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/* Convert a program in SSA form into Normal form.

   Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010

   Free Software Foundation, Inc.

   Contributed by Andrew Macleod <amacleod@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/>.  */

#include "config.h"

#include "system.h"

#include "coretypes.h"

#include "tm.h"

#include "tree.h"

#include "ggc.h"

#include "basic-block.h"

#include "diagnostic.h"

#include "bitmap.h"

#include "tree-flow.h"

#include "timevar.h"

#include "tree-dump.h"

#include "tree-pass.h"

#include "toplev.h"

#include "expr.h"

#include "ssaexpand.h"

DEF_VEC_I(source_location);

DEF_VEC_ALLOC_I(source_location,heap);

/* Used to hold all the components required to do SSA PHI elimination.

   The node and pred/succ list is a simple linear list of nodes and

   edges represented as pairs of nodes.

   The predecessor and successor list:  Nodes are entered in pairs, where

   [0] ->PRED, [1]->SUCC.  All the even indexes in the array represent

   predecessors, all the odd elements are successors.

   Rationale:

   When implemented as bitmaps, very large programs SSA->Normal times were

   being dominated by clearing the interference graph.

   Typically this list of edges is extremely small since it only includes

   PHI results and uses from a single edge which have not coalesced with

   each other.  This means that no virtual PHI nodes are included, and

   empirical evidence suggests that the number of edges rarely exceed

   3, and in a bootstrap of GCC, the maximum size encountered was 7.

   This also limits the number of possible nodes that are involved to

   rarely more than 6, and in the bootstrap of gcc, the maximum number

   of nodes encountered was 12.  */

typedef struct _elim_graph {

  /* Size of the elimination vectors.  */

  int size;

  /* List of nodes in the elimination graph.  */

  VEC(int,heap) *nodes;

  /*  The predecessor and successor edge list.  */

  VEC(int,heap) *edge_list;

  /* Source locus on each edge */

  VEC(source_location,heap) *edge_locus;

  /* Visited vector.  */

  sbitmap visited;

  /* Stack for visited nodes.  */

  VEC(int,heap) *stack;

  /* The variable partition map.  */

  var_map map;

  /* Edge being eliminated by this graph.  */

  edge e;

  /* List of constant copies to emit.  These are pushed on in pairs.  */

  VEC(int,heap) *const_dests;

  VEC(tree,heap) *const_copies;

  /* Source locations for any constant copies.  */

  VEC(source_location,heap) *copy_locus;

} *elim_graph;

/* For an edge E find out a good source location to associate with

   instructions inserted on edge E.  If E has an implicit goto set,

   use its location.  Otherwise search instructions in predecessors

   of E for a location, and use that one.  That makes sense because

   we insert on edges for PHI nodes, and effects of PHIs happen on

   the end of the predecessor conceptually.  */

static void

set_location_for_edge (edge e)

{

  if (e->goto_locus)

    {

      set_curr_insn_source_location (e->goto_locus);

      set_curr_insn_block (e->goto_block);

    }

  else

    {

      basic_block bb = e->src;

      gimple_stmt_iterator gsi;

      do

        {

          for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi); gsi_prev (&gsi))

            {

              gimple stmt = gsi_stmt (gsi);

              if (is_gimple_debug (stmt))

                continue;

              if (gimple_has_location (stmt) || gimple_block (stmt))

                {

                  set_curr_insn_source_location (gimple_location (stmt));

                  set_curr_insn_block (gimple_block (stmt));

                  return;

                }

            }

          /* Nothing found in this basic block.  Make a half-assed attempt

             to continue with another block.  */

          if (single_pred_p (bb))

            bb = single_pred (bb);

          else

            bb = e->src;

        }

      while (bb != e->src);

    }

}

/* Emit insns to copy SRC into DEST converting SRC if necessary.  As

   SRC/DEST might be BLKmode memory locations SIZEEXP is a tree from

   which we deduce the size to copy in that case.  */

static inline rtx

emit_partition_copy (rtx dest, rtx src, int unsignedsrcp, tree sizeexp)

