Compiler Design and Construction - Old Questions

9.  What is operation of simple code generator? Explain.

The final phase in compiler model is the code generator. It takes as input an intermediate representation of the source program and produces as output an equivalent target program.

        Fig: Position of code generator

A simple code generator generates target code for a sequence of three- address statements and effectively uses registers to store operands of the statements. For example: consider the three-address statement a := b+c It can have the following sequence of codes:

ADD R_j, R_i     Cost = 1    // if R_i contains b and R_j contains c

(or)

ADD c, R_i     Cost = 2    // if c is in a memory location

(or)

MOV c, R_j     Cost = 3    // move c from memory to R_j and add

ADD R_j, R_i