *loop = LOOP_VINFO_LOOP (loop_vinfo);
  struct data_reference *dra = DDR_A (ddr);
  struct data_reference *drb = DDR_B (ddr);
  stmt_vec_info stmtinfo_a = vinfo_for_stmt (DR_STMT (dra));
  stmt_vec_info stmtinfo_b = vinfo_for_stmt (DR_STMT (drb));
  lambda_vector dist_v;
  unsigned int loop_depth;

  /* In loop analysis all data references should be vectorizable.  */
  if (!STMT_VINFO_VECTORIZABLE (stmtinfo_a)
      || !STMT_VINFO_VECTORIZABLE (stmtinfo_b))
    gcc_unreachable ();

  /* Independent data accesses.  */
  if (DDR_ARE_DEPENDENT (ddr) == chrec_known)
    return false;

  if (dra == drb
      || (DR_IS_READ (dra) && DR_IS_READ (drb)))
    return false;

  /* Even if we have an anti-dependence then, as the vectorized loop covers at
     least two scalar iterations, there is always also a true dependence.
     As the vectorizer does not re-order loads and stores we can ignore
     the anti-dependence if TBAA can disambiguate both DRs similar to the
     case with known negative distance anti-dependences (positive
     distance anti-dependences would violate TBAA constraints).  */
  if (((DR_IS_READ (dra) && DR_IS_WRITE (drb))
       || (DR_IS_WRITE (dra) && DR_IS_READ (drb)))
      && !alias_sets_conflict_p (get_alias_set (DR_REF (dra)),
                                 get_alias_set (DR_REF (drb))))
    return false;

  /* Unknown data dependence.  */
  if (DDR_ARE_DEPENDENT (ddr) == chrec_dont_know)
    {
      /* If user asserted safelen consecutive iterations can be
         executed concurrently, assume independence.  */
      if (loop->safelen >= 2)
        {
          if (loop->safelen < *max_vf)
            *max_vf = loop->safelen;
          LOOP_VINFO_NO_DATA_DEPENDENCIES (loop_vinfo) = false;
          return false;
        }

      if (STMT_VINFO_GATHER_SCATTER_P (stmtinfo_a)
          || STMT_VINFO_GATHER_SCATTER_P (stmtinfo_b))
        {
          if (dump_enabled_p ())
            {
              dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                               "versioning for alias not supported for: "
                               "can't determine dependence between ");
              dump_generic_expr (MSG_MISSED_OPTIMIZATION, TDF_SLIM,
                                 DR_REF (dra));
              dump_printf (MSG_MISSED_OPTIMIZATION, " and ");
              dump_generic_expr (MSG_MISSED_OPTIMIZATION, TDF_SLIM,
                                 DR_REF (drb));
              dump_printf (MSG_MISSED_OPTIMIZATION, "\n");
            }
          return true;
        }

      if (dump_enabled_p ())
        {
          dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                           "versioning for alias required: "
                           "can't determine dependence between ");
          dump_generic_expr (MSG_MISSED_OPTIMIZATION, TDF_SLIM,
                             DR_REF (dra));
          dump_printf (MSG_MISSED_OPTIMIZATION, " and ");
          dump_generic_expr (MSG_MISSED_OPTIMIZATION, TDF_SLIM,
                             DR_REF (drb));
          dump_printf (MSG_MISSED_OPTIMIZATION, "\n");
        }

      /* Add to list of ddrs that need to be tested at run-time.  */
      return !vect_mark_for_runtime_alias_test (ddr, loop_vinfo);
    }

  /* Known data dependence.  */
  if (DDR_NUM_DIST_VECTS (ddr) == 0)
    {
      /* If user asserted safelen consecutive iterations can be
         executed concurrently, assume independence.  */
      if (loop->safelen >= 2)
        {
          if (loop->safelen < *max_vf)
            *max_vf = loop->safelen;
          LOOP_VINFO_NO_DATA_DEPENDENCIES (loop_vinfo) = false;
          return false;
        }

      if (STMT_VINFO_GATHER_SCATTER_P (stmtinfo_a)
          || STMT_VINFO_GATHER_SCATTER_P (stmtinfo_b))
        {
          if (dump_enabled_p ())
            {
              dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                               "versioning for alias not supported for: "
                               "bad dist vector for ");
              dump_generic_expr (MSG_MISSED_OPTIMIZATION, TDF_SLIM,
                                 DR_REF (dra));
              dump_printf (MSG_MISSED_OPTIMIZATION, " and ");
              dump_generic_expr (MSG_MISSED_OPTIMIZATION, TDF_SLIM,
                                 DR_REF (drb));
              dump_printf (MSG_MISSED_OPTIMIZATION, "\n");
            }
          return true;
        }

      if (dump_enabled_p ())
        {
          dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                           "versioning for alias required: "
                           "bad dist vector for ");
          dump_generic_expr (MSG_MISSED_OPTIMIZATION, TDF_SLIM, DR_REF (dra));
          dump_printf (MSG_MISSED_OPTIMIZATION,  " and ");
          dump_generic_expr (MSG_MISSED_OPTIMIZATION, TDF_SLIM, DR_REF (drb));
          dump_printf (MSG_MISSED_OPTIMIZATION, "\n");
        }
      /* Add to list of ddrs that need to be tested at run-time.  */
      return !vect_mark_for_runtime_alias_test (ddr, loop_vinfo);
    }

  loop_depth = index_in_loop_nest (loop->num, DDR_LOOP_NEST (ddr));
  FOR_EACH_VEC_ELT (DDR_DIST_VECTS (ddr), i, dist_v)
    {
      int dist = dist_v[loop_depth];

      if (dump_enabled_p ())
        dump_printf_loc (MSG_NOTE, vect_location,
                         "dependence distance  = %d.\n", dist);

      if (dist == 0)
        {
          if (dump_enabled_p ())
            {
              dump_printf_loc (MSG_NOTE, vect_location,
                               "dependence distance == 0 between ");
              dump_generic_expr (MSG_NOTE, TDF_SLIM, DR_REF (dra));
              dump_printf (MSG_NOTE, " and ");
              dump_generic_expr (MSG_NOTE, TDF_SLIM, DR_REF (drb));
              dump_printf (MSG_MISSED_OPTIMIZATION, "\n");
            }

          /* When we perform grouped accesses and perform implicit CSE
             by detecting equal accesses and doing disambiguation with
             runtime alias tests like for
                .. = a[i];
                .. = a[i+1];
                a[i] = ..;
                a[i+1] = ..;
                *p = ..;
                .. = a[i];
                .. = a[i+1];
             where we will end up loading { a[i], a[i+1] } once, make
             sure that inserting group loads before the first load and
             stores after the last store will do the right thing.
             Similar for groups like
                a[i] = ...;
                ... = a[i];
                a[i+1] = ...;
             where loads from the group interleave with the store.  */
          if (STMT_VINFO_GROUPED_ACCESS (stmtinfo_a)
              || STMT_VINFO_GROUPED_ACCESS (stmtinfo_b))
            {
              gimple *earlier_stmt;
              earlier_stmt = get_earlier_stmt (DR_STMT (dra), DR_STMT (drb));
              if (DR_IS_WRITE
                    (STMT_VINFO_DATA_REF (vinfo_for_stmt (earlier_stmt))))
                {
                  if (dump_enabled_p ())
                    dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                                     "READ_WRITE dependence in interleaving."
                                     "\n");
                  return true;
                }
            }

          continue;
        }

      if (dist > 0 && DDR_REVERSED_P (ddr))
        {
          /* If DDR_REVERSED_P the order of the data-refs in DDR was
             reversed (to make distance vector positive), and the actual
             distance is negative.  */
          if (dump_enabled_p ())
            dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                             "dependence distance negative.\n");
          /* Record a negative dependence distance to later limit the
             amount of stmt copying / unrolling we can perform.
             Only need to handle read-after-write dependence.  */
          if (DR_IS_READ (drb)
              && (STMT_VINFO_MIN_NEG_DIST (stmtinfo_b) == 0
                  || STMT_VINFO_MIN_NEG_DIST (stmtinfo_b) > (unsigned)dist))
            STMT_VINFO_MIN_NEG_DIST (stmtinfo_b) = dist;
          continue;
        }

      if (abs (dist) >= 2
          && abs (dist) < *max_vf)
        {
          /* The dependence distance requires reduction of the maximal
             vectorization factor.  */
          *max_vf = abs (dist);
          if (dump_enabled_p ())
            dump_printf_loc (MSG_NOTE, vect_location,
                             "adjusting maximal vectorization factor to %i\n",
                             *max_vf);
        }

      if (abs (dist) >= *max_vf)
        {
          /* Dependence distance does not create dependence, as far as
             vectorization is concerned, in this case.  */
          if (dump_enabled_p ())
            dump_printf_loc (MSG_NOTE, vect_location,
                             "dependence distance >= VF.\n");
          continue;
        }

      if (dump_enabled_p ())
        {
          dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                       "not vectorized, possible dependence "
                       "between data-refs ");
          dump_generic_expr (MSG_NOTE, TDF_SLIM, DR_REF (dra));
          dump_printf (MSG_NOTE,  " and ");
          dump_generic_expr (MSG_NOTE, TDF_SLIM, DR_REF (drb));
          dump_printf (MSG_NOTE,  "\n");
        }

      return true;
    }

  return false;
}

/* Function vect_analyze_data_ref_dependences.

   Examine all the data references in the loop, and make sure there do not
   exist any data dependences between them.  Set *MAX_VF according to
   the maximum vectorization factor the data dependences allow.  */

bool
vect_analyze_data_ref_dependences (loop_vec_info loop_vinfo, int *max_vf)
{
  unsigned int i;
  struct data_dependence_relation *ddr;

  if (dump_enabled_p ())
    dump_printf_loc (MSG_NOTE, vect_location,
                     "=== vect_analyze_data_ref_dependences ===\n");

  LOOP_VINFO_DDRS (loop_vinfo)
    .create (LOOP_VINFO_DATAREFS (loop_vinfo).length ()
             * LOOP_VINFO_DATAREFS (loop_vinfo).length ());
  LOOP_VINFO_NO_DATA_DEPENDENCIES (loop_vinfo) = true;
  if (!compute_all_dependences (LOOP_VINFO_DATAREFS (loop_vinfo),
                                &LOOP_VINFO_DDRS (loop_vinfo),
                                LOOP_VINFO_LOOP_NEST (loop_vinfo), true))
    return false;

  FOR_EACH_VEC_ELT (LOOP_VINFO_DDRS (loop_vinfo), i, ddr)
    if (vect_analyze_data_ref_dependence (ddr, loop_vinfo, max_vf))
      return false;

  return true;
}


/* Function vect_slp_analyze_data_ref_dependence.

   Return TRUE if there (might) exist a dependence between a memory-reference
   DRA and a memory-reference DRB.  When versioning for alias may check a
   dependence at run-time, return FALSE.  Adjust *MAX_VF according to
   the data dependence.  */

static bool
vect_slp_analyze_data_ref_dependence (struct data_dependence_relation *ddr)
{
  struct data_reference *dra = DDR_A (ddr);
  struct data_reference *drb = DDR_B (ddr);

  /* We need to check dependences of statements marked as unvectorizable
     as well, they still can prohibit vectorization.  */

  /* Independent data accesses.  */
  if (DDR_ARE_DEPENDENT (ddr) == chrec_known)
    return false;

  if (dra == drb)
    return false;

  /* Read-read is OK.  */
  if (DR_IS_READ (dra) && DR_IS_READ (drb))
    return false;

  /* If dra and drb are part of the same interleaving chain consider
     them independent.  */
  if (STMT_VINFO_GROUPED_ACCESS (vinfo_for_stmt (DR_STMT (dra)))
      && (GROUP_FIRST_ELEMENT (vinfo_for_stmt (DR_STMT (dra)))
          == GROUP_FIRST_ELEMENT (vinfo_for_stmt (DR_STMT (drb)))))
    return false;

  /* Unknown data dependence.  */
  if (DDR_ARE_DEPENDENT (ddr) == chrec_dont_know)
    {
      if  (dump_enabled_p ())
        {
          dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                           "can't determine dependence between ");
          dump_generic_expr (MSG_MISSED_OPTIMIZATION, TDF_SLIM, DR_REF (dra));
          dump_printf (MSG_MISSED_OPTIMIZATION,  " and ");
          dump_generic_expr (MSG_MISSED_OPTIMIZATION, TDF_SLIM, DR_REF (drb));
          dump_printf (MSG_MISSED_OPTIMIZATION,  "\n");
        }
    }
  else if (dump_enabled_p ())
    {
      dump_printf_loc (MSG_NOTE, vect_location,
                       "determined dependence between ");
      dump_generic_expr (MSG_NOTE, TDF_SLIM, DR_REF (dra));
      dump_printf (MSG_NOTE, " and ");
      dump_generic_expr (MSG_NOTE, TDF_SLIM, DR_REF (drb));
      dump_printf (MSG_NOTE,  "\n");
    }

  return true;
}


/* Analyze dependences involved in the transform of SLP NODE.  STORES
   contain the vector of scalar stores of this instance if we are
   disambiguating the loads.  */

static bool
vect_slp_analyze_node_dependences (slp_instance instance, slp_tree node,
                                   vec<gimple *> stores, gimple *last_store)
{
  /* This walks over all stmts involved in the SLP load/store done
     in NODE verifying we can sink them up to the last stmt in the
     group.  */
  gimple *last_access = vect_find_last_scalar_stmt_in_slp (node);
  for (unsigned k = 0; k < SLP_INSTANCE_GROUP_SIZE (instance); ++k)
    {
      gimple *access = SLP_TREE_SCALAR_STMTS (node)[k];
      if (access == last_access)
        continue;
      data_reference *dr_a = STMT_VINFO_DATA_REF (vinfo_for_stmt (access));
      for (gimple_stmt_iterator gsi = gsi_for_stmt (access);
           gsi_stmt (gsi) != last_access; gsi_next (&gsi))
        {
          gimple *stmt = gsi_stmt (gsi);
          if (! gimple_vuse (stmt)
              || (DR_IS_READ (dr_a) && ! gimple_vdef (stmt)))
            continue;

          /* If we couldn't record a (single) data reference for this
             stmt we have to give up.  */
          /* ???  Here and below if dependence analysis fails we can resort
             to the alias oracle which can handle more kinds of stmts.  */
          data_reference *dr_b = STMT_VINFO_DATA_REF (vinfo_for_stmt (stmt));
          if (!dr_b)
            return false;

          /* If we run into a store of this same instance (we've just
             marked those) then delay dependence checking until we run
             into the last store because this is where it will have
             been sunk to (and we verify if we can do that as well).  */
          if (gimple_visited_p (stmt))
            {
              if (stmt != last_store)
                continue;
              unsigned i;
              gimple *store;
              FOR_EACH_VEC_ELT (stores, i, store)
                {
                  data_reference *store_dr
                    = STMT_VINFO_DATA_REF (vinfo_for_stmt (store));
                  ddr_p ddr = initialize_data_dependence_relation
                                (dr_a, store_dr, vNULL);
                  if (vect_slp_analyze_data_ref_dependence (ddr))
                    {
                      free_dependence_relation (ddr);
                      return false;
                    }
                  free_dependence_relation (ddr);
                }
            }

          ddr_p ddr = initialize_data_dependence_relation (dr_a, dr_b, vNULL);
          if (vect_slp_analyze_data_ref_dependence (ddr))
            {
              free_dependence_relation (ddr);
              return false;
            }
          free_dependence_relation (ddr);
        }
    }
  return true;
}


/* Function vect_analyze_data_ref_dependences.

   Examine all the data references in the basic-block, and make sure there
   do not exist any data dependences between them.  Set *MAX_VF according to
   the maximum vectorization factor the data dependences allow.  */

bool
vect_slp_analyze_instance_dependence (slp_instance instance)
{
  if (dump_enabled_p ())
    dump_printf_loc (MSG_NOTE, vect_location,
                     "=== vect_slp_analyze_instance_dependence ===\n");

  /* The stores of this instance are at the root of the SLP tree.  */
  slp_tree store = SLP_INSTANCE_TREE (instance);
  if (! STMT_VINFO_DATA_REF (vinfo_for_stmt (SLP_TREE_SCALAR_STMTS (store)[0])))
    store = NULL;

  /* Verify we can sink stores to the vectorized stmt insert location.  */
  gimple *last_store = NULL;
  if (store)
    {
      if (! vect_slp_analyze_node_dependences (instance, store, vNULL, NULL))
        return false;

      /* Mark stores in this instance and remember the last one.  */
      last_store = vect_find_last_scalar_stmt_in_slp (store);
      for (unsigned k = 0; k < SLP_INSTANCE_GROUP_SIZE (instance); ++k)
        gimple_set_visited (SLP_TREE_SCALAR_STMTS (store)[k], true);
    }

  bool res = true;

  /* Verify we can sink loads to the vectorized stmt insert location,
     special-casing stores of this instance.  */
  slp_tree load;
  unsigned int i;
  FOR_EACH_VEC_ELT (SLP_INSTANCE_LOADS (instance), i, load)
    if (! vect_slp_analyze_node_dependences (instance, load,
                                             store
                                             ? SLP_TREE_SCALAR_STMTS (store)
                                             : vNULL, last_store))
      {
        res = false;
        break;
      }

  /* Unset the visited flag.  */
  if (store)
    for (unsigned k = 0; k < SLP_INSTANCE_GROUP_SIZE (instance); ++k)
      gimple_set_visited (SLP_TREE_SCALAR_STMTS (store)[k], false);

  return res;
}

/* Function vect_compute_data_ref_alignment

   Compute the misalignment of the data reference DR.

   Output:
   1. If during the misalignment computation it is found that the data reference
      cannot be vectorized then false is returned.
   2. DR_MISALIGNMENT (DR) is defined.

   FOR NOW: No analysis is actually performed. Misalignment is calculated
   only for trivial cases. TODO.  */

bool
vect_compute_data_ref_alignment (struct data_reference *dr)
{
  gimple *stmt = DR_STMT (dr);
  stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
  loop_vec_info loop_vinfo = STMT_VINFO_LOOP_VINFO (stmt_info);
  struct loop *loop = NULL;
  tree ref = DR_REF (dr);
  tree vectype;
  tree base, base_addr;
  tree misalign = NULL_TREE;
  tree aligned_to;
  unsigned HOST_WIDE_INT alignment;

  if (dump_enabled_p ())
    dump_printf_loc (MSG_NOTE, vect_location,
                     "vect_compute_data_ref_alignment:\n");

  if (loop_vinfo)
    loop = LOOP_VINFO_LOOP (loop_vinfo);

  /* Initialize misalignment to unknown.  */
  SET_DR_MISALIGNMENT (dr, -1);

  if (tree_fits_shwi_p (DR_STEP (dr)))
    misalign = DR_INIT (dr);
  aligned_to = DR_ALIGNED_TO (dr);
  base_addr = DR_BASE_ADDRESS (dr);
  vectype = STMT_VINFO_VECTYPE (stmt_info);

  /* In case the dataref is in an inner-loop of the loop that is being
     vectorized (LOOP), we use the base and misalignment information
     relative to the outer-loop (LOOP).  This is ok only if the misalignment
     stays the same throughout the execution of the inner-loop, which is why
     we have to check that the stride of the dataref in the inner-loop evenly
     divides by the vector size.  */
  if (loop && nested_in_vect_loop_p (loop, stmt))
    {
      tree step = DR_STEP (dr);

      if (tree_fits_shwi_p (step)
          && tree_to_shwi (step) % GET_MODE_SIZE (TYPE_MODE (vectype)) == 0)
        {
          if (dump_enabled_p ())
            dump_printf_loc (MSG_NOTE, vect_location,
                             "inner step divides the vector-size.\n");
          misalign = STMT_VINFO_DR_INIT (stmt_info);
          aligned_to = STMT_VINFO_DR_ALIGNED_TO (stmt_info);
          base_addr = STMT_VINFO_DR_BASE_ADDRESS (stmt_info);
        }
      else
        {
          if (dump_enabled_p ())
            dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                             "inner step doesn't divide the vector-size.\n");
          misalign = NULL_TREE;
        }
    }

  /* Similarly we can only use base and misalignment information relative to
     an innermost loop if the misalignment stays the same throughout the
     execution of the loop.  As above, this is the case if the stride of
     the dataref evenly divides by the vector size.  */
  else
    {
      tree step = DR_STEP (dr);
      unsigned vf = loop ? LOOP_VINFO_VECT_FACTOR (loop_vinfo) : 1;

      if (tree_fits_shwi_p (step)
          && ((tree_to_shwi (step) * vf)
              % GET_MODE_SIZE (TYPE_MODE (vectype)) != 0))
        {
          if (dump_enabled_p ())
            dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                             "step doesn't divide the vector-size.\n");
          misalign = NULL_TREE;
        }
    }

  /* To look at alignment of the base we have to preserve an inner MEM_REF
     as that carries alignment information of the actual access.  */
  base = ref;
  while (handled_component_p (base))
    base = TREE_OPERAND (base, 0);
  if (TREE_CODE (base) == MEM_REF)
    base = build2 (MEM_REF, TREE_TYPE (base), base_addr,
                   build_int_cst (TREE_TYPE (TREE_OPERAND (base, 1)), 0));
  unsigned int base_alignment = get_object_alignment (base);

  if (base_alignment >= TYPE_ALIGN (TREE_TYPE (vectype)))
    DR_VECT_AUX (dr)->base_element_aligned = true;

  alignment = TYPE_ALIGN_UNIT (vectype);

  if ((compare_tree_int (aligned_to, alignment) < 0)
      || !misalign)
    {
      if (dump_enabled_p ())
        {
          dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                           "Unknown alignment for access: ");
          dump_generic_expr (MSG_MISSED_OPTIMIZATION, TDF_SLIM, ref);
          dump_printf (MSG_MISSED_OPTIMIZATION, "\n");
        }
      return true;
    }

  if (base_alignment < TYPE_ALIGN (vectype))
    {
      /* Strip an inner MEM_REF to a bare decl if possible.  */
      if (TREE_CODE (base) == MEM_REF
          && integer_zerop (TREE_OPERAND (base, 1))
          && TREE_CODE (TREE_OPERAND (base, 0)) == ADDR_EXPR)
        base = TREE_OPERAND (TREE_OPERAND (base, 0), 0);

      if (!vect_can_force_dr_alignment_p (base, TYPE_ALIGN (vectype)))
        {
          if (dump_enabled_p ())
            {
              dump_printf_loc (MSG_NOTE, vect_location,
                               "can't force alignment of ref: ");
              dump_generic_expr (MSG_NOTE, TDF_SLIM, ref);
              dump_printf (MSG_NOTE, "\n");
            }
          return true;
        }

      /* Force the alignment of the decl.
         NOTE: This is the only change to the code we make during
         the analysis phase, before deciding to vectorize the loop.  */
      if (dump_enabled_p ())
        {
          dump_printf_loc (MSG_NOTE, vect_location, "force alignment of ");
          dump_generic_expr (MSG_NOTE, TDF_SLIM, ref);
          dump_printf (MSG_NOTE, "\n");
        }

      DR_VECT_AUX (dr)->base_decl = base;
      DR_VECT_AUX (dr)->base_misaligned = true;
      DR_VECT_AUX (dr)->base_element_aligned = true;
    }

  /* If this is a backward running DR then first access in the larger
     vectype actually is N-1 elements before the address in the DR.
     Adjust misalign accordingly.  */
  if (tree_int_cst_sgn (DR_STEP (dr)) < 0)
    {
      tree offset = ssize_int (TYPE_VECTOR_SUBPARTS (vectype) - 1);
      /* DR_STEP(dr) is the same as -TYPE_SIZE of the scalar type,
         otherwise we wouldn't be here.  */
      offset = fold_build2 (MULT_EXPR, ssizetype, offset, DR_STEP (dr));
      /* PLUS because DR_STEP was negative.  */
      misalign = size_binop (PLUS_EXPR, misalign, offset);
    }

  SET_DR_MISALIGNMENT (dr,
                       wi::mod_floor (misalign, alignment, SIGNED).to_uhwi ());

  if (dump_enabled_p ())
    {
      dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                       "misalign = %d bytes of ref ", DR_MISALIGNMENT (dr));
      dump_generic_expr (MSG_MISSED_OPTIMIZATION, TDF_SLIM, ref);
      dump_printf (MSG_MISSED_OPTIMIZATION, "\n");
    }

  return true;
}


/* Function vect_update_misalignment_for_peel

   DR - the data reference whose misalignment is to be adjusted.
   DR_PEEL - the data reference whose misalignment is being made
             zero in the vector loop by the peel.
   NPEEL - the number of iterations in the peel loop if the misalignment
           of DR_PEEL is known at compile time.  */

static void
vect_update_misalignment_for_peel (struct data_reference *dr,
                                   struct data_reference *dr_peel, int npeel)
{
  unsigned int i;
  vec<dr_p> same_align_drs;
  struct data_reference *current_dr;
  int dr_size = GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (DR_REF (dr))));
  int dr_peel_size = GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (DR_REF (dr_peel))));
  stmt_vec_info stmt_info = vinfo_for_stmt (DR_STMT (dr));
  stmt_vec_info peel_stmt_info = vinfo_for_stmt (DR_STMT (dr_peel));

 /* For interleaved data accesses the step in the loop must be multiplied by
     the size of the interleaving group.  */
  if (STMT_VINFO_GROUPED_ACCESS (stmt_info))
    dr_size *= GROUP_SIZE (vinfo_for_stmt (GROUP_FIRST_ELEMENT (stmt_info)));
  if (STMT_VINFO_GROUPED_ACCESS (peel_stmt_info))
    dr_peel_size *= GROUP_SIZE (peel_stmt_info);

  /* It can be assumed that the data refs with the same alignment as dr_peel
     are aligned in the vector loop.  */
  same_align_drs
    = STMT_VINFO_SAME_ALIGN_REFS (vinfo_for_stmt (DR_STMT (dr_peel)));
  FOR_EACH_VEC_ELT (same_align_drs, i, current_dr)
    {
      if (current_dr != dr)
        continue;
      gcc_assert (DR_MISALIGNMENT (dr) / dr_size ==
                  DR_MISALIGNMENT (dr_peel) / dr_peel_size);
      SET_DR_MISALIGNMENT (dr, 0);
      return;
    }

  if (known_alignment_for_access_p (dr)
      && known_alignment_for_access_p (dr_peel))
    {
      bool negative = tree_int_cst_compare (DR_STEP (dr), size_zero_node) < 0;
      int misal = DR_MISALIGNMENT (dr);
      tree vectype = STMT_VINFO_VECTYPE (stmt_info);
      misal += negative ? -npeel * dr_size : npeel * dr_size;
      misal &= (TYPE_ALIGN (vectype) / BITS_PER_UNIT) - 1;
      SET_DR_MISALIGNMENT (dr, misal);
      return;
    }

  if (dump_enabled_p ())
    dump_printf_loc (MSG_NOTE, vect_location, "Setting misalignment to -1.\n");
  SET_DR_MISALIGNMENT (dr, -1);
}


