re PR tree-optimization/46172 (ICE: in expand_widen_pattern_expr, at optabs.c:522 with -ftree-vectorize -fno-tree-dce)

2010-11-18  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/46172
	* tree-vect-loop-manip.c (remove_dead_stmts_from_loop): New
	function.
	(slpeel_tree_peel_loop_to_edge): Call it.

	* gcc.dg/torture/pr46172.c: New testcase.

From-SVN: r166908

1 files changed, 35 insertions, 0 deletions

diff --git a/gcc/tree-vect-loop-manip.c b/gcc/tree-vect-loop-manip.c
index f006182..eb7eada 100644
--- a/gcc/tree-vect-loop-manip.c
+++ b/gcc/tree-vect-loop-manip.c
@@ -1107,6 +1107,34 @@ set_prologue_iterations (basic_block bb_before_first_loop,
 }
 
 
+/* Remove dead assignments from loop NEW_LOOP.  */
+
+static void
+remove_dead_stmts_from_loop (struct loop *new_loop)
+{
+  basic_block *bbs = get_loop_body (new_loop);
+  unsigned i;
+  for (i = 0; i < new_loop->num_nodes; ++i)
+    {
+      gimple_stmt_iterator gsi;
+      for (gsi = gsi_start_bb (bbs[i]); !gsi_end_p (gsi);)
+	{
+	  gimple stmt = gsi_stmt (gsi);
+	  if (is_gimple_assign (stmt)
+	      && TREE_CODE (gimple_assign_lhs (stmt)) == SSA_NAME
+	      && has_zero_uses (gimple_assign_lhs (stmt)))
+	    {
+	      gsi_remove (&gsi, true);
+	      release_defs (stmt);
+	    }
+	  else
+	    gsi_next (&gsi);
+	}
+    }
+  free (bbs);
+}
+
+
 /* Function slpeel_tree_peel_loop_to_edge.
 
    Peel the first (last) iterations of LOOP into a new prolog (epilog) loop
@@ -1415,6 +1443,13 @@ slpeel_tree_peel_loop_to_edge (struct loop *loop,
   if (update_first_loop_count)
     slpeel_make_loop_iterate_ntimes (first_loop, first_niters);
 
+  /* Remove all pattern statements from the loop copy.  They will confuse
+     the expander if DCE is disabled.
+     ???  The pattern recognizer should be split into an analysis and
+     a transformation phase that is then run only on the loop that is
+     going to be transformed.  */
+  remove_dead_stmts_from_loop (new_loop);
+
   adjust_vec_debug_stmts ();
 
   BITMAP_FREE (definitions);