CFGs, we open the door to neat optimizations ! * dead code elimination * splitting polymorphic functions into multiple monomorphic functions * extreme minification * generating SSA graphs (like V8's Crankshaft!)
also do some neat mad-science-y stuff: ! * diffing CFGs — did that commit add a new exception edge to the program? * taint checking * if the IR is advanced enough, we could project JS into different languages.
(really answered): ! no* operators are safe. ! it's only combinations of operators and operand types that are safe. ! * except for void but hey, it's kind of difficult to write a useful program with just void