/* Function verify_data_ref_alignment

   Return TRUE if DR can be handled with respect to alignment.  */

static bool
verify_data_ref_alignment (data_reference_p dr)
{
  enum dr_alignment_support supportable_dr_alignment
    = vect_supportable_dr_alignment (dr, false);
  if (!supportable_dr_alignment)
    {
      if (dump_enabled_p ())
        {
          if (DR_IS_READ (dr))
            dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                             "not vectorized: unsupported unaligned load.");
          else
            dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                             "not vectorized: unsupported unaligned "
                             "store.");

          dump_generic_expr (MSG_MISSED_OPTIMIZATION, TDF_SLIM,
                             DR_REF (dr));
          dump_printf (MSG_MISSED_OPTIMIZATION, "\n");
        }
      return false;
    }

  if (supportable_dr_alignment != dr_aligned && dump_enabled_p ())
    dump_printf_loc (MSG_NOTE, vect_location,
                     "Vectorizing an unaligned access.\n");

  return true;
}

/* Function vect_verify_datarefs_alignment

   Return TRUE if all data references in the loop can be
   handled with respect to alignment.  */

bool
vect_verify_datarefs_alignment (loop_vec_info vinfo)
{
  vec<data_reference_p> datarefs = vinfo->datarefs;
  struct data_reference *dr;
  unsigned int i;

  FOR_EACH_VEC_ELT (datarefs, i, dr)
    {
      gimple *stmt = DR_STMT (dr);
      stmt_vec_info stmt_info = vinfo_for_stmt (stmt);

      if (!STMT_VINFO_RELEVANT_P (stmt_info))
        continue;

      /* For interleaving, only the alignment of the first access matters.   */
      if (STMT_VINFO_GROUPED_ACCESS (stmt_info)
          && GROUP_FIRST_ELEMENT (stmt_info) != stmt)
        continue;

      /* Strided accesses perform only component accesses, alignment is
         irrelevant for them.  */
      if (STMT_VINFO_STRIDED_P (stmt_info)
          && !STMT_VINFO_GROUPED_ACCESS (stmt_info))
        continue;

      if (! verify_data_ref_alignment (dr))
        return false;
    }

  return true;
}

/* Given an memory reference EXP return whether its alignment is less
   than its size.  */

static bool
not_size_aligned (tree exp)
{
  if (!tree_fits_uhwi_p (TYPE_SIZE (TREE_TYPE (exp))))
    return true;

  return (tree_to_uhwi (TYPE_SIZE (TREE_TYPE (exp)))
          > get_object_alignment (exp));
}

/* Function vector_alignment_reachable_p

   Return true if vector alignment for DR is reachable by peeling
   a few loop iterations.  Return false otherwise.  */

static bool
vector_alignment_reachable_p (struct data_reference *dr)
{
  gimple *stmt = DR_STMT (dr);
  stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
  tree vectype = STMT_VINFO_VECTYPE (stmt_info);

  if (STMT_VINFO_GROUPED_ACCESS (stmt_info))
    {
      /* For interleaved access we peel only if number of iterations in
         the prolog loop ({VF - misalignment}), is a multiple of the
         number of the interleaved accesses.  */
      int elem_size, mis_in_elements;
      int nelements = TYPE_VECTOR_SUBPARTS (vectype);

      /* FORNOW: handle only known alignment.  */
      if (!known_alignment_for_access_p (dr))
        return false;

      elem_size = GET_MODE_SIZE (TYPE_MODE (vectype)) / nelements;
      mis_in_elements = DR_MISALIGNMENT (dr) / elem_size;

      if ((nelements - mis_in_elements) % GROUP_SIZE (stmt_info))
        return false;
    }

  /* If misalignment is known at the compile time then allow peeling
     only if natural alignment is reachable through peeling.  */
  if (known_alignment_for_access_p (dr) && !aligned_access_p (dr))
    {
      HOST_WIDE_INT elmsize =
                int_cst_value (TYPE_SIZE_UNIT (TREE_TYPE (vectype)));
      if (dump_enabled_p ())
        {
          dump_printf_loc (MSG_NOTE, vect_location,
                           "data size =" HOST_WIDE_INT_PRINT_DEC, elmsize);
          dump_printf (MSG_NOTE,
                       ". misalignment = %d.\n", DR_MISALIGNMENT (dr));
        }
      if (DR_MISALIGNMENT (dr) % elmsize)
        {
          if (dump_enabled_p ())
            dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                             "data size does not divide the misalignment.\n");
          return false;
        }
    }

  if (!known_alignment_for_access_p (dr))
    {
      tree type = TREE_TYPE (DR_REF (dr));
      bool is_packed = not_size_aligned (DR_REF (dr));
      if (dump_enabled_p ())
        dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                         "Unknown misalignment, is_packed = %d\n",is_packed);
      if ((TYPE_USER_ALIGN (type) && !is_packed)
          || targetm.vectorize.vector_alignment_reachable (type, is_packed))
        return true;
      else
        return false;
    }

  return true;
}


/* Calculate the cost of the memory access represented by DR.  */

static void
vect_get_data_access_cost (struct data_reference *dr,
                           unsigned int *inside_cost,
                           unsigned int *outside_cost,
                           stmt_vector_for_cost *body_cost_vec)
{
  gimple *stmt = DR_STMT (dr);
  stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
  int nunits = TYPE_VECTOR_SUBPARTS (STMT_VINFO_VECTYPE (stmt_info));
  loop_vec_info loop_vinfo = STMT_VINFO_LOOP_VINFO (stmt_info);
  int vf = LOOP_VINFO_VECT_FACTOR (loop_vinfo);
  int ncopies = vf / nunits;

  if (DR_IS_READ (dr))
    vect_get_load_cost (dr, ncopies, true, inside_cost, outside_cost,
                        NULL, body_cost_vec, false);
  else
    vect_get_store_cost (dr, ncopies, inside_cost, body_cost_vec);

  if (dump_enabled_p ())
    dump_printf_loc (MSG_NOTE, vect_location,
                     "vect_get_data_access_cost: inside_cost = %d, "
                     "outside_cost = %d.\n", *inside_cost, *outside_cost);
}


typedef struct _vect_peel_info
{
  int npeel;
  struct data_reference *dr;
  unsigned int count;
} *vect_peel_info;

typedef struct _vect_peel_extended_info
{
  struct _vect_peel_info peel_info;
  unsigned int inside_cost;
  unsigned int outside_cost;
  stmt_vector_for_cost body_cost_vec;
} *vect_peel_extended_info;


/* Peeling hashtable helpers.  */

struct peel_info_hasher : free_ptr_hash <_vect_peel_info>
{
  static inline hashval_t hash (const _vect_peel_info *);
  static inline bool equal (const _vect_peel_info *, const _vect_peel_info *);
};

inline hashval_t
peel_info_hasher::hash (const _vect_peel_info *peel_info)
{
  return (hashval_t) peel_info->npeel;
}

inline bool
peel_info_hasher::equal (const _vect_peel_info *a, const _vect_peel_info *b)
{
  return (a->npeel == b->npeel);
}


/* Insert DR into peeling hash table with NPEEL as key.  */

static void
vect_peeling_hash_insert (hash_table<peel_info_hasher> *peeling_htab,
                          loop_vec_info loop_vinfo, struct data_reference *dr,
                          int npeel)
{
  struct _vect_peel_info elem, *slot;
  _vect_peel_info **new_slot;
  bool supportable_dr_alignment = vect_supportable_dr_alignment (dr, true);

  elem.npeel = npeel;
  slot = peeling_htab->find (&elem);
  if (slot)
    slot->count++;
  else
    {
      slot = XNEW (struct _vect_peel_info);
      slot->npeel = npeel;
      slot->dr = dr;
      slot->count = 1;
      new_slot = peeling_htab->find_slot (slot, INSERT);
      *new_slot = slot;
    }

  if (!supportable_dr_alignment
      && unlimited_cost_model (LOOP_VINFO_LOOP (loop_vinfo)))
    slot->count += VECT_MAX_COST;
}


/* Traverse peeling hash table to find peeling option that aligns maximum
   number of data accesses.  */

int
vect_peeling_hash_get_most_frequent (_vect_peel_info **slot,
                                     _vect_peel_extended_info *max)
{
  vect_peel_info elem = *slot;

  if (elem->count > max->peel_info.count
      || (elem->count == max->peel_info.count
          && max->peel_info.npeel > elem->npeel))
    {
      max->peel_info.npeel = elem->npeel;
      max->peel_info.count = elem->count;
      max->peel_info.dr = elem->dr;
    }

  return 1;
}


/* Traverse peeling hash table and calculate cost for each peeling option.
   Find the one with the lowest cost.  */

int
vect_peeling_hash_get_lowest_cost (_vect_peel_info **slot,
                                   _vect_peel_extended_info *min)
{
  vect_peel_info elem = *slot;
  int save_misalignment, dummy;
  unsigned int inside_cost = 0, outside_cost = 0, i;
  gimple *stmt = DR_STMT (elem->dr);
  stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
  loop_vec_info loop_vinfo = STMT_VINFO_LOOP_VINFO (stmt_info);
  vec<data_reference_p> datarefs = LOOP_VINFO_DATAREFS (loop_vinfo);
  struct data_reference *dr;
  stmt_vector_for_cost prologue_cost_vec, body_cost_vec, epilogue_cost_vec;

  prologue_cost_vec.create (2);
  body_cost_vec.create (2);
  epilogue_cost_vec.create (2);

  FOR_EACH_VEC_ELT (datarefs, i, dr)
    {
      stmt = DR_STMT (dr);
      stmt_info = vinfo_for_stmt (stmt);
      /* For interleaving, only the alignment of the first access
         matters.  */
      if (STMT_VINFO_GROUPED_ACCESS (stmt_info)
          && GROUP_FIRST_ELEMENT (stmt_info) != stmt)
        continue;

      save_misalignment = DR_MISALIGNMENT (dr);
      vect_update_misalignment_for_peel (dr, elem->dr, elem->npeel);
      vect_get_data_access_cost (dr, &inside_cost, &outside_cost,
                                 &body_cost_vec);
      SET_DR_MISALIGNMENT (dr, save_misalignment);
    }

  outside_cost += vect_get_known_peeling_cost
    (loop_vinfo, elem->npeel, &dummy,
     &LOOP_VINFO_SCALAR_ITERATION_COST (loop_vinfo),
     &prologue_cost_vec, &epilogue_cost_vec);

  /* Prologue and epilogue costs are added to the target model later.
     These costs depend only on the scalar iteration cost, the
     number of peeling iterations finally chosen, and the number of
     misaligned statements.  So discard the information found here.  */
  prologue_cost_vec.release ();
  epilogue_cost_vec.release ();

  if (inside_cost < min->inside_cost
      || (inside_cost == min->inside_cost && outside_cost < min->outside_cost))
    {
      min->inside_cost = inside_cost;
      min->outside_cost = outside_cost;
      min->body_cost_vec.release ();
      min->body_cost_vec = body_cost_vec;
      min->peel_info.dr = elem->dr;
      min->peel_info.npeel = elem->npeel;
    }
  else
    body_cost_vec.release ();

  return 1;
}


/* Choose best peeling option by traversing peeling hash table and either
   choosing an option with the lowest cost (if cost model is enabled) or the
   option that aligns as many accesses as possible.  */

static struct data_reference *
vect_peeling_hash_choose_best_peeling (hash_table<peel_info_hasher> *peeling_htab,
                                       loop_vec_info loop_vinfo,
                                       unsigned int *npeel,
                                       stmt_vector_for_cost *body_cost_vec)
{
   struct _vect_peel_extended_info res;

   res.peel_info.dr = NULL;
   res.body_cost_vec = stmt_vector_for_cost ();

   if (!unlimited_cost_model (LOOP_VINFO_LOOP (loop_vinfo)))
     {
       res.inside_cost = INT_MAX;
       res.outside_cost = INT_MAX;
       peeling_htab->traverse <_vect_peel_extended_info *,
                               vect_peeling_hash_get_lowest_cost> (&res);
     }
   else
     {
       res.peel_info.count = 0;
       peeling_htab->traverse <_vect_peel_extended_info *,
                               vect_peeling_hash_get_most_frequent> (&res);
     }

   *npeel = res.peel_info.npeel;
   *body_cost_vec = res.body_cost_vec;
   return res.peel_info.dr;
}


/* Function vect_enhance_data_refs_alignment

   This pass will use loop versioning and loop peeling in order to enhance
   the alignment of data references in the loop.

   FOR NOW: we assume that whatever versioning/peeling takes place, only the
   original loop is to be vectorized.  Any other loops that are created by
   the transformations performed in this pass - are not supposed to be
   vectorized.  This restriction will be relaxed.

   This pass will require a cost model to guide it whether to apply peeling
   or versioning or a combination of the two.  For example, the scheme that
   intel uses when given a loop with several memory accesses, is as follows:
   choose one memory access ('p') which alignment you want to force by doing
   peeling.  Then, either (1) generate a loop in which 'p' is aligned and all
   other accesses are not necessarily aligned, or (2) use loop versioning to
   generate one loop in which all accesses are aligned, and another loop in
   which only 'p' is necessarily aligned.

   ("Automatic Intra-Register Vectorization for the Intel Architecture",
   Aart J.C. Bik, Milind Girkar, Paul M. Grey and Ximmin Tian, International
   Journal of Parallel Programming, Vol. 30, No. 2, April 2002.)

   Devising a cost model is the most critical aspect of this work.  It will
   guide us on which access to peel for, whether to use loop versioning, how
   many versions to create, etc.  The cost model will probably consist of
   generic considerations as well as target specific considerations (on
   powerpc for example, misaligned stores are more painful than misaligned
   loads).

   Here are the general steps involved in alignment enhancements:

     -- original loop, before alignment analysis:
        for (i=0; i<N; i++){
          x = q[i];                     # DR_MISALIGNMENT(q) = unknown
          p[i] = y;                     # DR_MISALIGNMENT(p) = unknown
        }

     -- After vect_compute_data_refs_alignment:
        for (i=0; i<N; i++){
          x = q[i];                     # DR_MISALIGNMENT(q) = 3
          p[i] = y;                     # DR_MISALIGNMENT(p) = unknown
        }

     -- Possibility 1: we do loop versioning:
     if (p is aligned) {
        for (i=0; i<N; i++){    # loop 1A
          x = q[i];                     # DR_MISALIGNMENT(q) = 3
          p[i] = y;                     # DR_MISALIGNMENT(p) = 0
        }
     }
     else {
        for (i=0; i<N; i++){    # loop 1B
          x = q[i];                     # DR_MISALIGNMENT(q) = 3
          p[i] = y;                     # DR_MISALIGNMENT(p) = unaligned
        }
     }

     -- Possibility 2: we do loop peeling:
     for (i = 0; i < 3; i++){   # (scalar loop, not to be vectorized).
        x = q[i];
        p[i] = y;
     }
     for (i = 3; i < N; i++){   # loop 2A
        x = q[i];                       # DR_MISALIGNMENT(q) = 0
        p[i] = y;                       # DR_MISALIGNMENT(p) = unknown
     }

     -- Possibility 3: combination of loop peeling and versioning:
     for (i = 0; i < 3; i++){   # (scalar loop, not to be vectorized).
        x = q[i];
        p[i] = y;
     }
     if (p is aligned) {
        for (i = 3; i<N; i++){  # loop 3A
          x = q[i];                     # DR_MISALIGNMENT(q) = 0
          p[i] = y;                     # DR_MISALIGNMENT(p) = 0
        }
     }
     else {
        for (i = 3; i<N; i++){  # loop 3B
          x = q[i];                     # DR_MISALIGNMENT(q) = 0
          p[i] = y;                     # DR_MISALIGNMENT(p) = unaligned
        }
     }

     These loops are later passed to loop_transform to be vectorized.  The
     vectorizer will use the alignment information to guide the transformation
     (whether to generate regular loads/stores, or with special handling for
     misalignment).  */

bool
vect_enhance_data_refs_alignment (loop_vec_info loop_vinfo)
{
  vec<data_reference_p> datarefs = LOOP_VINFO_DATAREFS (loop_vinfo);
  struct loop *loop = LOOP_VINFO_LOOP (loop_vinfo);
  enum dr_alignment_support supportable_dr_alignment;
  struct data_reference *dr0 = NULL, *first_store = NULL;
  struct data_reference *dr;
  unsigned int i, j;
  bool do_peeling = false;
  bool do_versioning = false;
  bool stat;
  gimple *stmt;
  stmt_vec_info stmt_info;
  unsigned int npeel = 0;
  bool all_misalignments_unknown = true;
  unsigned int vf = LOOP_VINFO_VECT_FACTOR (loop_vinfo);
  unsigned possible_npeel_number = 1;
  tree vectype;
  unsigned int nelements, mis, same_align_drs_max = 0;
  stmt_vector_for_cost body_cost_vec = stmt_vector_for_cost ();
  hash_table<peel_info_hasher> peeling_htab (1);

  if (dump_enabled_p ())
    dump_printf_loc (MSG_NOTE, vect_location,
                     "=== vect_enhance_data_refs_alignment ===\n");

  /* Reset data so we can safely be called multiple times.  */
  LOOP_VINFO_MAY_MISALIGN_STMTS (loop_vinfo).truncate (0);
  LOOP_VINFO_PEELING_FOR_ALIGNMENT (loop_vinfo) = 0;

  /* While cost model enhancements are expected in the future, the high level
     view of the code at this time is as follows:

     A) If there is a misaligned access then see if peeling to align
        this access can make all data references satisfy
        vect_supportable_dr_alignment.  If so, update data structures
        as needed and return true.

     B) If peeling wasn't possible and there is a data reference with an
        unknown misalignment that does not satisfy vect_supportable_dr_alignment
        then see if loop versioning checks can be used to make all data
        references satisfy vect_supportable_dr_alignment.  If so, update
        data structures as needed and return true.

     C) If neither peeling nor versioning were successful then return false if
        any data reference does not satisfy vect_supportable_dr_alignment.

     D) Return true (all data references satisfy vect_supportable_dr_alignment).

     Note, Possibility 3 above (which is peeling and versioning together) is not
     being done at this time.  */

  /* (1) Peeling to force alignment.  */

  /* (1.1) Decide whether to perform peeling, and how many iterations to peel:
     Considerations:
     + How many accesses will become aligned due to the peeling
     - How many accesses will become unaligned due to the peeling,
       and the cost of misaligned accesses.
     - The cost of peeling (the extra runtime checks, the increase
       in code size).  */

  FOR_EACH_VEC_ELT (datarefs, i, dr)
    {
      stmt = DR_STMT (dr);
      stmt_info = vinfo_for_stmt (stmt);

      if (!STMT_VINFO_RELEVANT_P (stmt_info))
        continue;

      /* For interleaving, only the alignment of the first access
         matters.  */
      if (STMT_VINFO_GROUPED_ACCESS (stmt_info)
          && GROUP_FIRST_ELEMENT (stmt_info) != stmt)
        continue;

      /* For invariant accesses there is nothing to enhance.  */
      if (integer_zerop (DR_STEP (dr)))
        continue;

      /* Strided accesses perform only component accesses, alignment is
         irrelevant for them.  */
      if (STMT_VINFO_STRIDED_P (stmt_info)
          && !STMT_VINFO_GROUPED_ACCESS (stmt_info))
        continue;

      supportable_dr_alignment = vect_supportable_dr_alignment (dr, true);
      do_peeling = vector_alignment_reachable_p (dr);
      if (do_peeling)
        {
          if (known_alignment_for_access_p (dr))
            {
              unsigned int npeel_tmp;
              bool negative = tree_int_cst_compare (DR_STEP (dr),
                                                    size_zero_node) < 0;

              /* Save info about DR in the hash table.  */
              vectype = STMT_VINFO_VECTYPE (stmt_info);
              nelements = TYPE_VECTOR_SUBPARTS (vectype);
              mis = DR_MISALIGNMENT (dr) / GET_MODE_SIZE (TYPE_MODE (
                                                TREE_TYPE (DR_REF (dr))));
              npeel_tmp = (negative
                           ? (mis - nelements) : (nelements - mis))
                  & (nelements - 1);

              /* For multiple types, it is possible that the bigger type access
                 will have more than one peeling option.  E.g., a loop with two
                 types: one of size (vector size / 4), and the other one of
                 size (vector size / 8).  Vectorization factor will 8.  If both
                 access are misaligned by 3, the first one needs one scalar
                 iteration to be aligned, and the second one needs 5.  But the
                 the first one will be aligned also by peeling 5 scalar
                 iterations, and in that case both accesses will be aligned.
                 Hence, except for the immediate peeling amount, we also want
                 to try to add full vector size, while we don't exceed
                 vectorization factor.
                 We do this automtically for cost model, since we calculate cost
                 for every peeling option.  */
              if (unlimited_cost_model (LOOP_VINFO_LOOP (loop_vinfo)))
                {
                  if (STMT_SLP_TYPE (stmt_info))
                    possible_npeel_number
                      = (vf * GROUP_SIZE (stmt_info)) / nelements;
                  else
                    possible_npeel_number = vf / nelements;
                }

              /* Handle the aligned case. We may decide to align some other
                 access, making DR unaligned.  */
              if (DR_MISALIGNMENT (dr) == 0)
                {
                  npeel_tmp = 0;
                  if (unlimited_cost_model (LOOP_VINFO_LOOP (loop_vinfo)))
                    possible_npeel_number++;
                }

              for (j = 0; j < possible_npeel_number; j++)
                {
                  vect_peeling_hash_insert (&peeling_htab, loop_vinfo,
                                            dr, npeel_tmp);
                  npeel_tmp += nelements;
                }

              all_misalignments_unknown = false;
              /* Data-ref that was chosen for the case that all the
                 misalignments are unknown is not relevant anymore, since we
                 have a data-ref with known alignment.  */
              dr0 = NULL;
            }
          else
            {
              /* If we don't know any misalignment values, we prefer
                 peeling for data-ref that has the maximum number of data-refs
                 with the same alignment, unless the target prefers to align
                 stores over load.  */
              if (all_misalignments_unknown)
                {
                  unsigned same_align_drs
                    = STMT_VINFO_SAME_ALIGN_REFS (stmt_info).length ();
                  if (!dr0
                      || same_align_drs_max < same_align_drs)
                    {
                      same_align_drs_max = same_align_drs;
                      dr0 = dr;
                    }
                  /* For data-refs with the same number of related
                     accesses prefer the one where the misalign
                     computation will be invariant in the outermost loop.  */
                  else if (same_align_drs_max == same_align_drs)
                    {
                      struct loop *ivloop0, *ivloop;
                      ivloop0 = outermost_invariant_loop_for_expr
                          (loop, DR_BASE_ADDRESS (dr0));
                      ivloop = outermost_invariant_loop_for_expr
                          (loop, DR_BASE_ADDRESS (dr));
                      if ((ivloop && !ivloop0)
                          || (ivloop && ivloop0
                              && flow_loop_nested_p (ivloop, ivloop0)))
                        dr0 = dr;
                    }

                  if (!first_store && DR_IS_WRITE (dr))
                    first_store = dr;
                }

              /* If there are both known and unknown misaligned accesses in the
                 loop, we choose peeling amount according to the known
                 accesses.  */
              if (!supportable_dr_alignment)
                {
                  dr0 = dr;
                  if (!first_store && DR_IS_WRITE (dr))
                    first_store = dr;
                }
            }
        }
      else
        {
          if (!aligned_access_p (dr))
            {
              if (dump_enabled_p ())
                dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                                 "vector alignment may not be reachable\n");
              break;
            }
        }
    }

  /* Check if we can possibly peel the loop.  */
  if (!vect_can_advance_ivs_p (loop_vinfo)
      || !slpeel_can_duplicate_loop_p (loop, single_exit (loop))
      || loop->inner)
    do_peeling = false;

  if (do_peeling
      && all_misalignments_unknown
      && vect_supportable_dr_alignment (dr0, false))
    {
      /* Check if the target requires to prefer stores over loads, i.e., if
         misaligned stores are more expensive than misaligned loads (taking
         drs with same alignment into account).  */
      if (first_store && DR_IS_READ (dr0))
        {
          unsigned int load_inside_cost = 0, load_outside_cost = 0;
          unsigned int store_inside_cost = 0, store_outside_cost = 0;
          unsigned int load_inside_penalty = 0, load_outside_penalty = 0;
          unsigned int store_inside_penalty = 0, store_outside_penalty = 0;
          stmt_vector_for_cost dummy;
          dummy.create (2);

          vect_get_data_access_cost (dr0, &load_inside_cost, &load_outside_cost,
                                     &dummy);
          vect_get_data_access_cost (first_store, &store_inside_cost,
                                     &store_outside_cost, &dummy);

          dummy.release ();

          /* Calculate the penalty for leaving FIRST_STORE unaligned (by
             aligning the load DR0).  */
          load_inside_penalty = store_inside_cost;
          load_outside_penalty = store_outside_cost;
          for (i = 0;
               STMT_VINFO_SAME_ALIGN_REFS (vinfo_for_stmt (
                          DR_STMT (first_store))).iterate (i, &dr);
               i++)
            if (DR_IS_READ (dr))
              {
                load_inside_penalty += load_inside_cost;
                load_outside_penalty += load_outside_cost;
              }
            else
              {
                load_inside_penalty += store_inside_cost;
                load_outside_penalty += store_outside_cost;
              }

          /* Calculate the penalty for leaving DR0 unaligned (by
             aligning the FIRST_STORE).  */
          store_inside_penalty = load_inside_cost;
          store_outside_penalty = load_outside_cost;
          for (i = 0;
               STMT_VINFO_SAME_ALIGN_REFS (vinfo_for_stmt (
                      DR_STMT (dr0))).iterate (i, &dr);
               i++)
            if (DR_IS_READ (dr))
              {
                store_inside_penalty += load_inside_cost;
                store_outside_penalty += load_outside_cost;
              }
            else
              {
                store_inside_penalty += store_inside_cost;
                store_outside_penalty += store_outside_cost;
              }

          if (load_inside_penalty > store_inside_penalty
              || (load_inside_penalty == store_inside_penalty
                  && load_outside_penalty > store_outside_penalty))
            dr0 = first_store;
        }

