Import of virgin gcc 4.0.0 distribution.

[dragonfly.git] / contrib / gcc-4.0 / gcc / tree-vect-transform.c

/* Transformation Utilities for Loop Vectorization.
   Copyright (C) 2003,2004,2005 Free Software Foundation, Inc.
   Contributed by Dorit Naishlos <dorit@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 2, 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 COPYING.  If not, write to the Free
Software Foundation, 59 Temple Place - Suite 330, Boston, MA
02111-1307, USA.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "errors.h"
#include "ggc.h"
#include "tree.h"
#include "target.h"
#include "rtl.h"
#include "basic-block.h"
#include "diagnostic.h"
#include "tree-flow.h"
#include "tree-dump.h"
#include "timevar.h"
#include "cfgloop.h"
#include "expr.h"
#include "optabs.h"
#include "tree-data-ref.h"
#include "tree-chrec.h"
#include "tree-scalar-evolution.h"
#include "tree-vectorizer.h"
#include "langhooks.h"
#include "tree-pass.h"
#include "toplev.h"

/* Utility functions for the code transformation.  */
static bool vect_transform_stmt (tree, block_stmt_iterator *);
static void vect_align_data_ref (tree);
static tree vect_create_destination_var (tree, tree);
static tree vect_create_data_ref_ptr 
  (tree, block_stmt_iterator *, tree, tree *, bool); 
static tree vect_create_index_for_vector_ref (loop_vec_info);
static tree vect_create_addr_base_for_vector_ref (tree, tree *, tree);
static tree vect_get_new_vect_var (tree, enum vect_var_kind, const char *);
static tree vect_get_vec_def_for_operand (tree, tree);
static tree vect_init_vector (tree, tree);
static void vect_finish_stmt_generation 
  (tree stmt, tree vec_stmt, block_stmt_iterator *bsi);

/* Utility function dealing with loop peeling (not peeling itself).  */
static void vect_generate_tmps_on_preheader 
  (loop_vec_info, tree *, tree *, tree *);
static tree vect_build_loop_niters (loop_vec_info);
static void vect_update_ivs_after_vectorizer (loop_vec_info, tree, edge); 
static tree vect_gen_niters_for_prolog_loop (loop_vec_info, tree);
static void vect_update_inits_of_dr (struct data_reference *, tree niters);
static void vect_update_inits_of_drs (loop_vec_info, tree);
static void vect_do_peeling_for_alignment (loop_vec_info, struct loops *);
static void vect_do_peeling_for_loop_bound 
  (loop_vec_info, tree *, struct loops *);


/* Function vect_get_new_vect_var.

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

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

  if (var_kind == vect_simple_var)
    prefix = "vect_"; 
  else
    prefix = "vect_p";

  prefix_len = strlen (prefix);

  if (name)
    new_vect_var = create_tmp_var (type, concat (prefix, name, NULL));
  else
    new_vect_var = create_tmp_var (type, prefix);

  return new_vect_var;
}


/* Function vect_create_index_for_vector_ref.

   Create (and return) an index variable, along with it's update chain in the
   loop. This variable will be used to access a memory location in a vector
   operation.

   Input:
   LOOP: The loop being vectorized.
   BSI: The block_stmt_iterator where STMT is. Any new stmts created by this
        function can be added here, or in the loop pre-header.

   Output:
   Return an index that will be used to index a vector array.  It is expected
   that a pointer to the first vector will be used as the base address for the
   indexed reference.

   FORNOW: we are not trying to be efficient, just creating a new index each
   time from scratch.  At this time all vector references could use the same
   index.

   TODO: create only one index to be used by all vector references.  Record
   the index in the LOOP_VINFO the first time this procedure is called and
   return it on subsequent calls.  The increment of this index must be placed
   just before the conditional expression that ends the single block loop.  */

static tree
vect_create_index_for_vector_ref (loop_vec_info loop_vinfo)
{
  tree init, step;
  block_stmt_iterator incr_bsi;
  bool insert_after;
  tree indx_before_incr, indx_after_incr;
  struct loop *loop = LOOP_VINFO_LOOP (loop_vinfo);
  tree incr;

  /* It is assumed that the base pointer used for vectorized access contains
     the address of the first vector.  Therefore the index used for vectorized
     access must be initialized to zero and incremented by 1.  */

  init = integer_zero_node;
  step = integer_one_node;

  standard_iv_increment_position (loop, &incr_bsi, &insert_after);
  create_iv (init, step, NULL_TREE, loop, &incr_bsi, insert_after,
        &indx_before_incr, &indx_after_incr);
  incr = bsi_stmt (incr_bsi);
  get_stmt_operands (incr);
  set_stmt_info (stmt_ann (incr), new_stmt_vec_info (incr, loop_vinfo));

  return indx_before_incr;
}


/* Function vect_create_addr_base_for_vector_ref.

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

   Input:
   STMT: The statement containing the data reference.
   NEW_STMT_LIST: Must be initialized to NULL_TREE or a statement list.
   OFFSET: Optional. If supplied, it is be added to the initial address.

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

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

static tree
vect_create_addr_base_for_vector_ref (tree stmt,
                                      tree *new_stmt_list,
                                      tree offset)
{
  stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
  struct data_reference *dr = STMT_VINFO_DATA_REF (stmt_info);
  tree data_ref_base = 
    unshare_expr (STMT_VINFO_VECT_DR_BASE_ADDRESS (stmt_info));
  tree base_name = build_fold_indirect_ref (data_ref_base);
  tree ref = DR_REF (dr);
  tree scalar_type = TREE_TYPE (ref);
  tree scalar_ptr_type = build_pointer_type (scalar_type);
  tree vec_stmt;
  tree new_temp;
  tree addr_base, addr_expr;
  tree dest, new_stmt;
  tree base_offset = unshare_expr (STMT_VINFO_VECT_INIT_OFFSET (stmt_info));

  /* Create base_offset */
  dest = create_tmp_var (TREE_TYPE (base_offset), "base_off");
  add_referenced_tmp_var (dest);
  base_offset = force_gimple_operand (base_offset, &new_stmt, false, dest);  
  append_to_statement_list_force (new_stmt, new_stmt_list);

  if (offset)
    {
      tree tmp = create_tmp_var (TREE_TYPE (base_offset), "offset");
      add_referenced_tmp_var (tmp);
      offset = fold (build2 (MULT_EXPR, TREE_TYPE (offset), offset, 
                             STMT_VINFO_VECT_STEP (stmt_info)));
      base_offset = fold (build2 (PLUS_EXPR, TREE_TYPE (base_offset), 
                                  base_offset, offset));
      base_offset = force_gimple_operand (base_offset, &new_stmt, false, tmp);  
      append_to_statement_list_force (new_stmt, new_stmt_list);
    }
  
  /* base + base_offset */
  addr_base = fold (build2 (PLUS_EXPR, TREE_TYPE (data_ref_base), data_ref_base, 
                            base_offset));

  /* addr_expr = addr_base */
  addr_expr = vect_get_new_vect_var (scalar_ptr_type, vect_pointer_var,
                                     get_name (base_name));
  add_referenced_tmp_var (addr_expr);
  vec_stmt = build2 (MODIFY_EXPR, void_type_node, addr_expr, addr_base);
  new_temp = make_ssa_name (addr_expr, vec_stmt);
  TREE_OPERAND (vec_stmt, 0) = new_temp;
  append_to_statement_list_force (vec_stmt, new_stmt_list);

  if (vect_print_dump_info (REPORT_DETAILS, UNKNOWN_LOC))
    {
      fprintf (vect_dump, "created ");
      print_generic_expr (vect_dump, vec_stmt, TDF_SLIM);
    }
  return new_temp;
}


/* Function vect_align_data_ref.

   Handle mislignment of a memory accesses.

   FORNOW: Can't handle misaligned accesses. 
   Make sure that the dataref is aligned.  */

static void
vect_align_data_ref (tree stmt)
{
  stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
  struct data_reference *dr = STMT_VINFO_DATA_REF (stmt_info);

  /* FORNOW: can't handle misaligned accesses; 
             all accesses expected to be aligned.  */
  gcc_assert (aligned_access_p (dr));
}


/* Function vect_create_data_ref_ptr.

