Fix PR/46200

From-SVN: r166280

gcc/ChangeLog

+2010-11-03  Xinliang David Li  <davidxl@google.com>
+
+       PR target/46200
+       * tree-ssa-loop-ivopts.c (get_computation_cost_at):
+       Adjust cbase if the use stmt is after iv update.
+
 2010-11-03  Kaz Kojima  <kkojima@gcc.gnu.org>
 
 	* config.gcc (sh64*) <tm_file>: Add newlib-stdint.h for

gcc/testsuite/ChangeLog

+2010-11-03  Xinliang David Li  <davidxl@google.com>
+
+       PR target/46200
+       * g++.dg/tree-ssa/ivopts-2.C: New test.
+
 2010-11-03  H.J. Lu  <hongjiu.lu@intel.com>
 
 	PR target/46295

gcc/testsuite/g++.dg/tree-ssa/ivopts-2.C

+/* { dg-do compile { target { i?86-*-* x86_64-*-*  } } } */
+/* { dg-options "-O2 -fdump-tree-ivopts-details" } */
+
+void test (int *b, int *e, int stride)
+  {
+    for (int *p = b; p != e; p += stride)
+      *p = 1;
+  }
+
+/* { dg-final { scan-tree-dump-times "PHI <p" 1 "ivopts"} } */
+/* { dg-final { cleanup-tree-dump "ivopts" } } */

gcc/tree-ssa-loop-ivopts.c

@@ -4027,6 +4027,8 @@ get_computation_cost_at (struct ivopts_data *data,
   STRIP_NOPS (cbase);
   ctype = TREE_TYPE (cbase);
 
+  stmt_is_after_inc = stmt_after_increment (data->current_loop, cand, at);
+
   /* use = ubase + ratio * (var - cbase).  If either cbase is a constant
      or ratio == 1, it is better to handle this like
 
@@ -4045,8 +4047,24 @@ get_computation_cost_at (struct ivopts_data *data,
     }
   else if (ratio == 1)
     {
+      tree real_cbase = cbase;
+
+      /* Check to see if any adjustment is needed.  */
+      if (cstepi == 0 && stmt_is_after_inc)
+        {
+          aff_tree real_cbase_aff;
+          aff_tree cstep_aff;
+
+          tree_to_aff_combination (cbase, TREE_TYPE (real_cbase),
+                                   &real_cbase_aff);
+          tree_to_aff_combination (cstep, TREE_TYPE (cstep), &cstep_aff);
+
+          aff_combination_add (&real_cbase_aff, &cstep_aff);
+          real_cbase = aff_combination_to_tree (&real_cbase_aff);
+        }
+
       cost = difference_cost (data,
-			      ubase, cbase,
+			      ubase, real_cbase,
 			      &symbol_present, &var_present, &offset,
 			      depends_on);
       cost.cost /= avg_loop_niter (data->current_loop);
@@ -4088,7 +4106,6 @@ get_computation_cost_at (struct ivopts_data *data,
 
   /* If we are after the increment, the value of the candidate is higher by
      one iteration.  */
-  stmt_is_after_inc = stmt_after_increment (data->current_loop, cand, at);
   if (stmt_is_after_inc)
     offset -= ratio * cstepi;