re PR tree-optimization/25501 (Segfault)

gcc/
	PR tree-optimization/25501
	* tree-cfgcleanup.c (merge_phi_nodes): Check that RESULT is
	used in the PHI argument corresponding to the edge from BB to
	DEST.

gcc/testsuite/
	PR tree-optimization/25501
	* testsuite/gcc.dg/tree-ssa/pr25501.c: New.

From-SVN: r108853

gcc/ChangeLog

+2005-12-20  Kazu Hirata  <kazu@codesourcery.com>
+
+	PR tree-optimization/25501
+	* tree-cfgcleanup.c (merge_phi_nodes): Check that RESULT is
+	used in the PHI argument corresponding to the edge from BB to
+	DEST.
+
 2005-12-20  Richard Guenther  <rguenther@suse.de>
 
 	Revert

gcc/testsuite/ChangeLog

+2005-12-20  Kazu Hirata  <kazu@codesourcery.com>
+
+	PR tree-optimization/25501
+	* testsuite/gcc.dg/tree-ssa/pr25501.c: New.
+
 2005-12-20  Richard Guenther  <rguenther@suse.de>
 
 	Revert

gcc/testsuite/gcc.dg/tree-ssa/pr25501.c

+/* PR tree-optimization/25501
+   The PHI merge pass used to try to merge PHI nodes that cannot
+   actually merged, causing a segfault later.  Make sure that does not
+   happen any more.  */
+
+/* { dg-options "-O1 -fdump-tree-mergephi" } */
+
+int
+foo (int a)
+{
+  int b;
+  int c;
+  int d;
+
+  if (a == 2)
+    b = 3;
+  else
+    b = 5;
+
+  c = 7;
+
+  d = 11;
+
+  for (;;)
+    {
+      if (d == 5)
+	break;
+
+      d = b;
+    }
+
+  return 13;
+}
+
+/* { dg-final { scan-tree-dump-times "Removing basic block" 0 "mergephi"} } */
+/* { dg-final { cleanup-tree-dump "mergephi" } } */

gcc/tree-cfgcleanup.c

@@ -746,6 +746,7 @@ merge_phi_nodes (void)
       else
 	{
 	  tree phi;
+	  unsigned int dest_idx = single_succ_edge (bb)->dest_idx;
 
 	  /* BB dominates DEST.  There may be many users of the PHI
 	     nodes in BB.  However, there is still a trivial case we
@@ -767,7 +768,8 @@ merge_phi_nodes (void)
 	      /* Get the single use of the result of this PHI node.  */
   	      if (!single_imm_use (result, &imm_use, &use_stmt)
 		  || TREE_CODE (use_stmt) != PHI_NODE
-		  || bb_for_stmt (use_stmt) != dest)
+		  || bb_for_stmt (use_stmt) != dest
+		  || PHI_ARG_DEF (use_stmt, dest_idx) != result)
 		break;
 	    }