A C ?: expression is converted into an if statement with
each branch assigning to the same temporary. So,
a = b ? c : d;
becomes
if (b == 1)
T1 = c;
else
T1 = d;
a = T1;
The GIMPLE level if-conversion pass re-introduces ?:
expression, if appropriate. It is used to vectorize loops with
conditions using vector conditional operations.
Note that in GIMPLE, if statements are represented using
GIMPLE_COND, as described below.