Quadruples Triples & Three-Address Code Structures

Lecture 37 of CS606 Compiler Construction investigates the internal software data structures used to represent Three-Address Code in memory. Students examine three standard structural representations: Quadruples, Triples, and Indirect Triples. A Quadruple is a 4-field record consisting of (op, arg1, arg2, result), explicitly storing the name of the result temporary variable. A Triple record eliminates the explicit result field, referring to the outcome of an operation by its index or pointer position in the instruction array; while Triples save memory, reordering instructions during optimization requires updating all dependent array references. An Indirect Triple solves this limitation by decoupling instruction storage from a separate array of pointers, allowing compiler optimization passes to move, delete, or insert instructions simply by rearranging pointer entries without mutating underlying data records. Key compiler optimization passes spanning loop invariant code motion, constant folding, and dead code elimination are systematically demystified. By engaging with solved past papers by Moaaz and Waqar Siddhu, learners gain actionable insights into recurrent university exam questions. Interactive quiz assessments on VU SIGMA facilitate rapid knowledge verification and retention of critical compiler engineering terminology. Comprehensive coverage of IEEE and ACM curricula standards ensures learners communicate with technical precision across global systems engineering teams. Detailed analysis of machine code selection highlights the imperative of generating instruction sequences that maximize hardware pipeline throughput. Intermediate representation taxonomy categorizes structural formats into graphical ASTs, linear tuples, and hybrid tree-address models. The strategic role of peephole optimization is evaluated as a final localized pass to eliminate redundant loads, stores, and jumps. In this lecture, students examine formal language translation principles and architectural compiler pipelines to understand automated code generation. Through detailed theoretical derivations and algorithmic walkthroughs, the lesson explores lexical tokenization, grammatical parse trees, and syntax trees. Special emphasis is placed on formal grammar transformations, eliminating left recursion, and establishing unambiguous predictive parsing tables. Mastering these foundational language translation frameworks empowers computer science scholars to design robust parsers, interpreters, and domain-specific languages.