()
| 106 | * proper default edge maintenance. It also <em>immediately</em> kills |
| 107 | * Nodes that lose their last use; at times care must be taken to avoid |
| 108 | * killing Nodes that are being used without having an output Node. This |
| 109 | * definitely happens in the middle of recursive {@link #peephole} calls. |
| 110 | * |
| 111 | * @param idx which def to set |
| 112 | * @param new_def the new definition |
| 113 | * @return new_def for flow coding |