Compiler Designs and Constructions

1
Compiler Designs and Constructions

• Chapter 2 A Simple Compiler
• Objectives
• Demonstration of a simple Compiler
• One Pass Compiler
• Dr. Mohsen Chitsaz

2
Simple Compiler

• Example of a Simple Compiler
• Language
• A2
• BA
• CAB-2
• Method of representation
• Bachus-Naur-Form (BNF)
• Syntax Diagram
• SALARY 2TOTAL 17

3
Simple Compiler

• Grammar
• ltstatementgt ----gt ID ltexpressiongt
• ltexpressiongt ----gt ltprimarygt
• ltexpressiongt ----gtltprimarygt ltadd_opgt
  ltexpressiongt
• ltprimarygt ----gt ID
• ltprimarygt ----gt NUM
• ltadd_opgt ----gt
• ltadd_opgt ----gt -

4
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 15 2 num
• plus 51 add_op
• id 10 Total id
• minus 51 - add_op
• num 15 17 num
• semicolon 53 semicolon

5
Simple Compiler

• Symbol Table, Literal Table
• Salary 2 Total 17
• Identifier Type Value
• Salary int
• Total int 150

6
Simple Compiler

• Parser (Syntax Analyzer)
• Parse Tree
• Salary 2 Total 17

7
Simple Compiler

• Syntax Tree
• Salary 2 Total 17

8
Simple Compiler

• 5. Semantic Analyzer
• Salary 2 Total 17

9
Simple Compiler

• Intermediate Code Generation
• Salary2 total 17

10
Simple Compiler

• Why intermediate code and not assembly code

Pascal
C
Python
Intermediate Code
Final Object Code
11
Simple Compiler

• Code Optimization
• a. Salary 2 Total 17
• b. Salary Total 15

12
Simple Compiler

• Final Code Generation
• a. ADDL3 Total , 2, R5
• SUBL3 R5, 17, Salary
• b. SUBL3 Total, 15, Salary