http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52578
Bug #: 52578
Summary: Fails to fold another size difference
Classification: Unclassified
Product: gcc
Version: 4.7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
AssignedTo: [email protected]
ReportedBy: [email protected]
gnat.dg/opt9.adb will fail with the bitfield handling patch with -m32 because
we do not fold
long bar (long i)
{
return (long)((unsigned long)i + 2) - (long)i;
}
long foo (int i)
{
return (long)((unsigned long)i + 2) - (long)i;
}
to constants. the associate: path splits the above to
var0 == (long unsigned int) i, lit0 == 2, var1 == -i
which fails to associate because of
/* With undefined overflow we can only associate constants with one
variable, and constants whose association doesn't overflow. */
if ((POINTER_TYPE_P (type) && POINTER_TYPE_OVERFLOW_UNDEFINED)
|| (INTEGRAL_TYPE_P (type) && !TYPE_OVERFLOW_WRAPS (type)))
{
if (var0 && var1)
{
tree tmp0 = var0;
tree tmp1 = var1;
if (TREE_CODE (tmp0) == NEGATE_EXPR)
tmp0 = TREE_OPERAND (tmp0, 0);
if (TREE_CODE (tmp1) == NEGATE_EXPR)
tmp1 = TREE_OPERAND (tmp1, 0);
/* The only case we can still associate with two variables
is if they are the same, modulo negation. */
if (!operand_equal_p (tmp0, tmp1, 0))
ok = false;
but we can as well strip widening and sign-changing conversions I think.
