[libfirm] / ir / ana / irdom.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     Construct and access dominator / post dominator tree.
 * @author    Goetz Lindenmaier, Michael Beck, Rubino Geiss
 * @date      2.2002
 * @version   $Id$
 */
#include "config.h"

#include <string.h>

#include "irouts.h"

#include "xmalloc.h"
#include "irgwalk.h"
#include "irdom_t.h"
#include "irgraph_t.h"
#include "irnode_t.h"
#include "ircons_t.h"
#include "array_t.h"
#include "iredges.h"


#define get_dom_info(bl)  (&(bl)->attr.block.dom)
#define get_pdom_info(bl) (&(bl)->attr.block.pdom)

/*--------------------------------------------------------------------*/
/** Accessing the dominator and post dominator data structures       **/
/*--------------------------------------------------------------------*/

ir_node *get_Block_idom(const ir_node *bl)
{
        assert(is_Block(bl));
        if (get_Block_dom_depth(bl) == -1) {
                /* This block is not reachable from Start */
                return new_Bad();
        }
        return get_dom_info(bl)->idom;
}

void set_Block_idom(ir_node *bl, ir_node *n)
{
        ir_dom_info *bli = get_dom_info(bl);

        assert(is_Block(bl));

        /* Set the immediate dominator of bl to n */
        bli->idom = n;

        /*
         * If we don't set the root of the dominator tree
         * Append bl to the dominates queue of n.
         */
        if(n != NULL) {
                ir_dom_info *ni = get_dom_info(n);

                bli->next = ni->first;
                ni->first = bl;
        }
}

ir_node *get_Block_ipostdom(const ir_node *bl)
{
        assert(is_Block(bl));
        if (get_Block_postdom_depth(bl) == -1) {
                /* This block is not reachable from Start */
                return new_Bad();
        }
        return get_pdom_info(bl)->idom;
}

void set_Block_ipostdom(ir_node *bl, ir_node *n)
{
        ir_dom_info *bli = get_pdom_info(bl);

        assert(is_Block(bl));

        /* Set the immediate post dominator of bl to n */
        bli->idom = n;

        /*
         * If we don't set the root of the post dominator tree
         * Append bl to the post dominates queue of n.
         */
        if(n != NULL) {
                ir_dom_info *ni = get_pdom_info(n);

                bli->next = ni->first;
                ni->first = bl;
        }
}

int get_Block_dom_pre_num(const ir_node *bl)
{
        assert(is_Block(bl));
        return get_dom_info(bl)->pre_num;
}

void set_Block_dom_pre_num(ir_node *bl, int num)
{
        assert(is_Block(bl));
        get_dom_info(bl)->pre_num = num;
}

int get_Block_dom_depth(const ir_node *bl)
{
        assert(is_Block(bl));
        return get_dom_info(bl)->dom_depth;
}

void set_Block_dom_depth(ir_node *bl, int depth)
{
        assert(is_Block(bl));
        get_dom_info(bl)->dom_depth = depth;
}


int get_Block_postdom_pre_num(const ir_node *bl)
{
        assert(is_Block(bl));
        return get_pdom_info(bl)->pre_num;
}

void set_Block_postdom_pre_num(ir_node *bl, int num)
{
        assert(is_Block(bl));
        get_pdom_info(bl)->pre_num = num;
}

int get_Block_postdom_depth(const ir_node *bl)
{
        assert(is_Block(bl));
        return get_pdom_info(bl)->dom_depth;
}

void set_Block_postdom_depth(ir_node *bl, int depth)
{
        assert(is_Block(bl));
        get_pdom_info(bl)->dom_depth = depth;
}

unsigned get_Block_dom_tree_pre_num(const ir_node *bl)
{
        assert(is_Block(bl));
        return get_dom_info(bl)->tree_pre_num;
}

unsigned get_Block_dom_max_subtree_pre_num(const ir_node *bl)
{
        assert(is_Block(bl));
        return get_dom_info(bl)->max_subtree_pre_num;
}

unsigned get_Block_pdom_tree_pre_num(const ir_node *bl)
{
        assert(is_Block(bl));
        return get_pdom_info(bl)->tree_pre_num;
}

unsigned get_Block_pdom_max_subtree_pre_num(const ir_node *bl)
{
        assert(is_Block(bl));
        return get_pdom_info(bl)->max_subtree_pre_num;
}