      /* In case there are only loads with different unknown misalignments, use
         peeling only if it may help to align other accesses in the loop or
         if it may help improving load bandwith when we'd end up using
         unaligned loads.  */
      tree dr0_vt = STMT_VINFO_VECTYPE (vinfo_for_stmt (DR_STMT (dr0)));
      if (!first_store
          && !STMT_VINFO_SAME_ALIGN_REFS (
                  vinfo_for_stmt (DR_STMT (dr0))).length ()
          && (vect_supportable_dr_alignment (dr0, false)
              != dr_unaligned_supported
              || (builtin_vectorization_cost (vector_load, dr0_vt, 0)
                  == builtin_vectorization_cost (unaligned_load, dr0_vt, -1))))
        do_peeling = false;
    }

  if (do_peeling && !dr0)
    {
      /* Peeling is possible, but there is no data access that is not supported
         unless aligned. So we try to choose the best possible peeling.  */

      /* We should get here only if there are drs with known misalignment.  */
      gcc_assert (!all_misalignments_unknown);

      /* Choose the best peeling from the hash table.  */
      dr0 = vect_peeling_hash_choose_best_peeling (&peeling_htab,
                                                   loop_vinfo, &npeel,
                                                   &body_cost_vec);
      if (!dr0 || !npeel)
        do_peeling = false;
    }

  if (do_peeling)
    {
      stmt = DR_STMT (dr0);
      stmt_info = vinfo_for_stmt (stmt);
      vectype = STMT_VINFO_VECTYPE (stmt_info);
      nelements = TYPE_VECTOR_SUBPARTS (vectype);

      if (known_alignment_for_access_p (dr0))
        {
          bool negative = tree_int_cst_compare (DR_STEP (dr0),
                                                size_zero_node) < 0;
          if (!npeel)
            {
              /* Since it's known at compile time, compute the number of
                 iterations in the peeled loop (the peeling factor) for use in
                 updating DR_MISALIGNMENT values.  The peeling factor is the
                 vectorization factor minus the misalignment as an element
                 count.  */
              mis = DR_MISALIGNMENT (dr0);
              mis /= GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (DR_REF (dr0))));
              npeel = ((negative ? mis - nelements : nelements - mis)
                       & (nelements - 1));
            }

          /* For interleaved data access every iteration accesses all the
             members of the group, therefore we divide the number of iterations
             by the group size.  */
          stmt_info = vinfo_for_stmt (DR_STMT (dr0));
          if (STMT_VINFO_GROUPED_ACCESS (stmt_info))
            npeel /= GROUP_SIZE (stmt_info);

          if (dump_enabled_p ())
            dump_printf_loc (MSG_NOTE, vect_location,
                             "Try peeling by %d\n", npeel);
        }

      /* Ensure that all data refs can be vectorized after the peel.  */
      FOR_EACH_VEC_ELT (datarefs, i, dr)
        {
          int save_misalignment;

          if (dr == dr0)
            continue;

          stmt = DR_STMT (dr);
          stmt_info = vinfo_for_stmt (stmt);
          /* For interleaving, only the alignment of the first access
            matters.  */
          if (STMT_VINFO_GROUPED_ACCESS (stmt_info)
              && GROUP_FIRST_ELEMENT (stmt_info) != stmt)
            continue;

          /* Strided accesses perform only component accesses, alignment is
             irrelevant for them.  */
          if (STMT_VINFO_STRIDED_P (stmt_info)
              && !STMT_VINFO_GROUPED_ACCESS (stmt_info))
            continue;

          save_misalignment = DR_MISALIGNMENT (dr);
          vect_update_misalignment_for_peel (dr, dr0, npeel);
          supportable_dr_alignment = vect_supportable_dr_alignment (dr, false);
          SET_DR_MISALIGNMENT (dr, save_misalignment);

          if (!supportable_dr_alignment)
            {
              do_peeling = false;
              break;
            }
        }

      if (do_peeling && known_alignment_for_access_p (dr0) && npeel == 0)
        {
          stat = vect_verify_datarefs_alignment (loop_vinfo);
          if (!stat)
            do_peeling = false;
          else
            {
              body_cost_vec.release ();
              return stat;
            }
        }

      /* Cost model #1 - honor --param vect-max-peeling-for-alignment.  */
      if (do_peeling)
        {
          unsigned max_allowed_peel
            = PARAM_VALUE (PARAM_VECT_MAX_PEELING_FOR_ALIGNMENT);
          if (max_allowed_peel != (unsigned)-1)
            {
              unsigned max_peel = npeel;
              if (max_peel == 0)
                {
                  gimple *dr_stmt = DR_STMT (dr0);
                  stmt_vec_info vinfo = vinfo_for_stmt (dr_stmt);
                  tree vtype = STMT_VINFO_VECTYPE (vinfo);
                  max_peel = TYPE_VECTOR_SUBPARTS (vtype) - 1;
                }
              if (max_peel > max_allowed_peel)
                {
                  do_peeling = false;
                  if (dump_enabled_p ())
                    dump_printf_loc (MSG_NOTE, vect_location,
                        "Disable peeling, max peels reached: %d\n", max_peel);
                }
            }
        }

      /* Cost model #2 - if peeling may result in a remaining loop not
         iterating enough to be vectorized then do not peel.  */
      if (do_peeling
          && LOOP_VINFO_NITERS_KNOWN_P (loop_vinfo))
        {
          unsigned max_peel
            = npeel == 0 ? LOOP_VINFO_VECT_FACTOR (loop_vinfo) - 1 : npeel;
          if (LOOP_VINFO_INT_NITERS (loop_vinfo)
              < LOOP_VINFO_VECT_FACTOR (loop_vinfo) + max_peel)
            do_peeling = false;
        }

      if (do_peeling)
        {
          /* (1.2) Update the DR_MISALIGNMENT of each data reference DR_i.
             If the misalignment of DR_i is identical to that of dr0 then set
             DR_MISALIGNMENT (DR_i) to zero.  If the misalignment of DR_i and
             dr0 are known at compile time then increment DR_MISALIGNMENT (DR_i)
             by the peeling factor times the element size of DR_i (MOD the
             vectorization factor times the size).  Otherwise, the
             misalignment of DR_i must be set to unknown.  */
          FOR_EACH_VEC_ELT (datarefs, i, dr)
            if (dr != dr0)
              vect_update_misalignment_for_peel (dr, dr0, npeel);

          LOOP_VINFO_UNALIGNED_DR (loop_vinfo) = dr0;
          if (npeel)
            LOOP_VINFO_PEELING_FOR_ALIGNMENT (loop_vinfo) = npeel;
          else
            LOOP_VINFO_PEELING_FOR_ALIGNMENT (loop_vinfo)
              = DR_MISALIGNMENT (dr0);
          SET_DR_MISALIGNMENT (dr0, 0);
          if (dump_enabled_p ())
            {
              dump_printf_loc (MSG_NOTE, vect_location,
                               "Alignment of access forced using peeling.\n");
              dump_printf_loc (MSG_NOTE, vect_location,
                               "Peeling for alignment will be applied.\n");
            }
          /* The inside-loop cost will be accounted for in vectorizable_load
             and vectorizable_store correctly with adjusted alignments.
             Drop the body_cst_vec on the floor here.  */
          body_cost_vec.release ();

          stat = vect_verify_datarefs_alignment (loop_vinfo);
          gcc_assert (stat);
          return stat;
        }
    }

  body_cost_vec.release ();

  /* (2) Versioning to force alignment.  */

  /* Try versioning if:
     1) optimize loop for speed
     2) there is at least one unsupported misaligned data ref with an unknown
        misalignment, and
     3) all misaligned data refs with a known misalignment are supported, and
     4) the number of runtime alignment checks is within reason.  */

  do_versioning =
        optimize_loop_nest_for_speed_p (loop)
        && (!loop->inner); /* FORNOW */

  if (do_versioning)
    {
      FOR_EACH_VEC_ELT (datarefs, i, dr)
        {
          stmt = DR_STMT (dr);
          stmt_info = vinfo_for_stmt (stmt);

          /* For interleaving, only the alignment of the first access
             matters.  */
          if (aligned_access_p (dr)
              || (STMT_VINFO_GROUPED_ACCESS (stmt_info)
                  && GROUP_FIRST_ELEMENT (stmt_info) != stmt))
            continue;

          if (STMT_VINFO_STRIDED_P (stmt_info))
            {
              /* Strided loads perform only component accesses, alignment is
                 irrelevant for them.  */
              if (!STMT_VINFO_GROUPED_ACCESS (stmt_info))
                continue;
              do_versioning = false;
              break;
            }

          supportable_dr_alignment = vect_supportable_dr_alignment (dr, false);

          if (!supportable_dr_alignment)
            {
              gimple *stmt;
              int mask;
              tree vectype;

              if (known_alignment_for_access_p (dr)
                  || LOOP_VINFO_MAY_MISALIGN_STMTS (loop_vinfo).length ()
                     >= (unsigned) PARAM_VALUE (PARAM_VECT_MAX_VERSION_FOR_ALIGNMENT_CHECKS))
                {
                  do_versioning = false;
                  break;
                }

              stmt = DR_STMT (dr);
              vectype = STMT_VINFO_VECTYPE (vinfo_for_stmt (stmt));
              gcc_assert (vectype);

              /* The rightmost bits of an aligned address must be zeros.
                 Construct the mask needed for this test.  For example,
                 GET_MODE_SIZE for the vector mode V4SI is 16 bytes so the
                 mask must be 15 = 0xf. */
              mask = GET_MODE_SIZE (TYPE_MODE (vectype)) - 1;

              /* FORNOW: use the same mask to test all potentially unaligned
                 references in the loop.  The vectorizer currently supports
                 a single vector size, see the reference to
                 GET_MODE_NUNITS (TYPE_MODE (vectype)) where the
                 vectorization factor is computed.  */
              gcc_assert (!LOOP_VINFO_PTR_MASK (loop_vinfo)
                          || LOOP_VINFO_PTR_MASK (loop_vinfo) == mask);
              LOOP_VINFO_PTR_MASK (loop_vinfo) = mask;
              LOOP_VINFO_MAY_MISALIGN_STMTS (loop_vinfo).safe_push (
                      DR_STMT (dr));
            }
        }

      /* Versioning requires at least one misaligned data reference.  */
      if (!LOOP_REQUIRES_VERSIONING_FOR_ALIGNMENT (loop_vinfo))
        do_versioning = false;
      else if (!do_versioning)
        LOOP_VINFO_MAY_MISALIGN_STMTS (loop_vinfo).truncate (0);
    }

  if (do_versioning)
    {
      vec<gimple *> may_misalign_stmts
        = LOOP_VINFO_MAY_MISALIGN_STMTS (loop_vinfo);
      gimple *stmt;

      /* It can now be assumed that the data references in the statements
         in LOOP_VINFO_MAY_MISALIGN_STMTS will be aligned in the version
         of the loop being vectorized.  */
      FOR_EACH_VEC_ELT (may_misalign_stmts, i, stmt)
        {
          stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
          dr = STMT_VINFO_DATA_REF (stmt_info);
          SET_DR_MISALIGNMENT (dr, 0);
          if (dump_enabled_p ())
            dump_printf_loc (MSG_NOTE, vect_location,
                             "Alignment of access forced using versioning.\n");
        }

      if (dump_enabled_p ())
        dump_printf_loc (MSG_NOTE, vect_location,
                         "Versioning for alignment will be applied.\n");

      /* Peeling and versioning can't be done together at this time.  */
      gcc_assert (! (do_peeling && do_versioning));

      stat = vect_verify_datarefs_alignment (loop_vinfo);
      gcc_assert (stat);
      return stat;
    }

  /* This point is reached if neither peeling nor versioning is being done.  */
  gcc_assert (! (do_peeling || do_versioning));

  stat = vect_verify_datarefs_alignment (loop_vinfo);
  return stat;
}


/* Function vect_find_same_alignment_drs.

   Update group and alignment relations according to the chosen
   vectorization factor.  */

static void
vect_find_same_alignment_drs (struct data_dependence_relation *ddr,
                              loop_vec_info loop_vinfo)
{
  unsigned int i;
  struct loop *loop = LOOP_VINFO_LOOP (loop_vinfo);
  int vectorization_factor = LOOP_VINFO_VECT_FACTOR (loop_vinfo);
  struct data_reference *dra = DDR_A (ddr);
  struct data_reference *drb = DDR_B (ddr);
  stmt_vec_info stmtinfo_a = vinfo_for_stmt (DR_STMT (dra));
  stmt_vec_info stmtinfo_b = vinfo_for_stmt (DR_STMT (drb));
  int dra_size = GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (DR_REF (dra))));
  int drb_size = GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (DR_REF (drb))));
  lambda_vector dist_v;
  unsigned int loop_depth;

  if (DDR_ARE_DEPENDENT (ddr) == chrec_known)
    return;

  if (dra == drb)
    return;

  if (DDR_ARE_DEPENDENT (ddr) == chrec_dont_know)
    return;

  /* Loop-based vectorization and known data dependence.  */
  if (DDR_NUM_DIST_VECTS (ddr) == 0)
    return;

  /* Data-dependence analysis reports a distance vector of zero
     for data-references that overlap only in the first iteration
     but have different sign step (see PR45764).
     So as a sanity check require equal DR_STEP.  */
  if (!operand_equal_p (DR_STEP (dra), DR_STEP (drb), 0))
    return;

  loop_depth = index_in_loop_nest (loop->num, DDR_LOOP_NEST (ddr));
  FOR_EACH_VEC_ELT (DDR_DIST_VECTS (ddr), i, dist_v)
    {
      int dist = dist_v[loop_depth];

      if (dump_enabled_p ())
        dump_printf_loc (MSG_NOTE, vect_location,
                         "dependence distance  = %d.\n", dist);

      /* Same loop iteration.  */
      if (dist == 0
          || (dist % vectorization_factor == 0 && dra_size == drb_size))
        {
          /* Two references with distance zero have the same alignment.  */
          STMT_VINFO_SAME_ALIGN_REFS (stmtinfo_a).safe_push (drb);
          STMT_VINFO_SAME_ALIGN_REFS (stmtinfo_b).safe_push (dra);
          if (dump_enabled_p ())
            {
              dump_printf_loc (MSG_NOTE, vect_location,
                               "accesses have the same alignment.\n");
              dump_printf (MSG_NOTE,
                           "dependence distance modulo vf == 0 between ");
              dump_generic_expr (MSG_NOTE, TDF_SLIM, DR_REF (dra));
              dump_printf (MSG_NOTE,  " and ");
              dump_generic_expr (MSG_NOTE, TDF_SLIM, DR_REF (drb));
              dump_printf (MSG_NOTE, "\n");
            }
        }
    }
}


/* Function vect_analyze_data_refs_alignment

   Analyze the alignment of the data-references in the loop.
   Return FALSE if a data reference is found that cannot be vectorized.  */

bool
vect_analyze_data_refs_alignment (loop_vec_info vinfo)
{
  if (dump_enabled_p ())
    dump_printf_loc (MSG_NOTE, vect_location,
                     "=== vect_analyze_data_refs_alignment ===\n");

  /* Mark groups of data references with same alignment using
     data dependence information.  */
  vec<ddr_p> ddrs = vinfo->ddrs;
  struct data_dependence_relation *ddr;
  unsigned int i;

  FOR_EACH_VEC_ELT (ddrs, i, ddr)
    vect_find_same_alignment_drs (ddr, vinfo);

  vec<data_reference_p> datarefs = vinfo->datarefs;
  struct data_reference *dr;

  FOR_EACH_VEC_ELT (datarefs, i, dr)
    {
      stmt_vec_info stmt_info = vinfo_for_stmt (DR_STMT (dr));
      if (STMT_VINFO_VECTORIZABLE (stmt_info)
          && !vect_compute_data_ref_alignment (dr))
        {
          /* Strided accesses perform only component accesses, misalignment
             information is irrelevant for them.  */
          if (STMT_VINFO_STRIDED_P (stmt_info)
              && !STMT_VINFO_GROUPED_ACCESS (stmt_info))
            continue;

          if (dump_enabled_p ())
            dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                             "not vectorized: can't calculate alignment "
                             "for data ref.\n");

          return false;
        }
    }

  return true;
}


/* Analyze alignment of DRs of stmts in NODE.  */

static bool
vect_slp_analyze_and_verify_node_alignment (slp_tree node)
{
  /* We vectorize from the first scalar stmt in the node unless
     the node is permuted in which case we start from the first
     element in the group.  */
  gimple *first_stmt = SLP_TREE_SCALAR_STMTS (node)[0];
  data_reference_p first_dr = STMT_VINFO_DATA_REF (vinfo_for_stmt (first_stmt));
  if (SLP_TREE_LOAD_PERMUTATION (node).exists ())
    first_stmt = GROUP_FIRST_ELEMENT (vinfo_for_stmt (first_stmt));

  data_reference_p dr = STMT_VINFO_DATA_REF (vinfo_for_stmt (first_stmt));
  if (! vect_compute_data_ref_alignment (dr)
      /* For creating the data-ref pointer we need alignment of the
         first element anyway.  */
      || (dr != first_dr
          && ! vect_compute_data_ref_alignment (first_dr))
      || ! verify_data_ref_alignment (dr))
    {
      if (dump_enabled_p ())
        dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                         "not vectorized: bad data alignment in basic "
                         "block.\n");
      return false;
    }

  return true;
}

/* Function vect_slp_analyze_instance_alignment

   Analyze the alignment of the data-references in the SLP instance.
   Return FALSE if a data reference is found that cannot be vectorized.  */

bool
vect_slp_analyze_and_verify_instance_alignment (slp_instance instance)
{
  if (dump_enabled_p ())
    dump_printf_loc (MSG_NOTE, vect_location,
                     "=== vect_slp_analyze_and_verify_instance_alignment ===\n");

  slp_tree node;
  unsigned i;
  FOR_EACH_VEC_ELT (SLP_INSTANCE_LOADS (instance), i, node)
    if (! vect_slp_analyze_and_verify_node_alignment (node))
      return false;

  node = SLP_INSTANCE_TREE (instance);
  if (STMT_VINFO_DATA_REF (vinfo_for_stmt (SLP_TREE_SCALAR_STMTS (node)[0]))
      && ! vect_slp_analyze_and_verify_node_alignment
             (SLP_INSTANCE_TREE (instance)))
    return false;

  return true;
}


/* Analyze groups of accesses: check that DR belongs to a group of
   accesses of legal size, step, etc.  Detect gaps, single element
   interleaving, and other special cases. Set grouped access info.
   Collect groups of strided stores for further use in SLP analysis.
   Worker for vect_analyze_group_access.  */

static bool
vect_analyze_group_access_1 (struct data_reference *dr)
{
  tree step = DR_STEP (dr);
  tree scalar_type = TREE_TYPE (DR_REF (dr));
  HOST_WIDE_INT type_size = TREE_INT_CST_LOW (TYPE_SIZE_UNIT (scalar_type));
  gimple *stmt = DR_STMT (dr);
  stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
  loop_vec_info loop_vinfo = STMT_VINFO_LOOP_VINFO (stmt_info);
  bb_vec_info bb_vinfo = STMT_VINFO_BB_VINFO (stmt_info);
  HOST_WIDE_INT dr_step = -1;
  HOST_WIDE_INT groupsize, last_accessed_element = 1;
  bool slp_impossible = false;

  /* For interleaving, GROUPSIZE is STEP counted in elements, i.e., the
     size of the interleaving group (including gaps).  */
  if (tree_fits_shwi_p (step))
    {
      dr_step = tree_to_shwi (step);
      /* Check that STEP is a multiple of type size.  Otherwise there is
         a non-element-sized gap at the end of the group which we
         cannot represent in GROUP_GAP or GROUP_SIZE.
         ???  As we can handle non-constant step fine here we should
         simply remove uses of GROUP_GAP between the last and first
         element and instead rely on DR_STEP.  GROUP_SIZE then would
         simply not include that gap.  */
      if ((dr_step % type_size) != 0)
        {
          if (dump_enabled_p ())
            {
              dump_printf_loc (MSG_NOTE, vect_location,
                               "Step ");
              dump_generic_expr (MSG_NOTE, TDF_SLIM, step);
              dump_printf (MSG_NOTE,
                           " is not a multiple of the element size for ");
              dump_generic_expr (MSG_NOTE, TDF_SLIM, DR_REF (dr));
              dump_printf (MSG_NOTE, "\n");
            }
          return false;
        }
      groupsize = absu_hwi (dr_step) / type_size;
    }
  else
    groupsize = 0;

  /* Not consecutive access is possible only if it is a part of interleaving.  */
  if (!GROUP_FIRST_ELEMENT (vinfo_for_stmt (stmt)))
    {
      /* Check if it this DR is a part of interleaving, and is a single
         element of the group that is accessed in the loop.  */

      /* Gaps are supported only for loads. STEP must be a multiple of the type
         size.  The size of the group must be a power of 2.  */
      if (DR_IS_READ (dr)
          && (dr_step % type_size) == 0
          && groupsize > 0
          && exact_log2 (groupsize) != -1)
        {
          GROUP_FIRST_ELEMENT (vinfo_for_stmt (stmt)) = stmt;
          GROUP_SIZE (vinfo_for_stmt (stmt)) = groupsize;
          if (dump_enabled_p ())
            {
              dump_printf_loc (MSG_NOTE, vect_location,
                               "Detected single element interleaving ");
              dump_generic_expr (MSG_NOTE, TDF_SLIM, DR_REF (dr));
              dump_printf (MSG_NOTE, " step ");
              dump_generic_expr (MSG_NOTE, TDF_SLIM, step);
              dump_printf (MSG_NOTE, "\n");
            }

          return true;
        }

      if (dump_enabled_p ())
        {
          dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                           "not consecutive access ");
          dump_gimple_stmt (MSG_MISSED_OPTIMIZATION, TDF_SLIM, stmt, 0);
        }

      if (bb_vinfo)
        {
          /* Mark the statement as unvectorizable.  */
          STMT_VINFO_VECTORIZABLE (vinfo_for_stmt (DR_STMT (dr))) = false;
          return true;
        }

      dump_printf_loc (MSG_NOTE, vect_location, "using strided accesses\n");
      STMT_VINFO_STRIDED_P (stmt_info) = true;
      return true;
    }

  if (GROUP_FIRST_ELEMENT (vinfo_for_stmt (stmt)) == stmt)
    {
      /* First stmt in the interleaving chain. Check the chain.  */
      gimple *next = GROUP_NEXT_ELEMENT (vinfo_for_stmt (stmt));
      struct data_reference *data_ref = dr;
      unsigned int count = 1;
      tree prev_init = DR_INIT (data_ref);
      gimple *prev = stmt;
      HOST_WIDE_INT diff, gaps = 0;

      while (next)
        {
          /* Skip same data-refs.  In case that two or more stmts share
             data-ref (supported only for loads), we vectorize only the first
             stmt, and the rest get their vectorized loads from the first
             one.  */
          if (!tree_int_cst_compare (DR_INIT (data_ref),
                                     DR_INIT (STMT_VINFO_DATA_REF (
                                                   vinfo_for_stmt (next)))))
            {
              if (DR_IS_WRITE (data_ref))
                {
                  if (dump_enabled_p ())
                    dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                                     "Two store stmts share the same dr.\n");
                  return false;
                }

              if (dump_enabled_p ())
                dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                                 "Two or more load stmts share the same dr.\n");

              /* For load use the same data-ref load.  */
              GROUP_SAME_DR_STMT (vinfo_for_stmt (next)) = prev;

              prev = next;
              next = GROUP_NEXT_ELEMENT (vinfo_for_stmt (next));
              continue;
            }

          prev = next;
          data_ref = STMT_VINFO_DATA_REF (vinfo_for_stmt (next));

          /* All group members have the same STEP by construction.  */
          gcc_checking_assert (operand_equal_p (DR_STEP (data_ref), step, 0));

          /* Check that the distance between two accesses is equal to the type
             size. Otherwise, we have gaps.  */
          diff = (TREE_INT_CST_LOW (DR_INIT (data_ref))
                  - TREE_INT_CST_LOW (prev_init)) / type_size;
          if (diff != 1)
            {
              /* FORNOW: SLP of accesses with gaps is not supported.  */
              slp_impossible = true;
              if (DR_IS_WRITE (data_ref))
                {
                  if (dump_enabled_p ())
                    dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                                     "interleaved store with gaps\n");
                  return false;
                }

              gaps += diff - 1;
            }

          last_accessed_element += diff;

          /* Store the gap from the previous member of the group. If there is no
             gap in the access, GROUP_GAP is always 1.  */
          GROUP_GAP (vinfo_for_stmt (next)) = diff;

          prev_init = DR_INIT (data_ref);
          next = GROUP_NEXT_ELEMENT (vinfo_for_stmt (next));
          /* Count the number of data-refs in the chain.  */
          count++;
        }

      if (groupsize == 0)
        groupsize = count + gaps;

      if (groupsize > UINT_MAX)
        {
          if (dump_enabled_p ())
            dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                             "group is too large\n");
          return false;
        }

      /* Check that the size of the interleaving is equal to count for stores,
         i.e., that there are no gaps.  */
      if (groupsize != count
          && !DR_IS_READ (dr))
        {
          if (dump_enabled_p ())
            dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                             "interleaved store with gaps\n");
          return false;
        }

      /* If there is a gap after the last load in the group it is the
         difference between the groupsize and the last accessed
         element.
         When there is no gap, this difference should be 0.  */
      GROUP_GAP (vinfo_for_stmt (stmt)) = groupsize - last_accessed_element;

      GROUP_SIZE (vinfo_for_stmt (stmt)) = groupsize;
      if (dump_enabled_p ())
        {
          dump_printf_loc (MSG_NOTE, vect_location,
                           "Detected interleaving ");
          if (DR_IS_READ (dr))
            dump_printf (MSG_NOTE, "load ");
          else
            dump_printf (MSG_NOTE, "store ");
          dump_printf (MSG_NOTE, "of size %u starting with ",
                       (unsigned)groupsize);
          dump_gimple_stmt (MSG_NOTE, TDF_SLIM, stmt, 0);
          if (GROUP_GAP (vinfo_for_stmt (stmt)) != 0)
            dump_printf_loc (MSG_NOTE, vect_location,
                             "There is a gap of %u elements after the group\n",
                             GROUP_GAP (vinfo_for_stmt (stmt)));
        }

