https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126896
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Last reconfirmed| |2026-08-17
Status|UNCONFIRMED |NEW
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
To clarify, DOM turns
<bb 2> [local count: 1073741824]:
if (x_3(D) != 0)
goto <bb 3>; [50.00%]
else
goto <bb 4>; [50.00%]
<bb 3> [local count: 536870912]:
t_9 = a_7(D) < b_8(D);
goto <bb 5>; [100.00%]
<bb 4> [local count: 536870912]:
t_6 = c_4(D) < d_5(D);
<bb 5> [local count: 1073741824]:
# t_1 = PHI <t_9(3), t_6(4)>
if (t_1 != 0)
goto <bb 6>; [33.00%]
else
goto <bb 7>; [67.00%]
<bb 6> [local count: 354334800]:
g ();
<bb 7> [local count: 1073741824]:
return;
into
<bb 2> [local count: 1073741824]:
if (x_3(D) != 0)
goto <bb 3>; [50.00%]
else
goto <bb 4>; [50.00%]
<bb 3> [local count: 536870912]:
t_9 = a_7(D) < b_8(D);
if (t_9 != 0)
goto <bb 5>; [0.00%]
else
goto <bb 6>; [100.00%]
<bb 4> [local count: 536870912]:
t_6 = c_4(D) < d_5(D);
if (t_6 != 0)
goto <bb 5>; [66.00%]
else
goto <bb 6>; [34.00%]
<bb 5> [local count: 354334800]:
g ();
<bb 6> [local count: 1073741824]:
return;
This isn't jump threading. It looks more like sth for phiopt or tail
duplication?
t_9 = a_7(D) < b_8(D);
..
t_6 = c_4(D) < d_5(D);
..
# t_1 = PHI <t_9, t_6>
if (t_1 != 0)
I suspect there's some odd special case code in DOM to register this as
"jump thread" just to get the if (t != 0) block duplicated.
