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/* Integrated Register Allocator.  Changing code and generating moves.

   Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011

   Free Software Foundation, Inc.

   Contributed by Vladimir Makarov <vmakarov@redhat.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/>.  */

/* When we have more one region, we need to change the original RTL

   code after coloring.  Let us consider two allocnos representing the

   same pseudo-register outside and inside a region respectively.

   They can get different hard-registers.  The reload pass works on

   pseudo registers basis and there is no way to say the reload that

   pseudo could be in different registers and it is even more

   difficult to say in what places of the code the pseudo should have

   particular hard-registers.  So in this case IRA has to create and

   use a new pseudo-register inside the region and adds code to move

   allocno values on the region's borders.  This is done by the code

   in this file.

   The code makes top-down traversal of the regions and generate new

   pseudos and the move code on the region borders.  In some

   complicated cases IRA can create a new pseudo used temporarily to

   move allocno values when a swap of values stored in two

   hard-registers is needed (e.g. two allocnos representing different

   pseudos outside region got respectively hard registers 1 and 2 and

   the corresponding allocnos inside the region got respectively hard

   registers 2 and 1).  At this stage, the new pseudo is marked as

   spilled.

   IRA still creates the pseudo-register and the moves on the region

   borders even when the both corresponding allocnos were assigned to

   the same hard-register.  It is done because, if the reload pass for

   some reason spills a pseudo-register representing the original

   pseudo outside or inside the region, the effect will be smaller

   because another pseudo will still be in the hard-register.  In most

   cases, this is better then spilling the original pseudo in its

   whole live-range.  If reload does not change the allocation for the

   two pseudo-registers, the trivial move will be removed by

   post-reload optimizations.

   IRA does not generate a new pseudo and moves for the allocno values

   if the both allocnos representing an original pseudo inside and

   outside region assigned to the same hard register when the register

   pressure in the region for the corresponding pressure class is less

   than number of available hard registers for given pressure class.

   IRA also does some optimizations to remove redundant moves which is

   transformed into stores by the reload pass on CFG edges

   representing exits from the region.

   IRA tries to reduce duplication of code generated on CFG edges

   which are enters and exits to/from regions by moving some code to

   the edge sources or destinations when it is possible.  */

#include "config.h"

#include "system.h"

#include "coretypes.h"

#include "tm.h"

#include "regs.h"

#include "rtl.h"

#include "tm_p.h"

#include "target.h"

#include "flags.h"

#include "obstack.h"

#include "bitmap.h"

#include "hard-reg-set.h"

#include "basic-block.h"

#include "expr.h"

#include "recog.h"

#include "params.h"

#include "timevar.h"

#include "tree-pass.h"

#include "output.h"

#include "reload.h"

#include "df.h"

#include "ira-int.h"

/* Data used to emit live range split insns and to flattening IR.  */

ira_emit_data_t ira_allocno_emit_data;

/* Definitions for vectors of pointers.  */

typedef void *void_p;

DEF_VEC_P (void_p);

DEF_VEC_ALLOC_P (void_p,heap);

/* Pointers to data allocated for allocnos being created during

   emitting.  Usually there are quite few such allocnos because they

   are created only for resolving loop in register shuffling.  */

static VEC(void_p, heap) *new_allocno_emit_data_vec;

/* Allocate and initiate the emit data.  */

void

ira_initiate_emit_data (void)

{

  ira_allocno_t a;

  ira_allocno_iterator ai;

  ira_allocno_emit_data

    = (ira_emit_data_t) ira_allocate (ira_allocnos_num

                                      * sizeof (struct ira_emit_data));

  memset (ira_allocno_emit_data, 0,

          ira_allocnos_num * sizeof (struct ira_emit_data));

  FOR_EACH_ALLOCNO (a, ai)

    ALLOCNO_ADD_DATA (a) = ira_allocno_emit_data + ALLOCNO_NUM (a);

  new_allocno_emit_data_vec = VEC_alloc (void_p, heap, 50);

}

/* Free the emit data.  */

void

ira_finish_emit_data (void)

{

  void_p p;

  ira_allocno_t a;

  ira_allocno_iterator ai;

  ira_free (ira_allocno_emit_data);

