tree-vectorizer.c

/* Vectorizer
   Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
   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 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/>.  */

/* Loop and basic block vectorizer.

  This file contains drivers for the three vectorizers:
  (1) loop vectorizer (inter-iteration parallelism),
  (2) loop-aware SLP (intra-iteration parallelism) (invoked by the loop
      vectorizer)
  (3) BB vectorizer (out-of-loops), aka SLP

  The rest of the vectorizer's code is organized as follows:
  - tree-vect-loop.c - loop specific parts such as reductions, etc. These are
    used by drivers (1) and (2).
  - tree-vect-loop-manip.c - vectorizer's loop control-flow utilities, used by
    drivers (1) and (2).
  - tree-vect-slp.c - BB vectorization specific analysis and transformation,
    used by drivers (2) and (3).
  - tree-vect-stmts.c - statements analysis and transformation (used by all).
  - tree-vect-data-refs.c - vectorizer specific data-refs analysis and
    manipulations (used by all).
  - tree-vect-patterns.c - vectorizable code patterns detector (used by all)

  Here's a poor attempt at illustrating that:

     tree-vectorizer.c:
     loop_vect()  loop_aware_slp()  slp_vect()
          |        /           \          /
          |       /             \        /
          tree-vect-loop.c  tree-vect-slp.c
                | \      \  /      /   |
                |  \      \/      /    |
                |   \     /\     /     |
                |    \   /  \   /      |
         tree-vect-stmts.c  tree-vect-data-refs.c
                       \      /
                    tree-vect-patterns.c
*/

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "ggc.h"
#include "tree.h"
#include "tree-pretty-print.h"
#include "tree-flow.h"
#include "tree-dump.h"
#include "cfgloop.h"
#include "cfglayout.h"
#include "tree-vectorizer.h"
#include "tree-pass.h"
#include "timevar.h"

/* vect_dump will be set to stderr or dump_file if exist.  */
FILE *vect_dump;

/* vect_verbosity_level set to an invalid value
   to mark that it's uninitialized.  */
static enum vect_verbosity_levels vect_verbosity_level = MAX_VERBOSITY_LEVEL;

/* Loop or bb location.  */
LOC vect_location;

/* Vector mapping GIMPLE stmt to stmt_vec_info. */
VEC(vec_void_p,heap) *stmt_vec_info_vec;



/* Function vect_set_dump_settings.

   Fix the verbosity level of the vectorizer if the
   requested level was not set explicitly using the flag
   -ftree-vectorizer-verbose=N.
   Decide where to print the debugging information (dump_file/stderr).
   If the user defined the verbosity level, but there is no dump file,
   print to stderr, otherwise print to the dump file.  */

static void
vect_set_dump_settings (bool slp)
{
  vect_dump = dump_file;

  /* Check if the verbosity level was defined by the user:  */
  if (user_vect_verbosity_level != MAX_VERBOSITY_LEVEL)
    {
      vect_verbosity_level = user_vect_verbosity_level;
      /* Ignore user defined verbosity if dump flags require higher level of
         verbosity.  */
      if (dump_file)
        {
          if (((dump_flags & TDF_DETAILS)
                && vect_verbosity_level >= REPORT_DETAILS)
  	       || ((dump_flags & TDF_STATS)
	            && vect_verbosity_level >= REPORT_UNVECTORIZED_LOCATIONS))
            return;
        }
      else
        {
          /* If there is no dump file, print to stderr in case of loop
             vectorization.  */
          if (!slp)
            vect_dump = stderr;

          return;
        }
    }

  /* User didn't specify verbosity level:  */
  if (dump_file && (dump_flags & TDF_DETAILS))
    vect_verbosity_level = REPORT_DETAILS;
  else if (dump_file && (dump_flags & TDF_STATS))
    vect_verbosity_level = REPORT_UNVECTORIZED_LOCATIONS;
  else
    vect_verbosity_level = REPORT_NONE;

  gcc_assert (dump_file || vect_verbosity_level == REPORT_NONE);
}


/* Function debug_loop_details.

   For vectorization debug dumps.  */

bool
vect_print_dump_info (enum vect_verbosity_levels vl)
{
  if (vl > vect_verbosity_level)
    return false;

  if (!current_function_decl || !vect_dump)
    return false;

  if (vect_location == UNKNOWN_LOC)
    fprintf (vect_dump, "\n%s:%d: note: ",
	     DECL_SOURCE_FILE (current_function_decl),
	     DECL_SOURCE_LINE (current_function_decl));
  else
    fprintf (vect_dump, "\n%s:%d: note: ",
	     LOC_FILE (vect_location), LOC_LINE (vect_location));

  return true;
}


/* Function vectorize_loops.