   Create a memory reference expression for vector access, to be used in a
   vector load/store stmt. The reference is based on a new pointer to vector
   type (vp).

   Input:
   1. STMT: a stmt that references memory. Expected to be of the form
         MODIFY_EXPR <name, data-ref> or MODIFY_EXPR <data-ref, name>.
   2. BSI: block_stmt_iterator where new stmts can be added.
   3. OFFSET (optional): an offset to be added to the initial address accessed
        by the data-ref in STMT.
   4. ONLY_INIT: indicate if vp is to be updated in the loop, or remain
        pointing to the initial address.

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

      v8hi *vp;
      vp = (v8hi *)initial_address;

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

      Return the initial_address in INITIAL_ADDRESS.

   2. Create a data-reference in the loop based on the new vector pointer vp,
      and using a new index variable 'idx' as follows:

      vp' = vp + update

      where if ONLY_INIT is true:
         update = zero
      and otherwise
         update = idx + vector_type_size

      Return the pointer vp'.


   FORNOW: handle only aligned and consecutive accesses.  */

static tree
vect_create_data_ref_ptr (tree stmt, block_stmt_iterator *bsi, tree offset,
                          tree *initial_address, bool only_init)
{
  tree base_name;
  stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
  loop_vec_info loop_vinfo = STMT_VINFO_LOOP_VINFO (stmt_info);
  struct loop *loop = LOOP_VINFO_LOOP (loop_vinfo);
  tree vectype = STMT_VINFO_VECTYPE (stmt_info);
  tree vect_ptr_type;
  tree vect_ptr;
  tree tag;
  v_may_def_optype v_may_defs = STMT_V_MAY_DEF_OPS (stmt);
  v_must_def_optype v_must_defs = STMT_V_MUST_DEF_OPS (stmt);
  vuse_optype vuses = STMT_VUSE_OPS (stmt);
  int nvuses, nv_may_defs, nv_must_defs;
  int i;
  tree new_temp;
  tree vec_stmt;
  tree new_stmt_list = NULL_TREE;
  tree idx;
  edge pe = loop_preheader_edge (loop);
  basic_block new_bb;
  tree vect_ptr_init;
  tree vectype_size;
  tree ptr_update;
  tree data_ref_ptr;
  tree type, tmp, size;

  base_name =  build_fold_indirect_ref (unshare_expr (
                      STMT_VINFO_VECT_DR_BASE_ADDRESS (stmt_info)));

  if (vect_print_dump_info (REPORT_DETAILS, UNKNOWN_LOC))
    {
      tree data_ref_base = base_name;
      fprintf (vect_dump, "create array_ref of type: ");
      print_generic_expr (vect_dump, vectype, TDF_SLIM);
      if (TREE_CODE (data_ref_base) == VAR_DECL)
        fprintf (vect_dump, "  vectorizing a one dimensional array ref: ");
      else if (TREE_CODE (data_ref_base) == ARRAY_REF)
        fprintf (vect_dump, "  vectorizing a multidimensional array ref: ");
      else if (TREE_CODE (data_ref_base) == COMPONENT_REF)
        fprintf (vect_dump, "  vectorizing a record based array ref: ");
      else if (TREE_CODE (data_ref_base) == SSA_NAME)
        fprintf (vect_dump, "  vectorizing a pointer ref: ");
      print_generic_expr (vect_dump, base_name, TDF_SLIM);
    }

  /** (1) Create the new vector-pointer variable:  **/

  vect_ptr_type = build_pointer_type (vectype);
  vect_ptr = vect_get_new_vect_var (vect_ptr_type, vect_pointer_var,
                                    get_name (base_name));
  add_referenced_tmp_var (vect_ptr);
  
  
  /** (2) Handle aliasing information of the new vector-pointer:  **/
  
  tag = STMT_VINFO_MEMTAG (stmt_info);
  gcc_assert (tag);
  get_var_ann (vect_ptr)->type_mem_tag = tag;
  
  /* Mark for renaming all aliased variables
     (i.e, the may-aliases of the type-mem-tag).  */
  nvuses = NUM_VUSES (vuses);
  nv_may_defs = NUM_V_MAY_DEFS (v_may_defs);
  nv_must_defs = NUM_V_MUST_DEFS (v_must_defs);
  for (i = 0; i < nvuses; i++)
    {
      tree use = VUSE_OP (vuses, i);
      if (TREE_CODE (use) == SSA_NAME)
        bitmap_set_bit (vars_to_rename, var_ann (SSA_NAME_VAR (use))->uid);
    }
  for (i = 0; i < nv_may_defs; i++)
    {
      tree def = V_MAY_DEF_RESULT (v_may_defs, i);
      if (TREE_CODE (def) == SSA_NAME)
        bitmap_set_bit (vars_to_rename, var_ann (SSA_NAME_VAR (def))->uid);
    }
  for (i = 0; i < nv_must_defs; i++)
    {
      tree def = V_MUST_DEF_RESULT (v_must_defs, i);
      if (TREE_CODE (def) == SSA_NAME)
        bitmap_set_bit (vars_to_rename, var_ann (SSA_NAME_VAR (def))->uid);
    }


  /** (3) Calculate the initial address the vector-pointer, and set
          the vector-pointer to point to it before the loop:  **/

  /* Create: (&(base[init_val+offset]) in the loop preheader.  */
  new_temp = vect_create_addr_base_for_vector_ref (stmt, &new_stmt_list,
                                                   offset);
  pe = loop_preheader_edge (loop);
  new_bb = bsi_insert_on_edge_immediate (pe, new_stmt_list);
  gcc_assert (!new_bb);
  *initial_address = new_temp;

  /* Create: p = (vectype *) initial_base  */
  vec_stmt = fold_convert (vect_ptr_type, new_temp);
  vec_stmt = build2 (MODIFY_EXPR, void_type_node, vect_ptr, vec_stmt);
  new_temp = make_ssa_name (vect_ptr, vec_stmt);
  TREE_OPERAND (vec_stmt, 0) = new_temp;
  new_bb = bsi_insert_on_edge_immediate (pe, vec_stmt);
  gcc_assert (!new_bb);
  vect_ptr_init = TREE_OPERAND (vec_stmt, 0);


  /** (4) Handle the updating of the vector-pointer inside the loop: **/

  if (only_init) /* No update in loop is required.  */
    return vect_ptr_init;

  idx = vect_create_index_for_vector_ref (loop_vinfo);

  /* Create: update = idx * vectype_size  */
  tmp = create_tmp_var (integer_type_node, "update");
  add_referenced_tmp_var (tmp);
  size = TYPE_SIZE (vect_ptr_type); 
  type = lang_hooks.types.type_for_size (tree_low_cst (size, 1), 1);
  ptr_update = create_tmp_var (type, "update");
  add_referenced_tmp_var (ptr_update);
  vectype_size = TYPE_SIZE_UNIT (vectype);
  vec_stmt = build2 (MULT_EXPR, integer_type_node, idx, vectype_size);
  vec_stmt = build2 (MODIFY_EXPR, void_type_node, tmp, vec_stmt);
  new_temp = make_ssa_name (tmp, vec_stmt);
  TREE_OPERAND (vec_stmt, 0) = new_temp;
  bsi_insert_before (bsi, vec_stmt, BSI_SAME_STMT);
  vec_stmt = fold_convert (type, new_temp);
  vec_stmt = build2 (MODIFY_EXPR, void_type_node, ptr_update, vec_stmt);
  new_temp = make_ssa_name (ptr_update, vec_stmt);
  TREE_OPERAND (vec_stmt, 0) = new_temp;
  bsi_insert_before (bsi, vec_stmt, BSI_SAME_STMT);

  /* Create: data_ref_ptr = vect_ptr_init + update  */
  vec_stmt = build2 (PLUS_EXPR, vect_ptr_type, vect_ptr_init, new_temp);
  vec_stmt = build2 (MODIFY_EXPR, void_type_node, vect_ptr, vec_stmt);
  new_temp = make_ssa_name (vect_ptr, vec_stmt);
  TREE_OPERAND (vec_stmt, 0) = new_temp;
  bsi_insert_before (bsi, vec_stmt, BSI_SAME_STMT);
  data_ref_ptr = TREE_OPERAND (vec_stmt, 0);

  return data_ref_ptr;
}


/* Function vect_create_destination_var.