  FOR_EACH_ALLOCNO (a, ai)

    ALLOCNO_ADD_DATA (a) = NULL;

  for (;VEC_length (void_p, new_allocno_emit_data_vec) != 0;)

    {

      p = VEC_pop (void_p, new_allocno_emit_data_vec);

      ira_free (p);

    }

  VEC_free (void_p, heap, new_allocno_emit_data_vec);

}

/* Create and return a new allocno with given REGNO and

   LOOP_TREE_NODE.  Allocate emit data for it.  */

static ira_allocno_t

create_new_allocno (int regno, ira_loop_tree_node_t loop_tree_node)

{

  ira_allocno_t a;

  a = ira_create_allocno (regno, false, loop_tree_node);

  ALLOCNO_ADD_DATA (a) = ira_allocate (sizeof (struct ira_emit_data));

  memset (ALLOCNO_ADD_DATA (a), 0, sizeof (struct ira_emit_data));

  VEC_safe_push (void_p, heap, new_allocno_emit_data_vec, ALLOCNO_ADD_DATA (a));

  return a;

}

/* See comments below.  */

typedef struct move *move_t;

/* The structure represents an allocno move.  Both allocnos have the

   same origional regno but different allocation.  */

struct move

{

  /* The allocnos involved in the move.  */

  ira_allocno_t from, to;

  /* The next move in the move sequence.  */

  move_t next;

  /* Used for finding dependencies.  */

  bool visited_p;

  /* The size of the following array. */

  int deps_num;

  /* Moves on which given move depends on.  Dependency can be cyclic.

     It means we need a temporary to generates the moves.  Sequence

     A1->A2, B1->B2 where A1 and B2 are assigned to reg R1 and A2 and

     B1 are assigned to reg R2 is an example of the cyclic

     dependencies.  */

  move_t *deps;

  /* First insn generated for the move.  */

  rtx insn;

};

/* Array of moves (indexed by BB index) which should be put at the

   start/end of the corresponding basic blocks.  */

static move_t *at_bb_start, *at_bb_end;

/* Max regno before renaming some pseudo-registers.  For example, the

   same pseudo-register can be renamed in a loop if its allocation is

   different outside the loop.  */

static int max_regno_before_changing;

/* Return new move of allocnos TO and FROM.  */

static move_t

create_move (ira_allocno_t to, ira_allocno_t from)

{

  move_t move;

  move = (move_t) ira_allocate (sizeof (struct move));

  move->deps = NULL;

  move->deps_num = 0;

  move->to = to;

  move->from = from;

  move->next = NULL;

  move->insn = NULL_RTX;

  move->visited_p = false;

  return move;

}

/* Free memory for MOVE and its dependencies.  */

static void

free_move (move_t move)

{

  if (move->deps != NULL)

    ira_free (move->deps);

  ira_free (move);

}

/* Free memory for list of the moves given by its HEAD.  */

static void

free_move_list (move_t head)

{

  move_t next;

  for (; head != NULL; head = next)

    {

      next = head->next;

      free_move (head);

    }

}

/* Return TRUE if the move list LIST1 and LIST2 are equal (two

   moves are equal if they involve the same allocnos).  */

static bool

eq_move_lists_p (move_t list1, move_t list2)

{

  for (; list1 != NULL && list2 != NULL;

       list1 = list1->next, list2 = list2->next)

    if (list1->from != list2->from || list1->to != list2->to)

      return false;

  return list1 == list2;

}

/* Print move list LIST into file F.  */

static void

print_move_list (FILE *f, move_t list)

{

  for (; list != NULL; list = list->next)

    fprintf (f, " a%dr%d->a%dr%d",

             ALLOCNO_NUM (list->from), ALLOCNO_REGNO (list->from),

             ALLOCNO_NUM (list->to), ALLOCNO_REGNO (list->to));

  fprintf (f, "\n");

}

extern void ira_debug_move_list (move_t list);

/* Print move list LIST into stderr.  */

void

ira_debug_move_list (move_t list)

{

  print_move_list (stderr, list);

