1. Compiler design Review COMP 442/6421 – Compiler Design
Joey Paquet,

2. COMP 442/6421 – Compiler Design
Examination
Objective: to verify that the students grasp the theoretical aspects of compiler design, as taught in class.
Duration: 180 minutes.
Examination can be either of the following, which will be announced during the last week of classes:
Open-book examination: all course notes, any textbook, or paper documents are allowed during the examination, no electronic device permitted.
Student’s cheat-sheet examination: each student is allowed to bring one 8.5x11in page (double-sided) cheat-sheet of their own design at the examination. Can be either/both printed or hand-written.
Professor’s cheat-sheet examination: the professor provides one 8.5x11in page (double-sided) cheat-sheet, which is handed out two weeks prior to the examination. The cheat sheet will be printed as part of the examination questionnaire.
Closed-book examination: No material or cheat sheet of any kind is allowed or provided during the examination.
Joey Paquet,

3. Course review Compiler architecture Phases: Front-end, back-end
COMP 442/6421 – Compiler Design
Course review
Compiler architecture
Phases:
lexical analysis
syntactic analysis
semantic analysis
code optimization
code generation
Front-end, back-end
Intermediate representations
Mechanisms:
parsing tables
symbol table
semantic actions/semantic records
attribute migration
Functioning/role of each phase/component/mechanisms
Optionality of some phases
Joey Paquet,

4. Course review Lexical analysis Roles Design Implementation
COMP 442/6421 – Compiler Design
Course review
Lexical analysis
Roles
White space removal
Processing comments
Check and recover from lexical errors
Creation of a stream of tokens
Design
Translation of regular expression into a DFA
Thompson construction
Rabin–Scott power set construction
Implementation
Case statement or state transition table/algorithm
Notable examination questions
Generate a DFA from regular expressions (Thompson’s construction)
Generate a DFA from NDFA (Rabin-Scott power set construction)
Joey Paquet,

5. Course review Syntactic analysis Roles Design
COMP 442/6421 – Compiler Design
Course review
Syntactic analysis
Roles
Analyze the program’s structure
Check, report and recover from syntax errors leading to useful and comprehensive compiler output
Design
Generative context-free grammars, generating a derivation proving the validity of the input program according to the grammar
First and follow sets
Grammar transformation (removal of left recursions, ambiguities)
All designs are based on a stack mechanism
Top-down: predictive parsing, recursive descent, table-driven (require removal of left recursions, ambiguities)
Bottom-up: SLR, CLR, LALR (item generation)
Error recovery using “synchronizing tokens”
AST generation as intermediate representation
Attribute migration, semantic stack
Joey Paquet,

6. Course review Syntactic analysis (cont.) Implementation
COMP 442/6421 – Compiler Design
Course review
Syntactic analysis (cont.)
Implementation
Recursive descent top-down: each production is implemented as a function matching terminals and calling other such functions to parse non-terminals according to other rules
Table-driven top-down: table is constructed using the first and follow sets, based on the notion of “generative grammar”
Bottom-up: SLR, CLR, LALR: creation of a DFA using items and first and follow sets, creation of the state transition table with “action” and “goto” parts, called a “shift/reduce” parser.
Notable examination questions
Given a grammar, generate a table for a table-driven top-down predictive parser
Given a grammar, write some functions for a recursive-descent predictive parser
Given a grammar, eliminate left recursions and ambiguities
Given a grammar and a valid sentence, provide a derivation proving that this sentence is derivable from the grammar
Given a grammar, generate the sets of (CLR, SLR, LALR) items, then generate the corresponding state transition table and/or state transition diagram
Given a state transition table and a token stream, execute a parse trace for any of the above bottom-up parsing techniques
Joey Paquet,

7. Course review Semantic Analysis/translation Roles Design
COMP 442/6421 – Compiler Design
Course review
Semantic Analysis/translation
Roles
Verify the semantic validity of the program
Translate the program into executable code
Design
Symbol table
Intermediate representations (optional)
Optimization, high level and/or low level (optional)
Semantic actions and semantic records
AST traversal and the Visitor design pattern
Joey Paquet,

8. Course review Semantic Analysis/translation (cont.) Implementation
COMP 442/6421 – Compiler Design
Course review
Semantic Analysis/translation (cont.)
Implementation
Symbol table: nested tables to manage scoping
Intermediate representation: trees, directed acyclic graphs, tree traversal/analysis algorithms for further processing
Intermediate code: postfix notation, three-address code, quadruples, pcode, byte code
Notable examination questions
Given a program, sketch its corresponding symbol table structure.
Given a simple statement/expression write the corresponding Moon code translation.
Joey Paquet,