   Create a new temporary of type VECTYPE.  */

static tree
vect_create_destination_var (tree scalar_dest, tree vectype)
{
  tree vec_dest;
  const char *new_name;

  gcc_assert (TREE_CODE (scalar_dest) == SSA_NAME);

  new_name = get_name (scalar_dest);
  if (!new_name)
    new_name = "var_";
  vec_dest = vect_get_new_vect_var (vectype, vect_simple_var, new_name);
  add_referenced_tmp_var (vec_dest);

  return vec_dest;
}


/* Function vect_init_vector.

   Insert a new stmt (INIT_STMT) that initializes a new vector variable with
   the vector elements of VECTOR_VAR. Return the DEF of INIT_STMT. It will be
   used in the vectorization of STMT.  */

static tree
vect_init_vector (tree stmt, tree vector_var)
{
  stmt_vec_info stmt_vinfo = vinfo_for_stmt (stmt);
  loop_vec_info loop_vinfo = STMT_VINFO_LOOP_VINFO (stmt_vinfo);
  struct loop *loop = LOOP_VINFO_LOOP (loop_vinfo);
  tree new_var;
  tree init_stmt;
  tree vectype = STMT_VINFO_VECTYPE (stmt_vinfo); 
  tree vec_oprnd;
  edge pe;
  tree new_temp;
  basic_block new_bb;
 
  new_var = vect_get_new_vect_var (vectype, vect_simple_var, "cst_");
  add_referenced_tmp_var (new_var); 
 
  init_stmt = build2 (MODIFY_EXPR, vectype, new_var, vector_var);
  new_temp = make_ssa_name (new_var, init_stmt);
  TREE_OPERAND (init_stmt, 0) = new_temp;

  pe = loop_preheader_edge (loop);
  new_bb = bsi_insert_on_edge_immediate (pe, init_stmt);
  gcc_assert (!new_bb);

  if (vect_print_dump_info (REPORT_DETAILS, UNKNOWN_LOC))
    {
      fprintf (vect_dump, "created new init_stmt: ");
      print_generic_expr (vect_dump, init_stmt, TDF_SLIM);
    }

  vec_oprnd = TREE_OPERAND (init_stmt, 0);
  return vec_oprnd;
}


/* Function vect_get_vec_def_for_operand.

   OP is an operand in STMT. This function returns a (vector) def that will be
   used in the vectorized stmt for STMT.

   In the case that OP is an SSA_NAME which is defined in the loop, then
   STMT_VINFO_VEC_STMT of the defining stmt holds the relevant def.

   In case OP is an invariant or constant, a new stmt that creates a vector def
   needs to be introduced.  */

static tree
vect_get_vec_def_for_operand (tree op, tree stmt)
{
  tree vec_oprnd;
  tree vec_stmt;
  tree def_stmt;
  stmt_vec_info def_stmt_info = NULL;
  stmt_vec_info stmt_vinfo = vinfo_for_stmt (stmt);
  tree vectype = STMT_VINFO_VECTYPE (stmt_vinfo);
  int nunits = GET_MODE_NUNITS (TYPE_MODE (vectype));
  loop_vec_info loop_vinfo = STMT_VINFO_LOOP_VINFO (stmt_vinfo);
  struct loop *loop = LOOP_VINFO_LOOP (loop_vinfo);
  basic_block bb;
  tree vec_inv;
  tree t = NULL_TREE;
  tree def;
  int i;

  if (vect_print_dump_info (REPORT_DETAILS, UNKNOWN_LOC))
    {
      fprintf (vect_dump, "vect_get_vec_def_for_operand: ");
      print_generic_expr (vect_dump, op, TDF_SLIM);
    }

  /** ===> Case 1: operand is a constant.  **/

  if (TREE_CODE (op) == INTEGER_CST || TREE_CODE (op) == REAL_CST)
    {
      /* Create 'vect_cst_ = {cst,cst,...,cst}'  */

      tree vec_cst;

      /* Build a tree with vector elements.  */
      if (vect_print_dump_info (REPORT_DETAILS, UNKNOWN_LOC))
        fprintf (vect_dump, "Create vector_cst. nunits = %d", nunits);

      for (i = nunits - 1; i >= 0; --i)
        {
          t = tree_cons (NULL_TREE, op, t);
        }
      vec_cst = build_vector (vectype, t);
      return vect_init_vector (stmt, vec_cst);
    }

  gcc_assert (TREE_CODE (op) == SSA_NAME);
 
  /** ===> Case 2: operand is an SSA_NAME - find the stmt that defines it.  **/

  def_stmt = SSA_NAME_DEF_STMT (op);
  def_stmt_info = vinfo_for_stmt (def_stmt);

  if (vect_print_dump_info (REPORT_DETAILS, UNKNOWN_LOC))
    {
      fprintf (vect_dump, "vect_get_vec_def_for_operand: def_stmt: ");
      print_generic_expr (vect_dump, def_stmt, TDF_SLIM);
    }


  /** ==> Case 2.1: operand is defined inside the loop.  **/

  if (def_stmt_info)
    {
      /* Get the def from the vectorized stmt.  */

      vec_stmt = STMT_VINFO_VEC_STMT (def_stmt_info);
      gcc_assert (vec_stmt);
      vec_oprnd = TREE_OPERAND (vec_stmt, 0);
      return vec_oprnd;
    }


  /** ==> Case 2.2: operand is defined by the loop-header phi-node - 
                    it is a reduction/induction.  **/

  bb = bb_for_stmt (def_stmt);
  if (TREE_CODE (def_stmt) == PHI_NODE && flow_bb_inside_loop_p (loop, bb))
    {
      if (vect_print_dump_info (REPORT_DETAILS, UNKNOWN_LOC))
        fprintf (vect_dump, "reduction/induction - unsupported.");
      internal_error ("no support for reduction/induction"); /* FORNOW */
    }


  /** ==> Case 2.3: operand is defined outside the loop - 
                    it is a loop invariant.  */

  switch (TREE_CODE (def_stmt))
    {
    case PHI_NODE:
      def = PHI_RESULT (def_stmt);
      break;
    case MODIFY_EXPR:
      def = TREE_OPERAND (def_stmt, 0);
      break;
    case NOP_EXPR:
      def = TREE_OPERAND (def_stmt, 0);
      gcc_assert (IS_EMPTY_STMT (def_stmt));
      def = op;
      break;
    default:
      if (vect_print_dump_info (REPORT_DETAILS, UNKNOWN_LOC))
        {
          fprintf (vect_dump, "unsupported defining stmt: ");
          print_generic_expr (vect_dump, def_stmt, TDF_SLIM);
        }
      internal_error ("unsupported defining stmt");
    }

  /* Build a tree with vector elements.
     Create 'vec_inv = {inv,inv,..,inv}'  */

  if (vect_print_dump_info (REPORT_DETAILS, UNKNOWN_LOC))
    fprintf (vect_dump, "Create vector_inv.");

  for (i = nunits - 1; i >= 0; --i)
    {
      t = tree_cons (NULL_TREE, def, t);
    }

  vec_inv = build_constructor (vectype, t);
  return vect_init_vector (stmt, vec_inv);
}


/* Function vect_finish_stmt_generation.

   Insert a new stmt.  */

static void
vect_finish_stmt_generation (tree stmt, tree vec_stmt, block_stmt_iterator *bsi)
{
  bsi_insert_before (bsi, vec_stmt, BSI_SAME_STMT);

  if (vect_print_dump_info (REPORT_DETAILS, UNKNOWN_LOC))
    {
      fprintf (vect_dump, "add new stmt: ");
      print_generic_expr (vect_dump, vec_stmt, TDF_SLIM);
    }

#ifdef ENABLE_CHECKING
  /* Make sure bsi points to the stmt that is being vectorized.  */
  gcc_assert (stmt == bsi_stmt (*bsi));
#endif

#ifdef USE_MAPPED_LOCATION
  SET_EXPR_LOCATION (vec_stmt, EXPR_LOCUS (stmt));
#else
  SET_EXPR_LOCUS (vec_stmt, EXPR_LOCUS (stmt));
#endif
}


/* Function vectorizable_assignment.

