re PR rtl-optimization/32283 (Missed induction variable optimization)

	PR tree-optimization/32283
	* tree-ssa-loop-ivopts.c (may_eliminate_iv): Use
	estimated_loop_iterations.
	(determine_use_iv_cost_condition): Decrease cost of expressions
	used in iv elimination.

	* gcc.dg/tree-ssa/loop-31.c: New test.

From-SVN: r128272

gcc/ChangeLog

+2007-09-08  Zdenek Dvorak  <ook@ucw.cz>
+
+	PR tree-optimization/32283
+	* tree-ssa-loop-ivopts.c (may_eliminate_iv): Use
+	estimated_loop_iterations.
+	(determine_use_iv_cost_condition): Decrease cost of expressions
+	used in iv elimination.
+
 2007-09-08  Richard Guenther  <rguenther@suse.de>
 
 	* tree-cfg.c (verify_gimple_expr): Avoid building new

gcc/testsuite/ChangeLog

+2007-09-08  Zdenek Dvorak  <ook@ucw.cz>
+
+	PR tree-optimization/32283
+	* gcc.dg/tree-ssa/loop-31.c: New test.
+
 2007-09-08  Uros Bizjak  <ubizjak@gmail.com>
 
 	PR rtl-optimization/26449

gcc/testsuite/gcc.dg/tree-ssa/loop-31.c

+/* PR 32283 */
+
+/* { dg-do compile } */
+/* { dg-options "-O1 -fdump-tree-optimized" } */
+
+short a[(2048)];
+short foo (int len, int v)
+{
+  int i;
+  for (i = 0; i < len; i++) {
+      a[i] = v;
+  }
+  return a[0];
+}
+
+/* When we do not have addressing mode including multiplication,
+   the memory access should be strength-reduced.  */
+/* { dg-final { scan-tree-dump-times " \\+ 2" 1 "optimized" { target arm-*-* ia64-*-* } } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */

gcc/tree-ssa-loop-ivopts.c

@@ -3623,11 +3623,11 @@ may_eliminate_iv (struct ivopts_data *data,
 {
   basic_block ex_bb;
   edge exit;
-  tree nit, nit_type;
-  tree wider_type, period, per_type;
+  tree nit, period;
   struct loop *loop = data->current_loop;
   aff_tree bnd;
-  
+  double_int period_value, max_niter;
+
   if (TREE_CODE (cand->iv->step) != INTEGER_CST)
     return false;
 
@@ -3650,25 +3650,19 @@ may_eliminate_iv (struct ivopts_data *data,
   if (!nit)
     return false;
 
-  nit_type = TREE_TYPE (nit);
-
   /* Determine whether we may use the variable to test whether niter iterations
      elapsed.  This is the case iff the period of the induction variable is
      greater than the number of iterations.  */
   period = iv_period (cand->iv);
   if (!period)
     return false;
-  per_type = TREE_TYPE (period);
-
-  wider_type = TREE_TYPE (period);
-  if (TYPE_PRECISION (nit_type) < TYPE_PRECISION (per_type))
-    wider_type = per_type;
-  else
-    wider_type = nit_type;
 
-  if (!integer_nonzerop (fold_build2 (GE_EXPR, boolean_type_node,
-				      fold_convert (wider_type, period),
-				      fold_convert (wider_type, nit))))
+  /* Compare the period with the estimate on the number of iterations of the
+     loop.  */
+  if (!estimated_loop_iterations (loop, true, &max_niter))
+    return false;
+  period_value = tree_to_double_int (period);
+  if (double_int_ucmp (period_value, max_niter) <= 0)
     return false;
 
   cand_value_at (loop, cand, use->stmt, nit, &bnd);
@@ -3697,7 +3691,12 @@ determine_use_iv_cost_condition (struct ivopts_data *data,
 
   /* Try iv elimination.  */
   if (may_eliminate_iv (data, use, cand, &bound))
-    elim_cost = force_var_cost (data, bound, &depends_on_elim);
+    {
+      elim_cost = force_var_cost (data, bound, &depends_on_elim);
+      /* The bound is a loop invariant, so it will be only computed
+	 once.  */
+      elim_cost /= AVG_LOOP_NITER (data->current_loop);
+    }
   else
     elim_cost = INFTY;