X-Git-Url: http://nsz.repo.hu/git/?a=blobdiff_plain;f=ir%2Fopt%2Fjumpthreading.c;h=39de745f4dfad750b0b98f6d122a327ab193af37;hb=5ea61f3166daab45e560f0d7955fd4c72d8c7167;hp=135ede9dd9827db039165cf9da85231fcf48edde;hpb=4f8e80463195b1fee6ebbeefb59722faf76134cc;p=libfirm

diff --git a/ir/opt/jumpthreading.c b/ir/opt/jumpthreading.c
index 135ede9dd..39de745f4 100644
--- a/ir/opt/jumpthreading.c
+++ b/ir/opt/jumpthreading.c
@@ -60,7 +60,7 @@ static void add_pred(ir_node* node, ir_node* x)
 	int n;
 	int i;
 
-	assert(is_Block(node) || is_Phi(node));
+	assert(is_Block(node));
 
 	n = get_irn_arity(node);
 	NEW_ARR_A(ir_node*, ins, n + 1);
@@ -83,10 +83,10 @@ static ir_node *search_def_and_create_phis(ir_node *block, ir_mode *mode,
 	ir_node **in;
 	ir_node *dummy;
 
-	/* This is needed because we create bads sometimes */
-	if (is_Bad(block) || is_Block_dead(block)) {
+	/* In case of a bad input to a block we need to return the bad value */
+	if (is_Bad(block)) {
 		ir_graph *irg = get_irn_irg(block);
-		return new_r_Bad(irg);
+		return new_r_Bad(irg, mode);
 	}
 
 	/* the other defs can't be marked for cases where a user of the original
@@ -194,6 +194,16 @@ static void construct_ssa(ir_node *orig_block, ir_node *orig_val,
 	}
 }
 
+/**
+ * jumpthreading produces critical edges, e.g. B-C:
+ *     A         A
+ *  \ /       \  |
+ *   B    =>   B |
+ *  / \       / \|
+ *     C         C
+ *
+ * By splitting this critical edge more threadings might be possible.
+ */
 static void split_critical_edge(ir_node *block, int pos)
 {
 	ir_graph *irg = get_irn_irg(block);
@@ -275,6 +285,13 @@ static void copy_and_fix(const jumpthreading_env_t *env, ir_node *block,
 		ir_node *copy;
 		ir_mode *mode;
 
+		if (is_End(node)) {
+			/* edge is a Keep edge. If the end block is unreachable via normal control flow,
+			 * we must maintain end's reachability with Keeps.
+			 */
+			keep_alive(copy_block);
+			continue;
+		}
 		/* ignore control flow */
 		mode = get_irn_mode(node);
 		if (mode == mode_X || is_Cond(node))
@@ -624,9 +641,10 @@ static void thread_jumps(ir_node* block, void* data)
 	int      selector_evaluated;
 	const ir_edge_t *edge, *next;
 	ir_graph *irg;
-	ir_node *bad;
+	ir_node *badX;
 	int      cnst_pos;
 
+	/* we do not deal with Phis, so restrict this to exactly one cfgpred */
 	if (get_Block_n_cfgpreds(block) != 1)
 		return;
 
@@ -686,7 +704,7 @@ static void thread_jumps(ir_node* block, void* data)
 
 	if (selector_evaluated == 0) {
 		ir_graph *irg = get_irn_irg(block);
-		bad = new_r_Bad(irg);
+		ir_node  *bad = new_r_Bad(irg, mode_X);
 		exchange(projx, bad);
 		*changed = 1;
 		return;
@@ -709,21 +727,27 @@ static void thread_jumps(ir_node* block, void* data)
 	if (copy_block == NULL)
 		return;
 
+	/* We might thread the condition block of an infinite loop,
+	 * such that there is no path to End anymore. */
+	keep_alive(block);
+
 	/* we have to remove the edge towards the pred as the pred now
 	 * jumps into the true_block. We also have to shorten Phis
 	 * in our block because of this */
-	bad      = new_r_Bad(irg);
+	badX     = new_r_Bad(irg, mode_X);
 	cnst_pos = env.cnst_pos;
 
 	/* shorten Phis */
 	foreach_out_edge_safe(env.cnst_pred, edge, next) {
 		ir_node *node = get_edge_src_irn(edge);
 
-		if (is_Phi(node))
+		if (is_Phi(node)) {
+			ir_node *bad = new_r_Bad(irg, get_irn_mode(node));
 			set_Phi_pred(node, cnst_pos, bad);
+		}
 	}
 
-	set_Block_cfgpred(env.cnst_pred, cnst_pos, bad);
+	set_Block_cfgpred(env.cnst_pred, cnst_pos, badX);
 
 	/* the graph is changed now */
 	*changed = 1;
@@ -739,6 +763,10 @@ void opt_jumpthreading(ir_graph* irg)
 
 	remove_critical_cf_edges(irg);
 
+	/* ugly: jump threading might get confused by garbage nodes
+	 * of mode_X in copy_and_fix_node(), so remove all garbage edges. */
+	edges_deactivate(irg);
+
 	edges_assure(irg);
 	ir_reserve_resources(irg, IR_RESOURCE_IRN_LINK | IR_RESOURCE_IRN_VISITED);
 
@@ -753,15 +781,9 @@ void opt_jumpthreading(ir_graph* irg)
 
 	if (changed) {
 		/* control flow changed, some blocks may become dead */
-		set_irg_outs_inconsistent(irg);
 		set_irg_doms_inconsistent(irg);
 		set_irg_extblk_inconsistent(irg);
-		set_irg_loopinfo_inconsistent(irg);
 		set_irg_entity_usage_state(irg, ir_entity_usage_not_computed);
-
-		/* Dead code might be created. Optimize it away as it is dangerous
-		 * to call optimize_df() an dead code. */
-		optimize_cf(irg);
 	}
 }