/* Check, if a block dominates another block. */
int block_dominates(const ir_node *a, const ir_node *b)
{
        const ir_dom_info *ai, *bi;

        if (is_Block(a) && is_Block(b)) {
                ai = get_dom_info(a);
                bi = get_dom_info(b);
                return bi->tree_pre_num - ai->tree_pre_num
                        <= ai->max_subtree_pre_num - ai->tree_pre_num;
        }

        return 0;
}

/* Check, if a block strictly dominates another block. */
int block_strictly_dominates(const ir_node *a, const ir_node *b)
{
        return (a != b) && block_dominates(a, b);
}

/* Returns the smallest common dominator block of two nodes. */
ir_node *node_smallest_common_dominator(ir_node *a, ir_node *b)
{
        ir_node *bl_a   = is_Block(a) ? a : get_nodes_block(a);
        ir_node *bl_b   = is_Block(b) ? b : get_nodes_block(b);
        ir_node *dom_bl = NULL;

        /* Check if block of a dominates block of b */
        if (block_dominates(bl_a, bl_b))
                dom_bl = bl_a;
        /* Check if block of b dominates block of a */
        else if (block_dominates(bl_b, bl_a))
                dom_bl = bl_b;
        else {
                /* walk up dominator tree and search for first block dominating a and b */
                while (! dom_bl) {
                        bl_a = get_Block_idom(bl_a);

                        assert(! is_Bad(bl_a) && "block is dead?");

                        if (block_dominates(bl_a, bl_b))
                                dom_bl = bl_a;
                }
        }

        return dom_bl;
}

/* Returns the smallest common dominator block of all users of a node. */
ir_node *node_users_smallest_common_dominator(ir_node *irn, int handle_phi)
{
        int n, j, i = 0, success;
        ir_node **user_blocks, *dom_bl;
        const ir_edge_t *edge;

        assert(! is_Block(irn) && "WRONG USAGE of node_users_smallest_common_dominator");
        assert(edges_activated(get_irn_irg(irn)) && "need edges activated");

        n = get_irn_n_edges(irn);

        /* get array to hold all block of the node users */
        NEW_ARR_A(ir_node *, user_blocks, n);
        foreach_out_edge(irn, edge) {
                ir_node *src = get_edge_src_irn(edge);

                if (is_Phi(src) && handle_phi) {
                        /* get the corresponding cfg predecessor block if phi handling requested */
                        j  = get_edge_src_pos(edge);
                        assert(j >= 0 && "kaputt");
                        user_blocks[i++] = get_Block_cfgpred_block(get_nodes_block(src), j);
                }
                else
                        user_blocks[i++] = is_Block(src) ? src : get_nodes_block(src);
        }

        assert(i == n && "get_irn_n_edges probably broken");

        /* in case of only one user: return the block of the user */
        if (n == 1)
                return user_blocks[0];

        i = 0;
        /* search the smallest block dominating all user blocks */
        do {
                dom_bl  = node_smallest_common_dominator(user_blocks[i], user_blocks[i + 1]);
                success = 1;

                /* check if this block dominates all remaining blocks as well */
                for (j = i + 2; j < n; j++) {
                        if (! block_dominates(dom_bl, user_blocks[j]))
                                success = 0;
                }

                if (success)
                        break;

                /* inherit the dominator block of the first (i + 1) users */
                user_blocks[++i] = dom_bl;
        } while (i < n - 1);

        assert(success && "no block found dominating all users");

        return dom_bl;
}


/* Get the first node in the list of nodes dominated by a given block. */
ir_node *get_Block_dominated_first(const ir_node *bl)
{
        assert(is_Block(bl));
        return get_dom_info(bl)->first;
}

/* Get the next node in a list of nodes which are dominated by some
 * other node. */
ir_node *get_Block_dominated_next(const ir_node *bl)
{
        assert(is_Block(bl));
        return get_dom_info(bl)->next;
}