}

/* This recursive function changes pseudo-registers in *LOC if it is

   necessary.  The function returns TRUE if a change was done.  */

static bool

change_regs (rtx *loc)

{

  int i, regno, result = false;

  const char *fmt;

  enum rtx_code code;

  rtx reg;

  if (*loc == NULL_RTX)

    return false;

  code = GET_CODE (*loc);

  if (code == REG)

    {

      regno = REGNO (*loc);

      if (regno < FIRST_PSEUDO_REGISTER)

        return false;

      if (regno >= max_regno_before_changing)

        /* It is a shared register which was changed already.  */

        return false;

      if (ira_curr_regno_allocno_map[regno] == NULL)

        return false;

      reg = allocno_emit_reg (ira_curr_regno_allocno_map[regno]);

      if (reg == *loc)

        return false;

      *loc = reg;

      return true;

    }

  fmt = GET_RTX_FORMAT (code);

  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)

    {

      if (fmt[i] == 'e')

        result = change_regs (&XEXP (*loc, i)) || result;

      else if (fmt[i] == 'E')

        {

          int j;

          for (j = XVECLEN (*loc, i) - 1; j >= 0; j--)

            result = change_regs (&XVECEXP (*loc, i, j)) || result;

        }

    }

  return result;

}

/* Attach MOVE to the edge E.  The move is attached to the head of the

   list if HEAD_P is TRUE.  */

static void

add_to_edge_list (edge e, move_t move, bool head_p)

{

  move_t last;

  if (head_p || e->aux == NULL)

    {

      move->next = (move_t) e->aux;

      e->aux = move;

    }

  else

    {

      for (last = (move_t) e->aux; last->next != NULL; last = last->next)

        ;

      last->next = move;

      move->next = NULL;

    }

}

/* Create and return new pseudo-register with the same attributes as

   ORIGINAL_REG.  */

static rtx

create_new_reg (rtx original_reg)

{

  rtx new_reg;

  new_reg = gen_reg_rtx (GET_MODE (original_reg));

  ORIGINAL_REGNO (new_reg) = ORIGINAL_REGNO (original_reg);

  REG_USERVAR_P (new_reg) = REG_USERVAR_P (original_reg);

  REG_POINTER (new_reg) = REG_POINTER (original_reg);

  REG_ATTRS (new_reg) = REG_ATTRS (original_reg);

  if (internal_flag_ira_verbose > 3 && ira_dump_file != NULL)

    fprintf (ira_dump_file, "      Creating newreg=%i from oldreg=%i\n",

             REGNO (new_reg), REGNO (original_reg));

  return new_reg;

}

/* Return TRUE if loop given by SUBNODE inside the loop given by

   NODE.  */

static bool

subloop_tree_node_p (ira_loop_tree_node_t subnode, ira_loop_tree_node_t node)

{

  for (; subnode != NULL; subnode = subnode->parent)

    if (subnode == node)

      return true;

  return false;

}

/* Set up member `reg' to REG for allocnos which has the same regno as

   ALLOCNO and which are inside the loop corresponding to ALLOCNO. */

static void

set_allocno_reg (ira_allocno_t allocno, rtx reg)

{

  int regno;

  ira_allocno_t a;

  ira_loop_tree_node_t node;

  node = ALLOCNO_LOOP_TREE_NODE (allocno);

  for (a = ira_regno_allocno_map[ALLOCNO_REGNO (allocno)];

       a != NULL;

       a = ALLOCNO_NEXT_REGNO_ALLOCNO (a))

    if (subloop_tree_node_p (ALLOCNO_LOOP_TREE_NODE (a), node))

      ALLOCNO_EMIT_DATA (a)->reg = reg;

  for (a = ALLOCNO_CAP (allocno); a != NULL; a = ALLOCNO_CAP (a))

    ALLOCNO_EMIT_DATA (a)->reg = reg;

  regno = ALLOCNO_REGNO (allocno);

  for (a = allocno;;)

    {

      if (a == NULL || (a = ALLOCNO_CAP (a)) == NULL)

        {

          node = node->parent;

          if (node == NULL)

            break;

          a = node->regno_allocno_map[regno];

