Compiler Construction - Introduction and...

Compiler ConstructionIntroduction and overview

Gorel Hedin

Reviderad 2013-01-22

2013

Compiler Construction 2013 F01-1

Agenda

Course registration, structure, etc.

Course overview


Course registration

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Prerequisites

Object-oriented programming and Java

Algorithms and Data structures (recursion, trees, lists, hashtables, . . . )


Course information

Web page: http://cs.lth.se/eda180

will be updated during the course

LiteratureCourse material, will be made available on the web site.

Lectures, seminars, labs, project, articlesNot handed out - print yourself.

Textbook

A.W. Appel: Modern Compiler Implementation in Java, 2ndEdition, Cambridge University Press, 2002, ISBN:0-521-82060-X.Available as an e-book viahttp://www.lub.lu.se/en/search/lubsearch.html


http://cs.lth.se/eda180

http://www.lub.lu.se/en/search/lubsearch.html

Course structure

14 lectures

Tuesday 15-17, MA:020Wednesday 10-12, E:A

5 seminars (give extra points on exam)

Thursday 10-12, MA:026Start this week

6 computer assignments / lab sessions (mandatory)

Thursday 13-15 or Friday 10-12 (E:Hacke)Sign up by Thursday Jan 24 (see course web)Start next weekMust be completed before exam and course project

Written exam, March 13

Course project, VT2


People helping with the course

Lectures:

Gorel HedinEmma Soderberg

Guest lectures:

Roger Henriksson (automatic memory management)Jonas Skeppstedt (code optimization)

Seminars

Emma Soderberg

Programming assignments and lab sessions

Niklas ForsJesper Oqvist


Seminars

Active participation gives extra points at the exam

Before the seminar

Try to solve the problems at home.Write down your solutions, bring them with you, be preparedto present them at the seminar.

At the seminar

Mark the problems you are willing to present solutions for.The seminar leader selects some students to present theirsolutions. Discussion of the solutions.

At the written exam (Note! Only for exams this year)

Your markings will give you a maximum of 10% extra points atthe written exam.


Programming assignments / Lab sessions

Work in pairs

Use the lecture break to form pairs!

Make the preparations before each lab session.

If you complete the assignment in advance, you must anywaygo to the lab session to get it approved.


Examination

Exams take place

Wednesday, March 13, 8-13, Sparta:DFriday, August 30, 8-13, Victoriastadion 1A (1 week advanceregistration required)

Prerequisites

Completed programming assignments


Project

Standard project

Design of a small procedural languageImplementation of a compiler from source text to Intelassembly code

Work in pairs

Deadlines

Intermediate deadlines given laterFinal deadline for completed and approved project: May 3rd


Project outcome

compiler

assembly code

source code

csum = a + b + 1;

movl a, %eax

addl b, %eax

addl $1, %eax

movl %eax, csum


What happens after compilation?

compiler

assembly code

source code

assembler

linkerloader

object code

machinecode

machinememory

library object code


A closer look at the compiler

lexicalanalysis

syntacticanalysis

semanticanalysis

intermediatecode generation

machine codegeneration

optimization

source code

machinecode


Intermediate representations

lexicalanalysis

syntacticanalysis

semanticanalysis



optimization

AST

source code

machinecode

tokens intermediate code

intermediate code

attributedAST

analysis synthesis


Front and back end

lexicalanalysis

syntacticanalysis

semanticanalysis



optimization

source code

machinecode

front end back end


Intermediate code

intermediatecode

FrontEndL

BackEndIntel


Several front and back ends

intermediatecode

FrontEndL

BackEndIntel

FrontEndC FrontEndPL0

BackEndMIPS Interpreter


Why?

It is more rational to implement m front ends + n back endsthan m ∗ n compilers.

Many optimizations are best performed on intermediate code.

It may be easier to debug the front end using an interpreterthan a target machine.


Compilation and Interpretation

A compiler translates a high level program to lowlevel/machine code.

An interpreter executes a high/low level program by callingone procedure for each program construct.

An interpreter may use a JIT (“just in time”) compiler tocompile all or parts of the the program into machine codeduring execution.


Program representations

lexicalanalysis

syntacticanalysis

semanticanalysis



optimization

AST

source code

machinecode

tokens intermediate code

intermediate code

attributedAST


Lexical analysis (scanning)

Source text Tokens

while (k<=n) {

sum=sum+k;

k=k+1;

}

A token is a symbolic name, sometimes with an attribute.A lexeme is a string corresponding to a token.



