c++: using from enclosing class template [PR105006]

[official-gcc.git] / gcc / tree-vect-loop-manip.cc

/* Vectorizer Specific Loop Manipulations
   Copyright (C) 2003-2022 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 "tree.h"
#include "gimple.h"
#include "cfghooks.h"
#include "tree-pass.h"
#include "ssa.h"
#include "fold-const.h"
#include "cfganal.h"
#include "gimplify.h"
#include "gimple-iterator.h"
#include "gimplify-me.h"
#include "tree-cfg.h"
#include "tree-ssa-loop-manip.h"
#include "tree-into-ssa.h"
#include "tree-ssa.h"
#include "cfgloop.h"
#include "tree-scalar-evolution.h"
#include "tree-vectorizer.h"
#include "tree-ssa-loop-ivopts.h"
#include "gimple-fold.h"
#include "tree-ssa-loop-niter.h"
#include "internal-fn.h"
#include "stor-layout.h"
#include "optabs-query.h"
#include "vec-perm-indices.h"
#include "insn-config.h"
#include "rtl.h"
#include "recog.h"

/*************************************************************************
  Simple Loop Peeling Utilities

  Utilities to support loop peeling for vectorization purposes.
 *************************************************************************/


/* Renames the use *OP_P.  */

static void
rename_use_op (use_operand_p op_p)
{
  tree new_name;

  if (TREE_CODE (USE_FROM_PTR (op_p)) != SSA_NAME)
    return;

  new_name = get_current_def (USE_FROM_PTR (op_p));

  /* Something defined outside of the loop.  */
  if (!new_name)
    return;

  /* An ordinary ssa name defined in the loop.  */

  SET_USE (op_p, new_name);
}


/* Renames the variables in basic block BB.  Allow renaming  of PHI arguments
   on edges incoming from outer-block header if RENAME_FROM_OUTER_LOOP is
   true.  */

static void
rename_variables_in_bb (basic_block bb, bool rename_from_outer_loop)
{
  gimple *stmt;
  use_operand_p use_p;
  ssa_op_iter iter;
  edge e;
  edge_iterator ei;
  class loop *loop = bb->loop_father;
  class loop *outer_loop = NULL;

  if (rename_from_outer_loop)
    {
      gcc_assert (loop);
      outer_loop = loop_outer (loop);
    }

  for (gimple_stmt_iterator gsi = gsi_start_bb (bb); !gsi_end_p (gsi);
       gsi_next (&gsi))
    {
      stmt = gsi_stmt (gsi);
      FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES)
        rename_use_op (use_p);
    }

  FOR_EACH_EDGE (e, ei, bb->preds)
    {
      if (!flow_bb_inside_loop_p (loop, e->src))
        {
          if (!rename_from_outer_loop)
            continue;
          if (e->src != outer_loop->header)
            {
              if (outer_loop->inner->next)
                {
                  /* If outer_loop has 2 inner loops, allow there to
                     be an extra basic block which decides which of the
                     two loops to use using LOOP_VECTORIZED.  */
                  if (!single_pred_p (e->src)
                      || single_pred (e->src) != outer_loop->header)
                    continue;
                }
            }
        }
      for (gphi_iterator gsi = gsi_start_phis (bb); !gsi_end_p (gsi);
           gsi_next (&gsi))
        rename_use_op (PHI_ARG_DEF_PTR_FROM_EDGE (gsi.phi (), e));
    }
}


struct adjust_info
{
  tree from, to;
  basic_block bb;
};

/* A stack of values to be adjusted in debug stmts.  We have to
   process them LIFO, so that the closest substitution applies.  If we
   processed them FIFO, without the stack, we might substitute uses
   with a PHI DEF that would soon become non-dominant, and when we got
   to the suitable one, it wouldn't have anything to substitute any
   more.  */
static vec<adjust_info, va_heap> adjust_vec;

/* Adjust any debug stmts that referenced AI->from values to use the
   loop-closed AI->to, if the references are dominated by AI->bb and
   not by the definition of AI->from.  */

static void
adjust_debug_stmts_now (adjust_info *ai)
{
  basic_block bbphi = ai->bb;
  tree orig_def = ai->from;
  tree new_def = ai->to;
  imm_use_iterator imm_iter;
  gimple *stmt;
  basic_block bbdef = gimple_bb (SSA_NAME_DEF_STMT (orig_def));

  gcc_assert (dom_info_available_p (CDI_DOMINATORS));

  /* Adjust any debug stmts that held onto non-loop-closed
     references.  */
  FOR_EACH_IMM_USE_STMT (stmt, imm_iter, orig_def)
    {
      use_operand_p use_p;
      basic_block bbuse;

      if (!is_gimple_debug (stmt))
        continue;

      gcc_assert (gimple_debug_bind_p (stmt));

      bbuse = gimple_bb (stmt);

      if ((bbuse == bbphi
           || dominated_by_p (CDI_DOMINATORS, bbuse, bbphi))
          && !(bbuse == bbdef
               || dominated_by_p (CDI_DOMINATORS, bbuse, bbdef)))
        {
          if (new_def)
            FOR_EACH_IMM_USE_ON_STMT (use_p, imm_iter)
              SET_USE (use_p, new_def);
          else
            {
              gimple_debug_bind_reset_value (stmt);
              update_stmt (stmt);
            }
        }
    }
}

/* Adjust debug stmts as scheduled before.  */

static void
adjust_vec_debug_stmts (void)
{
  if (!MAY_HAVE_DEBUG_BIND_STMTS)
    return;

  gcc_assert (adjust_vec.exists ());

  while (!adjust_vec.is_empty ())
    {
      adjust_debug_stmts_now (&adjust_vec.last ());
      adjust_vec.pop ();
    }
}

/* Adjust any debug stmts that referenced FROM values to use the
   loop-closed TO, if the references are dominated by BB and not by
   the definition of FROM.  If adjust_vec is non-NULL, adjustments
   will be postponed until adjust_vec_debug_stmts is called.  */

static void
adjust_debug_stmts (tree from, tree to, basic_block bb)
{
  adjust_info ai;

  if (MAY_HAVE_DEBUG_BIND_STMTS
      && TREE_CODE (from) == SSA_NAME
      && ! SSA_NAME_IS_DEFAULT_DEF (from)
      && ! virtual_operand_p (from))
    {
      ai.from = from;
      ai.to = to;
      ai.bb = bb;

      if (adjust_vec.exists ())
        adjust_vec.safe_push (ai);
      else
        adjust_debug_stmts_now (&ai);
    }
}

/* Change E's phi arg in UPDATE_PHI to NEW_DEF, and record information
   to adjust any debug stmts that referenced the old phi arg,
   presumably non-loop-closed references left over from other
   transformations.  */

static void
adjust_phi_and_debug_stmts (gimple *update_phi, edge e, tree new_def)
{
  tree orig_def = PHI_ARG_DEF_FROM_EDGE (update_phi, e);

  SET_PHI_ARG_DEF (update_phi, e->dest_idx, new_def);

  if (MAY_HAVE_DEBUG_BIND_STMTS)
    adjust_debug_stmts (orig_def, PHI_RESULT (update_phi),
                        gimple_bb (update_phi));
}

/* Define one loop rgroup control CTRL from loop LOOP.  INIT_CTRL is the value
   that the control should have during the first iteration and NEXT_CTRL is the
   value that it should have on subsequent iterations.  */

static void
vect_set_loop_control (class loop *loop, tree ctrl, tree init_ctrl,
                       tree next_ctrl)
{
  gphi *phi = create_phi_node (ctrl, loop->header);
  add_phi_arg (phi, init_ctrl, loop_preheader_edge (loop), UNKNOWN_LOCATION);
  add_phi_arg (phi, next_ctrl, loop_latch_edge (loop), UNKNOWN_LOCATION);
}

/* Add SEQ to the end of LOOP's preheader block.  */

static void
add_preheader_seq (class loop *loop, gimple_seq seq)
{
  if (seq)
    {
      edge pe = loop_preheader_edge (loop);
      basic_block new_bb = gsi_insert_seq_on_edge_immediate (pe, seq);
      gcc_assert (!new_bb);
    }
}

/* Add SEQ to the beginning of LOOP's header block.  */

static void
add_header_seq (class loop *loop, gimple_seq seq)
{
  if (seq)
    {
      gimple_stmt_iterator gsi = gsi_after_labels (loop->header);
      gsi_insert_seq_before (&gsi, seq, GSI_SAME_STMT);
    }
}

/* Return true if the target can interleave elements of two vectors.
   OFFSET is 0 if the first half of the vectors should be interleaved
   or 1 if the second half should.  When returning true, store the
   associated permutation in INDICES.  */

static bool
interleave_supported_p (vec_perm_indices *indices, tree vectype,
                        unsigned int offset)
{
  poly_uint64 nelts = TYPE_VECTOR_SUBPARTS (vectype);
  poly_uint64 base = exact_div (nelts, 2) * offset;
  vec_perm_builder sel (nelts, 2, 3);
  for (unsigned int i = 0; i < 3; ++i)
    {
      sel.quick_push (base + i);
      sel.quick_push (base + i + nelts);
    }
  indices->new_vector (sel, 2, nelts);
  return can_vec_perm_const_p (TYPE_MODE (vectype), *indices);
}

/* Try to use permutes to define the masks in DEST_RGM using the masks
   in SRC_RGM, given that the former has twice as many masks as the
   latter.  Return true on success, adding any new statements to SEQ.  */

static bool
vect_maybe_permute_loop_masks (gimple_seq *seq, rgroup_controls *dest_rgm,
                               rgroup_controls *src_rgm)
{
  tree src_masktype = src_rgm->type;
  tree dest_masktype = dest_rgm->type;
  machine_mode src_mode = TYPE_MODE (src_masktype);
  insn_code icode1, icode2;
  if (dest_rgm->max_nscalars_per_iter <= src_rgm->max_nscalars_per_iter
      && (icode1 = optab_handler (vec_unpacku_hi_optab,
                                  src_mode)) != CODE_FOR_nothing
      && (icode2 = optab_handler (vec_unpacku_lo_optab,
                                  src_mode)) != CODE_FOR_nothing)
    {
      /* Unpacking the source masks gives at least as many mask bits as
         we need.  We can then VIEW_CONVERT any excess bits away.  */
      machine_mode dest_mode = insn_data[icode1].operand[0].mode;
      gcc_assert (dest_mode == insn_data[icode2].operand[0].mode);
      tree unpack_masktype = vect_halve_mask_nunits (src_masktype, dest_mode);
      for (unsigned int i = 0; i < dest_rgm->controls.length (); ++i)
        {
          tree src = src_rgm->controls[i / 2];
          tree dest = dest_rgm->controls[i];
          tree_code code = ((i & 1) == (BYTES_BIG_ENDIAN ? 0 : 1)
                            ? VEC_UNPACK_HI_EXPR
                            : VEC_UNPACK_LO_EXPR);
          gassign *stmt;
          if (dest_masktype == unpack_masktype)
            stmt = gimple_build_assign (dest, code, src);
          else
            {
              tree temp = make_ssa_name (unpack_masktype);
              stmt = gimple_build_assign (temp, code, src);
              gimple_seq_add_stmt (seq, stmt);
              stmt = gimple_build_assign (dest, VIEW_CONVERT_EXPR,
                                          build1 (VIEW_CONVERT_EXPR,
                                                  dest_masktype, temp));
            }
          gimple_seq_add_stmt (seq, stmt);
        }
      return true;
    }
  vec_perm_indices indices[2];
  if (dest_masktype == src_masktype
      && interleave_supported_p (&indices[0], src_masktype, 0)
      && interleave_supported_p (&indices[1], src_masktype, 1))
    {
      /* The destination requires twice as many mask bits as the source, so
         we can use interleaving permutes to double up the number of bits.  */
      tree masks[2];
      for (unsigned int i = 0; i < 2; ++i)
        masks[i] = vect_gen_perm_mask_checked (src_masktype, indices[i]);
      for (unsigned int i = 0; i < dest_rgm->controls.length (); ++i)
        {
          tree src = src_rgm->controls[i / 2];
          tree dest = dest_rgm->controls[i];
          gimple *stmt = gimple_build_assign (dest, VEC_PERM_EXPR,
                                              src, src, masks[i & 1]);
          gimple_seq_add_stmt (seq, stmt);
        }
      return true;
    }
  return false;
}

/* Helper for vect_set_loop_condition_partial_vectors.  Generate definitions
   for all the rgroup controls in RGC and return a control that is nonzero
   when the loop needs to iterate.  Add any new preheader statements to
   PREHEADER_SEQ.  Use LOOP_COND_GSI to insert code before the exit gcond.

   RGC belongs to loop LOOP.  The loop originally iterated NITERS
   times and has been vectorized according to LOOP_VINFO.

   If NITERS_SKIP is nonnull, the first iteration of the vectorized loop
   starts with NITERS_SKIP dummy iterations of the scalar loop before
   the real work starts.  The mask elements for these dummy iterations
   must be 0, to ensure that the extra iterations do not have an effect.

   It is known that:

     NITERS * RGC->max_nscalars_per_iter * RGC->factor

   does not overflow.  However, MIGHT_WRAP_P says whether an induction
   variable that starts at 0 and has step:

     VF * RGC->max_nscalars_per_iter * RGC->factor

   might overflow before hitting a value above:

     (NITERS + NITERS_SKIP) * RGC->max_nscalars_per_iter * RGC->factor

   This means that we cannot guarantee that such an induction variable
   would ever hit a value that produces a set of all-false masks or zero
   lengths for RGC.

   Note: the cost of the code generated by this function is modeled
   by vect_estimate_min_profitable_iters, so changes here may need
   corresponding changes there.  */

static tree
vect_set_loop_controls_directly (class loop *loop, loop_vec_info loop_vinfo,
                                 gimple_seq *preheader_seq,
                                 gimple_seq *header_seq,
                                 gimple_stmt_iterator loop_cond_gsi,
                                 rgroup_controls *rgc, tree niters,
                                 tree niters_skip, bool might_wrap_p)
{
  tree compare_type = LOOP_VINFO_RGROUP_COMPARE_TYPE (loop_vinfo);
  tree iv_type = LOOP_VINFO_RGROUP_IV_TYPE (loop_vinfo);
  bool use_masks_p = LOOP_VINFO_FULLY_MASKED_P (loop_vinfo);

  tree ctrl_type = rgc->type;
  unsigned int nitems_per_iter = rgc->max_nscalars_per_iter * rgc->factor;
  poly_uint64 nitems_per_ctrl = TYPE_VECTOR_SUBPARTS (ctrl_type) * rgc->factor;
  poly_uint64 vf = LOOP_VINFO_VECT_FACTOR (loop_vinfo);
  tree length_limit = NULL_TREE;
  /* For length, we need length_limit to ensure length in range.  */
  if (!use_masks_p)
    length_limit = build_int_cst (compare_type, nitems_per_ctrl);

  /* Calculate the maximum number of item values that the rgroup
     handles in total, the number that it handles for each iteration
     of the vector loop, and the number that it should skip during the
     first iteration of the vector loop.  */
  tree nitems_total = niters;
  tree nitems_step = build_int_cst (iv_type, vf);
  tree nitems_skip = niters_skip;
  if (nitems_per_iter != 1)
    {
      /* We checked before setting LOOP_VINFO_USING_PARTIAL_VECTORS_P that
         these multiplications don't overflow.  */
      tree compare_factor = build_int_cst (compare_type, nitems_per_iter);
      tree iv_factor = build_int_cst (iv_type, nitems_per_iter);
      nitems_total = gimple_build (preheader_seq, MULT_EXPR, compare_type,
                                   nitems_total, compare_factor);
      nitems_step = gimple_build (preheader_seq, MULT_EXPR, iv_type,
                                  nitems_step, iv_factor);
      if (nitems_skip)
        nitems_skip = gimple_build (preheader_seq, MULT_EXPR, compare_type,
                                    nitems_skip, compare_factor);
    }

  /* Create an induction variable that counts the number of items
     processed.  */
  tree index_before_incr, index_after_incr;
  gimple_stmt_iterator incr_gsi;
  bool insert_after;
  standard_iv_increment_position (loop, &incr_gsi, &insert_after);
  create_iv (build_int_cst (iv_type, 0), nitems_step, NULL_TREE, loop,
             &incr_gsi, insert_after, &index_before_incr, &index_after_incr);

  tree zero_index = build_int_cst (compare_type, 0);
  tree test_index, test_limit, first_limit;
  gimple_stmt_iterator *test_gsi;
  if (might_wrap_p)
    {
      /* In principle the loop should stop iterating once the incremented
         IV reaches a value greater than or equal to:

           NITEMS_TOTAL +[infinite-prec] NITEMS_SKIP

         However, there's no guarantee that this addition doesn't overflow
         the comparison type, or that the IV hits a value above it before
         wrapping around.  We therefore adjust the limit down by one
         IV step:

           (NITEMS_TOTAL +[infinite-prec] NITEMS_SKIP)
           -[infinite-prec] NITEMS_STEP

         and compare the IV against this limit _before_ incrementing it.
         Since the comparison type is unsigned, we actually want the
         subtraction to saturate at zero:

           (NITEMS_TOTAL +[infinite-prec] NITEMS_SKIP)
           -[sat] NITEMS_STEP

         And since NITEMS_SKIP < NITEMS_STEP, we can reassociate this as:

           NITEMS_TOTAL -[sat] (NITEMS_STEP - NITEMS_SKIP)

         where the rightmost subtraction can be done directly in
         COMPARE_TYPE.  */
      test_index = index_before_incr;
      tree adjust = gimple_convert (preheader_seq, compare_type,
                                    nitems_step);
      if (nitems_skip)
        adjust = gimple_build (preheader_seq, MINUS_EXPR, compare_type,
                               adjust, nitems_skip);
      test_limit = gimple_build (preheader_seq, MAX_EXPR, compare_type,
                                 nitems_total, adjust);
      test_limit = gimple_build (preheader_seq, MINUS_EXPR, compare_type,
                                 test_limit, adjust);
      test_gsi = &incr_gsi;

