[libfirm] / ir / ir / iredges.c

/*
 * Copyright (C) 1995-2008 University of Karlsruhe.  All right reserved.
 *
 * This file is part of libFirm.
 *
 * This file may be distributed and/or modified under the terms of the
 * GNU General Public License version 2 as published by the Free Software
 * Foundation and appearing in the file LICENSE.GPL included in the
 * packaging of this file.
 *
 * Licensees holding valid libFirm Professional Edition licenses may use
 * this file in accordance with the libFirm Commercial License.
 * Agreement provided with the Software.
 *
 * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
 * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE.
 */

/**
 * @file
 * @brief   Always available outs.
 * @author  Sebastian Hack, Michael Beck, Andreas Schoesser
 * @date    14.1.2005
 * @version $Id$
 * @summary
 *   This are out-edges (also called def-use edges) that are dynamically
 *   updated as the graph changes.
 */
#include "config.h"

#include "irnode_t.h"
#include "iropt_t.h"
#include "iredgekinds.h"
#include "iredges_t.h"
#include "irgwalk.h"
#include "irdump_t.h"
#include "irprintf.h"
#include "debug.h"
#include "set.h"
#include "bitset.h"

#include "iredgeset.h"
#include "hashptr.h"

#define DO_REHASH
#define SCALAR_RETURN
#define HashSet                   ir_edgeset_t
#define HashSetIterator           ir_edgeset_iterator_t
#define ValueType                 ir_edge_t*
#define NullValue                 NULL
#define DeletedValue              ((ir_edge_t*)-1)
#define Hash(this,key)            (HASH_PTR(key->src) ^ (key->pos * 40013))
#define KeysEqual(this,key1,key2) ((key1->src) == (key2->src) && (key1->pos == key2->pos))
#define SetRangeEmpty(ptr,size)   memset(ptr, 0, (size) * sizeof((ptr)[0]))

#define hashset_init            ir_edgeset_init
#define hashset_init_size       ir_edgeset_init_size
#define hashset_destroy         ir_edgeset_destroy
#define hashset_insert          ir_edgeset_insert
#define hashset_remove          ir_edgeset_remove
#define hashset_find            ir_edgeset_find
#define hashset_size            ir_edgeset_size
#define hashset_iterator_init   ir_edgeset_iterator_init
#define hashset_iterator_next   ir_edgeset_iterator_next
#define hashset_remove_iterator ir_edgeset_remove_iterator

#include "hashset.c"

/**
 * A function that allows for setting an edge.
 * This abstraction is necessary since different edge kind have
 * different methods of setting edges.
 */
typedef void (set_edge_func_t)(ir_node *src, int pos, ir_node *tgt);

typedef int (get_edge_src_arity_func_t)(const ir_node *src);

typedef ir_node *(get_edge_src_n_func_t)(const ir_node *src, int pos);

/**
 * Additional data for an edge kind.
 */
typedef struct {
        const char                *name;       /**< name of this edge kind */
        set_edge_func_t           *set_edge;   /**< the set_edge function */
        int                       first_idx;   /**< index of the first possible edge */
        get_edge_src_arity_func_t *get_arity;  /**< the get_arity function */
        get_edge_src_n_func_t     *get_n;      /**< the get_n function */
} ir_edge_kind_info_t;

/**
 * Get the predecessor block.
 */
static ir_node *get_block_n(const ir_node *irn, int pos) {
        if (is_Block(irn))
                return get_Block_cfgpred_block(irn, pos);
        /* might be a Bad */
        return NULL;
}

static const ir_edge_kind_info_t edge_kind_info[EDGE_KIND_LAST] = {
        { "normal"     , set_irn_n,   -1, get_irn_arity,  get_irn_n   },
        { "block succs", NULL,         0, get_irn_arity,  get_block_n },
        { "dependency",  set_irn_dep,  0, get_irn_deps,   get_irn_dep }
};

#define foreach_tgt(irn, i, n, kind) for(i = edge_kind_info[kind].first_idx, n = edge_kind_info[kind].get_arity(irn); i < n; ++i)
#define get_n(irn, pos, kind)        (edge_kind_info[kind].get_n(irn, pos))
#define get_kind_str(kind)           (edge_kind_info[kind].name)

