Code Generation

Register Descriptors

A register descriptor is a container depicting that all registers are empty in their initial states.

It contains complete information about each track of the register.

Also See, Top Down Parsing

Algorithm

The algorithm follows a queue of three address statements. The address statements are of form x: y op z simulates specific tasks.

The task description is given with the help of the following algorithm:

1. The initial step is to invoke a function getreg to capture the location L where the optimization of y op z is stored.
2. Manage the descriptive address of b to determine b'. If the value of b is present in memory and registers both, then the value of b' will be considered. If there is the absence of a value of b in L, then there is a need to generate the instruction MOV b', to copy a value of b in L.
3. A new instruction OP c' is to be generated. Updation of address descriptor of a takes place to depict that a is stored in L. If a is already present in L, then update the descriptor and remove a from all other descriptors.
4. After reaching the stage where b or c have no further uses, alter the register description. Now, the register will not store the values of b, and c.

Also read About, Specifications of Tokens in Compiler Design

Generating Code

The given assignment statement w:= (x-y) + (x-z) + (x-z) can be depicted into the queue of three address codes:
 

a:= x-y @  b:= x-z  @  c:= a+b   @  w:= b+c 

Code Sequence for the above problem is given as:

Frequently Asked Questions

Define Code Generator in compiler design.

Code Generator determines the values that are to be stored in the registers.

What is the final output received after code generation?

Machine code is the final output received after code generation.

Name the technique used for allocating registers efficiently.

Linear Scan Algorithm

In how many ways can a graph be colored in compiler design?

Every planar graph can be colored in four different ways.

What is the need for multiple passes?

Multiple passes provide better quality code generation.

Conclusion

Congratulations on finishing the blog!! After reading this blog, you will grasp the concept of Code Generation.

Recommended Reading:

• Top Down Parsing and Bottom Up Parsing
• First and Follow in Compiler Design
• Run-Time Environments
• Design Issues in Code Generator
• Basic Blocks in Compiler Design
• Backpatching In Compiler Design
• Basic Block In Compiler Design
• Input Buffering in Compiler Design
   

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