      /* SLP: create an SLP data structure for every interleaving group of
         stores for further analysis in vect_analyse_slp.  */
      if (DR_IS_WRITE (dr) && !slp_impossible)
        {
          if (loop_vinfo)
            LOOP_VINFO_GROUPED_STORES (loop_vinfo).safe_push (stmt);
          if (bb_vinfo)
            BB_VINFO_GROUPED_STORES (bb_vinfo).safe_push (stmt);
        }
    }

  return true;
}

/* Analyze groups of accesses: check that DR belongs to a group of
   accesses of legal size, step, etc.  Detect gaps, single element
   interleaving, and other special cases. Set grouped access info.
   Collect groups of strided stores for further use in SLP analysis.  */

static bool
vect_analyze_group_access (struct data_reference *dr)
{
  if (!vect_analyze_group_access_1 (dr))
    {
      /* Dissolve the group if present.  */
      gimple *next;
      gimple *stmt = GROUP_FIRST_ELEMENT (vinfo_for_stmt (DR_STMT (dr)));
      while (stmt)
        {
          stmt_vec_info vinfo = vinfo_for_stmt (stmt);
          next = GROUP_NEXT_ELEMENT (vinfo);
          GROUP_FIRST_ELEMENT (vinfo) = NULL;
          GROUP_NEXT_ELEMENT (vinfo) = NULL;
          stmt = next;
        }
      return false;
    }
  return true;
}

/* Analyze the access pattern of the data-reference DR.
   In case of non-consecutive accesses call vect_analyze_group_access() to
   analyze groups of accesses.  */

static bool
vect_analyze_data_ref_access (struct data_reference *dr)
{
  tree step = DR_STEP (dr);
  tree scalar_type = TREE_TYPE (DR_REF (dr));
  gimple *stmt = DR_STMT (dr);
  stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
  loop_vec_info loop_vinfo = STMT_VINFO_LOOP_VINFO (stmt_info);
  struct loop *loop = NULL;

  if (loop_vinfo)
    loop = LOOP_VINFO_LOOP (loop_vinfo);

  if (loop_vinfo && !step)
    {
      if (dump_enabled_p ())
        dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                         "bad data-ref access in loop\n");
      return false;
    }

  /* Allow loads with zero step in inner-loop vectorization.  */
  if (loop_vinfo && integer_zerop (step))
    {
      GROUP_FIRST_ELEMENT (vinfo_for_stmt (stmt)) = NULL;
      if (!nested_in_vect_loop_p (loop, stmt))
        return DR_IS_READ (dr);
      /* Allow references with zero step for outer loops marked
         with pragma omp simd only - it guarantees absence of
         loop-carried dependencies between inner loop iterations.  */
      if (!loop->force_vectorize)
        {
          if (dump_enabled_p ())
            dump_printf_loc (MSG_NOTE, vect_location,
                             "zero step in inner loop of nest\n");
          return false;
        }
    }

  if (loop && nested_in_vect_loop_p (loop, stmt))
    {
      /* Interleaved accesses are not yet supported within outer-loop
        vectorization for references in the inner-loop.  */
      GROUP_FIRST_ELEMENT (vinfo_for_stmt (stmt)) = NULL;

      /* For the rest of the analysis we use the outer-loop step.  */
      step = STMT_VINFO_DR_STEP (stmt_info);
      if (integer_zerop (step))
        {
          if (dump_enabled_p ())
            dump_printf_loc (MSG_NOTE, vect_location,
                             "zero step in outer loop.\n");
          return DR_IS_READ (dr);
        }
    }

  /* Consecutive?  */
  if (TREE_CODE (step) == INTEGER_CST)
    {
      HOST_WIDE_INT dr_step = TREE_INT_CST_LOW (step);
      if (!tree_int_cst_compare (step, TYPE_SIZE_UNIT (scalar_type))
          || (dr_step < 0
              && !compare_tree_int (TYPE_SIZE_UNIT (scalar_type), -dr_step)))
        {
          /* Mark that it is not interleaving.  */
          GROUP_FIRST_ELEMENT (vinfo_for_stmt (stmt)) = NULL;
          return true;
        }
    }

  if (loop && nested_in_vect_loop_p (loop, stmt))
    {
      if (dump_enabled_p ())
        dump_printf_loc (MSG_NOTE, vect_location,
                         "grouped access in outer loop.\n");
      return false;
    }


  /* Assume this is a DR handled by non-constant strided load case.  */
  if (TREE_CODE (step) != INTEGER_CST)
    return (STMT_VINFO_STRIDED_P (stmt_info)
            && (!STMT_VINFO_GROUPED_ACCESS (stmt_info)
                || vect_analyze_group_access (dr)));

  /* Not consecutive access - check if it's a part of interleaving group.  */
  return vect_analyze_group_access (dr);
}



/*  A helper function used in the comparator function to sort data
    references.  T1 and T2 are two data references to be compared.
    The function returns -1, 0, or 1.  */

static int
compare_tree (tree t1, tree t2)
{
  int i, cmp;
  enum tree_code code;
  char tclass;

  if (t1 == t2)
    return 0;
  if (t1 == NULL)
    return -1;
  if (t2 == NULL)
    return 1;

  STRIP_NOPS (t1);
  STRIP_NOPS (t2);

  if (TREE_CODE (t1) != TREE_CODE (t2))
    return TREE_CODE (t1) < TREE_CODE (t2) ? -1 : 1;

  code = TREE_CODE (t1);
  switch (code)
    {
    /* For const values, we can just use hash values for comparisons.  */
    case INTEGER_CST:
    case REAL_CST:
    case FIXED_CST:
    case STRING_CST:
    case COMPLEX_CST:
    case VECTOR_CST:
      {
        hashval_t h1 = iterative_hash_expr (t1, 0);
        hashval_t h2 = iterative_hash_expr (t2, 0);
        if (h1 != h2)
          return h1 < h2 ? -1 : 1;
        break;
      }

    case SSA_NAME:
      cmp = compare_tree (SSA_NAME_VAR (t1), SSA_NAME_VAR (t2));
      if (cmp != 0)
        return cmp;

      if (SSA_NAME_VERSION (t1) != SSA_NAME_VERSION (t2))
        return SSA_NAME_VERSION (t1) < SSA_NAME_VERSION (t2) ? -1 : 1;
      break;

    default:
      tclass = TREE_CODE_CLASS (code);

      /* For var-decl, we could compare their UIDs.  */
      if (tclass == tcc_declaration)
        {
          if (DECL_UID (t1) != DECL_UID (t2))
            return DECL_UID (t1) < DECL_UID (t2) ? -1 : 1;
          break;
        }

      /* For expressions with operands, compare their operands recursively.  */
      for (i = TREE_OPERAND_LENGTH (t1) - 1; i >= 0; --i)
        {
          cmp = compare_tree (TREE_OPERAND (t1, i), TREE_OPERAND (t2, i));
          if (cmp != 0)
            return cmp;
        }
    }

  return 0;
}


/* Compare two data-references DRA and DRB to group them into chunks
   suitable for grouping.  */

static int
dr_group_sort_cmp (const void *dra_, const void *drb_)
{
  data_reference_p dra = *(data_reference_p *)const_cast<void *>(dra_);
  data_reference_p drb = *(data_reference_p *)const_cast<void *>(drb_);
  int cmp;

  /* Stabilize sort.  */
  if (dra == drb)
    return 0;

  /* Ordering of DRs according to base.  */
  if (!operand_equal_p (DR_BASE_ADDRESS (dra), DR_BASE_ADDRESS (drb), 0))
    {
      cmp = compare_tree (DR_BASE_ADDRESS (dra), DR_BASE_ADDRESS (drb));
      if (cmp != 0)
        return cmp;
    }

  /* And according to DR_OFFSET.  */
  if (!dr_equal_offsets_p (dra, drb))
    {
      cmp = compare_tree (DR_OFFSET (dra), DR_OFFSET (drb));
      if (cmp != 0)
        return cmp;
    }

  /* Put reads before writes.  */
  if (DR_IS_READ (dra) != DR_IS_READ (drb))
    return DR_IS_READ (dra) ? -1 : 1;

  /* Then sort after access size.  */
  if (!operand_equal_p (TYPE_SIZE_UNIT (TREE_TYPE (DR_REF (dra))),
                        TYPE_SIZE_UNIT (TREE_TYPE (DR_REF (drb))), 0))
    {
      cmp = compare_tree (TYPE_SIZE_UNIT (TREE_TYPE (DR_REF (dra))),
                          TYPE_SIZE_UNIT (TREE_TYPE (DR_REF (drb))));
      if (cmp != 0)
        return cmp;
    }

  /* And after step.  */
  if (!operand_equal_p (DR_STEP (dra), DR_STEP (drb), 0))
    {
      cmp = compare_tree (DR_STEP (dra), DR_STEP (drb));
      if (cmp != 0)
        return cmp;
    }

  /* Then sort after DR_INIT.  In case of identical DRs sort after stmt UID.  */
  cmp = tree_int_cst_compare (DR_INIT (dra), DR_INIT (drb));
  if (cmp == 0)
    return gimple_uid (DR_STMT (dra)) < gimple_uid (DR_STMT (drb)) ? -1 : 1;
  return cmp;
}

/* Function vect_analyze_data_ref_accesses.

   Analyze the access pattern of all the data references in the loop.

   FORNOW: the only access pattern that is considered vectorizable is a
           simple step 1 (consecutive) access.

   FORNOW: handle only arrays and pointer accesses.  */

bool
vect_analyze_data_ref_accesses (vec_info *vinfo)
{
  unsigned int i;
  vec<data_reference_p> datarefs = vinfo->datarefs;
  struct data_reference *dr;

  if (dump_enabled_p ())
    dump_printf_loc (MSG_NOTE, vect_location,
                     "=== vect_analyze_data_ref_accesses ===\n");

  if (datarefs.is_empty ())
    return true;

  /* Sort the array of datarefs to make building the interleaving chains
     linear.  Don't modify the original vector's order, it is needed for
     determining what dependencies are reversed.  */
  vec<data_reference_p> datarefs_copy = datarefs.copy ();
  datarefs_copy.qsort (dr_group_sort_cmp);

  /* Build the interleaving chains.  */
  for (i = 0; i < datarefs_copy.length () - 1;)
    {
      data_reference_p dra = datarefs_copy[i];
      stmt_vec_info stmtinfo_a = vinfo_for_stmt (DR_STMT (dra));
      stmt_vec_info lastinfo = NULL;
      for (i = i + 1; i < datarefs_copy.length (); ++i)
        {
          data_reference_p drb = datarefs_copy[i];
          stmt_vec_info stmtinfo_b = vinfo_for_stmt (DR_STMT (drb));

          /* ???  Imperfect sorting (non-compatible types, non-modulo
             accesses, same accesses) can lead to a group to be artificially
             split here as we don't just skip over those.  If it really
             matters we can push those to a worklist and re-iterate
             over them.  The we can just skip ahead to the next DR here.  */

          /* Check that the data-refs have same first location (except init)
             and they are both either store or load (not load and store,
             not masked loads or stores).  */
          if (DR_IS_READ (dra) != DR_IS_READ (drb)
              || !operand_equal_p (DR_BASE_ADDRESS (dra),
                                   DR_BASE_ADDRESS (drb), 0)
              || !dr_equal_offsets_p (dra, drb)
              || !gimple_assign_single_p (DR_STMT (dra))
              || !gimple_assign_single_p (DR_STMT (drb)))
            break;

          /* Check that the data-refs have the same constant size.  */
          tree sza = TYPE_SIZE_UNIT (TREE_TYPE (DR_REF (dra)));
          tree szb = TYPE_SIZE_UNIT (TREE_TYPE (DR_REF (drb)));
          if (!tree_fits_uhwi_p (sza)
              || !tree_fits_uhwi_p (szb)
              || !tree_int_cst_equal (sza, szb))
            break;

          /* Check that the data-refs have the same step.  */
          if (!operand_equal_p (DR_STEP (dra), DR_STEP (drb), 0))
            break;

          /* Do not place the same access in the interleaving chain twice.  */
          if (tree_int_cst_compare (DR_INIT (dra), DR_INIT (drb)) == 0)
            break;

          /* Check the types are compatible.
             ???  We don't distinguish this during sorting.  */
          if (!types_compatible_p (TREE_TYPE (DR_REF (dra)),
                                   TREE_TYPE (DR_REF (drb))))
            break;

          /* Sorting has ensured that DR_INIT (dra) <= DR_INIT (drb).  */
          HOST_WIDE_INT init_a = TREE_INT_CST_LOW (DR_INIT (dra));
          HOST_WIDE_INT init_b = TREE_INT_CST_LOW (DR_INIT (drb));
          gcc_assert (init_a < init_b);

          /* If init_b == init_a + the size of the type * k, we have an
             interleaving, and DRA is accessed before DRB.  */
          HOST_WIDE_INT type_size_a = tree_to_uhwi (sza);
          if (type_size_a == 0
              || (init_b - init_a) % type_size_a != 0)
            break;

          /* If we have a store, the accesses are adjacent.  This splits
             groups into chunks we support (we don't support vectorization
             of stores with gaps).  */
          if (!DR_IS_READ (dra)
              && (init_b - (HOST_WIDE_INT) TREE_INT_CST_LOW
                                             (DR_INIT (datarefs_copy[i-1]))
                  != type_size_a))
            break;

          /* If the step (if not zero or non-constant) is greater than the
             difference between data-refs' inits this splits groups into
             suitable sizes.  */
          if (tree_fits_shwi_p (DR_STEP (dra)))
            {
              HOST_WIDE_INT step = tree_to_shwi (DR_STEP (dra));
              if (step != 0 && step <= (init_b - init_a))
                break;
            }

          if (dump_enabled_p ())
            {
              dump_printf_loc (MSG_NOTE, vect_location,
                               "Detected interleaving ");
              if (DR_IS_READ (dra))
                dump_printf (MSG_NOTE, "load ");
              else
                dump_printf (MSG_NOTE, "store ");
              dump_generic_expr (MSG_NOTE, TDF_SLIM, DR_REF (dra));
              dump_printf (MSG_NOTE,  " and ");
              dump_generic_expr (MSG_NOTE, TDF_SLIM, DR_REF (drb));
              dump_printf (MSG_NOTE, "\n");
            }

          /* Link the found element into the group list.  */
          if (!GROUP_FIRST_ELEMENT (stmtinfo_a))
            {
              GROUP_FIRST_ELEMENT (stmtinfo_a) = DR_STMT (dra);
              lastinfo = stmtinfo_a;
            }
          GROUP_FIRST_ELEMENT (stmtinfo_b) = DR_STMT (dra);
          GROUP_NEXT_ELEMENT (lastinfo) = DR_STMT (drb);
          lastinfo = stmtinfo_b;
        }
    }

  FOR_EACH_VEC_ELT (datarefs_copy, i, dr)
    if (STMT_VINFO_VECTORIZABLE (vinfo_for_stmt (DR_STMT (dr))) 
        && !vect_analyze_data_ref_access (dr))
      {
        if (dump_enabled_p ())
          dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                           "not vectorized: complicated access pattern.\n");

        if (is_a <bb_vec_info> (vinfo))
          {
            /* Mark the statement as not vectorizable.  */
            STMT_VINFO_VECTORIZABLE (vinfo_for_stmt (DR_STMT (dr))) = false;
            continue;
          }
        else
          {
            datarefs_copy.release ();
            return false;
          }
      }

  datarefs_copy.release ();
  return true;
}


/* Operator == between two dr_with_seg_len objects.

   This equality operator is used to make sure two data refs
   are the same one so that we will consider to combine the
   aliasing checks of those two pairs of data dependent data
   refs.  */

static bool
operator == (const dr_with_seg_len& d1,
             const dr_with_seg_len& d2)
{
  return operand_equal_p (DR_BASE_ADDRESS (d1.dr),
                          DR_BASE_ADDRESS (d2.dr), 0)
           && compare_tree (d1.offset, d2.offset) == 0
           && compare_tree (d1.seg_len, d2.seg_len) == 0;
}

/* Function comp_dr_with_seg_len_pair.

   Comparison function for sorting objects of dr_with_seg_len_pair_t
   so that we can combine aliasing checks in one scan.  */

static int
comp_dr_with_seg_len_pair (const void *p1_, const void *p2_)
{
  const dr_with_seg_len_pair_t* p1 = (const dr_with_seg_len_pair_t *) p1_;
  const dr_with_seg_len_pair_t* p2 = (const dr_with_seg_len_pair_t *) p2_;

  const dr_with_seg_len &p11 = p1->first,
                        &p12 = p1->second,
                        &p21 = p2->first,
                        &p22 = p2->second;

  /* For DR pairs (a, b) and (c, d), we only consider to merge the alias checks
     if a and c have the same basic address snd step, and b and d have the same
     address and step.  Therefore, if any a&c or b&d don't have the same address
     and step, we don't care the order of those two pairs after sorting.  */
  int comp_res;

  if ((comp_res = compare_tree (DR_BASE_ADDRESS (p11.dr),
                                DR_BASE_ADDRESS (p21.dr))) != 0)
    return comp_res;
  if ((comp_res = compare_tree (DR_BASE_ADDRESS (p12.dr),
                                DR_BASE_ADDRESS (p22.dr))) != 0)
    return comp_res;
  if ((comp_res = compare_tree (DR_STEP (p11.dr), DR_STEP (p21.dr))) != 0)
    return comp_res;
  if ((comp_res = compare_tree (DR_STEP (p12.dr), DR_STEP (p22.dr))) != 0)
    return comp_res;
  if ((comp_res = compare_tree (p11.offset, p21.offset)) != 0)
    return comp_res;
  if ((comp_res = compare_tree (p12.offset, p22.offset)) != 0)
    return comp_res;

  return 0;
}

/* Function vect_vfa_segment_size.

   Create an expression that computes the size of segment
   that will be accessed for a data reference.  The functions takes into
   account that realignment loads may access one more vector.

   Input:
     DR: The data reference.
     LENGTH_FACTOR: segment length to consider.

   Return an expression whose value is the size of segment which will be
   accessed by DR.  */

static tree
vect_vfa_segment_size (struct data_reference *dr, tree length_factor)
{
  tree segment_length;

  if (integer_zerop (DR_STEP (dr)))
    segment_length = TYPE_SIZE_UNIT (TREE_TYPE (DR_REF (dr)));
  else
    segment_length = size_binop (MULT_EXPR,
                                 fold_convert (sizetype, DR_STEP (dr)),
                                 fold_convert (sizetype, length_factor));

  if (vect_supportable_dr_alignment (dr, false)
        == dr_explicit_realign_optimized)
    {
      tree vector_size = TYPE_SIZE_UNIT
                          (STMT_VINFO_VECTYPE (vinfo_for_stmt (DR_STMT (dr))));

      segment_length = size_binop (PLUS_EXPR, segment_length, vector_size);
    }
  return segment_length;
}

/* Function vect_prune_runtime_alias_test_list.

   Prune a list of ddrs to be tested at run-time by versioning for alias.
   Merge several alias checks into one if possible.
   Return FALSE if resulting list of ddrs is longer then allowed by
   PARAM_VECT_MAX_VERSION_FOR_ALIAS_CHECKS, otherwise return TRUE.  */

bool
vect_prune_runtime_alias_test_list (loop_vec_info loop_vinfo)
{
  vec<ddr_p> may_alias_ddrs =
    LOOP_VINFO_MAY_ALIAS_DDRS (loop_vinfo);
  vec<dr_with_seg_len_pair_t>& comp_alias_ddrs =
    LOOP_VINFO_COMP_ALIAS_DDRS (loop_vinfo);
  int vect_factor = LOOP_VINFO_VECT_FACTOR (loop_vinfo);
  tree scalar_loop_iters = LOOP_VINFO_NITERS (loop_vinfo);

  ddr_p ddr;
  unsigned int i;
  tree length_factor;

  if (dump_enabled_p ())
    dump_printf_loc (MSG_NOTE, vect_location,
                     "=== vect_prune_runtime_alias_test_list ===\n");

  if (may_alias_ddrs.is_empty ())
    return true;

  /* Basically, for each pair of dependent data refs store_ptr_0
     and load_ptr_0, we create an expression:

     ((store_ptr_0 + store_segment_length_0) <= load_ptr_0)
     || (load_ptr_0 + load_segment_length_0) <= store_ptr_0))

     for aliasing checks.  However, in some cases we can decrease
     the number of checks by combining two checks into one.  For
     example, suppose we have another pair of data refs store_ptr_0
     and load_ptr_1, and if the following condition is satisfied:

     load_ptr_0 < load_ptr_1  &&
     load_ptr_1 - load_ptr_0 - load_segment_length_0 < store_segment_length_0

     (this condition means, in each iteration of vectorized loop,
     the accessed memory of store_ptr_0 cannot be between the memory
     of load_ptr_0 and load_ptr_1.)

     we then can use only the following expression to finish the
     alising checks between store_ptr_0 & load_ptr_0 and
     store_ptr_0 & load_ptr_1:

     ((store_ptr_0 + store_segment_length_0) <= load_ptr_0)
     || (load_ptr_1 + load_segment_length_1 <= store_ptr_0))

     Note that we only consider that load_ptr_0 and load_ptr_1 have the
     same basic address.  */

  comp_alias_ddrs.create (may_alias_ddrs.length ());

  /* First, we collect all data ref pairs for aliasing checks.  */
  FOR_EACH_VEC_ELT (may_alias_ddrs, i, ddr)
    {
      struct data_reference *dr_a, *dr_b;
      gimple *dr_group_first_a, *dr_group_first_b;
      tree segment_length_a, segment_length_b;
      gimple *stmt_a, *stmt_b;

      dr_a = DDR_A (ddr);
      stmt_a = DR_STMT (DDR_A (ddr));
      dr_group_first_a = GROUP_FIRST_ELEMENT (vinfo_for_stmt (stmt_a));
      if (dr_group_first_a)
        {
          stmt_a = dr_group_first_a;
          dr_a = STMT_VINFO_DATA_REF (vinfo_for_stmt (stmt_a));
        }

      dr_b = DDR_B (ddr);
      stmt_b = DR_STMT (DDR_B (ddr));
      dr_group_first_b = GROUP_FIRST_ELEMENT (vinfo_for_stmt (stmt_b));
      if (dr_group_first_b)
        {
          stmt_b = dr_group_first_b;
          dr_b = STMT_VINFO_DATA_REF (vinfo_for_stmt (stmt_b));
        }

      if (!operand_equal_p (DR_STEP (dr_a), DR_STEP (dr_b), 0))
        length_factor = scalar_loop_iters;
      else
        length_factor = size_int (vect_factor);
      segment_length_a = vect_vfa_segment_size (dr_a, length_factor);
      segment_length_b = vect_vfa_segment_size (dr_b, length_factor);

      dr_with_seg_len_pair_t dr_with_seg_len_pair
          (dr_with_seg_len (dr_a, segment_length_a),
           dr_with_seg_len (dr_b, segment_length_b));

      if (compare_tree (DR_BASE_ADDRESS (dr_a), DR_BASE_ADDRESS (dr_b)) > 0)
        std::swap (dr_with_seg_len_pair.first, dr_with_seg_len_pair.second);

      comp_alias_ddrs.safe_push (dr_with_seg_len_pair);
    }

  /* Second, we sort the collected data ref pairs so that we can scan
     them once to combine all possible aliasing checks.  */
  comp_alias_ddrs.qsort (comp_dr_with_seg_len_pair);

  /* Third, we scan the sorted dr pairs and check if we can combine
     alias checks of two neighbouring dr pairs.  */
  for (size_t i = 1; i < comp_alias_ddrs.length (); ++i)
    {
      /* Deal with two ddrs (dr_a1, dr_b1) and (dr_a2, dr_b2).  */
      dr_with_seg_len *dr_a1 = &comp_alias_ddrs[i-1].first,
                      *dr_b1 = &comp_alias_ddrs[i-1].second,
                      *dr_a2 = &comp_alias_ddrs[i].first,
                      *dr_b2 = &comp_alias_ddrs[i].second;

      /* Remove duplicate data ref pairs.  */
      if (*dr_a1 == *dr_a2 && *dr_b1 == *dr_b2)
        {
          if (dump_enabled_p ())
            {
              dump_printf_loc (MSG_NOTE, vect_location,
                               "found equal ranges ");
              dump_generic_expr (MSG_NOTE, TDF_SLIM,
                                 DR_REF (dr_a1->dr));
              dump_printf (MSG_NOTE,  ", ");
              dump_generic_expr (MSG_NOTE, TDF_SLIM,
                                 DR_REF (dr_b1->dr));
              dump_printf (MSG_NOTE,  " and ");
              dump_generic_expr (MSG_NOTE, TDF_SLIM,
                                 DR_REF (dr_a2->dr));
              dump_printf (MSG_NOTE,  ", ");
              dump_generic_expr (MSG_NOTE, TDF_SLIM,
                                 DR_REF (dr_b2->dr));
              dump_printf (MSG_NOTE, "\n");
            }

          comp_alias_ddrs.ordered_remove (i--);
          continue;
        }

      if (*dr_a1 == *dr_a2 || *dr_b1 == *dr_b2)
        {
          /* We consider the case that DR_B1 and DR_B2 are same memrefs,
             and DR_A1 and DR_A2 are two consecutive memrefs.  */
          if (*dr_a1 == *dr_a2)
            {
              std::swap (dr_a1, dr_b1);
              std::swap (dr_a2, dr_b2);
            }

          if (!operand_equal_p (DR_BASE_ADDRESS (dr_a1->dr),
                                DR_BASE_ADDRESS (dr_a2->dr),
                                0)
              || !tree_fits_shwi_p (dr_a1->offset)
              || !tree_fits_shwi_p (dr_a2->offset))
            continue;

          HOST_WIDE_INT diff = (tree_to_shwi (dr_a2->offset)
                                - tree_to_shwi (dr_a1->offset));


          /* Now we check if the following condition is satisfied:

             DIFF - SEGMENT_LENGTH_A < SEGMENT_LENGTH_B

             where DIFF = DR_A2->OFFSET - DR_A1->OFFSET.  However,
             SEGMENT_LENGTH_A or SEGMENT_LENGTH_B may not be constant so we
             have to make a best estimation.  We can get the minimum value
             of SEGMENT_LENGTH_B as a constant, represented by MIN_SEG_LEN_B,
             then either of the following two conditions can guarantee the
             one above:

