Method setDef

chapter21/src/main/java/com/seaofnodes/simple/node/Node.java:165–184

Change a def into a Node. Keeps the edges correct, by removing the corresponding use->def edge. This may make the original def go dead. This function is co-recursive with #kill. This method is the normal path for altering a Node, because it does the proper d

(int idx, N new_def )

     *
     * @param new_def the new definition, appended to the end of existing definitions
     * @return new_def for flow coding
     */
    public Node addDef(Node new_def) {
        unlock();
        // Add use->def edge
        _inputs.add(new_def);
        // If new def is not null, add the corresponding def->use edge
        if( new_def != null )
            new_def.addUse(this);
        return new_def;
    }

    // Breaks the edge invariants, used temporarily
    protected <N extends Node> void addUse(N n) { _outputs.add(n); }

    // Remove node 'use' from 'def's (i.e. our) output list, by compressing the list in-place.
    // Return true if the output list is empty afterward.
    // Error is 'use' does not exist; ok for 'use' to be null.
    protected boolean delUse( Node use ) {
        _outputs.del(_outputs.find(use));
        moveDepsToWorklist(); // User-count and anti-dependence queries can now change.
        return _outputs.isEmpty();
    }