DEBUG_ONLY(static firm_dbg_module_t *dbg;)

/**
 * This flag is set to 1, if the edges get initialized for an irg.
 * Then register additional data is forbidden.
 */
static int edges_used = 0;

/**
 * Summed size of all users private data
 */

static int edges_private_size = 0;
#define EDGE_SIZE (sizeof(ir_edge_t) + edges_private_size)

/**
 * If set to 1, the list heads are checked every time an edge is changed.
 */
static int edges_dbg = 0;

#ifdef DEBUG_libfirm
/* a static variable holding the last number assigned to a new edge */
static long last_edge_num = -1;
#endif

static inline long edge_get_id(const ir_edge_t *e) {
#ifdef DEBUG_libfirm
        return e->edge_nr;
#else /* DEBUG_libfirm */
        return (long)e;
#endif /* DEBUG_libfirm */
}

/**
 * Announce to reserve extra space for each edge to be allocated.
 *
 * @param n: Size of the space to reserve
 *
 * @return Offset at which the private data will begin
 *
 * Several users can reserve extra space for private usage.
 * Each user has to remember his given offset and the size of his private data.
 * To be called before FIRM is initialized.
 */
int edges_register_private_data(size_t n) {
        int res = edges_private_size;

        assert(!edges_used && "you cannot register private edge data, if edges have been initialized");

        edges_private_size += n;
        return res;
}

/**
 * Reset the user's private data at offset 'offset'
 * The user has to remember his offset and the size of his data!
 * Caution: Using wrong values here can destroy other users private data!
 */
void edges_reset_private_data(ir_graph *irg, int offset, size_t size) {
        irg_edge_info_t       *info = _get_irg_edge_info(irg, EDGE_KIND_NORMAL);
        ir_edge_t             *edge;
        ir_edgeset_iterator_t  iter;

        foreach_ir_edgeset(&info->edges, edge, iter) {
                memset(edge + sizeof(*edge) + offset, 0, size);
        }
}

#define TIMES37(x) (((x) << 5) + ((x) << 2) + (x))

#define get_irn_out_list_head(irn) (&get_irn_out_info(irn)->outs)

#define edge_hash(edge) (TIMES37((edge)->pos) + HASH_PTR((edge)->src))

/**
 * Initialize the out information for a graph.
 * @note Dead node elimination can call this on an already initialized graph.
 */
void edges_init_graph_kind(ir_graph *irg, ir_edge_kind_t kind) {
        if (edges_activated_kind(irg, kind)) {
                irg_edge_info_t *info = _get_irg_edge_info(irg, kind);
                size_t amount = irg->estimated_node_count * 2;

                edges_used = 1;
                if(info->allocated) {
                        amount = ir_edgeset_size(&info->edges);
                        ir_edgeset_destroy(&info->edges);
                        obstack_free(&info->edges_obst, NULL);
                }
                obstack_init(&info->edges_obst);
                ir_edgeset_init_size(&info->edges, amount);
                info->allocated = 1;
        }
}

/**
 * Get the edge object of an outgoing edge at a node.
 * @param   irg The graph, the node is in.
 * @param   src The node at which the edge originates.
 * @param   pos The position of the edge.
 * @return      The corresponding edge object or NULL,
 *              if no such edge exists.
 */
const ir_edge_t *get_irn_edge_kind(ir_graph *irg, const ir_node *src, int pos, ir_edge_kind_t kind)
{
        if (edges_activated_kind(irg, kind)) {
                irg_edge_info_t *info = _get_irg_edge_info(irg, kind);
                ir_edge_t       key;

                key.src = (ir_node *)src;
                key.pos = pos;

                return ir_edgeset_find(&info->edges, &key);
        }

        return NULL;
}

/**
 * Get the edge object of an outgoing edge at a node.
 * Looks for an edge for all kinds.
 */
const ir_edge_t *get_irn_edge(ir_graph *irg, const ir_node *src, int pos) {
        const ir_edge_t *edge;
        if((edge = get_irn_edge_kind(irg, src, pos, EDGE_KIND_NORMAL)) == NULL)
                edge = get_irn_edge_kind(irg, src, pos, EDGE_KIND_BLOCK);
        return(edge);
}