/* Check, if a block post dominates another block. */
int block_postdominates(const ir_node *a, const ir_node *b)
{
        const ir_dom_info *ai, *bi;

        if (is_Block(a) && is_Block(b)) {
                ai = get_pdom_info(a);
                bi = get_pdom_info(b);
                return bi->tree_pre_num - ai->tree_pre_num
                        <= ai->max_subtree_pre_num - ai->tree_pre_num;
        }

        return 0;
}

/* Check, if a block strictly dominates another block. */
int block_strictly_postdominates(const ir_node *a, const ir_node *b)
{
        return (a != b) && block_postdominates(a, b);
}


/* Get the first node in the list of nodes post dominated by a given block. */
ir_node *get_Block_postdominated_first(const ir_node *bl)
{
        assert(is_Block(bl));
        return get_pdom_info(bl)->first;
}

/* Get the next node in a list of nodes which are post dominated by some
 * other node. */
ir_node *get_Block_postdominated_next(const ir_node *bl)
{
        assert(is_Block(bl));
        return get_pdom_info(bl)->next;
}

/* Visit all nodes in the dominator subtree of a given node. */
void dom_tree_walk(ir_node *bl, irg_walk_func *pre,
                irg_walk_func *post, void *env)
{
        ir_node *p;

        if(pre)
                pre(bl, env);

        dominates_for_each(bl, p) {
                dom_tree_walk(p, pre, post, env);
        }

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

/* Visit all nodes in the post dominator subtree of a given node. */
void postdom_tree_walk(ir_node *bl, irg_walk_func *pre,
                irg_walk_func *post, void *env)
{
        ir_node *p;

        if(pre)
                pre(bl, env);

        postdominates_for_each(bl, p) {
                postdom_tree_walk(p, pre, post, env);
        }

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

/* Walk over the dominator tree of an irg starting at the root. */
void dom_tree_walk_irg(ir_graph *irg, irg_walk_func *pre,
                irg_walk_func *post, void *env)
{
        /* The root of the dominator tree should be the Start block. */
        ir_node *root = get_irg_start_block(irg);

        assert(irg->dom_state == dom_consistent
                        && "The dominators of the irg must be consistent");
        assert(root && "The start block of the graph is NULL?");
        assert(get_dom_info(root)->idom == NULL
                        && "The start node in the graph must be the root of the dominator tree");
        dom_tree_walk(root, pre, post, env);
}

/* Walk over the post dominator tree of an irg starting at the root. */
void postdom_tree_walk_irg(ir_graph *irg, irg_walk_func *pre,
                irg_walk_func *post, void *env)
{
        /* The root of the dominator tree should be the End block. */
        ir_node *root = get_irg_end_block(irg);

        assert(irg->pdom_state == dom_consistent
                        && "The dominators of the irg must be consistent");
        assert(root && "The end block of the graph is NULL?");
        assert(get_pdom_info(root)->idom == NULL
                        && "The End block node in the graph must be the root of the post dominator tree");
        postdom_tree_walk(root, pre, post, env);
}


static void assign_tree_dom_pre_order(ir_node *bl, void *data)
{
        unsigned *num = data;
        ir_dom_info *bi = get_dom_info(bl);

        bi->tree_pre_num = (*num)++;
}

static void assign_tree_dom_pre_order_max(ir_node *bl, void *data)
{
        ir_dom_info *bi = get_dom_info(bl);
        ir_node *p;
        unsigned max = 0;
        unsigned children = 0;
        (void) data;

        for(p = bi->first; p; p = get_dom_info(p)->next) {
                unsigned max_p = get_dom_info(p)->max_subtree_pre_num;
                max = max > max_p ? max : max_p;
                children++;
        }

        bi->max_subtree_pre_num = children > 0 ? max : bi->tree_pre_num;
        assert(bi->max_subtree_pre_num >= bi->tree_pre_num);
}

static void assign_tree_postdom_pre_order(ir_node *bl, void *data)
{
        unsigned *num = data;
        ir_dom_info *bi = get_pdom_info(bl);

        bi->tree_pre_num = (*num)++;
}

static void assign_tree_postdom_pre_order_max(ir_node *bl, void *data)
{
        ir_dom_info *bi = get_pdom_info(bl);
        ir_node *p;
        unsigned max = 0;
        unsigned children = 0;
        (void) data;

        for(p = bi->first; p; p = get_pdom_info(p)->next) {
                unsigned max_p = get_pdom_info(p)->max_subtree_pre_num;
                max = max > max_p ? max : max_p;
                children++;
        }

        bi->max_subtree_pre_num = children > 0 ? max : bi->tree_pre_num;
        assert(bi->max_subtree_pre_num >= bi->tree_pre_num);
}