{

  rtx seq;

  start_sequence ();

  if (GET_MODE (src) != VOIDmode && GET_MODE (src) != GET_MODE (dest))

    src = convert_to_mode (GET_MODE (dest), src, unsignedsrcp);

  if (GET_MODE (src) == BLKmode)

    {

      gcc_assert (GET_MODE (dest) == BLKmode);

      emit_block_move (dest, src, expr_size (sizeexp), BLOCK_OP_NORMAL);

    }

  else

    emit_move_insn (dest, src);

  seq = get_insns ();

  end_sequence ();

  return seq;

}

/* Insert a copy instruction from partition SRC to DEST onto edge E.  */

static void

insert_partition_copy_on_edge (edge e, int dest, int src, source_location locus)

{

  tree var;

  rtx seq;

  if (dump_file && (dump_flags & TDF_DETAILS))

    {

      fprintf (dump_file,

               "Inserting a partition copy on edge BB%d->BB%d :"

               "PART.%d = PART.%d",

               e->src->index,

               e->dest->index, dest, src);

      fprintf (dump_file, "\n");

    }

  gcc_assert (SA.partition_to_pseudo[dest]);

  gcc_assert (SA.partition_to_pseudo[src]);

  set_location_for_edge (e);

  /* If a locus is provided, override the default.  */

  if (locus)

    set_curr_insn_source_location (locus);

  var = partition_to_var (SA.map, src);

  seq = emit_partition_copy (SA.partition_to_pseudo[dest],

                             SA.partition_to_pseudo[src],

                             TYPE_UNSIGNED (TREE_TYPE (var)),

                             var);

  insert_insn_on_edge (seq, e);

}

/* Insert a copy instruction from expression SRC to partition DEST

   onto edge E.  */

static void

insert_value_copy_on_edge (edge e, int dest, tree src, source_location locus)

{

  rtx seq, x;

  enum machine_mode dest_mode, src_mode;

  int unsignedp;

  tree var;

  if (dump_file && (dump_flags & TDF_DETAILS))

    {

      fprintf (dump_file,

               "Inserting a value copy on edge BB%d->BB%d : PART.%d = ",

               e->src->index,

               e->dest->index, dest);

      print_generic_expr (dump_file, src, TDF_SLIM);

      fprintf (dump_file, "\n");

    }

  gcc_assert (SA.partition_to_pseudo[dest]);

  set_location_for_edge (e);

  /* If a locus is provided, override the default.  */

  if (locus)

    set_curr_insn_source_location (locus);

  start_sequence ();

  var = SSA_NAME_VAR (partition_to_var (SA.map, dest));

  src_mode = TYPE_MODE (TREE_TYPE (src));

  dest_mode = promote_decl_mode (var, &unsignedp);

  gcc_assert (src_mode == TYPE_MODE (TREE_TYPE (var)));

  gcc_assert (dest_mode == GET_MODE (SA.partition_to_pseudo[dest]));

  if (src_mode != dest_mode)

    {

      x = expand_expr (src, NULL, src_mode, EXPAND_NORMAL);

      x = convert_modes (dest_mode, src_mode, x, unsignedp);

    }

  else if (src_mode == BLKmode)

    {

      x = SA.partition_to_pseudo[dest];

      store_expr (src, x, 0, false);

    }

  else

    x = expand_expr (src, SA.partition_to_pseudo[dest],

                     dest_mode, EXPAND_NORMAL);

  if (x != SA.partition_to_pseudo[dest])

    emit_move_insn (SA.partition_to_pseudo[dest], x);

  seq = get_insns ();

  end_sequence ();

  insert_insn_on_edge (seq, e);

}

/* Insert a copy instruction from RTL expression SRC to partition DEST

   onto edge E.  */

static void

insert_rtx_to_part_on_edge (edge e, int dest, rtx src, int unsignedsrcp,

                            source_location locus)

{

  rtx seq;

  if (dump_file && (dump_flags & TDF_DETAILS))

    {

      fprintf (dump_file,

               "Inserting a temp copy on edge BB%d->BB%d : PART.%d = ",

               e->src->index,

               e->dest->index, dest);

      print_simple_rtl (dump_file, src);

      fprintf (dump_file, "\n");

    }

  gcc_assert (SA.partition_to_pseudo[dest]);

  set_location_for_edge (e);

