Method delDef

chapter07/src/main/java/com/seaofnodes/simple/node/Node.java:200–206

(int idx)

    // shuffles the order deterministically - which is suitable for Region and
    // Phi, but not for every Node.
    void delDef(int idx) {
        Node old_def = in(idx);
        if( old_def != null &&  // If the old def exists, remove a def->use edge
            old_def.delUse(this) ) // If we removed the last use, the old def is now dead
            old_def.kill();     // Kill old def
        Utils.del(_inputs, idx);
    }

    /**
     * Add a new def to an existing Node.  Keep the edges correct by