        }

      if (a == NULL)

        continue;

      if (ALLOCNO_EMIT_DATA (a)->child_renamed_p)

        break;

      ALLOCNO_EMIT_DATA (a)->child_renamed_p = true;

    }

}

/* Return true if there is an entry to given loop not from its parent

   (or grandparent) block.  For example, it is possible for two

   adjacent loops inside another loop.  */

static bool

entered_from_non_parent_p (ira_loop_tree_node_t loop_node)

{

  ira_loop_tree_node_t bb_node, src_loop_node, parent;

  edge e;

  edge_iterator ei;

  for (bb_node = loop_node->children;

       bb_node != NULL;

       bb_node = bb_node->next)

    if (bb_node->bb != NULL)

      {

        FOR_EACH_EDGE (e, ei, bb_node->bb->preds)

          if (e->src != ENTRY_BLOCK_PTR

              && (src_loop_node = IRA_BB_NODE (e->src)->parent) != loop_node)

            {

              for (parent = src_loop_node->parent;

                   parent != NULL;

                   parent = parent->parent)

                if (parent == loop_node)

                  break;

              if (parent != NULL)

                /* That is an exit from a nested loop -- skip it.  */

                continue;

              for (parent = loop_node->parent;

                   parent != NULL;

                   parent = parent->parent)

                if (src_loop_node == parent)

                  break;

              if (parent == NULL)

                return true;

            }

      }

  return false;

}

/* Set up ENTERED_FROM_NON_PARENT_P for each loop region.  */

static void

setup_entered_from_non_parent_p (void)

{

  unsigned int i;

  loop_p loop;

  ira_assert (current_loops != NULL);

  FOR_EACH_VEC_ELT (loop_p, ira_loops.larray, i, loop)

    if (ira_loop_nodes[i].regno_allocno_map != NULL)

      ira_loop_nodes[i].entered_from_non_parent_p

        = entered_from_non_parent_p (&ira_loop_nodes[i]);

}

/* Return TRUE if move of SRC_ALLOCNO (assigned to hard register) to

   DEST_ALLOCNO (assigned to memory) can be removed beacuse it does

   not change value of the destination.  One possible reason for this

   is the situation when SRC_ALLOCNO is not modified in the

   corresponding loop.  */

static bool

store_can_be_removed_p (ira_allocno_t src_allocno, ira_allocno_t dest_allocno)

{

  int regno, orig_regno;

  ira_allocno_t a;

  ira_loop_tree_node_t node;

  ira_assert (ALLOCNO_CAP_MEMBER (src_allocno) == NULL

              && ALLOCNO_CAP_MEMBER (dest_allocno) == NULL);

  orig_regno = ALLOCNO_REGNO (src_allocno);

  regno = REGNO (allocno_emit_reg (dest_allocno));

  for (node = ALLOCNO_LOOP_TREE_NODE (src_allocno);

       node != NULL;

       node = node->parent)

    {

      a = node->regno_allocno_map[orig_regno];

      ira_assert (a != NULL);

      if (REGNO (allocno_emit_reg (a)) == (unsigned) regno)

        /* We achieved the destination and everything is ok.  */

        return true;

      else if (bitmap_bit_p (node->modified_regnos, orig_regno))

        return false;

      else if (node->entered_from_non_parent_p)

        /* If there is a path from a destination loop block to the

           source loop header containing basic blocks of non-parents

           (grandparents) of the source loop, we should have checked

           modifications of the pseudo on this path too to decide

           about possibility to remove the store.  It could be done by

           solving a data-flow problem.  Unfortunately such global

           solution would complicate IR flattening.  Therefore we just

           prohibit removal of the store in such complicated case.  */

        return false;

    }

  /* It is actually a loop entry -- do not remove the store.  */

  return false;

}

/* Generate and attach moves to the edge E.  This looks at the final

   regnos of allocnos living on the edge with the same original regno

   to figure out when moves should be generated.  */

static void

generate_edge_moves (edge e)

