Compiler Design – Lecture 0 - ECED Mansoura · PDF fileCompiler Design Lecture 1 Sunday, October 3, 2010. ... Target program produced by compiler has less processing time (faster)

Compiler DesignLecture 1

Sunday, October 3, 2010

Problem in Real Life



Egyptian

Arabic



Egyptian British

Arabic English


?


Egyptian British

Arabic English


Solution

Egyptian British ?

Arabic English


Solution

Egyptian British ?

Arabic English

Sol(1):No Translator (En)advantages:

•Faster interaction.disadvantages:

•Difficult (He must learn english).


Solution

Egyptian British ?

Arabic English Sol(2):Translator (Ar)advantages:

•He can use his native language, easier.disadvantages:

•Slower (additional person).

Sol(1):No Translator (En)advantages:

•Faster interaction.disadvantages:

•Difficult (He must learn english).


Problem in Computer World

You Computer

High level language Machine language


SolutionYou Computer

High level language

Machine language Sol(2):Translator (HL)

advantages:•You can use high level language.

✓Easier to debug.✓Readable.

disadvantages:•Need additional phase (translation).

Sol(1):No Translator (ML)advantages:

•Faster (no translation is required).disadvantages:

•Difficult,you must use machine language.


Translator

Translates a program into a form in which it can be executed by a computer.

The most common kinds:

๏Compiler.

๏ Interpreter.


Compiler

Compiler

Source Program

Target Program

Errors

Fig1. Translation


Compiler

Compiler

Source Program

Target Program

Errors Target Program

Inputs

Outputs

Fig1. Translation Fig2. Execution


Compiler

Compiler

Source Program

Target Program

Errors Target Program

Inputs

Outputs

Fig1. Translation Fig2. Execution

•It does translation only (Produces target program).•Target program maps inputs to outputs without having to compile the source program again.


Interpreter

Interpreter

Source Program

Outputs

Errors Inputs

Fig1. Translation+Execution


Interpreter

Interpreter

Source Program

Outputs

Errors Inputs

Fig1. Translation+Execution

•Translation + Execution (statement by statement)•Every time the source program is run, it will do translation.•Do translation whether or not there are changes in the source program.


Processing TimeTarget program produced by compiler has less processing time (faster) than the interpreted source program.(True or false)?



True



Target program produce by compiler:Processing time=Execution time only-->small

processing time-->faster

True



Target program produce by compiler:Processing time=Execution time only-->small

processing time-->fasterInterpreted source program:

Processing time=Translation time+Execution time--> large processing time-->slower

True


Language Processing SystemPrograms needed to create an executable generated code.


Language Processing SystemPrograms needed to create an executable generated code.

Compiler

Source Program

Assembler

Linker

Assembly language program

Machine language module(s)

Loader

Library routines(ML)

Machine language program(exe)

Memory


Assembler

Translate target program (assembly program) into machine language program.


Linker

3

Object file format

• Object file header describes the size and position of the other pieces of the file

• Text segment contains the machine instructions• Data segment contains binary representation of data in

assembly file• Relocation info identifies instructions and data that depend

on absolute addresses• Symbol table associates addresses with external labels and

lists unresolved references• Debugging info

Object fileheader

Textsegment

Datasegment

Relocationinformation

Symboltable

Debugginginformation

Process for producing an executable file

Objectfile

Sourcefile Assembler

LinkerAssembler

Assembler Programlibrary

Objectfile

Objectfile

Sourcefile

Sourcefile

Executablefile


Loader

Part of the OS that brings an executable file residing on disk into memory and starts its running.


Compiler Structure

There are 2 parts(phases):

✓Analysis(Front-end):➡ Determines the operations implied by the source program which are

recorded in a tree structure.

➡ Collects information about the source program and stores it in a data structure called symbol table.

➡ Machine independent.

✓Synthesis(Back-end):➡ Constructs the target program from the intermediate representation and

information in symbol table.

➡ Machine dependent.


Compiler StructureLexical Analyzer/Scanner

Syntax Analyzer/Parser

Semantic Analyzer

Intermediate Code Generator

Code Optimizer

Code Generator

Symbol Table


Lexical Analyzer/ScannerPerforms lexical analysis (scanning).Steps:✓ Reads source program character by character from left to right.✓ Groups characters into lexeme.✓ For each lexeme, it produces a token.✓ Stores information about the token in the symbol table.


Lexical Analyzer/ScannerPerforms lexical analysis (scanning).Steps:✓ Reads source program character by character from left to right.✓ Groups characters into lexeme.✓ For each lexeme, it produces a token.✓ Stores information about the token in the symbol table.

Source Programposition = initial + rate * 60

ScannerLexeme Tokenposition <id, 1>

= <=>initial <id ,2>

+ <+>rate <id, 3>

* <*>60 <60>

<id,1> <=> <id,2> <+> <id,3> <*> <60>

1 position ...

2 initial ...3 rate ...

Symbol Table


Syntax Analyzer/Parser

Performs syntax analysis (parsing).

Checks if the token sequence is correct with respect to language specification.

If it is correct, it will build syntax tree using tokens as nodesIf it is not correct --> syntax error.

Example


Semantic Analyzer

Uses syntax tree and the information in the symbol table.

Checks for semantic errors (type checking).

Possibly performs coercions.


Intermediate Code GeneratorGenerates an intermediate code (machine independent).This code should be:✓easy to produce.✓easy to translate into the target language.

Example: three-address code✓assembly-like instructions✓at most three operands per instruction.✓at most one operator on RHS.✓temporary names hold the computed values.


Code Optimizer

Improves the intermediate code so that faster and shorter target code that consumes less power can be obtained.

Reduce redundancy.

Example.


Code Generator

Maps (optimized) intermediate code into the target code.

Registers and memory locations are selected for each of the variables.

Example.


Documents

Compiler Design – Lecture 0 - ECED Mansoura · PDF fileCompiler Design Lecture 1 Sunday, October 3, 2010. ... Target program produced by compiler has less processing time (faster)