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/* SparseSet implementation.

   Copyright (C) 2007, 2008 Free Software Foundation, Inc.

   Contributed by Peter Bergner <bergner@vnet.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/>.  */

#include "config.h"

#include "system.h"

#include "sparseset.h"

/* Allocate and clear a n_elms SparseSet.  */

sparseset

sparseset_alloc (SPARSESET_ELT_TYPE n_elms)

{

  unsigned int n_bytes = sizeof (struct sparseset_def)

                         + ((n_elms - 1) * 2 * sizeof (SPARSESET_ELT_TYPE));

  /* We use xcalloc rather than xmalloc to silence some valgrind uninitialized

     read errors when accessing set->sparse[n] when "n" is not, and never has

     been, in the set.  These uninitialized reads are expected, by design and

     harmless.  If this turns into a performance problem due to some future

     additional users of sparseset, we can revisit this decision.  */

  sparseset set = (sparseset) xcalloc (1, n_bytes);

  set->dense = &(set->elms[0]);

  set->sparse = &(set->elms[n_elms]);

  set->size = n_elms;

  sparseset_clear (set);

  return set;

}

/* Low level routine not meant for use outside of sparseset.[ch].

   Assumes idx1 < s->members and idx2 < s->members.  */

static inline void

sparseset_swap (sparseset s, SPARSESET_ELT_TYPE idx1, SPARSESET_ELT_TYPE idx2)

{

  SPARSESET_ELT_TYPE tmp = s->dense[idx2];

  sparseset_insert_bit (s, s->dense[idx1], idx2);

  sparseset_insert_bit (s, tmp, idx1);

}

/* Operation: S = S - {e}

   Delete e from the set S if it is a member of S.  */

void

sparseset_clear_bit (sparseset s, SPARSESET_ELT_TYPE e)

{

  if (sparseset_bit_p (s, e))

    {

      SPARSESET_ELT_TYPE idx = s->sparse[e];

      SPARSESET_ELT_TYPE iter = s->iter;

      SPARSESET_ELT_TYPE mem = s->members - 1;

      /* If we are iterating over this set and we want to delete a

         member we've already visited, then we swap the element we

         want to delete with the element at the current iteration

         index so that it plays well together with the code below

         that actually removes the element.  */

      if (s->iterating && idx <= iter)

        {

          if (idx < iter)

            {

              sparseset_swap (s, idx, iter);

              idx = iter;

            }

          s->iter_inc = 0;

        }

      /* Replace the element we want to delete with the last element

         in the dense array and then decrement s->members, effectively

         removing the element we want to delete.  */

      sparseset_insert_bit (s, s->dense[mem], idx);

      s->members = mem;

    }

}

/* Operation: D = S

   Restrictions: none.  */

void

sparseset_copy (sparseset d, sparseset s)

{

  SPARSESET_ELT_TYPE i;

  if (d == s)

    return;

  sparseset_clear (d);

  for (i = 0; i < s->members; i++)

    sparseset_insert_bit (d, s->dense[i], i);

  d->members = s->members;

}

/* Operation: D = A & B.

   Restrictions: none.  */

void

sparseset_and (sparseset d, sparseset a, sparseset b)

{

  SPARSESET_ELT_TYPE e;

  if (a == b)

    {

      if (d != a)

        sparseset_copy (d, a);

      return;

    }

  if (d == a || d == b)

    {

      sparseset s = (d == a) ? b : a;

      EXECUTE_IF_SET_IN_SPARSESET (d, e)

        if (!sparseset_bit_p (s, e))

          sparseset_clear_bit (d, e);

    }

  else

    {

      sparseset sml, lrg;

      if (sparseset_cardinality (a) < sparseset_cardinality (b))

        {

          sml = a;

          lrg = b;

        }

      else

        {

          sml = b;

          lrg = a;

        }

      sparseset_clear (d);

      EXECUTE_IF_SET_IN_SPARSESET (sml, e)

        if (sparseset_bit_p (lrg, e))

          sparseset_set_bit (d, e);

    }

}

/* Operation: D = A & ~B.

   Restrictions: D != B, unless D == A == B.  */

void

sparseset_and_compl (sparseset d, sparseset a, sparseset b)

{

  SPARSESET_ELT_TYPE e;

  if (a == b)

    {

      sparseset_clear (d);

      return;

    }

  gcc_assert (d != b);

  if (d == a)

    {

      if (sparseset_cardinality (d) < sparseset_cardinality (b))

        {

          EXECUTE_IF_SET_IN_SPARSESET (d, e)

            if (sparseset_bit_p (b, e))

              sparseset_clear_bit (d, e);

        }

      else

        {

          EXECUTE_IF_SET_IN_SPARSESET (b, e)

            sparseset_clear_bit (d, e);

        }

    }

  else

    {

      sparseset_clear (d);

      EXECUTE_IF_SET_IN_SPARSESET (a, e)

        if (!sparseset_bit_p (b, e))

          sparseset_set_bit (d, e);

    }

}

/* Operation: D = A | B.

   Restrictions: none.  */

void

sparseset_ior (sparseset d, sparseset a, sparseset b)

{

  SPARSESET_ELT_TYPE e;

  if (a == b)

    sparseset_copy (d, a);

  else if (d == b)

    {

      EXECUTE_IF_SET_IN_SPARSESET (a, e)

        sparseset_set_bit (d, e);

    }

  else

    {

      if (d != a)

        sparseset_copy (d, a);

      EXECUTE_IF_SET_IN_SPARSESET (b, e)

        sparseset_set_bit (d, e);

    }

}

/* Operation: A == B

   Restrictions: none.  */

bool

sparseset_equal_p (sparseset a, sparseset b)

{

  SPARSESET_ELT_TYPE e;

  if (a == b)

    return true;

  if (sparseset_cardinality (a) != sparseset_cardinality (b))

    return false;

  EXECUTE_IF_SET_IN_SPARSESET (a, e)

    if (!sparseset_bit_p (b, e))

      return false;

  return true;

}