You don't really need a pushx opcode.  If the "die" is in the scope of
a "catch", then you can directy jump to the handler.  Otherwise, you
unwind the stack until you arrive in the scope of a "catch".  In order
to know whether this is the case, you simply build a table at compile
time which associate to each possible return address a corresponding
handler (if any).  The advantage is that the cost of "catch" is null
when no exception is raised.  As a subroutine block is implicitely a
"catch" (it catches return exceptions), this may be interesting.

-- Jerome