{

  ira_loop_tree_node_t src_loop_node, dest_loop_node;

  unsigned int regno;

  bitmap_iterator bi;

  ira_allocno_t src_allocno, dest_allocno, *src_map, *dest_map;

  move_t move;

  src_loop_node = IRA_BB_NODE (e->src)->parent;

  dest_loop_node = IRA_BB_NODE (e->dest)->parent;

  e->aux = NULL;

  if (src_loop_node == dest_loop_node)

    return;

  src_map = src_loop_node->regno_allocno_map;

  dest_map = dest_loop_node->regno_allocno_map;

  EXECUTE_IF_SET_IN_REG_SET (DF_LR_IN (e->dest),

                             FIRST_PSEUDO_REGISTER, regno, bi)

    if (bitmap_bit_p (DF_LR_OUT (e->src), regno))

      {

        src_allocno = src_map[regno];

        dest_allocno = dest_map[regno];

        if (REGNO (allocno_emit_reg (src_allocno))

            == REGNO (allocno_emit_reg (dest_allocno)))

          continue;

        /* Remove unnecessary stores at the region exit.  We should do

           this for readonly memory for sure and this is guaranteed by

           that we never generate moves on region borders (see

           checking ira_reg_equiv_invariant_p in function

           change_loop).  */

        if (ALLOCNO_HARD_REGNO (dest_allocno) < 0

            && ALLOCNO_HARD_REGNO (src_allocno) >= 0

            && store_can_be_removed_p (src_allocno, dest_allocno))

          {

            ALLOCNO_EMIT_DATA (src_allocno)->mem_optimized_dest = dest_allocno;

            ALLOCNO_EMIT_DATA (dest_allocno)->mem_optimized_dest_p = true;

            if (internal_flag_ira_verbose > 3 && ira_dump_file != NULL)

              fprintf (ira_dump_file, "      Remove r%d:a%d->a%d(mem)\n",

                       regno, ALLOCNO_NUM (src_allocno),

                       ALLOCNO_NUM (dest_allocno));

            continue;

          }

        move = create_move (dest_allocno, src_allocno);

        add_to_edge_list (e, move, true);

    }

}

/* Bitmap of allocnos local for the current loop.  */

static bitmap local_allocno_bitmap;

/* This bitmap is used to find that we need to generate and to use a

   new pseudo-register when processing allocnos with the same original

   regno.  */

static bitmap used_regno_bitmap;

/* This bitmap contains regnos of allocnos which were renamed locally

   because the allocnos correspond to disjoint live ranges in loops

   with a common parent.  */

static bitmap renamed_regno_bitmap;

/* Change (if necessary) pseudo-registers inside loop given by loop

   tree node NODE.  */

static void

change_loop (ira_loop_tree_node_t node)

{

  bitmap_iterator bi;

  unsigned int i;

  int regno;

  bool used_p;

  ira_allocno_t allocno, parent_allocno, *map;

  rtx insn, original_reg;

  enum reg_class aclass, pclass;

  ira_loop_tree_node_t parent;

  if (node != ira_loop_tree_root)

    {

      ira_assert (current_loops != NULL);

      if (node->bb != NULL)

        {

          FOR_BB_INSNS (node->bb, insn)

            if (INSN_P (insn) && change_regs (&insn))

              {

                df_insn_rescan (insn);

                df_notes_rescan (insn);

              }

          return;

        }

      if (internal_flag_ira_verbose > 3 && ira_dump_file != NULL)

        fprintf (ira_dump_file,

                 "      Changing RTL for loop %d (header bb%d)\n",

                 node->loop_num, node->loop->header->index);

      parent = ira_curr_loop_tree_node->parent;

      map = parent->regno_allocno_map;

      EXECUTE_IF_SET_IN_REG_SET (ira_curr_loop_tree_node->border_allocnos,

                                 0, i, bi)

        {

          allocno = ira_allocnos[i];

          regno = ALLOCNO_REGNO (allocno);

          aclass = ALLOCNO_CLASS (allocno);

          pclass = ira_pressure_class_translate[aclass];

          parent_allocno = map[regno];

          ira_assert (regno < ira_reg_equiv_len);