  /* If a locus is provided, override the default.  */

  if (locus)

    set_curr_insn_source_location (locus);

  /* We give the destination as sizeexp in case src/dest are BLKmode

     mems.  Usually we give the source.  As we result from SSA names

     the left and right size should be the same (and no WITH_SIZE_EXPR

     involved), so it doesn't matter.  */

  seq = emit_partition_copy (SA.partition_to_pseudo[dest],

                             src, unsignedsrcp,

                             partition_to_var (SA.map, dest));

  insert_insn_on_edge (seq, e);

}

/* Insert a copy instruction from partition SRC to RTL lvalue DEST

   onto edge E.  */

static void

insert_part_to_rtx_on_edge (edge e, rtx dest, int src, source_location locus)

{

  tree var;

  rtx seq;

  if (dump_file && (dump_flags & TDF_DETAILS))

    {

      fprintf (dump_file,

               "Inserting a temp copy on edge BB%d->BB%d : ",

               e->src->index,

               e->dest->index);

      print_simple_rtl (dump_file, dest);

      fprintf (dump_file, "= PART.%d\n", src);

    }

  gcc_assert (SA.partition_to_pseudo[src]);

  set_location_for_edge (e);

  /* If a locus is provided, override the default.  */

  if (locus)

    set_curr_insn_source_location (locus);

  var = partition_to_var (SA.map, src);

  seq = emit_partition_copy (dest,

                             SA.partition_to_pseudo[src],

                             TYPE_UNSIGNED (TREE_TYPE (var)),

                             var);

  insert_insn_on_edge (seq, e);

}

/* Create an elimination graph with SIZE nodes and associated data

   structures.  */

static elim_graph

new_elim_graph (int size)

{

  elim_graph g = (elim_graph) xmalloc (sizeof (struct _elim_graph));

  g->nodes = VEC_alloc (int, heap, 30);

  g->const_dests = VEC_alloc (int, heap, 20);

  g->const_copies = VEC_alloc (tree, heap, 20);

  g->copy_locus = VEC_alloc (source_location, heap, 10);

  g->edge_list = VEC_alloc (int, heap, 20);

  g->edge_locus = VEC_alloc (source_location, heap, 10);

  g->stack = VEC_alloc (int, heap, 30);

  g->visited = sbitmap_alloc (size);

  return g;

}

/* Empty elimination graph G.  */

static inline void

clear_elim_graph (elim_graph g)

{

  VEC_truncate (int, g->nodes, 0);

  VEC_truncate (int, g->edge_list, 0);

  VEC_truncate (source_location, g->edge_locus, 0);

}

/* Delete elimination graph G.  */

static inline void

delete_elim_graph (elim_graph g)

{

  sbitmap_free (g->visited);

  VEC_free (int, heap, g->stack);

  VEC_free (int, heap, g->edge_list);

  VEC_free (tree, heap, g->const_copies);

  VEC_free (int, heap, g->const_dests);

  VEC_free (int, heap, g->nodes);

  VEC_free (source_location, heap, g->copy_locus);

  VEC_free (source_location, heap, g->edge_locus);

  free (g);

}

/* Return the number of nodes in graph G.  */

static inline int

elim_graph_size (elim_graph g)

{

  return VEC_length (int, g->nodes);

}

/* Add NODE to graph G, if it doesn't exist already.  */

static inline void

elim_graph_add_node (elim_graph g, int node)

{

  int x;

  int t;

  for (x = 0; VEC_iterate (int, g->nodes, x, t); x++)

    if (t == node)

      return;

  VEC_safe_push (int, heap, g->nodes, node);

}

/* Add the edge PRED->SUCC to graph G.  */

static inline void

elim_graph_add_edge (elim_graph g, int pred, int succ, source_location locus)

{

  VEC_safe_push (int, heap, g->edge_list, pred);

  VEC_safe_push (int, heap, g->edge_list, succ);

  VEC_safe_push (source_location, heap, g->edge_locus, locus);

}

/* Remove an edge from graph G for which NODE is the predecessor, and

   return the successor node.  -1 is returned if there is no such edge.  */

static inline int

elim_graph_remove_succ_edge (elim_graph g, int node, source_location *locus)

