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LISP Compiler

Example Code

(defn range (from to)
      (if (eq? from to)
          (list from)
          (cons from
                (range (fxadd1 from) to))))
(defn fizzbuzz (n)
      (cond
        ((eq? (fxrem n 15) 0) (puts "FizzBuzz"))
        ((eq? (fxrem n 3) 0) (puts "Fizz"))
        ((eq? (fxrem n 5) 0) (puts "Buzz"))
        (else (inspect n))))

(for-each fizzbuzz (range 1 100))

Getting Started

  1. Use chicken-scheme to build the compiler & the stdlib
  2. Compile some program to LLVM-IR
  3. Combine it w/ the stdlib files
  4. Run it
make bootstrap
./compiler < programs/fizzbuzz.csm > fizzbuzz-body.ll 
cat stdlib-ll/*.ll stdlib.ll fizzbuzz-body.ll > fizzbuzz.ll
lli fizzbuzz.ll

Design Decisions

  • 64bit only
  • Tagged Pointers for values, 3bit tag, 61bit value
    • 000: Integer
    • 001: Symbol
    • 010: Char
    • 100: Closure
    • 101: String
    • 110: Pair
    • 111: Hardcoded primitives, #t, #f, '()
  • Symbols are limited to 31 chars

Limitations

  • Not compliant to any standart
  • No GC => compiling itself uses ~1GB of RAM

Project Structure

  • compiler.scm Main compiler logic
  • helper.scm Helper functions that are not part of the stdlib
  • llvm.scm Helper functions for outputting LLVM-IR code
  • reader.scm Recursive descent parser for the input language
  • syntax.scm Defines the syntax of the input language
  • `preprocessing/
    • desugar.scm Convert cond to if etc.
    • alpha-convert.scm Rename variables to prevent naming collisions
    • closure-convert.scm Convert fns to closures & lambdas w/o free variables
  • compatibility.scm Some macros & functions to make chicken scheme understand the compiler source code
  • stdlib-ll/ Collection of low-level stdlib functions written directly in LLVM-IR

Special Syntax

  • ~> Thread-first macro like in clojure
  • ~>> Thread-last macro like in clojure

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