Compilers: Principles and Practice

10.3 Peep-hole Optimization

This kind of optimization is done by one or more passes over the entire IR, in a linear fashion. Such methods are called peep-hole optimization because it inspects and manipulates a small portion of the IR at a time, see Fig. 10.2. A peep-hole method:

 

 

Fig. 10.2 Peep-hole Optimization

 

• looks for certain patterns and replaces them with simpler, or more efficient ones;
• requires only small amount of additional memory for its functioning;
• is relatively small and fast;
• works best with 3-tuple and 4-tuple IR;
• a number of individual methods are available under the umbrella of peep-hole optimization.

We should note ...