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re PR tree-optimization/27364 (VRP miscompiles some unsigned math)

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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.

From-SVN: r113481
This commit is contained in:
Jeff Law 2006-05-02 13:54:20 -06:00 • committed by Jeff Law
parent e6cbdf26b4
commit 26ef43017a
4 changed files with 47 additions and 1 deletions
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6
gcc/ChangeLog
View file

@ -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.

5
gcc/testsuite/ChangeLog
View file

@ -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

13
gcc/testsuite/gcc.c-torture/execute/pr27364.c Normal file
View file

@ -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);
}

24
gcc/tree-vrp.c
View file

@ -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)