re PR tree-optimization/23128 (VRP fails for unsigned values)

2005-08-05  James A. Morrison  <phython@gcc.gnu.org>

        PR tree-optimization/23128
        * tree-vrp.c (vrp_int_const_binop): Check if unsigned addition or
        subtraction wrap, and set TREE_OVERFLOW if they do.

From-SVN: r102800

gcc/ChangeLog

+2005-08-05  James A. Morrison  <phython@gcc.gnu.org>
+
+	PR tree-optimization/23128
+	* tree-vrp.c (vrp_int_const_binop): Check if unsigned addition or
+	subtraction wrap, and set TREE_OVERFLOW if they do.
+
 2005-08-05  Richard Henderson  <rth@redhat.com>
 
 	PR 21728

gcc/testsuite/ChangeLog

 2005-08-05  James A. Morrison  <phython@gcc.gnu.org>
 
+	* gcc.c-torture/execute/vrp-5.c: New test.
+	* gcc.c-torture/execute/vrp-6.c: New test.
+	* gcc.dg/tree-ssa/vrp21.c: New test.
+
+2005-08-05  James A. Morrison  <phython@gcc.gnu.org>
+
 	* g++.dg/parse/pr22514.C: New test.
 
 2005-08-05  J"orn Rennecke <joern.rennecke@st.com>

gcc/testsuite/gcc.c-torture/execute/vrp-5.c

+extern void exit (int);
+extern void abort ();
+
+void test(unsigned int a, unsigned int b)
+{
+  if (a < 5)
+    abort();
+  if (b < 5)
+    abort();
+  if (a + b != 0U)
+    abort();
+}
+
+int main(int argc, char *argv[])
+{
+  unsigned int x = 0x80000000;
+  test(x, x);
+  exit (0);
+}
+
+
+

gcc/testsuite/gcc.c-torture/execute/vrp-6.c

+#include <limits.h>
+
+extern void exit (int);
+extern void abort ();
+
+void test01(unsigned int a, unsigned int b)
+{
+  if (a < 5)
+    abort();
+  if (b < 5)
+    abort();
+  if (a - b != 5)
+    abort();
+}
+
+void test02(unsigned int a, unsigned int b)
+{
+  if (a >= 12)
+    if (b > 15)
+      if (a - b < UINT_MAX - 15U)
+	abort ();
+}
+
+int main(int argc, char *argv[])
+{
+  unsigned x = 0x80000000;
+  test01(x + 5, x);
+  test02(14, 16);
+  exit (0);
+}
+
+
+

gcc/testsuite/gcc.dg/tree-ssa/vrp21.c

+/* { dg-do compile } */
+/* { dg-options "-O1 -ftree-vrp -fdump-tree-vrp" } */
+
+extern void link_error ();
+
+void test01(unsigned int a, unsigned int b)
+{
+  unsigned int x = 0x80000000;
+  if (a < x)
+    if (b < x)
+      if (a > 5)
+        if (a + b == 0U)
+          link_error ();
+}
+
+void test02(unsigned int a, unsigned int b)
+{
+  unsigned int x = 0x80000000;
+  if (a > x)
+    if (b < x)
+      if (a - b == 1U)
+        link_error ();
+}
+
+/* { dg-final { scan-tree-dump-times "link_error" 0 "vrp" } } */
+/* { dg-final { cleanup-tree-dump "vrp" } } */

gcc/tree-vrp.c

@@ -915,10 +915,23 @@ vrp_int_const_binop (enum tree_code code, tree val1, tree val2)
      on -INF and +INF.  */
   res = int_const_binop (code, val1, val2, 0);
 
+  if (TYPE_UNSIGNED (TREE_TYPE (val1)))
+    {
+      int checkz = compare_values (res, val1);
+
+      /* Ensure that res = val1 + val2 >= val1
+         or that res = val1 - val2 <= val1.  */
+      if ((code == PLUS_EXPR && !(checkz == 1 || checkz == 0))
+          || (code == MINUS_EXPR && !(checkz == 0 || checkz == -1)))
+	{
+	  res = copy_node (res);
+	  TREE_OVERFLOW (res) = 1;
+	}
+    }
   /* If the operation overflowed but neither VAL1 nor VAL2 are
      overflown, return -INF or +INF depending on the operation
      and the combination of signs of the operands.  */
-  if (TREE_OVERFLOW (res)
+  else if (TREE_OVERFLOW (res)
 	   && !TREE_OVERFLOW (val1)
 	   && !TREE_OVERFLOW (val2))
     {