Source text Tokens

while (k<=n) { WHILE LPAR ID(k) LEQ ID(n) RPAR LBRA

sum=sum+k;

k=k+1;

}

A token is a symbolic name, sometimes with an attribute.A lexeme is a string corresponding to a token.



Source text Tokens

while (k<=n) { WHILE LPAR ID(k) LEQ ID(n) RPAR LBRA

sum=sum+k; ID(sum) EQ ID(sum) PLUS ID(k) SEMI

k=k+1; ID(k) EQ ID(k) PLUS INT(1) SEMI

} RBRA


Syntactic analysis (parsing)


Abstract Syntax Tree (AST)

used for program representation inside tools

very similar to the parse tree, but

contains only essential tokenshas a simpler more natural structure

often represented by a typed object-oriented model

abstract classes (statements, expressions, ...)concrete classes (while, if, add, subtract, ...)


Parse tree – spans all tokens


Abstract syntax tree – only essential structure and tokens


AST class hierarchy

Create class hierarchies for statements and expressions!

Invent names for suitable abstract classes!

Which methods are required to traverse the AST?


Draw the class hierarchy

Stmt

WhileStmtgetExpr()getStmt()

AssignmentgetId()getExpr()

CompoundStmtgetNrOfStmts()getStmt(int)

Expr

AddgetExpr1()getExpr2()

LessEqualgetExpr1()getExpr2()

IntgetINT()

IdgetID()


Semantic analysis

Analyze the AST, e.g.

Which variable corresponds to which declaration?

What is the type of an expression?

Are there compile time errors in the program?


Formalisms we will cover

Regular expressions for

defining tokensautomatic generation of scanners

Context-free grammars for

defining concrete syntax treesautomatic generation of parsers

Abstract Grammars for

defining abstract syntax treesautomatic generation of Java classes

Attribute Grammars for

defining properties of AST nodesautomatic evaluation of the attributes

Aspect Modules for

defining fields, methods, and attributes in separate modulesautomatic weaving into Java classes


Compiler tools we will use

JavaCC (Sun/Open source)

Scanner and parser generator

JJTree (Sun/Open source)

adds AST building to JavaCCimplements the Visitor pattern for ASTs

JastAdd (LTH/Open source)

generates Java classessupports static aspect oriented programmingsupports attribute grammars

as (GNU/Open source)

translates assembly code to machine code


Other tools we will use

Ant (Apache/Open source)

Software system builder

JUnit (Object Mentor/Open source)

testing framework

Gdb (GNU/Open source)

debugger


Synthesis

Runtime systems

How are variables accessed and procedures called?How are objects and classes represented?How is memory reused?

Intermediate code generation

Straight-forward mapping from ASTUse unlimited number of registers (temporaries)

Optimization

Only brief overview (see EDA230 for detailed treatment)

Machine code generation

Instruction selectionRegister allocation


Paradigms

Imperative programming

ProceduralObject oriented

Declarative programming

FunctionalLogicalConstraintRegular expressionsContext-free grammarsAttribute grammars

Hybrid languages

JastAddScala...


Applications of compiler construction

Traditional compilers from source to assembly

Source-to-source translators, preprocessors

Interpreters and virtual machines

Integrated programming environments

Analysis tools

Refactoring tools

Domain-specific languages


Related research at LTH

Extensible compiler tools (Gorel Hedin)

Real-time garbage collection (Roger Henriksson)

Code optimization for multiprocessors (Jonas Skeppstedt)

Natural language processing (Pierre Nugues)

Constraint solvers (Krzysztof Kuchcinski)

Data-flow languages (Jorn Janneck)

Languages for pervasive systems (Boris Magnusson)

Languages for physical modeling (Johan Akesson)


Course goals

After this course...

You should be able to use

regular expressionscontext-free grammarsabstract grammars

You should be able describe

attribute grammarsruntime systems and garbage collectionsome code optimizations

You should be able to build a compiler, where you

use a parser generatormake semantic analysisdo code generation

You should be able to program, using

static aspect oriented programmingthe visitor pattern


Readings

F1: Introduction

Appel, chapter 1-1.2

F2: Regular expressions

Appel, chapter 2Appel, recommended exercises: 2.1 – 2.8Try solve the problems in Seminar 1


Review questions

Which are the major compilation phases?

What is the difference between the analysis and synthesisphases?

Why do we use intermediate code?

What is the advantage of separating the front and back ends?

What is

a lexeme,a token,a parse tree,an abstract syntax tree,intermediate code,assembly code?


Compiler Construction - Introduction and...

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