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#+setupfile: publish.setup
#+title: Vericert Documentation
#+author: Yann Herklotz
* Overview
Vericert translates C code into a hardware description language called Verilog, which can then be synthesised into hardware, to be placed onto a field-programmable gate array (FPGA) or application-specific integrated circuit (ASIC).
#+attr_html: :width 600
#+caption: Current design of Vericert, where HTL is an intermediate language representing a finite state machine with data-path (FSMD) and Verilog is the target language.
#+name: fig:design
[[../images/design.jpg]]
The design shown in Figure [[fig:design]] shows how Vericert leverages an existing verified C compiler called [[https://compcert.org/compcert-C.html][CompCert]] to perform this translation.
* Building Vericert
To build Vericert, the provided Makefile can be used. External dependencies are needed to build the project, which can be pulled in automatically with [[https://nixos.org/nix/][nix]] using the provided ~default.nix~ and ~shell.nix~ files.
The project is written in Coq, a theorem prover, which is extracted to OCaml so that it can then be compiled and executed. The dependencies of this project are the following:
- [[https://coq.inria.fr/][Coq]]: theorem prover that is used to also program the HLS tool.
- [[https://ocaml.org/][OCaml]]: the OCaml compiler to compile the extracted files.
- [[https://github.com/mit-plv/bbv][bbv]]: an efficient bit vector library.
- [[https://github.com/ocaml/dune][dune]]: build tool for ocaml projects to gather all the ocaml files and compile them in the right order.
- [[http://gallium.inria.fr/~fpottier/menhir/][menhir]]: parser generator for ocaml.
- [[https://github.com/ocaml/ocamlfind][findlib]] to find installed OCaml libraries.
- [[https://gcc.gnu.org/][GCC]]: compiler to help build CompCert.
These dependencies can be installed manually, or automatically through Nix.
** Downloading CompCert
CompCert is added as a submodule in the ~lib/CompCert~ directory. It is needed to run the build process below, as it is the one dependency that is not downloaded by nix, and has to be downloaded together with the repository. To clone CompCert together with this project, you can run:
#+begin_src shell
git clone --recursive https://github.com/ymherklotz/vericert
#+end_src
If the repository is already cloned, you can run the following command to make sure that CompCert is also downloaded:
#+begin_src shell
git submodule update --init
#+end_src
** Setting up Nix
Nix is a package manager that can create an isolated environment so that the builds are reproducible. Once nix is installed, it can be used in the following way.
To open a shell which includes all the necessary dependencies, one can use:
#+begin_src shell
nix-shell
#+end_src
which will open a shell that has all the dependencies loaded.
** Makefile build
If the dependencies were installed manually, or if one is in the ~nix-shell~, the project can be built by running:
#+begin_src shell
make -j8
#+end_src
and installed locally, or under the ~PREFIX~ location using:
#+begin_src shell
make install
#+end_src
Which will install the binary in ~./bin/vericert~ by default. However, this can be changed by changing the ~PREFIX~ environment variable, in which case the binary will be installed in ~$PREFIX/bin/vericert~.
** Testing
To test out ~vericert~ you can try the following examples which are in the test folder using the following:
#+begin_src shell
./bin/vericert test/loop.c -o loop.v
./bin/vericert test/conditional.c -o conditional.v
./bin/vericert test/add.c -o add.v
#+end_src
Or by running the test suite using the following command:
#+begin_src shell
make test
#+end_src
* Using Vericert
Vericert can be used to translate a subset of C into Verilog.
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