             1: DIFF <= MIN_SEG_LEN_B
             2: DIFF - SEGMENT_LENGTH_A < MIN_SEG_LEN_B

             */

          HOST_WIDE_INT  min_seg_len_b = (tree_fits_shwi_p (dr_b1->seg_len)
                                          ? tree_to_shwi (dr_b1->seg_len)
                                          : vect_factor);

          if (diff <= min_seg_len_b
              || (tree_fits_shwi_p (dr_a1->seg_len)
                  && diff - tree_to_shwi (dr_a1->seg_len) < min_seg_len_b))
            {
              if (dump_enabled_p ())
                {
                  dump_printf_loc (MSG_NOTE, vect_location,
                                   "merging ranges for ");
                  dump_generic_expr (MSG_NOTE, TDF_SLIM,
                                     DR_REF (dr_a1->dr));
                  dump_printf (MSG_NOTE,  ", ");
                  dump_generic_expr (MSG_NOTE, TDF_SLIM,
                                     DR_REF (dr_b1->dr));
                  dump_printf (MSG_NOTE,  " and ");
                  dump_generic_expr (MSG_NOTE, TDF_SLIM,
                                     DR_REF (dr_a2->dr));
                  dump_printf (MSG_NOTE,  ", ");
                  dump_generic_expr (MSG_NOTE, TDF_SLIM,
                                     DR_REF (dr_b2->dr));
                  dump_printf (MSG_NOTE, "\n");
                }

              dr_a1->seg_len = size_binop (PLUS_EXPR,
                                           dr_a2->seg_len, size_int (diff));
              comp_alias_ddrs.ordered_remove (i--);
            }
        }
    }

  dump_printf_loc (MSG_NOTE, vect_location,
                   "improved number of alias checks from %d to %d\n",
                   may_alias_ddrs.length (), comp_alias_ddrs.length ());
  if ((int) comp_alias_ddrs.length () >
      PARAM_VALUE (PARAM_VECT_MAX_VERSION_FOR_ALIAS_CHECKS))
    return false;

  return true;
}

/* Check whether a non-affine read or write in stmt is suitable for gather load
   or scatter store and if so, return a builtin decl for that operation.  */

tree
vect_check_gather_scatter (gimple *stmt, loop_vec_info loop_vinfo, tree *basep,
                           tree *offp, int *scalep)
{
  HOST_WIDE_INT scale = 1, pbitpos, pbitsize;
  struct loop *loop = LOOP_VINFO_LOOP (loop_vinfo);
  stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
  struct data_reference *dr = STMT_VINFO_DATA_REF (stmt_info);
  tree offtype = NULL_TREE;
  tree decl, base, off;
  machine_mode pmode;
  int punsignedp, reversep, pvolatilep = 0;

  base = DR_REF (dr);
  /* For masked loads/stores, DR_REF (dr) is an artificial MEM_REF,
     see if we can use the def stmt of the address.  */
  if (is_gimple_call (stmt)
      && gimple_call_internal_p (stmt)
      && (gimple_call_internal_fn (stmt) == IFN_MASK_LOAD
          || gimple_call_internal_fn (stmt) == IFN_MASK_STORE)
      && TREE_CODE (base) == MEM_REF
      && TREE_CODE (TREE_OPERAND (base, 0)) == SSA_NAME
      && integer_zerop (TREE_OPERAND (base, 1))
      && !expr_invariant_in_loop_p (loop, TREE_OPERAND (base, 0)))
    {
      gimple *def_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (base, 0));
      if (is_gimple_assign (def_stmt)
          && gimple_assign_rhs_code (def_stmt) == ADDR_EXPR)
        base = TREE_OPERAND (gimple_assign_rhs1 (def_stmt), 0);
    }

  /* The gather and scatter builtins need address of the form
     loop_invariant + vector * {1, 2, 4, 8}
     or
     loop_invariant + sign_extend (vector) * { 1, 2, 4, 8 }.
     Unfortunately DR_BASE_ADDRESS/DR_OFFSET can be a mixture
     of loop invariants/SSA_NAMEs defined in the loop, with casts,
     multiplications and additions in it.  To get a vector, we need
     a single SSA_NAME that will be defined in the loop and will
     contain everything that is not loop invariant and that can be
     vectorized.  The following code attempts to find such a preexistng
     SSA_NAME OFF and put the loop invariants into a tree BASE
     that can be gimplified before the loop.  */
  base = get_inner_reference (base, &pbitsize, &pbitpos, &off, &pmode,
                              &punsignedp, &reversep, &pvolatilep, false);
  gcc_assert (base && (pbitpos % BITS_PER_UNIT) == 0 && !reversep);

  if (TREE_CODE (base) == MEM_REF)
    {
      if (!integer_zerop (TREE_OPERAND (base, 1)))
        {
          if (off == NULL_TREE)
            {
              offset_int moff = mem_ref_offset (base);
              off = wide_int_to_tree (sizetype, moff);
            }
          else
            off = size_binop (PLUS_EXPR, off,
                              fold_convert (sizetype, TREE_OPERAND (base, 1)));
        }
      base = TREE_OPERAND (base, 0);
    }
  else
    base = build_fold_addr_expr (base);

  if (off == NULL_TREE)
    off = size_zero_node;

  /* If base is not loop invariant, either off is 0, then we start with just
     the constant offset in the loop invariant BASE and continue with base
     as OFF, otherwise give up.
     We could handle that case by gimplifying the addition of base + off
     into some SSA_NAME and use that as off, but for now punt.  */
  if (!expr_invariant_in_loop_p (loop, base))
    {
      if (!integer_zerop (off))
        return NULL_TREE;
      off = base;
      base = size_int (pbitpos / BITS_PER_UNIT);
    }
  /* Otherwise put base + constant offset into the loop invariant BASE
     and continue with OFF.  */
  else
    {
      base = fold_convert (sizetype, base);
      base = size_binop (PLUS_EXPR, base, size_int (pbitpos / BITS_PER_UNIT));
    }

  /* OFF at this point may be either a SSA_NAME or some tree expression
     from get_inner_reference.  Try to peel off loop invariants from it
     into BASE as long as possible.  */
  STRIP_NOPS (off);
  while (offtype == NULL_TREE)
    {
      enum tree_code code;
      tree op0, op1, add = NULL_TREE;

      if (TREE_CODE (off) == SSA_NAME)
        {
          gimple *def_stmt = SSA_NAME_DEF_STMT (off);

          if (expr_invariant_in_loop_p (loop, off))
            return NULL_TREE;

          if (gimple_code (def_stmt) != GIMPLE_ASSIGN)
            break;

          op0 = gimple_assign_rhs1 (def_stmt);
          code = gimple_assign_rhs_code (def_stmt);
          op1 = gimple_assign_rhs2 (def_stmt);
        }
      else
        {
          if (get_gimple_rhs_class (TREE_CODE (off)) == GIMPLE_TERNARY_RHS)
            return NULL_TREE;
          code = TREE_CODE (off);
          extract_ops_from_tree (off, &code, &op0, &op1);
        }
      switch (code)
        {
        case POINTER_PLUS_EXPR:
        case PLUS_EXPR:
          if (expr_invariant_in_loop_p (loop, op0))
            {
              add = op0;
              off = op1;
            do_add:
              add = fold_convert (sizetype, add);
              if (scale != 1)
                add = size_binop (MULT_EXPR, add, size_int (scale));
              base = size_binop (PLUS_EXPR, base, add);
              continue;
            }
          if (expr_invariant_in_loop_p (loop, op1))
            {
              add = op1;
              off = op0;
              goto do_add;
            }
          break;
        case MINUS_EXPR:
          if (expr_invariant_in_loop_p (loop, op1))
            {
              add = fold_convert (sizetype, op1);
              add = size_binop (MINUS_EXPR, size_zero_node, add);
              off = op0;
              goto do_add;
            }
          break;
        case MULT_EXPR:
          if (scale == 1 && tree_fits_shwi_p (op1))
            {
              scale = tree_to_shwi (op1);
              off = op0;
              continue;
            }
          break;
        case SSA_NAME:
          off = op0;
          continue;
        CASE_CONVERT:
          if (!POINTER_TYPE_P (TREE_TYPE (op0))
              && !INTEGRAL_TYPE_P (TREE_TYPE (op0)))
            break;
          if (TYPE_PRECISION (TREE_TYPE (op0))
              == TYPE_PRECISION (TREE_TYPE (off)))
            {
              off = op0;
              continue;
            }
          if (TYPE_PRECISION (TREE_TYPE (op0))
              < TYPE_PRECISION (TREE_TYPE (off)))
            {
              off = op0;
              offtype = TREE_TYPE (off);
              STRIP_NOPS (off);
              continue;
            }
          break;
        default:
          break;
        }
      break;
    }

  /* If at the end OFF still isn't a SSA_NAME or isn't
     defined in the loop, punt.  */
  if (TREE_CODE (off) != SSA_NAME
      || expr_invariant_in_loop_p (loop, off))
    return NULL_TREE;

  if (offtype == NULL_TREE)
    offtype = TREE_TYPE (off);

  if (DR_IS_READ (dr))
    decl = targetm.vectorize.builtin_gather (STMT_VINFO_VECTYPE (stmt_info),
                                             offtype, scale);
  else
    decl = targetm.vectorize.builtin_scatter (STMT_VINFO_VECTYPE (stmt_info),
                                              offtype, scale);

  if (decl == NULL_TREE)
    return NULL_TREE;

  if (basep)
    *basep = base;
  if (offp)
    *offp = off;
  if (scalep)
    *scalep = scale;
  return decl;
}

/* Function vect_analyze_data_refs.

  Find all the data references in the loop or basic block.

   The general structure of the analysis of data refs in the vectorizer is as
   follows:
   1- vect_analyze_data_refs(loop/bb): call
      compute_data_dependences_for_loop/bb to find and analyze all data-refs
      in the loop/bb and their dependences.
   2- vect_analyze_dependences(): apply dependence testing using ddrs.
   3- vect_analyze_drs_alignment(): check that ref_stmt.alignment is ok.
   4- vect_analyze_drs_access(): check that ref_stmt.step is ok.

*/

bool
vect_analyze_data_refs (vec_info *vinfo, int *min_vf)
{
  struct loop *loop = NULL;
  unsigned int i;
  struct data_reference *dr;
  tree scalar_type;

  if (dump_enabled_p ())
    dump_printf_loc (MSG_NOTE, vect_location,
                     "=== vect_analyze_data_refs ===\n");

  if (loop_vec_info loop_vinfo = dyn_cast <loop_vec_info> (vinfo))
    loop = LOOP_VINFO_LOOP (loop_vinfo);

  /* Go through the data-refs, check that the analysis succeeded.  Update
     pointer from stmt_vec_info struct to DR and vectype.  */

  vec<data_reference_p> datarefs = vinfo->datarefs;
  FOR_EACH_VEC_ELT (datarefs, i, dr)
    {
      gimple *stmt;
      stmt_vec_info stmt_info;
      tree base, offset, init;
      enum { SG_NONE, GATHER, SCATTER } gatherscatter = SG_NONE;
      bool simd_lane_access = false;
      int vf;

again:
      if (!dr || !DR_REF (dr))
        {
          if (dump_enabled_p ())
            dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                             "not vectorized: unhandled data-ref\n");
          return false;
        }

      stmt = DR_STMT (dr);
      stmt_info = vinfo_for_stmt (stmt);

      /* Discard clobbers from the dataref vector.  We will remove
         clobber stmts during vectorization.  */
      if (gimple_clobber_p (stmt))
        {
          free_data_ref (dr);
          if (i == datarefs.length () - 1)
            {
              datarefs.pop ();
              break;
            }
          datarefs.ordered_remove (i);
          dr = datarefs[i];
          goto again;
        }

      /* Check that analysis of the data-ref succeeded.  */
      if (!DR_BASE_ADDRESS (dr) || !DR_OFFSET (dr) || !DR_INIT (dr)
          || !DR_STEP (dr))
        {
          bool maybe_gather
            = DR_IS_READ (dr)
              && !TREE_THIS_VOLATILE (DR_REF (dr))
              && targetm.vectorize.builtin_gather != NULL;
          bool maybe_scatter
            = DR_IS_WRITE (dr)
              && !TREE_THIS_VOLATILE (DR_REF (dr))
              && targetm.vectorize.builtin_scatter != NULL;
          bool maybe_simd_lane_access
            = is_a <loop_vec_info> (vinfo) && loop->simduid;

          /* If target supports vector gather loads or scatter stores, or if
             this might be a SIMD lane access, see if they can't be used.  */
          if (is_a <loop_vec_info> (vinfo)
              && (maybe_gather || maybe_scatter || maybe_simd_lane_access)
              && !nested_in_vect_loop_p (loop, stmt))
            {
              struct data_reference *newdr
                = create_data_ref (NULL, loop_containing_stmt (stmt),
                                   DR_REF (dr), stmt, maybe_scatter ? false : true);
              gcc_assert (newdr != NULL && DR_REF (newdr));
              if (DR_BASE_ADDRESS (newdr)
                  && DR_OFFSET (newdr)
                  && DR_INIT (newdr)
                  && DR_STEP (newdr)
                  && integer_zerop (DR_STEP (newdr)))
                {
                  if (maybe_simd_lane_access)
                    {
                      tree off = DR_OFFSET (newdr);
                      STRIP_NOPS (off);
                      if (TREE_CODE (DR_INIT (newdr)) == INTEGER_CST
                          && TREE_CODE (off) == MULT_EXPR
                          && tree_fits_uhwi_p (TREE_OPERAND (off, 1)))
                        {
                          tree step = TREE_OPERAND (off, 1);
                          off = TREE_OPERAND (off, 0);
                          STRIP_NOPS (off);
                          if (CONVERT_EXPR_P (off)
                              && TYPE_PRECISION (TREE_TYPE (TREE_OPERAND (off,
                                                                          0)))
                                 < TYPE_PRECISION (TREE_TYPE (off)))
                            off = TREE_OPERAND (off, 0);
                          if (TREE_CODE (off) == SSA_NAME)
                            {
                              gimple *def = SSA_NAME_DEF_STMT (off);
                              tree reft = TREE_TYPE (DR_REF (newdr));
                              if (is_gimple_call (def)
                                  && gimple_call_internal_p (def)
                                  && (gimple_call_internal_fn (def)
                                      == IFN_GOMP_SIMD_LANE))
                                {
                                  tree arg = gimple_call_arg (def, 0);
                                  gcc_assert (TREE_CODE (arg) == SSA_NAME);
                                  arg = SSA_NAME_VAR (arg);
                                  if (arg == loop->simduid
                                      /* For now.  */
                                      && tree_int_cst_equal
                                           (TYPE_SIZE_UNIT (reft),
                                            step))
                                    {
                                      DR_OFFSET (newdr) = ssize_int (0);
                                      DR_STEP (newdr) = step;
                                      DR_ALIGNED_TO (newdr)
                                        = size_int (BIGGEST_ALIGNMENT);
                                      dr = newdr;
                                      simd_lane_access = true;
                                    }
                                }
                            }
                        }
                    }
                  if (!simd_lane_access && (maybe_gather || maybe_scatter))
                    {
                      dr = newdr;
                      if (maybe_gather)
                        gatherscatter = GATHER;
                      else
                        gatherscatter = SCATTER;
                    }
                }
              if (gatherscatter == SG_NONE && !simd_lane_access)
                free_data_ref (newdr);
            }

          if (gatherscatter == SG_NONE && !simd_lane_access)
            {
              if (dump_enabled_p ())
                {
                  dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                                   "not vectorized: data ref analysis "
                                   "failed ");
                  dump_gimple_stmt (MSG_MISSED_OPTIMIZATION, TDF_SLIM, stmt, 0);
                  dump_printf (MSG_MISSED_OPTIMIZATION, "\n");
                }

              if (is_a <bb_vec_info> (vinfo))
                break;

              return false;
            }
        }

      if (TREE_CODE (DR_BASE_ADDRESS (dr)) == INTEGER_CST)
        {
          if (dump_enabled_p ())
            dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                             "not vectorized: base addr of dr is a "
                             "constant\n");

          if (is_a <bb_vec_info> (vinfo))
            break;

          if (gatherscatter != SG_NONE || simd_lane_access)
            free_data_ref (dr);
          return false;
        }

      if (TREE_THIS_VOLATILE (DR_REF (dr)))
        {
          if (dump_enabled_p ())
            {
              dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                               "not vectorized: volatile type ");
              dump_gimple_stmt (MSG_MISSED_OPTIMIZATION, TDF_SLIM, stmt, 0);
              dump_printf (MSG_MISSED_OPTIMIZATION, "\n");
            }

          if (is_a <bb_vec_info> (vinfo))
            break;

          return false;
        }

      if (stmt_can_throw_internal (stmt))
        {
          if (dump_enabled_p ())
            {
              dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                               "not vectorized: statement can throw an "
                               "exception ");
              dump_gimple_stmt (MSG_MISSED_OPTIMIZATION, TDF_SLIM, stmt, 0);
              dump_printf (MSG_MISSED_OPTIMIZATION, "\n");
            }

          if (is_a <bb_vec_info> (vinfo))
            break;

          if (gatherscatter != SG_NONE || simd_lane_access)
            free_data_ref (dr);
          return false;
        }

      if (TREE_CODE (DR_REF (dr)) == COMPONENT_REF
          && DECL_BIT_FIELD (TREE_OPERAND (DR_REF (dr), 1)))
        {
          if (dump_enabled_p ())
            {
              dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                               "not vectorized: statement is bitfield "
                               "access ");
              dump_gimple_stmt (MSG_MISSED_OPTIMIZATION, TDF_SLIM, stmt, 0);
              dump_printf (MSG_MISSED_OPTIMIZATION, "\n");
            }

          if (is_a <bb_vec_info> (vinfo))
            break;

          if (gatherscatter != SG_NONE || simd_lane_access)
            free_data_ref (dr);
          return false;
        }

      base = unshare_expr (DR_BASE_ADDRESS (dr));
      offset = unshare_expr (DR_OFFSET (dr));
      init = unshare_expr (DR_INIT (dr));

      if (is_gimple_call (stmt)
          && (!gimple_call_internal_p (stmt)
              || (gimple_call_internal_fn (stmt) != IFN_MASK_LOAD
                  && gimple_call_internal_fn (stmt) != IFN_MASK_STORE)))
        {
          if (dump_enabled_p ())
            {
              dump_printf_loc (MSG_MISSED_OPTIMIZATION,  vect_location,
                               "not vectorized: dr in a call ");
              dump_gimple_stmt (MSG_MISSED_OPTIMIZATION, TDF_SLIM, stmt, 0);
              dump_printf (MSG_MISSED_OPTIMIZATION, "\n");
            }

          if (is_a <bb_vec_info> (vinfo))
            break;

          if (gatherscatter != SG_NONE || simd_lane_access)
            free_data_ref (dr);
          return false;
        }

      /* Update DR field in stmt_vec_info struct.  */

      /* If the dataref is in an inner-loop of the loop that is considered for
         for vectorization, we also want to analyze the access relative to
         the outer-loop (DR contains information only relative to the
         inner-most enclosing loop).  We do that by building a reference to the
         first location accessed by the inner-loop, and analyze it relative to
         the outer-loop.  */
      if (loop && nested_in_vect_loop_p (loop, stmt))
        {
          tree outer_step, outer_base, outer_init;
          HOST_WIDE_INT pbitsize, pbitpos;
          tree poffset;
          machine_mode pmode;
          int punsignedp, preversep, pvolatilep;
          affine_iv base_iv, offset_iv;
          tree dinit;

          /* Build a reference to the first location accessed by the
             inner-loop: *(BASE+INIT).  (The first location is actually
             BASE+INIT+OFFSET, but we add OFFSET separately later).  */
          tree inner_base = build_fold_indirect_ref
                                (fold_build_pointer_plus (base, init));

          if (dump_enabled_p ())
            {
              dump_printf_loc (MSG_NOTE, vect_location,
                               "analyze in outer-loop: ");
              dump_generic_expr (MSG_NOTE, TDF_SLIM, inner_base);
              dump_printf (MSG_NOTE, "\n");
            }

          outer_base = get_inner_reference (inner_base, &pbitsize, &pbitpos,
                                            &poffset, &pmode, &punsignedp,
                                            &preversep, &pvolatilep, false);
          gcc_assert (outer_base != NULL_TREE);

          if (pbitpos % BITS_PER_UNIT != 0)
            {
              if (dump_enabled_p ())
                dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                                 "failed: bit offset alignment.\n");
              return false;
            }

          if (preversep)
            {
              if (dump_enabled_p ())
                dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                                 "failed: reverse storage order.\n");
              return false;
            }

          outer_base = build_fold_addr_expr (outer_base);
          if (!simple_iv (loop, loop_containing_stmt (stmt), outer_base,
                          &base_iv, false))
            {
              if (dump_enabled_p ())
                dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                                 "failed: evolution of base is not affine.\n");
              return false;
            }

          if (offset)
            {
              if (poffset)
                poffset = fold_build2 (PLUS_EXPR, TREE_TYPE (offset), offset,
                                       poffset);
              else
                poffset = offset;
            }

          if (!poffset)
            {
              offset_iv.base = ssize_int (0);
              offset_iv.step = ssize_int (0);
            }
          else if (!simple_iv (loop, loop_containing_stmt (stmt), poffset,
                               &offset_iv, false))
            {
              if (dump_enabled_p ())
                dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                                 "evolution of offset is not affine.\n");
              return false;
            }

          outer_init = ssize_int (pbitpos / BITS_PER_UNIT);
          split_constant_offset (base_iv.base, &base_iv.base, &dinit);
          outer_init =  size_binop (PLUS_EXPR, outer_init, dinit);
          split_constant_offset (offset_iv.base, &offset_iv.base, &dinit);
          outer_init =  size_binop (PLUS_EXPR, outer_init, dinit);

          outer_step = size_binop (PLUS_EXPR,
                                fold_convert (ssizetype, base_iv.step),
                                fold_convert (ssizetype, offset_iv.step));

          STMT_VINFO_DR_STEP (stmt_info) = outer_step;
          /* FIXME: Use canonicalize_base_object_address (base_iv.base); */
          STMT_VINFO_DR_BASE_ADDRESS (stmt_info) = base_iv.base;
          STMT_VINFO_DR_INIT (stmt_info) = outer_init;
          STMT_VINFO_DR_OFFSET (stmt_info) =
                                fold_convert (ssizetype, offset_iv.base);
          STMT_VINFO_DR_ALIGNED_TO (stmt_info) =
                                size_int (highest_pow2_factor (offset_iv.base));

          if (dump_enabled_p ())
            {
              dump_printf_loc (MSG_NOTE, vect_location,
                               "\touter base_address: ");
              dump_generic_expr (MSG_NOTE, TDF_SLIM,
                                 STMT_VINFO_DR_BASE_ADDRESS (stmt_info));
              dump_printf (MSG_NOTE, "\n\touter offset from base address: ");
              dump_generic_expr (MSG_NOTE, TDF_SLIM,
                                 STMT_VINFO_DR_OFFSET (stmt_info));
              dump_printf (MSG_NOTE,
                           "\n\touter constant offset from base address: ");
              dump_generic_expr (MSG_NOTE, TDF_SLIM,
                                 STMT_VINFO_DR_INIT (stmt_info));
              dump_printf (MSG_NOTE, "\n\touter step: ");
              dump_generic_expr (MSG_NOTE, TDF_SLIM,
                                 STMT_VINFO_DR_STEP (stmt_info));
              dump_printf (MSG_NOTE, "\n\touter aligned to: ");
              dump_generic_expr (MSG_NOTE, TDF_SLIM,
                                 STMT_VINFO_DR_ALIGNED_TO (stmt_info));
              dump_printf (MSG_NOTE, "\n");
            }
        }

      if (STMT_VINFO_DATA_REF (stmt_info))
        {
          if (dump_enabled_p ())
            {
              dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                               "not vectorized: more than one data ref "
                               "in stmt: ");
              dump_gimple_stmt (MSG_MISSED_OPTIMIZATION, TDF_SLIM, stmt, 0);
              dump_printf (MSG_MISSED_OPTIMIZATION, "\n");
            }

          if (is_a <bb_vec_info> (vinfo))
            break;

          if (gatherscatter != SG_NONE || simd_lane_access)
            free_data_ref (dr);
          return false;
        }

      STMT_VINFO_DATA_REF (stmt_info) = dr;
      if (simd_lane_access)
        {
          STMT_VINFO_SIMD_LANE_ACCESS_P (stmt_info) = true;
          free_data_ref (datarefs[i]);
          datarefs[i] = dr;
        }

      /* Set vectype for STMT.  */
      scalar_type = TREE_TYPE (DR_REF (dr));
      STMT_VINFO_VECTYPE (stmt_info)
        = get_vectype_for_scalar_type (scalar_type);
      if (!STMT_VINFO_VECTYPE (stmt_info))
        {
          if (dump_enabled_p ())
            {
              dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                               "not vectorized: no vectype for stmt: ");
              dump_gimple_stmt (MSG_MISSED_OPTIMIZATION, TDF_SLIM, stmt, 0);
              dump_printf (MSG_MISSED_OPTIMIZATION, " scalar_type: ");
              dump_generic_expr (MSG_MISSED_OPTIMIZATION, TDF_DETAILS,
                                 scalar_type);
              dump_printf (MSG_MISSED_OPTIMIZATION, "\n");
            }

          if (is_a <bb_vec_info> (vinfo))
            {
              /* No vector type is fine, the ref can still participate
                 in dependence analysis, we just can't vectorize it.  */
              STMT_VINFO_VECTORIZABLE (stmt_info) = false;
              continue;
            }

          if (gatherscatter != SG_NONE || simd_lane_access)
            {
              STMT_VINFO_DATA_REF (stmt_info) = NULL;
              if (gatherscatter != SG_NONE)
                free_data_ref (dr);
            }
          return false;
        }
      else
        {
          if (dump_enabled_p ())
            {
              dump_printf_loc (MSG_NOTE, vect_location,
                               "got vectype for stmt: ");
              dump_gimple_stmt (MSG_NOTE, TDF_SLIM, stmt, 0);
              dump_generic_expr (MSG_NOTE, TDF_SLIM,
                                 STMT_VINFO_VECTYPE (stmt_info));
              dump_printf (MSG_NOTE, "\n");
            }
        }

      /* Adjust the minimal vectorization factor according to the
         vector type.  */
      vf = TYPE_VECTOR_SUBPARTS (STMT_VINFO_VECTYPE (stmt_info));
      if (vf > *min_vf)
        *min_vf = vf;

      if (gatherscatter != SG_NONE)
        {
          tree off;
          if (!vect_check_gather_scatter (stmt, as_a <loop_vec_info> (vinfo),
                                          NULL, &off, NULL)
              || get_vectype_for_scalar_type (TREE_TYPE (off)) == NULL_TREE)
            {
              STMT_VINFO_DATA_REF (stmt_info) = NULL;
              free_data_ref (dr);
              if (dump_enabled_p ())
                {
                  dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                                   (gatherscatter == GATHER) ?
                                   "not vectorized: not suitable for gather "
                                   "load " :
                                   "not vectorized: not suitable for scatter "
                                   "store ");
                  dump_gimple_stmt (MSG_MISSED_OPTIMIZATION, TDF_SLIM, stmt, 0);
                  dump_printf (MSG_MISSED_OPTIMIZATION, "\n");
                }
              return false;
            }

          datarefs[i] = dr;
          STMT_VINFO_GATHER_SCATTER_P (stmt_info) = gatherscatter;
        }

      else if (is_a <loop_vec_info> (vinfo)
               && TREE_CODE (DR_STEP (dr)) != INTEGER_CST)
        {
          if (nested_in_vect_loop_p (loop, stmt))
            {
              if (dump_enabled_p ())
                {
                  dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location, 
                                   "not vectorized: not suitable for strided "
                                   "load ");
                  dump_gimple_stmt (MSG_MISSED_OPTIMIZATION, TDF_SLIM, stmt, 0);
                  dump_printf (MSG_MISSED_OPTIMIZATION, "\n");
                }
              return false;
            }
          STMT_VINFO_STRIDED_P (stmt_info) = true;
        }
    }

  /* If we stopped analysis at the first dataref we could not analyze
     when trying to vectorize a basic-block mark the rest of the datarefs
     as not vectorizable and truncate the vector of datarefs.  That
     avoids spending useless time in analyzing their dependence.  */
  if (i != datarefs.length ())
    {
      gcc_assert (is_a <bb_vec_info> (vinfo));
      for (unsigned j = i; j < datarefs.length (); ++j)
        {
          data_reference_p dr = datarefs[j];
          STMT_VINFO_VECTORIZABLE (vinfo_for_stmt (DR_STMT (dr))) = false;
          free_data_ref (dr);
        }
      datarefs.truncate (i);
    }

  return true;
}


/* Function vect_get_new_vect_var.