/**
 * Change the out count
 *
 * @param tgt  the edge target
 * @param kind the kind of the edge
 */
static inline void edge_change_cnt(ir_node *tgt, ir_edge_kind_t kind, int ofs) {
        irn_edge_info_t *info = _get_irn_edge_info(tgt, kind);
        info->out_count += ofs;

#if 0
        assert(info->out_count >= 0);
        if (info->out_count == 0 && kind == EDGE_KIND_NORMAL) {
                /* tgt lost it's last user */
                int i;

                for (i = get_irn_arity(tgt) - 1; i >= -1; --i) {
                        ir_node *prev = get_irn_n(tgt, i);

                        edges_notify_edge(tgt, i, NULL, prev, current_ir_graph);
                }
                for (i = get_irn_deps(tgt) - 1; i >= 0; --i) {
                        ir_node *prev = get_irn_dep(tgt, i);

                        edges_notify_edge_kind(tgt, i, NULL, prev, EDGE_KIND_DEP, current_ir_graph);

                }
        }
#endif
}

/**
 * Verify the edge list of a node, ie. ensure it's a loop:
 * head -> e_1 -> ... -> e_n -> head
 */
static inline void vrfy_list_head(ir_node *irn, ir_edge_kind_t kind) {
        int                    err       = 0;
        int                    num       = 0;
        pset                   *lh_set   = pset_new_ptr(16);
        const struct list_head *head     = _get_irn_outs_head(irn, kind);
        const struct list_head *pos;

        list_for_each(pos, head) {
                if (pset_find_ptr(lh_set, pos)) {
                        const ir_edge_t *edge = list_entry(pos, ir_edge_t, list);

                        ir_fprintf(stderr, "EDGE Verifier: edge list broken (self loop not to head) for %+F:\n", irn);
                        fprintf(stderr, "- at list entry %d\n", num);
                        if (edge->invalid)
                                fprintf(stderr, "- edge(%ld) is invalid\n", edge_get_id(edge));
                        if (edge->src)
                                ir_fprintf(stderr, "- edge(%ld) %+F(%d)\n", edge_get_id(edge), edge->src, edge->pos);
                        err = 1;
                        break;
                }
                num++;
                pset_insert_ptr(lh_set, pos);
        }

        del_pset(lh_set);

        assert(err == 0);
}

/* The edge from (src, pos) -> old_tgt is redirected to tgt */
void edges_notify_edge_kind(ir_node *src, int pos, ir_node *tgt,
                            ir_node *old_tgt, ir_edge_kind_t kind,
                            ir_graph *irg)
{
        const char      *msg = "";
        irg_edge_info_t *info;
        ir_edgeset_t    *edges;
        ir_edge_t        templ;
        ir_edge_t       *edge;

        assert(edges_activated_kind(irg, kind));

        /*
         * Only do something, if the old and new target differ.
         */
        if (tgt == old_tgt)
                return;

        info  = _get_irg_edge_info(irg, kind);
        edges = &info->edges;

        /* Initialize the edge template to search in the set. */
        templ.src = src;
        templ.pos = pos;

        /*
         * If the target is NULL, the edge shall be deleted.
         */
        if (tgt == NULL) {
                /* search the edge in the set. */
                edge = ir_edgeset_find(edges, &templ);

                /* mark the edge invalid if it was found */
                if (edge) {
                        msg = "deleting";
                        list_del(&edge->list);
                        ir_edgeset_remove(edges, edge);
                        edge->invalid = 1;
                        edge->pos = -2;
                        edge->src = NULL;
#ifdef DEBUG_libfirm
                        edge->edge_nr = -1;
#endif /* DEBUG_libfirm */
                        edge_change_cnt(old_tgt, kind, -1);
                }

                /* If the edge was not found issue a warning on the debug stream */
                else {
                        msg = "edge to delete not found!\n";
                }
        } /* if */

        /*
         * The target is not NULL and the old target differs
         * from the new target, the edge shall be moved (if the
         * old target was != NULL) or added (if the old target was
         * NULL).
         */
        else {
                struct list_head *head = _get_irn_outs_head(tgt, kind);

                assert(head->next && head->prev &&
                                "target list head must have been initialized");

