cs419 compiler lec1&2 introduction

Compilers

WELCOME TO A JOURNEY TO

CS419Spring 2014

Lecture1: Introduction

Cairo UniversityFCI

Dr. Hussien SharafComputer Science [email protected]

LECTURE OUTLINE

Grading and policy Course outline and

references Chapter one

2Dr. Hussien M. Sharaf

GRADING AND POLICY


Grades will be based on 100 possible points, using the following distribution schedule:Assignments: 5% Mid-term Exam : 10% Group Project: 10%Practical: 10%Attendance: 5%Final Exam: 60%

COURSE OUTLINE AND REFERENCES

Chapter one – Introduction Chapter three- Lexical analysis

definition - using Regular Expression Chapter three- Lexical analysis using

DFA Chapter three- Lexical analysis using

NFA and Transfer NFA to DFA.


COURSE OUTLINE AND REFERENCES Chapter four- Syntax analysis using

CFG. Chapter four- Syntax analysis, Parsing

trees and Ambiguity. Chapter four - Removing Left

Recursion and Left Factoring. Chapter four - Syntax analysis (CFG)

using Top-down parsing.


COURSE OUTLINE AND REFERENCES Chapter four - First and Follow

operators. Chapter four - Syntax analysis (CFG)

using Bottom-Up (predictive/LR) parsing.

Chapter four - Construction of “LR Parsing Tables” / “parsing Table LL1”

Semantic analysis Intermediate code and code generation.


LECTURE1 OUTLINE Introduction is split into two lectures: Lec1: Overview

What are compilers Phases ( architecture ) of a Compiler. Some Data structures that are required for

compiler’s work: Token Symbol table. Literal table Parse tree


LECTURE2 OUTLINE Lec2: Overview

Phases of a Compiler: Scanning. Parsing. Semantic analysis. Intermediate code generation. Code generation.


WHAT ARE COMPILERS?A program that translates one language to another.

Responsibility: 1. Accepts a source program

typically written in a high- level language.

2. Produces an equivalent target program typically in assembly or machine language.

3. Reports error messages as part of the translation process.

compilerSource programUsually High level language

Target programUsually machine language

Error message


COUSINS OF COMPILERS

1. Interpreter: is a program that ultimately performs the same function as a compiler, but in a different manner. It works by scanning through the source program instruction by instruction. As each instruction is encountered, the interpreter translates it into machine code and executes it directly.

2. Assembler: is a program that automatically translates the source program written in assembly language and to produce as output an object code written in binary machine code.

3. Linker: is a program that takes one or more objects generated by compilers and assembles them into a single executable program.

4. Loader: (is a routine that) loads an object program into memory and prepares it for execution


DIFFERENT ARCHITECTURAL VIEWS

1. Functional view : 6 phases.2. Logical view: the 6 phases are grouped into two

main categories A. Analysis VS synthesis.B. Front end VS back end.

3. Operations view: execute one or more phase into one pass. Each pass builds or updates the output of the previous pass.

A. Scanning & parsing.B. Sematic analysis.C. Code generation & optimization.


ARCHITECTURE/PHASES OF A COMPILER

Scanner/lexical analyzer

Parser/ syntax analyzer

Semantic analyzer

Source Code optimization

Code generator

Target Code optimization

Stream of characters

Stream of tokens

Parse/syntax tree

Annotated tree

Intermediate code

Target code

Target code

Literal Table

Symbol Table

Dr. Hussien M. Sharaf

12

SOME DATA STRUCTURES

1. Token

2. Symbol table

3. Literal table

4. Parse tree

5. Semantic parse tree

6. Intermediate code


1. TOKEN

Single Symbol ahead: In most languages the scanner needs to generate only one token ahead at a time.

In this case you don’t need a collection/array of tokens, only one global variable can be used.

Dr. Hussien M. Sharaf

2. SYMBOL TABLE1. Stores information associated with

identifiers. Information associated with variables like [name, type, address, size (for array), etc.]

2. Stores Information associated with functions like [name, type of return value, parameters, address, etc.]

name Type address size (for array)

x int OxA300 n/a

y int OxA304 n/a

c char OxA308 10

Sample code:

int x, y;char c[10];x = 5;


2. SYMBOL TABLE (CONT’D)

3. Use defined data types like structs, enums and classes.

The symbol table is modified by the scanner, parser, and semantic analyzer.

The information at the symbol table is used by intermediate code generator phase and machine code generator phase.

Mostly use hash table for efficiency. Because access time is O(k) and space consumption is not a concern.


3. LITERAL TABLE

Store constants and strings used in program reduce the memory size by reusing

constants and strings Can be combined with symbol table in

some implementations.


4. PARSE TREE Dynamically-allocated, pointer-based

TREE structure Sample code


5. SEMANTIC PARSE TREE Usually the same parse tree is used

and annotations are added for each node.


6. INTERMEDIATE CODE The structure of the

code is kept as simple as possible usually three-address code.

Each instruction is allows only three addresses (variables).

Each instruction is added as an entry into a linked list that allows dynamic growth.


Var2 Var3opVar1

Var2 Var3opVar1

…. …op….

NULL

End of chapter 1

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cs419 compiler lec1&2 introduction

Education

array code

object code

token symbol table

intermediate code generation

code generation optimization

introduction chapter

dfa chapter

symbol table contd