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authorBen Cheng <bccheng@google.com>2013-03-28 11:14:20 -0700
committerBen Cheng <bccheng@google.com>2013-03-28 12:40:33 -0700
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[GCC 4.8] Initial check-in of GCC 4.8.0
Change-Id: I0719d8a6d0f69b367a6ab6f10eb75622dbf12771
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+/* SparseSet implementation.
+ Copyright (C) 2007-2013 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/>. */
+
+#ifndef GCC_SPARSESET_H
+#define GCC_SPARSESET_H
+
+/* Implementation of the Briggs and Torczon sparse set representation.
+ The sparse set representation was first published in:
+
+ "An Efficient Representation for Sparse Sets",
+ ACM LOPLAS, Vol. 2, Nos. 1-4, March-December 1993, Pages 59-69.
+
+ The sparse set representation is suitable for integer sets with a
+ fixed-size universe. Two vectors are used to store the members of
+ the set. If an element I is in the set, then sparse[I] is the
+ index of I in the dense vector, and dense[sparse[I]] == I. The dense
+ vector works like a stack. The size of the stack is the cardinality
+ of the set.
+
+ The following operations can be performed in O(1) time:
+
+ * clear : sparseset_clear
+ * cardinality : sparseset_cardinality
+ * set_size : sparseset_size
+ * member_p : sparseset_bit_p
+ * add_member : sparseset_set_bit
+ * remove_member : sparseset_clear_bit
+ * choose_one : sparseset_pop
+
+ Additionally, the sparse set representation supports enumeration of
+ the members in O(N) time, where n is the number of members in the set.
+ The members of the set are stored cache-friendly in the dense vector.
+ This makes it a competitive choice for iterating over relatively sparse
+ sets requiring operations:
+
+ * forall : EXECUTE_IF_SET_IN_SPARSESET
+ * set_copy : sparseset_copy
+ * set_intersection : sparseset_and
+ * set_union : sparseset_ior
+ * set_difference : sparseset_and_compl
+ * set_disjuction : (not implemented)
+ * set_compare : sparseset_equal_p
+
+ NB: It is OK to use remove_member during EXECUTE_IF_SET_IN_SPARSESET.
+ The iterator is updated for it.
+
+ Based on the efficiency of these operations, this representation of
+ sparse sets will often be superior to alternatives such as simple
+ bitmaps, linked-list bitmaps, array bitmaps, balanced binary trees,
+ hash tables, linked lists, etc., if the set is sufficiently sparse.
+ In the LOPLAS paper the cut-off point where sparse sets became faster
+ than simple bitmaps (see sbitmap.h) when N / U < 64 (where U is the
+ size of the universe of the set).
+
+ Because the set universe is fixed, the set cannot be resized. For
+ sparse sets with initially unknown size, linked-list bitmaps are a
+ better choice, see bitmap.h.
+
+ Sparse sets storage requirements are relatively large: O(U) with a
+ larger constant than sbitmaps (if the storage requirement for an
+ sbitmap with universe U is S, then the storage required for a sparse
+ set for the same universe are 2*HOST_BITS_PER_WIDEST_FAST_INT * S).