   Returns a name for a new variable.  The current naming scheme appends the
   prefix "vect_" or "vect_p" (depending on the value of VAR_KIND) to
   the name of vectorizer generated variables, and appends that to NAME if
   provided.  */

tree
vect_get_new_vect_var (tree type, enum vect_var_kind var_kind, const char *name)
{
  const char *prefix;
  tree new_vect_var;

  switch (var_kind)
  {
  case vect_simple_var:
    prefix = "vect";
    break;
  case vect_scalar_var:
    prefix = "stmp";
    break;
  case vect_mask_var:
    prefix = "mask";
    break;
  case vect_pointer_var:
    prefix = "vectp";
    break;
  default:
    gcc_unreachable ();
  }

  if (name)
    {
      char* tmp = concat (prefix, "_", name, NULL);
      new_vect_var = create_tmp_reg (type, tmp);
      free (tmp);
    }
  else
    new_vect_var = create_tmp_reg (type, prefix);

  return new_vect_var;
}

/* Like vect_get_new_vect_var but return an SSA name.  */

tree
vect_get_new_ssa_name (tree type, enum vect_var_kind var_kind, const char *name)
{
  const char *prefix;
  tree new_vect_var;

  switch (var_kind)
  {
  case vect_simple_var:
    prefix = "vect";
    break;
  case vect_scalar_var:
    prefix = "stmp";
    break;
  case vect_pointer_var:
    prefix = "vectp";
    break;
  default:
    gcc_unreachable ();
  }

  if (name)
    {
      char* tmp = concat (prefix, "_", name, NULL);
      new_vect_var = make_temp_ssa_name (type, NULL, tmp);
      free (tmp);
    }
  else
    new_vect_var = make_temp_ssa_name (type, NULL, prefix);

  return new_vect_var;
}

/* Duplicate ptr info and set alignment/misaligment on NAME from DR.  */

static void
vect_duplicate_ssa_name_ptr_info (tree name, data_reference *dr,
                                  stmt_vec_info stmt_info)
{
  duplicate_ssa_name_ptr_info (name, DR_PTR_INFO (dr));
  unsigned int align = TYPE_ALIGN_UNIT (STMT_VINFO_VECTYPE (stmt_info));
  int misalign = DR_MISALIGNMENT (dr);
  if (misalign == -1)
    mark_ptr_info_alignment_unknown (SSA_NAME_PTR_INFO (name));
  else
    set_ptr_info_alignment (SSA_NAME_PTR_INFO (name), align, misalign);
}

/* Function vect_create_addr_base_for_vector_ref.

   Create an expression that computes the address of the first memory location
   that will be accessed for a data reference.

   Input:
   STMT: The statement containing the data reference.
   NEW_STMT_LIST: Must be initialized to NULL_TREE or a statement list.
   OFFSET: Optional. If supplied, it is be added to the initial address.
   LOOP:    Specify relative to which loop-nest should the address be computed.
            For example, when the dataref is in an inner-loop nested in an
            outer-loop that is now being vectorized, LOOP can be either the
            outer-loop, or the inner-loop.  The first memory location accessed
            by the following dataref ('in' points to short):

                for (i=0; i<N; i++)
                   for (j=0; j<M; j++)
                     s += in[i+j]

            is as follows:
            if LOOP=i_loop:     &in             (relative to i_loop)
            if LOOP=j_loop:     &in+i*2B        (relative to j_loop)
   BYTE_OFFSET: Optional, defaulted to NULL.  If supplied, it is added to the
            initial address.  Unlike OFFSET, which is number of elements to
            be added, BYTE_OFFSET is measured in bytes.

   Output:
   1. Return an SSA_NAME whose value is the address of the memory location of
      the first vector of the data reference.
   2. If new_stmt_list is not NULL_TREE after return then the caller must insert
      these statement(s) which define the returned SSA_NAME.

   FORNOW: We are only handling array accesses with step 1.  */

tree
vect_create_addr_base_for_vector_ref (gimple *stmt,
                                      gimple_seq *new_stmt_list,
                                      tree offset,
                                      struct loop *loop,
                                      tree byte_offset)
{
  stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
  struct data_reference *dr = STMT_VINFO_DATA_REF (stmt_info);
  tree data_ref_base;
  const char *base_name;
  tree addr_base;
  tree dest;
  gimple_seq seq = NULL;
  tree base_offset;
  tree init;
  tree vect_ptr_type;
  tree step = TYPE_SIZE_UNIT (TREE_TYPE (DR_REF (dr)));
  loop_vec_info loop_vinfo = STMT_VINFO_LOOP_VINFO (stmt_info);

  if (loop_vinfo && loop && loop != (gimple_bb (stmt))->loop_father)
    {
      struct loop *outer_loop = LOOP_VINFO_LOOP (loop_vinfo);

      gcc_assert (nested_in_vect_loop_p (outer_loop, stmt));

      data_ref_base = unshare_expr (STMT_VINFO_DR_BASE_ADDRESS (stmt_info));
      base_offset = unshare_expr (STMT_VINFO_DR_OFFSET (stmt_info));
      init = unshare_expr (STMT_VINFO_DR_INIT (stmt_info));
    }
  else
    {
      data_ref_base = unshare_expr (DR_BASE_ADDRESS (dr));
      base_offset = unshare_expr (DR_OFFSET (dr));
      init = unshare_expr (DR_INIT (dr));
    }

  if (loop_vinfo)
    base_name = get_name (data_ref_base);
  else
    {
      base_offset = ssize_int (0);
      init = ssize_int (0);
      base_name = get_name (DR_REF (dr));
    }

  /* Create base_offset */
  base_offset = size_binop (PLUS_EXPR,
                            fold_convert (sizetype, base_offset),
                            fold_convert (sizetype, init));

  if (offset)
    {
      offset = fold_build2 (MULT_EXPR, sizetype,
                            fold_convert (sizetype, offset), step);
      base_offset = fold_build2 (PLUS_EXPR, sizetype,
                                 base_offset, offset);
    }
  if (byte_offset)
    {
      byte_offset = fold_convert (sizetype, byte_offset);
      base_offset = fold_build2 (PLUS_EXPR, sizetype,
                                 base_offset, byte_offset);
    }

  /* base + base_offset */
  if (loop_vinfo)
    addr_base = fold_build_pointer_plus (data_ref_base, base_offset);
  else
    {
      addr_base = build1 (ADDR_EXPR,
                          build_pointer_type (TREE_TYPE (DR_REF (dr))),
                          unshare_expr (DR_REF (dr)));
    }

  vect_ptr_type = build_pointer_type (STMT_VINFO_VECTYPE (stmt_info));
  dest = vect_get_new_vect_var (vect_ptr_type, vect_pointer_var, base_name);
  addr_base = force_gimple_operand (addr_base, &seq, true, dest);
  gimple_seq_add_seq (new_stmt_list, seq);

  if (DR_PTR_INFO (dr)
      && TREE_CODE (addr_base) == SSA_NAME
      && !SSA_NAME_PTR_INFO (addr_base))
    {
      vect_duplicate_ssa_name_ptr_info (addr_base, dr, stmt_info);
      if (offset || byte_offset)
        mark_ptr_info_alignment_unknown (SSA_NAME_PTR_INFO (addr_base));
    }

  if (dump_enabled_p ())
    {
      dump_printf_loc (MSG_NOTE, vect_location, "created ");
      dump_generic_expr (MSG_NOTE, TDF_SLIM, addr_base);
      dump_printf (MSG_NOTE, "\n");
    }

  return addr_base;
}


/* Function vect_create_data_ref_ptr.

   Create a new pointer-to-AGGR_TYPE variable (ap), that points to the first
   location accessed in the loop by STMT, along with the def-use update
   chain to appropriately advance the pointer through the loop iterations.
   Also set aliasing information for the pointer.  This pointer is used by
   the callers to this function to create a memory reference expression for
   vector load/store access.

   Input:
   1. STMT: a stmt that references memory. Expected to be of the form
         GIMPLE_ASSIGN <name, data-ref> or
         GIMPLE_ASSIGN <data-ref, name>.
   2. AGGR_TYPE: the type of the reference, which should be either a vector
        or an array.
   3. AT_LOOP: the loop where the vector memref is to be created.
   4. OFFSET (optional): an offset to be added to the initial address accessed
        by the data-ref in STMT.
   5. BSI: location where the new stmts are to be placed if there is no loop
   6. ONLY_INIT: indicate if ap is to be updated in the loop, or remain
        pointing to the initial address.
   7. BYTE_OFFSET (optional, defaults to NULL): a byte offset to be added
        to the initial address accessed by the data-ref in STMT.  This is
        similar to OFFSET, but OFFSET is counted in elements, while BYTE_OFFSET
        in bytes.

   Output:
   1. Declare a new ptr to vector_type, and have it point to the base of the
      data reference (initial addressed accessed by the data reference).
      For example, for vector of type V8HI, the following code is generated:

      v8hi *ap;
      ap = (v8hi *)initial_address;

      if OFFSET is not supplied:
         initial_address = &a[init];
      if OFFSET is supplied:
         initial_address = &a[init + OFFSET];
      if BYTE_OFFSET is supplied:
         initial_address = &a[init] + BYTE_OFFSET;

      Return the initial_address in INITIAL_ADDRESS.

   2. If ONLY_INIT is true, just return the initial pointer.  Otherwise, also
      update the pointer in each iteration of the loop.

      Return the increment stmt that updates the pointer in PTR_INCR.

   3. Set INV_P to true if the access pattern of the data reference in the
      vectorized loop is invariant.  Set it to false otherwise.

   4. Return the pointer.  */

tree
vect_create_data_ref_ptr (gimple *stmt, tree aggr_type, struct loop *at_loop,
                          tree offset, tree *initial_address,
                          gimple_stmt_iterator *gsi, gimple **ptr_incr,
                          bool only_init, bool *inv_p, tree byte_offset)
{
  const char *base_name;
  stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
  loop_vec_info loop_vinfo = STMT_VINFO_LOOP_VINFO (stmt_info);
  struct loop *loop = NULL;
  bool nested_in_vect_loop = false;
  struct loop *containing_loop = NULL;
  tree aggr_ptr_type;
  tree aggr_ptr;
  tree new_temp;
  gimple_seq new_stmt_list = NULL;
  edge pe = NULL;
  basic_block new_bb;
  tree aggr_ptr_init;
  struct data_reference *dr = STMT_VINFO_DATA_REF (stmt_info);
  tree aptr;
  gimple_stmt_iterator incr_gsi;
  bool insert_after;
  tree indx_before_incr, indx_after_incr;
  gimple *incr;
  tree step;
  bb_vec_info bb_vinfo = STMT_VINFO_BB_VINFO (stmt_info);

  gcc_assert (TREE_CODE (aggr_type) == ARRAY_TYPE
              || TREE_CODE (aggr_type) == VECTOR_TYPE);

  if (loop_vinfo)
    {
      loop = LOOP_VINFO_LOOP (loop_vinfo);
      nested_in_vect_loop = nested_in_vect_loop_p (loop, stmt);
      containing_loop = (gimple_bb (stmt))->loop_father;
      pe = loop_preheader_edge (loop);
    }
  else
    {
      gcc_assert (bb_vinfo);
      only_init = true;
      *ptr_incr = NULL;
    }

  /* Check the step (evolution) of the load in LOOP, and record
     whether it's invariant.  */
  if (nested_in_vect_loop)
    step = STMT_VINFO_DR_STEP (stmt_info);
  else
    step = DR_STEP (STMT_VINFO_DATA_REF (stmt_info));

  if (integer_zerop (step))
    *inv_p = true;
  else
    *inv_p = false;

  /* Create an expression for the first address accessed by this load
     in LOOP.  */
  base_name = get_name (DR_BASE_ADDRESS (dr));

  if (dump_enabled_p ())
    {
      tree dr_base_type = TREE_TYPE (DR_BASE_OBJECT (dr));
      dump_printf_loc (MSG_NOTE, vect_location,
                       "create %s-pointer variable to type: ",
                       get_tree_code_name (TREE_CODE (aggr_type)));
      dump_generic_expr (MSG_NOTE, TDF_SLIM, aggr_type);
      if (TREE_CODE (dr_base_type) == ARRAY_TYPE)
        dump_printf (MSG_NOTE, "  vectorizing an array ref: ");
      else if (TREE_CODE (dr_base_type) == VECTOR_TYPE)
        dump_printf (MSG_NOTE, "  vectorizing a vector ref: ");
      else if (TREE_CODE (dr_base_type) == RECORD_TYPE)
        dump_printf (MSG_NOTE, "  vectorizing a record based array ref: ");
      else
        dump_printf (MSG_NOTE, "  vectorizing a pointer ref: ");
      dump_generic_expr (MSG_NOTE, TDF_SLIM, DR_BASE_OBJECT (dr));
      dump_printf (MSG_NOTE, "\n");
    }

  /* (1) Create the new aggregate-pointer variable.
     Vector and array types inherit the alias set of their component
     type by default so we need to use a ref-all pointer if the data
     reference does not conflict with the created aggregated data
     reference because it is not addressable.  */
  bool need_ref_all = false;
  if (!alias_sets_conflict_p (get_alias_set (aggr_type),
                              get_alias_set (DR_REF (dr))))
    need_ref_all = true;
  /* Likewise for any of the data references in the stmt group.  */
  else if (STMT_VINFO_GROUP_SIZE (stmt_info) > 1)
    {
      gimple *orig_stmt = STMT_VINFO_GROUP_FIRST_ELEMENT (stmt_info);
      do
        {
          stmt_vec_info sinfo = vinfo_for_stmt (orig_stmt);
          struct data_reference *sdr = STMT_VINFO_DATA_REF (sinfo);
          if (!alias_sets_conflict_p (get_alias_set (aggr_type),
                                      get_alias_set (DR_REF (sdr))))
            {
              need_ref_all = true;
              break;
            }
          orig_stmt = STMT_VINFO_GROUP_NEXT_ELEMENT (sinfo);
        }
      while (orig_stmt);
    }
  aggr_ptr_type = build_pointer_type_for_mode (aggr_type, ptr_mode,
                                               need_ref_all);
  aggr_ptr = vect_get_new_vect_var (aggr_ptr_type, vect_pointer_var, base_name);


  /* Note: If the dataref is in an inner-loop nested in LOOP, and we are
     vectorizing LOOP (i.e., outer-loop vectorization), we need to create two
     def-use update cycles for the pointer: one relative to the outer-loop
     (LOOP), which is what steps (3) and (4) below do.  The other is relative
     to the inner-loop (which is the inner-most loop containing the dataref),
     and this is done be step (5) below.

     When vectorizing inner-most loops, the vectorized loop (LOOP) is also the
     inner-most loop, and so steps (3),(4) work the same, and step (5) is
     redundant.  Steps (3),(4) create the following:

        vp0 = &base_addr;
        LOOP:   vp1 = phi(vp0,vp2)
                ...
                ...
                vp2 = vp1 + step
                goto LOOP

     If there is an inner-loop nested in loop, then step (5) will also be
     applied, and an additional update in the inner-loop will be created:

        vp0 = &base_addr;
        LOOP:   vp1 = phi(vp0,vp2)
                ...
        inner:     vp3 = phi(vp1,vp4)
                   vp4 = vp3 + inner_step
                   if () goto inner
                ...
                vp2 = vp1 + step
                if () goto LOOP   */

  /* (2) Calculate the initial address of the aggregate-pointer, and set
     the aggregate-pointer to point to it before the loop.  */

  /* Create: (&(base[init_val+offset]+byte_offset) in the loop preheader.  */

  new_temp = vect_create_addr_base_for_vector_ref (stmt, &new_stmt_list,
                                                   offset, loop, byte_offset);
  if (new_stmt_list)
    {
      if (pe)
        {
          new_bb = gsi_insert_seq_on_edge_immediate (pe, new_stmt_list);
          gcc_assert (!new_bb);
        }
      else
        gsi_insert_seq_before (gsi, new_stmt_list, GSI_SAME_STMT);
    }

  *initial_address = new_temp;
  aggr_ptr_init = new_temp;

  /* (3) Handle the updating of the aggregate-pointer inside the loop.
     This is needed when ONLY_INIT is false, and also when AT_LOOP is the
     inner-loop nested in LOOP (during outer-loop vectorization).  */

  /* No update in loop is required.  */
  if (only_init && (!loop_vinfo || at_loop == loop))
    aptr = aggr_ptr_init;
  else
    {
      /* The step of the aggregate pointer is the type size.  */
      tree iv_step = TYPE_SIZE_UNIT (aggr_type);
      /* One exception to the above is when the scalar step of the load in
         LOOP is zero. In this case the step here is also zero.  */
      if (*inv_p)
        iv_step = size_zero_node;
      else if (tree_int_cst_sgn (step) == -1)
        iv_step = fold_build1 (NEGATE_EXPR, TREE_TYPE (iv_step), iv_step);

      standard_iv_increment_position (loop, &incr_gsi, &insert_after);

      create_iv (aggr_ptr_init,
                 fold_convert (aggr_ptr_type, iv_step),
                 aggr_ptr, loop, &incr_gsi, insert_after,
                 &indx_before_incr, &indx_after_incr);
      incr = gsi_stmt (incr_gsi);
      set_vinfo_for_stmt (incr, new_stmt_vec_info (incr, loop_vinfo));

      /* Copy the points-to information if it exists. */
      if (DR_PTR_INFO (dr))
        {
          vect_duplicate_ssa_name_ptr_info (indx_before_incr, dr, stmt_info);
          vect_duplicate_ssa_name_ptr_info (indx_after_incr, dr, stmt_info);
        }
      if (ptr_incr)
        *ptr_incr = incr;

      aptr = indx_before_incr;
    }

  if (!nested_in_vect_loop || only_init)
    return aptr;


  /* (4) Handle the updating of the aggregate-pointer inside the inner-loop
     nested in LOOP, if exists.  */

  gcc_assert (nested_in_vect_loop);
  if (!only_init)
    {
      standard_iv_increment_position (containing_loop, &incr_gsi,
                                      &insert_after);
      create_iv (aptr, fold_convert (aggr_ptr_type, DR_STEP (dr)), aggr_ptr,
                 containing_loop, &incr_gsi, insert_after, &indx_before_incr,
                 &indx_after_incr);
      incr = gsi_stmt (incr_gsi);
      set_vinfo_for_stmt (incr, new_stmt_vec_info (incr, loop_vinfo));

      /* Copy the points-to information if it exists. */
      if (DR_PTR_INFO (dr))
        {
          vect_duplicate_ssa_name_ptr_info (indx_before_incr, dr, stmt_info);
          vect_duplicate_ssa_name_ptr_info (indx_after_incr, dr, stmt_info);
        }
      if (ptr_incr)
        *ptr_incr = incr;

      return indx_before_incr;
    }
  else
    gcc_unreachable ();
}


/* Function bump_vector_ptr

   Increment a pointer (to a vector type) by vector-size. If requested,
   i.e. if PTR-INCR is given, then also connect the new increment stmt
   to the existing def-use update-chain of the pointer, by modifying
   the PTR_INCR as illustrated below:

   The pointer def-use update-chain before this function:
                        DATAREF_PTR = phi (p_0, p_2)
                        ....
        PTR_INCR:       p_2 = DATAREF_PTR + step

   The pointer def-use update-chain after this function:
                        DATAREF_PTR = phi (p_0, p_2)
                        ....
                        NEW_DATAREF_PTR = DATAREF_PTR + BUMP
                        ....
        PTR_INCR:       p_2 = NEW_DATAREF_PTR + step

   Input:
   DATAREF_PTR - ssa_name of a pointer (to vector type) that is being updated
                 in the loop.
   PTR_INCR - optional. The stmt that updates the pointer in each iteration of
              the loop.  The increment amount across iterations is expected
              to be vector_size.
   BSI - location where the new update stmt is to be placed.
   STMT - the original scalar memory-access stmt that is being vectorized.
   BUMP - optional. The offset by which to bump the pointer. If not given,
          the offset is assumed to be vector_size.

   Output: Return NEW_DATAREF_PTR as illustrated above.

*/

tree
bump_vector_ptr (tree dataref_ptr, gimple *ptr_incr, gimple_stmt_iterator *gsi,
                 gimple *stmt, tree bump)
{
  stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
  struct data_reference *dr = STMT_VINFO_DATA_REF (stmt_info);
  tree vectype = STMT_VINFO_VECTYPE (stmt_info);
  tree update = TYPE_SIZE_UNIT (vectype);
  gassign *incr_stmt;
  ssa_op_iter iter;
  use_operand_p use_p;
  tree new_dataref_ptr;

  if (bump)
    update = bump;

  if (TREE_CODE (dataref_ptr) == SSA_NAME)
    new_dataref_ptr = copy_ssa_name (dataref_ptr);
  else
    new_dataref_ptr = make_ssa_name (TREE_TYPE (dataref_ptr));
  incr_stmt = gimple_build_assign (new_dataref_ptr, POINTER_PLUS_EXPR,
                                   dataref_ptr, update);
  vect_finish_stmt_generation (stmt, incr_stmt, gsi);

  /* Copy the points-to information if it exists. */
  if (DR_PTR_INFO (dr))
    {
      duplicate_ssa_name_ptr_info (new_dataref_ptr, DR_PTR_INFO (dr));
      mark_ptr_info_alignment_unknown (SSA_NAME_PTR_INFO (new_dataref_ptr));
    }

  if (!ptr_incr)
    return new_dataref_ptr;

  /* Update the vector-pointer's cross-iteration increment.  */
  FOR_EACH_SSA_USE_OPERAND (use_p, ptr_incr, iter, SSA_OP_USE)
    {
      tree use = USE_FROM_PTR (use_p);

      if (use == dataref_ptr)
        SET_USE (use_p, new_dataref_ptr);
      else
        gcc_assert (tree_int_cst_compare (use, update) == 0);
    }

  return new_dataref_ptr;
}


/* Function vect_create_destination_var.

   Create a new temporary of type VECTYPE.  */

tree
vect_create_destination_var (tree scalar_dest, tree vectype)
{
  tree vec_dest;
  const char *name;
  char *new_name;
  tree type;
  enum vect_var_kind kind;

  kind = vectype
    ? VECTOR_BOOLEAN_TYPE_P (vectype)
    ? vect_mask_var
    : vect_simple_var
    : vect_scalar_var;
  type = vectype ? vectype : TREE_TYPE (scalar_dest);

  gcc_assert (TREE_CODE (scalar_dest) == SSA_NAME);

  name = get_name (scalar_dest);
  if (name)
    new_name = xasprintf ("%s_%u", name, SSA_NAME_VERSION (scalar_dest));
  else
    new_name = xasprintf ("_%u", SSA_NAME_VERSION (scalar_dest));
  vec_dest = vect_get_new_vect_var (type, kind, new_name);
  free (new_name);

  return vec_dest;
}

/* Function vect_grouped_store_supported.

   Returns TRUE if interleave high and interleave low permutations
   are supported, and FALSE otherwise.  */

bool
vect_grouped_store_supported (tree vectype, unsigned HOST_WIDE_INT count)
{
  machine_mode mode = TYPE_MODE (vectype);

  /* vect_permute_store_chain requires the group size to be equal to 3 or
     be a power of two.  */
  if (count != 3 && exact_log2 (count) == -1)
    {
      if (dump_enabled_p ())
        dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                         "the size of the group of accesses"
                         " is not a power of 2 or not eqaul to 3\n");
      return false;
    }

  /* Check that the permutation is supported.  */
  if (VECTOR_MODE_P (mode))
    {
      unsigned int i, nelt = GET_MODE_NUNITS (mode);
      unsigned char *sel = XALLOCAVEC (unsigned char, nelt);

      if (count == 3)
        {
          unsigned int j0 = 0, j1 = 0, j2 = 0;
          unsigned int i, j;

          for (j = 0; j < 3; j++)
            {
              int nelt0 = ((3 - j) * nelt) % 3;
              int nelt1 = ((3 - j) * nelt + 1) % 3;
              int nelt2 = ((3 - j) * nelt + 2) % 3;
              for (i = 0; i < nelt; i++)
                {
                  if (3 * i + nelt0 < nelt)
                    sel[3 * i + nelt0] = j0++;
                  if (3 * i + nelt1 < nelt)
                    sel[3 * i + nelt1] = nelt + j1++;
                  if (3 * i + nelt2 < nelt)
                    sel[3 * i + nelt2] = 0;
                }
              if (!can_vec_perm_p (mode, false, sel))
                {
                  if (dump_enabled_p ())
                    dump_printf (MSG_MISSED_OPTIMIZATION,
                                 "permutaion op not supported by target.\n");
                  return false;
                }

              for (i = 0; i < nelt; i++)
                {
                  if (3 * i + nelt0 < nelt)
                    sel[3 * i + nelt0] = 3 * i + nelt0;
                  if (3 * i + nelt1 < nelt)
                    sel[3 * i + nelt1] = 3 * i + nelt1;
                  if (3 * i + nelt2 < nelt)
                    sel[3 * i + nelt2] = nelt + j2++;
                }
              if (!can_vec_perm_p (mode, false, sel))
                {
                  if (dump_enabled_p ())
                    dump_printf (MSG_MISSED_OPTIMIZATION,
                                 "permutaion op not supported by target.\n");
                  return false;
                }
            }
          return true;
        }
      else
        {
          /* If length is not equal to 3 then only power of 2 is supported.  */
          gcc_assert (exact_log2 (count) != -1);

          for (i = 0; i < nelt / 2; i++)
            {
              sel[i * 2] = i;
              sel[i * 2 + 1] = i + nelt;
            }
            if (can_vec_perm_p (mode, false, sel))
              {
                for (i = 0; i < nelt; i++)
                  sel[i] += nelt / 2;
                if (can_vec_perm_p (mode, false, sel))
                  return true;
              }
        }
    }

  if (dump_enabled_p ())
    dump_printf (MSG_MISSED_OPTIMIZATION,
                 "permutaion op not supported by target.\n");
  return false;
}


/* Return TRUE if vec_store_lanes is available for COUNT vectors of
   type VECTYPE.  */

bool
vect_store_lanes_supported (tree vectype, unsigned HOST_WIDE_INT count)
{
  return vect_lanes_optab_supported_p ("vec_store_lanes",
                                       vec_store_lanes_optab,
                                       vectype, count);
}


/* Function vect_permute_store_chain.

