1. Compiler Designs and Constructions
Chapter 2: A Simple Compiler
Compiler Designs and Constructions
Chapter 2: A Simple Compiler
Objectives:
Demonstration of a simple Compiler
One Pass Compiler
Dr. Mohsen Chitsaz
Chapter 2: A Simple Compiler
COSC 470

2. Chapter 2: A Simple Compiler
Example of a Simple Compiler
Language
A=2;
B=A;
C=A+B-2;
Method of representation:
Bachus-Naur-Form (BNF)
Syntax Diagram
SALARY = 2+TOTAL – 17; ID
Num = + - ;
Chapter 2: A Simple Compiler

3. Chapter 2: A Simple Compiler
Grammar
<statement> ----> ID = <expression>;
<expression> ----> <primary>
<expression> ----><primary> <add_op> <expression>
<primary> ----> ID
<primary> ----> NUM
<add_op> ----> +
<add_op> ----> -
Chapter 2: A Simple Compiler

4. Chapter 2: A Simple Compiler
Scanner (Lexical Analyzer)(Tokenizer)
Salary = 2 + Total – 17;
Token Token Token
Representation Lexeme Type (Attribute)
id 10 Salary id
Ass 50 = ass_op
num num
plus add_op
id 10 Total id
minus add_op
num num
semicolon 53 ; semicolon
Chapter 2: A Simple Compiler

5. Simple Compiler Symbol Table, Literal Table Salary = 2 + Total – 17;
Identifier Type Value
Salary int
Total int 150
Chapter 2: A Simple Compiler

6. Chapter 2: A Simple Compiler
Parser (Syntax Analyzer):
Parse Tree:
Salary = 2 + Total – 17;
Chapter 2: A Simple Compiler

7. Chapter 2: A Simple Compiler
Syntax Tree:
Salary = 2 + Total – 17;
Chapter 2: A Simple Compiler

8. Chapter 2: A Simple Compiler
5. Semantic Analyzer:
Salary = 2 + Total – 17;
Chapter 2: A Simple Compiler

9. Chapter 2: A Simple Compiler
Intermediate Code Generation:
Salary=2 + total –17 ;
Operator
OP1
OP2
Result + 2
Total
Temp1 - 17
Temp2 =
Salary
Chapter 2: A Simple Compiler

10. Chapter 2: A Simple Compiler
Why intermediate code and not assembly code
C++
Pascal
Python
Intermediate Code
Final Object Code
Chapter 2: A Simple Compiler

11. Chapter 2: A Simple Compiler
Code Optimization:
a. Salary = 2 + Total – 17;
b. Salary = Total – 15;
Operator
OP1
OP2
Result + 2
Total
Temp1 - 17
Salary
Chapter 2: A Simple Compiler

12. Chapter 2: A Simple Compiler
Final Code Generation:
a. ADDL3 Total , #2, R5
SUBL3 R5, #17, Salary
b. SUBL3 Total, #15, Salary
Chapter 2: A Simple Compiler
COSC 470