Check array indices in object_address_invariant_in_loop_p (PR 84357)

object_address_invariant_in_loop_p ignored ARRAY_REF indices on
the basis that:

	  /* Index of the ARRAY_REF was zeroed in analyze_indices, thus we only
	     need to check the stride and the lower bound of the reference.  */

That was true back in 2007 when the code was added:

static void
dr_analyze_indices (struct data_reference *dr, struct loop *nest)
{
  [...]
  while (handled_component_p (aref))
    {
      if (TREE_CODE (aref) == ARRAY_REF)
        {
          op = TREE_OPERAND (aref, 1);
          access_fn = analyze_scalar_evolution (loop, op);
          access_fn = resolve_mixers (nest, access_fn);
          VEC_safe_push (tree, heap, access_fns, access_fn);

          TREE_OPERAND (aref, 1) = build_int_cst (TREE_TYPE (op), 0);
        }

      aref = TREE_OPERAND (aref, 0);
    }

but the assignment was removed a few years ago.  We were therefore
treating "two->arr[i]" and "three->arr[i]" as loop invariant.

2018-02-14  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	PR tree-optimization/84357
	* tree-data-ref.c (object_address_invariant_in_loop_p): Check
	operand 1 of an ARRAY_REF too.

gcc/testsuite/
	PR tree-optimization/84357
	* gcc.dg/vect/pr84357.c: New test.

From-SVN: r257657

gcc/ChangeLog

@@ -1,3 +1,9 @@
+2018-02-14  Richard Sandiford  <richard.sandiford@linaro.org>
+
+	PR tree-optimization/84357
+	* tree-data-ref.c (object_address_invariant_in_loop_p): Check
+	operand 1 of an ARRAY_REF too.
+
 2018-02-14  Oleg Endo  <olegendo@gcc.gnu.org>
 
 	PR target/83831

gcc/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2018-02-14  Richard Sandiford  <richard.sandiford@linaro.org>
+
+	PR tree-optimization/84357
+	* gcc.dg/vect/pr84357.c: New test.
+
 2018-02-14  Oleg Endo  <olegendo@gcc.gnu.org>
 
 	PR target/83831

gcc/testsuite/gcc.dg/vect/pr84357.c

@@ -0,0 +1,31 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-Wall" } */
+
+#define COUNT 32
+
+typedef struct s1 {
+    unsigned char c;
+} s1;
+
+typedef struct s2
+{
+    char pad;
+    s1 arr[COUNT];
+} s2;
+
+typedef struct s3 {
+    s1 arr[COUNT];
+} s3;
+
+s2 * get_s2();
+s3 * gActiveS3;
+void foo()
+{
+    s3 * three = gActiveS3;
+    s2 * two = get_s2();
+
+    for (int i = 0; i < COUNT; i++)
+    {
+        two->arr[i].c = three->arr[i].c;
+    }
+}

gcc/tree-data-ref.c

@@ -2200,13 +2200,10 @@ object_address_invariant_in_loop_p (const struct loop *loop, const_tree obj)
     {
       if (TREE_CODE (obj) == ARRAY_REF)
 	{
-	  /* Index of the ARRAY_REF was zeroed in analyze_indices, thus we only
+	  for (int i = 1; i < 4; ++i)
-	     need to check the stride and the lower bound of the reference.  */
+	    if (chrec_contains_symbols_defined_in_loop (TREE_OPERAND (obj, i),
-	  if (chrec_contains_symbols_defined_in_loop (TREE_OPERAND (obj, 2),
+							loop->num))
-						      loop->num)
+	      return false;
-	      || chrec_contains_symbols_defined_in_loop (TREE_OPERAND (obj, 3),
-							 loop->num))
-	    return false;
 	}
       else if (TREE_CODE (obj) == COMPONENT_REF)
 	{