{

  int y;

  unsigned x;

  for (x = 0; x < VEC_length (int, g->edge_list); x += 2)

    if (VEC_index (int, g->edge_list, x) == node)

      {

        VEC_replace (int, g->edge_list, x, -1);

        y = VEC_index (int, g->edge_list, x + 1);

        VEC_replace (int, g->edge_list, x + 1, -1);

        *locus = VEC_index (source_location, g->edge_locus, x / 2);

        VEC_replace (source_location, g->edge_locus, x / 2, UNKNOWN_LOCATION);

        return y;

      }

  *locus = UNKNOWN_LOCATION;

  return -1;

}

/* Find all the nodes in GRAPH which are successors to NODE in the

   edge list.  VAR will hold the partition number found.  CODE is the

   code fragment executed for every node found.  */

#define FOR_EACH_ELIM_GRAPH_SUCC(GRAPH, NODE, VAR, LOCUS, CODE)         \

do {                                                                    \

  unsigned x_;                                                          \

  int y_;                                                               \

  for (x_ = 0; x_ < VEC_length (int, (GRAPH)->edge_list); x_ += 2)       \

    {                                                                   \

      y_ = VEC_index (int, (GRAPH)->edge_list, x_);                     \

      if (y_ != (NODE))                                                 \

        continue;                                                       \

      (VAR) = VEC_index (int, (GRAPH)->edge_list, x_ + 1);              \

      (LOCUS) = VEC_index (source_location, (GRAPH)->edge_locus, x_ / 2); \

      CODE;                                                             \

    }                                                                   \

} while (0)

/* Find all the nodes which are predecessors of NODE in the edge list for

   GRAPH.  VAR will hold the partition number found.  CODE is the

   code fragment executed for every node found.  */

#define FOR_EACH_ELIM_GRAPH_PRED(GRAPH, NODE, VAR, LOCUS, CODE)         \

do {                                                                    \

  unsigned x_;                                                          \

  int y_;                                                               \

  for (x_ = 0; x_ < VEC_length (int, (GRAPH)->edge_list); x_ += 2)       \

    {                                                                   \

      y_ = VEC_index (int, (GRAPH)->edge_list, x_ + 1);                 \

      if (y_ != (NODE))                                                 \

        continue;                                                       \

      (VAR) = VEC_index (int, (GRAPH)->edge_list, x_);                  \

      (LOCUS) = VEC_index (source_location, (GRAPH)->edge_locus, x_ / 2); \

      CODE;                                                             \

    }                                                                   \

} while (0)

/* Add T to elimination graph G.  */

static inline void

eliminate_name (elim_graph g, int T)

{

  elim_graph_add_node (g, T);

}

/* Build elimination graph G for basic block BB on incoming PHI edge

   G->e.  */

static void

eliminate_build (elim_graph g)

{

  tree Ti;

  int p0, pi;

  gimple_stmt_iterator gsi;

  clear_elim_graph (g);

  for (gsi = gsi_start_phis (g->e->dest); !gsi_end_p (gsi); gsi_next (&gsi))

    {

      gimple phi = gsi_stmt (gsi);

      source_location locus;

      p0 = var_to_partition (g->map, gimple_phi_result (phi));

      /* Ignore results which are not in partitions.  */

      if (p0 == NO_PARTITION)

        continue;

      Ti = PHI_ARG_DEF (phi, g->e->dest_idx);

      locus = gimple_phi_arg_location_from_edge (phi, g->e);

      /* If this argument is a constant, or a SSA_NAME which is being

         left in SSA form, just queue a copy to be emitted on this

         edge.  */

      if (!phi_ssa_name_p (Ti)

          || (TREE_CODE (Ti) == SSA_NAME

              && var_to_partition (g->map, Ti) == NO_PARTITION))

        {

          /* Save constant copies until all other copies have been emitted

             on this edge.  */

          VEC_safe_push (int, heap, g->const_dests, p0);

          VEC_safe_push (tree, heap, g->const_copies, Ti);

          VEC_safe_push (source_location, heap, g->copy_locus, locus);

        }

      else

        {

          pi = var_to_partition (g->map, Ti);

          if (p0 != pi)