   Check if STMT performs an assignment (copy) that can be vectorized. 
   If VEC_STMT is also passed, vectorize the STMT: create a vectorized 
   stmt to replace it, put it in VEC_STMT, and insert it at BSI.
   Return FALSE if not a vectorizable STMT, TRUE otherwise.  */

bool
vectorizable_assignment (tree stmt, block_stmt_iterator *bsi, tree *vec_stmt)
{
  tree vec_dest;
  tree scalar_dest;
  tree op;
  tree vec_oprnd;
  stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
  tree vectype = STMT_VINFO_VECTYPE (stmt_info);
  loop_vec_info loop_vinfo = STMT_VINFO_LOOP_VINFO (stmt_info);
  tree new_temp;

  /* Is vectorizable assignment?  */

  if (TREE_CODE (stmt) != MODIFY_EXPR)
    return false;

  scalar_dest = TREE_OPERAND (stmt, 0);
  if (TREE_CODE (scalar_dest) != SSA_NAME)
    return false;

  op = TREE_OPERAND (stmt, 1);
  if (!vect_is_simple_use (op, loop_vinfo, NULL))
    {
      if (vect_print_dump_info (REPORT_DETAILS, UNKNOWN_LOC))
        fprintf (vect_dump, "use not simple.");
      return false;
    }

  if (!vec_stmt) /* transformation not required.  */
    {
      STMT_VINFO_TYPE (stmt_info) = assignment_vec_info_type;
      return true;
    }

  /** Transform.  **/
  if (vect_print_dump_info (REPORT_DETAILS, UNKNOWN_LOC))
    fprintf (vect_dump, "transform assignment.");

  /* Handle def.  */
  vec_dest = vect_create_destination_var (scalar_dest, vectype);

  /* Handle use.  */
  op = TREE_OPERAND (stmt, 1);
  vec_oprnd = vect_get_vec_def_for_operand (op, stmt);

  /* Arguments are ready. create the new vector stmt.  */
  *vec_stmt = build2 (MODIFY_EXPR, vectype, vec_dest, vec_oprnd);
  new_temp = make_ssa_name (vec_dest, *vec_stmt);
  TREE_OPERAND (*vec_stmt, 0) = new_temp;
  vect_finish_stmt_generation (stmt, *vec_stmt, bsi);
  
  return true;
}


/* Function vectorizable_operation.

   Check if STMT performs a binary or unary operation that can be vectorized. 
   If VEC_STMT is also passed, vectorize the STMT: create a vectorized 
   stmt to replace it, put it in VEC_STMT, and insert it at BSI.
   Return FALSE if not a vectorizable STMT, TRUE otherwise.  */

bool
vectorizable_operation (tree stmt, block_stmt_iterator *bsi, tree *vec_stmt)
{
  tree vec_dest;
  tree scalar_dest;
  tree operation;
  tree op0, op1 = NULL;
  tree vec_oprnd0, vec_oprnd1=NULL;
  stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
  tree vectype = STMT_VINFO_VECTYPE (stmt_info);
  loop_vec_info loop_vinfo = STMT_VINFO_LOOP_VINFO (stmt_info);
  int i;
  enum tree_code code;
  enum machine_mode vec_mode;
  tree new_temp;
  int op_type;
  tree op;
  optab optab;

  /* Is STMT a vectorizable binary/unary operation?   */
  if (TREE_CODE (stmt) != MODIFY_EXPR)
    return false;

  if (TREE_CODE (TREE_OPERAND (stmt, 0)) != SSA_NAME)
    return false;

  operation = TREE_OPERAND (stmt, 1);
  code = TREE_CODE (operation);
  optab = optab_for_tree_code (code, vectype);

  /* Support only unary or binary operations.  */
  op_type = TREE_CODE_LENGTH (code);
  if (op_type != unary_op && op_type != binary_op)
    {
      if (vect_print_dump_info (REPORT_DETAILS, UNKNOWN_LOC))
        fprintf (vect_dump, "num. args = %d (not unary/binary op).", op_type);
      return false;
    }

  for (i = 0; i < op_type; i++)
    {
      op = TREE_OPERAND (operation, i);
      if (!vect_is_simple_use (op, loop_vinfo, NULL))
        {
          if (vect_print_dump_info (REPORT_DETAILS, UNKNOWN_LOC))
            fprintf (vect_dump, "use not simple.");
          return false;
        }       
    } 

  /* Supportable by target?  */
  if (!optab)
    {
      if (vect_print_dump_info (REPORT_DETAILS, UNKNOWN_LOC))
        fprintf (vect_dump, "no optab.");
      return false;
    }
  vec_mode = TYPE_MODE (vectype);
  if (optab->handlers[(int) vec_mode].insn_code == CODE_FOR_nothing)
    {
      if (vect_print_dump_info (REPORT_DETAILS, UNKNOWN_LOC))
        fprintf (vect_dump, "op not supported by target.");
      return false;
    }

  if (!vec_stmt) /* transformation not required.  */
    {
      STMT_VINFO_TYPE (stmt_info) = op_vec_info_type;
      return true;
    }

  /** Transform.  **/

  if (vect_print_dump_info (REPORT_DETAILS, UNKNOWN_LOC))
    fprintf (vect_dump, "transform binary/unary operation.");

  /* Handle def.  */
  scalar_dest = TREE_OPERAND (stmt, 0);
  vec_dest = vect_create_destination_var (scalar_dest, vectype);

  /* Handle uses.  */
  op0 = TREE_OPERAND (operation, 0);
  vec_oprnd0 = vect_get_vec_def_for_operand (op0, stmt);

  if (op_type == binary_op)
    {
      op1 = TREE_OPERAND (operation, 1);
      vec_oprnd1 = vect_get_vec_def_for_operand (op1, stmt); 
    }

  /* Arguments are ready. create the new vector stmt.  */

  if (op_type == binary_op)
    *vec_stmt = build2 (MODIFY_EXPR, vectype, vec_dest,
                build2 (code, vectype, vec_oprnd0, vec_oprnd1));
  else
    *vec_stmt = build2 (MODIFY_EXPR, vectype, vec_dest,
                build1 (code, vectype, vec_oprnd0));
  new_temp = make_ssa_name (vec_dest, *vec_stmt);
  TREE_OPERAND (*vec_stmt, 0) = new_temp;
  vect_finish_stmt_generation (stmt, *vec_stmt, bsi);

  return true;
}


/* Function vectorizable_store.

   Check if STMT defines a non scalar data-ref (array/pointer/structure) that 
   can be vectorized. 
   If VEC_STMT is also passed, vectorize the STMT: create a vectorized 
   stmt to replace it, put it in VEC_STMT, and insert it at BSI.
   Return FALSE if not a vectorizable STMT, TRUE otherwise.  */

bool
vectorizable_store (tree stmt, block_stmt_iterator *bsi, tree *vec_stmt)
{
  tree scalar_dest;
  tree data_ref;
  tree op;
  tree vec_oprnd1;
  stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
  struct data_reference *dr = STMT_VINFO_DATA_REF (stmt_info);
  tree vectype = STMT_VINFO_VECTYPE (stmt_info);
  loop_vec_info loop_vinfo = STMT_VINFO_LOOP_VINFO (stmt_info);
  enum machine_mode vec_mode;
  tree dummy;
  enum dr_alignment_support alignment_support_cheme;

  /* Is vectorizable store? */

  if (TREE_CODE (stmt) != MODIFY_EXPR)
    return false;

  scalar_dest = TREE_OPERAND (stmt, 0);
  if (TREE_CODE (scalar_dest) != ARRAY_REF
      && TREE_CODE (scalar_dest) != INDIRECT_REF)
    return false;

  op = TREE_OPERAND (stmt, 1);
  if (!vect_is_simple_use (op, loop_vinfo, NULL))
    {
      if (vect_print_dump_info (REPORT_DETAILS, UNKNOWN_LOC))
        fprintf (vect_dump, "use not simple.");
      return false;
    }

  vec_mode = TYPE_MODE (vectype);
  /* FORNOW. In some cases can vectorize even if data-type not supported
     (e.g. - array initialization with 0).  */
  if (mov_optab->handlers[(int)vec_mode].insn_code == CODE_FOR_nothing)
    return false;

  if (!STMT_VINFO_DATA_REF (stmt_info))
    return false;


  if (!vec_stmt) /* transformation not required.  */
    {
      STMT_VINFO_TYPE (stmt_info) = store_vec_info_type;
      return true;
    }

