In the pseudocode of Figure A.5 code fragments
are written as Java-like strings of program text (with
+ as the
concatenation operator). In the practical implementation these are
manipulated as nodes in an
abstract syntax tree.
Access sets will probably be implemented as two separate variable sets: the set of uses and the set of defs. A straightforward (possibly inefficient) approach is to implement each of these two sets using five components:
We consider two access sets to be dependent if they share a common variable (or category of variables), and at least one of the accesses is a def.
To complete the simplify algorithm we still need to define, for each kind of expression in the language, the relevant set of subexpressions (enumerated in the foreach), and also--for dependence analysis within expressions--the ``direct accesses associated with'' this kind of expression.