      /* Get a safe limit for the first iteration.  */
      if (nitems_skip)
        {
          /* The first vector iteration can handle at most NITEMS_STEP
             items.  NITEMS_STEP <= CONST_LIMIT, and adding
             NITEMS_SKIP to that cannot overflow.  */
          tree const_limit = build_int_cst (compare_type,
                                            LOOP_VINFO_VECT_FACTOR (loop_vinfo)
                                            * nitems_per_iter);
          first_limit = gimple_build (preheader_seq, MIN_EXPR, compare_type,
                                      nitems_total, const_limit);
          first_limit = gimple_build (preheader_seq, PLUS_EXPR, compare_type,
                                      first_limit, nitems_skip);
        }
      else
        /* For the first iteration it doesn't matter whether the IV hits
           a value above NITEMS_TOTAL.  That only matters for the latch
           condition.  */
        first_limit = nitems_total;
    }
  else
    {
      /* Test the incremented IV, which will always hit a value above
         the bound before wrapping.  */
      test_index = index_after_incr;
      test_limit = nitems_total;
      if (nitems_skip)
        test_limit = gimple_build (preheader_seq, PLUS_EXPR, compare_type,
                                   test_limit, nitems_skip);
      test_gsi = &loop_cond_gsi;

      first_limit = test_limit;
    }

  /* Convert the IV value to the comparison type (either a no-op or
     a demotion).  */
  gimple_seq test_seq = NULL;
  test_index = gimple_convert (&test_seq, compare_type, test_index);
  gsi_insert_seq_before (test_gsi, test_seq, GSI_SAME_STMT);

  /* Provide a definition of each control in the group.  */
  tree next_ctrl = NULL_TREE;
  tree ctrl;
  unsigned int i;
  FOR_EACH_VEC_ELT_REVERSE (rgc->controls, i, ctrl)
    {
      /* Previous controls will cover BIAS items.  This control covers the
         next batch.  */
      poly_uint64 bias = nitems_per_ctrl * i;
      tree bias_tree = build_int_cst (compare_type, bias);

      /* See whether the first iteration of the vector loop is known
         to have a full control.  */
      poly_uint64 const_limit;
      bool first_iteration_full
        = (poly_int_tree_p (first_limit, &const_limit)
           && known_ge (const_limit, (i + 1) * nitems_per_ctrl));

      /* Rather than have a new IV that starts at BIAS and goes up to
         TEST_LIMIT, prefer to use the same 0-based IV for each control
         and adjust the bound down by BIAS.  */
      tree this_test_limit = test_limit;
      if (i != 0)
        {
          this_test_limit = gimple_build (preheader_seq, MAX_EXPR,
                                          compare_type, this_test_limit,
                                          bias_tree);
          this_test_limit = gimple_build (preheader_seq, MINUS_EXPR,
                                          compare_type, this_test_limit,
                                          bias_tree);
        }

      /* Create the initial control.  First include all items that
         are within the loop limit.  */
      tree init_ctrl = NULL_TREE;
      if (!first_iteration_full)
        {
          tree start, end;
          if (first_limit == test_limit)
            {
              /* Use a natural test between zero (the initial IV value)
                 and the loop limit.  The "else" block would be valid too,
                 but this choice can avoid the need to load BIAS_TREE into
                 a register.  */
              start = zero_index;
              end = this_test_limit;
            }
          else
            {
              /* FIRST_LIMIT is the maximum number of items handled by the
                 first iteration of the vector loop.  Test the portion
                 associated with this control.  */
              start = bias_tree;
              end = first_limit;
            }

          if (use_masks_p)
            init_ctrl = vect_gen_while (preheader_seq, ctrl_type,
                                        start, end, "max_mask");
          else
            {
              init_ctrl = make_temp_ssa_name (compare_type, NULL, "max_len");
              gimple_seq seq = vect_gen_len (init_ctrl, start,
                                             end, length_limit);
              gimple_seq_add_seq (preheader_seq, seq);
            }
        }

      /* Now AND out the bits that are within the number of skipped
         items.  */
      poly_uint64 const_skip;
      if (nitems_skip
          && !(poly_int_tree_p (nitems_skip, &const_skip)
               && known_le (const_skip, bias)))
        {
          gcc_assert (use_masks_p);
          tree unskipped_mask = vect_gen_while_not (preheader_seq, ctrl_type,
                                                    bias_tree, nitems_skip);
          if (init_ctrl)
            init_ctrl = gimple_build (preheader_seq, BIT_AND_EXPR, ctrl_type,
                                      init_ctrl, unskipped_mask);
          else
            init_ctrl = unskipped_mask;
        }

      if (!init_ctrl)
        {
          /* First iteration is full.  */
          if (use_masks_p)
            init_ctrl = build_minus_one_cst (ctrl_type);
          else
            init_ctrl = length_limit;
        }

      /* Get the control value for the next iteration of the loop.  */
      if (use_masks_p)
        {
          gimple_seq stmts = NULL;
          next_ctrl = vect_gen_while (&stmts, ctrl_type, test_index,
                                      this_test_limit, "next_mask");
          gsi_insert_seq_before (test_gsi, stmts, GSI_SAME_STMT);
        }
      else
        {
          next_ctrl = make_temp_ssa_name (compare_type, NULL, "next_len");
          gimple_seq seq = vect_gen_len (next_ctrl, test_index, this_test_limit,
                                         length_limit);
          gsi_insert_seq_before (test_gsi, seq, GSI_SAME_STMT);
        }

      vect_set_loop_control (loop, ctrl, init_ctrl, next_ctrl);
    }

  int partial_load_bias = LOOP_VINFO_PARTIAL_LOAD_STORE_BIAS (loop_vinfo);
  if (partial_load_bias != 0)
    {
      tree adjusted_len = rgc->bias_adjusted_ctrl;
      gassign *minus = gimple_build_assign (adjusted_len, PLUS_EXPR,
                                            rgc->controls[0],
                                            build_int_cst
                                            (TREE_TYPE (rgc->controls[0]),
                                             partial_load_bias));
      gimple_seq_add_stmt (header_seq, minus);
    }

  return next_ctrl;
}

/* Set up the iteration condition and rgroup controls for LOOP, given
   that LOOP_VINFO_USING_PARTIAL_VECTORS_P is true for the vectorized
   loop.  LOOP_VINFO describes the vectorization of LOOP.  NITERS is
   the number of iterations of the original scalar loop that should be
   handled by the vector loop.  NITERS_MAYBE_ZERO and FINAL_IV are as
   for vect_set_loop_condition.

   Insert the branch-back condition before LOOP_COND_GSI and return the
   final gcond.  */

static gcond *
vect_set_loop_condition_partial_vectors (class loop *loop,
                                         loop_vec_info loop_vinfo, tree niters,
                                         tree final_iv, bool niters_maybe_zero,
                                         gimple_stmt_iterator loop_cond_gsi)
{
  gimple_seq preheader_seq = NULL;
  gimple_seq header_seq = NULL;

  bool use_masks_p = LOOP_VINFO_FULLY_MASKED_P (loop_vinfo);
  tree compare_type = LOOP_VINFO_RGROUP_COMPARE_TYPE (loop_vinfo);
  unsigned int compare_precision = TYPE_PRECISION (compare_type);
  tree orig_niters = niters;

  /* Type of the initial value of NITERS.  */
  tree ni_actual_type = TREE_TYPE (niters);
  unsigned int ni_actual_precision = TYPE_PRECISION (ni_actual_type);
  tree niters_skip = LOOP_VINFO_MASK_SKIP_NITERS (loop_vinfo);

  /* Convert NITERS to the same size as the compare.  */
  if (compare_precision > ni_actual_precision
      && niters_maybe_zero)
    {
      /* We know that there is always at least one iteration, so if the
         count is zero then it must have wrapped.  Cope with this by
         subtracting 1 before the conversion and adding 1 to the result.  */
      gcc_assert (TYPE_UNSIGNED (ni_actual_type));
      niters = gimple_build (&preheader_seq, PLUS_EXPR, ni_actual_type,
                             niters, build_minus_one_cst (ni_actual_type));
      niters = gimple_convert (&preheader_seq, compare_type, niters);
      niters = gimple_build (&preheader_seq, PLUS_EXPR, compare_type,
                             niters, build_one_cst (compare_type));
    }
  else
    niters = gimple_convert (&preheader_seq, compare_type, niters);

  /* Iterate over all the rgroups and fill in their controls.  We could use
     the first control from any rgroup for the loop condition; here we
     arbitrarily pick the last.  */
  tree test_ctrl = NULL_TREE;
  rgroup_controls *rgc;
  unsigned int i;
  auto_vec<rgroup_controls> *controls = use_masks_p
                                          ? &LOOP_VINFO_MASKS (loop_vinfo)
                                          : &LOOP_VINFO_LENS (loop_vinfo);
  FOR_EACH_VEC_ELT (*controls, i, rgc)
    if (!rgc->controls.is_empty ())
      {
        /* First try using permutes.  This adds a single vector
           instruction to the loop for each mask, but needs no extra
           loop invariants or IVs.  */
        unsigned int nmasks = i + 1;
        if (use_masks_p && (nmasks & 1) == 0)
          {
            rgroup_controls *half_rgc = &(*controls)[nmasks / 2 - 1];
            if (!half_rgc->controls.is_empty ()
                && vect_maybe_permute_loop_masks (&header_seq, rgc, half_rgc))
              continue;
          }

        /* See whether zero-based IV would ever generate all-false masks
           or zero length before wrapping around.  */
        bool might_wrap_p = vect_rgroup_iv_might_wrap_p (loop_vinfo, rgc);

        /* Set up all controls for this group.  */
        test_ctrl = vect_set_loop_controls_directly (loop, loop_vinfo,
                                                     &preheader_seq,
                                                     &header_seq,
                                                     loop_cond_gsi, rgc,
                                                     niters, niters_skip,
                                                     might_wrap_p);
      }

  /* Emit all accumulated statements.  */
  add_preheader_seq (loop, preheader_seq);
  add_header_seq (loop, header_seq);

  /* Get a boolean result that tells us whether to iterate.  */
  edge exit_edge = single_exit (loop);
  tree_code code = (exit_edge->flags & EDGE_TRUE_VALUE) ? EQ_EXPR : NE_EXPR;
  tree zero_ctrl = build_zero_cst (TREE_TYPE (test_ctrl));
  gcond *cond_stmt = gimple_build_cond (code, test_ctrl, zero_ctrl,
                                        NULL_TREE, NULL_TREE);
  gsi_insert_before (&loop_cond_gsi, cond_stmt, GSI_SAME_STMT);

  /* The loop iterates (NITERS - 1) / VF + 1 times.
     Subtract one from this to get the latch count.  */
  tree step = build_int_cst (compare_type,
                             LOOP_VINFO_VECT_FACTOR (loop_vinfo));
  tree niters_minus_one = fold_build2 (PLUS_EXPR, compare_type, niters,
                                       build_minus_one_cst (compare_type));
  loop->nb_iterations = fold_build2 (TRUNC_DIV_EXPR, compare_type,
                                     niters_minus_one, step);

  if (final_iv)
    {
      gassign *assign = gimple_build_assign (final_iv, orig_niters);
      gsi_insert_on_edge_immediate (single_exit (loop), assign);
    }

  return cond_stmt;
}

/* Like vect_set_loop_condition, but handle the case in which the vector
   loop handles exactly VF scalars per iteration.  */

static gcond *
vect_set_loop_condition_normal (class loop *loop, tree niters, tree step,
                                tree final_iv, bool niters_maybe_zero,
                                gimple_stmt_iterator loop_cond_gsi)
{
  tree indx_before_incr, indx_after_incr;
  gcond *cond_stmt;
  gcond *orig_cond;
  edge pe = loop_preheader_edge (loop);
  edge exit_edge = single_exit (loop);
  gimple_stmt_iterator incr_gsi;
  bool insert_after;
  enum tree_code code;
  tree niters_type = TREE_TYPE (niters);

  orig_cond = get_loop_exit_condition (loop);
  gcc_assert (orig_cond);
  loop_cond_gsi = gsi_for_stmt (orig_cond);

  tree init, limit;
  if (!niters_maybe_zero && integer_onep (step))
    {
      /* In this case we can use a simple 0-based IV:

         A:
           x = 0;
           do
             {
               ...
               x += 1;
             }
           while (x < NITERS);  */
      code = (exit_edge->flags & EDGE_TRUE_VALUE) ? GE_EXPR : LT_EXPR;
      init = build_zero_cst (niters_type);
      limit = niters;
    }
  else
    {
      /* The following works for all values of NITERS except 0:

         B:
           x = 0;
           do
             {
               ...
               x += STEP;
             }
           while (x <= NITERS - STEP);

         so that the loop continues to iterate if x + STEP - 1 < NITERS
         but stops if x + STEP - 1 >= NITERS.

         However, if NITERS is zero, x never hits a value above NITERS - STEP
         before wrapping around.  There are two obvious ways of dealing with
         this:

         - start at STEP - 1 and compare x before incrementing it
         - start at -1 and compare x after incrementing it

         The latter is simpler and is what we use.  The loop in this case
         looks like:

         C:
           x = -1;
           do
             {
               ...
               x += STEP;
             }
           while (x < NITERS - STEP);

         In both cases the loop limit is NITERS - STEP.  */
      gimple_seq seq = NULL;
      limit = force_gimple_operand (niters, &seq, true, NULL_TREE);
      limit = gimple_build (&seq, MINUS_EXPR, TREE_TYPE (limit), limit, step);
      if (seq)
        {
          basic_block new_bb = gsi_insert_seq_on_edge_immediate (pe, seq);
          gcc_assert (!new_bb);
        }
      if (niters_maybe_zero)
        {
          /* Case C.  */
          code = (exit_edge->flags & EDGE_TRUE_VALUE) ? GE_EXPR : LT_EXPR;
          init = build_all_ones_cst (niters_type);
        }
      else
        {
          /* Case B.  */
          code = (exit_edge->flags & EDGE_TRUE_VALUE) ? GT_EXPR : LE_EXPR;
          init = build_zero_cst (niters_type);
        }
    }

  standard_iv_increment_position (loop, &incr_gsi, &insert_after);
  create_iv (init, step, NULL_TREE, loop,
             &incr_gsi, insert_after, &indx_before_incr, &indx_after_incr);
  indx_after_incr = force_gimple_operand_gsi (&loop_cond_gsi, indx_after_incr,
                                              true, NULL_TREE, true,
                                              GSI_SAME_STMT);
  limit = force_gimple_operand_gsi (&loop_cond_gsi, limit, true, NULL_TREE,
                                     true, GSI_SAME_STMT);

  cond_stmt = gimple_build_cond (code, indx_after_incr, limit, NULL_TREE,
                                 NULL_TREE);

  gsi_insert_before (&loop_cond_gsi, cond_stmt, GSI_SAME_STMT);

  /* Record the number of latch iterations.  */
  if (limit == niters)
    /* Case A: the loop iterates NITERS times.  Subtract one to get the
       latch count.  */
    loop->nb_iterations = fold_build2 (MINUS_EXPR, niters_type, niters,
                                       build_int_cst (niters_type, 1));
  else
    /* Case B or C: the loop iterates (NITERS - STEP) / STEP + 1 times.
       Subtract one from this to get the latch count.  */
    loop->nb_iterations = fold_build2 (TRUNC_DIV_EXPR, niters_type,
                                       limit, step);

  if (final_iv)
    {
      gassign *assign = gimple_build_assign (final_iv, MINUS_EXPR,
                                             indx_after_incr, init);
      gsi_insert_on_edge_immediate (single_exit (loop), assign);
    }

  return cond_stmt;
}

/* If we're using fully-masked loops, make LOOP iterate:

      N == (NITERS - 1) / STEP + 1

   times.  When NITERS is zero, this is equivalent to making the loop
   execute (1 << M) / STEP times, where M is the precision of NITERS.
   NITERS_MAYBE_ZERO is true if this last case might occur.

   If we're not using fully-masked loops, make LOOP iterate:

      N == (NITERS - STEP) / STEP + 1

   times, where NITERS is known to be outside the range [1, STEP - 1].
   This is equivalent to making the loop execute NITERS / STEP times
   when NITERS is nonzero and (1 << M) / STEP times otherwise.
   NITERS_MAYBE_ZERO again indicates whether this last case might occur.

   If FINAL_IV is nonnull, it is an SSA name that should be set to
   N * STEP on exit from the loop.