  /** Transform.  **/

  if (vect_print_dump_info (REPORT_DETAILS, UNKNOWN_LOC))
    fprintf (vect_dump, "transform store");

  alignment_support_cheme = vect_supportable_dr_alignment (dr);
  gcc_assert (alignment_support_cheme);
  gcc_assert (alignment_support_cheme = dr_aligned);  /* FORNOW */

  /* Handle use - get the vectorized def from the defining stmt.  */
  vec_oprnd1 = vect_get_vec_def_for_operand (op, stmt);

  /* Handle def.  */
  /* FORNOW: make sure the data reference is aligned.  */
  vect_align_data_ref (stmt);
  data_ref = vect_create_data_ref_ptr (stmt, bsi, NULL_TREE, &dummy, false);
  data_ref = build_fold_indirect_ref (data_ref);

  /* Arguments are ready. create the new vector stmt.  */
  *vec_stmt = build2 (MODIFY_EXPR, vectype, data_ref, vec_oprnd1);
  vect_finish_stmt_generation (stmt, *vec_stmt, bsi);

  return true;
}


/* vectorizable_load.

   Check if STMT reads a non scalar data-ref (array/pointer/structure) that 
   can be vectorized. 
   If VEC_STMT is also passed, vectorize the STMT: create a vectorized 
   stmt to replace it, put it in VEC_STMT, and insert it at BSI.
   Return FALSE if not a vectorizable STMT, TRUE otherwise.  */

bool
vectorizable_load (tree stmt, block_stmt_iterator *bsi, tree *vec_stmt)
{
  tree scalar_dest;
  tree vec_dest = NULL;
  tree data_ref = NULL;
  tree op;
  stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
  struct data_reference *dr = STMT_VINFO_DATA_REF (stmt_info);
  tree vectype = STMT_VINFO_VECTYPE (stmt_info);
  tree new_temp;
  int mode;
  tree init_addr;
  tree new_stmt;
  tree dummy;
  basic_block new_bb;
  loop_vec_info loop_vinfo = STMT_VINFO_LOOP_VINFO (stmt_info);
  struct loop *loop = LOOP_VINFO_LOOP (loop_vinfo);
  edge pe = loop_preheader_edge (loop);
  enum dr_alignment_support alignment_support_cheme;

  /* Is vectorizable load? */

  if (TREE_CODE (stmt) != MODIFY_EXPR)
    return false;

  scalar_dest = TREE_OPERAND (stmt, 0);
  if (TREE_CODE (scalar_dest) != SSA_NAME)
    return false;

  op = TREE_OPERAND (stmt, 1);
  if (TREE_CODE (op) != ARRAY_REF && TREE_CODE (op) != INDIRECT_REF)
    return false;

  if (!STMT_VINFO_DATA_REF (stmt_info))
    return false;

  mode = (int) TYPE_MODE (vectype);

  /* FORNOW. In some cases can vectorize even if data-type not supported
    (e.g. - data copies).  */
  if (mov_optab->handlers[mode].insn_code == CODE_FOR_nothing)
    {
      if (vect_print_dump_info (REPORT_DETAILS, LOOP_LOC (loop_vinfo)))
        fprintf (vect_dump, "Aligned load, but unsupported type.");
      return false;
    }

  if (!vec_stmt) /* transformation not required.  */
    {
      STMT_VINFO_TYPE (stmt_info) = load_vec_info_type;
      return true;
    }

  /** Transform.  **/

  if (vect_print_dump_info (REPORT_DETAILS, UNKNOWN_LOC))
    fprintf (vect_dump, "transform load.");

  alignment_support_cheme = vect_supportable_dr_alignment (dr);
  gcc_assert (alignment_support_cheme);

  if (alignment_support_cheme == dr_aligned
      || alignment_support_cheme == dr_unaligned_supported)
    {
      /* Create:
         p = initial_addr;
         indx = 0;
         loop {
           vec_dest = *(p);
           indx = indx + 1;
         }
      */

      vec_dest = vect_create_destination_var (scalar_dest, vectype);
      data_ref = vect_create_data_ref_ptr (stmt, bsi, NULL_TREE, &dummy, false);
      if (aligned_access_p (dr))
        data_ref = build_fold_indirect_ref (data_ref);
      else
        {
          int mis = DR_MISALIGNMENT (dr);
          tree tmis = (mis == -1 ? size_zero_node : size_int (mis));
          tmis = size_binop (MULT_EXPR, tmis, size_int(BITS_PER_UNIT));
          data_ref = build2 (MISALIGNED_INDIRECT_REF, vectype, data_ref, tmis);
        }
      new_stmt = build2 (MODIFY_EXPR, vectype, vec_dest, data_ref);
      new_temp = make_ssa_name (vec_dest, new_stmt);
      TREE_OPERAND (new_stmt, 0) = new_temp;
      vect_finish_stmt_generation (stmt, new_stmt, bsi);
    }
  else if (alignment_support_cheme == dr_unaligned_software_pipeline)
    {
      /* Create:
         p1 = initial_addr;
         msq_init = *(floor(p1))
         p2 = initial_addr + VS - 1;
         magic = have_builtin ? builtin_result : initial_address;
         indx = 0;
         loop {
           p2' = p2 + indx * vectype_size
           lsq = *(floor(p2'))
           vec_dest = realign_load (msq, lsq, magic)
           indx = indx + 1;
           msq = lsq;
         }
      */

      tree offset;
      tree magic;
      tree phi_stmt;
      tree msq_init;
      tree msq, lsq;
      tree dataref_ptr;
      tree params;

      /* <1> Create msq_init = *(floor(p1)) in the loop preheader  */
      vec_dest = vect_create_destination_var (scalar_dest, vectype);
      data_ref = vect_create_data_ref_ptr (stmt, bsi, NULL_TREE, 
                                           &init_addr, true);
      data_ref = build1 (ALIGN_INDIRECT_REF, vectype, data_ref);
      new_stmt = build2 (MODIFY_EXPR, vectype, vec_dest, data_ref);
      new_temp = make_ssa_name (vec_dest, new_stmt);
      TREE_OPERAND (new_stmt, 0) = new_temp;
      new_bb = bsi_insert_on_edge_immediate (pe, new_stmt);
      gcc_assert (!new_bb);
      msq_init = TREE_OPERAND (new_stmt, 0);


      /* <2> Create lsq = *(floor(p2')) in the loop  */ 
      offset = build_int_cst (integer_type_node, 
                              GET_MODE_NUNITS (TYPE_MODE (vectype)));
      offset = int_const_binop (MINUS_EXPR, offset, integer_one_node, 1);
      vec_dest = vect_create_destination_var (scalar_dest, vectype);
      dataref_ptr = vect_create_data_ref_ptr (stmt, bsi, offset, &dummy, false);
      data_ref = build1 (ALIGN_INDIRECT_REF, vectype, dataref_ptr);
      new_stmt = build2 (MODIFY_EXPR, vectype, vec_dest, data_ref);
      new_temp = make_ssa_name (vec_dest, new_stmt);
      TREE_OPERAND (new_stmt, 0) = new_temp;
      vect_finish_stmt_generation (stmt, new_stmt, bsi);
      lsq = TREE_OPERAND (new_stmt, 0);


      /* <3> */
      if (targetm.vectorize.builtin_mask_for_load)
        {
          /* Create permutation mask, if required, in loop preheader.  */
          tree builtin_decl;
          params = build_tree_list (NULL_TREE, init_addr);
          vec_dest = vect_create_destination_var (scalar_dest, vectype);
          builtin_decl = targetm.vectorize.builtin_mask_for_load ();
          new_stmt = build_function_call_expr (builtin_decl, params);
          new_stmt = build2 (MODIFY_EXPR, vectype, vec_dest, new_stmt);
          new_temp = make_ssa_name (vec_dest, new_stmt);
          TREE_OPERAND (new_stmt, 0) = new_temp;
          new_bb = bsi_insert_on_edge_immediate (pe, new_stmt);
          gcc_assert (!new_bb);
          magic = TREE_OPERAND (new_stmt, 0);

