re PR tree-optimization/26180 (wrong code due to VRP and unsigned multiplies with wraps)

	PR 26180
	* tree-vrp.c (vrp_int_const_binop): Detect overflow when
	multiplying unsigned values.
	Tidy comments.

testsuite

	PR 26180
	* gcc.dg/tree-ssa/pr26180.c: New test.

From-SVN: r110794

gcc/ChangeLog

+2006-02-09  Diego Novillo  <dnovillo@redhat.com>
+
+	PR 26180
+	* tree-vrp.c (vrp_int_const_binop): Detect overflow when
+	multiplying unsigned values.
+	Tidy comments.
+
 2006-02-09  Eric Botcazou  <ebotcazou@libertysurf.fr>
 
 	* config/sparc/sparc.c (tls_call_delay): Fix oversight.

gcc/testsuite/ChangeLog

+2006-02-09  Diego Novillo  <dnovillo@redhat.com>
+
+	PR 26180
+	* gcc.dg/tree-ssa/pr26180.c: New test.
+
 2006-02-08  Jeff Law  <law@redhat.com>
 
 	* gcc.dg/tree-ssa/pr21417.c: New test.

gcc/testsuite/gcc.dg/tree-ssa/pr26180.c

+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+void abort(void);
+int bar(int x, int y)
+{
+    int x1, y1;
+    int x2, y2;
+    unsigned int x3, y3, w;
+    int z = 1;
+
+    x1 = (x < (1 << 30));
+    y1 = (y < (1 << 30));
+    if (x1)
+    if (y1) {
+        x2 = ((x > 0)? (x): -(x));
+        y2 = ((y > 0)? (y): -(y));
+
+        x3 = x2;
+        y3 = y2;
+        w = x3 * y3;
+
+        if (w >= (1 << 30)) {
+          z = 1;
+        } else    {
+          z = -1;
+        }
+    }
+
+        return z;
+}
+
+
+int main()
+{
+  int x, y, z;
+  x = 536870912;  /* 2^29 */
+  y = 2;
+  z = bar(x, y);
+  if (z != 1)
+    abort ();
+  return 0;
+}

gcc/tree-vrp.c

@@ -1191,22 +1191,24 @@ vrp_int_const_binop (enum tree_code code, tree val1, tree val2)
     {
       int checkz = compare_values (res, val1);
 
-      /* Ensure that res = val1 + val2 >= 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)))
+      if (((code == PLUS_EXPR || code == MULT_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.  */
   else if (TREE_OVERFLOW (res)
 	   && !TREE_OVERFLOW (val1)
 	   && !TREE_OVERFLOW (val2))
     {
+      /* 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.  */
       int sgn1 = tree_int_cst_sgn (val1);
       int sgn2 = tree_int_cst_sgn (val2);