   Assumption: the exit-condition of LOOP is the last stmt in the loop.  */

void
vect_set_loop_condition (class loop *loop, loop_vec_info loop_vinfo,
                         tree niters, tree step, tree final_iv,
                         bool niters_maybe_zero)
{
  gcond *cond_stmt;
  gcond *orig_cond = get_loop_exit_condition (loop);
  gimple_stmt_iterator loop_cond_gsi = gsi_for_stmt (orig_cond);

  if (loop_vinfo && LOOP_VINFO_USING_PARTIAL_VECTORS_P (loop_vinfo))
    cond_stmt = vect_set_loop_condition_partial_vectors (loop, loop_vinfo,
                                                         niters, final_iv,
                                                         niters_maybe_zero,
                                                         loop_cond_gsi);
  else
    cond_stmt = vect_set_loop_condition_normal (loop, niters, step, final_iv,
                                                niters_maybe_zero,
                                                loop_cond_gsi);

  /* Remove old loop exit test.  */
  stmt_vec_info orig_cond_info;
  if (loop_vinfo
      && (orig_cond_info = loop_vinfo->lookup_stmt (orig_cond)))
    loop_vinfo->remove_stmt (orig_cond_info);
  else
    gsi_remove (&loop_cond_gsi, true);

  if (dump_enabled_p ())
    dump_printf_loc (MSG_NOTE, vect_location, "New loop exit condition: %G",
                     cond_stmt);
}

/* Helper routine of slpeel_tree_duplicate_loop_to_edge_cfg.
   For all PHI arguments in FROM->dest and TO->dest from those
   edges ensure that TO->dest PHI arguments have current_def
   to that in from.  */

static void
slpeel_duplicate_current_defs_from_edges (edge from, edge to)
{
  gimple_stmt_iterator gsi_from, gsi_to;

  for (gsi_from = gsi_start_phis (from->dest),
       gsi_to = gsi_start_phis (to->dest);
       !gsi_end_p (gsi_from) && !gsi_end_p (gsi_to);)
    {
      gimple *from_phi = gsi_stmt (gsi_from);
      gimple *to_phi = gsi_stmt (gsi_to);
      tree from_arg = PHI_ARG_DEF_FROM_EDGE (from_phi, from);
      tree to_arg = PHI_ARG_DEF_FROM_EDGE (to_phi, to);
      if (virtual_operand_p (from_arg))
        {
          gsi_next (&gsi_from);
          continue;
        }
      if (virtual_operand_p (to_arg))
        {
          gsi_next (&gsi_to);
          continue;
        }
      if (TREE_CODE (from_arg) != SSA_NAME)
        gcc_assert (operand_equal_p (from_arg, to_arg, 0));
      else if (TREE_CODE (to_arg) == SSA_NAME
               && from_arg != to_arg)
        {
          if (get_current_def (to_arg) == NULL_TREE)
            {
              gcc_assert (types_compatible_p (TREE_TYPE (to_arg),
                                              TREE_TYPE (get_current_def
                                                           (from_arg))));
              set_current_def (to_arg, get_current_def (from_arg));
            }
        }
      gsi_next (&gsi_from);
      gsi_next (&gsi_to);
    }

  gphi *from_phi = get_virtual_phi (from->dest);
  gphi *to_phi = get_virtual_phi (to->dest);
  if (from_phi)
    set_current_def (PHI_ARG_DEF_FROM_EDGE (to_phi, to),
                     get_current_def (PHI_ARG_DEF_FROM_EDGE (from_phi, from)));
}


/* Given LOOP this function generates a new copy of it and puts it
   on E which is either the entry or exit of LOOP.  If SCALAR_LOOP is
   non-NULL, assume LOOP and SCALAR_LOOP are equivalent and copy the
   basic blocks from SCALAR_LOOP instead of LOOP, but to either the
   entry or exit of LOOP.  */

class loop *
slpeel_tree_duplicate_loop_to_edge_cfg (class loop *loop,
                                        class loop *scalar_loop, edge e)
{
  class loop *new_loop;
  basic_block *new_bbs, *bbs, *pbbs;
  bool at_exit;
  bool was_imm_dom;
  basic_block exit_dest;
  edge exit, new_exit;
  bool duplicate_outer_loop = false;

  exit = single_exit (loop);
  at_exit = (e == exit);
  if (!at_exit && e != loop_preheader_edge (loop))
    return NULL;

  if (scalar_loop == NULL)
    scalar_loop = loop;

  bbs = XNEWVEC (basic_block, scalar_loop->num_nodes + 1);
  pbbs = bbs + 1;
  get_loop_body_with_size (scalar_loop, pbbs, scalar_loop->num_nodes);
  /* Allow duplication of outer loops.  */
  if (scalar_loop->inner)
    duplicate_outer_loop = true;
  /* Check whether duplication is possible.  */
  if (!can_copy_bbs_p (pbbs, scalar_loop->num_nodes))
    {
      free (bbs);
      return NULL;
    }

  /* Generate new loop structure.  */
  new_loop = duplicate_loop (scalar_loop, loop_outer (scalar_loop));
  duplicate_subloops (scalar_loop, new_loop);

  exit_dest = exit->dest;
  was_imm_dom = (get_immediate_dominator (CDI_DOMINATORS,
                                          exit_dest) == loop->header ?
                 true : false);

  /* Also copy the pre-header, this avoids jumping through hoops to
     duplicate the loop entry PHI arguments.  Create an empty
     pre-header unconditionally for this.  */
  basic_block preheader = split_edge (loop_preheader_edge (scalar_loop));
  edge entry_e = single_pred_edge (preheader);
  bbs[0] = preheader;
  new_bbs = XNEWVEC (basic_block, scalar_loop->num_nodes + 1);

  exit = single_exit (scalar_loop);
  copy_bbs (bbs, scalar_loop->num_nodes + 1, new_bbs,
            &exit, 1, &new_exit, NULL,
            at_exit ? loop->latch : e->src, true);
  exit = single_exit (loop);
  basic_block new_preheader = new_bbs[0];

  /* Before installing PHI arguments make sure that the edges
     into them match that of the scalar loop we analyzed.  This
     makes sure the SLP tree matches up between the main vectorized
     loop and the epilogue vectorized copies.  */
  if (single_succ_edge (preheader)->dest_idx
      != single_succ_edge (new_bbs[0])->dest_idx)
    {
      basic_block swap_bb = new_bbs[1];
      gcc_assert (EDGE_COUNT (swap_bb->preds) == 2);
      std::swap (EDGE_PRED (swap_bb, 0), EDGE_PRED (swap_bb, 1));
      EDGE_PRED (swap_bb, 0)->dest_idx = 0;
      EDGE_PRED (swap_bb, 1)->dest_idx = 1;
    }
  if (duplicate_outer_loop)
    {
      class loop *new_inner_loop = get_loop_copy (scalar_loop->inner);
      if (loop_preheader_edge (scalar_loop)->dest_idx
          != loop_preheader_edge (new_inner_loop)->dest_idx)
        {
          basic_block swap_bb = new_inner_loop->header;
          gcc_assert (EDGE_COUNT (swap_bb->preds) == 2);
          std::swap (EDGE_PRED (swap_bb, 0), EDGE_PRED (swap_bb, 1));
          EDGE_PRED (swap_bb, 0)->dest_idx = 0;
          EDGE_PRED (swap_bb, 1)->dest_idx = 1;
        }
    }

  add_phi_args_after_copy (new_bbs, scalar_loop->num_nodes + 1, NULL);

  /* Skip new preheader since it's deleted if copy loop is added at entry.  */
  for (unsigned i = (at_exit ? 0 : 1); i < scalar_loop->num_nodes + 1; i++)
    rename_variables_in_bb (new_bbs[i], duplicate_outer_loop);

  if (scalar_loop != loop)
    {
      /* If we copied from SCALAR_LOOP rather than LOOP, SSA_NAMEs from
         SCALAR_LOOP will have current_def set to SSA_NAMEs in the new_loop,
         but LOOP will not.  slpeel_update_phi_nodes_for_guard{1,2} expects
         the LOOP SSA_NAMEs (on the exit edge and edge from latch to
         header) to have current_def set, so copy them over.  */
      slpeel_duplicate_current_defs_from_edges (single_exit (scalar_loop),
                                                exit);
      slpeel_duplicate_current_defs_from_edges (EDGE_SUCC (scalar_loop->latch,
                                                           0),
                                                EDGE_SUCC (loop->latch, 0));
    }

  if (at_exit) /* Add the loop copy at exit.  */
    {
      if (scalar_loop != loop)
        {
          gphi_iterator gsi;
          new_exit = redirect_edge_and_branch (new_exit, exit_dest);

          for (gsi = gsi_start_phis (exit_dest); !gsi_end_p (gsi);
               gsi_next (&gsi))
            {
              gphi *phi = gsi.phi ();
              tree orig_arg = PHI_ARG_DEF_FROM_EDGE (phi, e);
              location_t orig_locus
                = gimple_phi_arg_location_from_edge (phi, e);

              add_phi_arg (phi, orig_arg, new_exit, orig_locus);
            }
        }
      redirect_edge_and_branch_force (e, new_preheader);
      flush_pending_stmts (e);
      set_immediate_dominator (CDI_DOMINATORS, new_preheader, e->src);
      if (was_imm_dom || duplicate_outer_loop)
        set_immediate_dominator (CDI_DOMINATORS, exit_dest, new_exit->src);

      /* And remove the non-necessary forwarder again.  Keep the other
         one so we have a proper pre-header for the loop at the exit edge.  */
      redirect_edge_pred (single_succ_edge (preheader),
                          single_pred (preheader));
      delete_basic_block (preheader);
      set_immediate_dominator (CDI_DOMINATORS, scalar_loop->header,
                               loop_preheader_edge (scalar_loop)->src);
    }
  else /* Add the copy at entry.  */
    {
      if (scalar_loop != loop)
        {
          /* Remove the non-necessary forwarder of scalar_loop again.  */
          redirect_edge_pred (single_succ_edge (preheader),
                              single_pred (preheader));
          delete_basic_block (preheader);
          set_immediate_dominator (CDI_DOMINATORS, scalar_loop->header,
                                   loop_preheader_edge (scalar_loop)->src);
          preheader = split_edge (loop_preheader_edge (loop));
          entry_e = single_pred_edge (preheader);
        }

      redirect_edge_and_branch_force (entry_e, new_preheader);
      flush_pending_stmts (entry_e);
      set_immediate_dominator (CDI_DOMINATORS, new_preheader, entry_e->src);

      redirect_edge_and_branch_force (new_exit, preheader);
      flush_pending_stmts (new_exit);
      set_immediate_dominator (CDI_DOMINATORS, preheader, new_exit->src);

      /* And remove the non-necessary forwarder again.  Keep the other
         one so we have a proper pre-header for the loop at the exit edge.  */
      redirect_edge_pred (single_succ_edge (new_preheader),
                          single_pred (new_preheader));
      delete_basic_block (new_preheader);
      set_immediate_dominator (CDI_DOMINATORS, new_loop->header,
                               loop_preheader_edge (new_loop)->src);
    }

  if (scalar_loop != loop)
    {
      /* Update new_loop->header PHIs, so that on the preheader
         edge they are the ones from loop rather than scalar_loop.  */
      gphi_iterator gsi_orig, gsi_new;
      edge orig_e = loop_preheader_edge (loop);
      edge new_e = loop_preheader_edge (new_loop);

      for (gsi_orig = gsi_start_phis (loop->header),
           gsi_new = gsi_start_phis (new_loop->header);
           !gsi_end_p (gsi_orig) && !gsi_end_p (gsi_new);
           gsi_next (&gsi_orig), gsi_next (&gsi_new))
        {
          gphi *orig_phi = gsi_orig.phi ();
          gphi *new_phi = gsi_new.phi ();
          tree orig_arg = PHI_ARG_DEF_FROM_EDGE (orig_phi, orig_e);
          location_t orig_locus
            = gimple_phi_arg_location_from_edge (orig_phi, orig_e);

          add_phi_arg (new_phi, orig_arg, new_e, orig_locus);
        }
    }

  free (new_bbs);
  free (bbs);

  checking_verify_dominators (CDI_DOMINATORS);

  return new_loop;
}


/* Given the condition expression COND, put it as the last statement of
   GUARD_BB; set both edges' probability; set dominator of GUARD_TO to
   DOM_BB; return the skip edge.  GUARD_TO is the target basic block to
   skip the loop.  PROBABILITY is the skip edge's probability.  Mark the
   new edge as irreducible if IRREDUCIBLE_P is true.  */

static edge
slpeel_add_loop_guard (basic_block guard_bb, tree cond,
                       basic_block guard_to, basic_block dom_bb,
                       profile_probability probability, bool irreducible_p)
{
  gimple_stmt_iterator gsi;
  edge new_e, enter_e;
  gcond *cond_stmt;
  gimple_seq gimplify_stmt_list = NULL;

  enter_e = EDGE_SUCC (guard_bb, 0);
  enter_e->flags &= ~EDGE_FALLTHRU;
  enter_e->flags |= EDGE_FALSE_VALUE;
  gsi = gsi_last_bb (guard_bb);

  cond = force_gimple_operand_1 (cond, &gimplify_stmt_list, is_gimple_condexpr,
                                 NULL_TREE);
  if (gimplify_stmt_list)
    gsi_insert_seq_after (&gsi, gimplify_stmt_list, GSI_NEW_STMT);

  cond_stmt = gimple_build_cond_from_tree (cond, NULL_TREE, NULL_TREE);
  gsi = gsi_last_bb (guard_bb);
  gsi_insert_after (&gsi, cond_stmt, GSI_NEW_STMT);

  /* Add new edge to connect guard block to the merge/loop-exit block.  */
  new_e = make_edge (guard_bb, guard_to, EDGE_TRUE_VALUE);

  new_e->probability = probability;
  if (irreducible_p)
    new_e->flags |= EDGE_IRREDUCIBLE_LOOP;

  enter_e->probability = probability.invert ();
  set_immediate_dominator (CDI_DOMINATORS, guard_to, dom_bb);

  /* Split enter_e to preserve LOOPS_HAVE_PREHEADERS.  */
  if (enter_e->dest->loop_father->header == enter_e->dest)
    split_edge (enter_e);

  return new_e;
}


/* This function verifies that the following restrictions apply to LOOP:
   (1) it consists of exactly 2 basic blocks - header, and an empty latch
       for innermost loop and 5 basic blocks for outer-loop.
   (2) it is single entry, single exit
   (3) its exit condition is the last stmt in the header
   (4) E is the entry/exit edge of LOOP.
 */

bool
slpeel_can_duplicate_loop_p (const class loop *loop, const_edge e)
{
  edge exit_e = single_exit (loop);
  edge entry_e = loop_preheader_edge (loop);
  gcond *orig_cond = get_loop_exit_condition (loop);
  gimple_stmt_iterator loop_exit_gsi = gsi_last_bb (exit_e->src);
  unsigned int num_bb = loop->inner? 5 : 2;

  /* All loops have an outer scope; the only case loop->outer is NULL is for
     the function itself.  */
  if (!loop_outer (loop)
      || loop->num_nodes != num_bb
      || !empty_block_p (loop->latch)
      || !single_exit (loop)
      /* Verify that new loop exit condition can be trivially modified.  */
      || (!orig_cond || orig_cond != gsi_stmt (loop_exit_gsi))
      || (e != exit_e && e != entry_e))
    return false;

  return true;
}

/* If the loop has a virtual PHI, but exit bb doesn't, create a virtual PHI
   in the exit bb and rename all the uses after the loop.  This simplifies
   the *guard[12] routines, which assume loop closed SSA form for all PHIs
   (but normally loop closed SSA form doesn't require virtual PHIs to be
   in the same form).  Doing this early simplifies the checking what
   uses should be renamed.

   If we create a new phi after the loop, return the definition that
   applies on entry to the loop, otherwise return null.  */

static tree
create_lcssa_for_virtual_phi (class loop *loop)
{
  gphi_iterator gsi;
  edge exit_e = single_exit (loop);

  for (gsi = gsi_start_phis (loop->header); !gsi_end_p (gsi); gsi_next (&gsi))
    if (virtual_operand_p (gimple_phi_result (gsi_stmt (gsi))))
      {
        gphi *phi = gsi.phi ();
        for (gsi = gsi_start_phis (exit_e->dest);
             !gsi_end_p (gsi); gsi_next (&gsi))
          if (virtual_operand_p (gimple_phi_result (gsi_stmt (gsi))))
            break;
        if (gsi_end_p (gsi))
          {
            tree new_vop = copy_ssa_name (PHI_RESULT (phi));
            gphi *new_phi = create_phi_node (new_vop, exit_e->dest);
            tree vop = PHI_ARG_DEF_FROM_EDGE (phi, EDGE_SUCC (loop->latch, 0));
            imm_use_iterator imm_iter;
            gimple *stmt;
            use_operand_p use_p;

            SSA_NAME_OCCURS_IN_ABNORMAL_PHI (new_vop)
              = SSA_NAME_OCCURS_IN_ABNORMAL_PHI (vop);
            add_phi_arg (new_phi, vop, exit_e, UNKNOWN_LOCATION);
            gimple_phi_set_result (new_phi, new_vop);
            FOR_EACH_IMM_USE_STMT (stmt, imm_iter, vop)
              if (stmt != new_phi
                  && !flow_bb_inside_loop_p (loop, gimple_bb (stmt)))
                FOR_EACH_IMM_USE_ON_STMT (use_p, imm_iter)
                  SET_USE (use_p, new_vop);

            return PHI_ARG_DEF_FROM_EDGE (phi, loop_preheader_edge (loop));
          }
        break;
      }
  return NULL_TREE;
}

/* Function vect_get_loop_location.

   Extract the location of the loop in the source code.
   If the loop is not well formed for vectorization, an estimated
   location is calculated.
   Return the loop location if succeed and NULL if not.  */

dump_user_location_t
find_loop_location (class loop *loop)
{
  gimple *stmt = NULL;
  basic_block bb;
  gimple_stmt_iterator si;

  if (!loop)
    return dump_user_location_t ();

  stmt = get_loop_exit_condition (loop);

  if (stmt
      && LOCATION_LOCUS (gimple_location (stmt)) > BUILTINS_LOCATION)
    return stmt;

  /* If we got here the loop is probably not "well formed",
     try to estimate the loop location */

  if (!loop->header)
    return dump_user_location_t ();

  bb = loop->header;

  for (si = gsi_start_bb (bb); !gsi_end_p (si); gsi_next (&si))
    {
      stmt = gsi_stmt (si);
      if (LOCATION_LOCUS (gimple_location (stmt)) > BUILTINS_LOCATION)
        return stmt;
    }

  return dump_user_location_t ();
}

/* Return true if the phi described by STMT_INFO defines an IV of the
   loop to be vectorized.  */

static bool
iv_phi_p (stmt_vec_info stmt_info)
{
  gphi *phi = as_a <gphi *> (stmt_info->stmt);
  if (virtual_operand_p (PHI_RESULT (phi)))
    return false;

  if (STMT_VINFO_DEF_TYPE (stmt_info) == vect_reduction_def
      || STMT_VINFO_DEF_TYPE (stmt_info) == vect_double_reduction_def)
    return false;

  return true;
}

/* Function vect_can_advance_ivs_p

   In case the number of iterations that LOOP iterates is unknown at compile
   time, an epilog loop will be generated, and the loop induction variables
   (IVs) will be "advanced" to the value they are supposed to take just before
   the epilog loop.  Here we check that the access function of the loop IVs
   and the expression that represents the loop bound are simple enough.
   These restrictions will be relaxed in the future.  */

bool
vect_can_advance_ivs_p (loop_vec_info loop_vinfo)
{
  class loop *loop = LOOP_VINFO_LOOP (loop_vinfo);
  basic_block bb = loop->header;
  gphi_iterator gsi;

  /* Analyze phi functions of the loop header.  */

  if (dump_enabled_p ())
    dump_printf_loc (MSG_NOTE, vect_location, "vect_can_advance_ivs_p:\n");
  for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
    {
      tree evolution_part;

      gphi *phi = gsi.phi ();
      stmt_vec_info phi_info = loop_vinfo->lookup_stmt (phi);
      if (dump_enabled_p ())
        dump_printf_loc (MSG_NOTE, vect_location, "Analyze phi: %G",
                         phi_info->stmt);

      /* Skip virtual phi's. The data dependences that are associated with
         virtual defs/uses (i.e., memory accesses) are analyzed elsewhere.

