Cs419 Compiler lec1&2 introduction

WELCOME TO A
JOURNEY TO
CS419

Dr. Hussien Sharaf
Computer Science Department

dr.sharaf@from-masr.com

LECTURE OUTLINE
 Grading

and policy
 Course outline and references
 Chapter one

Dr. Hussien M. Sharaf

2

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%

3

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.



4

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.



5

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.



6

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

7

LECTURE2 OUTLINE


Lec2: Overview


Phases of a Compiler:






Scanning.
Parsing.
Semantic analysis.
Intermediate code generation.
Code generation.


8

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

Source
program

Responsibility:

Usually
High level
language

1. Accepts a source program

typically written in a high- level
language.

compiler

Target
program
Usually
machine
language

Error
message

2. Produces an equivalent target

program typically in assembly or
machine language.
3. Reports error messages as part

of the translation process.

9

COUSINS OF COMPILERS
1.

2.

3.

4.

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.
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.
Linker: is a program that takes one or more objects
generated by compilers and assembles them into a
single executable program.
Loader: (is a routine that) loads an object program into
memory and prepares it for execution


10

DIFFERENT ARCHITECTURAL VIEWS
1.
2.

Functional view : 6 phases.
Logical view: the 6 phases are grouped into two main
categories
A.
B.

3.

Analysis VS synthesis.
Front end VS back end.

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

Scanning & parsing.
Sematic analysis.
Code generation & optimization.


11

ARCHITECTURE/PHASES OF A COMPILER
Stream of
characters

Scanner/lexical analyzer
Stream of tokens

Parser/ syntax analyzer
Parse/syntax tree

Literal Table

Semantic analyzer
Annotated tree

Source Code optimization
Intermediate code

Symbol Table

Code generator
Target code

Target Code optimization
Target code

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


13


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.


2. SYMBOL TABLE
1.

2.

Stores information associated with identifiers.
Information associated with variables like
[name, type, address, size (for array), etc.]
Stores Information associated with functions
like [name, type of return
value, parameters, address, etc.]
Sample
name
Type address size (for array)
code:
x
int
OxA300 n/a
y
int
OxA304 n/a
int x, y;
c
char OxA308 10
char c[10];
x = 5;


15

2. SYMBOL TABLE (CONT’D)
Use defined data types like structs, enums
and classes.
 The symbol table is modified by the scanner,
parser, and semantic analyzer.
3.





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.


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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.


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4. PARSE TREE
Dynamically-allocated, pointer-based
TREE structure
 Sample code



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5. SEMANTIC PARSE TREE


Usually the same parse tree is used and
annotations are added for each node.


19

6. INTERMEDIATE CODE
The structure of the code
is kept as simple as
possible usually threeaddress code.
 Each instruction is allows
only three addresses
(variables).
 Each instruction is added
as an entry into a linked
list that allows dynamic
growth.



Var1

Var2

op

Var3

Var1

Var2

op

Var3

….

….

op

…

NULL

20

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Cs419 Compiler lec1&2 introduction

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