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/* Register conflict graph computation routines.

   Copyright (C) 2000, 2003, 2004, 2005, 2007 Free Software Foundation, Inc.

   Contributed by CodeSourcery, LLC

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/>.  */

/* References:

   Building an Optimizing Compiler

   Robert Morgan

   Butterworth-Heinemann, 1998 */

#include "config.h"

#include "system.h"

#include "coretypes.h"

#include "tm.h"

#include "obstack.h"

#include "hashtab.h"

#include "rtl.h"

#include "hard-reg-set.h"

#include "basic-block.h"

/* A register conflict graph is an undirected graph containing nodes

   for some or all of the regs used in a function.  Arcs represent

   conflicts, i.e. two nodes are connected by an arc if there is a

   point in the function at which the regs corresponding to the two

   nodes are both live.

   The conflict graph is represented by the data structures described

   in Morgan section 11.3.1.  Nodes are not stored explicitly; only

   arcs are.  An arc stores the numbers of the regs it connects.

   Arcs can be located by two methods:

     - The two reg numbers for each arc are hashed into a single

       value, and the arc is placed in a hash table according to this

       value.  This permits quick determination of whether a specific

       conflict is present in the graph.

     - Additionally, the arc data structures are threaded by a set of

       linked lists by single reg number.  Since each arc references

       two regs, there are two next pointers, one for the

       smaller-numbered reg and one for the larger-numbered reg.  This

       permits the quick enumeration of conflicts for a single

       register.

   Arcs are allocated from an obstack.  */

/* An arc in a conflict graph.  */

struct conflict_graph_arc_def

{

  /* The next element of the list of conflicts involving the

     smaller-numbered reg, as an index in the table of arcs of this

     graph.   Contains NULL if this is the tail.  */

  struct conflict_graph_arc_def *smaller_next;

  /* The next element of the list of conflicts involving the

     larger-numbered reg, as an index in the table of arcs of this

     graph.  Contains NULL if this is the tail.  */

  struct conflict_graph_arc_def *larger_next;

  /* The smaller-numbered reg involved in this conflict.  */

  int smaller;

  /* The larger-numbered reg involved in this conflict.  */

  int larger;

};

typedef struct conflict_graph_arc_def *conflict_graph_arc;

typedef const struct conflict_graph_arc_def *const_conflict_graph_arc;

/* A conflict graph.  */

struct conflict_graph_def

{

  /* A hash table of arcs.  Used to search for a specific conflict.  */

  htab_t arc_hash_table;

  /* The number of regs this conflict graph handles.  */

  int num_regs;

  /* For each reg, the arc at the head of a list that threads through

     all the arcs involving that reg.  An entry is NULL if no

     conflicts exist involving that reg.  */

  conflict_graph_arc *neighbor_heads;

  /* Arcs are allocated from here.  */

  struct obstack arc_obstack;

};

/* The initial capacity (number of conflict arcs) for newly-created

   conflict graphs.  */

#define INITIAL_ARC_CAPACITY 64

/* Computes the hash value of the conflict graph arc connecting regs

   R1 and R2.  R1 is assumed to be smaller or equal to R2.  */

#define CONFLICT_HASH_FN(R1, R2) ((R2) * ((R2) - 1) / 2 + (R1))

static hashval_t arc_hash (const void *);

static int arc_eq (const void *, const void *);

static int print_conflict (int, int, void *);

/* Callback function to compute the hash value of an arc.  Uses

   current_graph to locate the graph to which the arc belongs.  */

static hashval_t

arc_hash (const void *arcp)

{

  const_conflict_graph_arc arc = (const_conflict_graph_arc) arcp;

  return CONFLICT_HASH_FN (arc->smaller, arc->larger);

}

/* Callback function to determine the equality of two arcs in the hash

   table.  */

static int

arc_eq (const void *arcp1, const void *arcp2)

{

  const_conflict_graph_arc arc1 = (const_conflict_graph_arc) arcp1;

  const_conflict_graph_arc arc2 = (const_conflict_graph_arc) arcp2;

  return arc1->smaller == arc2->smaller && arc1->larger == arc2->larger;

}

/* Creates an empty conflict graph to hold conflicts among NUM_REGS

   registers.  */

conflict_graph

conflict_graph_new (int num_regs)

{

  conflict_graph graph = XNEW (struct conflict_graph_def);

  graph->num_regs = num_regs;

  /* Set up the hash table.  No delete action is specified; memory

     management of arcs is through the obstack.  */

  graph->arc_hash_table

    = htab_create (INITIAL_ARC_CAPACITY, &arc_hash, &arc_eq, NULL);

  /* Create an obstack for allocating arcs.  */

  obstack_init (&graph->arc_obstack);

  /* Create and zero the lookup table by register number.  */

  graph->neighbor_heads = XCNEWVEC (conflict_graph_arc, num_regs);

  return graph;

}

/* Deletes a conflict graph.  */

void

conflict_graph_delete (conflict_graph graph)

{

  obstack_free (&graph->arc_obstack, NULL);

  htab_delete (graph->arc_hash_table);

  free (graph->neighbor_heads);

  free (graph);

