Introduction to Compiler Construction in a Java World

162 An Introduction to Compiler Construction in a Java World

are more likely to be adding new syntax to j--, together with its functionality. Making

extensions to j-- would require our modifying each of the phases.

Moreover, often the traversal order for one node type differs from that of another. And

sometimes we want to perform actions at a node before, after, and even in between the

traversal of the sub-trees. For example, take a look at codegen() for the JIfStatement:

public void codegen ( CLEmitter o u tput ) {

String elseLabel = output . creat e L a bel ();

String endLabel = output . createLab e l ();

condition . codegen ( output , elseLabel ,