[backport from gcc-4.7.1 r187964 <mikpe@it.uu.se>]

gcc/

2012-05-29  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/53516
	* tree-data-ref.c (stmt_with_adjacent_zero_store_dr_p): Reject
	bitfield accesses.
	* tree-vect-data-refs.c (vect_analyze_data_refs): Likewise.

gcc/testsuite/

2012-05-29  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/53516
	* gcc.dg/torture/pr53516.c: New testcase.

--- gcc-4.6.3/gcc/testsuite/gcc.dg/torture/pr53516.c.~1~	1970-01-01 01:00:00.000000000 +0100
+++ gcc-4.6.3/gcc/testsuite/gcc.dg/torture/pr53516.c	2012-06-22 13:03:37.000000000 +0200
@@ -0,0 +1,32 @@
+/* { dg-do run } */
+/* { dg-options "-ftree-vectorize -ftree-loop-distribute-patterns" } */
+
+extern void abort (void);
+
+struct Foo
+{
+  char a : 1;
+  char b : 7;
+};
+
+struct Foo x[256];
+int y[256];
+
+void __attribute__((noinline,noclone)) bar (int n)
+{
+  int i;
+  for (i = 0; i < n; ++i)
+    {
+      x[i].a = 0;
+      y[i] = 3;
+    }
+}
+
+int main()
+{
+  x[5].b = 7;
+  bar (256);
+  if (x[5].b != 7)
+    abort ();
+  return 0;
+}
--- gcc-4.6.3/gcc/tree-data-ref.c.~1~	2011-05-11 15:07:54.000000000 +0200
+++ gcc-4.6.3/gcc/tree-data-ref.c	2012-06-22 13:03:37.000000000 +0200
@@ -5125,26 +5125,33 @@ stores_from_loop (struct loop *loop, VEC
 bool
 stmt_with_adjacent_zero_store_dr_p (gimple stmt)
 {
-  tree op0, op1;
+  tree lhs, rhs;
   bool res;
   struct data_reference *dr;
 
   if (!stmt
       || !gimple_vdef (stmt)
-      || !is_gimple_assign (stmt)
-      || !gimple_assign_single_p (stmt)
-      || !(op1 = gimple_assign_rhs1 (stmt))
-      || !(integer_zerop (op1) || real_zerop (op1)))
+      || !gimple_assign_single_p (stmt))
+    return false;
+
+  lhs = gimple_assign_lhs (stmt);
+  rhs = gimple_assign_rhs1 (stmt);
+
+  /* If this is a bitfield store bail out.  */
+  if (TREE_CODE (lhs) == COMPONENT_REF
+      && DECL_BIT_FIELD (TREE_OPERAND (lhs, 1)))
+    return false;
+
+  if (!(integer_zerop (rhs) || real_zerop (rhs)))
     return false;
 
   dr = XCNEW (struct data_reference);
-  op0 = gimple_assign_lhs (stmt);
 
   DR_STMT (dr) = stmt;
-  DR_REF (dr) = op0;
+  DR_REF (dr) = lhs;
 
   res = dr_analyze_innermost (dr)
-    && stride_of_unit_type_p (DR_STEP (dr), TREE_TYPE (op0));
+    && stride_of_unit_type_p (DR_STEP (dr), TREE_TYPE (lhs));
 
   free_data_ref (dr);
   return res;
--- gcc-4.6.3/gcc/tree-vect-data-refs.c.~1~	2011-12-12 20:43:06.000000000 +0100
+++ gcc-4.6.3/gcc/tree-vect-data-refs.c	2012-06-22 13:03:56.000000000 +0200
@@ -2616,10 +2616,6 @@ vect_analyze_data_refs (loop_vec_info lo
           return false;
         }
 
-      base = unshare_expr (DR_BASE_ADDRESS (dr));
-      offset = unshare_expr (DR_OFFSET (dr));
-      init = unshare_expr (DR_INIT (dr));
-
       if (stmt_can_throw_internal (stmt))
         {
           if (vect_print_dump_info (REPORT_UNVECTORIZED_LOCATIONS))
@@ -2631,6 +2627,23 @@ vect_analyze_data_refs (loop_vec_info lo
           return false;
         }
 
+      if (TREE_CODE (DR_REF (dr)) == COMPONENT_REF
+	  && DECL_BIT_FIELD (TREE_OPERAND (DR_REF (dr), 1)))
+	{
+          if (vect_print_dump_info (REPORT_UNVECTORIZED_LOCATIONS))
+            {
+              fprintf (vect_dump, "not vectorized: statement is bitfield "
+                       "access ");
+              print_gimple_stmt (vect_dump, stmt, 0, TDF_SLIM);
+            }
+
+          return false;
+	}
+
+      base = unshare_expr (DR_BASE_ADDRESS (dr));
+      offset = unshare_expr (DR_OFFSET (dr));
+      init = unshare_expr (DR_INIT (dr));
+
       if (is_gimple_call (stmt))
 	{
 	  if (vect_print_dump_info (REPORT_UNVECTORIZED_LOCATIONS))