Compiler Design. Lecture 1

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1 Compiler Design Lecture 1

2 Problem in Real Life

3 Problem in Real Life Egyptian Arabic

4 Problem in Real Life Egyptian British Arabic English

5 Problem in Real Life Egyptian? British Arabic English

6 Solution Egyptian? British Arabic English

7 Solution Egyptian? British Sol(1):No Translator (En) advantages: Faster interaction. disadvantages: Difficult (He must learn english). Arabic English

8 Solution Egyptian? British Sol(1):No Translator (En) advantages: Faster interaction. disadvantages: Difficult (He must learn english). Arabic Sol(2):Translator (Ar) advantages: He can use his native language, easier. disadvantages: Slower (additional person). English

9 Problem in Computer World You Computer High level language Machine language

disadvantages: Difficult,you must use machine language.

10 Solution You Computer High level language Sol(1):No Translator (ML) advantages: Faster (no translation is required). disadvantages: Difficult,you must use machine language. Sol(2):Translator (HL) advantages: You can use high level language. Easier to debug. Readable. disadvantages: Need additional phase (translation). Machine language

11 Translator Translates a program into a form in which it can be executed by a computer. The most common kinds: Compiler. Interpreter.

12 Compiler Source Program Errors Compiler Target Program Fig1. Translation

13 Compiler Source Program Inputs Errors Compiler Target Program Target Program Fig1. Translation Outputs Fig2. Execution

14 Compiler Source Program Inputs Errors Compiler Target Program Target Program Fig1. Translation Outputs Fig2. Execution It does translation only (Produces target program). Target program maps inputs to outputs without having to compile the source program again.

15 Interpreter Source Program Errors Interpreter Inputs Outputs Fig1. Translation+Execution

16 Interpreter Source Program Errors Interpreter Inputs Outputs 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.

17 Processing Time Target program produced by compiler has less processing time (faster) than the interpreted source program.(true or false)?

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

19 Processing Time Target 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

20 Processing Time Target 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 Interpreted source program: Processing time=translation time+execution time--> large processing time-->slower

21 Language Processing System Programs needed to create an executable generated code.

22 Language Processing System Programs needed to create an executable generated code. Source Program Compiler Assembler Assembly language program Machine language module(s) Library routines(ml) Linker Loader Machine language program(exe) Memory

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

24 Linker Source file Assembler Object file Source file Assembler Object file Linker Executable file Source file Assembler Object file Program library

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

26 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.

27 Compiler Structure Lexical Analyzer/Scanner Syntax Analyzer/Parser Symbol Table Semantic Analyzer Intermediate Code Generator Code Optimizer Code Generator

28 Lexical Analyzer/Scanner Performs 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.

29 Lexical Analyzer/Scanner Performs 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. Scanner Source Program position = initial + rate * 60 Lexeme Token position <id, 1> = <=> initial <id,2> + <+> rate <id, 3> * <*> 60 <60> <id,1> <=> <id,2> <+> <id,3> <*> <60> Symbol Table 1 position... 2 initial... 3 rate...

30 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 nodes If it is not correct --> syntax error. Example

31 Semantic Analyzer Uses syntax tree and the information in the symbol table. Checks for semantic errors (type checking). Possibly performs coercions.

32 Intermediate Code Generator Generates 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.

33 Code Optimizer Improves the intermediate code so that faster and shorter target code that consumes less power can be obtained. Reduce redundancy. Example.

34 Code Generator Maps (optimized) intermediate code into the target code. Registers and memory locations are selected for each of the variables. Example.

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