re PR tree-optimization/23821 (DOM and VRP creating harder to optimize code)

2009-10-05  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/23821
	* tree-vrp.c (vrp_finalize): Do not perform copy propagation.
	* tree-ssa-dom.c (cprop_operand): Do not propagate copies into
	simple IV increments.

	* gcc.dg/torture/pr23821.c: New testcase.

From-SVN: r152449

gcc/ChangeLog

+2009-10-05  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/23821
+	* tree-vrp.c (vrp_finalize): Do not perform copy propagation.
+	* tree-ssa-dom.c (cprop_operand): Do not propagate copies into
+	simple IV increments.
+
 2009-10-05  Ramana Radhakrishnan  <ramana.radhakrishnan@arm.com>
 
         * config/arm/arm.c (arm_override_options): Really initialize

gcc/testsuite/ChangeLog

+2009-10-05  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/23821
+	* gcc.dg/torture/pr23821.c: New testcase.
+
 2009-10-05  Daniel Kraft  <d@domob.eu>
 
 	PR fortran/41403

gcc/testsuite/gcc.dg/torture/pr23821.c

+/* { dg-do compile } */
+/* { dg-skip-if "" { *-*-* } { "-O0" } { "" } } */
+/* At -O1 DOM threads a jump in a non-optimal way which leads to
+   the bogus propagation.  */
+/* { dg-skip-if "" { *-*-* } { "-O1" } { "" } } */
+/* { dg-options "-fdump-tree-ivcanon-details" } */
+
+static int a[199];
+
+extern void abort (void);
+
+int
+main ()
+{
+  int i, x;
+  for (i = 0; i < 199; i++)
+    {
+      x = a[i];
+      if (x != i)
+	abort ();
+    }
+  return 0;
+}
+
+/* Verify that we do not propagate the equivalence x == i into the
+   induction variable increment.  */
+
+/* { dg-final { scan-tree-dump "Added canonical iv" "ivcanon" } } */
+/* { dg-final { cleanup-tree-dump "ivcanon" } } */

gcc/tree-ssa-dom.c

@@ -1998,6 +1998,12 @@ cprop_operand (gimple stmt, use_operand_p op_p)
       if (loop_depth_of_name (val) > loop_depth_of_name (op))
 	return;
 
+      /* Do not propagate copies into simple IV increment statements.
+         See PR23821 for how this can disturb IV analysis.  */
+      if (TREE_CODE (val) != INTEGER_CST
+	  && simple_iv_increment_p (stmt))
+	return;
+
       /* Dump details.  */
       if (dump_file && (dump_flags & TDF_DETAILS))
 	{

gcc/tree-vrp.c

@@ -7237,7 +7237,7 @@ vrp_finalize (void)
     }
 
   /* We may have ended with ranges that have exactly one value.  Those
-     values can be substituted as any other copy/const propagated
+     values can be substituted as any other const propagated
      value using substitute_and_fold.  */
   single_val_range = XCNEWVEC (prop_value_t, num_ssa_names);
 
@@ -7245,7 +7245,8 @@ vrp_finalize (void)
   for (i = 0; i < num_ssa_names; i++)
     if (vr_value[i]
 	&& vr_value[i]->type == VR_RANGE
-	&& vr_value[i]->min == vr_value[i]->max)
+	&& vr_value[i]->min == vr_value[i]->max
+	&& is_gimple_min_invariant (vr_value[i]->min))
       {
 	single_val_range[i].value = vr_value[i]->min;
 	do_value_subst_p = true;