         Skip reduction phis.  */
      if (!iv_phi_p (phi_info))
        {
          if (dump_enabled_p ())
            dump_printf_loc (MSG_NOTE, vect_location,
                             "reduc or virtual phi. skip.\n");
          continue;
        }

      /* Analyze the evolution function.  */

      evolution_part = STMT_VINFO_LOOP_PHI_EVOLUTION_PART (phi_info);
      if (evolution_part == NULL_TREE)
        {
          if (dump_enabled_p ())
            dump_printf (MSG_MISSED_OPTIMIZATION,
                         "No access function or evolution.\n");
          return false;
        }

      /* FORNOW: We do not transform initial conditions of IVs
         which evolution functions are not invariants in the loop.  */

      if (!expr_invariant_in_loop_p (loop, evolution_part))
        {
          if (dump_enabled_p ())
            dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                             "evolution not invariant in loop.\n");
          return false;
        }

      /* FORNOW: We do not transform initial conditions of IVs
         which evolution functions are a polynomial of degree >= 2.  */

      if (tree_is_chrec (evolution_part))
        {
          if (dump_enabled_p ())
            dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
                             "evolution is chrec.\n");
          return false;
        }
    }

  return true;
}


/*   Function vect_update_ivs_after_vectorizer.

     "Advance" the induction variables of LOOP to the value they should take
     after the execution of LOOP.  This is currently necessary because the
     vectorizer does not handle induction variables that are used after the
     loop.  Such a situation occurs when the last iterations of LOOP are
     peeled, because:
     1. We introduced new uses after LOOP for IVs that were not originally used
        after LOOP: the IVs of LOOP are now used by an epilog loop.
     2. LOOP is going to be vectorized; this means that it will iterate N/VF
        times, whereas the loop IVs should be bumped N times.

     Input:
     - LOOP - a loop that is going to be vectorized. The last few iterations
              of LOOP were peeled.
     - NITERS - the number of iterations that LOOP executes (before it is
                vectorized). i.e, the number of times the ivs should be bumped.
     - UPDATE_E - a successor edge of LOOP->exit that is on the (only) path
                  coming out from LOOP on which there are uses of the LOOP ivs
                  (this is the path from LOOP->exit to epilog_loop->preheader).

                  The new definitions of the ivs are placed in LOOP->exit.
                  The phi args associated with the edge UPDATE_E in the bb
                  UPDATE_E->dest are updated accordingly.

     Assumption 1: Like the rest of the vectorizer, this function assumes
     a single loop exit that has a single predecessor.

     Assumption 2: The phi nodes in the LOOP header and in update_bb are
     organized in the same order.

     Assumption 3: The access function of the ivs is simple enough (see
     vect_can_advance_ivs_p).  This assumption will be relaxed in the future.

     Assumption 4: Exactly one of the successors of LOOP exit-bb is on a path
     coming out of LOOP on which the ivs of LOOP are used (this is the path
     that leads to the epilog loop; other paths skip the epilog loop).  This
     path starts with the edge UPDATE_E, and its destination (denoted update_bb)
     needs to have its phis updated.
 */

static void
vect_update_ivs_after_vectorizer (loop_vec_info loop_vinfo,
                                  tree niters, edge update_e)
{
  gphi_iterator gsi, gsi1;
  class loop *loop = LOOP_VINFO_LOOP (loop_vinfo);
  basic_block update_bb = update_e->dest;
  basic_block exit_bb = single_exit (loop)->dest;

  /* Make sure there exists a single-predecessor exit bb:  */
  gcc_assert (single_pred_p (exit_bb));
  gcc_assert (single_succ_edge (exit_bb) == update_e);

  for (gsi = gsi_start_phis (loop->header), gsi1 = gsi_start_phis (update_bb);
       !gsi_end_p (gsi) && !gsi_end_p (gsi1);
       gsi_next (&gsi), gsi_next (&gsi1))
    {
      tree init_expr;
      tree step_expr, off;
      tree type;
      tree var, ni, ni_name;
      gimple_stmt_iterator last_gsi;

      gphi *phi = gsi.phi ();
      gphi *phi1 = gsi1.phi ();
      stmt_vec_info phi_info = loop_vinfo->lookup_stmt (phi);
      if (dump_enabled_p ())
        dump_printf_loc (MSG_NOTE, vect_location,
                         "vect_update_ivs_after_vectorizer: phi: %G", phi);

      /* Skip reduction and virtual phis.  */
      if (!iv_phi_p (phi_info))
        {
          if (dump_enabled_p ())
            dump_printf_loc (MSG_NOTE, vect_location,
                             "reduc or virtual phi. skip.\n");
          continue;
        }

      type = TREE_TYPE (gimple_phi_result (phi));
      step_expr = STMT_VINFO_LOOP_PHI_EVOLUTION_PART (phi_info);
      step_expr = unshare_expr (step_expr);

      /* FORNOW: We do not support IVs whose evolution function is a polynomial
         of degree >= 2 or exponential.  */
      gcc_assert (!tree_is_chrec (step_expr));

      init_expr = PHI_ARG_DEF_FROM_EDGE (phi, loop_preheader_edge (loop));

      off = fold_build2 (MULT_EXPR, TREE_TYPE (step_expr),
                         fold_convert (TREE_TYPE (step_expr), niters),
                         step_expr);
      if (POINTER_TYPE_P (type))
        ni = fold_build_pointer_plus (init_expr, off);
      else
        ni = fold_build2 (PLUS_EXPR, type,
                          init_expr, fold_convert (type, off));

      var = create_tmp_var (type, "tmp");

      last_gsi = gsi_last_bb (exit_bb);
      gimple_seq new_stmts = NULL;
      ni_name = force_gimple_operand (ni, &new_stmts, false, var);
      /* Exit_bb shouldn't be empty.  */
      if (!gsi_end_p (last_gsi))
        gsi_insert_seq_after (&last_gsi, new_stmts, GSI_SAME_STMT);
      else
        gsi_insert_seq_before (&last_gsi, new_stmts, GSI_SAME_STMT);

      /* Fix phi expressions in the successor bb.  */
      adjust_phi_and_debug_stmts (phi1, update_e, ni_name);
    }
}

/* Return a gimple value containing the misalignment (measured in vector
   elements) for the loop described by LOOP_VINFO, i.e. how many elements
   it is away from a perfectly aligned address.  Add any new statements
   to SEQ.  */

static tree
get_misalign_in_elems (gimple **seq, loop_vec_info loop_vinfo)
{
  dr_vec_info *dr_info = LOOP_VINFO_UNALIGNED_DR (loop_vinfo);
  stmt_vec_info stmt_info = dr_info->stmt;
  tree vectype = STMT_VINFO_VECTYPE (stmt_info);

  poly_uint64 target_align = DR_TARGET_ALIGNMENT (dr_info);
  unsigned HOST_WIDE_INT target_align_c;
  tree target_align_minus_1;

  bool negative = tree_int_cst_compare (DR_STEP (dr_info->dr),
                                        size_zero_node) < 0;
  tree offset = (negative
                 ? size_int ((-TYPE_VECTOR_SUBPARTS (vectype) + 1)
                             * TREE_INT_CST_LOW
                                 (TYPE_SIZE_UNIT (TREE_TYPE (vectype))))
                 : size_zero_node);
  tree start_addr = vect_create_addr_base_for_vector_ref (loop_vinfo,
                                                          stmt_info, seq,
                                                          offset);
  tree type = unsigned_type_for (TREE_TYPE (start_addr));
  if (target_align.is_constant (&target_align_c))
    target_align_minus_1 = build_int_cst (type, target_align_c - 1);
  else
    {
      tree vla = build_int_cst (type, target_align);
      tree vla_align = fold_build2 (BIT_AND_EXPR, type, vla,
                                    fold_build2 (MINUS_EXPR, type,
                                                 build_int_cst (type, 0), vla));
      target_align_minus_1 = fold_build2 (MINUS_EXPR, type, vla_align,
                                          build_int_cst (type, 1));
    }

  HOST_WIDE_INT elem_size
    = int_cst_value (TYPE_SIZE_UNIT (TREE_TYPE (vectype)));
  tree elem_size_log = build_int_cst (type, exact_log2 (elem_size));

  /* Create:  misalign_in_bytes = addr & (target_align - 1).  */
  tree int_start_addr = fold_convert (type, start_addr);
  tree misalign_in_bytes = fold_build2 (BIT_AND_EXPR, type, int_start_addr,
                                        target_align_minus_1);

  /* Create:  misalign_in_elems = misalign_in_bytes / element_size.  */
  tree misalign_in_elems = fold_build2 (RSHIFT_EXPR, type, misalign_in_bytes,
                                        elem_size_log);

  return misalign_in_elems;
}

/* Function vect_gen_prolog_loop_niters

   Generate the number of iterations which should be peeled as prolog for the
   loop represented by LOOP_VINFO.  It is calculated as the misalignment of
   DR - the data reference recorded in LOOP_VINFO_UNALIGNED_DR (LOOP_VINFO).
   As a result, after the execution of this loop, the data reference DR will
   refer to an aligned location.  The following computation is generated:

   If the misalignment of DR is known at compile time:
     addr_mis = int mis = DR_MISALIGNMENT (dr);
   Else, compute address misalignment in bytes:
     addr_mis = addr & (target_align - 1)

   prolog_niters = ((VF - addr_mis/elem_size)&(VF-1))/step

   (elem_size = element type size; an element is the scalar element whose type
   is the inner type of the vectype)

   The computations will be emitted at the end of BB.  We also compute and
   store upper bound (included) of the result in BOUND.

   When the step of the data-ref in the loop is not 1 (as in interleaved data
   and SLP), the number of iterations of the prolog must be divided by the step
   (which is equal to the size of interleaved group).

   The above formulas assume that VF == number of elements in the vector. This
   may not hold when there are multiple-types in the loop.
   In this case, for some data-references in the loop the VF does not represent
   the number of elements that fit in the vector.  Therefore, instead of VF we
   use TYPE_VECTOR_SUBPARTS.  */

static tree
vect_gen_prolog_loop_niters (loop_vec_info loop_vinfo,
                             basic_block bb, int *bound)
{
  dr_vec_info *dr_info = LOOP_VINFO_UNALIGNED_DR (loop_vinfo);
  tree var;
  tree niters_type = TREE_TYPE (LOOP_VINFO_NITERS (loop_vinfo));
  gimple_seq stmts = NULL, new_stmts = NULL;
  tree iters, iters_name;
  stmt_vec_info stmt_info = dr_info->stmt;
  tree vectype = STMT_VINFO_VECTYPE (stmt_info);
  poly_uint64 target_align = DR_TARGET_ALIGNMENT (dr_info);

  if (LOOP_VINFO_PEELING_FOR_ALIGNMENT (loop_vinfo) > 0)
    {
      int npeel = LOOP_VINFO_PEELING_FOR_ALIGNMENT (loop_vinfo);

      if (dump_enabled_p ())
        dump_printf_loc (MSG_NOTE, vect_location,
                         "known peeling = %d.\n", npeel);

      iters = build_int_cst (niters_type, npeel);
      *bound = LOOP_VINFO_PEELING_FOR_ALIGNMENT (loop_vinfo);
    }
  else
    {
      tree misalign_in_elems = get_misalign_in_elems (&stmts, loop_vinfo);
      tree type = TREE_TYPE (misalign_in_elems);
      HOST_WIDE_INT elem_size
        = int_cst_value (TYPE_SIZE_UNIT (TREE_TYPE (vectype)));
      /* We only do prolog peeling if the target alignment is known at compile
         time.  */
      poly_uint64 align_in_elems =
        exact_div (target_align, elem_size);
      tree align_in_elems_minus_1 =
        build_int_cst (type, align_in_elems - 1);
      tree align_in_elems_tree = build_int_cst (type, align_in_elems);

      /* Create:  (niters_type) ((align_in_elems - misalign_in_elems)
                                 & (align_in_elems - 1)).  */
      bool negative = tree_int_cst_compare (DR_STEP (dr_info->dr),
                                            size_zero_node) < 0;
      if (negative)
        iters = fold_build2 (MINUS_EXPR, type, misalign_in_elems,
                             align_in_elems_tree);
      else
        iters = fold_build2 (MINUS_EXPR, type, align_in_elems_tree,
                             misalign_in_elems);
      iters = fold_build2 (BIT_AND_EXPR, type, iters, align_in_elems_minus_1);
      iters = fold_convert (niters_type, iters);
      unsigned HOST_WIDE_INT align_in_elems_c;
      if (align_in_elems.is_constant (&align_in_elems_c))
        *bound = align_in_elems_c - 1;
      else
        *bound = -1;
    }

  if (dump_enabled_p ())
    dump_printf_loc (MSG_NOTE, vect_location,
                     "niters for prolog loop: %T\n", iters);

  var = create_tmp_var (niters_type, "prolog_loop_niters");
  iters_name = force_gimple_operand (iters, &new_stmts, false, var);

  if (new_stmts)
    gimple_seq_add_seq (&stmts, new_stmts);
  if (stmts)
    {
      gcc_assert (single_succ_p (bb));
      gimple_stmt_iterator gsi = gsi_last_bb (bb);
      if (gsi_end_p (gsi))
        gsi_insert_seq_before (&gsi, stmts, GSI_SAME_STMT);
      else
        gsi_insert_seq_after (&gsi, stmts, GSI_SAME_STMT);
    }
  return iters_name;
}


/* Function vect_update_init_of_dr

   If CODE is PLUS, the vector loop starts NITERS iterations after the
   scalar one, otherwise CODE is MINUS and the vector loop starts NITERS
   iterations before the scalar one (using masking to skip inactive
   elements).  This function updates the information recorded in DR to
   account for the difference.  Specifically, it updates the OFFSET
   field of DR_INFO.  */

static void
vect_update_init_of_dr (dr_vec_info *dr_info, tree niters, tree_code code)
{
  struct data_reference *dr = dr_info->dr;
  tree offset = dr_info->offset;
  if (!offset)
    offset = build_zero_cst (sizetype);

  niters = fold_build2 (MULT_EXPR, sizetype,
                        fold_convert (sizetype, niters),
                        fold_convert (sizetype, DR_STEP (dr)));
  offset = fold_build2 (code, sizetype,
                        fold_convert (sizetype, offset), niters);
  dr_info->offset = offset;
}


/* Function vect_update_inits_of_drs

   Apply vect_update_inits_of_dr to all accesses in LOOP_VINFO.
   CODE and NITERS are as for vect_update_inits_of_dr.  */

void
vect_update_inits_of_drs (loop_vec_info loop_vinfo, tree niters,
                          tree_code code)
{
  unsigned int i;
  vec<data_reference_p> datarefs = LOOP_VINFO_DATAREFS (loop_vinfo);
  struct data_reference *dr;

  DUMP_VECT_SCOPE ("vect_update_inits_of_dr");

  /* Adjust niters to sizetype.  We used to insert the stmts on loop preheader
     here, but since we might use these niters to update the epilogues niters
     and data references we can't insert them here as this definition might not
     always dominate its uses.  */
  if (!types_compatible_p (sizetype, TREE_TYPE (niters)))
    niters = fold_convert (sizetype, niters);

  FOR_EACH_VEC_ELT (datarefs, i, dr)
    {
      dr_vec_info *dr_info = loop_vinfo->lookup_dr (dr);
      if (!STMT_VINFO_GATHER_SCATTER_P (dr_info->stmt)
          && !STMT_VINFO_SIMD_LANE_ACCESS_P (dr_info->stmt))
        vect_update_init_of_dr (dr_info, niters, code);
    }
}

/* For the information recorded in LOOP_VINFO prepare the loop for peeling
   by masking.  This involves calculating the number of iterations to
   be peeled and then aligning all memory references appropriately.  */

void
vect_prepare_for_masked_peels (loop_vec_info loop_vinfo)
{
  tree misalign_in_elems;
  tree type = LOOP_VINFO_RGROUP_COMPARE_TYPE (loop_vinfo);

  gcc_assert (vect_use_loop_mask_for_alignment_p (loop_vinfo));

  /* From the information recorded in LOOP_VINFO get the number of iterations
     that need to be skipped via masking.  */
  if (LOOP_VINFO_PEELING_FOR_ALIGNMENT (loop_vinfo) > 0)
    {
      poly_int64 misalign = (LOOP_VINFO_VECT_FACTOR (loop_vinfo)
                             - LOOP_VINFO_PEELING_FOR_ALIGNMENT (loop_vinfo));
      misalign_in_elems = build_int_cst (type, misalign);
    }
  else
    {
      gimple_seq seq1 = NULL, seq2 = NULL;
      misalign_in_elems = get_misalign_in_elems (&seq1, loop_vinfo);
      misalign_in_elems = fold_convert (type, misalign_in_elems);
      misalign_in_elems = force_gimple_operand (misalign_in_elems,
                                                &seq2, true, NULL_TREE);
      gimple_seq_add_seq (&seq1, seq2);
      if (seq1)
        {
          edge pe = loop_preheader_edge (LOOP_VINFO_LOOP (loop_vinfo));
          basic_block new_bb = gsi_insert_seq_on_edge_immediate (pe, seq1);
          gcc_assert (!new_bb);
        }
    }

  if (dump_enabled_p ())
    dump_printf_loc (MSG_NOTE, vect_location,
                     "misalignment for fully-masked loop: %T\n",
                     misalign_in_elems);

  LOOP_VINFO_MASK_SKIP_NITERS (loop_vinfo) = misalign_in_elems;

  vect_update_inits_of_drs (loop_vinfo, misalign_in_elems, MINUS_EXPR);
}

/* This function builds ni_name = number of iterations.  Statements
   are emitted on the loop preheader edge.  If NEW_VAR_P is not NULL, set
   it to TRUE if new ssa_var is generated.  */

tree
vect_build_loop_niters (loop_vec_info loop_vinfo, bool *new_var_p)
{
  tree ni = unshare_expr (LOOP_VINFO_NITERS (loop_vinfo));
  if (TREE_CODE (ni) == INTEGER_CST)
    return ni;
  else
    {
      tree ni_name, var;
      gimple_seq stmts = NULL;
      edge pe = loop_preheader_edge (LOOP_VINFO_LOOP (loop_vinfo));

      var = create_tmp_var (TREE_TYPE (ni), "niters");
      ni_name = force_gimple_operand (ni, &stmts, false, var);
      if (stmts)
        {
          gsi_insert_seq_on_edge_immediate (pe, stmts);
          if (new_var_p != NULL)
            *new_var_p = true;
        }

      return ni_name;
    }
}

/* Calculate the number of iterations above which vectorized loop will be
   preferred than scalar loop.  NITERS_PROLOG is the number of iterations
   of prolog loop.  If it's integer const, the integer number is also passed
   in INT_NITERS_PROLOG.  BOUND_PROLOG is the upper bound (inclusive) of the
   number of iterations of the prolog loop.  BOUND_EPILOG is the corresponding
   value for the epilog loop.  If CHECK_PROFITABILITY is true, TH is the
   threshold below which the scalar (rather than vectorized) loop will be
   executed.  This function stores the upper bound (inclusive) of the result
   in BOUND_SCALAR.  */

static tree
vect_gen_scalar_loop_niters (tree niters_prolog, int int_niters_prolog,
                             int bound_prolog, poly_int64 bound_epilog, int th,
                             poly_uint64 *bound_scalar,
                             bool check_profitability)
{
  tree type = TREE_TYPE (niters_prolog);
  tree niters = fold_build2 (PLUS_EXPR, type, niters_prolog,
                             build_int_cst (type, bound_epilog));

