In compiler design, three-address code (TAC), also known as intermediate code (IC), plays a crucial role in code optimization. It's a simplified representation of the source code generated during the compilation process, serving as a bridge between the high-level source code and the low-level machine code.
Key Characteristics:
- Intermediate Representation: TAC acts as an intermediate stage between the original source code and the final machine code.
- Three Operands: Each TAC instruction typically involves at most three operands and one operator. These operands can be variables, constants, or temporary variables generated by the compiler.
- Assignment and Operation: The instruction format usually combines an assignment and a binary operation. The result of the operation is assigned to a specific operand.
Benefits of TAC:
- Optimization: TAC facilitates various code optimization techniques like constant propagation, dead code elimination, and common subexpression elimination. These optimizations improve the efficiency of the generated machine code.
- Target Independence: TAC is independent of the target machine architecture, allowing the compiler to focus on optimizing the logic without being constrained by specific machine instructions.
- Simplicity: TAC offers a relatively simple and easy-to-understand representation, aiding in debugging and analyzing the compilation process.
Common Forms of TAC Instructions:
t1 := a + b: This instruction adds the values ofaandband stores the result in temporary variablet1.t2 := t1 * c: This instruction multiplies the value int1withcand stores the result int2.if (t2 > 0) goto L1: This instruction performs a comparison and jumps to labelL1if the value int2is greater than 0.