loop-init.c

/* Loop optimizer initialization routines and RTL loop optimization passes.
   Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2010
   Free Software Foundation, Inc.

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 "tm.h"
#include "rtl.h"
#include "hard-reg-set.h"
#include "obstack.h"
#include "basic-block.h"
#include "cfgloop.h"
#include "cfglayout.h"
#include "tree-pass.h"
#include "timevar.h"
#include "flags.h"
#include "df.h"
#include "ggc.h"


/* Initialize loop structures.  This is used by the tree and RTL loop
   optimizers.  FLAGS specify what properties to compute and/or ensure for
   loops.  */

void
loop_optimizer_init (unsigned flags)
{
  struct loops *loops;

  gcc_assert (!current_loops);
  loops = ggc_alloc_cleared_loops ();

  /* Find the loops.  */

  flow_loops_find (loops);
  current_loops = loops;

  if (flags & LOOPS_MAY_HAVE_MULTIPLE_LATCHES)
    {
      /* If the loops may have multiple latches, we cannot canonicalize
	 them further (and most of the loop manipulation functions will
	 not work).  However, we avoid modifying cfg, which some
	 passes may want.  */
      gcc_assert ((flags & ~(LOOPS_MAY_HAVE_MULTIPLE_LATCHES
			     | LOOPS_HAVE_RECORDED_EXITS)) == 0);
      loops_state_set (LOOPS_MAY_HAVE_MULTIPLE_LATCHES);
    }
  else
    disambiguate_loops_with_multiple_latches ();

  /* Create pre-headers.  */
  if (flags & LOOPS_HAVE_PREHEADERS)
    {
      int cp_flags = CP_SIMPLE_PREHEADERS;

      if (flags & LOOPS_HAVE_FALLTHRU_PREHEADERS)
        cp_flags |= CP_FALLTHRU_PREHEADERS;

      create_preheaders (cp_flags);
    }

  /* Force all latches to have only single successor.  */
  if (flags & LOOPS_HAVE_SIMPLE_LATCHES)
    force_single_succ_latches ();

  /* Mark irreducible loops.  */
  if (flags & LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
    mark_irreducible_loops ();

  if (flags & LOOPS_HAVE_RECORDED_EXITS)
    record_loop_exits ();

  /* Dump loops.  */
  flow_loops_dump (dump_file, NULL, 1);

#ifdef ENABLE_CHECKING
  verify_dominators (CDI_DOMINATORS);
  verify_loop_structure ();
#endif
}

/* Finalize loop structures.  */

void
loop_optimizer_finalize (void)
{
  loop_iterator li;
  struct loop *loop;
  basic_block bb;

  gcc_assert (current_loops != NULL);

  FOR_EACH_LOOP (li, loop, 0)
    {
      free_simple_loop_desc (loop);
    }

  /* Clean up.  */
  if (loops_state_satisfies_p (LOOPS_HAVE_RECORDED_EXITS))
    release_recorded_exits ();
  flow_loops_free (current_loops);
  ggc_free (current_loops);
  current_loops = NULL;

  FOR_ALL_BB (bb)
    {
      bb->loop_father = NULL;
    }
}


/* Gate for the RTL loop superpass.  The actual passes are subpasses.
   See passes.c for more on that.  */

static bool
gate_handle_loop2 (void)
{
  return (optimize > 0
  	  && (flag_move_loop_invariants
              || flag_unswitch_loops
              || flag_peel_loops
              || flag_unroll_loops
#ifdef HAVE_doloop_end
	      || (flag_branch_on_count_reg && HAVE_doloop_end)
#endif
	      ));
}

struct rtl_opt_pass pass_loop2 =
{
 {
  RTL_PASS,
  "loop2",                              /* name */
  gate_handle_loop2, 		        /* gate */
  NULL,                                 /* execute */
  NULL,                                 /* sub */
  NULL,                                 /* next */
  0,                                    /* static_pass_number */
  TV_LOOP,                              /* tv_id */
  0,                                    /* properties_required */
  0,                                    /* properties_provided */
  0,                                    /* properties_destroyed */
  0,                                    /* todo_flags_start */
  TODO_ggc_collect                      /* todo_flags_finish */
 }
};


/* Initialization of the RTL loop passes.  */
static unsigned int
rtl_loop_init (void)
{
  gcc_assert (current_ir_type () == IR_RTL_CFGLAYOUT);

  if (dump_file)
    dump_flow_info (dump_file, dump_flags);

  loop_optimizer_init (LOOPS_NORMAL);
  return 0;
}

struct rtl_opt_pass pass_rtl_loop_init =
{
 {
  RTL_PASS,
  "loop2_init",                           /* name */
  NULL,                                 /* gate */
  rtl_loop_init,                        /* execute */
  NULL,                                 /* sub */
  NULL,                                 /* next */
  0,                                    /* static_pass_number */
  TV_LOOP,                              /* tv_id */
  0,                                    /* properties_required */
  0,                                    /* properties_provided */
  0,                                    /* properties_destroyed */
  0,                                    /* todo_flags_start */
  TODO_verify_rtl_sharing               /* todo_flags_finish */
 }
};