          /* Since we have just created a CALL_EXPR, we may need to
             rename call-clobbered variables.  */
          mark_call_clobbered_vars_to_rename ();
        }
      else
        {
          /* Use current address instead of init_addr for reduced reg pressure.
           */
          magic = dataref_ptr;
        }


      /* <4> Create msq = phi <msq_init, lsq> in loop  */ 
      vec_dest = vect_create_destination_var (scalar_dest, vectype);
      msq = make_ssa_name (vec_dest, NULL_TREE);
      phi_stmt = create_phi_node (msq, loop->header); /* CHECKME */
      SSA_NAME_DEF_STMT (msq) = phi_stmt;
      add_phi_arg (phi_stmt, msq_init, loop_preheader_edge (loop));
      add_phi_arg (phi_stmt, lsq, loop_latch_edge (loop));


      /* <5> Create <vec_dest = realign_load (msq, lsq, magic)> in loop  */
      vec_dest = vect_create_destination_var (scalar_dest, vectype);
      new_stmt = build3 (REALIGN_LOAD_EXPR, vectype, msq, lsq, magic);
      new_stmt = build2 (MODIFY_EXPR, vectype, vec_dest, new_stmt);
      new_temp = make_ssa_name (vec_dest, new_stmt); 
      TREE_OPERAND (new_stmt, 0) = new_temp;
      vect_finish_stmt_generation (stmt, new_stmt, bsi);
    }
  else
    gcc_unreachable ();

  *vec_stmt = new_stmt;
  return true;
}


/* Function vect_transform_stmt.

   Create a vectorized stmt to replace STMT, and insert it at BSI.  */

bool
vect_transform_stmt (tree stmt, block_stmt_iterator *bsi)
{
  bool is_store = false;
  tree vec_stmt = NULL_TREE;
  stmt_vec_info stmt_info = vinfo_for_stmt (stmt);
  bool done;

  switch (STMT_VINFO_TYPE (stmt_info))
    {
    case op_vec_info_type:
      done = vectorizable_operation (stmt, bsi, &vec_stmt);
      gcc_assert (done);
      break;

    case assignment_vec_info_type:
      done = vectorizable_assignment (stmt, bsi, &vec_stmt);
      gcc_assert (done);
      break;

    case load_vec_info_type:
      done = vectorizable_load (stmt, bsi, &vec_stmt);
      gcc_assert (done);
      break;

    case store_vec_info_type:
      done = vectorizable_store (stmt, bsi, &vec_stmt);
      gcc_assert (done);
      is_store = true;
      break;
    default:
      if (vect_print_dump_info (REPORT_DETAILS, UNKNOWN_LOC))
        fprintf (vect_dump, "stmt not supported.");
      gcc_unreachable ();
    }

  STMT_VINFO_VEC_STMT (stmt_info) = vec_stmt;

  return is_store;
}


/* This function builds ni_name = number of iterations loop executes
   on the loop preheader.  */

static tree
vect_build_loop_niters (loop_vec_info loop_vinfo)
{
  tree ni_name, stmt, var;
  edge pe;
  struct loop *loop = LOOP_VINFO_LOOP (loop_vinfo);
  tree ni = unshare_expr (LOOP_VINFO_NITERS (loop_vinfo));

  var = create_tmp_var (TREE_TYPE (ni), "niters");
  add_referenced_tmp_var (var);
  ni_name = force_gimple_operand (ni, &stmt, false, var);

  pe = loop_preheader_edge (loop);
  if (stmt)
    {
      basic_block new_bb = bsi_insert_on_edge_immediate (pe, stmt);
      gcc_assert (!new_bb);
    }
      
  return ni_name;
}


/* This function generates the following statements:

 ni_name = number of iterations loop executes
 ratio = ni_name / vf
 ratio_mult_vf_name = ratio * vf

 and places them at the loop preheader edge.  */

static void 
vect_generate_tmps_on_preheader (loop_vec_info loop_vinfo, 
                                 tree *ni_name_ptr,
                                 tree *ratio_mult_vf_name_ptr, 
                                 tree *ratio_name_ptr)
{

  edge pe;
  basic_block new_bb;
  tree stmt, ni_name;
  tree var;
  tree ratio_name;
  tree ratio_mult_vf_name;
  struct loop *loop = LOOP_VINFO_LOOP (loop_vinfo);
  tree ni = LOOP_VINFO_NITERS (loop_vinfo);
  int vf = LOOP_VINFO_VECT_FACTOR (loop_vinfo);
  tree log_vf = build_int_cst (unsigned_type_node, exact_log2 (vf));

  pe = loop_preheader_edge (loop);

  /* Generate temporary variable that contains 
     number of iterations loop executes.  */

  ni_name = vect_build_loop_niters (loop_vinfo);

  /* Create: ratio = ni >> log2(vf) */

  var = create_tmp_var (TREE_TYPE (ni), "bnd");
  add_referenced_tmp_var (var);
  ratio_name = make_ssa_name (var, NULL_TREE);
  stmt = build2 (MODIFY_EXPR, void_type_node, ratio_name,
           build2 (RSHIFT_EXPR, TREE_TYPE (ni_name), ni_name, log_vf));
  SSA_NAME_DEF_STMT (ratio_name) = stmt;

  pe = loop_preheader_edge (loop);
  new_bb = bsi_insert_on_edge_immediate (pe, stmt);
  gcc_assert (!new_bb);
       
  /* Create: ratio_mult_vf = ratio << log2 (vf).  */

  var = create_tmp_var (TREE_TYPE (ni), "ratio_mult_vf");
  add_referenced_tmp_var (var);
  ratio_mult_vf_name = make_ssa_name (var, NULL_TREE);
  stmt = build2 (MODIFY_EXPR, void_type_node, ratio_mult_vf_name,
           build2 (LSHIFT_EXPR, TREE_TYPE (ratio_name), ratio_name, log_vf));
  SSA_NAME_DEF_STMT (ratio_mult_vf_name) = stmt;

  pe = loop_preheader_edge (loop);
  new_bb = bsi_insert_on_edge_immediate (pe, stmt);
  gcc_assert (!new_bb);

  *ni_name_ptr = ni_name;
  *ratio_mult_vf_name_ptr = ratio_mult_vf_name;
  *ratio_name_ptr = ratio_name;
    
  return;  
}


/*   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)
{
  struct loop *loop = LOOP_VINFO_LOOP (loop_vinfo);
  basic_block exit_bb = loop->exit_edges[0]->dest;
  tree phi, phi1;
  basic_block update_bb = update_e->dest;

  /* gcc_assert (vect_can_advance_ivs_p (loop_vinfo)); */

  /* Make sure there exists a single-predecessor exit bb:  */
  gcc_assert (EDGE_COUNT (exit_bb->preds) == 1);

  for (phi = phi_nodes (loop->header), phi1 = phi_nodes (update_bb); 
       phi && phi1; 
       phi = PHI_CHAIN (phi), phi1 = PHI_CHAIN (phi1))
    {
      tree access_fn = NULL;
      tree evolution_part;
      tree init_expr;
      tree step_expr;
      tree var, stmt, ni, ni_name;
      block_stmt_iterator last_bsi;

      /* Skip virtual phi's.  */
      if (!is_gimple_reg (SSA_NAME_VAR (PHI_RESULT (phi))))
        {
          if (vect_print_dump_info (REPORT_DETAILS, UNKNOWN_LOC))
            fprintf (vect_dump, "virtual phi. skip.");
          continue;
        }

      access_fn = analyze_scalar_evolution (loop, PHI_RESULT (phi)); 
      gcc_assert (access_fn);
      evolution_part =
         unshare_expr (evolution_part_in_loop_num (access_fn, loop->num));
      gcc_assert (evolution_part != NULL_TREE);
      