/*--------------------------------------------------------------------*/
/*  Building and Removing the dominator data structure                */
/*--------------------------------------------------------------------*/

/**
 * count the number of blocks and clears the post dominance info
 */
static void count_and_init_blocks_pdom(ir_node *bl, void *env)
{
        int *n_blocks = (int *) env;
        (*n_blocks) ++;

        memset(get_pdom_info(bl), 0, sizeof(ir_dom_info));
        set_Block_ipostdom(bl, NULL);
        set_Block_postdom_pre_num(bl, -1);
        set_Block_postdom_depth(bl, -1);
}

/** temporary type used while constructing the dominator / post dominator tree. */
typedef struct tmp_dom_info {
        ir_node *block;               /**< backlink */

        struct tmp_dom_info *semi;    /**< semidominator */
        struct tmp_dom_info *parent;
        struct tmp_dom_info *label;   /**< used for LINK and EVAL */
        struct tmp_dom_info *ancestor;/**< used for LINK and EVAL */
        struct tmp_dom_info *dom;     /**< After step 3, if the semidominator of w is
                                           its immediate dominator, then w->dom is the
                                           immediate dominator of w.  Otherwise w->dom
                                           is a vertex v whose number is smaller than
                                           w and whose immediate dominator is also w's
                                           immediate dominator. After step 4, w->dom
                                           is the immediate dominator of w.  */
        struct tmp_dom_info *bucket;  /**< set of vertices with same semidominator */
} tmp_dom_info;

/** Struct to pass info through walker. */
typedef struct {
        tmp_dom_info *d;
        int used;
} dom_env;


/**
 * Walks Blocks along the out data structure.  If recursion started with
 * Start block misses control dead blocks.
 */
static void init_tmp_dom_info(ir_node *bl, tmp_dom_info *parent,
                              tmp_dom_info *tdi_list, int *used, int n_blocks) {
        tmp_dom_info *tdi;
        int i;

        assert(is_Block(bl));
        if (get_irg_block_visited(current_ir_graph) == get_Block_block_visited(bl))
          return;
        mark_Block_block_visited(bl);
        set_Block_dom_pre_num(bl, *used);

        assert(*used < n_blocks);
        tdi = &tdi_list[*used];
        ++(*used);

        tdi->semi     = tdi;
        tdi->label    = tdi;
        tdi->ancestor = NULL;
        tdi->bucket   = NULL;
        tdi->parent   = parent;
        tdi->block    = bl;

        /* Iterate */
        for (i = get_Block_n_cfg_outs_ka(bl) - 1; i >= 0; --i) {
                ir_node *pred = get_Block_cfg_out_ka(bl, i);
                /* can happen for half-optimized dead code (I've seen this in student
                   projects */
                if (!is_Block(pred))
                        continue;

                init_tmp_dom_info(pred, tdi, tdi_list, used, n_blocks);
        }
}

/**
 * Walks Blocks along the control flow.  If recursion started with
 * End block misses blocks in endless loops.
 */
static void init_tmp_pdom_info(ir_node *bl, tmp_dom_info *parent,
                               tmp_dom_info *tdi_list, int* used, int n_blocks) {
        tmp_dom_info *tdi;
        int i;

        assert(is_Block(bl));
        if (get_irg_block_visited(current_ir_graph) == get_Block_block_visited(bl))
          return;
        mark_Block_block_visited(bl);
        set_Block_postdom_pre_num(bl, *used);

        assert(*used < n_blocks);
        tdi = &tdi_list[*used];
        ++(*used);

        tdi->semi = tdi;
        tdi->label = tdi;
        tdi->ancestor = NULL;
        tdi->bucket = NULL;
        tdi->parent = parent;
        tdi->block = bl;

