From a355164b55855756790d0ad5c9c1fd953dfc20cf Mon Sep 17 00:00:00 2001
From: Matthias Braun <matze@braunis.de>
Date: Tue, 7 Oct 2008 17:32:21 +0000
Subject: [PATCH] revert change for now breaks 255.vortex and 253.perlbmk

[r22586]
---
 ir/ana/irdom.c | 79 +++++++++++++++++++++++++++++++++-----------------
 1 file changed, 53 insertions(+), 26 deletions(-)

diff --git a/ir/ana/irdom.c b/ir/ana/irdom.c
index 789d8c336..a878a410b 100644
--- a/ir/ana/irdom.c
+++ b/ir/ana/irdom.c
@@ -444,15 +444,13 @@ static void assign_tree_postdom_pre_order_max(ir_node *bl, void *data)
  * count the number of blocks and clears the post dominance info
  */
 static void count_and_init_blocks_pdom(ir_node *bl, void *env) {
-	if (is_Block(bl)) {
-		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);
-	}
+	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. */
@@ -596,15 +594,13 @@ INLINE static void dom_link(tmp_dom_info *v, tmp_dom_info *w) {
  * Walker: count the number of blocks and clears the dominance info
  */
 static void count_and_init_blocks_dom(ir_node *bl, void *env) {
-	if (is_Block(bl)) {
-		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);
-	}
+	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);
 }
 
 /**
@@ -612,21 +608,52 @@ static void count_and_init_blocks_dom(ir_node *bl, void *env) {
  *
  * - 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;
 
-	/*
-	 * Normally one would use irg_block_walk_graph() here, however, this does NOT
-	 * guarantee that all UNREACHABLE blocks are visited.
-	 * This could led to wrong dominance info in those blocks, causing
-	 * the verifier to crash for instance.
-	 * So, we visit EVERY node to ensure the info is updated.
-	 */
-	irg_walk_graph(irg, pre, NULL, &n_blocks);
+	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)) {
+				if (Block_block_visited(pred))
+					continue;
+
+				/* we found an endless loop */
+				dec_irg_block_visited(irg);
+				irg_block_walk(pred, pre, NULL, &n_blocks);
+			}
+			in[j++] = pred;
+		}
+		if (j != arity) {
+			/* we kill some Block keep-alives */
+			set_End_keepalives(end, j, in);
+			set_irg_outs_inconsistent(irg);
+		}
+	}
+
+	current_ir_graph = rem;
 	return n_blocks;
 }
 
-- 
2.20.1