  *bound_scalar = bound_prolog + bound_epilog;
  if (check_profitability)
    {
      /* TH indicates the minimum niters of vectorized loop, while we
         compute the maximum niters of scalar loop.  */
      th--;
      /* Peeling for constant times.  */
      if (int_niters_prolog >= 0)
        {
          *bound_scalar = upper_bound (int_niters_prolog + bound_epilog, th);
          return build_int_cst (type, *bound_scalar);
        }
      /* Peeling an unknown number of times.  Note that both BOUND_PROLOG
         and BOUND_EPILOG are inclusive upper bounds.  */
      if (known_ge (th, bound_prolog + bound_epilog))
        {
          *bound_scalar = th;
          return build_int_cst (type, th);
        }
      /* Need to do runtime comparison.  */
      else if (maybe_gt (th, bound_epilog))
        {
          *bound_scalar = upper_bound (*bound_scalar, th);
          return fold_build2 (MAX_EXPR, type,
                              build_int_cst (type, th), niters);
        }
    }
  return niters;
}

/* NITERS is the number of times that the original scalar loop executes
   after peeling.  Work out the maximum number of iterations N that can
   be handled by the vectorized form of the loop and then either:

   a) set *STEP_VECTOR_PTR to the vectorization factor and generate:

        niters_vector = N

   b) set *STEP_VECTOR_PTR to one and generate:

        niters_vector = N / vf

   In both cases, store niters_vector in *NITERS_VECTOR_PTR and add
   any new statements on the loop preheader edge.  NITERS_NO_OVERFLOW
   is true if NITERS doesn't overflow (i.e. if NITERS is always nonzero).  */

void
vect_gen_vector_loop_niters (loop_vec_info loop_vinfo, tree niters,
                             tree *niters_vector_ptr, tree *step_vector_ptr,
                             bool niters_no_overflow)
{
  tree ni_minus_gap, var;
  tree niters_vector, step_vector, type = TREE_TYPE (niters);
  poly_uint64 vf = LOOP_VINFO_VECT_FACTOR (loop_vinfo);
  edge pe = loop_preheader_edge (LOOP_VINFO_LOOP (loop_vinfo));
  tree log_vf = NULL_TREE;

  /* If epilogue loop is required because of data accesses with gaps, we
     subtract one iteration from the total number of iterations here for
     correct calculation of RATIO.  */
  if (LOOP_VINFO_PEELING_FOR_GAPS (loop_vinfo))
    {
      ni_minus_gap = fold_build2 (MINUS_EXPR, type, niters,
                                  build_one_cst (type));
      if (!is_gimple_val (ni_minus_gap))
        {
          var = create_tmp_var (type, "ni_gap");
          gimple *stmts = NULL;
          ni_minus_gap = force_gimple_operand (ni_minus_gap, &stmts,
                                               true, var);
          gsi_insert_seq_on_edge_immediate (pe, stmts);
        }
    }
  else
    ni_minus_gap = niters;

  unsigned HOST_WIDE_INT const_vf;
  if (vf.is_constant (&const_vf)
      && !LOOP_VINFO_USING_PARTIAL_VECTORS_P (loop_vinfo))
    {
      /* Create: niters >> log2(vf) */
      /* If it's known that niters == number of latch executions + 1 doesn't
         overflow, we can generate niters >> log2(vf); otherwise we generate
         (niters - vf) >> log2(vf) + 1 by using the fact that we know ratio
         will be at least one.  */
      log_vf = build_int_cst (type, exact_log2 (const_vf));
      if (niters_no_overflow)
        niters_vector = fold_build2 (RSHIFT_EXPR, type, ni_minus_gap, log_vf);
      else
        niters_vector
          = fold_build2 (PLUS_EXPR, type,
                         fold_build2 (RSHIFT_EXPR, type,
                                      fold_build2 (MINUS_EXPR, type,
                                                   ni_minus_gap,
                                                   build_int_cst (type, vf)),
                                      log_vf),
                         build_int_cst (type, 1));
      step_vector = build_one_cst (type);
    }
  else
    {
      niters_vector = ni_minus_gap;
      step_vector = build_int_cst (type, vf);
    }

  if (!is_gimple_val (niters_vector))
    {
      var = create_tmp_var (type, "bnd");
      gimple_seq stmts = NULL;
      niters_vector = force_gimple_operand (niters_vector, &stmts, true, var);
      gsi_insert_seq_on_edge_immediate (pe, stmts);
      /* Peeling algorithm guarantees that vector loop bound is at least ONE,
         we set range information to make niters analyzer's life easier.
         Note the number of latch iteration value can be TYPE_MAX_VALUE so
         we have to represent the vector niter TYPE_MAX_VALUE + 1 >> log_vf.  */
      if (stmts != NULL && log_vf)
        {
          if (niters_no_overflow)
            set_range_info (niters_vector, VR_RANGE,
                            wi::one (TYPE_PRECISION (type)),
                            wi::rshift (wi::max_value (TYPE_PRECISION (type),
                                                       TYPE_SIGN (type)),
                                        exact_log2 (const_vf),
                                        TYPE_SIGN (type)));
          /* For VF == 1 the vector IV might also overflow so we cannot
             assert a minimum value of 1.  */
          else if (const_vf > 1)
            set_range_info (niters_vector, VR_RANGE,
                            wi::one (TYPE_PRECISION (type)),
                            wi::rshift (wi::max_value (TYPE_PRECISION (type),
                                                       TYPE_SIGN (type))
                                        - (const_vf - 1),
                                        exact_log2 (const_vf), TYPE_SIGN (type))
                            + 1);
        }
    }
  *niters_vector_ptr = niters_vector;
  *step_vector_ptr = step_vector;

  return;
}

/* Given NITERS_VECTOR which is the number of iterations for vectorized
   loop specified by LOOP_VINFO after vectorization, compute the number
   of iterations before vectorization (niters_vector * vf) and store it
   to NITERS_VECTOR_MULT_VF_PTR.  */

static void
vect_gen_vector_loop_niters_mult_vf (loop_vec_info loop_vinfo,
                                     tree niters_vector,
                                     tree *niters_vector_mult_vf_ptr)
{
  /* We should be using a step_vector of VF if VF is variable.  */
  int vf = LOOP_VINFO_VECT_FACTOR (loop_vinfo).to_constant ();
  class loop *loop = LOOP_VINFO_LOOP (loop_vinfo);
  tree type = TREE_TYPE (niters_vector);
  tree log_vf = build_int_cst (type, exact_log2 (vf));
  basic_block exit_bb = single_exit (loop)->dest;

  gcc_assert (niters_vector_mult_vf_ptr != NULL);
  tree niters_vector_mult_vf = fold_build2 (LSHIFT_EXPR, type,
                                            niters_vector, log_vf);
  if (!is_gimple_val (niters_vector_mult_vf))
    {
      tree var = create_tmp_var (type, "niters_vector_mult_vf");
      gimple_seq stmts = NULL;
      niters_vector_mult_vf = force_gimple_operand (niters_vector_mult_vf,
                                                    &stmts, true, var);
      gimple_stmt_iterator gsi = gsi_start_bb (exit_bb);
      gsi_insert_seq_before (&gsi, stmts, GSI_SAME_STMT);
    }
  *niters_vector_mult_vf_ptr = niters_vector_mult_vf;
}

/* LCSSA_PHI is a lcssa phi of EPILOG loop which is copied from LOOP,
   this function searches for the corresponding lcssa phi node in exit
   bb of LOOP.  If it is found, return the phi result; otherwise return
   NULL.  */

static tree
find_guard_arg (class loop *loop, class loop *epilog ATTRIBUTE_UNUSED,
                gphi *lcssa_phi)
{
  gphi_iterator gsi;
  edge e = single_exit (loop);

  gcc_assert (single_pred_p (e->dest));
  for (gsi = gsi_start_phis (e->dest); !gsi_end_p (gsi); gsi_next (&gsi))
    {
      gphi *phi = gsi.phi ();
      if (operand_equal_p (PHI_ARG_DEF (phi, 0),
                           PHI_ARG_DEF (lcssa_phi, 0), 0))
        return PHI_RESULT (phi);
    }
  return NULL_TREE;
}

/* Function slpeel_tree_duplicate_loop_to_edge_cfg duplciates FIRST/SECOND
   from SECOND/FIRST and puts it at the original loop's preheader/exit
   edge, the two loops are arranged as below:

       preheader_a:
     first_loop:
       header_a:
         i_1 = PHI<i_0, i_2>;
         ...
         i_2 = i_1 + 1;
         if (cond_a)
           goto latch_a;
         else
           goto between_bb;
       latch_a:
         goto header_a;

       between_bb:
         ;; i_x = PHI<i_2>;   ;; LCSSA phi node to be created for FIRST,

     second_loop:
       header_b:
         i_3 = PHI<i_0, i_4>; ;; Use of i_0 to be replaced with i_x,
                                 or with i_2 if no LCSSA phi is created
                                 under condition of CREATE_LCSSA_FOR_IV_PHIS.
         ...
         i_4 = i_3 + 1;
         if (cond_b)
           goto latch_b;
         else
           goto exit_bb;
       latch_b:
         goto header_b;

       exit_bb:

   This function creates loop closed SSA for the first loop; update the
   second loop's PHI nodes by replacing argument on incoming edge with the
   result of newly created lcssa PHI nodes.  IF CREATE_LCSSA_FOR_IV_PHIS
   is false, Loop closed ssa phis will only be created for non-iv phis for
   the first loop.

   This function assumes exit bb of the first loop is preheader bb of the
   second loop, i.e, between_bb in the example code.  With PHIs updated,
   the second loop will execute rest iterations of the first.  */

static void
slpeel_update_phi_nodes_for_loops (loop_vec_info loop_vinfo,
                                   class loop *first, class loop *second,
                                   bool create_lcssa_for_iv_phis)
{
  gphi_iterator gsi_update, gsi_orig;
  class loop *loop = LOOP_VINFO_LOOP (loop_vinfo);

  edge first_latch_e = EDGE_SUCC (first->latch, 0);
  edge second_preheader_e = loop_preheader_edge (second);
  basic_block between_bb = single_exit (first)->dest;

  gcc_assert (between_bb == second_preheader_e->src);
  gcc_assert (single_pred_p (between_bb) && single_succ_p (between_bb));
  /* Either the first loop or the second is the loop to be vectorized.  */
  gcc_assert (loop == first || loop == second);

  for (gsi_orig = gsi_start_phis (first->header),
       gsi_update = gsi_start_phis (second->header);
       !gsi_end_p (gsi_orig) && !gsi_end_p (gsi_update);
       gsi_next (&gsi_orig), gsi_next (&gsi_update))
    {
      gphi *orig_phi = gsi_orig.phi ();
      gphi *update_phi = gsi_update.phi ();

      tree arg = PHI_ARG_DEF_FROM_EDGE (orig_phi, first_latch_e);
      /* Generate lcssa PHI node for the first loop.  */
      gphi *vect_phi = (loop == first) ? orig_phi : update_phi;
      stmt_vec_info vect_phi_info = loop_vinfo->lookup_stmt (vect_phi);
      if (create_lcssa_for_iv_phis || !iv_phi_p (vect_phi_info))
        {
          tree new_res = copy_ssa_name (PHI_RESULT (orig_phi));
          gphi *lcssa_phi = create_phi_node (new_res, between_bb);
          add_phi_arg (lcssa_phi, arg, single_exit (first), UNKNOWN_LOCATION);
          arg = new_res;
        }

      /* Update PHI node in the second loop by replacing arg on the loop's
         incoming edge.  */
      adjust_phi_and_debug_stmts (update_phi, second_preheader_e, arg);
    }

  /* For epilogue peeling we have to make sure to copy all LC PHIs
     for correct vectorization of live stmts.  */
  if (loop == first)
    {
      basic_block orig_exit = single_exit (second)->dest;
      for (gsi_orig = gsi_start_phis (orig_exit);
           !gsi_end_p (gsi_orig); gsi_next (&gsi_orig))
        {
          gphi *orig_phi = gsi_orig.phi ();
          tree orig_arg = PHI_ARG_DEF (orig_phi, 0);
          if (TREE_CODE (orig_arg) != SSA_NAME || virtual_operand_p  (orig_arg))
            continue;

          /* Already created in the above loop.   */
          if (find_guard_arg (first, second, orig_phi))
            continue;

          tree new_res = copy_ssa_name (orig_arg);
          gphi *lcphi = create_phi_node (new_res, between_bb);
          add_phi_arg (lcphi, orig_arg, single_exit (first), UNKNOWN_LOCATION);
        }
    }
}

/* Function slpeel_add_loop_guard adds guard skipping from the beginning
   of SKIP_LOOP to the beginning of UPDATE_LOOP.  GUARD_EDGE and MERGE_EDGE
   are two pred edges of the merge point before UPDATE_LOOP.  The two loops
   appear like below:

       guard_bb:
         if (cond)
           goto merge_bb;
         else
           goto skip_loop;

     skip_loop:
       header_a:
         i_1 = PHI<i_0, i_2>;
         ...
         i_2 = i_1 + 1;
         if (cond_a)
           goto latch_a;
         else
           goto exit_a;
       latch_a:
         goto header_a;

       exit_a:
         i_5 = PHI<i_2>;

       merge_bb:
         ;; PHI (i_x = PHI<i_0, i_5>) to be created at merge point.

     update_loop:
       header_b:
         i_3 = PHI<i_5, i_4>;  ;; Use of i_5 to be replaced with i_x.
         ...
         i_4 = i_3 + 1;
         if (cond_b)
           goto latch_b;
         else
           goto exit_bb;
       latch_b:
         goto header_b;

       exit_bb:

   This function creates PHI nodes at merge_bb and replaces the use of i_5
   in the update_loop's PHI node with the result of new PHI result.  */

static void
slpeel_update_phi_nodes_for_guard1 (class loop *skip_loop,
                                    class loop *update_loop,
                                    edge guard_edge, edge merge_edge)
{
  location_t merge_loc, guard_loc;
  edge orig_e = loop_preheader_edge (skip_loop);
  edge update_e = loop_preheader_edge (update_loop);
  gphi_iterator gsi_orig, gsi_update;

  for ((gsi_orig = gsi_start_phis (skip_loop->header),
        gsi_update = gsi_start_phis (update_loop->header));
       !gsi_end_p (gsi_orig) && !gsi_end_p (gsi_update);
       gsi_next (&gsi_orig), gsi_next (&gsi_update))
    {
      gphi *orig_phi = gsi_orig.phi ();
      gphi *update_phi = gsi_update.phi ();

      /* Generate new phi node at merge bb of the guard.  */
      tree new_res = copy_ssa_name (PHI_RESULT (orig_phi));
      gphi *new_phi = create_phi_node (new_res, guard_edge->dest);

      /* Merge bb has two incoming edges: GUARD_EDGE and MERGE_EDGE.  Set the
         args in NEW_PHI for these edges.  */
      tree merge_arg = PHI_ARG_DEF_FROM_EDGE (update_phi, update_e);
      tree guard_arg = PHI_ARG_DEF_FROM_EDGE (orig_phi, orig_e);
      merge_loc = gimple_phi_arg_location_from_edge (update_phi, update_e);
      guard_loc = gimple_phi_arg_location_from_edge (orig_phi, orig_e);
      add_phi_arg (new_phi, merge_arg, merge_edge, merge_loc);
      add_phi_arg (new_phi, guard_arg, guard_edge, guard_loc);

      /* Update phi in UPDATE_PHI.  */
      adjust_phi_and_debug_stmts (update_phi, update_e, new_res);
    }
}

/* LOOP and EPILOG are two consecutive loops in CFG and EPILOG is copied
   from LOOP.  Function slpeel_add_loop_guard adds guard skipping from a
   point between the two loops to the end of EPILOG.  Edges GUARD_EDGE
   and MERGE_EDGE are the two pred edges of merge_bb at the end of EPILOG.
   The CFG looks like:

     loop:
       header_a:
         i_1 = PHI<i_0, i_2>;
         ...
         i_2 = i_1 + 1;
         if (cond_a)
           goto latch_a;
         else
           goto exit_a;
       latch_a:
         goto header_a;

       exit_a:

       guard_bb:
         if (cond)
           goto merge_bb;
         else
           goto epilog_loop;

       ;; fall_through_bb

     epilog_loop:
       header_b:
         i_3 = PHI<i_2, i_4>;
         ...
         i_4 = i_3 + 1;
         if (cond_b)
           goto latch_b;
         else
           goto merge_bb;
       latch_b:
         goto header_b;

       merge_bb:
         ; PHI node (i_y = PHI<i_2, i_4>) to be created at merge point.

       exit_bb:
         i_x = PHI<i_4>;  ;Use of i_4 to be replaced with i_y in merge_bb.