   Given a chain of interleaved stores in DR_CHAIN of LENGTH that must be
   a power of 2 or equal to 3, generate interleave_high/low stmts to reorder
   the data correctly for the stores.  Return the final references for stores
   in RESULT_CHAIN.

   E.g., LENGTH is 4 and the scalar type is short, i.e., VF is 8.
   The input is 4 vectors each containing 8 elements.  We assign a number to
   each element, the input sequence is:

   1st vec:   0  1  2  3  4  5  6  7
   2nd vec:   8  9 10 11 12 13 14 15
   3rd vec:  16 17 18 19 20 21 22 23
   4th vec:  24 25 26 27 28 29 30 31

   The output sequence should be:

   1st vec:  0  8 16 24  1  9 17 25
   2nd vec:  2 10 18 26  3 11 19 27
   3rd vec:  4 12 20 28  5 13 21 30
   4th vec:  6 14 22 30  7 15 23 31

   i.e., we interleave the contents of the four vectors in their order.

   We use interleave_high/low instructions to create such output.  The input of
   each interleave_high/low operation is two vectors:
   1st vec    2nd vec
   0 1 2 3    4 5 6 7
   the even elements of the result vector are obtained left-to-right from the
   high/low elements of the first vector.  The odd elements of the result are
   obtained left-to-right from the high/low elements of the second vector.
   The output of interleave_high will be:   0 4 1 5
   and of interleave_low:                   2 6 3 7


   The permutation is done in log LENGTH stages.  In each stage interleave_high
   and interleave_low stmts are created for each pair of vectors in DR_CHAIN,
   where the first argument is taken from the first half of DR_CHAIN and the
   second argument from it's second half.
   In our example,

   I1: interleave_high (1st vec, 3rd vec)
   I2: interleave_low (1st vec, 3rd vec)
   I3: interleave_high (2nd vec, 4th vec)
   I4: interleave_low (2nd vec, 4th vec)

   The output for the first stage is:

   I1:  0 16  1 17  2 18  3 19
   I2:  4 20  5 21  6 22  7 23
   I3:  8 24  9 25 10 26 11 27
   I4: 12 28 13 29 14 30 15 31

   The output of the second stage, i.e. the final result is:

   I1:  0  8 16 24  1  9 17 25
   I2:  2 10 18 26  3 11 19 27
   I3:  4 12 20 28  5 13 21 30
   I4:  6 14 22 30  7 15 23 31.  */

void
vect_permute_store_chain (vec<tree> dr_chain,
                          unsigned int length,
                          gimple *stmt,
                          gimple_stmt_iterator *gsi,
                          vec<tree> *result_chain)
{
  tree vect1, vect2, high, low;
  gimple *perm_stmt;
  tree vectype = STMT_VINFO_VECTYPE (vinfo_for_stmt (stmt));
  tree perm_mask_low, perm_mask_high;
  tree data_ref;
  tree perm3_mask_low, perm3_mask_high;
  unsigned int i, n, log_length = exact_log2 (length);
  unsigned int j, nelt = TYPE_VECTOR_SUBPARTS (vectype);
  unsigned char *sel = XALLOCAVEC (unsigned char, nelt);

  result_chain->quick_grow (length);
  memcpy (result_chain->address (), dr_chain.address (),
          length * sizeof (tree));

  if (length == 3)
    {
      unsigned int j0 = 0, j1 = 0, j2 = 0;

      for (j = 0; j < 3; j++)
        {
          int nelt0 = ((3 - j) * nelt) % 3;
          int nelt1 = ((3 - j) * nelt + 1) % 3;
          int nelt2 = ((3 - j) * nelt + 2) % 3;

          for (i = 0; i < nelt; i++)
            {
              if (3 * i + nelt0 < nelt)
                sel[3 * i + nelt0] = j0++;
              if (3 * i + nelt1 < nelt)
                sel[3 * i + nelt1] = nelt + j1++;
              if (3 * i + nelt2 < nelt)
                sel[3 * i + nelt2] = 0;
            }
          perm3_mask_low = vect_gen_perm_mask_checked (vectype, sel);

          for (i = 0; i < nelt; i++)
            {
              if (3 * i + nelt0 < nelt)
                sel[3 * i + nelt0] = 3 * i + nelt0;
              if (3 * i + nelt1 < nelt)
                sel[3 * i + nelt1] = 3 * i + nelt1;
              if (3 * i + nelt2 < nelt)
                sel[3 * i + nelt2] = nelt + j2++;
            }
          perm3_mask_high = vect_gen_perm_mask_checked (vectype, sel);

          vect1 = dr_chain[0];
          vect2 = dr_chain[1];

          /* Create interleaving stmt:
             low = VEC_PERM_EXPR <vect1, vect2,
                                  {j, nelt, *, j + 1, nelt + j + 1, *,
                                   j + 2, nelt + j + 2, *, ...}>  */
          data_ref = make_temp_ssa_name (vectype, NULL, "vect_shuffle3_low");
          perm_stmt = gimple_build_assign (data_ref, VEC_PERM_EXPR, vect1,
                                           vect2, perm3_mask_low);
          vect_finish_stmt_generation (stmt, perm_stmt, gsi);

          vect1 = data_ref;
          vect2 = dr_chain[2];
          /* Create interleaving stmt:
             low = VEC_PERM_EXPR <vect1, vect2,
                                  {0, 1, nelt + j, 3, 4, nelt + j + 1,
                                   6, 7, nelt + j + 2, ...}>  */
          data_ref = make_temp_ssa_name (vectype, NULL, "vect_shuffle3_high");
          perm_stmt = gimple_build_assign (data_ref, VEC_PERM_EXPR, vect1,
                                           vect2, perm3_mask_high);
          vect_finish_stmt_generation (stmt, perm_stmt, gsi);
          (*result_chain)[j] = data_ref;
        }
    }
  else
    {
      /* If length is not equal to 3 then only power of 2 is supported.  */
      gcc_assert (exact_log2 (length) != -1);

      for (i = 0, n = nelt / 2; i < n; i++)
        {
          sel[i * 2] = i;
          sel[i * 2 + 1] = i + nelt;
        }
        perm_mask_high = vect_gen_perm_mask_checked (vectype, sel);

        for (i = 0; i < nelt; i++)
          sel[i] += nelt / 2;
        perm_mask_low = vect_gen_perm_mask_checked (vectype, sel);

        for (i = 0, n = log_length; i < n; i++)
          {
            for (j = 0; j < length/2; j++)
              {
                vect1 = dr_chain[j];
                vect2 = dr_chain[j+length/2];

                /* Create interleaving stmt:
                   high = VEC_PERM_EXPR <vect1, vect2, {0, nelt, 1, nelt+1,
                                                        ...}>  */
                high = make_temp_ssa_name (vectype, NULL, "vect_inter_high");
                perm_stmt = gimple_build_assign (high, VEC_PERM_EXPR, vect1,
                                                 vect2, perm_mask_high);
                vect_finish_stmt_generation (stmt, perm_stmt, gsi);
                (*result_chain)[2*j] = high;

                /* Create interleaving stmt:
                   low = VEC_PERM_EXPR <vect1, vect2,
                                        {nelt/2, nelt*3/2, nelt/2+1, nelt*3/2+1,
                                         ...}>  */
                low = make_temp_ssa_name (vectype, NULL, "vect_inter_low");
                perm_stmt = gimple_build_assign (low, VEC_PERM_EXPR, vect1,
                                                 vect2, perm_mask_low);
                vect_finish_stmt_generation (stmt, perm_stmt, gsi);
                (*result_chain)[2*j+1] = low;
              }
            memcpy (dr_chain.address (), result_chain->address (),
                    length * sizeof (tree));
          }
    }
}

/* Function vect_setup_realignment

   This function is called when vectorizing an unaligned load using
   the dr_explicit_realign[_optimized] scheme.
   This function generates the following code at the loop prolog:

      p = initial_addr;
   x  msq_init = *(floor(p));   # prolog load
      realignment_token = call target_builtin;
    loop:
   x  msq = phi (msq_init, ---)

   The stmts marked with x are generated only for the case of
   dr_explicit_realign_optimized.

   The code above sets up a new (vector) pointer, pointing to the first
   location accessed by STMT, and a "floor-aligned" load using that pointer.
   It also generates code to compute the "realignment-token" (if the relevant
   target hook was defined), and creates a phi-node at the loop-header bb
   whose arguments are the result of the prolog-load (created by this
   function) and the result of a load that takes place in the loop (to be
   created by the caller to this function).

   For the case of dr_explicit_realign_optimized:
   The caller to this function uses the phi-result (msq) to create the
   realignment code inside the loop, and sets up the missing phi argument,
   as follows:
    loop:
      msq = phi (msq_init, lsq)
      lsq = *(floor(p'));        # load in loop
      result = realign_load (msq, lsq, realignment_token);

   For the case of dr_explicit_realign:
    loop:
      msq = *(floor(p));        # load in loop
      p' = p + (VS-1);
      lsq = *(floor(p'));       # load in loop
      result = realign_load (msq, lsq, realignment_token);

   Input:
   STMT - (scalar) load stmt to be vectorized. This load accesses
          a memory location that may be unaligned.
   BSI - place where new code is to be inserted.
   ALIGNMENT_SUPPORT_SCHEME - which of the two misalignment handling schemes
                              is used.

   Output:
   REALIGNMENT_TOKEN - the result of a call to the builtin_mask_for_load
                       target hook, if defined.
   Return value - the result of the loop-header phi node.  */

tree
vect_setup_realignment (gimple *stmt, gimple_stmt_iterator *gsi,
                        tree *realignment_token,
                        enum dr_alignment_support alignment_support_scheme,
                        tree init_addr,
                        struct loop **at_loop)
{
  stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
  tree vectype = STMT_VINFO_VECTYPE (stmt_info);
  loop_vec_info loop_vinfo = STMT_VINFO_LOOP_VINFO (stmt_info);
  struct data_reference *dr = STMT_VINFO_DATA_REF (stmt_info);
  struct loop *loop = NULL;
  edge pe = NULL;
  tree scalar_dest = gimple_assign_lhs (stmt);
  tree vec_dest;
  gimple *inc;
  tree ptr;
  tree data_ref;
  basic_block new_bb;
  tree msq_init = NULL_TREE;
  tree new_temp;
  gphi *phi_stmt;
  tree msq = NULL_TREE;
  gimple_seq stmts = NULL;
  bool inv_p;
  bool compute_in_loop = false;
  bool nested_in_vect_loop = false;
  struct loop *containing_loop = (gimple_bb (stmt))->loop_father;
  struct loop *loop_for_initial_load = NULL;

  if (loop_vinfo)
    {
      loop = LOOP_VINFO_LOOP (loop_vinfo);
      nested_in_vect_loop = nested_in_vect_loop_p (loop, stmt);
    }

  gcc_assert (alignment_support_scheme == dr_explicit_realign
              || alignment_support_scheme == dr_explicit_realign_optimized);

  /* We need to generate three things:
     1. the misalignment computation
     2. the extra vector load (for the optimized realignment scheme).
     3. the phi node for the two vectors from which the realignment is
      done (for the optimized realignment scheme).  */

  /* 1. Determine where to generate the misalignment computation.

     If INIT_ADDR is NULL_TREE, this indicates that the misalignment
     calculation will be generated by this function, outside the loop (in the
     preheader).  Otherwise, INIT_ADDR had already been computed for us by the
     caller, inside the loop.

     Background: If the misalignment remains fixed throughout the iterations of
     the loop, then both realignment schemes are applicable, and also the
     misalignment computation can be done outside LOOP.  This is because we are
     vectorizing LOOP, and so the memory accesses in LOOP advance in steps that
     are a multiple of VS (the Vector Size), and therefore the misalignment in
     different vectorized LOOP iterations is always the same.
     The problem arises only if the memory access is in an inner-loop nested
     inside LOOP, which is now being vectorized using outer-loop vectorization.
     This is the only case when the misalignment of the memory access may not
     remain fixed throughout the iterations of the inner-loop (as explained in
     detail in vect_supportable_dr_alignment).  In this case, not only is the
     optimized realignment scheme not applicable, but also the misalignment
     computation (and generation of the realignment token that is passed to
     REALIGN_LOAD) have to be done inside the loop.

     In short, INIT_ADDR indicates whether we are in a COMPUTE_IN_LOOP mode
     or not, which in turn determines if the misalignment is computed inside
     the inner-loop, or outside LOOP.  */

  if (init_addr != NULL_TREE || !loop_vinfo)
    {
      compute_in_loop = true;
      gcc_assert (alignment_support_scheme == dr_explicit_realign);
    }


  /* 2. Determine where to generate the extra vector load.

     For the optimized realignment scheme, instead of generating two vector
     loads in each iteration, we generate a single extra vector load in the
     preheader of the loop, and in each iteration reuse the result of the
     vector load from the previous iteration.  In case the memory access is in
     an inner-loop nested inside LOOP, which is now being vectorized using
     outer-loop vectorization, we need to determine whether this initial vector
     load should be generated at the preheader of the inner-loop, or can be
     generated at the preheader of LOOP.  If the memory access has no evolution
     in LOOP, it can be generated in the preheader of LOOP. Otherwise, it has
     to be generated inside LOOP (in the preheader of the inner-loop).  */

  if (nested_in_vect_loop)
    {
      tree outerloop_step = STMT_VINFO_DR_STEP (stmt_info);
      bool invariant_in_outerloop =
            (tree_int_cst_compare (outerloop_step, size_zero_node) == 0);
      loop_for_initial_load = (invariant_in_outerloop ? loop : loop->inner);
    }
  else
    loop_for_initial_load = loop;
  if (at_loop)
    *at_loop = loop_for_initial_load;

  if (loop_for_initial_load)
    pe = loop_preheader_edge (loop_for_initial_load);

  /* 3. For the case of the optimized realignment, create the first vector
      load at the loop preheader.  */

  if (alignment_support_scheme == dr_explicit_realign_optimized)
    {
      /* Create msq_init = *(floor(p1)) in the loop preheader  */
      gassign *new_stmt;

      gcc_assert (!compute_in_loop);
      vec_dest = vect_create_destination_var (scalar_dest, vectype);
      ptr = vect_create_data_ref_ptr (stmt, vectype, loop_for_initial_load,
                                      NULL_TREE, &init_addr, NULL, &inc,
                                      true, &inv_p);
      if (TREE_CODE (ptr) == SSA_NAME)
        new_temp = copy_ssa_name (ptr);
      else
        new_temp = make_ssa_name (TREE_TYPE (ptr));
      new_stmt = gimple_build_assign
                   (new_temp, BIT_AND_EXPR, ptr,
                    build_int_cst (TREE_TYPE (ptr),
                                   -(HOST_WIDE_INT)TYPE_ALIGN_UNIT (vectype)));
      new_bb = gsi_insert_on_edge_immediate (pe, new_stmt);
      gcc_assert (!new_bb);
      data_ref
        = build2 (MEM_REF, TREE_TYPE (vec_dest), new_temp,
                  build_int_cst (reference_alias_ptr_type (DR_REF (dr)), 0));
      new_stmt = gimple_build_assign (vec_dest, data_ref);
      new_temp = make_ssa_name (vec_dest, new_stmt);
      gimple_assign_set_lhs (new_stmt, new_temp);
      if (pe)
        {
          new_bb = gsi_insert_on_edge_immediate (pe, new_stmt);
          gcc_assert (!new_bb);
        }
      else
         gsi_insert_before (gsi, new_stmt, GSI_SAME_STMT);

      msq_init = gimple_assign_lhs (new_stmt);
    }

  /* 4. Create realignment token using a target builtin, if available.
      It is done either inside the containing loop, or before LOOP (as
      determined above).  */

  if (targetm.vectorize.builtin_mask_for_load)
    {
      gcall *new_stmt;
      tree builtin_decl;

      /* Compute INIT_ADDR - the initial addressed accessed by this memref.  */
      if (!init_addr)
        {
          /* Generate the INIT_ADDR computation outside LOOP.  */
          init_addr = vect_create_addr_base_for_vector_ref (stmt, &stmts,
                                                        NULL_TREE, loop);
          if (loop)
            {
              pe = loop_preheader_edge (loop);
              new_bb = gsi_insert_seq_on_edge_immediate (pe, stmts);
              gcc_assert (!new_bb);
            }
          else
             gsi_insert_seq_before (gsi, stmts, GSI_SAME_STMT);
        }

      builtin_decl = targetm.vectorize.builtin_mask_for_load ();
      new_stmt = gimple_build_call (builtin_decl, 1, init_addr);
      vec_dest =
        vect_create_destination_var (scalar_dest,
                                     gimple_call_return_type (new_stmt));
      new_temp = make_ssa_name (vec_dest, new_stmt);
      gimple_call_set_lhs (new_stmt, new_temp);

      if (compute_in_loop)
        gsi_insert_before (gsi, new_stmt, GSI_SAME_STMT);
      else
        {
          /* Generate the misalignment computation outside LOOP.  */
          pe = loop_preheader_edge (loop);
          new_bb = gsi_insert_on_edge_immediate (pe, new_stmt);
          gcc_assert (!new_bb);
        }

      *realignment_token = gimple_call_lhs (new_stmt);

      /* The result of the CALL_EXPR to this builtin is determined from
         the value of the parameter and no global variables are touched
         which makes the builtin a "const" function.  Requiring the
         builtin to have the "const" attribute makes it unnecessary
         to call mark_call_clobbered.  */
      gcc_assert (TREE_READONLY (builtin_decl));
    }

  if (alignment_support_scheme == dr_explicit_realign)
    return msq;

  gcc_assert (!compute_in_loop);
  gcc_assert (alignment_support_scheme == dr_explicit_realign_optimized);


  /* 5. Create msq = phi <msq_init, lsq> in loop  */

  pe = loop_preheader_edge (containing_loop);
  vec_dest = vect_create_destination_var (scalar_dest, vectype);
  msq = make_ssa_name (vec_dest);
  phi_stmt = create_phi_node (msq, containing_loop->header);
  add_phi_arg (phi_stmt, msq_init, pe, UNKNOWN_LOCATION);

  return msq;
}


/* Function vect_grouped_load_supported.

   Returns TRUE if even and odd permutations are supported,
   and FALSE otherwise.  */

bool
vect_grouped_load_supported (tree vectype, unsigned HOST_WIDE_INT count)
{
  machine_mode mode = TYPE_MODE (vectype);

  /* vect_permute_load_chain requires the group size to be equal to 3 or
     be a power of two.  */
  if (count != 3 && exact_log2 (count) == -1)
    {
      if (dump_enabled_p ())
        dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                         "the size of the group of accesses"
                         " is not a power of 2 or not equal to 3\n");
      return false;
    }

  /* Check that the permutation is supported.  */
  if (VECTOR_MODE_P (mode))
    {
      unsigned int i, j, nelt = GET_MODE_NUNITS (mode);
      unsigned char *sel = XALLOCAVEC (unsigned char, nelt);

      if (count == 3)
        {
          unsigned int k;
          for (k = 0; k < 3; k++)
            {
              for (i = 0; i < nelt; i++)
                if (3 * i + k < 2 * nelt)
                  sel[i] = 3 * i + k;
                else
                  sel[i] = 0;
              if (!can_vec_perm_p (mode, false, sel))
                {
                  if (dump_enabled_p ())
                    dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                                     "shuffle of 3 loads is not supported by"
                                     " target\n");
                  return false;
                }
              for (i = 0, j = 0; i < nelt; i++)
                if (3 * i + k < 2 * nelt)
                  sel[i] = i;
                else
                  sel[i] = nelt + ((nelt + k) % 3) + 3 * (j++);
              if (!can_vec_perm_p (mode, false, sel))
                {
                  if (dump_enabled_p ())
                    dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                                     "shuffle of 3 loads is not supported by"
                                     " target\n");
                  return false;
                }
            }
          return true;
        }
      else
        {
          /* If length is not equal to 3 then only power of 2 is supported.  */
          gcc_assert (exact_log2 (count) != -1);
          for (i = 0; i < nelt; i++)
            sel[i] = i * 2;
          if (can_vec_perm_p (mode, false, sel))
            {
              for (i = 0; i < nelt; i++)
                sel[i] = i * 2 + 1;
              if (can_vec_perm_p (mode, false, sel))
                return true;
            }
        }
    }

  if (dump_enabled_p ())
    dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                     "extract even/odd not supported by target\n");
  return false;
}

/* Return TRUE if vec_load_lanes is available for COUNT vectors of
   type VECTYPE.  */

bool
vect_load_lanes_supported (tree vectype, unsigned HOST_WIDE_INT count)
{
  return vect_lanes_optab_supported_p ("vec_load_lanes",
                                       vec_load_lanes_optab,
                                       vectype, count);
}

/* Function vect_permute_load_chain.

   Given a chain of interleaved loads in DR_CHAIN of LENGTH that must be
   a power of 2 or equal to 3, generate extract_even/odd stmts to reorder
   the input data correctly.  Return the final references for loads in
   RESULT_CHAIN.

   E.g., LENGTH is 4 and the scalar type is short, i.e., VF is 8.
   The input is 4 vectors each containing 8 elements. We assign a number to each
   element, the input sequence is:

   1st vec:   0  1  2  3  4  5  6  7
   2nd vec:   8  9 10 11 12 13 14 15
   3rd vec:  16 17 18 19 20 21 22 23
   4th vec:  24 25 26 27 28 29 30 31

   The output sequence should be:

   1st vec:  0 4  8 12 16 20 24 28
   2nd vec:  1 5  9 13 17 21 25 29
   3rd vec:  2 6 10 14 18 22 26 30
   4th vec:  3 7 11 15 19 23 27 31

   i.e., the first output vector should contain the first elements of each
   interleaving group, etc.

   We use extract_even/odd instructions to create such output.  The input of
   each extract_even/odd operation is two vectors
   1st vec    2nd vec
   0 1 2 3    4 5 6 7

   and the output is the vector of extracted even/odd elements.  The output of
   extract_even will be:   0 2 4 6
   and of extract_odd:     1 3 5 7


   The permutation is done in log LENGTH stages.  In each stage extract_even
   and extract_odd stmts are created for each pair of vectors in DR_CHAIN in
   their order.  In our example,

   E1: extract_even (1st vec, 2nd vec)
   E2: extract_odd (1st vec, 2nd vec)
   E3: extract_even (3rd vec, 4th vec)
   E4: extract_odd (3rd vec, 4th vec)

   The output for the first stage will be:

   E1:  0  2  4  6  8 10 12 14
   E2:  1  3  5  7  9 11 13 15
   E3: 16 18 20 22 24 26 28 30
   E4: 17 19 21 23 25 27 29 31

   In order to proceed and create the correct sequence for the next stage (or
   for the correct output, if the second stage is the last one, as in our
   example), we first put the output of extract_even operation and then the
   output of extract_odd in RESULT_CHAIN (which is then copied to DR_CHAIN).
   The input for the second stage is:

   1st vec (E1):  0  2  4  6  8 10 12 14
   2nd vec (E3): 16 18 20 22 24 26 28 30
   3rd vec (E2):  1  3  5  7  9 11 13 15
   4th vec (E4): 17 19 21 23 25 27 29 31

   The output of the second stage:

   E1: 0 4  8 12 16 20 24 28
   E2: 2 6 10 14 18 22 26 30
   E3: 1 5  9 13 17 21 25 29
   E4: 3 7 11 15 19 23 27 31

   And RESULT_CHAIN after reordering:

   1st vec (E1):  0 4  8 12 16 20 24 28
   2nd vec (E3):  1 5  9 13 17 21 25 29
   3rd vec (E2):  2 6 10 14 18 22 26 30
   4th vec (E4):  3 7 11 15 19 23 27 31.  */

static void
vect_permute_load_chain (vec<tree> dr_chain,
                         unsigned int length,
                         gimple *stmt,
                         gimple_stmt_iterator *gsi,
                         vec<tree> *result_chain)
{
  tree data_ref, first_vect, second_vect;
  tree perm_mask_even, perm_mask_odd;
  tree perm3_mask_low, perm3_mask_high;
  gimple *perm_stmt;
  tree vectype = STMT_VINFO_VECTYPE (vinfo_for_stmt (stmt));
  unsigned int i, j, log_length = exact_log2 (length);
  unsigned nelt = TYPE_VECTOR_SUBPARTS (vectype);
  unsigned char *sel = XALLOCAVEC (unsigned char, nelt);

  result_chain->quick_grow (length);
  memcpy (result_chain->address (), dr_chain.address (),
          length * sizeof (tree));

  if (length == 3)
    {
      unsigned int k;

      for (k = 0; k < 3; k++)
        {
          for (i = 0; i < nelt; i++)
            if (3 * i + k < 2 * nelt)
              sel[i] = 3 * i + k;
            else
              sel[i] = 0;
          perm3_mask_low = vect_gen_perm_mask_checked (vectype, sel);

          for (i = 0, j = 0; i < nelt; i++)
            if (3 * i + k < 2 * nelt)
              sel[i] = i;
            else
              sel[i] = nelt + ((nelt + k) % 3) + 3 * (j++);

          perm3_mask_high = vect_gen_perm_mask_checked (vectype, sel);

          first_vect = dr_chain[0];
          second_vect = dr_chain[1];

          /* Create interleaving stmt (low part of):
             low = VEC_PERM_EXPR <first_vect, second_vect2, {k, 3 + k, 6 + k,
                                                             ...}>  */
          data_ref = make_temp_ssa_name (vectype, NULL, "vect_shuffle3_low");
          perm_stmt = gimple_build_assign (data_ref, VEC_PERM_EXPR, first_vect,
                                           second_vect, perm3_mask_low);
          vect_finish_stmt_generation (stmt, perm_stmt, gsi);

          /* Create interleaving stmt (high part of):
             high = VEC_PERM_EXPR <first_vect, second_vect2, {k, 3 + k, 6 + k,
                                                              ...}>  */
          first_vect = data_ref;
          second_vect = dr_chain[2];
          data_ref = make_temp_ssa_name (vectype, NULL, "vect_shuffle3_high");
          perm_stmt = gimple_build_assign (data_ref, VEC_PERM_EXPR, first_vect,
                                           second_vect, perm3_mask_high);
          vect_finish_stmt_generation (stmt, perm_stmt, gsi);
          (*result_chain)[k] = data_ref;
        }
    }
  else
    {
      /* If length is not equal to 3 then only power of 2 is supported.  */
      gcc_assert (exact_log2 (length) != -1);

      for (i = 0; i < nelt; ++i)
        sel[i] = i * 2;
      perm_mask_even = vect_gen_perm_mask_checked (vectype, sel);

      for (i = 0; i < nelt; ++i)
        sel[i] = i * 2 + 1;
      perm_mask_odd = vect_gen_perm_mask_checked (vectype, sel);

      for (i = 0; i < log_length; i++)
        {
          for (j = 0; j < length; j += 2)
            {
              first_vect = dr_chain[j];
              second_vect = dr_chain[j+1];

              /* data_ref = permute_even (first_data_ref, second_data_ref);  */
              data_ref = make_temp_ssa_name (vectype, NULL, "vect_perm_even");
              perm_stmt = gimple_build_assign (data_ref, VEC_PERM_EXPR,
                                               first_vect, second_vect,
                                               perm_mask_even);
              vect_finish_stmt_generation (stmt, perm_stmt, gsi);
              (*result_chain)[j/2] = data_ref;

              /* data_ref = permute_odd (first_data_ref, second_data_ref);  */
              data_ref = make_temp_ssa_name (vectype, NULL, "vect_perm_odd");
              perm_stmt = gimple_build_assign (data_ref, VEC_PERM_EXPR,
                                               first_vect, second_vect,
                                               perm_mask_odd);
              vect_finish_stmt_generation (stmt, perm_stmt, gsi);
              (*result_chain)[j/2+length/2] = data_ref;
            }
          memcpy (dr_chain.address (), result_chain->address (),
                  length * sizeof (tree));
        }
    }
}

/* Function vect_shift_permute_load_chain.

