Variable Propagation in Code Optimization

Q.1: Why compiler uses Variable propagation in compilation process?

Answer:

Compiler uses variable propagation step in code optimization because this analysis can provide the optimizer to optimize the code which results in

1. Elimination of redundant variables: Sometimes in our code, the variables can be can be replaced by other variables which can reduce the usage of new variables, thus leading to the elimination of pointless variables.

2. Elimination of Dead Code: Eliminating dead code in the code reduces unnecessary computations and memory usage.

3. Improving Resource efficiency: By using less no. of variables and memory, we are able to improve the efficiency of our code in utilizing the memory and C.P.U resources.

Q.2: Difference between Constant Propagation and Variable Propagation?

Answer:

Constant propagation is a optimization technique where we replace the variables with the known constants, where as in variable propagation, we just analyze the code and this analyzation helps the optimizer to know which code to replace, which code to eliminate etc..

Q.3: When does variable propagation step takes place?

Answer:

Right after the Generation of Intermediate code, The analysis of Intermediate code generation takes place and after this, code optimization takes place.

Q.4: Will variable propagation step modifies the code?

Answer:

No, the variable propagation directly does not modify the code any, but it will help the optimizer to modify the code.

Q.5: Will modifying the code by optimization changes the functionality?

Answer:

No, The optimization takes place such that it modifies the code and improves the efficiency of code in terms of memory and speed without changing the core functionality of the code.

In the compilation process, after generating the Intermediate code, the Compiler does code optimization to improve the performance of the code. So, before actually modifying the code for optimization, the compiler analyses the flow of variables in the code, that is compiler analyzes the code and variables, and based upon this analysis, the optimizer component of the compiler does code optimization. This analysis of the flow of variables throughout the code by the compiler is called variable propagation.