                /* If the old target is not null, the edge is moved. */
                if (old_tgt) {
                        edge = ir_edgeset_find(edges, &templ);
                        assert(edge && "edge to redirect not found!");
                        assert(! edge->invalid && "Invalid edge encountered");

                        msg = "redirecting";

                        list_move(&edge->list, head);
                        edge_change_cnt(old_tgt, kind, -1);
                }

                /* The old target was null, thus, the edge is newly created. */
                else {
                        ir_edge_t *new_edge;
                        ir_edge_t *edge
                                = obstack_alloc(&info->edges_obst, EDGE_SIZE);
                        memset(edge, 0, EDGE_SIZE);
                        edge->src = src;
                        edge->pos = pos;
                        edge->kind = kind;
                        DEBUG_ONLY(edge->src_nr = get_irn_node_nr(src));

                        new_edge = ir_edgeset_insert(edges, edge);
                        if(new_edge != edge) {
                                obstack_free(&info->edges_obst, edge);
                        }

                        assert(! edge->invalid && "Freshly inserted edge is invalid?!?");
                        assert(edge->list.next == NULL && edge->list.prev == NULL &&
                                "New edge must not have list head initialized");

                        msg = "adding";
                        list_add(&edge->list, head);
#ifdef DEBUG_libfirm
                        edge->edge_nr = ++last_edge_num;
#endif /* DEBUG_libfirm */
                }

                edge_change_cnt(tgt, kind, +1);
        } /* else */

#ifndef DEBUG_libfirm
        /* verify list heads */
        if (edges_dbg) {
                if (tgt)
                        vrfy_list_head(tgt, kind);
                if (old_tgt)
                        vrfy_list_head(old_tgt, kind);
        }
#endif

        DBG((dbg, LEVEL_5, "announce out edge: %+F %d-> %+F(%+F): %s\n", src, pos, tgt, old_tgt, msg));
}

void edges_notify_edge(ir_node *src, int pos, ir_node *tgt, ir_node *old_tgt, ir_graph *irg)
{
        if (edges_activated_kind(irg, EDGE_KIND_NORMAL)) {
                edges_notify_edge_kind(src, pos, tgt, old_tgt, EDGE_KIND_NORMAL, irg);
        }

        if (edges_activated_kind(irg, EDGE_KIND_BLOCK) && is_Block(src)) {
                if (pos == -1) {
                        /* a MacroBlock edge: ignore it here */
                } else {
                        ir_node *bl_old = old_tgt ? get_nodes_block(skip_Proj(old_tgt)) : NULL;
                        ir_node *bl_tgt = NULL;

                        if (tgt)
                                bl_tgt = is_Bad(tgt) ? tgt : get_nodes_block(skip_Proj(tgt));

                        edges_notify_edge_kind(src, pos, bl_tgt, bl_old, EDGE_KIND_BLOCK, irg);
                }
        }
}

/**
 * Delete all in edges of a given kind from the node old.
 *
 * @param old   the node
 * @param kind  the kind of edges to remove
 * @param irg   the irg of the old node
 */
static void edges_node_deleted_kind(ir_node *old, ir_edge_kind_t kind, ir_graph *irg)
{
        int i, n;

        if (!edges_activated_kind(irg, kind))
                return;

        DBG((dbg, LEVEL_5, "node deleted (kind: %s): %+F\n", get_kind_str(kind), old));

        foreach_tgt(old, i, n, kind) {
                ir_node *old_tgt = get_n(old, i, kind);
                edges_notify_edge_kind(old, i, NULL, old_tgt, kind, irg);
        }
}

struct build_walker {
        ir_graph       *irg;
        ir_edge_kind_t kind;
        bitset_t       *reachable;
        unsigned       problem_found;
};

/**
 * Post-Walker: notify all edges
 */
static void build_edges_walker(ir_node *irn, void *data) {
        struct build_walker   *w = data;
        int                   i, n;
        ir_edge_kind_t        kind = w->kind;
        ir_graph              *irg = w->irg;
        get_edge_src_n_func_t *get_n;

        get_n = edge_kind_info[kind].get_n;
        foreach_tgt(irn, i, n, kind) {
                ir_node *pred = get_n(irn, i, kind);
                edges_notify_edge_kind(irn, i, pred, NULL, kind, irg);
        }
}

