https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114779
--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
But in that case the POINTER_TYPE_P case doesn't trigger, because it is
INTEGER_CST and
so
/* If we know this is a constant, emit the constant of one. */
if (CONSTANT_CLASS_P (arg)
|| (TREE_CODE (arg) == CONSTRUCTOR
&& TREE_CONSTANT (arg)))
return integer_one_node;
triggers first.
There is another case where the builtin can return true for a pointer, and that
is
when it is called with a string literal (__builtin_constant_p ("abcd")):
if (TREE_CODE (arg) == ADDR_EXPR)
{
tree op = TREE_OPERAND (arg, 0);
if (TREE_CODE (op) == STRING_CST
|| (TREE_CODE (op) == ARRAY_REF
&& integer_zerop (TREE_OPERAND (op, 1))
&& TREE_CODE (TREE_OPERAND (op, 0)) == STRING_CST))
return integer_one_node;
}
But if you use even in the same function
int volatile *psfr = SFR;
__builtin_constant_p (psfr)
it will fold to 0.