            {

              eliminate_name (g, p0);

              eliminate_name (g, pi);

              elim_graph_add_edge (g, p0, pi, locus);

            }

        }

    }

}

/* Push successors of T onto the elimination stack for G.  */

static void

elim_forward (elim_graph g, int T)

{

  int S;

  source_location locus;

  SET_BIT (g->visited, T);

  FOR_EACH_ELIM_GRAPH_SUCC (g, T, S, locus,

    {

      if (!TEST_BIT (g->visited, S))

        elim_forward (g, S);

    });

  VEC_safe_push (int, heap, g->stack, T);

}

/* Return 1 if there unvisited predecessors of T in graph G.  */

static int

elim_unvisited_predecessor (elim_graph g, int T)

{

  int P;

  source_location locus;

  FOR_EACH_ELIM_GRAPH_PRED (g, T, P, locus,

    {

      if (!TEST_BIT (g->visited, P))

        return 1;

    });

  return 0;

}

/* Process predecessors first, and insert a copy.  */

static void

elim_backward (elim_graph g, int T)

{

  int P;

  source_location locus;

  SET_BIT (g->visited, T);

  FOR_EACH_ELIM_GRAPH_PRED (g, T, P, locus,

    {

      if (!TEST_BIT (g->visited, P))

        {

          elim_backward (g, P);

          insert_partition_copy_on_edge (g->e, P, T, locus);

        }

    });

}

/* Allocate a new pseudo register usable for storing values sitting

   in NAME (a decl or SSA name), i.e. with matching mode and attributes.  */

static rtx

get_temp_reg (tree name)

{

  tree var = TREE_CODE (name) == SSA_NAME ? SSA_NAME_VAR (name) : name;

  tree type = TREE_TYPE (var);

  int unsignedp;

  enum machine_mode reg_mode = promote_decl_mode (var, &unsignedp);

  rtx x = gen_reg_rtx (reg_mode);

  if (POINTER_TYPE_P (type))

    mark_reg_pointer (x, TYPE_ALIGN (TREE_TYPE (TREE_TYPE (var))));

  return x;

}

/* Insert required copies for T in graph G.  Check for a strongly connected

   region, and create a temporary to break the cycle if one is found.  */

static void

elim_create (elim_graph g, int T)

{

  int P, S;

  source_location locus;

  if (elim_unvisited_predecessor (g, T))

    {

      tree var = partition_to_var (g->map, T);

      rtx U = get_temp_reg (var);

      int unsignedsrcp = TYPE_UNSIGNED (TREE_TYPE (var));

      insert_part_to_rtx_on_edge (g->e, U, T, UNKNOWN_LOCATION);

      FOR_EACH_ELIM_GRAPH_PRED (g, T, P, locus,

        {

          if (!TEST_BIT (g->visited, P))

            {

              elim_backward (g, P);

              insert_rtx_to_part_on_edge (g->e, P, U, unsignedsrcp, locus);

            }

        });

    }

  else

    {

      S = elim_graph_remove_succ_edge (g, T, &locus);

      if (S != -1)

        {

          SET_BIT (g->visited, T);

          insert_partition_copy_on_edge (g->e, T, S, locus);

        }

    }

}

/* Eliminate all the phi nodes on edge E in graph G.  */

static void

eliminate_phi (edge e, elim_graph g)

{

  int x;

  gcc_assert (VEC_length (tree, g->const_copies) == 0);

  gcc_assert (VEC_length (source_location, g->copy_locus) == 0);

  /* Abnormal edges already have everything coalesced.  */

  if (e->flags & EDGE_ABNORMAL)

    return;

  g->e = e;

  eliminate_build (g);

  if (elim_graph_size (g) != 0)

    {

      int part;

      sbitmap_zero (g->visited);

      VEC_truncate (int, g->stack, 0);

      for (x = 0; VEC_iterate (int, g->nodes, x, part); x++)

        {

          if (!TEST_BIT (g->visited, part))

            elim_forward (g, part);

        }

      sbitmap_zero (g->visited);

      while (VEC_length (int, g->stack) > 0)

        {

          x = VEC_pop (int, g->stack);

          if (!TEST_BIT (g->visited, x))