        /* Iterate */
        for (i = get_Block_n_cfgpreds(bl) - 1; i >= 0; --i) {
                ir_node *pred = get_Block_cfgpred_block(bl, i);
                if (is_Bad(pred))
                        continue;
                assert(is_Block(pred));
                init_tmp_pdom_info(pred, tdi, tdi_list, used, n_blocks);
        }

        /* Handle keep-alives. Note that the preprocessing
           in init_construction() had already killed all
           phantom keep-alive edges. All remaining block keep-alives
           are really edges to endless loops.
         */
        if (bl == get_irg_end_block(current_ir_graph)) {
                ir_node *end = get_irg_end(current_ir_graph);

                for (i = get_irn_arity(end) - 1; i >= 0; --i) {
                        ir_node *pred = get_irn_n(end, i);

                        if (is_Block(pred))
                                init_tmp_pdom_info(pred, tdi, tdi_list, used, n_blocks);
                }
        }
}

static void dom_compress(tmp_dom_info *v)
{
        assert (v->ancestor);
        if (v->ancestor->ancestor) {
                dom_compress (v->ancestor);
                if (v->ancestor->label->semi < v->label->semi) {
                        v->label = v->ancestor->label;
                }
                v->ancestor = v->ancestor->ancestor;
        }
}

/**
 * if V is a root, return v, else return the vertex u, not being the
 * root, with minimum u->semi on the path from v to its root.
 */
inline static tmp_dom_info *dom_eval(tmp_dom_info *v)
{
        if (!v->ancestor) return v;
        dom_compress (v);
        return v->label;
}

/** make V W's ancestor */
inline static void dom_link(tmp_dom_info *v, tmp_dom_info *w)
{
        w->ancestor = v;
}

/**
 * Walker: count the number of blocks and clears the dominance info
 */
static void count_and_init_blocks_dom(ir_node *bl, void *env)
{
        int *n_blocks = (int *) env;
        (*n_blocks) ++;

        memset(get_dom_info(bl), 0, sizeof(ir_dom_info));
        set_Block_idom(bl, NULL);
        set_Block_dom_pre_num(bl, -1);
        set_Block_dom_depth(bl, -1);
}

/**
 * Initialize the dominance/postdominance construction:
 *
 * - count the number of blocks
 * - clear the dominance info
 * - remove Block-keepalives of live blocks to reduce
 *   the number of "phantom" block edges
 *
 * @param irg  the graph
 * @param pre  a walker function that will be called for every block in the graph
 */
static int init_construction(ir_graph *irg, irg_walk_func *pre)
{
        ir_graph *rem = current_ir_graph;
        ir_node *end;
        int arity;
        int n_blocks = 0;

        current_ir_graph = irg;

        /* this visits only the reachable blocks */
        irg_block_walk(get_irg_end_block(irg), pre, NULL, &n_blocks);

        /* now visit the unreachable (from End) Blocks and remove unnecessary keep-alives */
        end   = get_irg_end(irg);
        arity = get_End_n_keepalives(end);
        if (arity) {    /* we have keep-alives */
                ir_node **in;
                int i, j;

                NEW_ARR_A(ir_node *, in, arity);
                for (i = j = 0; i < arity; i++) {
                        ir_node *pred = get_End_keepalive(end, i);

                        if (!is_Block(pred)) {
                                pred = get_nodes_block(pred);
                                if (!is_Block(pred)) {
                                        /* a node which has a bad block input: kill it */
                                        continue;
                                }
                        }
                        dec_irg_block_visited(irg);
                        irg_block_walk(pred, pre, NULL, &n_blocks);
                        in[j++] = pred;
                }
                if (j != arity) {
                        /* we kill some keep-alives */
                        set_End_keepalives(end, j, in);
                        set_irg_outs_inconsistent(irg);
                }
        }

        current_ir_graph = rem;
        return n_blocks;
}


/* Computes the dominator trees.  Sets a flag in irg to "dom_consistent".
   If the control flow of the graph is changed this flag must be set to
   "dom_inconsistent".  */
void compute_doms(ir_graph *irg)
{
        ir_graph *rem = current_ir_graph;
        int n_blocks, used, i, j;
        tmp_dom_info *tdi_list;   /* Ein Golf? */

        current_ir_graph = irg;

