Wednesday 5:00 - 7:00
Room 109, Warren Weaver Hall
Professor Robert Dewar

Instructor: Robert Dewar (
Teaching Assistant: Shubin Zhao (

Class list

All students should register themselves with the class list, which is used for all technical discussions concerning the course and the course project. To subscribe to this list visit the web page:

where you will find full directions.

Please send all your questions to this list (not to the instructor) so that everyone can participate.



Aho, Sethi and Ullman: Compilers, principles, Techniques and tools (Addison Wesley)

This is still the standard textbook, even though more than 10 years old. The following suggested readings touch on more recent topics, but the Dragon book still contains much information that every compiler writer should know.

Recommended readings:

Fraser and Hanson: a retargetable C compiler (Benjamin Cummings, 1996)
Muchnick: advanced compiler design and implementation (Morgan Kaufman, 1997)
Fisher & LeBlanc : Crafting a Compiler (Benjamin Cummings)
Appel : modern compiler implementation in C : basic techniques
Dewar & Smosna : Microprocessors, a programmer's perspective (Mc-Graw Hill)

GNAT Sources

Throughout the course we will be referring to the sources of the GNAT compiler, which will also be the basis of the course project. The compact overview of GNAT provides a roadmap to its main components. You can download GNAT for your favorite machine, and get the full sources of the compiler, from the NYU ftp site: ftp, directory pub/gnat. To build the compiler, you will need the sources for GCC 2.81.

You may also find it useful to browse the GNAT sources here. To download the entire set, grab, unzip it on your local machine, and point your browser to index.htm.

(Please report any broken cross references to

Ada, GNAT, and tool documentation:

Ada 95 reference manual.
The GNAT user's guide.
The GNAT reference manual.
GCC documentation.
GDB documentation.

All of the above are available for downloading in multiple formats from the NYU ftp site.

If Ada is new to you, you may want to start with this ada summary.

Assembly resources:

The Art of Assembly is a complete online text book covering x86 assembly programming.

For Linux / Unix information see Especially see the Linux Assembly HOWTO.

Complete x86 information is available from Intel:

Developer's Manual, Volume 1: Basic Architecture
Developer's Manual, Volume 2: Instruction Set.
Developer's Manual, Volume 3: System Programming Guide.

You may also find it useful to examine assembly generated by GCC from your own code. To do so, pass GCC the -S flag or the -save-temps flag. It's also straight forward to step through a program in GDB and use 'stepi' to watch the instructions being executed for each line.

Course Work

Semester project: write a prototype compiler for a Pascal subset of Ada, using the front-end of the GNAT compiler.
Various problem sets, and a final examination.

Final Exam

May 9th in class. Open book.
Exam guidelines.

Final Project

Compilers Final Project requirements and submission instructions.
A minimal test program.

Dead Lines

May 13th, midnight
Deadline for initial submission of final project.
May 20th, midnight
If and ONLY IF you have made an initial submission of the final project, you can submit an updated version with improvements etc by this deadline. The submission must clearly indicate what the changes are.

Lecture 1

Language translators: compilers and interpreters. The structure of a compiler: lexical analysis, parsing, semantic analysis, intermediate code generation, register allocation, global optimization. Bootstrapping a compiler. This is essentially an overview of what compilers are all about, and hence of the entire course

Readings: ASU chap. 1 and 2.

Lecture 2

A modern compiler : GNAT. The architecture of GNAT: phases, intermediate representations, important data structures.
How to build GNAT from sources. How to build modified versions of GNAT, tree-walking routines that use the intermediate representation of GNAT.

Readings: GNAT specifications for syntactic and entity information, the driver routines, interface to the GCC code generator.

an example tree-walking routine
example sources
syntax specification for GNAT AST
semantic information for entities in GNAT AST

Lecture 3

Lexical scanning: Token classes, fast keyword recognition, minimizing the code-per-character cost of scanning, scanning numeric literals and string literals. The interface between the scanner and the parser. Hand-written vs. automatically generated scanners. Regular expressions. Handling of constants

Readings: GNAT files,, scn.adb, scn-nlit.adb, scn-slit.adb, ASU sections 3.1 - 3.4 (rest of chapter optional)

The flex specifications
Lecture slides (or powerpoint)

Lecture 4

Parsing. Abstract syntax vs. concrete syntax. Grammars and the formal specification of certain aspects of programming languages. Top-down parsing and recursive descent. Error detection and recovery.

Readings: GNAT files , par.adb (the top level parsing routine), and its subunits. such as
par-ch3.adb (parsing of declarations),
par-ch4.adb (expressions),
par-ch5.adb (statements),
par-ch6.adb (subprograms),
par-ch7.adb (packages),
par-ch10.adb (compilation units),
and ASU sections 4.1-4.4

Lecture 5

Automatic parser construction. FIRST and FOLLOW functions. LL(1) parsers. LR parsers. Conflicts in LR grammars and how to resolve them. An introduction to BISON.

The Bison specifications.
Lecture slides (or powerpoint)

Readings: ASU sec. 4.7-4.9

GCC 2.81 uses Yacc/Bison for it's C and C++ parsers, which provide realistic examples. Some preprocessing is performed during the GCC build, consult those sources for further details.

Lecture 6

Code generation: quadruples, assembly language, machine language. Simple algorithms for register allocation. Formal specification of machine characteristics. Note: logically this would fit better later on in the course if we were tracing the action of a compiler from beginning to end, but we move this earlier to give you a jump start on the final project for the course. Readings: GCC docs, ASU chapter 9 An excellent GCC tutorial can be found at

Lecture 7

Run-time organization: storage allocation, non-local references, parameter passing, dynamic storage allocation. Exception handling, debugging information.

Readings: GNAT files sem_res, exp_ch4, exp_ch6, exp_ch11. ASU chapter 7.
Lecture slides (or powerpoint)

Lecture 8

Semantic analysis: attributes and their computation, tree-traversals, visibility and name resolution. Inherited attributes and symbol tables. Name resolution in block-structured languages.

Readings: GNAT files, X= 3 to 8 ASU sections 5.1 - 5.5,
Lecture slides

Lecture 9

Type checking. Type systems, varieties of strong typing, overload resolution, polymorphism and dynamic dispatching. Type-checking and type inference, unification.

Readings: GNAT files sem_res, sem_type, sem_disp. ASU chapter 6.

Lecture 10

Intermediate code generation: control structures, assignments, aggregates. Lowering the semantic abstraction of high-level constructs.

Readings: GNAT files exp_ch5, exp_aggr. ASU chapter 8.

Lecture 11

Code generation for RISC machines: pipelines, delay slots, instruction scheduling

Readings : Microprocessors, chap. ???

Lecture 12

Peephole optimization. Case study: the REALIA Cobol compiler.
Lecture slides (or StarOffice format)

Lecture 13

Last official class. April 25

Global optimization: data flow analysis, monotonic frameworks, use-def chaining, constant folding, common subexpression elimination.

Readings: ASU chapter 10, lecture notes.

Lecture 14

First exam week date. May 2nd

Special extra class. Guest lecturer by Dr. Ben Goldberg on advance loop optimization.

Final Exam

May 9th in class

Open book. Exam guidelines.