File Structure.html    Author McKeeman    Copyright © 2007    index

Components

Compilers, generally speaking, divide into a front-end, back-end and runtime. An intermediate representation (IR) is passed from the front-end to the back-end. In xcom all these algorithms are imbedded in objects. Each object, once constructed, holds the information it has gathered. Each such object is passed to any other object needing the contained information. Each object provides its information either by public fields or a public access methods.

Analysis

• Cfg object -- read the context-free grammar for the input language and build tables.
• Lexer object -- build a lexeme sequence from the source program.
• Parser object -- select the meaningful lexemes and construct a shift/reduce sequence.
• Tree object -- build tree from the shift/reduce sequence.
• Symbols object -- walk the tree to build a symbol table pairing names to attributes.

Synthesis

• Generator object -- pass information from one part of the IR to another and detemine the execution sequence.
• Emitter object -- choose the instructions.
• Assembler object -- assemble, format the executable, and launch the user program.

Runtime

• getCfun.c -- implement builtin functions, link X-to-X calls.
• runX86.c -- execute compiled user programs, report runtime errors.