/* Finalization of the RTL loop passes.  */

static unsigned int
rtl_loop_done (void)
{
  loop_optimizer_finalize ();
  free_dominance_info (CDI_DOMINATORS);

  cleanup_cfg (0);
  if (dump_file)
    dump_flow_info (dump_file, dump_flags);

  return 0;
}

struct rtl_opt_pass pass_rtl_loop_done =
{
 {
  RTL_PASS,
  "loop2_done",                          /* name */
  NULL,                                 /* gate */
  rtl_loop_done,                        /* execute */
  NULL,                                 /* sub */
  NULL,                                 /* next */
  0,                                    /* static_pass_number */
  TV_LOOP,                              /* tv_id */
  0,                                    /* properties_required */
  0,                                    /* properties_provided */
  0,                                    /* properties_destroyed */
  0,                                    /* todo_flags_start */
  TODO_verify_flow
    | TODO_verify_rtl_sharing           /* todo_flags_finish */
 }
};


/* Loop invariant code motion.  */
static bool
gate_rtl_move_loop_invariants (void)
{
  return flag_move_loop_invariants;
}

static unsigned int
rtl_move_loop_invariants (void)
{
  if (number_of_loops () > 1)
    move_loop_invariants ();
  return 0;
}

struct rtl_opt_pass pass_rtl_move_loop_invariants =
{
 {
  RTL_PASS,
  "loop2_invariant",                    /* name */
  gate_rtl_move_loop_invariants,        /* gate */
  rtl_move_loop_invariants,             /* execute */
  NULL,                                 /* sub */
  NULL,                                 /* next */
  0,                                    /* static_pass_number */
  TV_LOOP_MOVE_INVARIANTS,              /* tv_id */
  0,                                    /* properties_required */
  0,                                    /* properties_provided */
  0,                                    /* properties_destroyed */
  0,                                    /* todo_flags_start */
  TODO_df_verify |
  TODO_df_finish | TODO_verify_rtl_sharing  /* todo_flags_finish */
 }
};


/* Loop unswitching for RTL.  */
static bool
gate_rtl_unswitch (void)
{
  return flag_unswitch_loops;
}

static unsigned int
rtl_unswitch (void)
{
  if (number_of_loops () > 1)
    unswitch_loops ();
  return 0;
}

struct rtl_opt_pass pass_rtl_unswitch =
{
 {
  RTL_PASS,
  "loop2_unswitch",                      /* name */
  gate_rtl_unswitch,                    /* gate */
  rtl_unswitch,                         /* execute */
  NULL,                                 /* sub */
  NULL,                                 /* next */
  0,                                    /* static_pass_number */
  TV_LOOP_UNSWITCH,                     /* tv_id */
  0,                                    /* properties_required */
  0,                                    /* properties_provided */
  0,                                    /* properties_destroyed */
  0,                                    /* todo_flags_start */
  TODO_verify_rtl_sharing,              /* todo_flags_finish */
 }
};


/* Loop unswitching for RTL.  */
static bool
gate_rtl_unroll_and_peel_loops (void)
{
  return (flag_peel_loops || flag_unroll_loops || flag_unroll_all_loops);
}

static unsigned int
rtl_unroll_and_peel_loops (void)
{
  if (number_of_loops () > 1)
    {
      int flags = 0;
      if (dump_file)
	df_dump (dump_file);

      if (flag_peel_loops)
	flags |= UAP_PEEL;
      if (flag_unroll_loops)
	flags |= UAP_UNROLL;
      if (flag_unroll_all_loops)
	flags |= UAP_UNROLL_ALL;

      unroll_and_peel_loops (flags);
    }
  return 0;
}

struct rtl_opt_pass pass_rtl_unroll_and_peel_loops =
{
 {
  RTL_PASS,
  "loop2_unroll",                        /* name */
  gate_rtl_unroll_and_peel_loops,       /* gate */
  rtl_unroll_and_peel_loops,            /* execute */
  NULL,                                 /* sub */
  NULL,                                 /* next */
  0,                                    /* static_pass_number */
  TV_LOOP_UNROLL,                       /* tv_id */
  0,                                    /* properties_required */
  0,                                    /* properties_provided */
  0,                                    /* properties_destroyed */
  0,                                    /* todo_flags_start */
  TODO_verify_rtl_sharing,              /* todo_flags_finish */
 }
};


/* The doloop optimization.  */
static bool
gate_rtl_doloop (void)
{
#ifdef HAVE_doloop_end
  return (flag_branch_on_count_reg && HAVE_doloop_end);
#else
  return 0;
#endif
}

static unsigned int
rtl_doloop (void)
{
#ifdef HAVE_doloop_end
  if (number_of_loops () > 1)
    doloop_optimize_loops ();
#endif
  return 0;
}

struct rtl_opt_pass pass_rtl_doloop =
{
 {
  RTL_PASS,
  "loop2_doloop",                        /* name */
  gate_rtl_doloop,                      /* gate */
  rtl_doloop,                           /* execute */
  NULL,                                 /* sub */
  NULL,                                 /* next */
  0,                                    /* static_pass_number */
  TV_LOOP_DOLOOP,                       /* tv_id */
  0,                                    /* properties_required */
  0,                                    /* properties_provided */
  0,                                    /* properties_destroyed */
  0,                                    /* todo_flags_start */
  TODO_verify_rtl_sharing               /* todo_flags_finish */
 }
};