        /* Update graph state */
        assert(get_irg_phase_state(irg) != phase_building);
        irg->dom_state = dom_consistent;

        /* Count the number of blocks in the graph. */
        n_blocks = init_construction(irg, count_and_init_blocks_dom);

        /* Memory for temporary information. */
        tdi_list = XMALLOCNZ(tmp_dom_info, n_blocks);

        /* We need the out data structure. */
        assure_irg_outs(irg);

        /* this with a standard walker as passing the parent to the sons isn't
           simple. */
        used = 0;
        inc_irg_block_visited(irg);
        init_tmp_dom_info(get_irg_start_block(irg), NULL, tdi_list, &used, n_blocks);
        /* If not all blocks are reachable from Start by out edges this assertion
           fails.
           assert(used == n_blocks && "Precondition for dom construction violated"); */
        assert(used <= n_blocks && "Precondition for dom construction violated");
        n_blocks = used;


        for (i = n_blocks-1; i > 0; i--) {  /* Don't iterate the root, it's done. */
                int irn_arity;
                tmp_dom_info *w = &tdi_list[i];
                tmp_dom_info *v;

                /* Step 2 */
                irn_arity = get_irn_arity(w->block);
                for (j = 0; j < irn_arity;  j++) {
                        ir_node *pred = get_Block_cfgpred_block(w->block, j);
                        tmp_dom_info *u;

                        if (is_Bad(pred) || (get_Block_dom_pre_num (pred) == -1))
                                continue;       /* control-dead */

                        u = dom_eval (&tdi_list[get_Block_dom_pre_num(pred)]);
                        if (u->semi < w->semi) w->semi = u->semi;
                }

                /* handle keep-alives if we are at the end block */
                if (w->block == get_irg_end_block(irg)) {
                        ir_node *end = get_irg_end(irg);

                        irn_arity = get_irn_arity(end);
                        for (j = 0; j < irn_arity;  j++) {
                                ir_node *pred = get_irn_n(end, j);
                                tmp_dom_info *u;

                                if (is_no_Block(pred) || get_Block_dom_pre_num(pred) == -1)
                                        continue;       /* control-dead */

                                u = dom_eval (&tdi_list[get_Block_dom_pre_num(pred)]);
                                if (u->semi < w->semi) w->semi = u->semi;
                        }
                }

                /* Add w to w->semi's bucket.  w is in exactly one bucket, so
                   buckets can been implemented as linked lists. */
                w->bucket = w->semi->bucket;
                w->semi->bucket = w;

                dom_link (w->parent, w);

                /* Step 3 */
                while (w->parent->bucket) {
                        tmp_dom_info *u;
                        v = w->parent->bucket;
                        /* remove v from w->parent->bucket */
                        w->parent->bucket = v->bucket;
                        v->bucket = NULL;

                        u = dom_eval (v);
                        if (u->semi < v->semi)
                                v->dom = u;
                        else
                                v->dom = w->parent;
                }
        }
        /* Step 4 */
        tdi_list[0].dom = NULL;
        set_Block_idom(tdi_list[0].block, NULL);
        set_Block_dom_depth(tdi_list[0].block, 1);
        for (i = 1; i < n_blocks;  i++) {
                tmp_dom_info *w = &tdi_list[i];
                int depth;

                if (! w->dom)
                        continue; /* control dead */

                if (w->dom != w->semi) w->dom = w->dom->dom;
                set_Block_idom(w->block, w->dom->block);

                /* blocks dominated by dead one's are still dead */
                depth = get_Block_dom_depth(w->dom->block);
                if (depth > 0)
                        ++depth;
                set_Block_dom_depth(w->block, depth);
        }

        /* clean up */
        free(tdi_list);

        /* Do a walk over the tree and assign the tree pre orders. */
        {
                unsigned tree_pre_order = 0;
                dom_tree_walk_irg(irg, assign_tree_dom_pre_order,
                        assign_tree_dom_pre_order_max, &tree_pre_order);
        }
        current_ir_graph = rem;
}

void assure_doms(ir_graph *irg)
{
        if (get_irg_dom_state(irg) != dom_consistent)
                compute_doms(irg);
}

void free_dom(ir_graph *irg)
{
        /* Update graph state */
        assert(get_irg_phase_state(irg) != phase_building);
        irg->dom_state = dom_none;

