Intermediate Code Generation

Back to Compiler Design
Arjit Sharma
01 Min

What Is Intermediate Code?

Once the compiler has understood your code (via syntax and semantics), it converts it into an intermediate representation (IR), a form that is not machine code yet, but close enough to be easily translated into it later.

Think of it as a machine-neutral version of your program.

Example (from a = b + c * d;):

  • Intermediate Code:

    t1 = c * d
t2 = b + t1
a = t2

Why Do We Need IR?

  1. Portability - The same frontend (parser, analyzer) can target multiple machines via different backends.
  2. Optimization - Easier to perform code improvements on IR before generating final machine code.
  3. Simplicity - Abstracts away hardware-level details for now.

Common IR Forms

  • Three-address code (TAC) - Each instruction has at most three operands. Widely used.
  • Control Flow Graphs (CFGs) - Show how control moves between code blocks.
  • Static Single Assignment (SSA) - Every variable is assigned exactly once;

Conclusion

  • Intermediate Code bridges semantic understanding and machine execution
  • Makes code portable, optimizable, and easier to analyze
  • Forms like three-address code are widely used
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