X-Git-Url: http://nsz.repo.hu/git/?a=blobdiff_plain;f=ir%2Fana%2Firdom.c;h=080d148d4e252974636223e470175e87d16f62d9;hb=02f098c997643c82451cd29b6c44d8a75cb4d8d8;hp=9f8bb72792e6efe32d158ace1c461a0d0e0631d3;hpb=a58a82dcc39d39e7797cdfe3912bac5363e2a7b9;p=libfirm

diff --git a/ir/ana/irdom.c b/ir/ana/irdom.c
index 9f8bb7279..080d148d4 100644
--- a/ir/ana/irdom.c
+++ b/ir/ana/irdom.c
@@ -1,52 +1,63 @@
 /*
- * Project:     libFIRM
- * File name:   ir/ana/irdom.c
- * Purpose:     Construct and access dominator tree.
- * Author:      Goetz Lindenmaier
- * Modified by:
- * Created:     2.2002
- * CVS-ID:      $Id$
- * Copyright:   (c) 2002-2003 Universität Karlsruhe
- * Licence:     This file protected by GPL -  GNU GENERAL PUBLIC LICENSE.
+ * 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.
  */
 
-#ifdef HAVE_CONFIG_H
+/**
+ * @file
+ * @brief     Construct and access dominator / post dominator tree.
+ * @author    Goetz Lindenmaier, Michael Beck, Rubino Geiss
+ * @date      2.2002
+ */
 #include "config.h"
-#endif
 
-#ifdef HAVE_STRING_H
 #include <string.h>
-#endif
 
 #include "irouts.h"
 
 #include "xmalloc.h"
 #include "irgwalk.h"
 #include "irdom_t.h"
-#include "irgraph_t.h"   /* To access state field. */
+#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)
-
-/*--------------------------------------------------------------------*/
-/** Accessing the dominator data structures                          **/
-/*--------------------------------------------------------------------*/
+#define get_dom_info(bl)  (&(bl)->attr.block.dom)
+#define get_pdom_info(bl) (&(bl)->attr.block.pdom)
 
-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;
+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 */
+		ir_graph *irg = get_irn_irg(bl);
+		return new_r_Bad(irg, mode_BB);
+	}
+	return get_dom_info(bl)->idom;
 }
 
-void set_Block_idom(ir_node *bl, ir_node *n) {
-	dom_info *bli = get_dom_info(bl);
+void set_Block_idom(ir_node *bl, ir_node *n)
+{
+	ir_dom_info *bli = get_dom_info(bl);
 
-  assert(get_irn_op(bl) == op_Block);
+	assert(is_Block(bl));
 
 	/* Set the immediate dominator of bl to n */
 	bli->idom = n;
@@ -55,32 +66,93 @@ void set_Block_idom(ir_node *bl, ir_node *n) {
 	 * If we don't set the root of the dominator tree
 	 * Append bl to the dominates queue of n.
 	 */
-	if(n != NULL) {
-		dom_info *ni = get_dom_info(n);
+	if (n != NULL) {
+		ir_dom_info *ni = get_dom_info(n);
 
 		bli->next = ni->first;
 		ni->first = bl;
 	}
 }
 
-int get_Block_pre_num(const ir_node *bl) {
-  assert(get_irn_op(bl) == op_Block);
-  return bl->attr.block.dom.pre_num;
+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 */
+		ir_graph *irg = get_irn_irg(bl);
+		return new_r_Bad(irg, mode_BB);
+	}
+	return get_pdom_info(bl)->idom;
 }
 
-void set_Block_pre_num(ir_node *bl, int num) {
-  assert(get_irn_op(bl) == op_Block);
-  bl->attr.block.dom.pre_num = num;
+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_depth(const ir_node *bl) {
-  assert(get_irn_op(bl) == op_Block);
-  return bl->attr.block.dom.dom_depth;
+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_depth(ir_node *bl, int depth) {
-  assert(get_irn_op(bl) == op_Block);
-  bl->attr.block.dom.dom_depth = depth;
+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)
@@ -95,9 +167,21 @@ unsigned get_Block_dom_max_subtree_pre_num(const ir_node *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;
+}
+
 int block_dominates(const ir_node *a, const ir_node *b)
 {
-	const dom_info *ai, *bi;
+	const ir_dom_info *ai, *bi;
 
 	if (is_Block(a) && is_Block(b)) {
 		ai = get_dom_info(a);
@@ -109,6 +193,95 @@ int block_dominates(const ir_node *a, const ir_node *b)
 	return 0;
 }
 
+int block_strictly_dominates(const ir_node *a, const ir_node *b)
+{
+	return (a != b) && block_dominates(a, b);
+}
+
+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;
+}
+
+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));
@@ -121,29 +294,76 @@ ir_node *get_Block_dominated_next(const ir_node *bl)
 	return get_dom_info(bl)->next;
 }
 