          /* We generate the same hard register move because the

             reload pass can put an allocno into memory in this case

             we will have live range splitting.  If it does not happen

             such the same hard register moves will be removed.  The

             worst case when the both allocnos are put into memory by

             the reload is very rare.  */

          if (parent_allocno != NULL

              && (ALLOCNO_HARD_REGNO (allocno)

                  == ALLOCNO_HARD_REGNO (parent_allocno))

              && (ALLOCNO_HARD_REGNO (allocno) < 0

                  || (parent->reg_pressure[pclass] + 1

                      <= ira_available_class_regs[pclass])

                  || TEST_HARD_REG_BIT (ira_prohibited_mode_move_regs

                                        [ALLOCNO_MODE (allocno)],

                                        ALLOCNO_HARD_REGNO (allocno))

                  /* don't create copies because reload can spill an

                     allocno set by copy although the allocno will not

                     get memory slot.  */

                  || ira_reg_equiv_invariant_p[regno]

                  || ira_reg_equiv_const[regno] != NULL_RTX))

            continue;

          original_reg = allocno_emit_reg (allocno);

          if (parent_allocno == NULL

              || (REGNO (allocno_emit_reg (parent_allocno))

                  == REGNO (original_reg)))

            {

              if (internal_flag_ira_verbose > 3 && ira_dump_file)

                fprintf (ira_dump_file, "  %i vs parent %i:",

                         ALLOCNO_HARD_REGNO (allocno),

                         ALLOCNO_HARD_REGNO (parent_allocno));

              set_allocno_reg (allocno, create_new_reg (original_reg));

            }

        }

    }

  /* Rename locals: Local allocnos with same regno in different loops

     might get the different hard register.  So we need to change

     ALLOCNO_REG.  */

  bitmap_and_compl (local_allocno_bitmap,

                    ira_curr_loop_tree_node->all_allocnos,

                    ira_curr_loop_tree_node->border_allocnos);

  EXECUTE_IF_SET_IN_REG_SET (local_allocno_bitmap, 0, i, bi)

    {

      allocno = ira_allocnos[i];

      regno = ALLOCNO_REGNO (allocno);

      if (ALLOCNO_CAP_MEMBER (allocno) != NULL)

        continue;

      used_p = !bitmap_set_bit (used_regno_bitmap, regno);

      ALLOCNO_EMIT_DATA (allocno)->somewhere_renamed_p = true;

      if (! used_p)

        continue;

      bitmap_set_bit (renamed_regno_bitmap, regno);

      set_allocno_reg (allocno, create_new_reg (allocno_emit_reg (allocno)));

    }

}

/* Process to set up flag somewhere_renamed_p.  */

static void

set_allocno_somewhere_renamed_p (void)

{

  unsigned int regno;

  ira_allocno_t allocno;

  ira_allocno_iterator ai;

  FOR_EACH_ALLOCNO (allocno, ai)

    {

      regno = ALLOCNO_REGNO (allocno);

      if (bitmap_bit_p (renamed_regno_bitmap, regno)

          && REGNO (allocno_emit_reg (allocno)) == regno)

        ALLOCNO_EMIT_DATA (allocno)->somewhere_renamed_p = true;

    }

}

/* Return TRUE if move lists on all edges given in vector VEC are

   equal.  */

static bool

eq_edge_move_lists_p (VEC(edge,gc) *vec)

{

  move_t list;

  int i;

  list = (move_t) EDGE_I (vec, 0)->aux;

  for (i = EDGE_COUNT (vec) - 1; i > 0; i--)

    if (! eq_move_lists_p (list, (move_t) EDGE_I (vec, i)->aux))

      return false;

  return true;

}

/* Look at all entry edges (if START_P) or exit edges of basic block

   BB and put move lists at the BB start or end if it is possible.  In

   other words, this decreases code duplication of allocno moves.  */

static void

unify_moves (basic_block bb, bool start_p)

{

  int i;

  edge e;

  move_t list;

  VEC(edge,gc) *vec;

  vec = (start_p ? bb->preds : bb->succs);

  if (EDGE_COUNT (vec) == 0 || ! eq_edge_move_lists_p (vec))

    return;

  e = EDGE_I (vec, 0);

  list = (move_t) e->aux;