/**
 * Pre-Walker: initializes the list-heads and set the out-count
 * of all nodes to 0.
 */
static void init_lh_walker(ir_node *irn, void *data) {
        struct build_walker *w   = data;
        ir_edge_kind_t      kind = w->kind;
        list_head           *head = _get_irn_outs_head(irn, kind);
        INIT_LIST_HEAD(head);
        _get_irn_edge_info(irn, kind)->out_count = 0;
}

/**
 * Pre-Walker: initializes the list-heads and set the out-count
 * of all nodes to 0.
 *
 * Additionally touches DEP nodes, as they might be DEAD.
 * THIS IS UGLY, but I don't find a better way until we
 *
 * a) ensure that dead nodes are not used as input
 * b) it might be sufficient to add those stupid NO_REG nodes
 * to the anchor
 */
static void init_lh_walker_dep(ir_node *irn, void *data) {
        struct build_walker *w   = data;
        ir_edge_kind_t      kind = w->kind;
        list_head           *head = _get_irn_outs_head(irn, kind);
        int                 i;

        INIT_LIST_HEAD(head);
        _get_irn_edge_info(irn, kind)->out_count = 0;

        for (i = get_irn_deps(irn) - 1; i >= 0; --i) {
                ir_node *dep = get_irn_dep(irn, i);

                head = _get_irn_outs_head(dep, kind);

                INIT_LIST_HEAD(head);
                _get_irn_edge_info(dep, kind)->out_count = 0;
        }
}

typedef struct visitor_info_t {
        irg_walk_func *visit;
        void *data;
} visitor_info_t;

/**
 * Visitor: initializes the list-heads and set the out-count
 * of all nodes to 0 of nodes that are not seen so far.
 */
static void visitor(ir_node *irn, void *data) {
        visitor_info_t *info = data;

        if (!irn_visited(irn)) {
                mark_irn_visited(irn);
                info->visit(irn, info->data);
        }
}

/*
 * Build the initial edge set.
 * Beware, this is not a simple task because it suffers from two
 * difficulties:
 * - the anchor set allows access to Nodes that may not be reachable from
 *   the End node
 * - the identities add nodes to the "root set" that are not yet reachable
 *   from End. However, after some transformations, the CSE may revival these
 *   nodes
 *
 * These problems can be fixed using different strategies:
 * - Add an age flag to every node. Whenever the edge of a node is older
 *   then the current edge, invalidate the edges of this node.
 *   While this would help for revivaled nodes, it increases memory and runtime.
 * - Delete the identities set.
 *   Solves the revival problem, but may increase the memory consumption, as
 *   nodes cannot be revivaled at all.
 * - Manually iterate over the identities root set. This did not consume more memory
 *   but increase the computation time because the |identities| >= |V|
 *
 * Currently, we use the last option.
 */
void edges_activate_kind(ir_graph *irg, ir_edge_kind_t kind)
{
        struct build_walker w;
        irg_edge_info_t     *info = _get_irg_edge_info(irg, kind);
        visitor_info_t      visit;

        w.irg  = irg;
        w.kind = kind;

        visit.data = &w;

        info->activated = 1;
        edges_init_graph_kind(irg, kind);
        if (kind == EDGE_KIND_DEP) {
                irg_walk_anchors(irg, init_lh_walker_dep, NULL, &w);
                /* Argh: Dep nodes might be dead, so we MUST visit identities first */
                visit.visit = init_lh_walker_dep;
                visit_all_identities(irg, visitor, &visit);
                irg_walk_anchors(irg, NULL, build_edges_walker, &w);
        } else {
                irg_walk_anchors(irg, init_lh_walker, build_edges_walker, &w);
                visit.visit = init_lh_walker;
                visit_all_identities(irg, visitor, &visit);
        }
}

void edges_deactivate_kind(ir_graph *irg, ir_edge_kind_t kind)
{
        irg_edge_info_t *info = _get_irg_edge_info(irg, kind);

        info->activated = 0;
        if (info->allocated) {
                obstack_free(&info->edges_obst, NULL);
                ir_edgeset_destroy(&info->edges);
                info->allocated = 0;
        }
}

int (edges_activated_kind)(const ir_graph *irg, ir_edge_kind_t kind)
{
        return _edges_activated_kind(irg, kind);
}