+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;
+}
+
+int block_strictly_postdominates(const ir_node *a, const ir_node *b)
+{
+	return (a != b) && block_postdominates(a, b);
+}
+
+ir_node *get_Block_postdominated_first(const ir_node *bl)
+{
+	assert(is_Block(bl));
+	return get_pdom_info(bl)->first;
+}
+
+ir_node *get_Block_postdominated_next(const ir_node *bl)
+{
+	assert(is_Block(bl));
+	return get_pdom_info(bl)->next;
+}
+
 void dom_tree_walk(ir_node *bl, irg_walk_func *pre,
 		irg_walk_func *post, void *env)
 {
 	ir_node *p;
 
-	if(pre)
+	if (pre)
 		pre(bl, env);
 
 	dominates_for_each(bl, p) {
 		dom_tree_walk(p, pre, post, env);
 	}
 
-	if(post)
+	if (post)
+		post(bl, env);
+}
+
+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);
 }
 
 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 node. */
+	/* 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
+	assert(is_irg_state(irg, IR_GRAPH_STATE_CONSISTENT_DOMINANCE)
 			&& "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
@@ -151,22 +371,38 @@ void dom_tree_walk_irg(ir_graph *irg, irg_walk_func *pre,
 	dom_tree_walk(root, pre, post, env);
 }
 
-static void assign_tree_pre_order(ir_node *bl, void *data)
+void postdom_tree_walk_irg(ir_graph *irg, irg_walk_func *pre,
+		irg_walk_func *post, void *env)
 {
-	unsigned *num = data;
-	dom_info *bi = get_dom_info(bl);
+	/* The root of the post dominator tree should be the End block. */
+	ir_node *root = get_irg_end_block(irg);
+
+	assert(is_irg_state(irg, IR_GRAPH_STATE_CONSISTENT_POSTDOMINANCE)
+			&& "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 = (unsigned*) data;
+	ir_dom_info *bi = get_dom_info(bl);
 
 	bi->tree_pre_num = (*num)++;
 }
 
-static void assign_tree_pre_order_max(ir_node *bl, void *data)
+static void assign_tree_dom_pre_order_max(ir_node *bl, void *data)
 {
-	dom_info *bi = get_dom_info(bl);
+	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) {
+	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++;
@@ -176,211 +412,461 @@ static void assign_tree_pre_order_max(ir_node *bl, void *data)
 	assert(bi->max_subtree_pre_num >= bi->tree_pre_num);
 }
 
-/*--------------------------------------------------------------------*/
-/*  Building and Removing the dominator datastructure                 */
-/*--------------------------------------------------------------------*/
+static void assign_tree_postdom_pre_order(ir_node *bl, void *data)
+{
+	unsigned *num = (unsigned*) 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);
+}
+
+/**
+ * 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;
 
-static void count_and_init_blocks(ir_node *bl, void *env) {
-  int *n_blocks = (int *) env;
-  (*n_blocks) ++;
+	(*n_blocks) ++;
 
-	memset(get_dom_info(bl), 0, sizeof(dom_info));
-  set_Block_idom(bl, NULL);
-  set_Block_pre_num(bl, -1);
-  set_Block_dom_depth(bl, -1);
+	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 tree. */
+/** 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 */
+	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. */
+/** Struct to pass info through walker. */
 typedef struct {
-  tmp_dom_info *d;
-  int used;
-
+	tmp_dom_info *d;
+	int used;
 } dom_env;
 
