diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 222af4d7715..6c85de4fdcd 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2010-11-26  Alexandre Oliva  <aoliva@redhat.com>
+
+	PR debug/46258
+	* tree-cfg.c (replace_uses_by): Don't mark BBs as altered on
+	debug stmts.
+
 2010-11-26  Alexandre Oliva  <aoliva@redhat.com>
 
 	* toplev.c (finalize): Add no_backend parameter.  Don't finish
diff --git a/gcc/tree-cfg.c b/gcc/tree-cfg.c
index 0745a681347..7944f8c7809 100644
--- a/gcc/tree-cfg.c
+++ b/gcc/tree-cfg.c
@@ -1570,7 +1570,7 @@ replace_uses_by (tree name, tree val)
 	  size_t i;
 
 	  fold_stmt_inplace (stmt);
-	  if (cfgcleanup_altered_bbs)
+	  if (cfgcleanup_altered_bbs && !is_gimple_debug (stmt))
 	    bitmap_set_bit (cfgcleanup_altered_bbs, gimple_bb (stmt)->index);
 
 	  /* FIXME.  This should go in update_stmt.  */