re PR tree-optimization/22026 (ACATS FAIL C45331A fixed point wrong code (VRP related))

gcc/
	PR tree-optimization/22026
	* tree-vrp.c (extract_range_from_binary_expr): Drop to
	VR_VARYING if a binary expression involving VR_ANTI_RANGE is
	PLUS_EXPR, MINUS_EXPR, or unsigned MULT_EXPR.

testsuite/
	PR tree-optimization/22026
	* gcc.dg/tree-ssa/pr22026.c: New.

From-SVN: r101328

gcc/ChangeLog

-2005-06-25  Kazu Hirata  <kazu@codesourcery.com>
+2005-06-26  Kazu Hirata  <kazu@codesourcery.com>
+
+	PR tree-optimization/22026
+	* tree-vrp.c (extract_range_from_binary_expr): Drop to
+	VR_VARYING if a binary expression involving VR_ANTI_RANGE is
+	PLUS_EXPR, MINUS_EXPR, or unsigned MULT_EXPR.
+
+2005-06-26  Kazu Hirata  <kazu@codesourcery.com>
 
 	* Makefile.in (OBJS-common): Remove duplicate object file
 	names.

gcc/testsuite/ChangeLog

+2005-06-26  Kazu Hirata  <kazu@codesourcery.com>
+
+	PR tree-optimization/22026
+	* gcc.dg/tree-ssa/pr22026.c: New.
+
 2005-06-25  Thomas Koenig <Thomas.Koenig@online.de>
 
 	PR libfortran/21144

gcc/testsuite/gcc.dg/tree-ssa/pr22026.c

+/* PR tree-optimization/22026
+   VRP used think that ~[0,0] + ~[0,0] = ~[0,0], which is wrong.  The
+   same applies to subtraction and unsigned multiplication.  */
+
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-vrp" } */
+
+int
+plus (int x, int y)
+{
+  if (x != 0)
+    if (y != 0)
+      {
+        int z = x + y;
+        if (z != 0)
+          return 1;
+      }
+  return 0;
+}
+
+int
+minus (int x, int y)
+{
+  if (x != 0)
+    if (y != 0)
+      {
+        int z = x - y;
+        if (z != 0)
+          return 1;
+      }
+  return 0;
+}
+
+int
+mult (unsigned x, unsigned y)
+{
+  if (x != 0)
+    if (y != 0)
+      {
+	unsigned z = x * y;
+	if (z != 0)
+	  return 1;
+      }
+  return 0;
+}
+
+/* None of the predicates can be folded in these functions.  */
+/* { dg-final { scan-tree-dump-times "Folding predicate" 0 "vrp" } } */
+/* { dg-final { cleanup-tree-dump "vrp" } } */

gcc/tree-vrp.c

@@ -1107,6 +1107,19 @@ extract_range_from_binary_expr (value_range_t *vr, tree expr)
 	   || code == MIN_EXPR
 	   || code == MAX_EXPR)
     {
+      /* If we have a PLUS_EXPR with two VR_ANTI_RANGEs, drop to
+	 VR_VARYING.  It would take more effort to compute a precise
+	 range for such a case.  For example, if we have op0 == 1 and
+	 op1 == -1 with their ranges both being ~[0,0], we would have
+	 op0 + op1 == 0, so we cannot claim that the sum is in ~[0,0].
+	 Note that we are guaranteed to have vr0.type == vr1.type at
+	 this point.  */
+      if (code == PLUS_EXPR && vr0.type == VR_ANTI_RANGE)
+	{
+	  set_value_range_to_varying (vr);
+	  return;
+	}
+
       /* For operations that make the resulting range directly
 	 proportional to the original ranges, apply the operation to
 	 the same end of each range.  */
@@ -1123,6 +1136,22 @@ extract_range_from_binary_expr (value_range_t *vr, tree expr)
       tree val[4];
       size_t i;
 
+      /* If we have an unsigned MULT_EXPR with two VR_ANTI_RANGEs,
+	 drop to VR_VARYING.  It would take more effort to compute a
+	 precise range for such a case.  For example, if we have
+	 op0 == 65536 and op1 == 65536 with their ranges both being
+	 ~[0,0] on a 32-bit machine, we would have op0 * op1 == 0, so
+	 we cannot claim that the product is in ~[0,0].  Note that we
+	 are guaranteed to have vr0.type == vr1.type at this
+	 point.  */
+      if (code == MULT_EXPR
+	  && vr0.type == VR_ANTI_RANGE
+	  && (flag_wrapv || TYPE_UNSIGNED (TREE_TYPE (op0))))
+	{
+	  set_value_range_to_varying (vr);
+	  return;
+	}
+
       /* Multiplications and divisions are a bit tricky to handle,
 	 depending on the mix of signs we have in the two ranges, we
 	 need to operate on different values to get the minimum and
@@ -1188,6 +1217,19 @@ extract_range_from_binary_expr (value_range_t *vr, tree expr)
     }
   else if (code == MINUS_EXPR)
     {
+      /* If we have a MINUS_EXPR with two VR_ANTI_RANGEs, drop to
+	 VR_VARYING.  It would take more effort to compute a precise
+	 range for such a case.  For example, if we have op0 == 1 and
+	 op1 == 1 with their ranges both being ~[0,0], we would have
+	 op0 - op1 == 0, so we cannot claim that the difference is in
+	 ~[0,0].  Note that we are guaranteed to have
+	 vr0.type == vr1.type at this point.  */
+      if (vr0.type == VR_ANTI_RANGE)
+	{
+	  set_value_range_to_varying (vr);
+	  return;
+	}
+
       /* For MINUS_EXPR, apply the operation to the opposite ends of
 	 each range.  */
       min = vrp_int_const_binop (code, vr0.min, vr1.max);