 
-/* Walks Blocks along the out datastructure.  If recursion started with
-   Start block misses control dead blocks. */
+/**
+ * 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) {
-  tmp_dom_info *tdi;
-  int i;
-
-  assert(get_irn_op(bl) == op_Block);
-  if (get_irg_block_visited(current_ir_graph) == get_Block_block_visited(bl))
-    return;
-  mark_Block_block_visited(bl);
-  set_Block_pre_num(bl, *used);
-
-  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 = 0; i < get_Block_n_cfg_outs(bl); i++) {
-    ir_node *pred = get_Block_cfg_out(bl, i);
-    assert(get_irn_opcode(pred) == iro_Block);
-    init_tmp_dom_info(pred, tdi, tdi_list, used);
-  }
-}
-
-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;
-}
-
-/* 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(current_ir_graph) != phase_building);
-  current_ir_graph->dom_state = dom_consistent;
-
-  /* Count the number of blocks in the graph. */
-  n_blocks = 0;
-  irg_block_walk(get_irg_end(current_ir_graph), count_and_init_blocks, NULL, &n_blocks);
-
-  /* Memory for temporary information. */
-  tdi_list = xcalloc(n_blocks, sizeof(tdi_list[0]));
-
-  /* We need the out datastructure. */
-  if (current_ir_graph->outs_state != outs_consistent)
-    compute_irg_outs(current_ir_graph);
-
-  /* this with a standard walker as passing the parent to the sons isn't
-     simple. */
-  used = 0;
-  inc_irg_block_visited(current_ir_graph);
-  init_tmp_dom_info(get_irg_start_block(current_ir_graph), NULL, tdi_list, &used);
-  /* If not all blocks are reachable from Start by out 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_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_pre_num (pred) == -1))
-	continue;	/* control-dead */
-
-      u = dom_eval (&tdi_list[get_Block_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 ben 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];
-
-    if (w->dom != w->semi) w->dom = w->dom->dom;
-    set_Block_idom(w->block, w->dom->block);
-    set_Block_dom_depth(w->block, get_Block_dom_depth(w->dom->block) + 1);
-  }
-
-  /* clean up */
-  /*  free(tdi_list); @@@ does not work !!?? */
-  current_ir_graph = rem;
+                              tmp_dom_info *tdi_list, int *used, int n_blocks)
+{
+	tmp_dom_info *tdi;
+	int i;
+
+	assert(is_Block(bl));
+	if (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);
+}
+
+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);
+
+	/* Count the number of blocks in the graph. */
+	n_blocks = 0;
+	irg_block_walk_graph(irg, count_and_init_blocks_dom, NULL, &n_blocks);
+
+	/* 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. */
+		tmp_dom_info *w     = &tdi_list[i];
+		ir_node      *block = w->block;
+		tmp_dom_info *v;
+		int           irn_arity;
+
+		/* Step 2 */
+		irn_arity = get_irn_arity(block);
+		for (j = 0; j < irn_arity;  j++) {
+			ir_node *pred       = get_Block_cfgpred(block, j);
+			ir_node *pred_block = get_nodes_block(pred);
+			tmp_dom_info *u;
+
+			if (is_Bad(pred) || (get_Block_dom_pre_num (pred_block) == -1))
+				continue;    /* unreachable */
+
+			u = dom_eval (&tdi_list[get_Block_dom_pre_num(pred_block)]);
+			if (u->semi < w->semi)
+				w->semi = u->semi;
+		}
+
+		/* handle keep-alives if we are at the end block */
+		if (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_Block(pred) || get_Block_dom_pre_num(pred) == -1)
+					continue;   /* unreachable */
+
+				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_pre_order,
-				assign_tree_pre_order_max, &tree_pre_order);
+		dom_tree_walk(get_irg_start_block(irg), assign_tree_dom_pre_order,
+		                  assign_tree_dom_pre_order_max, &tree_pre_order);
 	}
+	current_ir_graph = rem;
+	set_irg_state(irg, IR_GRAPH_STATE_CONSISTENT_DOMINANCE);
 }
 
-void free_dom_and_peace(ir_graph *irg) {
-  /* Update graph state */
-  assert(get_irg_phase_state(current_ir_graph) != phase_building);
-  current_ir_graph->dom_state = dom_none;
+void assure_doms(ir_graph *irg)
+{
+	if (! is_irg_state(irg, IR_GRAPH_STATE_CONSISTENT_DOMINANCE))
+		compute_doms(irg);
+}
+
+void free_dom(ir_graph *irg)
+{
+	/* Update graph state */
+	assert(get_irg_phase_state(irg) != phase_building);
+	clear_irg_state(irg, IR_GRAPH_STATE_CONSISTENT_DOMINANCE);
+
+	/* With the implementation right now there is nothing to free,
+	   but better call it anyways... */
+}
+
+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);
+
+	/* Count the number of blocks in the graph. */
+	n_blocks = 0;
+	irg_block_walk_graph(irg, count_and_init_blocks_pdom, NULL, &n_blocks);
+
+	/* 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(get_irg_end_block(irg), assign_tree_postdom_pre_order,
+			assign_tree_postdom_pre_order_max, &tree_pre_order);
+	}
+	current_ir_graph = rem;
+	set_irg_state(irg, IR_GRAPH_STATE_CONSISTENT_POSTDOMINANCE);
+}
+
+void assure_postdoms(ir_graph *irg)
+{
+	if (! is_irg_state(irg, IR_GRAPH_STATE_CONSISTENT_POSTDOMINANCE))
+		compute_postdoms(irg);
+}
+
+void free_postdom(ir_graph *irg)
+{
+	/* Update graph state */
+	assert(get_irg_phase_state(irg) != phase_building);
+	clear_irg_state(irg, IR_GRAPH_STATE_CONSISTENT_POSTDOMINANCE);
 
-  /* With the implementation right now there is nothing to free,
-     but better call it anyways... */
+	/* With the implementation right now there is nothing to free,
+	   but better call it anyways... */
 }