Structure and function of Compiler

Any compiler must perform two major tasks

• analysis of the source program
• synthesis of a machine language program

Fig: Structure of a compiler

Scanner

• the scanner begins the analysis of the source program by reading the input, character by character, and grouping characters into individual words and symbols (tokens)
  • RE (Regular Expression)
  • NFA (Non-deterministic finite automata)
  • DFA (Deterministic finite automata)
  • LXA

Parser

• Given a format syntax specification (typically as a context-free grammar [CFG]), the parser reads tokens and groups them into units as specified by the productions of the CFG being used.
• As syntactic structure is recognized, the parser either calls corresponding semantic routines directly or builds a syntax tree.
  • CFG (Context Free Grammar)
  • BNF (Backus-Naur Form)
  • GAA (Grammar Analysis Algorithms)
  • LL, LR, SLR, LALR Parsers
  • YACC

Semantic Routines

• perform two functions
  • check the static semantics of each construct
  • Do the actual translation
  • heart of the compiler
    • syntax Directed Translation
    • semantic Processing Techniques
    • IR (intermediate Representation)

Optimizer

• The IR generated by the semantic routines is analyzed and transformed into functionally equivalent but improved IR code
• This phase can be very complex and slow
• peehole optimization
• loop optimization, register allocation, code scheduling
  • register and temporary management
  • peehole optimization

Code Generator

• interpretive code generation
• generating code from Tree/Dag
• Grammar-Based code generator