https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110287
--- Comment #9 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
This is _M_realloc insert at release_ssa time:
eleased 63 names, 165.79%, removed 63 holes
void std::vector<pair_t>::_M_realloc_insert<const pair_t&> (struct vector *
const this, struct iterator __position, const struct pair_t & __args#0)
{
struct pair_t * const __position;
struct pair_t * __new_finish;
struct pair_t * __old_finish;
struct pair_t * __old_start;
long unsigned int _1;
struct pair_t * _2;
struct pair_t * _3;
long int _4;
long unsigned int _5;
struct pair_t * _6;
const size_type _10;
long int _13;
struct pair_t * iftmp.5_15;
struct pair_t * _17;
struct _Vector_impl * _18;
long unsigned int _22;
long int _23;
long unsigned int _24;
long unsigned int _25;
struct pair_t * _26;
long unsigned int _36;
<bb 2> [local count: 1073741824]:
__position_27 = MEM[(struct __normal_iterator *)&__position];
_10 = std::vector<pair_t>::_M_check_len (this_8(D), 1,
"vector::_M_realloc_insert");
__old_start_11 = this_8(D)->D.25975._M_impl.D.25282._M_start;
__old_finish_12 = this_8(D)->D.25975._M_impl.D.25282._M_finish;
_13 = __position_27 - __old_start_11;
if (_10 != 0)
goto <bb 3>; [54.67%]
else
goto <bb 4>; [45.33%]
<bb 3> [local count: 587014656]:
_18 = &MEM[(struct _Vector_base *)this_8(D)]._M_impl;
_17 = std::__new_allocator<pair_t>::allocate (_18, _10, 0B);
<bb 4> [local count: 1073741824]:
# iftmp.5_15 = PHI <0B(2), _17(3)>
_1 = (long unsigned int) _13;
_2 = iftmp.5_15 + _1;
*_2 = *__args#0_14(D);
if (_13 > 0)
goto <bb 5>; [41.48%]
else
goto <bb 6>; [58.52%]
<bb 5> [local count: 445388112]:
__builtin_memmove (iftmp.5_15, __old_start_11, _1);
<bb 6> [local count: 1073741824]:
_36 = _1 + 8;
__new_finish_16 = iftmp.5_15 + _36;
_23 = __old_finish_12 - __position_27;
if (_23 > 0)
goto <bb 7>; [41.48%]
else
goto <bb 8>; [58.52%]
<bb 7> [local count: 445388112]:
_24 = (long unsigned int) _23;
__builtin_memcpy (__new_finish_16, __position_27, _24);
<bb 8> [local count: 1073741824]:
_25 = (long unsigned int) _23;
_26 = __new_finish_16 + _25;
_3 = this_8(D)->D.25975._M_impl.D.25282._M_end_of_storage;
_4 = _3 - __old_start_11;
if (__old_start_11 != 0B)
goto <bb 9>; [53.47%]
else
goto <bb 10>; [46.53%]
<bb 9> [local count: 574129752]:
_22 = (long unsigned int) _4;
operator delete (__old_start_11, _22);
<bb 10> [local count: 1073741824]:
this_8(D)->D.25975._M_impl.D.25282._M_start = iftmp.5_15;
this_8(D)->D.25975._M_impl.D.25282._M_finish = _26;
_5 = _10 * 8;
_6 = iftmp.5_15 + _5;
this_8(D)->D.25975._M_impl.D.25282._M_end_of_storage = _6;
return;
}
First it is not clear to me why we need memmove at all?
So first issue is:
<bb 2> [local count: 1073741824]:
__position_27 = MEM[(struct __normal_iterator *)&__position];
_10 = std::vector<pair_t>::_M_check_len (this_8(D), 1,
"vector::_M_realloc_insert");
__old_start_11 = this_8(D)->D.25975._M_impl.D.25282._M_start;
__old_finish_12 = this_8(D)->D.25975._M_impl.D.25282._M_finish;
_13 = __position_27 - __old_start_11;
if (_10 != 0)
goto <bb 3>; [54.67%]
else
goto <bb 4>; [45.33%]
Without inlining _M_check_len early we can not work out return value range,
since we need to know that paramter 2 is 1 and not 0.
Adding __builtin_unreachable check after helps to reduce
if (_10 != 0)
but I need to do something about inliner accounting the conditional to function
body size.
<bb 4> [local count: 1073741824]:
# iftmp.5_15 = PHI <0B(2), _17(3)>
_1 = (long unsigned int) _13;
_2 = iftmp.5_15 + _1;
*_2 = *__args#0_14(D);
if (_13 > 0)
goto <bb 5>; [41.48%]
else
goto <bb 6>; [58.52%]
<bb 5> [local count: 445388112]:
__builtin_memmove (iftmp.5_15, __old_start_11, _1);
Is this code about inserting value to the middle? Since push_back always
initializes iterator to point to the end, this seems quite sily to do.
Can't we do somehting like _M_realloc_append?