   For each name used out side EPILOG (i.e - for each name that has a lcssa
   phi in exit_bb) we create a new PHI in merge_bb.  The new PHI has two
   args corresponding to GUARD_EDGE and MERGE_EDGE.  Arg for MERGE_EDGE is
   the arg of the original PHI in exit_bb, arg for GUARD_EDGE is defined
   by LOOP and is found in the exit bb of LOOP.  Arg of the original PHI
   in exit_bb will also be updated.  */

static void
slpeel_update_phi_nodes_for_guard2 (class loop *loop, class loop *epilog,
                                    edge guard_edge, edge merge_edge)
{
  gphi_iterator gsi;
  basic_block merge_bb = guard_edge->dest;

  gcc_assert (single_succ_p (merge_bb));
  edge e = single_succ_edge (merge_bb);
  basic_block exit_bb = e->dest;
  gcc_assert (single_pred_p (exit_bb));
  gcc_assert (single_pred (exit_bb) == single_exit (epilog)->dest);

  for (gsi = gsi_start_phis (exit_bb); !gsi_end_p (gsi); gsi_next (&gsi))
    {
      gphi *update_phi = gsi.phi ();
      tree old_arg = PHI_ARG_DEF (update_phi, 0);

      tree merge_arg = NULL_TREE;

      /* If the old argument is a SSA_NAME use its current_def.  */
      if (TREE_CODE (old_arg) == SSA_NAME)
        merge_arg = get_current_def (old_arg);
      /* If it's a constant or doesn't have a current_def, just use the old
         argument.  */
      if (!merge_arg)
        merge_arg = old_arg;

      tree guard_arg = find_guard_arg (loop, epilog, update_phi);
      /* If the var is live after loop but not a reduction, we simply
         use the old arg.  */
      if (!guard_arg)
        guard_arg = old_arg;

      /* Create new phi node in MERGE_BB:  */
      tree new_res = copy_ssa_name (PHI_RESULT (update_phi));
      gphi *merge_phi = create_phi_node (new_res, merge_bb);

      /* MERGE_BB has two incoming edges: GUARD_EDGE and MERGE_EDGE, Set
         the two PHI args in merge_phi for these edges.  */
      add_phi_arg (merge_phi, merge_arg, merge_edge, UNKNOWN_LOCATION);
      add_phi_arg (merge_phi, guard_arg, guard_edge, UNKNOWN_LOCATION);

      /* Update the original phi in exit_bb.  */
      adjust_phi_and_debug_stmts (update_phi, e, new_res);
    }
}

/* EPILOG loop is duplicated from the original loop for vectorizing,
   the arg of its loop closed ssa PHI needs to be updated.  */

static void
slpeel_update_phi_nodes_for_lcssa (class loop *epilog)
{
  gphi_iterator gsi;
  basic_block exit_bb = single_exit (epilog)->dest;

  gcc_assert (single_pred_p (exit_bb));
  edge e = EDGE_PRED (exit_bb, 0);
  for (gsi = gsi_start_phis (exit_bb); !gsi_end_p (gsi); gsi_next (&gsi))
    rename_use_op (PHI_ARG_DEF_PTR_FROM_EDGE (gsi.phi (), e));
}

/* EPILOGUE_VINFO is an epilogue loop that we now know would need to
   iterate exactly CONST_NITERS times.  Make a final decision about
   whether the epilogue loop should be used, returning true if so.  */

static bool
vect_update_epilogue_niters (loop_vec_info epilogue_vinfo,
                             unsigned HOST_WIDE_INT const_niters)
{
  /* Avoid wrap-around when computing const_niters - 1.  Also reject
     using an epilogue loop for a single scalar iteration, even if
     we could in principle implement that using partial vectors.  */
  unsigned int gap_niters = LOOP_VINFO_PEELING_FOR_GAPS (epilogue_vinfo);
  if (const_niters <= gap_niters + 1)
    return false;

  /* Install the number of iterations.  */
  tree niters_type = TREE_TYPE (LOOP_VINFO_NITERS (epilogue_vinfo));
  tree niters_tree = build_int_cst (niters_type, const_niters);
  tree nitersm1_tree = build_int_cst (niters_type, const_niters - 1);

  LOOP_VINFO_NITERS (epilogue_vinfo) = niters_tree;
  LOOP_VINFO_NITERSM1 (epilogue_vinfo) = nitersm1_tree;

  /* Decide what to do if the number of epilogue iterations is not
     a multiple of the epilogue loop's vectorization factor.  */
  return vect_determine_partial_vectors_and_peeling (epilogue_vinfo, true);
}

/* LOOP_VINFO is an epilogue loop whose corresponding main loop can be skipped.
   Return a value that equals:

   - MAIN_LOOP_VALUE when LOOP_VINFO is entered from the main loop and
   - SKIP_VALUE when the main loop is skipped.  */

tree
vect_get_main_loop_result (loop_vec_info loop_vinfo, tree main_loop_value,
                           tree skip_value)
{
  gcc_assert (loop_vinfo->main_loop_edge);

  tree phi_result = make_ssa_name (TREE_TYPE (main_loop_value));
  basic_block bb = loop_vinfo->main_loop_edge->dest;
  gphi *new_phi = create_phi_node (phi_result, bb);
  add_phi_arg (new_phi, main_loop_value, loop_vinfo->main_loop_edge,
               UNKNOWN_LOCATION);
  add_phi_arg (new_phi, skip_value,
               loop_vinfo->skip_main_loop_edge, UNKNOWN_LOCATION);
  return phi_result;
}

/* Function vect_do_peeling.

   Input:
   - LOOP_VINFO: Represent a loop to be vectorized, which looks like:

       preheader:
     LOOP:
       header_bb:
         loop_body
         if (exit_loop_cond) goto exit_bb
         else                goto header_bb
       exit_bb:

   - NITERS: The number of iterations of the loop.
   - NITERSM1: The number of iterations of the loop's latch.
   - NITERS_NO_OVERFLOW: No overflow in computing NITERS.
   - TH, CHECK_PROFITABILITY: Threshold of niters to vectorize loop if
                              CHECK_PROFITABILITY is true.
   Output:
   - *NITERS_VECTOR and *STEP_VECTOR describe how the main loop should
     iterate after vectorization; see vect_set_loop_condition for details.
   - *NITERS_VECTOR_MULT_VF_VAR is either null or an SSA name that
     should be set to the number of scalar iterations handled by the
     vector loop.  The SSA name is only used on exit from the loop.

   This function peels prolog and epilog from the loop, adds guards skipping
   PROLOG and EPILOG for various conditions.  As a result, the changed CFG
   would look like:

       guard_bb_1:
         if (prefer_scalar_loop) goto merge_bb_1
         else                    goto guard_bb_2

       guard_bb_2:
         if (skip_prolog) goto merge_bb_2
         else             goto prolog_preheader

       prolog_preheader:
     PROLOG:
       prolog_header_bb:
         prolog_body
         if (exit_prolog_cond) goto prolog_exit_bb
         else                  goto prolog_header_bb
       prolog_exit_bb:

       merge_bb_2:

       vector_preheader:
     VECTOR LOOP:
       vector_header_bb:
         vector_body
         if (exit_vector_cond) goto vector_exit_bb
         else                  goto vector_header_bb
       vector_exit_bb:

       guard_bb_3:
         if (skip_epilog) goto merge_bb_3
         else             goto epilog_preheader

       merge_bb_1:

       epilog_preheader:
     EPILOG:
       epilog_header_bb:
         epilog_body
         if (exit_epilog_cond) goto merge_bb_3
         else                  goto epilog_header_bb

       merge_bb_3:

   Note this function peels prolog and epilog only if it's necessary,
   as well as guards.
   This function returns the epilogue loop if a decision was made to vectorize
   it, otherwise NULL.

   The analysis resulting in this epilogue loop's loop_vec_info was performed
   in the same vect_analyze_loop call as the main loop's.  At that time
   vect_analyze_loop constructs a list of accepted loop_vec_info's for lower
   vectorization factors than the main loop.  This list is stored in the main
   loop's loop_vec_info in the 'epilogue_vinfos' member.  Everytime we decide to
   vectorize the epilogue loop for a lower vectorization factor,  the
   loop_vec_info sitting at the top of the epilogue_vinfos list is removed,
   updated and linked to the epilogue loop.  This is later used to vectorize
   the epilogue.  The reason the loop_vec_info needs updating is that it was
   constructed based on the original main loop, and the epilogue loop is a
   copy of this loop, so all links pointing to statements in the original loop
   need updating.  Furthermore, these loop_vec_infos share the
   data_reference's records, which will also need to be updated.

   TODO: Guard for prefer_scalar_loop should be emitted along with
   versioning conditions if loop versioning is needed.  */


class loop *
vect_do_peeling (loop_vec_info loop_vinfo, tree niters, tree nitersm1,
                 tree *niters_vector, tree *step_vector,
                 tree *niters_vector_mult_vf_var, int th,
                 bool check_profitability, bool niters_no_overflow,
                 tree *advance)
{
  edge e, guard_e;
  tree type = TREE_TYPE (niters), guard_cond;
  basic_block guard_bb, guard_to;
  profile_probability prob_prolog, prob_vector, prob_epilog;
  int estimated_vf;
  int prolog_peeling = 0;
  bool vect_epilogues = loop_vinfo->epilogue_vinfos.length () > 0;
  bool vect_epilogues_updated_niters = false;
  /* We currently do not support prolog peeling if the target alignment is not
     known at compile time.  'vect_gen_prolog_loop_niters' depends on the
     target alignment being constant.  */
  dr_vec_info *dr_info = LOOP_VINFO_UNALIGNED_DR (loop_vinfo);
  if (dr_info && !DR_TARGET_ALIGNMENT (dr_info).is_constant ())
    return NULL;

  if (!vect_use_loop_mask_for_alignment_p (loop_vinfo))
    prolog_peeling = LOOP_VINFO_PEELING_FOR_ALIGNMENT (loop_vinfo);

  poly_uint64 vf = LOOP_VINFO_VECT_FACTOR (loop_vinfo);
  poly_uint64 bound_epilog = 0;
  if (!LOOP_VINFO_USING_PARTIAL_VECTORS_P (loop_vinfo)
      && LOOP_VINFO_PEELING_FOR_NITER (loop_vinfo))
    bound_epilog += vf - 1;
  if (LOOP_VINFO_PEELING_FOR_GAPS (loop_vinfo))
    bound_epilog += 1;
  bool epilog_peeling = maybe_ne (bound_epilog, 0U);
  poly_uint64 bound_scalar = bound_epilog;

  if (!prolog_peeling && !epilog_peeling)
    return NULL;

  /* Before doing any peeling make sure to reset debug binds outside of
     the loop refering to defs not in LC SSA.  */
  class loop *loop = LOOP_VINFO_LOOP (loop_vinfo);
  for (unsigned i = 0; i < loop->num_nodes; ++i)
    {
      basic_block bb = LOOP_VINFO_BBS (loop_vinfo)[i];
      imm_use_iterator ui;
      gimple *use_stmt;
      for (gphi_iterator gsi = gsi_start_phis (bb); !gsi_end_p (gsi);
           gsi_next (&gsi))
        {
          FOR_EACH_IMM_USE_STMT (use_stmt, ui, gimple_phi_result (gsi.phi ()))
            if (gimple_debug_bind_p (use_stmt)
                && loop != gimple_bb (use_stmt)->loop_father
                && !flow_loop_nested_p (loop,
                                        gimple_bb (use_stmt)->loop_father))
              {
                gimple_debug_bind_reset_value (use_stmt);
                update_stmt (use_stmt);
              }
        }
      for (gimple_stmt_iterator gsi = gsi_start_bb (bb); !gsi_end_p (gsi);
           gsi_next (&gsi))
        {
          ssa_op_iter op_iter;
          def_operand_p def_p;
          FOR_EACH_SSA_DEF_OPERAND (def_p, gsi_stmt (gsi), op_iter, SSA_OP_DEF)
            FOR_EACH_IMM_USE_STMT (use_stmt, ui, DEF_FROM_PTR (def_p))
              if (gimple_debug_bind_p (use_stmt)
                  && loop != gimple_bb (use_stmt)->loop_father
                  && !flow_loop_nested_p (loop,
                                          gimple_bb (use_stmt)->loop_father))
                {
                  gimple_debug_bind_reset_value (use_stmt);
                  update_stmt (use_stmt);
                }
        }
    }

  prob_vector = profile_probability::guessed_always ().apply_scale (9, 10);
  estimated_vf = vect_vf_for_cost (loop_vinfo);
  if (estimated_vf == 2)
    estimated_vf = 3;
  prob_prolog = prob_epilog = profile_probability::guessed_always ()
                        .apply_scale (estimated_vf - 1, estimated_vf);

  class loop *prolog, *epilog = NULL;
  class loop *first_loop = loop;
  bool irred_flag = loop_preheader_edge (loop)->flags & EDGE_IRREDUCIBLE_LOOP;

  /* We might have a queued need to update virtual SSA form.  As we
     delete the update SSA machinery below after doing a regular
     incremental SSA update during loop copying make sure we don't
     lose that fact.
     ???  Needing to update virtual SSA form by renaming is unfortunate
     but not all of the vectorizer code inserting new loads / stores
     properly assigns virtual operands to those statements.  */
  update_ssa (TODO_update_ssa_only_virtuals);

  create_lcssa_for_virtual_phi (loop);

  /* If we're vectorizing an epilogue loop, the update_ssa above will
     have ensured that the virtual operand is in SSA form throughout the
     vectorized main loop.  Normally it is possible to trace the updated
     vector-stmt vdefs back to scalar-stmt vdefs and vector-stmt vuses
     back to scalar-stmt vuses, meaning that the effect of the SSA update
     remains local to the main loop.  However, there are rare cases in
     which the vectorized loop has vdefs even when the original scalar
     loop didn't.  For example, vectorizing a load with IFN_LOAD_LANES
     introduces clobbers of the temporary vector array, which in turn
     needs new vdefs.  If the scalar loop doesn't write to memory, these
     new vdefs will be the only ones in the vector loop.

     In that case, update_ssa will have added a new virtual phi to the
     main loop, which previously didn't need one.  Ensure that we (locally)
     maintain LCSSA form for the virtual operand, just as we would have
     done if the virtual phi had existed from the outset.  This makes it
     easier to duplicate the scalar epilogue loop below.  */
  tree vop_to_rename = NULL_TREE;
  if (loop_vec_info orig_loop_vinfo = LOOP_VINFO_ORIG_LOOP_INFO (loop_vinfo))
    {
      class loop *orig_loop = LOOP_VINFO_LOOP (orig_loop_vinfo);
      vop_to_rename = create_lcssa_for_virtual_phi (orig_loop);
    }

  if (MAY_HAVE_DEBUG_BIND_STMTS)
    {
      gcc_assert (!adjust_vec.exists ());
      adjust_vec.create (32);
    }
  initialize_original_copy_tables ();

  /* Record the anchor bb at which the guard should be placed if the scalar
     loop might be preferred.  */
  basic_block anchor = loop_preheader_edge (loop)->src;

  /* Generate the number of iterations for the prolog loop.  We do this here
     so that we can also get the upper bound on the number of iterations.  */
  tree niters_prolog;
  int bound_prolog = 0;
  if (prolog_peeling)
    niters_prolog = vect_gen_prolog_loop_niters (loop_vinfo, anchor,
                                                  &bound_prolog);
  else
    niters_prolog = build_int_cst (type, 0);

  loop_vec_info epilogue_vinfo = NULL;
  if (vect_epilogues)
    {
      epilogue_vinfo = loop_vinfo->epilogue_vinfos[0];
      loop_vinfo->epilogue_vinfos.ordered_remove (0);
    }

  tree niters_vector_mult_vf = NULL_TREE;
  /* Saving NITERs before the loop, as this may be changed by prologue.  */
  tree before_loop_niters = LOOP_VINFO_NITERS (loop_vinfo);
  edge update_e = NULL, skip_e = NULL;
  unsigned int lowest_vf = constant_lower_bound (vf);
  /* If we know the number of scalar iterations for the main loop we should
     check whether after the main loop there are enough iterations left over
     for the epilogue.  */
  if (vect_epilogues
      && LOOP_VINFO_NITERS_KNOWN_P (loop_vinfo)
      && prolog_peeling >= 0
      && known_eq (vf, lowest_vf))
    {
      unsigned HOST_WIDE_INT eiters
        = (LOOP_VINFO_INT_NITERS (loop_vinfo)
           - LOOP_VINFO_PEELING_FOR_GAPS (loop_vinfo));

      eiters -= prolog_peeling;
      eiters
        = eiters % lowest_vf + LOOP_VINFO_PEELING_FOR_GAPS (loop_vinfo);

      while (!vect_update_epilogue_niters (epilogue_vinfo, eiters))
        {
          delete epilogue_vinfo;
          epilogue_vinfo = NULL;
          if (loop_vinfo->epilogue_vinfos.length () == 0)
            {
              vect_epilogues = false;
              break;
            }
          epilogue_vinfo = loop_vinfo->epilogue_vinfos[0];
          loop_vinfo->epilogue_vinfos.ordered_remove (0);
        }
      vect_epilogues_updated_niters = true;
    }
  /* Prolog loop may be skipped.  */
  bool skip_prolog = (prolog_peeling != 0);
  /* Skip this loop to epilog when there are not enough iterations to enter this
     vectorized loop.  If true we should perform runtime checks on the NITERS
     to check whether we should skip the current vectorized loop.  If we know
     the number of scalar iterations we may choose to add a runtime check if
     this number "maybe" smaller than the number of iterations required
     when we know the number of scalar iterations may potentially
     be smaller than the number of iterations required to enter this loop, for
     this we use the upper bounds on the prolog and epilog peeling.  When we
     don't know the number of iterations and don't require versioning it is
     because we have asserted that there are enough scalar iterations to enter
     the main loop, so this skip is not necessary.  When we are versioning then
     we only add such a skip if we have chosen to vectorize the epilogue.  */
  bool skip_vector = (LOOP_VINFO_NITERS_KNOWN_P (loop_vinfo)
                      ? maybe_lt (LOOP_VINFO_INT_NITERS (loop_vinfo),
                                  bound_prolog + bound_epilog)
                      : (!LOOP_REQUIRES_VERSIONING (loop_vinfo)
                         || vect_epilogues));
  /* Epilog loop must be executed if the number of iterations for epilog
     loop is known at compile time, otherwise we need to add a check at
     the end of vector loop and skip to the end of epilog loop.  */
  bool skip_epilog = (prolog_peeling < 0
                      || !LOOP_VINFO_NITERS_KNOWN_P (loop_vinfo)
                      || !vf.is_constant ());
  /* PEELING_FOR_GAPS is special because epilog loop must be executed.  */
  if (LOOP_VINFO_PEELING_FOR_GAPS (loop_vinfo))
    skip_epilog = false;

  if (skip_vector)
    {
      split_edge (loop_preheader_edge (loop));

