[PATCH] Try harder for conditional evaluation in VRP

[Richard Biener]

Especially for ops with symbolic ranges it may be preferable
to compare one range with an op such as in
[x + 1, x + 1] < x instead of expanding the range of x on
the rhs to sth unrelated.

So, try harder.

Bootstrapped and tested on x86_64-unknown-linux-gnu, applied.

Richard.

2014-05-27  Richard Biener  <rguent...@suse.de>

        * tree-vrp.c (vrp_evaluate_conditional_warnv_with_ops_using_ranges):
        Try using literal operands when comparing value-ranges failed.

Index: gcc/tree-vrp.c
===================================================================
--- gcc/tree-vrp.c      (revision 210931)
+++ gcc/tree-vrp.c      (working copy)
@@ -6919,14 +6919,15 @@ vrp_evaluate_conditional_warnv_with_ops_
   vr0 = (TREE_CODE (op0) == SSA_NAME) ? get_value_range (op0) : NULL;
   vr1 = (TREE_CODE (op1) == SSA_NAME) ? get_value_range (op1) : NULL;
 
+  tree res = NULL_TREE;
   if (vr0 && vr1)
-    return compare_ranges (code, vr0, vr1, strict_overflow_p);
-  else if (vr0 && vr1 == NULL)
-    return compare_range_with_value (code, vr0, op1, strict_overflow_p);
-  else if (vr0 == NULL && vr1)
-    return (compare_range_with_value
+    res = compare_ranges (code, vr0, vr1, strict_overflow_p);
+  if (!res && vr0)
+    res = compare_range_with_value (code, vr0, op1, strict_overflow_p);
+  if (!res && vr1)
+    res = (compare_range_with_value
            (swap_tree_comparison (code), vr1, op0, strict_overflow_p));
-  return NULL;
+  return res;
 }
 
 /* Helper function for vrp_evaluate_conditional_warnv. */