Three Address code generator

• It is a step in intermediate code generation phase of the compiler
• The purpose of the ICG is to provide platform-independent representation of the SC
• Three address code is common form of intermediate representation.
• It allows for machine independent code optimization between high level and SC and lowlevel Machine code
• Optimizations can be applied without needing to know the specifics of the target machien
• Done by breaking down complex instructions and expressions into a sequence of elementary operations
• Each instruction of 3AC involves ATMOST 3 addresses
• two for operands and one for result

quadruples:

• each instruction is represented by 4 fields:
• an operator, two operands and one result field

Triplets:

• triplets are similar to quads but omit result field
• reduces compelexit

Indirect Triplets:

• use a list of pointers that point to the triplets.
• better because easier rearrangement of code during OPT as you only need to reaggange the pointers rather than the triplets themselves