      /* Due to the order in which we peel prolog and epilog, we first
         propagate probability to the whole loop.  The purpose is to
         avoid adjusting probabilities of both prolog and vector loops
         separately.  Note in this case, the probability of epilog loop
         needs to be scaled back later.  */
      basic_block bb_before_loop = loop_preheader_edge (loop)->src;
      if (prob_vector.initialized_p ())
        {
          scale_bbs_frequencies (&bb_before_loop, 1, prob_vector);
          scale_loop_profile (loop, prob_vector, 0);
        }
    }

  dump_user_location_t loop_loc = find_loop_location (loop);
  class loop *scalar_loop = LOOP_VINFO_SCALAR_LOOP (loop_vinfo);
  if (vect_epilogues)
    /* Make sure to set the epilogue's epilogue scalar loop, such that we can
       use the original scalar loop as remaining epilogue if necessary.  */
    LOOP_VINFO_SCALAR_LOOP (epilogue_vinfo)
      = LOOP_VINFO_SCALAR_LOOP (loop_vinfo);

  if (prolog_peeling)
    {
      e = loop_preheader_edge (loop);
      if (!slpeel_can_duplicate_loop_p (loop, e))
        {
          dump_printf_loc (MSG_MISSED_OPTIMIZATION, loop_loc,
                           "loop can't be duplicated to preheader edge.\n");
          gcc_unreachable ();
        }
      /* Peel prolog and put it on preheader edge of loop.  */
      prolog = slpeel_tree_duplicate_loop_to_edge_cfg (loop, scalar_loop, e);
      if (!prolog)
        {
          dump_printf_loc (MSG_MISSED_OPTIMIZATION, loop_loc,
                           "slpeel_tree_duplicate_loop_to_edge_cfg failed.\n");
          gcc_unreachable ();
        }
      prolog->force_vectorize = false;
      slpeel_update_phi_nodes_for_loops (loop_vinfo, prolog, loop, true);
      first_loop = prolog;
      reset_original_copy_tables ();

      /* Update the number of iterations for prolog loop.  */
      tree step_prolog = build_one_cst (TREE_TYPE (niters_prolog));
      vect_set_loop_condition (prolog, NULL, niters_prolog,
                               step_prolog, NULL_TREE, false);

      /* Skip the prolog loop.  */
      if (skip_prolog)
        {
          guard_cond = fold_build2 (EQ_EXPR, boolean_type_node,
                                    niters_prolog, build_int_cst (type, 0));
          guard_bb = loop_preheader_edge (prolog)->src;
          basic_block bb_after_prolog = loop_preheader_edge (loop)->src;
          guard_to = split_edge (loop_preheader_edge (loop));
          guard_e = slpeel_add_loop_guard (guard_bb, guard_cond,
                                           guard_to, guard_bb,
                                           prob_prolog.invert (),
                                           irred_flag);
          e = EDGE_PRED (guard_to, 0);
          e = (e != guard_e ? e : EDGE_PRED (guard_to, 1));
          slpeel_update_phi_nodes_for_guard1 (prolog, loop, guard_e, e);

          scale_bbs_frequencies (&bb_after_prolog, 1, prob_prolog);
          scale_loop_profile (prolog, prob_prolog, bound_prolog);
        }

      /* Update init address of DRs.  */
      vect_update_inits_of_drs (loop_vinfo, niters_prolog, PLUS_EXPR);
      /* Update niters for vector loop.  */
      LOOP_VINFO_NITERS (loop_vinfo)
        = fold_build2 (MINUS_EXPR, type, niters, niters_prolog);
      LOOP_VINFO_NITERSM1 (loop_vinfo)
        = fold_build2 (MINUS_EXPR, type,
                       LOOP_VINFO_NITERSM1 (loop_vinfo), niters_prolog);
      bool new_var_p = false;
      niters = vect_build_loop_niters (loop_vinfo, &new_var_p);
      /* It's guaranteed that vector loop bound before vectorization is at
         least VF, so set range information for newly generated var.  */
      if (new_var_p)
        set_range_info (niters, VR_RANGE,
                        wi::to_wide (build_int_cst (type, vf)),
                        wi::to_wide (TYPE_MAX_VALUE (type)));

      /* Prolog iterates at most bound_prolog times, latch iterates at
         most bound_prolog - 1 times.  */
      record_niter_bound (prolog, bound_prolog - 1, false, true);
      delete_update_ssa ();
      adjust_vec_debug_stmts ();
      scev_reset ();
    }

  if (epilog_peeling)
    {
      e = single_exit (loop);
      if (!slpeel_can_duplicate_loop_p (loop, e))
        {
          dump_printf_loc (MSG_MISSED_OPTIMIZATION, loop_loc,
                           "loop can't be duplicated to exit edge.\n");
          gcc_unreachable ();
        }
      /* Peel epilog and put it on exit edge of loop.  If we are vectorizing
         said epilog then we should use a copy of the main loop as a starting
         point.  This loop may have already had some preliminary transformations
         to allow for more optimal vectorization, for example if-conversion.
         If we are not vectorizing the epilog then we should use the scalar loop
         as the transformations mentioned above make less or no sense when not
         vectorizing.  */
      epilog = vect_epilogues ? get_loop_copy (loop) : scalar_loop;
      if (vop_to_rename)
        {
          /* Vectorizing the main loop can sometimes introduce a vdef to
             a loop that previously didn't have one; see the comment above
             the definition of VOP_TO_RENAME for details.  The definition
             D that holds on E will then be different from the definition
             VOP_TO_RENAME that holds during SCALAR_LOOP, so we need to
             rename VOP_TO_RENAME to D when copying the loop.

             The virtual operand is in LCSSA form for the main loop,
             and no stmt between the main loop and E needs a vdef,
             so we know that D is provided by a phi rather than by a
             vdef on a normal gimple stmt.  */
          basic_block vdef_bb = e->src;
          gphi *vphi;
          while (!(vphi = get_virtual_phi (vdef_bb)))
            vdef_bb = get_immediate_dominator (CDI_DOMINATORS, vdef_bb);
          gcc_assert (vop_to_rename != gimple_phi_result (vphi));
          set_current_def (vop_to_rename, gimple_phi_result (vphi));
        }
      epilog = slpeel_tree_duplicate_loop_to_edge_cfg (loop, epilog, e);
      if (!epilog)
        {
          dump_printf_loc (MSG_MISSED_OPTIMIZATION, loop_loc,
                           "slpeel_tree_duplicate_loop_to_edge_cfg failed.\n");
          gcc_unreachable ();
        }
      epilog->force_vectorize = false;
      slpeel_update_phi_nodes_for_loops (loop_vinfo, loop, epilog, false);

      /* Scalar version loop may be preferred.  In this case, add guard
         and skip to epilog.  Note this only happens when the number of
         iterations of loop is unknown at compile time, otherwise this
         won't be vectorized.  */
      if (skip_vector)
        {
          /* Additional epilogue iteration is peeled if gap exists.  */
          tree t = vect_gen_scalar_loop_niters (niters_prolog, prolog_peeling,
                                                bound_prolog, bound_epilog,
                                                th, &bound_scalar,
                                                check_profitability);
          /* Build guard against NITERSM1 since NITERS may overflow.  */
          guard_cond = fold_build2 (LT_EXPR, boolean_type_node, nitersm1, t);
          guard_bb = anchor;
          guard_to = split_edge (loop_preheader_edge (epilog));
          guard_e = slpeel_add_loop_guard (guard_bb, guard_cond,
                                           guard_to, guard_bb,
                                           prob_vector.invert (),
                                           irred_flag);
          skip_e = guard_e;
          e = EDGE_PRED (guard_to, 0);
          e = (e != guard_e ? e : EDGE_PRED (guard_to, 1));
          slpeel_update_phi_nodes_for_guard1 (first_loop, epilog, guard_e, e);

          /* Simply propagate profile info from guard_bb to guard_to which is
             a merge point of control flow.  */
          guard_to->count = guard_bb->count;

          /* Scale probability of epilog loop back.
             FIXME: We should avoid scaling down and back up.  Profile may
             get lost if we scale down to 0.  */
          basic_block *bbs = get_loop_body (epilog);
          for (unsigned int i = 0; i < epilog->num_nodes; i++)
            bbs[i]->count = bbs[i]->count.apply_scale
                                 (bbs[i]->count,
                                  bbs[i]->count.apply_probability
                                    (prob_vector));
          free (bbs);
        }

      basic_block bb_before_epilog = loop_preheader_edge (epilog)->src;
      /* If loop is peeled for non-zero constant times, now niters refers to
         orig_niters - prolog_peeling, it won't overflow even the orig_niters
         overflows.  */
      niters_no_overflow |= (prolog_peeling > 0);
      vect_gen_vector_loop_niters (loop_vinfo, niters,
                                   niters_vector, step_vector,
                                   niters_no_overflow);
      if (!integer_onep (*step_vector))
        {
          /* On exit from the loop we will have an easy way of calcalating
             NITERS_VECTOR / STEP * STEP.  Install a dummy definition
             until then.  */
          niters_vector_mult_vf = make_ssa_name (TREE_TYPE (*niters_vector));
          SSA_NAME_DEF_STMT (niters_vector_mult_vf) = gimple_build_nop ();
          *niters_vector_mult_vf_var = niters_vector_mult_vf;
        }
      else
        vect_gen_vector_loop_niters_mult_vf (loop_vinfo, *niters_vector,
                                             &niters_vector_mult_vf);
      /* Update IVs of original loop as if they were advanced by
         niters_vector_mult_vf steps.  */
      gcc_checking_assert (vect_can_advance_ivs_p (loop_vinfo));
      update_e = skip_vector ? e : loop_preheader_edge (epilog);
      vect_update_ivs_after_vectorizer (loop_vinfo, niters_vector_mult_vf,
                                        update_e);

      if (skip_epilog)
        {
          guard_cond = fold_build2 (EQ_EXPR, boolean_type_node,
                                    niters, niters_vector_mult_vf);
          guard_bb = single_exit (loop)->dest;
          guard_to = split_edge (single_exit (epilog));
          guard_e = slpeel_add_loop_guard (guard_bb, guard_cond, guard_to,
                                           skip_vector ? anchor : guard_bb,
                                           prob_epilog.invert (),
                                           irred_flag);
          if (vect_epilogues)
            epilogue_vinfo->skip_this_loop_edge = guard_e;
          slpeel_update_phi_nodes_for_guard2 (loop, epilog, guard_e,
                                              single_exit (epilog));
          /* Only need to handle basic block before epilog loop if it's not
             the guard_bb, which is the case when skip_vector is true.  */
          if (guard_bb != bb_before_epilog)
            {
              prob_epilog = prob_vector * prob_epilog + prob_vector.invert ();

              scale_bbs_frequencies (&bb_before_epilog, 1, prob_epilog);
            }
          scale_loop_profile (epilog, prob_epilog, 0);
        }
      else
        slpeel_update_phi_nodes_for_lcssa (epilog);

      unsigned HOST_WIDE_INT bound;
      if (bound_scalar.is_constant (&bound))
        {
          gcc_assert (bound != 0);
          /* -1 to convert loop iterations to latch iterations.  */
          record_niter_bound (epilog, bound - 1, false, true);
        }

      delete_update_ssa ();
      adjust_vec_debug_stmts ();
      scev_reset ();
    }

  if (vect_epilogues)
    {
      epilog->aux = epilogue_vinfo;
      LOOP_VINFO_LOOP (epilogue_vinfo) = epilog;

      loop_constraint_clear (epilog, LOOP_C_INFINITE);

      /* We now must calculate the number of NITERS performed by the previous
         loop and EPILOGUE_NITERS to be performed by the epilogue.  */
      tree niters = fold_build2 (PLUS_EXPR, TREE_TYPE (niters_vector_mult_vf),
                                 niters_prolog, niters_vector_mult_vf);

      /* If skip_vector we may skip the previous loop, we insert a phi-node to
         determine whether we are coming from the previous vectorized loop
         using the update_e edge or the skip_vector basic block using the
         skip_e edge.  */
      if (skip_vector)
        {
          gcc_assert (update_e != NULL
                      && skip_e != NULL
                      && !vect_epilogues_updated_niters);
          gphi *new_phi = create_phi_node (make_ssa_name (TREE_TYPE (niters)),
                                           update_e->dest);
          tree new_ssa = make_ssa_name (TREE_TYPE (niters));
          gimple *stmt = gimple_build_assign (new_ssa, niters);
          gimple_stmt_iterator gsi;
          if (TREE_CODE (niters_vector_mult_vf) == SSA_NAME
              && SSA_NAME_DEF_STMT (niters_vector_mult_vf)->bb != NULL)
            {
              gsi = gsi_for_stmt (SSA_NAME_DEF_STMT (niters_vector_mult_vf));
              gsi_insert_after (&gsi, stmt, GSI_NEW_STMT);
            }
          else
            {
              gsi = gsi_last_bb (update_e->src);
              gsi_insert_before (&gsi, stmt, GSI_NEW_STMT);
            }

          niters = new_ssa;
          add_phi_arg (new_phi, niters, update_e, UNKNOWN_LOCATION);
          add_phi_arg (new_phi, build_zero_cst (TREE_TYPE (niters)), skip_e,
                       UNKNOWN_LOCATION);
          niters = PHI_RESULT (new_phi);
          epilogue_vinfo->main_loop_edge = update_e;
          epilogue_vinfo->skip_main_loop_edge = skip_e;
        }

      /* Set ADVANCE to the number of iterations performed by the previous
         loop and its prologue.  */
      *advance = niters;

      if (!vect_epilogues_updated_niters)
        {
          /* Subtract the number of iterations performed by the vectorized loop
             from the number of total iterations.  */
          tree epilogue_niters = fold_build2 (MINUS_EXPR, TREE_TYPE (niters),
                                              before_loop_niters,
                                              niters);

          LOOP_VINFO_NITERS (epilogue_vinfo) = epilogue_niters;
          LOOP_VINFO_NITERSM1 (epilogue_vinfo)
            = fold_build2 (MINUS_EXPR, TREE_TYPE (epilogue_niters),
                           epilogue_niters,
                           build_one_cst (TREE_TYPE (epilogue_niters)));

          /* Decide what to do if the number of epilogue iterations is not
             a multiple of the epilogue loop's vectorization factor.
             We should have rejected the loop during the analysis phase
             if this fails.  */
          if (!vect_determine_partial_vectors_and_peeling (epilogue_vinfo,
                                                           true))
            gcc_unreachable ();
        }
    }

  adjust_vec.release ();
  free_original_copy_tables ();

  return vect_epilogues ? epilog : NULL;
}

/* Function vect_create_cond_for_niters_checks.

   Create a conditional expression that represents the run-time checks for
   loop's niter.  The loop is guaranteed to terminate if the run-time
   checks hold.

   Input:
   COND_EXPR  - input conditional expression.  New conditions will be chained
                with logical AND operation.  If it is NULL, then the function
                is used to return the number of alias checks.
   LOOP_VINFO - field LOOP_VINFO_MAY_ALIAS_STMTS contains the list of ddrs
                to be checked.

   Output:
   COND_EXPR - conditional expression.

   The returned COND_EXPR is the conditional expression to be used in the
   if statement that controls which version of the loop gets executed at
   runtime.  */

static void
vect_create_cond_for_niters_checks (loop_vec_info loop_vinfo, tree *cond_expr)
{
  tree part_cond_expr = LOOP_VINFO_NITERS_ASSUMPTIONS (loop_vinfo);

  if (*cond_expr)
    *cond_expr = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
                              *cond_expr, part_cond_expr);
  else
    *cond_expr = part_cond_expr;
}

/* Set *COND_EXPR to a tree that is true when both the original *COND_EXPR
   and PART_COND_EXPR are true.  Treat a null *COND_EXPR as "true".  */

static void
chain_cond_expr (tree *cond_expr, tree part_cond_expr)
{
  if (*cond_expr)
    *cond_expr = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
                              *cond_expr, part_cond_expr);
  else
    *cond_expr = part_cond_expr;
}

/* Function vect_create_cond_for_align_checks.

   Create a conditional expression that represents the alignment checks for
   all of data references (array element references) whose alignment must be
   checked at runtime.

   Input:
   COND_EXPR  - input conditional expression.  New conditions will be chained
                with logical AND operation.
   LOOP_VINFO - two fields of the loop information are used.
                LOOP_VINFO_PTR_MASK is the mask used to check the alignment.
                LOOP_VINFO_MAY_MISALIGN_STMTS contains the refs to be checked.

   Output:
   COND_EXPR_STMT_LIST - statements needed to construct the conditional
                         expression.
   The returned value is the conditional expression to be used in the if
   statement that controls which version of the loop gets executed at runtime.

