PR tree-optimization/27364

[pf3gnuchains/gcc-fork.git] / gcc / tree-vrp.c

diff --git a/gcc/tree-vrp.c b/gcc/tree-vrp.c
index 7c6fe6e..d487df6 100644 (file)
--- a/gcc/tree-vrp.c
+++ b/gcc/tree-vrp.c
@@ -1191,17 +1191,39 @@ vrp_int_const_binop (enum tree_code code, tree val1, tree val2)
   if (TYPE_UNSIGNED (TREE_TYPE (val1)))
     {
       int checkz = compare_values (res, val1);
+      bool overflow = false;
 
       /* Ensure that res = val1 [+*] val2 >= val1
          or that res = val1 - val2 <= val1.  */
-      if (((code == PLUS_EXPR || code == MULT_EXPR)
+      if ((code == PLUS_EXPR
           && !(checkz == 1 || checkz == 0))
           || (code == MINUS_EXPR
              && !(checkz == 0 || checkz == -1)))
        {
+         overflow = true;
+       }
+      /* Checking for multiplication overflow is done by dividing the
+        output of the multiplication by the first input of the
+        multiplication.  If the result of that division operation is
+        not equal to the second input of the multiplication, then the
+        multiplication overflowed.  */
+      else if (code == MULT_EXPR && !integer_zerop (val1))
+       {
+         tree tmp = int_const_binop (TRUNC_DIV_EXPR,
+                                     TYPE_MAX_VALUE (TREE_TYPE (val1)),
+                                     val1, 0);
+         int check = compare_values (tmp, val2);
+
+         if (check != 0)
+           overflow = true;
+       }
+
+      if (overflow)
+       {
          res = copy_node (res);
          TREE_OVERFLOW (res) = 1;
        }
+
     }
   else if (TREE_OVERFLOW (res)
           && !TREE_OVERFLOW (val1)