ASL Interpreter

Introduction

Example implementation of Arm's Architecture Specification Language (ASL).

The ASL interpreter is a collection of resources to help you to understand and make use of Arm's architecture specifications. It consists of lexer, parser, typechecker and interpreter for the ASL language and an interactive interface for evaluating ASL statements and expressions.

Requirements

To build and run the ASL interpreter, you will need:

• OCaml version 4.07 (other versions may work)
• OPAM OCaml version 2.0.5 (other versions may work)
• The following OPAM packages
  • ocaml - OCaml compiler
  • menhir - parser generator tool
  • ocamlfind - build tool for OCaml
  • ott.0.29 - tool for defining language grammars and semantics (this version or later required)
  • linenoise - OCaml line editing library
  • pprint - OCaml pretty-printing library
  • z3.4.7.1 - OCaml bindings for the Z3 SMT solver (exactly this version is required)
  • zarith - OCaml multiprecision arithmetic library

License and contribution

The software is provided under the BSD-3-Clause licence. Contributions to this project are accepted under the same licence.

This software includes code from one other open source projects

• The CIL project defines a useful visitor class for traversing C ASTs. The file visitor.ml is a modified copy of this class that generalizes the type to work with an arbitrary AST.

  CIL is distributed under a BSD-3-Clause licence.

Building and development

Directory structure

This interpreter consists of a single directory organized as follows

• Metadata, documentation, etc:
  • LICENCE - Software licence
  • README.md - This file
  • asli.odocl - Manifest (for documentation generation)
  • Makefile - build system file
  • _tags - OCaml build system configuration file
• Source code consisting of
  • Lexer
    • lexer.mll - ASL lexer (ocamllex file)
    • lexersupport.ml - indentation-based parsing support
  • Grammar and Parser
    • asl.ott - used to generate the ASL parser and abstract syntax tree (OTT file)
    • asl_visitor.ml - code to traverse abstract syntax tree
    • asl_utils.ml - code to transform abstract syntax tree
  • Typechecker
    • tcheck.ml - typechecker
  • Interpreter
    • primops.ml - implementation of ASL builtin types and operations
    • value.ml - interpreter support code
    • eval.ml - evaluator for ASL language
  • ASL standard library
    • prelude.asl - builtin types and functions
  • Programs
    • asli.ml - interactive ASL tool
    • testlexer.ml - test program that converts ASL code to list of tokens
  • Misc
    • utils.ml - utility code
• Code copied from other open source projects
  • visitor.ml

Installing dependencies

Platform specific instructions:

    MacOS: brew install opam
    Ubuntu: sudo apt-get install opam

Platform independent instructions:

    opam install ocaml
    opam install menhir
    opam install ocamlfind
    opam install ott
    opam install linenoise
    opam install pprint
    opam install z3.4.7.1
    opam install zarith

    eval `opam config env`

You also need to execute this command

    MacOS: export DYLD_LIBRARY_PATH=`opam config var z3:lib`
    Linux: export LD_LIBRARY_PATH=`opam config var z3:lib`

Building

To build the ASL lexer, the ASL interpreter and PDF files containing the ASL grammar, execute these commands.

    make testlexer.native asli pdf doc

Using ASL lexer

This displays a list of tokens in an ASL file including the indent and dedent tokens used to support indentation-based parsing.

    $ ./testlexer.native prelude.asl

Using ASL interpreter

This reads ASL files specified on the command line and provides an interactive environment for executing ASL statements and expressions.

    $ ./asli
                _____  _       _    ___________________________________
        /\     / ____|| |     (_)   ASL interpreter
       /  \   | (___  | |      _    Copyright Arm Limited (c) 2017-2019
      / /\ \   \___ \ | |     | |
     / ____ \  ____) || |____ | |   Version 0.0 alpha
    /_/    \_\|_____/ |______||_|   ___________________________________

    Type :? for help
    ASLi> 1+1
    2
    ASLi> ZeroExtend('11', 32)
    '00000000000000000000000000000011'
    ASLi> bits(32) x = ZeroExtend('11', 32);
    ASLi> x
    '00000000000000000000000000000011'
    ASLi> :quit

Enjoy!