https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105751
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2022-05-30
Status|UNCONFIRMED |NEW
Ever confirmed|0 |1
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed. We end up expanding
<bb 2> [local count: 1073741824]:
_5 = a_2(D) + 8;
_6 = &MEM[(const struct array *)a_2(D)]._M_elems;
_8 = _5 - _6;
__len_9 = (const size_t) _8;
if (__len_9 != 0)
goto <bb 3>; [50.00%]
else
goto <bb 4>; [50.00%]
<bb 3> [local count: 536870913]:
_4 = &MEM[(const struct array *)b_3(D)]._M_elems;
_10 = __builtin_memcmp_eq (_6, _4, __len_9);
_11 = _10 == 0;
<bb 4> [local count: 1073741824]:
# _12 = PHI <1(2), _11(3)>
return _12;
So somehow the size is not known to be 8 and thus the proposed optimized code
would compare uninitialized memory?
