https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110287
Jan Hubicka <hubicka at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Ever confirmed|0 |1
Last reconfirmed| |2023-11-21
--- Comment #10 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
We now produce reasonable code for _M_check_len and propagate value range of
the return value. This helps us to notice that later allocator call will not
throw exception on invalid size, so we are down from 3 throw calls to one.
Current code is:
size_type std::vector<pair_t>::_M_check_len (const struct vector * const this,
size_type __n, const char * __s)
{
const size_type __len;
long unsigned int _1;
long unsigned int __n.3_2;
size_type iftmp.4_3;
long unsigned int _4;
long unsigned int _7;
long unsigned int _8;
long int _9;
long int _11;
struct pair_t * _12;
struct pair_t * _13;
<bb 2> [local count: 1073741824]:
_13 = this_6(D)->D.26060._M_impl.D.25361._M_finish;
_12 = this_6(D)->D.26060._M_impl.D.25361._M_start;
_11 = _13 - _12;
_9 = _11 /[ex] 8;
_7 = (long unsigned int) _9;
_1 = 1152921504606846975 - _7;
__n.3_2 = __n;
if (_1 < __n.3_2)
goto <bb 3>; [0.00%]
else
goto <bb 4>; [100.00%]
<bb 3> [count: 0]:
std::__throw_length_error (__s_14(D));
<bb 4> [local count: 1073741824]:
_8 = MAX_EXPR <__n.3_2, _7>;
__len_10 = _7 + _8;
if (_7 > __len_10)
goto <bb 6>; [35.00%]
else
goto <bb 5>; [65.00%]
<bb 5> [local count: 697932184]:
_4 = MIN_EXPR <__len_10, 1152921504606846975>;
<bb 6> [local count: 1073741824]:
# iftmp.4_3 = PHI <1152921504606846975(4), _4(5)>
return iftmp.4_3;
}
I still think we could play games with the 2^63 being too large for the
standard allocator and turn __throw_length_error into __builtin_unreachable for
that case. This would help early inliner to inline this function and save some
throw calls in real code.
