Week 08_Basics of Compiler Construction.pdf
- 2. Compilers • Programming languages are notations for describing computation to people and to machines • All the software (including Operating Systems, Embedded Software, Special Purpose Software, General Software applications) running on the computers was written in some programming language. • Types of languages: • High level language (C++, Java, C-sharp etc.) • Low level language (one-to-one interaction with Machine e.g., Assembly) • Machine level language (Interact directly with Machine’s Hardware in the form of 101010….) • There must be a translation mechanism that tells machine what to do against each set of instruction
- 3. Compilers • A program must be translated into a form in which it can be executed by a computer • The software systems that do this translation are called “COMPILERS” Program in Program in Source Language Target (High level) Language (Machine Level) Errors Compiler
- 4. Objective • The purpose of this course is to become familiar with the functionality of different Phases in the construction of a compiler front end and to gain insight of how these phases are related to each other. • Process of construction of compiler • Lexical analysis • Syntax Analysis • Semantic Analysis • Syntax Directed Translation • Intermediate Code Representation
- 5. Language Processors • Simply stated, a compiler is a program that can read a program in one language – the source language – and translate into an equivalent program in another language – the target language. Source Program • Important Role • Report errors, if any, found in source program Target Program Compiler
- 6. Language Processors • If the target program is an executable machine-language program, it can then be called by the user to process inputs and produce outputs. input output Target Program
- 7. Interpreter • Interpreters are the common kind of language processor. • An interpreter appears to directly execute the program and provide output. Source Program input output Errors Interpreter
- 8. Compiler Vs Interpreter Compiler Interpreter Pros Pros Less space Easy debugging Fast Execution Fast Development Cons Cons Slow Processing Not for large project (Partly solved; Requires more space Separate compilation) Slower Execution Debugging (Interpreter in memory (Improves through IDEs) all the time)
- 9. Language Processors • Example Java language processors combine compilation and interpretation source Program Intermediate Program output input A Hybrid Compiler Virtual Machine Translator
- 10. Language Processors • A Java source program may first be compiled into an intermediate form called bytecodes. • The bytecodes are then interpreted by a virtual machine. • A benefit of this arrangement is that bytecodes compiled on one machine can be interpreted on another machine, perhaps across a network. • In order to achieve faster processing of inputs to outputs, some Java compilers use just-in-time compilers • It translate the bytecodes into machine language immediately before they run the intermediate program to process the input. • In addition to a compiler, several other programs may be required to create an executable target program.
- 11. Language Processors • A source program may be divided into modules stored in separate files. • The task of collecting the source program is sometimes entrusted to a separate program, called a preprocessor. • The preprocessor may also expand “shorthands” called macros into source language statements. • The modified source program is then fed to a compiler. • The compiler may produce an assembly-language program as its output, because assembly language is easier to produce as output and is easier to debug. • The assembly language is then processed by a program called an assembler that produces machine code as its output.
- 12. Language Processors • Large programs are often compiled in pieces, so the machine code may have to be linked together with other object files and library files into the code that actually runs on the machine. • The linker resolves external memory addresses, where the code in one file may refer to a location in another file. • The loader then puts together all of the executable objects files into memory of execution.
- 17. Analysis • Operations performed • Breaks up the source program in to pieces • Imposes a grammatical structure on these pieces • Then an intermediate representation (known as Tree Structure = Syntax Tree, in which we got to know all of the insight operations performed and their hierarchy) is created using this structure • Display an error messages (if any) • It also collects information about the source program and stores in a data structure called symbol table (Symbol table is used in all compilation phases whether directly or in any of its updated form) • Analysis phase is also known as “Front end of a compiler”
- 18. Synthesis • Operations performed • It takes the intermediate representation and information from the symbol tree as input. • Construct the desired target program • Back End of a Compiler
- 19. Compilation Phases • A typical decomposition of a compiler can be done into several phases: