what local variables have been accessed at least once?
Stores that clobber previous stores to array or ref locals.
collect reaching definitions and initial useful instructions for this method.
Use-def chain: give the reaching definitions at the beginning of given instruction.
Map instructions who have a drop on some control path, to that DROP instruction.
Finds and marks all clobbers of the given local starting in the given basic block at the given index
Map from a local and a basic block to the instructions that store to that local in that basic block
Mark useful instructions.
the current method.
what instructions have been marked as useful?
Useful instructions which have not been scanned yet.