/**
 * Reroute all use-edges from a node to another.
 * @param from The node whose use-edges shall be withdrawn.
 * @param to   The node to which all the use-edges of @p from shall be
 *             sent to.
 * @param irg  The graph.
 */
void edges_reroute_kind(ir_node *from, ir_node *to, ir_edge_kind_t kind, ir_graph *irg)
{
        set_edge_func_t *set_edge = edge_kind_info[kind].set_edge;

        if(set_edge && edges_activated_kind(irg, kind)) {
                struct list_head *head = _get_irn_outs_head(from, kind);

                DBG((dbg, LEVEL_5, "reroute from %+F to %+F\n", from, to));

                while (head != head->next) {
                        ir_edge_t *edge = list_entry(head->next, ir_edge_t, list);
                        assert(edge->pos >= -1);
                        set_edge(edge->src, edge->pos, to);
                }
        }
}

static void verify_set_presence(ir_node *irn, void *data)
{
        struct build_walker *w     = data;
        ir_edgeset_t        *edges = &_get_irg_edge_info(w->irg, w->kind)->edges;
        int i, n;

        foreach_tgt(irn, i, n, w->kind) {
                ir_edge_t templ, *e;

                templ.src = irn;
                templ.pos = i;

                e = ir_edgeset_find(edges, &templ);
                if(e != NULL) {
                        e->present = 1;
                } else {
                        w->problem_found = 1;
#if 0
                        ir_fprintf(stderr, "Edge Verifier: edge %+F,%d -> %+F (kind: \"%s\") is missing\n",
                                irn, i, get_n(irn, i, w->kind), get_kind_str(w->kind));
#endif
                }
        }
}

static void verify_list_presence(ir_node *irn, void *data)
{
        struct build_walker *w = data;
        const ir_edge_t     *e;

        bitset_set(w->reachable, get_irn_idx(irn));

        /* check list heads */
        vrfy_list_head(irn, w->kind);

        foreach_out_edge_kind(irn, e, w->kind) {
                ir_node *tgt;

                if (w->kind == EDGE_KIND_NORMAL && get_irn_arity(e->src) <= e->pos) {
                        w->problem_found = 1;
#if 0
                        ir_fprintf(stderr, "Edge Verifier: edge(%ld) %+F -> %+F recorded at src position %d, but src has arity %d\n",
                                edge_get_id(e), e->src, irn, e->pos, get_irn_arity(e->src));
#endif
                        continue;
                }

                tgt = get_n(e->src, e->pos, w->kind);

                if (irn != tgt) {
                        w->problem_found = 1;
#if 0
                        ir_fprintf(stderr, "Edge Verifier: edge(%ld) %+F,%d (kind \"%s\") is no out edge of %+F but of %+F\n",
                                edge_get_id(e), e->src, e->pos, get_kind_str(w->kind), irn, tgt);
#endif
                }
        }
}

int edges_verify_kind(ir_graph *irg, ir_edge_kind_t kind)
{
        struct build_walker w;
        ir_edgeset_t        *edges = &_get_irg_edge_info(irg, kind)->edges;
        ir_edge_t           *e;
        ir_edgeset_iterator_t  iter;

        w.irg           = irg;
        w.kind          = kind;
        w.reachable     = bitset_alloca(get_irg_last_idx(irg));
        w.problem_found = 0;

        /* Clear the present bit in all edges available. */
        foreach_ir_edgeset(edges, e, iter) {
                e->present = 0;
        }

        irg_walk_graph(irg, verify_set_presence, verify_list_presence, &w);