   Entry point to loop vectorization phase.  */

unsigned
vectorize_loops (void)
{
  unsigned int i;
  unsigned int num_vectorized_loops = 0;
  unsigned int vect_loops_num;
  loop_iterator li;
  struct loop *loop;

  vect_loops_num = number_of_loops ();

  /* Bail out if there are no loops.  */
  if (vect_loops_num <= 1)
    return 0;

  /* Fix the verbosity level if not defined explicitly by the user.  */
  vect_set_dump_settings (false);

  init_stmt_vec_info_vec ();

  /*  ----------- Analyze loops. -----------  */

  /* If some loop was duplicated, it gets bigger number
     than all previously defined loops.  This fact allows us to run
     only over initial loops skipping newly generated ones.  */
  FOR_EACH_LOOP (li, loop, 0)
    if (optimize_loop_nest_for_speed_p (loop))
      {
	loop_vec_info loop_vinfo;

	vect_location = find_loop_location (loop);
	loop_vinfo = vect_analyze_loop (loop);
	loop->aux = loop_vinfo;

	if (!loop_vinfo || !LOOP_VINFO_VECTORIZABLE_P (loop_vinfo))
	  continue;

	vect_transform_loop (loop_vinfo);
	num_vectorized_loops++;
      }

  vect_location = UNKNOWN_LOC;

  statistics_counter_event (cfun, "Vectorized loops", num_vectorized_loops);
  if (vect_print_dump_info (REPORT_UNVECTORIZED_LOCATIONS)
      || (num_vectorized_loops > 0
	  && vect_print_dump_info (REPORT_VECTORIZED_LOCATIONS)))
    fprintf (vect_dump, "vectorized %u loops in function.\n",
	     num_vectorized_loops);

  /*  ----------- Finalize. -----------  */

  mark_sym_for_renaming (gimple_vop (cfun));

  for (i = 1; i < vect_loops_num; i++)
    {
      loop_vec_info loop_vinfo;

      loop = get_loop (i);
      if (!loop)
	continue;
      loop_vinfo = (loop_vec_info) loop->aux;
      destroy_loop_vec_info (loop_vinfo, true);
      loop->aux = NULL;
    }

  free_stmt_vec_info_vec ();

  return num_vectorized_loops > 0 ? TODO_cleanup_cfg : 0;
}


/*  Entry point to basic block SLP phase.  */

static unsigned int
execute_vect_slp (void)
{
  basic_block bb;

  /* Fix the verbosity level if not defined explicitly by the user.  */
  vect_set_dump_settings (true);

  init_stmt_vec_info_vec ();

  FOR_EACH_BB (bb)
    {
      vect_location = find_bb_location (bb);

      if (vect_slp_analyze_bb (bb))
        {
          vect_slp_transform_bb (bb);

          if (vect_print_dump_info (REPORT_VECTORIZED_LOCATIONS))
            fprintf (vect_dump, "basic block vectorized using SLP\n");
        }
    }

  free_stmt_vec_info_vec ();
  return 0;
}

static bool
gate_vect_slp (void)
{
  /* Apply SLP either if the vectorizer is on and the user didn't specify
     whether to run SLP or not, or if the SLP flag was set by the user.  */
  return ((flag_tree_vectorize != 0 && flag_tree_slp_vectorize != 0)
          || flag_tree_slp_vectorize == 1);
}

struct gimple_opt_pass pass_slp_vectorize =
{
 {
  GIMPLE_PASS,
  "slp",                                /* name */
  gate_vect_slp,                        /* gate */
  execute_vect_slp,                     /* execute */
  NULL,                                 /* sub */
  NULL,                                 /* next */
  0,                                    /* static_pass_number */
  TV_TREE_SLP_VECTORIZATION,            /* tv_id */
  PROP_ssa | PROP_cfg,                  /* properties_required */
  0,                                    /* properties_provided */
  0,                                    /* properties_destroyed */
  0,                                    /* todo_flags_start */
  TODO_ggc_collect
    | TODO_verify_ssa
    | TODO_dump_func
    | TODO_update_ssa
    | TODO_verify_stmts                 /* todo_flags_finish */
 }
};


/* Increase alignment of global arrays to improve vectorization potential.
   TODO:
   - Consider also structs that have an array field.
   - Use ipa analysis to prune arrays that can't be vectorized?
     This should involve global alignment analysis and in the future also
     array padding.  */

static unsigned int
increase_alignment (void)
{
  struct varpool_node *vnode;

  /* Increase the alignment of all global arrays for vectorization.  */
  for (vnode = varpool_nodes_queue;
       vnode;
       vnode = vnode->next_needed)
    {
      tree vectype, decl = vnode->decl;
      tree t;
      unsigned int alignment;

      t = TREE_TYPE(decl);
      if (TREE_CODE (t) != ARRAY_TYPE)
        continue;
      vectype = get_vectype_for_scalar_type (strip_array_types (t));
      if (!vectype)
        continue;
      alignment = TYPE_ALIGN (vectype);
      if (DECL_ALIGN (decl) >= alignment)
        continue;

      if (vect_can_force_dr_alignment_p (decl, alignment))
        {
          DECL_ALIGN (decl) = TYPE_ALIGN (vectype);
          DECL_USER_ALIGN (decl) = 1;
          if (dump_file)
            {
              fprintf (dump_file, "Increasing alignment of decl: ");
              print_generic_expr (dump_file, decl, TDF_SLIM);
	      fprintf (dump_file, "\n");
            }
        }
    }
  return 0;
}


static bool
gate_increase_alignment (void)
{
  return flag_section_anchors && flag_tree_vectorize;
}


struct simple_ipa_opt_pass pass_ipa_increase_alignment =
{
 {
  SIMPLE_IPA_PASS,
  "increase_alignment",                 /* name */
  gate_increase_alignment,              /* gate */
  increase_alignment,                   /* execute */
  NULL,                                 /* sub */
  NULL,                                 /* next */
  0,                                    /* static_pass_number */
  TV_IPA_OPT,                           /* tv_id */
  0,                                    /* properties_required */
  0,                                    /* properties_provided */
  0,                                    /* properties_destroyed */
  0,                                    /* todo_flags_start */
  0                                     /* todo_flags_finish */
 }
};