CSCE 531 Compiler Construction Final Lecture of the Semester

1
CSCE 531Compiler ConstructionFinal Lecture of
the Semester

• Spring 2008
• Marco Valtorta
• mgv_at_cse.sc.edu

2
Acknowledgment

• The slides are based on the textbook and other
  sources, including slides from Bent Thomsens
  course at the University of Aalborg in Denmark
  and several other fine textbooks
• The three main other compiler textbooks I
  considered are
• Aho, Alfred V., Monica S. Lam, Ravi Sethi, and
  Jeffrey D. Ullman. Compilers Principles,
  Techniques, Tools, 2nd ed. Addison-Welsey,
  2007. (The dragon book)
• Appel, Andrew W. Modern Compiler Implementation
  in Java, 2nd ed. Cambridge, 2002. (Editions in
  ML and C also available the tiger books)
• Grune, Dick, Henri E. Bal, Ceriel J.H. Jacobs,
  and Koen G. Langendoen. Modern Compiler Design.
  Wiley, 2000

3
Efficiency

• Efficiency is especially an issue for register
  machines
• Example 9.5
• Hand-developed assembly code is faster
• Code transformations (optimizations)
• Constant folding, including address folding for
  arrays and records (ex. 9.6)
• Common expression elimination (ex. 9.7)
• Code movement (ex. 9.8)

4
Blocks and Data Flow Analysis

• Handout (dragon books 9.4 1988)
• Partition into basic blocks
• Transformation on basic blocks
• Common subexpression elimination
• Dead code elimination
• Renaming of temporary variables
• Interchange of two independent adjacent
  statements
• Basic blocks form a flow graph

5
Live Variable Analysis

• Handout (dragon book 9.2.5 2007)
• Could variable x at point p be used along some
  path in the flow graph starting at p?

6
Language Lifecycle

• Language processors do not exist in a vacuum
• Waterfall, Iterative Development, RUDE
• Support for programming in the large and
  programming in the small is necessary
• This goes beyond compiler design
• Waterfall requires support for design-by-contract
• Iterative development requires support for
  prototyping
• RUDE may be better supported by weaker typing

7
Interpreters are everywhere on the web
Web-Client
Database Server
Web-Server
HTML-Form (JavaScript)
Call PHP interpreter
WWW
DBMS
Submit Data
LAN
PHP Script
Web-Browser
SQL commands
Response
Response
Database Output
Reply
8
Parallel Programming

• People still we do not know how to do parallel
  programming in an imperative style, and the
  machines are catching up!
• Solution 1 use a functional or logical style
• Solution 2 concentrate on numerical computation
• Solution 3 support specific computer
  architectures

9
Compilers, Language Design, and Specifications

• It is hard to write informal specifications that
  are unambiguous
• Example repeat until exercise
• It seems impossible to teach a compiler course
  without also teaching language design
• Example recursive data types

10
Why Study PL Concepts?

1. Increased capacity to express ideas
2. Improved background for choosing appropriate
   languages
3. Increased ability to learn new languages
4. Better understanding of the significance of
   implementation
5. Increased ability to design new languages
6. Background for compiler writing
7. Overall advancement of computing
8. Distinguish essential from accidental features