      /* FORNOW: We do not support IVs whose evolution function is a polynomial
         of degree >= 2 or exponential.  */
      gcc_assert (!tree_is_chrec (evolution_part));

      step_expr = evolution_part;
      init_expr = unshare_expr (initial_condition_in_loop_num (access_fn, 
                                                               loop->num));

      ni = build2 (PLUS_EXPR, TREE_TYPE (init_expr),
                  build2 (MULT_EXPR, TREE_TYPE (niters),
                       niters, step_expr), init_expr);

      var = create_tmp_var (TREE_TYPE (init_expr), "tmp");
      add_referenced_tmp_var (var);

      ni_name = force_gimple_operand (ni, &stmt, false, var);
      
      /* Insert stmt into exit_bb.  */
      last_bsi = bsi_last (exit_bb);
      if (stmt)
        bsi_insert_before (&last_bsi, stmt, BSI_SAME_STMT);   

      /* Fix phi expressions in the successor bb.  */
      gcc_assert (PHI_ARG_DEF_FROM_EDGE (phi1, update_e) ==
                  PHI_ARG_DEF_FROM_EDGE (phi, EDGE_SUCC (loop->latch, 0)));
      SET_PHI_ARG_DEF (phi1, update_e->dest_idx, ni_name);
    }
}


/* Function vect_do_peeling_for_loop_bound

   Peel the last iterations of the loop represented by LOOP_VINFO.
   The peeled iterations form a new epilog loop.  Given that the loop now 
   iterates NITERS times, the new epilog loop iterates
   NITERS % VECTORIZATION_FACTOR times.
   
   The original loop will later be made to iterate 
   NITERS / VECTORIZATION_FACTOR times (this value is placed into RATIO).  */

static void 
vect_do_peeling_for_loop_bound (loop_vec_info loop_vinfo, tree *ratio,
                                struct loops *loops)
{

  tree ni_name, ratio_mult_vf_name;
  struct loop *loop = LOOP_VINFO_LOOP (loop_vinfo);
  struct loop *new_loop;
  edge update_e;
#ifdef ENABLE_CHECKING
  int loop_num;
#endif

  if (vect_print_dump_info (REPORT_DETAILS, UNKNOWN_LOC))
    fprintf (vect_dump, "=== vect_transtorm_for_unknown_loop_bound ===");

  /* Generate the following variables on the preheader of original loop:
         
     ni_name = number of iteration the original loop executes
     ratio = ni_name / vf
     ratio_mult_vf_name = ratio * vf  */
  vect_generate_tmps_on_preheader (loop_vinfo, &ni_name,
                                   &ratio_mult_vf_name, ratio);

  /* Update loop info.  */
  loop->pre_header = loop_preheader_edge (loop)->src;
  loop->pre_header_edges[0] = loop_preheader_edge (loop);

#ifdef ENABLE_CHECKING
  loop_num  = loop->num; 
#endif
  new_loop = slpeel_tree_peel_loop_to_edge (loop, loops, loop->exit_edges[0],
                                            ratio_mult_vf_name, ni_name, false);
#ifdef ENABLE_CHECKING
  gcc_assert (new_loop);
  gcc_assert (loop_num == loop->num);
  slpeel_verify_cfg_after_peeling (loop, new_loop);
#endif

  /* A guard that controls whether the new_loop is to be executed or skipped
     is placed in LOOP->exit.  LOOP->exit therefore has two successors - one
     is the preheader of NEW_LOOP, where the IVs from LOOP are used.  The other
     is a bb after NEW_LOOP, where these IVs are not used.  Find the edge that
     is on the path where the LOOP IVs are used and need to be updated.  */

  if (EDGE_PRED (new_loop->pre_header, 0)->src == loop->exit_edges[0]->dest)
    update_e = EDGE_PRED (new_loop->pre_header, 0);
  else
    update_e = EDGE_PRED (new_loop->pre_header, 1);

  /* Update IVs of original loop as if they were advanced 
     by ratio_mult_vf_name steps.  */
  vect_update_ivs_after_vectorizer (loop_vinfo, ratio_mult_vf_name, update_e); 

  /* After peeling we have to reset scalar evolution analyzer.  */
  scev_reset ();

  return;
}


/* Function vect_gen_niters_for_prolog_loop

   Set the number of iterations for the loop represented by LOOP_VINFO
   to the minimum between LOOP_NITERS (the original iteration count of the loop)
   and the misalignment of DR - the first 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:

   compute address misalignment in bytes:
   addr_mis = addr & (vectype_size - 1)

   prolog_niters = min ( LOOP_NITERS , (VF - addr_mis/elem_size)&(VF-1) )
   
   (elem_size = element type size; an element is the scalar element 
        whose type is the inner type of the vectype)  */

static tree 
vect_gen_niters_for_prolog_loop (loop_vec_info loop_vinfo, tree loop_niters)
{
  struct data_reference *dr = LOOP_VINFO_UNALIGNED_DR (loop_vinfo);
  int vf = LOOP_VINFO_VECT_FACTOR (loop_vinfo);
  struct loop *loop = LOOP_VINFO_LOOP (loop_vinfo);
  tree var, stmt;
  tree iters, iters_name;
  edge pe;
  basic_block new_bb;
  tree dr_stmt = DR_STMT (dr);
  stmt_vec_info stmt_info = vinfo_for_stmt (dr_stmt);
  tree vectype = STMT_VINFO_VECTYPE (stmt_info);
  int vectype_align = TYPE_ALIGN (vectype) / BITS_PER_UNIT;
  tree elem_misalign;
  tree byte_misalign;
  tree new_stmts = NULL_TREE;
  tree start_addr = 
        vect_create_addr_base_for_vector_ref (dr_stmt, &new_stmts, NULL_TREE);
  tree ptr_type = TREE_TYPE (start_addr);
  tree size = TYPE_SIZE (ptr_type);
  tree type = lang_hooks.types.type_for_size (tree_low_cst (size, 1), 1);
  tree vectype_size_minus_1 = build_int_cst (type, vectype_align - 1);
  tree vf_minus_1 = build_int_cst (unsigned_type_node, vf - 1);
  tree niters_type = TREE_TYPE (loop_niters);
  tree elem_size_log = 
        build_int_cst (unsigned_type_node, exact_log2 (vectype_align/vf));
  tree vf_tree = build_int_cst (unsigned_type_node, vf);

  pe = loop_preheader_edge (loop); 
  new_bb = bsi_insert_on_edge_immediate (pe, new_stmts); 
  gcc_assert (!new_bb);

  /* Create:  byte_misalign = addr & (vectype_size - 1)  */
  byte_misalign = build2 (BIT_AND_EXPR, type, start_addr, vectype_size_minus_1);

  /* Create:  elem_misalign = byte_misalign / element_size  */
  elem_misalign = 
        build2 (RSHIFT_EXPR, unsigned_type_node, byte_misalign, elem_size_log);
  
  /* Create:  (niters_type) (VF - elem_misalign)&(VF - 1)  */
  iters = build2 (MINUS_EXPR, unsigned_type_node, vf_tree, elem_misalign);
  iters = build2 (BIT_AND_EXPR, unsigned_type_node, iters, vf_minus_1);
  iters = fold_convert (niters_type, iters);
  
  /* Create:  prolog_loop_niters = min (iters, loop_niters) */
  /* If the loop bound is known at compile time we already verified that it is
     greater than vf; since the misalignment ('iters') is at most vf, there's
     no need to generate the MIN_EXPR in this case.  */
  if (TREE_CODE (loop_niters) != INTEGER_CST)
    iters = build2 (MIN_EXPR, niters_type, iters, loop_niters);

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

  /* Insert stmt on loop preheader edge.  */
  pe = loop_preheader_edge (loop);
  if (stmt)
    {
      basic_block new_bb = bsi_insert_on_edge_immediate (pe, stmt);
      gcc_assert (!new_bb);
    }

  return iters_name; 
}


/* Function vect_update_inits_of_dr

   NITERS iterations were peeled from LOOP.  DR represents a data reference
   in LOOP.  This function updates the information recorded in DR to
   account for the fact that the first NITERS iterations had already been 
   executed.  Specifically, it updates the OFFSET field of stmt_info.  */

static void
vect_update_inits_of_dr (struct data_reference *dr, tree niters)
{
  stmt_vec_info stmt_info = vinfo_for_stmt (DR_STMT (dr));
  tree offset = STMT_VINFO_VECT_INIT_OFFSET (stmt_info);
      
  niters = fold (build2 (MULT_EXPR, TREE_TYPE (niters), niters, 
                         STMT_VINFO_VECT_STEP (stmt_info)));
  offset = fold (build2 (PLUS_EXPR, TREE_TYPE (offset), offset, niters));
  STMT_VINFO_VECT_INIT_OFFSET (stmt_info) = offset;
}


