[Bug rtl-optimization/16967] Iterating gcse.c CPROP and PRE does not reach a fixed point

["steven at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #7 from steven at gcc dot gnu dot org  2006-04-20 20:53 -------
I have tested this test case again with lcm.c patched with the patch below to
check for insertions on edges where an expression is already available. The
abort does not trigger.

The version of GCC that I patched and tested was extracted from SVN with the
following commands: svn co -r {"2004-08-10 15:10"} (etc.)

Index: lcm.c
===================================================================
--- lcm.c       (revision 85749)
+++ lcm.c       (working copy)
@@ -426,10 +426,6 @@ pre_edge_lcm (FILE *file ATTRIBUTE_UNUSE
     dump_sbitmap_vector (file, "earliest", "", earliest, num_edges);
 #endif

-  sbitmap_vector_free (antout);
-  sbitmap_vector_free (antin);
-  sbitmap_vector_free (avout);
-
   later = sbitmap_vector_alloc (num_edges, n_exprs);

   /* Allocate an extra element for the exit block in the laterin vector.  */
@@ -462,6 +458,32 @@ pre_edge_lcm (FILE *file ATTRIBUTE_UNUSE
     }
 #endif

+#if 1
+  {
+    sbitmap *avout_check;
+    sbitmap *insert_ = *insert;
+    int x;
+
+    avout_check = sbitmap_vector_alloc (num_edges, n_exprs);
+    sbitmap_vector_zero (avout_check, num_edges);
+
+    for (x = 0; x < num_edges; x++)
+      {
+       basic_block bb = INDEX_EDGE_PRED_BB (edge_list, x);
+       if (bb->index < 0)
+         continue;
+       sbitmap_copy (avout_check[x], avout[bb->index]);
+       sbitmap_a_and_b (avout_check[x], avout_check[x], insert_[x]);
+       if (sbitmap_first_set_bit (avout_check[x]) >= 0)
+         abort ();
+      }
+  }
+#endif
+
+  sbitmap_vector_free (antout);
+  sbitmap_vector_free (antin);
+  sbitmap_vector_free (avout);
+
   return edge_list;
 }


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16967