https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121909
Jan Hubicka <hubicka at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Last reconfirmed| |2025-09-11
Status|UNCONFIRMED |NEW
--- Comment #1 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
The problem is that last basic block has:
_7 = a;
and fnsplit considers only splitting where the split part leads directly to
return (which is kind of a limitation that can be avoided, too).
Hand optimizing it to:
int *a;
int *get()
{
int *aa = a;
if (!aa)
a = aa = new (int);
return aa;
}
Problem is that equivalent transformation is done only later by PRE
int * get ()
{
int * a.0_1;
void * _5;
int * prephitmp_8;
<bb 2> [local count: 1073741824]:
a.0_1 = a;
if (a.0_1 == 0B)
goto <bb 3>; [17.43%]
else
goto <bb 4>; [82.57%]
<bb 3> [local count: 187153200]:
_5 = operator new (4);
a = _5;
<bb 4> [local count: 1073741824]:
# prephitmp_8 = PHI <a.0_1(2), _5(3)>
return prephitmp_8;
}
I am not sure why FRE does not see it. Load in return is fully redundant.