/* Function vect_update_inits_of_drs

   NITERS iterations were peeled from the loop represented by LOOP_VINFO.  
   This function updates the information recorded for the data references in 
   the loop to account for the fact that the first NITERS iterations had 
   already been executed.  Specifically, it updates the initial_condition of the
   access_function of all the data_references in the loop.  */

static void
vect_update_inits_of_drs (loop_vec_info loop_vinfo, tree niters)
{
  unsigned int i;
  varray_type loop_write_datarefs = LOOP_VINFO_DATAREF_WRITES (loop_vinfo);
  varray_type loop_read_datarefs = LOOP_VINFO_DATAREF_READS (loop_vinfo);

  if (vect_dump && (dump_flags & TDF_DETAILS))
    fprintf (vect_dump, "=== vect_update_inits_of_dr ===");

  for (i = 0; i < VARRAY_ACTIVE_SIZE (loop_write_datarefs); i++)
    {
      struct data_reference *dr = VARRAY_GENERIC_PTR (loop_write_datarefs, i);
      vect_update_inits_of_dr (dr, niters);
    }

  for (i = 0; i < VARRAY_ACTIVE_SIZE (loop_read_datarefs); i++)
    {
      struct data_reference *dr = VARRAY_GENERIC_PTR (loop_read_datarefs, i);
      vect_update_inits_of_dr (dr, niters);
    }
}


/* Function vect_do_peeling_for_alignment

   Peel the first 'niters' iterations of the loop represented by LOOP_VINFO.
   'niters' is set to the misalignment of one of the data references in the
   loop, thereby forcing it to refer to an aligned location at the beginning
   of the execution of this loop.  The data reference for which we are
   peeling is recorded in LOOP_VINFO_UNALIGNED_DR.  */

static void
vect_do_peeling_for_alignment (loop_vec_info loop_vinfo, struct loops *loops)
{
  struct loop *loop = LOOP_VINFO_LOOP (loop_vinfo);
  tree niters_of_prolog_loop, ni_name;
  tree n_iters;
  struct loop *new_loop;

  if (vect_print_dump_info (REPORT_DETAILS, UNKNOWN_LOC))
    fprintf (vect_dump, "=== vect_do_peeling_for_alignment ===");

  ni_name = vect_build_loop_niters (loop_vinfo);
  niters_of_prolog_loop = vect_gen_niters_for_prolog_loop (loop_vinfo, ni_name);
  
  /* Peel the prolog loop and iterate it niters_of_prolog_loop.  */
  new_loop = 
        slpeel_tree_peel_loop_to_edge (loop, loops, loop_preheader_edge (loop), 
                                       niters_of_prolog_loop, ni_name, true); 
#ifdef ENABLE_CHECKING
  gcc_assert (new_loop);
  slpeel_verify_cfg_after_peeling (new_loop, loop);
#endif

  /* Update number of times loop executes.  */
  n_iters = LOOP_VINFO_NITERS (loop_vinfo);
  LOOP_VINFO_NITERS (loop_vinfo) =
    build2 (MINUS_EXPR, TREE_TYPE (n_iters), n_iters, niters_of_prolog_loop);

  /* Update the init conditions of the access functions of all data refs.  */
  vect_update_inits_of_drs (loop_vinfo, niters_of_prolog_loop);

  /* After peeling we have to reset scalar evolution analyzer.  */
  scev_reset ();

  return;
}


/* Function vect_transform_loop.

   The analysis phase has determined that the loop is vectorizable.
   Vectorize the loop - created vectorized stmts to replace the scalar
   stmts in the loop, and update the loop exit condition.  */

void
vect_transform_loop (loop_vec_info loop_vinfo, 
                     struct loops *loops ATTRIBUTE_UNUSED)
{
  struct loop *loop = LOOP_VINFO_LOOP (loop_vinfo);
  basic_block *bbs = LOOP_VINFO_BBS (loop_vinfo);
  int nbbs = loop->num_nodes;
  block_stmt_iterator si;
  int i;
  tree ratio = NULL;
  int vectorization_factor = LOOP_VINFO_VECT_FACTOR (loop_vinfo);

  if (vect_print_dump_info (REPORT_DETAILS, UNKNOWN_LOC))
    fprintf (vect_dump, "=== vec_transform_loop ===");

  
  /* Peel the loop if there are data refs with unknown alignment.
     Only one data ref with unknown store is allowed.  */

  if (LOOP_DO_PEELING_FOR_ALIGNMENT (loop_vinfo))
    vect_do_peeling_for_alignment (loop_vinfo, loops);
  
  /* If the loop has a symbolic number of iterations 'n' (i.e. it's not a
     compile time constant), or it is a constant that doesn't divide by the
     vectorization factor, then an epilog loop needs to be created.
     We therefore duplicate the loop: the original loop will be vectorized,
     and will compute the first (n/VF) iterations. The second copy of the loop
     will remain scalar and will compute the remaining (n%VF) iterations.
     (VF is the vectorization factor).  */

  if (!LOOP_VINFO_NITERS_KNOWN_P (loop_vinfo)
      || (LOOP_VINFO_NITERS_KNOWN_P (loop_vinfo)
          && LOOP_VINFO_INT_NITERS (loop_vinfo) % vectorization_factor != 0))
    vect_do_peeling_for_loop_bound (loop_vinfo, &ratio, loops);
  else
    ratio = build_int_cst (TREE_TYPE (LOOP_VINFO_NITERS (loop_vinfo)),
                LOOP_VINFO_INT_NITERS (loop_vinfo) / vectorization_factor);

  /* 1) Make sure the loop header has exactly two entries
     2) Make sure we have a preheader basic block.  */

  gcc_assert (EDGE_COUNT (loop->header->preds) == 2);

  loop_split_edge_with (loop_preheader_edge (loop), NULL);


  /* FORNOW: the vectorizer supports only loops which body consist
     of one basic block (header + empty latch). When the vectorizer will 
     support more involved loop forms, the order by which the BBs are 
     traversed need to be reconsidered.  */

  for (i = 0; i < nbbs; i++)
    {
      basic_block bb = bbs[i];

      for (si = bsi_start (bb); !bsi_end_p (si);)
        {
          tree stmt = bsi_stmt (si);
          stmt_vec_info stmt_info;
          bool is_store;

          if (vect_print_dump_info (REPORT_DETAILS, UNKNOWN_LOC))
            {
              fprintf (vect_dump, "------>vectorizing statement: ");
              print_generic_expr (vect_dump, stmt, TDF_SLIM);
            }   
          stmt_info = vinfo_for_stmt (stmt);
          gcc_assert (stmt_info);
          if (!STMT_VINFO_RELEVANT_P (stmt_info))
            {
              bsi_next (&si);
              continue;
            }
#ifdef ENABLE_CHECKING
          /* FORNOW: Verify that all stmts operate on the same number of
                     units and no inner unrolling is necessary.  */
          gcc_assert 
                (GET_MODE_NUNITS (TYPE_MODE (STMT_VINFO_VECTYPE (stmt_info)))
                 == vectorization_factor);
#endif
          /* -------- vectorize statement ------------ */
          if (vect_print_dump_info (REPORT_DETAILS, UNKNOWN_LOC))
            fprintf (vect_dump, "transform statement.");

          is_store = vect_transform_stmt (stmt, &si);
          if (is_store)
            {
              /* free the attached stmt_vec_info and remove the stmt.  */
              stmt_ann_t ann = stmt_ann (stmt);
              free (stmt_info);
              set_stmt_info (ann, NULL);
              bsi_remove (&si);
              continue;
            }

          bsi_next (&si);
        }                       /* stmts in BB */
    }                           /* BBs in loop */

  slpeel_make_loop_iterate_ntimes (loop, ratio);

  if (vect_print_dump_info (REPORT_VECTORIZED_LOOPS, LOOP_LOC (loop_vinfo)))
    fprintf (vect_dump, "LOOP VECTORIZED.");
}