   Given a chain of loads in DR_CHAIN of LENGTH 2 or 3, generate
   sequence of stmts to reorder the input data accordingly.
   Return the final references for loads in RESULT_CHAIN.
   Return true if successed, false otherwise.

   E.g., LENGTH is 3 and the scalar type is short, i.e., VF is 8.
   The input is 3 vectors each containing 8 elements.  We assign a
   number to each element, the input sequence is:

   1st vec:   0  1  2  3  4  5  6  7
   2nd vec:   8  9 10 11 12 13 14 15
   3rd vec:  16 17 18 19 20 21 22 23

   The output sequence should be:

   1st vec:  0 3 6  9 12 15 18 21
   2nd vec:  1 4 7 10 13 16 19 22
   3rd vec:  2 5 8 11 14 17 20 23

   We use 3 shuffle instructions and 3 * 3 - 1 shifts to create such output.

   First we shuffle all 3 vectors to get correct elements order:

   1st vec:  ( 0  3  6) ( 1  4  7) ( 2  5)
   2nd vec:  ( 8 11 14) ( 9 12 15) (10 13)
   3rd vec:  (16 19 22) (17 20 23) (18 21)

   Next we unite and shift vector 3 times:

   1st step:
     shift right by 6 the concatenation of:
     "1st vec" and  "2nd vec"
       ( 0  3  6) ( 1  4  7) |( 2  5) _ ( 8 11 14) ( 9 12 15)| (10 13)
     "2nd vec" and  "3rd vec"
       ( 8 11 14) ( 9 12 15) |(10 13) _ (16 19 22) (17 20 23)| (18 21)
     "3rd vec" and  "1st vec"
       (16 19 22) (17 20 23) |(18 21) _ ( 0  3  6) ( 1  4  7)| ( 2  5)
                             | New vectors                   |

     So that now new vectors are:

     1st vec:  ( 2  5) ( 8 11 14) ( 9 12 15)
     2nd vec:  (10 13) (16 19 22) (17 20 23)
     3rd vec:  (18 21) ( 0  3  6) ( 1  4  7)

   2nd step:
     shift right by 5 the concatenation of:
     "1st vec" and  "3rd vec"
       ( 2  5) ( 8 11 14) |( 9 12 15) _ (18 21) ( 0  3  6)| ( 1  4  7)
     "2nd vec" and  "1st vec"
       (10 13) (16 19 22) |(17 20 23) _ ( 2  5) ( 8 11 14)| ( 9 12 15)
     "3rd vec" and  "2nd vec"
       (18 21) ( 0  3  6) |( 1  4  7) _ (10 13) (16 19 22)| (17 20 23)
                          | New vectors                   |

     So that now new vectors are:

     1st vec:  ( 9 12 15) (18 21) ( 0  3  6)
     2nd vec:  (17 20 23) ( 2  5) ( 8 11 14)
     3rd vec:  ( 1  4  7) (10 13) (16 19 22) READY

   3rd step:
     shift right by 5 the concatenation of:
     "1st vec" and  "1st vec"
       ( 9 12 15) (18 21) |( 0  3  6) _ ( 9 12 15) (18 21)| ( 0  3  6)
     shift right by 3 the concatenation of:
     "2nd vec" and  "2nd vec"
               (17 20 23) |( 2  5) ( 8 11 14) _ (17 20 23)| ( 2  5) ( 8 11 14)
                          | New vectors                   |

     So that now all vectors are READY:
     1st vec:  ( 0  3  6) ( 9 12 15) (18 21)
     2nd vec:  ( 2  5) ( 8 11 14) (17 20 23)
     3rd vec:  ( 1  4  7) (10 13) (16 19 22)

   This algorithm is faster than one in vect_permute_load_chain if:
     1.  "shift of a concatination" is faster than general permutation.
         This is usually so.
     2.  The TARGET machine can't execute vector instructions in parallel.
         This is because each step of the algorithm depends on previous.
         The algorithm in vect_permute_load_chain is much more parallel.

   The algorithm is applicable only for LOAD CHAIN LENGTH less than VF.
*/

static bool
vect_shift_permute_load_chain (vec<tree> dr_chain,
                               unsigned int length,
                               gimple *stmt,
                               gimple_stmt_iterator *gsi,
                               vec<tree> *result_chain)
{
  tree vect[3], vect_shift[3], data_ref, first_vect, second_vect;
  tree perm2_mask1, perm2_mask2, perm3_mask;
  tree select_mask, shift1_mask, shift2_mask, shift3_mask, shift4_mask;
  gimple *perm_stmt;

  tree vectype = STMT_VINFO_VECTYPE (vinfo_for_stmt (stmt));
  unsigned int i;
  unsigned nelt = TYPE_VECTOR_SUBPARTS (vectype);
  unsigned char *sel = XALLOCAVEC (unsigned char, nelt);
  stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
  loop_vec_info loop_vinfo = STMT_VINFO_LOOP_VINFO (stmt_info);

  result_chain->quick_grow (length);
  memcpy (result_chain->address (), dr_chain.address (),
          length * sizeof (tree));

  if (exact_log2 (length) != -1 && LOOP_VINFO_VECT_FACTOR (loop_vinfo) > 4)
    {
      unsigned int j, log_length = exact_log2 (length);
      for (i = 0; i < nelt / 2; ++i)
        sel[i] = i * 2;
      for (i = 0; i < nelt / 2; ++i)
        sel[nelt / 2 + i] = i * 2 + 1;
      if (!can_vec_perm_p (TYPE_MODE (vectype), false, sel))
        {
          if (dump_enabled_p ())
            dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                             "shuffle of 2 fields structure is not \
                              supported by target\n");
          return false;
        }
      perm2_mask1 = vect_gen_perm_mask_checked (vectype, sel);

      for (i = 0; i < nelt / 2; ++i)
        sel[i] = i * 2 + 1;
      for (i = 0; i < nelt / 2; ++i)
        sel[nelt / 2 + i] = i * 2;
      if (!can_vec_perm_p (TYPE_MODE (vectype), false, sel))
        {
          if (dump_enabled_p ())
            dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                             "shuffle of 2 fields structure is not \
                              supported by target\n");
          return false;
        }
      perm2_mask2 = vect_gen_perm_mask_checked (vectype, sel);

      /* Generating permutation constant to shift all elements.
         For vector length 8 it is {4 5 6 7 8 9 10 11}.  */
      for (i = 0; i < nelt; i++)
        sel[i] = nelt / 2 + i;
      if (!can_vec_perm_p (TYPE_MODE (vectype), false, sel))
        {
          if (dump_enabled_p ())
            dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                             "shift permutation is not supported by target\n");
          return false;
        }
      shift1_mask = vect_gen_perm_mask_checked (vectype, sel);

      /* Generating permutation constant to select vector from 2.
         For vector length 8 it is {0 1 2 3 12 13 14 15}.  */
      for (i = 0; i < nelt / 2; i++)
        sel[i] = i;
      for (i = nelt / 2; i < nelt; i++)
        sel[i] = nelt + i;
      if (!can_vec_perm_p (TYPE_MODE (vectype), false, sel))
        {
          if (dump_enabled_p ())
            dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                             "select is not supported by target\n");
          return false;
        }
      select_mask = vect_gen_perm_mask_checked (vectype, sel);

      for (i = 0; i < log_length; i++)
        {
          for (j = 0; j < length; j += 2)
            {
              first_vect = dr_chain[j];
              second_vect = dr_chain[j + 1];

              data_ref = make_temp_ssa_name (vectype, NULL, "vect_shuffle2");
              perm_stmt = gimple_build_assign (data_ref, VEC_PERM_EXPR,
                                               first_vect, first_vect,
                                               perm2_mask1);
              vect_finish_stmt_generation (stmt, perm_stmt, gsi);
              vect[0] = data_ref;

              data_ref = make_temp_ssa_name (vectype, NULL, "vect_shuffle2");
              perm_stmt = gimple_build_assign (data_ref, VEC_PERM_EXPR,
                                               second_vect, second_vect,
                                               perm2_mask2);
              vect_finish_stmt_generation (stmt, perm_stmt, gsi);
              vect[1] = data_ref;

              data_ref = make_temp_ssa_name (vectype, NULL, "vect_shift");
              perm_stmt = gimple_build_assign (data_ref, VEC_PERM_EXPR,
                                               vect[0], vect[1], shift1_mask);
              vect_finish_stmt_generation (stmt, perm_stmt, gsi);
              (*result_chain)[j/2 + length/2] = data_ref;

              data_ref = make_temp_ssa_name (vectype, NULL, "vect_select");
              perm_stmt = gimple_build_assign (data_ref, VEC_PERM_EXPR,
                                               vect[0], vect[1], select_mask);
              vect_finish_stmt_generation (stmt, perm_stmt, gsi);
              (*result_chain)[j/2] = data_ref;
            }
          memcpy (dr_chain.address (), result_chain->address (),
                  length * sizeof (tree));
        }
      return true;
    }
  if (length == 3 && LOOP_VINFO_VECT_FACTOR (loop_vinfo) > 2)
    {
      unsigned int k = 0, l = 0;

      /* Generating permutation constant to get all elements in rigth order.
         For vector length 8 it is {0 3 6 1 4 7 2 5}.  */
      for (i = 0; i < nelt; i++)
        {
          if (3 * k + (l % 3) >= nelt)
            {
              k = 0;
              l += (3 - (nelt % 3));
            }
          sel[i] = 3 * k + (l % 3);
          k++;
        }
      if (!can_vec_perm_p (TYPE_MODE (vectype), false, sel))
        {
          if (dump_enabled_p ())
            dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                             "shuffle of 3 fields structure is not \
                              supported by target\n");
          return false;
        }
      perm3_mask = vect_gen_perm_mask_checked (vectype, sel);

      /* Generating permutation constant to shift all elements.
         For vector length 8 it is {6 7 8 9 10 11 12 13}.  */
      for (i = 0; i < nelt; i++)
        sel[i] = 2 * (nelt / 3) + (nelt % 3) + i;
      if (!can_vec_perm_p (TYPE_MODE (vectype), false, sel))
        {
          if (dump_enabled_p ())
            dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                             "shift permutation is not supported by target\n");
          return false;
        }
      shift1_mask = vect_gen_perm_mask_checked (vectype, sel);

      /* Generating permutation constant to shift all elements.
         For vector length 8 it is {5 6 7 8 9 10 11 12}.  */
      for (i = 0; i < nelt; i++)
        sel[i] = 2 * (nelt / 3) + 1 + i;
      if (!can_vec_perm_p (TYPE_MODE (vectype), false, sel))
        {
          if (dump_enabled_p ())
            dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                             "shift permutation is not supported by target\n");
          return false;
        }
      shift2_mask = vect_gen_perm_mask_checked (vectype, sel);

      /* Generating permutation constant to shift all elements.
         For vector length 8 it is {3 4 5 6 7 8 9 10}.  */
      for (i = 0; i < nelt; i++)
        sel[i] = (nelt / 3) + (nelt % 3) / 2 + i;
      if (!can_vec_perm_p (TYPE_MODE (vectype), false, sel))
        {
          if (dump_enabled_p ())
            dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                             "shift permutation is not supported by target\n");
          return false;
        }
      shift3_mask = vect_gen_perm_mask_checked (vectype, sel);

      /* Generating permutation constant to shift all elements.
         For vector length 8 it is {5 6 7 8 9 10 11 12}.  */
      for (i = 0; i < nelt; i++)
        sel[i] = 2 * (nelt / 3) + (nelt % 3) / 2 + i;
      if (!can_vec_perm_p (TYPE_MODE (vectype), false, sel))
        {
          if (dump_enabled_p ())
            dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                             "shift permutation is not supported by target\n");
          return false;
        }
      shift4_mask = vect_gen_perm_mask_checked (vectype, sel);

      for (k = 0; k < 3; k++)
        {
          data_ref = make_temp_ssa_name (vectype, NULL, "vect_shuffle3");
          perm_stmt = gimple_build_assign (data_ref, VEC_PERM_EXPR,
                                           dr_chain[k], dr_chain[k],
                                           perm3_mask);
          vect_finish_stmt_generation (stmt, perm_stmt, gsi);
          vect[k] = data_ref;
        }

      for (k = 0; k < 3; k++)
        {
          data_ref = make_temp_ssa_name (vectype, NULL, "vect_shift1");
          perm_stmt = gimple_build_assign (data_ref, VEC_PERM_EXPR,
                                           vect[k % 3], vect[(k + 1) % 3],
                                           shift1_mask);
          vect_finish_stmt_generation (stmt, perm_stmt, gsi);
          vect_shift[k] = data_ref;
        }

      for (k = 0; k < 3; k++)
        {
          data_ref = make_temp_ssa_name (vectype, NULL, "vect_shift2");
          perm_stmt = gimple_build_assign (data_ref, VEC_PERM_EXPR,
                                           vect_shift[(4 - k) % 3],
                                           vect_shift[(3 - k) % 3],
                                           shift2_mask);
          vect_finish_stmt_generation (stmt, perm_stmt, gsi);
          vect[k] = data_ref;
        }

      (*result_chain)[3 - (nelt % 3)] = vect[2];

      data_ref = make_temp_ssa_name (vectype, NULL, "vect_shift3");
      perm_stmt = gimple_build_assign (data_ref, VEC_PERM_EXPR, vect[0],
                                       vect[0], shift3_mask);
      vect_finish_stmt_generation (stmt, perm_stmt, gsi);
      (*result_chain)[nelt % 3] = data_ref;

      data_ref = make_temp_ssa_name (vectype, NULL, "vect_shift4");
      perm_stmt = gimple_build_assign (data_ref, VEC_PERM_EXPR, vect[1],
                                       vect[1], shift4_mask);
      vect_finish_stmt_generation (stmt, perm_stmt, gsi);
      (*result_chain)[0] = data_ref;
      return true;
    }
  return false;
}

/* Function vect_transform_grouped_load.

   Given a chain of input interleaved data-refs (in DR_CHAIN), build statements
   to perform their permutation and ascribe the result vectorized statements to
   the scalar statements.
*/

void
vect_transform_grouped_load (gimple *stmt, vec<tree> dr_chain, int size,
                             gimple_stmt_iterator *gsi)
{
  machine_mode mode;
  vec<tree> result_chain = vNULL;

  /* DR_CHAIN contains input data-refs that are a part of the interleaving.
     RESULT_CHAIN is the output of vect_permute_load_chain, it contains permuted
     vectors, that are ready for vector computation.  */
  result_chain.create (size);

  /* If reassociation width for vector type is 2 or greater target machine can
     execute 2 or more vector instructions in parallel.  Otherwise try to
     get chain for loads group using vect_shift_permute_load_chain.  */
  mode = TYPE_MODE (STMT_VINFO_VECTYPE (vinfo_for_stmt (stmt)));
  if (targetm.sched.reassociation_width (VEC_PERM_EXPR, mode) > 1
      || exact_log2 (size) != -1
      || !vect_shift_permute_load_chain (dr_chain, size, stmt,
                                         gsi, &result_chain))
    vect_permute_load_chain (dr_chain, size, stmt, gsi, &result_chain);
  vect_record_grouped_load_vectors (stmt, result_chain);
  result_chain.release ();
}

/* RESULT_CHAIN contains the output of a group of grouped loads that were
   generated as part of the vectorization of STMT.  Assign the statement
   for each vector to the associated scalar statement.  */

void
vect_record_grouped_load_vectors (gimple *stmt, vec<tree> result_chain)
{
  gimple *first_stmt = GROUP_FIRST_ELEMENT (vinfo_for_stmt (stmt));
  gimple *next_stmt, *new_stmt;
  unsigned int i, gap_count;
  tree tmp_data_ref;

  /* Put a permuted data-ref in the VECTORIZED_STMT field.
     Since we scan the chain starting from it's first node, their order
     corresponds the order of data-refs in RESULT_CHAIN.  */
  next_stmt = first_stmt;
  gap_count = 1;
  FOR_EACH_VEC_ELT (result_chain, i, tmp_data_ref)
    {
      if (!next_stmt)
        break;

      /* Skip the gaps.  Loads created for the gaps will be removed by dead
       code elimination pass later.  No need to check for the first stmt in
       the group, since it always exists.
       GROUP_GAP is the number of steps in elements from the previous
       access (if there is no gap GROUP_GAP is 1).  We skip loads that
       correspond to the gaps.  */
      if (next_stmt != first_stmt
          && gap_count < GROUP_GAP (vinfo_for_stmt (next_stmt)))
      {
        gap_count++;
        continue;
      }

      while (next_stmt)
        {
          new_stmt = SSA_NAME_DEF_STMT (tmp_data_ref);
          /* We assume that if VEC_STMT is not NULL, this is a case of multiple
             copies, and we put the new vector statement in the first available
             RELATED_STMT.  */
          if (!STMT_VINFO_VEC_STMT (vinfo_for_stmt (next_stmt)))
            STMT_VINFO_VEC_STMT (vinfo_for_stmt (next_stmt)) = new_stmt;
          else
            {
              if (!GROUP_SAME_DR_STMT (vinfo_for_stmt (next_stmt)))
                {
                  gimple *prev_stmt =
                    STMT_VINFO_VEC_STMT (vinfo_for_stmt (next_stmt));
                  gimple *rel_stmt =
                    STMT_VINFO_RELATED_STMT (vinfo_for_stmt (prev_stmt));
                  while (rel_stmt)
                    {
                      prev_stmt = rel_stmt;
                      rel_stmt =
                        STMT_VINFO_RELATED_STMT (vinfo_for_stmt (rel_stmt));
                    }

                  STMT_VINFO_RELATED_STMT (vinfo_for_stmt (prev_stmt)) =
                    new_stmt;
                }
            }

          next_stmt = GROUP_NEXT_ELEMENT (vinfo_for_stmt (next_stmt));
          gap_count = 1;
          /* If NEXT_STMT accesses the same DR as the previous statement,
             put the same TMP_DATA_REF as its vectorized statement; otherwise
             get the next data-ref from RESULT_CHAIN.  */
          if (!next_stmt || !GROUP_SAME_DR_STMT (vinfo_for_stmt (next_stmt)))
            break;
        }
    }
}

/* Function vect_force_dr_alignment_p.

   Returns whether the alignment of a DECL can be forced to be aligned
   on ALIGNMENT bit boundary.  */

bool
vect_can_force_dr_alignment_p (const_tree decl, unsigned int alignment)
{
  if (TREE_CODE (decl) != VAR_DECL)
    return false;

  if (decl_in_symtab_p (decl)
      && !symtab_node::get (decl)->can_increase_alignment_p ())
    return false;

  if (TREE_STATIC (decl))
    return (alignment <= MAX_OFILE_ALIGNMENT);
  else
    return (alignment <= MAX_STACK_ALIGNMENT);
}


/* Return whether the data reference DR is supported with respect to its
   alignment.
   If CHECK_ALIGNED_ACCESSES is TRUE, check if the access is supported even
   it is aligned, i.e., check if it is possible to vectorize it with different
   alignment.  */

enum dr_alignment_support
vect_supportable_dr_alignment (struct data_reference *dr,
                               bool check_aligned_accesses)
{
  gimple *stmt = DR_STMT (dr);
  stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
  tree vectype = STMT_VINFO_VECTYPE (stmt_info);
  machine_mode mode = TYPE_MODE (vectype);
  loop_vec_info loop_vinfo = STMT_VINFO_LOOP_VINFO (stmt_info);
  struct loop *vect_loop = NULL;
  bool nested_in_vect_loop = false;

  if (aligned_access_p (dr) && !check_aligned_accesses)
    return dr_aligned;

  /* For now assume all conditional loads/stores support unaligned
     access without any special code.  */
  if (is_gimple_call (stmt)
      && gimple_call_internal_p (stmt)
      && (gimple_call_internal_fn (stmt) == IFN_MASK_LOAD
          || gimple_call_internal_fn (stmt) == IFN_MASK_STORE))
    return dr_unaligned_supported;

  if (loop_vinfo)
    {
      vect_loop = LOOP_VINFO_LOOP (loop_vinfo);
      nested_in_vect_loop = nested_in_vect_loop_p (vect_loop, stmt);
    }

  /* Possibly unaligned access.  */

  /* We can choose between using the implicit realignment scheme (generating
     a misaligned_move stmt) and the explicit realignment scheme (generating
     aligned loads with a REALIGN_LOAD).  There are two variants to the
     explicit realignment scheme: optimized, and unoptimized.
     We can optimize the realignment only if the step between consecutive
     vector loads is equal to the vector size.  Since the vector memory
     accesses advance in steps of VS (Vector Size) in the vectorized loop, it
     is guaranteed that the misalignment amount remains the same throughout the
     execution of the vectorized loop.  Therefore, we can create the
     "realignment token" (the permutation mask that is passed to REALIGN_LOAD)
     at the loop preheader.

     However, in the case of outer-loop vectorization, when vectorizing a
     memory access in the inner-loop nested within the LOOP that is now being
     vectorized, while it is guaranteed that the misalignment of the
     vectorized memory access will remain the same in different outer-loop
     iterations, it is *not* guaranteed that is will remain the same throughout
     the execution of the inner-loop.  This is because the inner-loop advances
     with the original scalar step (and not in steps of VS).  If the inner-loop
     step happens to be a multiple of VS, then the misalignment remains fixed
     and we can use the optimized realignment scheme.  For example:

      for (i=0; i<N; i++)
        for (j=0; j<M; j++)
          s += a[i+j];

     When vectorizing the i-loop in the above example, the step between
     consecutive vector loads is 1, and so the misalignment does not remain
     fixed across the execution of the inner-loop, and the realignment cannot
     be optimized (as illustrated in the following pseudo vectorized loop):

      for (i=0; i<N; i+=4)
        for (j=0; j<M; j++){
          vs += vp[i+j]; // misalignment of &vp[i+j] is {0,1,2,3,0,1,2,3,...}
                         // when j is {0,1,2,3,4,5,6,7,...} respectively.
                         // (assuming that we start from an aligned address).
          }

     We therefore have to use the unoptimized realignment scheme:

      for (i=0; i<N; i+=4)
          for (j=k; j<M; j+=4)
          vs += vp[i+j]; // misalignment of &vp[i+j] is always k (assuming
                           // that the misalignment of the initial address is
                           // 0).

     The loop can then be vectorized as follows:

      for (k=0; k<4; k++){
        rt = get_realignment_token (&vp[k]);
        for (i=0; i<N; i+=4){
          v1 = vp[i+k];
          for (j=k; j<M; j+=4){
            v2 = vp[i+j+VS-1];
            va = REALIGN_LOAD <v1,v2,rt>;
            vs += va;
            v1 = v2;
          }
        }
    } */

  if (DR_IS_READ (dr))
    {
      bool is_packed = false;
      tree type = (TREE_TYPE (DR_REF (dr)));

      if (optab_handler (vec_realign_load_optab, mode) != CODE_FOR_nothing
          && (!targetm.vectorize.builtin_mask_for_load
              || targetm.vectorize.builtin_mask_for_load ()))
        {
          tree vectype = STMT_VINFO_VECTYPE (stmt_info);
          if ((nested_in_vect_loop
               && (TREE_INT_CST_LOW (DR_STEP (dr))
                   != GET_MODE_SIZE (TYPE_MODE (vectype))))
              || !loop_vinfo)
            return dr_explicit_realign;
          else
            return dr_explicit_realign_optimized;
        }
      if (!known_alignment_for_access_p (dr))
        is_packed = not_size_aligned (DR_REF (dr));

      if ((TYPE_USER_ALIGN (type) && !is_packed)
          || targetm.vectorize.
               support_vector_misalignment (mode, type,
                                            DR_MISALIGNMENT (dr), is_packed))
        /* Can't software pipeline the loads, but can at least do them.  */
        return dr_unaligned_supported;
    }
  else
    {
      bool is_packed = false;
      tree type = (TREE_TYPE (DR_REF (dr)));

      if (!known_alignment_for_access_p (dr))
        is_packed = not_size_aligned (DR_REF (dr));

     if ((TYPE_USER_ALIGN (type) && !is_packed)
         || targetm.vectorize.
              support_vector_misalignment (mode, type,
                                           DR_MISALIGNMENT (dr), is_packed))
       return dr_unaligned_supported;
    }

  /* Unsupported.  */
  return dr_unaligned_unsupported;
}