}

/* Adds a conflict to GRAPH between regs REG1 and REG2, which must be

   distinct.  Returns nonzero, unless the conflict is already present

   in GRAPH, in which case it does nothing and returns zero.  */

int

conflict_graph_add (conflict_graph graph, int reg1, int reg2)

{

  int smaller = MIN (reg1, reg2);

  int larger = MAX (reg1, reg2);

  struct conflict_graph_arc_def dummy;

  conflict_graph_arc arc;

  void **slot;

  /* A reg cannot conflict with itself.  */

  gcc_assert (reg1 != reg2);

  dummy.smaller = smaller;

  dummy.larger = larger;

  slot = htab_find_slot (graph->arc_hash_table, (void *) &dummy, INSERT);

  /* If the conflict is already there, do nothing.  */

  if (*slot != NULL)

    return 0;

  /* Allocate an arc.  */

  arc

    = obstack_alloc (&graph->arc_obstack,

                     sizeof (struct conflict_graph_arc_def));

  /* Record the reg numbers.  */

  arc->smaller = smaller;

  arc->larger = larger;

  /* Link the conflict into two lists, one for each reg.  */

  arc->smaller_next = graph->neighbor_heads[smaller];

  graph->neighbor_heads[smaller] = arc;

  arc->larger_next = graph->neighbor_heads[larger];

  graph->neighbor_heads[larger] = arc;

  /* Put it in the hash table.  */

  *slot = (void *) arc;

  return 1;

}

/* Returns nonzero if a conflict exists in GRAPH between regs REG1

   and REG2.  */

int

conflict_graph_conflict_p (conflict_graph graph, int reg1, int reg2)

{

  /* Build an arc to search for.  */

  struct conflict_graph_arc_def arc;

  arc.smaller = MIN (reg1, reg2);

  arc.larger = MAX (reg1, reg2);

  return htab_find (graph->arc_hash_table, (void *) &arc) != NULL;

}

/* Calls ENUM_FN for each conflict in GRAPH involving REG.  EXTRA is

   passed back to ENUM_FN.  */

void

conflict_graph_enum (conflict_graph graph, int reg,

                     conflict_graph_enum_fn enum_fn, void *extra)

{

  conflict_graph_arc arc = graph->neighbor_heads[reg];

  while (arc != NULL)

    {

      /* Invoke the callback.  */

      if ((*enum_fn) (arc->smaller, arc->larger, extra))

        /* Stop if requested.  */

        break;

      /* Which next pointer to follow depends on whether REG is the

         smaller or larger reg in this conflict.  */

      if (reg < arc->larger)

        arc = arc->smaller_next;

      else

        arc = arc->larger_next;

    }

}

/* For each conflict between a register x and SRC in GRAPH, adds a

   conflict to GRAPH between x and TARGET.  */

void

conflict_graph_merge_regs (conflict_graph graph, int target, int src)

{

  conflict_graph_arc arc = graph->neighbor_heads[src];

  if (target == src)

    return;

  while (arc != NULL)

    {

      int other = arc->smaller;

      if (other == src)

        other = arc->larger;

      conflict_graph_add (graph, target, other);

      /* Which next pointer to follow depends on whether REG is the

         smaller or larger reg in this conflict.  */

      if (src < arc->larger)

        arc = arc->smaller_next;

      else

        arc = arc->larger_next;

    }

}

/* Holds context information while a conflict graph is being traversed

   for printing.  */

struct print_context

{

  /* The file pointer to which we're printing.  */

  FILE *fp;

  /* The reg whose conflicts we're printing.  */

  int reg;

  /* Whether a conflict has already been printed for this reg.  */

  int started;

};

/* Callback function when enumerating conflicts during printing.  */

static int

print_conflict (int reg1, int reg2, void *contextp)

{

  struct print_context *context = (struct print_context *) contextp;

  int reg;

  /* If this is the first conflict printed for this reg, start a new

     line.  */

  if (! context->started)

    {

      fprintf (context->fp, " %d:", context->reg);

      context->started = 1;

    }

  /* Figure out the reg whose conflicts we're printing.  The other reg

     is the interesting one.  */

  if (reg1 == context->reg)

    reg = reg2;

  else

    {

      gcc_assert (reg2 == context->reg);

      reg = reg1;

    }

  /* Print the conflict.  */

  fprintf (context->fp, " %d", reg);

  /* Continue enumerating.  */

  return 0;

}

/* Prints the conflicts in GRAPH to FP.  */

void

conflict_graph_print (conflict_graph graph, FILE *fp)

{

  int reg;

  struct print_context context;

  context.fp = fp;

  fprintf (fp, "Conflicts:\n");

  /* Loop over registers supported in this graph.  */

  for (reg = 0; reg < graph->num_regs; ++reg)

    {

      context.reg = reg;

      context.started = 0;

      /* Scan the conflicts for reg, printing as we go.  A label for

         this line will be printed the first time a conflict is

         printed for the reg; we won't start a new line if this reg

         has no conflicts.  */

      conflict_graph_enum (graph, reg, &print_conflict, &context);

      /* If this reg does have conflicts, end the line.  */

      if (context.started)

        fputc ('\n', fp);

    }

}