        /*
         * Dump all edges which are not invalid and not present.
         * These edges are superfluous and their presence in the
         * edge set is wrong.
         */
        foreach_ir_edgeset(edges, e, iter) {
                if (! e->invalid && ! e->present && bitset_is_set(w.reachable, get_irn_idx(e->src))) {
                        w.problem_found = 1;
                        ir_fprintf(stderr, "Edge Verifier: edge(%ld) %+F,%d is superfluous\n", edge_get_id(e), e->src, e->pos);
                }
        }

        return w.problem_found;
}

#define IGNORE_NODE(irn) (is_Bad((irn)) || is_Block((irn)))

/**
 * Clear link field of all nodes.
 */
static void clear_links(ir_node *irn, void *env) {
        struct build_walker *w  = env;
        bitset_t            *bs;

        if (IGNORE_NODE(irn)) {
                set_irn_link(irn, NULL);
                return;
        }

        bs = bitset_malloc(get_irg_last_idx(w->irg));
        set_irn_link(irn, bs);
}

/**
 * Increases count (stored in link field) for all operands of a node.
 */
static void count_user(ir_node *irn, void *env) {
        int i;
        int first;
        (void) env;

        first = -1;
        for (i = get_irn_arity(irn) - 1; i >= first; --i) {
                ir_node  *op = get_irn_n(irn, i);
                bitset_t *bs = get_irn_link(op);

                if (bs)
                        bitset_set(bs, get_irn_idx(irn));
        }
}

/**
 * Verifies if collected count, number of edges in list and stored edge count are in sync.
 */
static void verify_edge_counter(ir_node *irn, void *env) {
        struct build_walker    *w = env;
        bitset_t               *bs;
        int                    list_cnt;
        int                    ref_cnt;
        int                    edge_cnt;
        unsigned long          idx;
        const struct list_head *head;
        const struct list_head *pos;

        if (IGNORE_NODE(irn))
                return;

        bs       = get_irn_link(irn);
        list_cnt = 0;
        ref_cnt  = 0;
        edge_cnt = _get_irn_edge_info(irn, EDGE_KIND_NORMAL)->out_count;
        head     = _get_irn_outs_head(irn, EDGE_KIND_NORMAL);

        /* We can iterate safely here, list heads have already been verified. */
        list_for_each(pos, head) {
                ++list_cnt;
        }

        /* check all nodes that reference us and count edges that point number
         * of ins that actually point to us */
        ref_cnt = 0;
        bitset_foreach(bs, idx) {
                int i, arity;
                ir_node *src = get_idx_irn(w->irg, idx);

                arity = get_irn_arity(src);
                for (i = 0; i < arity; ++i) {
                        ir_node *in = get_irn_n(src, i);
                        if (in == irn)
                                ++ref_cnt;
                }
        }

        if (edge_cnt != list_cnt) {
                w->problem_found = 1;
                ir_fprintf(stderr, "Edge Verifier: edge count is %d, but %d edge(s) are recorded in list at %+F\n",
                        edge_cnt, list_cnt, irn);
        }

        if (ref_cnt != list_cnt) {
                w->problem_found = 1;
                ir_fprintf(stderr, "Edge Verifier: %+F reachable by %d node(s), but the list contains %d edge(s)\n",
                        irn, ref_cnt, list_cnt);

                /* Matze: buggy if a node has multiple ins pointing at irn */
#if 0
                list_for_each(pos, head) {
                        ir_edge_t *edge = list_entry(pos, ir_edge_t, list);
                        bitset_flip(bs, get_irn_idx(edge->src));
                }

                if (ref_cnt < list_cnt)
                        fprintf(stderr,"               following nodes are recorded in list, but not as user:\n");
                else
                        fprintf(stderr,"               following nodes are user, but not recorded in list:\n");

                fprintf(stderr,"              ");
                bitset_foreach(bs, idx) {
                        ir_node *src = get_idx_irn(w->irg, idx);
                        ir_fprintf(stderr, " %+F", src);
                }
                fprintf(stderr, "\n");
#endif
        }

        bitset_free(bs);
}

/**
 * Verifies the out edges of an irg.
 */
int edges_verify(ir_graph *irg) {
        struct build_walker w;
        int    problem_found = 0;

        /* verify normal edges only */
        problem_found  = edges_verify_kind(irg, EDGE_KIND_NORMAL);

        w.irg           = irg;
        w.kind          = EDGE_KIND_NORMAL;
        w.problem_found = 0;

