Currently we generate an if with probability set on only one of the two edges:
<bb 5> [0.00%] [count: INV]:
_5 = mask.3[iter.6_3];
if (_5 == 0)
goto <bb 6>; [INV] [count: INV]
else
goto <bb 2>; [100.00%] [count: INV]
Add the missing edge probability, and set the split to unlikely/likely:
if (_5 == 0)
goto <bb 6>; [19.99%] [count: INV]
else
goto <bb 2>; [80.01%] [count: INV]