Method kill

chapter19/src/main/java/com/seaofnodes/simple/node/Node.java:251–263

Kill a Node with no uses , by setting all of its defs to null. This may recursively kill more Nodes, and is basically dead code elimination.

( )

     * code elimination.
     */
    public void kill( ) {
        unlock();
        moveDepsToWorklist();
        assert isUnused();      // Has no uses, so it is dead
        _type=null;             // Flag as dead
        while( nIns()>0 ) { // Set all inputs to null, recursively killing unused Nodes
            Node old_def = _inputs.removeLast();
            // Revisit neighbor because removed use
            if( old_def != null && CODE.add(old_def).delUse(this) )
                old_def.kill(); // If we removed the last use, the old def is now dead
        }
        assert isDead();        // Really dead now
    }

    // Mostly used for asserts and printing.
    public boolean isDead() { return isUnused() && nIns()==0 && _type==null; }