Question

Answer the following question

Compiling a source program written in a given high level programming language into a machine language takes several steps. Identify the various stages that are normally required. Explain the modules that need to be designed at each stage and indicate the interface (the input and output) of each module at each phase. Give examples.

Answer 1

Phases of a Compiler

only two major phases of compilation

1.Analysis Phase

2.Synthesis Phase

Analysis Phase - An intermediate representation is created from the give source code

* Lexical Analyzer

*Syntax Analyzer

* Semantic Analyzer

* Intermediate Code Generator

lexical analyzer divides the program into tokens

Syntax analyzer recognizes sentences

Semantic analyzer checks static semantics of each construct

Intermediate Code Generator generates abstract code

Synthesis Phase

Equivalent target program is created from the intermediate representation

Code Optimizer optimizes the abstract code

Code Generator translates abstract intermediate code into specific machine instructions

Symbol Table

data structure used while compiling a source code .consist identifier name and their type format .store tokens

1. Lexical Analyzer

reads the source program and converts it into tokens. convert lexems into tokens

tokens

Tokens are defined by regular expressions which are understood by the lexical analyzer

2.Syntax Analyzer

Also called as parser.It develops a parse tree and takes all the tokens one by one from the symbol table and uses Context Free Grammar to construct the parse tree

Syntax error can also be determined at this level

3.Semantic Analyzer

it verifies the parse tree generated in syntax phase .to check the statement is meaningful or not.it also check the type and flow control of program.

4.Intermediate Code Generator

it generate intermediate code in lower level language using the semantics of the source code .it is same for every compiler out there, but after that, it depends on the platform. To build a new compiler we don’t need to build it from scratch. We can take the intermediate code from the already existing compiler and build the last two parts.

5.Code Optimization

transforms the intermediate code so that it consumes fewer resources and produces more speed. optimize the code generated before for better efficiency and better utilization of resources

6.Target Code generator

it writes a code that the machine can understand and also register allocation, instruction selection etc. The output is dependent on the type of assembler. This is the final stage of compilation