PR tree-optimization/27364

	* tree-vrp.c (vrp_int_const_binop): Fix detection of overflow from
	multiply expressions.

	* gcc.c-torture/execute/pr27364.c: New test.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@113481 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 378be12..28e2616 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2006-05-02  Jeff Law  <law@redhat.com>
+
+       PR tree-optimization/27364
+       * tree-vrp.c (vrp_int_const_binop): Fix detection of overflow from
+       multiply expressions.
+
 2006-05-02  Tom Tromey  <tromey@redhat.com>
 
        * tree-flow-inline.h (op_iter_init_phiuse): Fixed typo.

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 9608839..2a654bc 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2006-05-02  Jeff Law  <law@redhat.com>
+
+       PR tree-optimization/27364
+       * gcc.c-torture/execute/pr27364.c: New test.
+
 2006-05-02  Mark Mitchell  <mark@codesourcery.com>
 
        PR c++/27309

diff --git a/gcc/testsuite/gcc.c-torture/execute/pr27364.c b/gcc/testsuite/gcc.c-torture/execute/pr27364.c
new file mode 100644 (file)
index 0000000..aa608b2
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr27364.c
@@ -0,0 +1,13 @@
+int f(unsigned number_of_digits_to_use)
+{
+  if (number_of_digits_to_use >1294)
+    return 0;
+  return (number_of_digits_to_use * 3321928 / 1000000 + 1) /16;
+}
+
+int main(void)
+{
+  if (f(11) != 2)
+    __builtin_abort ();
+  exit (0);
+}

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)