Compiler Design and Construction - Old Questions

10.  Why optimization is often required in the code generated by simple code generator? Explain the unreachable code optimization.

Code optimization is used to improve the intermediate code so that the output of the program could run faster and takes less space. It removes the unnecessary lines of the code and arranges the sequence of statements in order to speed up the program execution without wasting resources. It tries to improve the code by making it consume less resources (i.e. CPU, Memory) and deliver high speed.

Optimization is required in the code generated by simple code generator due to the following reasons:

• Code optimization enhances the portability of the compiler to the target processor.
• Code optimization allows consumption of fewer resources (i.e. CPU, Memory).
• Optimized code has faster execution speed.
• Optimized code utilizes the memory efficiently.
• Optimized code gives better performance.
• Optimized code often promotes re-usability.

Unreachable code optimization

The unreachable code is a part of the source code that will never be executed due to inappropriate exit points/control flow.. By eliminating these useless things from a code, the code will get optimized. For e.g.

An unlabeled instruction immediately following an unconditional jump can be removed. For e.g.