[RFC,VRP] Improve intersect_ranges

Message ID 76edd771-749d-f85f-2d0e-84e714abb78e@linaro.org
State New
Headers show

Commit Message

kugan Oct. 6, 2016, 10 p.m.
Hi,

In vrp intersect_ranges, Richard recently changed it to create integer 
value ranges when it is integer singleton.

Maybe we should do the same when the other range is a complex ranges 
with SSA_NAME (like [x+2, +INF])?

Attached patch tries to do this. There are cases where it will be 
beneficial as the  testcase in the patch. (For this testcase to work 
with Early VRP, we need the patch posted at 
https://gcc.gnu.org/ml/gcc-patches/2016-10/msg00413.html)

Bootstrapped and regression tested on x86_64-linux-gnu with no new 
regressions.

Thanks,
Kugan


gcc/testsuite/ChangeLog:

2016-10-07  Kugan Vivekanandarajah  <kuganv@linaro.org>

	* gcc.dg/tree-ssa/evrp6.c: New test.

gcc/ChangeLog:

2016-10-07  Kugan Vivekanandarajah  <kuganv@linaro.org>

	* tree-vrp.c (intersect_ranges): If we failed to handle
	the intersection and the other range involves computation with
	symbolic values, choose integer range if available.

Patch hide | download patch | download mbox

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/evrp6.c b/gcc/testsuite/gcc.dg/tree-ssa/evrp6.c
index e69de29..3740da0 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/evrp6.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/evrp6.c
@@ -0,0 +1,21 @@ 
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-evrp" } */
+
+extern void abort (void);
+
+int
+foo (int k, int j)
+{
+  if (j >= 10)
+    {
+      if (j < k)
+	{
+	  k++;
+	  if (k < 10)
+	    abort ();
+	}
+    }
+
+  return j;
+}
+/* { dg-final { scan-tree-dump "\\\[12, \\+INF" "evrp" } } */
diff --git a/gcc/tree-vrp.c b/gcc/tree-vrp.c
index 7a08be7..2706854 100644
--- a/gcc/tree-vrp.c
+++ b/gcc/tree-vrp.c
@@ -8553,11 +8553,26 @@  intersect_ranges (enum value_range_type *vr0type,
 	gcc_unreachable ();
     }
 
+  /* If one is a complex value range involving SSA_NAME
+     and other is INTEGER_CST, prefer INTEGER_CST.  */
+  else if (vr1type == VR_RANGE
+	   && INTEGER_CST == TREE_CODE (vr1min)
+	   && INTEGER_CST == TREE_CODE (vr1max)
+	   && (((INTEGER_CST != TREE_CODE (*vr0min)
+		 && SSA_NAME != TREE_CODE (*vr0min))
+		|| ((INTEGER_CST != TREE_CODE (*vr0max)
+		     && SSA_NAME != TREE_CODE (*vr0max))))))
+    {
+      *vr0type = vr1type;
+      *vr0min = vr1min;
+      *vr0max = vr1max;
+    }
+
   /* As a fallback simply use { *VRTYPE, *VR0MIN, *VR0MAX } as
      result for the intersection.  That's always a conservative
      correct estimate unless VR1 is a constant singleton range
      in which case we choose that.  */
-  if (vr1type == VR_RANGE
+  else if (vr1type == VR_RANGE
       && is_gimple_min_invariant (vr1min)
       && vrp_operand_equal_p (vr1min, vr1max))
     {