COMPILER

COMPILER

1. Is a computer program that translates text written in a computer language into another computer languague

   • Compilation

2. Operations

   • Lexing
   • Preprocessing
   • Parsing
   • Semantic analysis
   • Code optimizations
   • Code generation

3. Characteristics

   • Bug-free
   • It generates correct machine code
     • This code must run fast
   • It must run fast
   • It must be portable
   • It must print good diagnostics and error messages

4. Types

   • One-pass compiler
     • It passes through the source code of each compilation unit only once
       • It can´t look back at a code it previously processed
     • Limited scope available
   • Multi-pass compiler
     • It processes the source code several times
       • The intermediate code is improved pass by pass
     • Greater scope of the passes
       • Better code generation
   • Source-to-source compiler
     • It takes a high level language
       • Its inputs and outputs a high level language

5. Classification

   • A native compiler
     • Its output is intended to directly run on the same type of computer
   • Cross compiler
     • Is designed to run on a different platform

6. Design

   • The source language is large and complex and high quality output
     • The design may be split into a number of relatively independent phases
       • Front end
         • It is where syntactic and semantic processing takes place
         • It includes all analysis phases end the intermediate code generator
       • Middle end
         • It performs optimizations on a form other than the source code
       • Back end
         • It performs more analysis, transformations and optimizations that are for a particular computer
         • It generates code for a particular processor and OS

7. Analysis

   • The source program is analyzed to determine whether it meets the syntactic and static semantic constraints
     • Lexical analysis
       • It works as interface between source program and syntax analyzer
       • It reads a stream of characters as an input and produce a sequence of tokens
     • Syntax Analysis
       • Syntax analyser or parser groups the tokens produced by the scanner into syntactic structures
         • Parsing expressions and statements
     • Semantic Analysis
       • It is a pass by a compiler that adds semantical information to the parse tree
       • It performs certain checks

8. Out target program

   • Code generator
     • Process by which a compiler´s code generator converts a syntactically-correct program into a series of instructions
   • Code optimizier
     • Process of tuning the output of a compiler to minimize some attribute of an executable program
   • Intermediate code generator
     • Three address code