?: expression is converted into an
if statement with
each branch assigning to the same temporary. So,
a = b ? c : d;
if (b) T1 = c; else T1 = d; a = T1;
Tree 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 also represented using
COND_EXPR, as described below.