        /* verify counter */
        irg_walk_anchors(irg, clear_links, count_user, &w);
        irg_walk_anchors(irg, NULL, verify_edge_counter, &w);

        return problem_found ? 1 : w.problem_found;
}

void init_edges(void) {
        FIRM_DBG_REGISTER(dbg, DBG_EDGES);
        /* firm_dbg_set_mask(dbg, -1); */
}

void edges_init_dbg(int do_dbg) {
        edges_dbg = do_dbg;
}

void edges_activate(ir_graph *irg) {
        edges_activate_kind(irg, EDGE_KIND_NORMAL);
        edges_activate_kind(irg, EDGE_KIND_BLOCK);
        if (get_irg_phase_state(irg) == phase_backend)
                edges_activate_kind(irg, EDGE_KIND_DEP);
}

void edges_deactivate(ir_graph *irg) {
        if (get_irg_phase_state(irg) == phase_backend)
                edges_deactivate_kind(irg, EDGE_KIND_DEP);
        edges_deactivate_kind(irg, EDGE_KIND_BLOCK);
        edges_deactivate_kind(irg, EDGE_KIND_NORMAL);
}

int edges_assure(ir_graph *irg) {
        int activated = edges_activated(irg);

        if (!activated)
                edges_activate(irg);

        return activated;
}

int edges_assure_kind(ir_graph *irg, ir_edge_kind_t kind) {
        int activated = edges_activated_kind(irg, kind);

        if (!activated)
                edges_activate_kind(irg, kind);

        return activated;
}

void edges_node_deleted(ir_node *irn, ir_graph *irg) {
        edges_node_deleted_kind(irn, EDGE_KIND_NORMAL, irg);
        edges_node_deleted_kind(irn, EDGE_KIND_BLOCK, irg);
}


const ir_edge_t *(get_irn_out_edge_first_kind)(const ir_node *irn, ir_edge_kind_t kind) {
        return _get_irn_out_edge_first_kind(irn, kind);
}

const ir_edge_t *(get_irn_out_edge_next)(const ir_node *irn, const ir_edge_t *last) {
        return _get_irn_out_edge_next(irn, last);
}

ir_node *(get_edge_src_irn)(const ir_edge_t *edge) {
        return _get_edge_src_irn(edge);
}

int (get_edge_src_pos)(const ir_edge_t *edge) {
        return _get_edge_src_pos(edge);
}

int (get_irn_n_edges_kind)(const ir_node *irn, ir_edge_kind_t kind) {
        return _get_irn_n_edges_kind(irn, kind);
}

void dump_all_out_edges(ir_node *irn) {
        int i;
        for (i = 0; i < EDGE_KIND_LAST; ++i) {
                const ir_edge_t *edge;

                printf("kind \"%s\"\n", get_kind_str(i));
                foreach_out_edge_kind(irn, edge, i) {
                        ir_printf("\t%+F(%d)\n", edge->src, edge->pos);
                }
        }
}

static void irg_block_edges_walk2(ir_node *bl,
                                irg_walk_func *pre, irg_walk_func *post,
                                void *env) {
        const ir_edge_t *edge, *next;

        if (!Block_block_visited(bl)) {
                mark_Block_block_visited(bl);

                if (pre)
                        pre(bl, env);

                foreach_out_edge_kind_safe(bl, edge, next, EDGE_KIND_BLOCK) {
                        /* find the corresponding successor block. */
                        ir_node *pred = get_edge_src_irn(edge);
                        irg_block_edges_walk2(pred, pre, post, env);
                }

                if (post)
                        post(bl, env);
        }
}

void irg_block_edges_walk(ir_node *node,
                          irg_walk_func *pre, irg_walk_func *post,
                          void *env) {

        assert(edges_activated(current_ir_graph));
        assert(is_Block(node));

        ir_reserve_resources(current_ir_graph, IR_RESOURCE_BLOCK_VISITED);

        inc_irg_block_visited(current_ir_graph);
        irg_block_edges_walk2(node, pre, post, env);

        ir_free_resources(current_ir_graph, IR_RESOURCE_BLOCK_VISITED);
}