   The algorithm makes two assumptions:
     1) The number of bytes "n" in a vector is a power of 2.
     2) An address "a" is aligned if a%n is zero and that this
        test can be done as a&(n-1) == 0.  For example, for 16
        byte vectors the test is a&0xf == 0.  */

static void
vect_create_cond_for_align_checks (loop_vec_info loop_vinfo,
                                   tree *cond_expr,
                                   gimple_seq *cond_expr_stmt_list)
{
  const vec<stmt_vec_info> &may_misalign_stmts
    = LOOP_VINFO_MAY_MISALIGN_STMTS (loop_vinfo);
  stmt_vec_info stmt_info;
  int mask = LOOP_VINFO_PTR_MASK (loop_vinfo);
  tree mask_cst;
  unsigned int i;
  tree int_ptrsize_type;
  char tmp_name[20];
  tree or_tmp_name = NULL_TREE;
  tree and_tmp_name;
  gimple *and_stmt;
  tree ptrsize_zero;
  tree part_cond_expr;

  /* Check that mask is one less than a power of 2, i.e., mask is
     all zeros followed by all ones.  */
  gcc_assert ((mask != 0) && ((mask & (mask+1)) == 0));

  int_ptrsize_type = signed_type_for (ptr_type_node);

  /* Create expression (mask & (dr_1 || ... || dr_n)) where dr_i is the address
     of the first vector of the i'th data reference. */

  FOR_EACH_VEC_ELT (may_misalign_stmts, i, stmt_info)
    {
      gimple_seq new_stmt_list = NULL;
      tree addr_base;
      tree addr_tmp_name;
      tree new_or_tmp_name;
      gimple *addr_stmt, *or_stmt;
      tree vectype = STMT_VINFO_VECTYPE (stmt_info);
      bool negative = tree_int_cst_compare
        (DR_STEP (STMT_VINFO_DATA_REF (stmt_info)), size_zero_node) < 0;
      tree offset = negative
        ? size_int ((-TYPE_VECTOR_SUBPARTS (vectype) + 1)
                    * TREE_INT_CST_LOW (TYPE_SIZE_UNIT (TREE_TYPE (vectype))))
        : size_zero_node;

      /* create: addr_tmp = (int)(address_of_first_vector) */
      addr_base =
        vect_create_addr_base_for_vector_ref (loop_vinfo,
                                              stmt_info, &new_stmt_list,
                                              offset);
      if (new_stmt_list != NULL)
        gimple_seq_add_seq (cond_expr_stmt_list, new_stmt_list);

      sprintf (tmp_name, "addr2int%d", i);
      addr_tmp_name = make_temp_ssa_name (int_ptrsize_type, NULL, tmp_name);
      addr_stmt = gimple_build_assign (addr_tmp_name, NOP_EXPR, addr_base);
      gimple_seq_add_stmt (cond_expr_stmt_list, addr_stmt);

      /* The addresses are OR together.  */

      if (or_tmp_name != NULL_TREE)
        {
          /* create: or_tmp = or_tmp | addr_tmp */
          sprintf (tmp_name, "orptrs%d", i);
          new_or_tmp_name = make_temp_ssa_name (int_ptrsize_type, NULL, tmp_name);
          or_stmt = gimple_build_assign (new_or_tmp_name, BIT_IOR_EXPR,
                                         or_tmp_name, addr_tmp_name);
          gimple_seq_add_stmt (cond_expr_stmt_list, or_stmt);
          or_tmp_name = new_or_tmp_name;
        }
      else
        or_tmp_name = addr_tmp_name;

    } /* end for i */

  mask_cst = build_int_cst (int_ptrsize_type, mask);

  /* create: and_tmp = or_tmp & mask  */
  and_tmp_name = make_temp_ssa_name (int_ptrsize_type, NULL, "andmask");

  and_stmt = gimple_build_assign (and_tmp_name, BIT_AND_EXPR,
                                  or_tmp_name, mask_cst);
  gimple_seq_add_stmt (cond_expr_stmt_list, and_stmt);

  /* Make and_tmp the left operand of the conditional test against zero.
     if and_tmp has a nonzero bit then some address is unaligned.  */
  ptrsize_zero = build_int_cst (int_ptrsize_type, 0);
  part_cond_expr = fold_build2 (EQ_EXPR, boolean_type_node,
                                and_tmp_name, ptrsize_zero);
  chain_cond_expr (cond_expr, part_cond_expr);
}

/* If LOOP_VINFO_CHECK_UNEQUAL_ADDRS contains <A1, B1>, ..., <An, Bn>,
   create a tree representation of: (&A1 != &B1) && ... && (&An != &Bn).
   Set *COND_EXPR to a tree that is true when both the original *COND_EXPR
   and this new condition are true.  Treat a null *COND_EXPR as "true".  */

static void
vect_create_cond_for_unequal_addrs (loop_vec_info loop_vinfo, tree *cond_expr)
{
  const vec<vec_object_pair> &pairs
    = LOOP_VINFO_CHECK_UNEQUAL_ADDRS (loop_vinfo);
  unsigned int i;
  vec_object_pair *pair;
  FOR_EACH_VEC_ELT (pairs, i, pair)
    {
      tree addr1 = build_fold_addr_expr (pair->first);
      tree addr2 = build_fold_addr_expr (pair->second);
      tree part_cond_expr = fold_build2 (NE_EXPR, boolean_type_node,
                                         addr1, addr2);
      chain_cond_expr (cond_expr, part_cond_expr);
    }
}

/* Create an expression that is true when all lower-bound conditions for
   the vectorized loop are met.  Chain this condition with *COND_EXPR.  */

static void
vect_create_cond_for_lower_bounds (loop_vec_info loop_vinfo, tree *cond_expr)
{
  const vec<vec_lower_bound> &lower_bounds
    = LOOP_VINFO_LOWER_BOUNDS (loop_vinfo);
  for (unsigned int i = 0; i < lower_bounds.length (); ++i)
    {
      tree expr = lower_bounds[i].expr;
      tree type = unsigned_type_for (TREE_TYPE (expr));
      expr = fold_convert (type, expr);
      poly_uint64 bound = lower_bounds[i].min_value;
      if (!lower_bounds[i].unsigned_p)
        {
          expr = fold_build2 (PLUS_EXPR, type, expr,
                              build_int_cstu (type, bound - 1));
          bound += bound - 1;
        }
      tree part_cond_expr = fold_build2 (GE_EXPR, boolean_type_node, expr,
                                         build_int_cstu (type, bound));
      chain_cond_expr (cond_expr, part_cond_expr);
    }
}

/* Function vect_create_cond_for_alias_checks.

   Create a conditional expression that represents the run-time checks for
   overlapping of address ranges represented by a list of data references
   relations passed as input.

   Input:
   COND_EXPR  - input conditional expression.  New conditions will be chained
                with logical AND operation.  If it is NULL, then the function
                is used to return the number of alias checks.
   LOOP_VINFO - field LOOP_VINFO_MAY_ALIAS_STMTS contains the list of ddrs
                to be checked.

   Output:
   COND_EXPR - conditional expression.

   The returned COND_EXPR is the conditional expression to be used in the if
   statement that controls which version of the loop gets executed at runtime.
*/

void
vect_create_cond_for_alias_checks (loop_vec_info loop_vinfo, tree * cond_expr)
{
  const vec<dr_with_seg_len_pair_t> &comp_alias_ddrs =
    LOOP_VINFO_COMP_ALIAS_DDRS (loop_vinfo);

  if (comp_alias_ddrs.is_empty ())
    return;

  create_runtime_alias_checks (LOOP_VINFO_LOOP (loop_vinfo),
                               &comp_alias_ddrs, cond_expr);
  if (dump_enabled_p ())
    dump_printf_loc (MSG_NOTE, vect_location,
                     "created %u versioning for alias checks.\n",
                     comp_alias_ddrs.length ());
}


/* Function vect_loop_versioning.

   If the loop has data references that may or may not be aligned or/and
   has data reference relations whose independence was not proven then
   two versions of the loop need to be generated, one which is vectorized
   and one which isn't.  A test is then generated to control which of the
   loops is executed.  The test checks for the alignment of all of the
   data references that may or may not be aligned.  An additional
   sequence of runtime tests is generated for each pairs of DDRs whose
   independence was not proven.  The vectorized version of loop is
   executed only if both alias and alignment tests are passed.

   The test generated to check which version of loop is executed
   is modified to also check for profitability as indicated by the
   cost model threshold TH.

   The versioning precondition(s) are placed in *COND_EXPR and
   *COND_EXPR_STMT_LIST.  */

class loop *
vect_loop_versioning (loop_vec_info loop_vinfo,
                      gimple *loop_vectorized_call)
{
  class loop *loop = LOOP_VINFO_LOOP (loop_vinfo), *nloop;
  class loop *scalar_loop = LOOP_VINFO_SCALAR_LOOP (loop_vinfo);
  basic_block condition_bb;
  gphi_iterator gsi;
  gimple_stmt_iterator cond_exp_gsi;
  basic_block merge_bb;
  basic_block new_exit_bb;
  edge new_exit_e, e;
  gphi *orig_phi, *new_phi;
  tree cond_expr = NULL_TREE;
  gimple_seq cond_expr_stmt_list = NULL;
  tree arg;
  profile_probability prob = profile_probability::likely ();
  gimple_seq gimplify_stmt_list = NULL;
  tree scalar_loop_iters = LOOP_VINFO_NITERSM1 (loop_vinfo);
  bool version_align = LOOP_REQUIRES_VERSIONING_FOR_ALIGNMENT (loop_vinfo);
  bool version_alias = LOOP_REQUIRES_VERSIONING_FOR_ALIAS (loop_vinfo);
  bool version_niter = LOOP_REQUIRES_VERSIONING_FOR_NITERS (loop_vinfo);
  poly_uint64 versioning_threshold
    = LOOP_VINFO_VERSIONING_THRESHOLD (loop_vinfo);
  tree version_simd_if_cond
    = LOOP_REQUIRES_VERSIONING_FOR_SIMD_IF_COND (loop_vinfo);
  unsigned th = LOOP_VINFO_COST_MODEL_THRESHOLD (loop_vinfo);

  if (vect_apply_runtime_profitability_check_p (loop_vinfo)
      && !ordered_p (th, versioning_threshold))
    cond_expr = fold_build2 (GE_EXPR, boolean_type_node, scalar_loop_iters,
                             build_int_cst (TREE_TYPE (scalar_loop_iters),
                                            th - 1));
  if (maybe_ne (versioning_threshold, 0U))
    {
      tree expr = fold_build2 (GE_EXPR, boolean_type_node, scalar_loop_iters,
                               build_int_cst (TREE_TYPE (scalar_loop_iters),
                                              versioning_threshold - 1));
      if (cond_expr)
        cond_expr = fold_build2 (BIT_AND_EXPR, boolean_type_node,
                                 expr, cond_expr);
      else
        cond_expr = expr;
    }

  if (version_niter)
    vect_create_cond_for_niters_checks (loop_vinfo, &cond_expr);

  if (cond_expr)
    cond_expr = force_gimple_operand_1 (unshare_expr (cond_expr),
                                        &cond_expr_stmt_list,
                                        is_gimple_condexpr, NULL_TREE);

  if (version_align)
    vect_create_cond_for_align_checks (loop_vinfo, &cond_expr,
                                       &cond_expr_stmt_list);

  if (version_alias)
    {
      vect_create_cond_for_unequal_addrs (loop_vinfo, &cond_expr);
      vect_create_cond_for_lower_bounds (loop_vinfo, &cond_expr);
      vect_create_cond_for_alias_checks (loop_vinfo, &cond_expr);
    }

  if (version_simd_if_cond)
    {
      gcc_assert (dom_info_available_p (CDI_DOMINATORS));
      if (flag_checking)
        if (basic_block bb
            = gimple_bb (SSA_NAME_DEF_STMT (version_simd_if_cond)))
          gcc_assert (bb != loop->header
                      && dominated_by_p (CDI_DOMINATORS, loop->header, bb)
                      && (scalar_loop == NULL
                          || (bb != scalar_loop->header
                              && dominated_by_p (CDI_DOMINATORS,
                                                 scalar_loop->header, bb))));
      tree zero = build_zero_cst (TREE_TYPE (version_simd_if_cond));
      tree c = fold_build2 (NE_EXPR, boolean_type_node,
                            version_simd_if_cond, zero);
      if (cond_expr)
        cond_expr = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
                                 c, cond_expr);
      else
        cond_expr = c;
      if (dump_enabled_p ())
        dump_printf_loc (MSG_NOTE, vect_location,
                         "created versioning for simd if condition check.\n");
    }

  cond_expr = force_gimple_operand_1 (unshare_expr (cond_expr),
                                      &gimplify_stmt_list,
                                      is_gimple_condexpr, NULL_TREE);
  gimple_seq_add_seq (&cond_expr_stmt_list, gimplify_stmt_list);

  /* Compute the outermost loop cond_expr and cond_expr_stmt_list are
     invariant in.  */
  class loop *outermost = outermost_invariant_loop_for_expr (loop, cond_expr);
  for (gimple_stmt_iterator gsi = gsi_start (cond_expr_stmt_list);
       !gsi_end_p (gsi); gsi_next (&gsi))
    {
      gimple *stmt = gsi_stmt (gsi);
      update_stmt (stmt);
      ssa_op_iter iter;
      use_operand_p use_p;
      basic_block def_bb;
      FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE)
        if ((def_bb = gimple_bb (SSA_NAME_DEF_STMT (USE_FROM_PTR (use_p))))
            && flow_bb_inside_loop_p (outermost, def_bb))
          outermost = superloop_at_depth (loop, bb_loop_depth (def_bb) + 1);
    }

  /* Search for the outermost loop we can version.  Avoid versioning of
     non-perfect nests but allow if-conversion versioned loops inside.  */
  class loop *loop_to_version = loop;
  if (flow_loop_nested_p (outermost, loop))
    { 
      if (dump_enabled_p ())
        dump_printf_loc (MSG_NOTE, vect_location,
                         "trying to apply versioning to outer loop %d\n",
                         outermost->num);
      if (outermost->num == 0)
        outermost = superloop_at_depth (loop, 1);
      /* And avoid applying versioning on non-perfect nests.  */
      while (loop_to_version != outermost
             && single_exit (loop_outer (loop_to_version))
             && (!loop_outer (loop_to_version)->inner->next
                 || vect_loop_vectorized_call (loop_to_version))
             && (!loop_outer (loop_to_version)->inner->next
                 || !loop_outer (loop_to_version)->inner->next->next))
        loop_to_version = loop_outer (loop_to_version);
    }

  /* Apply versioning.  If there is already a scalar version created by
     if-conversion re-use that.  Note we cannot re-use the copy of
     an if-converted outer-loop when vectorizing the inner loop only.  */
  gcond *cond;
  if ((!loop_to_version->inner || loop == loop_to_version)
      && loop_vectorized_call)
    {
      gcc_assert (scalar_loop);
      condition_bb = gimple_bb (loop_vectorized_call);
      cond = as_a <gcond *> (last_stmt (condition_bb));
      gimple_cond_set_condition_from_tree (cond, cond_expr);
      update_stmt (cond);

      if (cond_expr_stmt_list)
        {
          cond_exp_gsi = gsi_for_stmt (loop_vectorized_call);
          gsi_insert_seq_before (&cond_exp_gsi, cond_expr_stmt_list,
                                 GSI_SAME_STMT);
        }

      /* if-conversion uses profile_probability::always () for both paths,
         reset the paths probabilities appropriately.  */
      edge te, fe;
      extract_true_false_edges_from_block (condition_bb, &te, &fe);
      te->probability = prob;
      fe->probability = prob.invert ();
      /* We can scale loops counts immediately but have to postpone
         scaling the scalar loop because we re-use it during peeling.  */
      scale_loop_frequencies (loop_to_version, te->probability);
      LOOP_VINFO_SCALAR_LOOP_SCALING (loop_vinfo) = fe->probability;

      nloop = scalar_loop;
      if (dump_enabled_p ())
        dump_printf_loc (MSG_NOTE, vect_location,
                         "reusing %sloop version created by if conversion\n",
                         loop_to_version != loop ? "outer " : "");
    }
  else
    {
      if (loop_to_version != loop
          && dump_enabled_p ())
        dump_printf_loc (MSG_NOTE, vect_location,
                         "applying loop versioning to outer loop %d\n",
                         loop_to_version->num);

      unsigned orig_pe_idx = loop_preheader_edge (loop)->dest_idx;

      initialize_original_copy_tables ();
      nloop = loop_version (loop_to_version, cond_expr, &condition_bb,
                            prob, prob.invert (), prob, prob.invert (), true);
      gcc_assert (nloop);
      nloop = get_loop_copy (loop);

      /* For cycle vectorization with SLP we rely on the PHI arguments
         appearing in the same order as the SLP node operands which for the
         loop PHI nodes means the preheader edge dest index needs to remain
         the same for the analyzed loop which also becomes the vectorized one.
         Make it so in case the state after versioning differs by redirecting
         the first edge into the header to the same destination which moves
         it last.  */
      if (loop_preheader_edge (loop)->dest_idx != orig_pe_idx)
        {
          edge e = EDGE_PRED (loop->header, 0);
          ssa_redirect_edge (e, e->dest);
          flush_pending_stmts (e);
        }
      gcc_assert (loop_preheader_edge (loop)->dest_idx == orig_pe_idx);

      /* Kill off IFN_LOOP_VECTORIZED_CALL in the copy, nobody will
         reap those otherwise;  they also refer to the original
         loops.  */
      class loop *l = loop;
      while (gimple *call = vect_loop_vectorized_call (l))
        {
          call = SSA_NAME_DEF_STMT (get_current_def (gimple_call_lhs (call)));
          fold_loop_internal_call (call, boolean_false_node);
          l = loop_outer (l);
        }
      free_original_copy_tables ();

      if (cond_expr_stmt_list)
        {
          cond_exp_gsi = gsi_last_bb (condition_bb);
          gsi_insert_seq_before (&cond_exp_gsi, cond_expr_stmt_list,
                                 GSI_SAME_STMT);
        }

      /* Loop versioning violates an assumption we try to maintain during
         vectorization - that the loop exit block has a single predecessor.
         After versioning, the exit block of both loop versions is the same
         basic block (i.e. it has two predecessors). Just in order to simplify
         following transformations in the vectorizer, we fix this situation
         here by adding a new (empty) block on the exit-edge of the loop,
         with the proper loop-exit phis to maintain loop-closed-form.
         If loop versioning wasn't done from loop, but scalar_loop instead,
         merge_bb will have already just a single successor.  */

      merge_bb = single_exit (loop_to_version)->dest;
      if (EDGE_COUNT (merge_bb->preds) >= 2)
        {
          gcc_assert (EDGE_COUNT (merge_bb->preds) >= 2);
          new_exit_bb = split_edge (single_exit (loop_to_version));
          new_exit_e = single_exit (loop_to_version);
          e = EDGE_SUCC (new_exit_bb, 0);

          for (gsi = gsi_start_phis (merge_bb); !gsi_end_p (gsi);
               gsi_next (&gsi))
            {
              tree new_res;
              orig_phi = gsi.phi ();
              new_res = copy_ssa_name (PHI_RESULT (orig_phi));
              new_phi = create_phi_node (new_res, new_exit_bb);
              arg = PHI_ARG_DEF_FROM_EDGE (orig_phi, e);
              add_phi_arg (new_phi, arg, new_exit_e,
                           gimple_phi_arg_location_from_edge (orig_phi, e));
              adjust_phi_and_debug_stmts (orig_phi, e, PHI_RESULT (new_phi));
            }
        }

      update_ssa (TODO_update_ssa);
    }

  if (version_niter)
    {
      /* The versioned loop could be infinite, we need to clear existing
         niter information which is copied from the original loop.  */
      gcc_assert (loop_constraint_set_p (loop, LOOP_C_FINITE));
      vect_free_loop_info_assumptions (nloop);
    }

  if (LOCATION_LOCUS (vect_location.get_location_t ()) != UNKNOWN_LOCATION
      && dump_enabled_p ())
    {
      if (version_alias)
        dump_printf_loc (MSG_OPTIMIZED_LOCATIONS | MSG_PRIORITY_USER_FACING,
                         vect_location,
                         "loop versioned for vectorization because of "
                         "possible aliasing\n");
      if (version_align)
        dump_printf_loc (MSG_OPTIMIZED_LOCATIONS | MSG_PRIORITY_USER_FACING,
                         vect_location,
                         "loop versioned for vectorization to enhance "
                         "alignment\n");

    }

  return nloop;
}