        /* With the implementation right now there is nothing to free,
           but better call it anyways... */
}

/* Computes the post dominator trees.  Sets a flag in irg to "dom_consistent".
   If the control flow of the graph is changed this flag must be set to
   "dom_inconsistent".  */
void compute_postdoms(ir_graph *irg)
{
        ir_graph *rem = current_ir_graph;
        int n_blocks, used, i, j;
        tmp_dom_info *tdi_list;

        current_ir_graph = irg;

        /* Update graph state */
        assert(get_irg_phase_state(irg) != phase_building);
        irg->pdom_state = dom_consistent;

        /* Count the number of blocks in the graph. */
        n_blocks = init_construction(irg, count_and_init_blocks_pdom);

        /* Memory for temporary information. */
        tdi_list = XMALLOCNZ(tmp_dom_info, n_blocks);

        /* We need the out data structure. */
        assure_irg_outs(irg);

        /* this with a standard walker as passing the parent to the sons isn't
           simple. */
        used = 0;
        inc_irg_block_visited(irg);
        init_tmp_pdom_info(get_irg_end_block(irg), NULL, tdi_list, &used, n_blocks);
        /* If not all blocks are reachable from End by cfg edges this assertion
           fails.
           assert(used == n_blocks && "Precondition for dom construction violated"); */
        n_blocks = used;


        for (i = n_blocks-1; i > 0; i--) {  /* Don't iterate the root, it's done. */
                int irn_arity;
                tmp_dom_info *w = &tdi_list[i];
                tmp_dom_info *v;

                /* Step 2 */
                irn_arity = get_Block_n_cfg_outs_ka(w->block);
                for (j = 0;  j < irn_arity;  j++) {
                        ir_node *succ = get_Block_cfg_out_ka(w->block, j);
                        tmp_dom_info *u;

                        if (get_Block_postdom_pre_num (succ) == -1)
                                continue;       /* endless-loop */

                        u = dom_eval (&tdi_list[get_Block_postdom_pre_num(succ)]);
                        if (u->semi < w->semi) w->semi = u->semi;
                }
                /* Add w to w->semi's bucket.  w is in exactly one bucket, so
                   buckets can be implemented as linked lists. */
                w->bucket = w->semi->bucket;
                w->semi->bucket = w;

                dom_link (w->parent, w);

                /* Step 3 */
                while (w->parent->bucket) {
                        tmp_dom_info *u;
                        v = w->parent->bucket;
                        /* remove v from w->parent->bucket */
                        w->parent->bucket = v->bucket;
                        v->bucket = NULL;

                        u = dom_eval(v);
                        if (u->semi < v->semi)
                                v->dom = u;
                        else
                                v->dom = w->parent;
                }
        }
        /* Step 4 */
        tdi_list[0].dom = NULL;
        set_Block_ipostdom(tdi_list[0].block, NULL);
        set_Block_postdom_depth(tdi_list[0].block, 1);
        for (i = 1;  i < n_blocks;  i++) {
                tmp_dom_info *w = &tdi_list[i];

                if (w->dom != w->semi) w->dom = w->dom->dom;
                set_Block_ipostdom(w->block, w->dom->block);
                set_Block_postdom_depth(w->block, get_Block_postdom_depth(w->dom->block) + 1);
        }

        /* clean up */
        free(tdi_list);

        /* Do a walk over the tree and assign the tree pre orders. */
        {
                unsigned tree_pre_order = 0;
                postdom_tree_walk_irg(irg, assign_tree_postdom_pre_order,
                        assign_tree_postdom_pre_order_max, &tree_pre_order);
        }
        current_ir_graph = rem;
}

void assure_postdoms(ir_graph *irg)
{
        if (get_irg_postdom_state(irg) != dom_consistent)
                compute_postdoms(irg);
}

void free_postdom(ir_graph *irg)
{
        /* Update graph state */
        assert(get_irg_phase_state(irg) != phase_building);
        irg->pdom_state = dom_none;

        /* With the implementation right now there is nothing to free,
           but better call it anyways... */
}