+ Accessing the sparse vector is not very cache-friendly, but iterating
+ over the members in the set is cache-friendly because only the dense
+ vector is used. */
+
+/* Data Structure used for the SparseSet representation. */
+
+#define SPARSESET_ELT_BITS ((unsigned) HOST_BITS_PER_WIDEST_FAST_INT)
+#define SPARSESET_ELT_TYPE unsigned HOST_WIDEST_FAST_INT
+
+typedef struct sparseset_def
+{
+ SPARSESET_ELT_TYPE *dense; /* Dense array. */
+ SPARSESET_ELT_TYPE *sparse; /* Sparse array. */
+ SPARSESET_ELT_TYPE members; /* Number of elements. */
+ SPARSESET_ELT_TYPE size; /* Maximum number of elements. */
+ SPARSESET_ELT_TYPE iter; /* Iterator index. */
+ unsigned char iter_inc; /* Iteration increment amount. */
+ bool iterating;
+ SPARSESET_ELT_TYPE elms[2]; /* Combined dense and sparse arrays. */
+} *sparseset;
+
+#define sparseset_free(MAP) free(MAP)
+extern sparseset sparseset_alloc (SPARSESET_ELT_TYPE n_elms);
+extern void sparseset_clear_bit (sparseset, SPARSESET_ELT_TYPE);
+extern void sparseset_copy (sparseset, sparseset);
+extern void sparseset_and (sparseset, sparseset, sparseset);
+extern void sparseset_and_compl (sparseset, sparseset, sparseset);
+extern void sparseset_ior (sparseset, sparseset, sparseset);
+extern bool sparseset_equal_p (sparseset, sparseset);
+
+/* Operation: S = {}
+ Clear the set of all elements. */
+
+static inline void
+sparseset_clear (sparseset s)
+{
+ s->members = 0;
+ s->iterating = false;
+}
+
+/* Return the number of elements currently in the set. */
+
+static inline SPARSESET_ELT_TYPE
+sparseset_cardinality (sparseset s)
+{
+ return s->members;
+}
+
+/* Return the maximum number of elements this set can hold. */
+
+static inline SPARSESET_ELT_TYPE
+sparseset_size (sparseset s)
+{
+ return s->size;
+}
+
+/* Return true if e is a member of the set S, otherwise return false. */
+
+static inline bool
+sparseset_bit_p (sparseset s, SPARSESET_ELT_TYPE e)
+{
+ SPARSESET_ELT_TYPE idx;
+
+ gcc_checking_assert (e < s->size);
+
+ idx = s->sparse[e];
+
+ return idx < s->members && s->dense[idx] == e;
+}
+
+/* Low level insertion routine not meant for use outside of sparseset.[ch].
+ Assumes E is valid and not already a member of the set S. */
+
+static inline void
+sparseset_insert_bit (sparseset s, SPARSESET_ELT_TYPE e, SPARSESET_ELT_TYPE idx)
+{
+ s->sparse[e] = idx;
+ s->dense[idx] = e;
+}
+
+/* Operation: S = S + {e}
+ Insert E into the set S, if it isn't already a member. */
+
+static inline void
+sparseset_set_bit (sparseset s, SPARSESET_ELT_TYPE e)
+{
+ if (!sparseset_bit_p (s, e))
+ sparseset_insert_bit (s, e, s->members++);
+}
+
+/* Return and remove the last member added to the set S. */
+
+static inline SPARSESET_ELT_TYPE
+sparseset_pop (sparseset s)
+{
+ SPARSESET_ELT_TYPE mem = s->members;
+
+ gcc_checking_assert (mem != 0);
+
+ s->members = mem - 1;
+ return s->dense[mem];
+}
+
+static inline void
+sparseset_iter_init (sparseset s)
+{
+ s->iter = 0;
+ s->iter_inc = 1;
+ s->iterating = true;
+}
+
+static inline bool
+sparseset_iter_p (sparseset s)
+{
+ if (s->iterating && s->iter < s->members)
+ return true;
+ else
+ return s->iterating = false;
+}
+
+static inline SPARSESET_ELT_TYPE
+sparseset_iter_elm (sparseset s)
+{
+ return s->dense[s->iter];
+}
+
+static inline void
+sparseset_iter_next (sparseset s)
+{
+ s->iter += s->iter_inc;
+ s->iter_inc = 1;
+}
+
+#define EXECUTE_IF_SET_IN_SPARSESET(SPARSESET, ITER) \
+ for (sparseset_iter_init (SPARSESET); \
+ sparseset_iter_p (SPARSESET) \
+ && (((ITER) = sparseset_iter_elm (SPARSESET)) || 1); \
+ sparseset_iter_next (SPARSESET))
+
+#endif /* GCC_SPARSESET_H */