Javadoc
Is this instruction a "beginning instruction". A beginning instruction is defined to be an instruction
that can be the first successfully executed instruction in the method. The first instruction is always a
beginning instruction. If the first instruction can throw an exception, and is covered by a try block, then
the first instruction of any exception handler for that try block is also a beginning instruction. And likewise,
if any of those instructions can throw an exception and are covered by try blocks, the first instruction of the
corresponding exception handler is a beginning instruction, etc.
To determine this, we simply check if the first predecessor is the fake "StartOfMethod" instruction, which has
an instruction index of -1.