DFCXX

DFCxx is a domain-specific language, which allows specifying the computational logic of a streaming computer to generate SystemVerilog hardware descriptions.

DFCxx provides a library of C++ classes (like Stream, Scalar, Kernel), allowing relations between objects to represent the computational logic of a streaming computer.

By inheriting dfcxx::Kernel abstract class and implementing a parameterless constructor this new class represents the main unit of computation, kernel.

The computational logic of a streaming dataflow computer has to be statically scheduled: DFCIR currently has two implementations of scheduling algorithms (Linear Programming-approach and a simple as-soon-as-possible algorithm).

By using one of dfcxx::Kernel::compile-method overloads, it is possible to choose a scheduling strategy and latency configuration for computational elements, as well as the output file for SystemVerilog code to be generated in.

#include "dfcxx/DFCXX.h"

class NewKernel : public dfcxx::Kernel {
public:
  std::string_view getName() override {
    return "NewKernel";
  }

  ~NewKernel() override = default;

  NewKernel() : dfcxx::Kernel() {
    using dfcxx::DFType;
    using dfcxx::DFVariable;

    const DFType &type = dfUInt(32);
    DFVariable &x = io.input("x", type);
    DFVariable &sum = x + x;
    ...
    ...
  }
};

int main(int argc, char **argv) {
    NewKernel kernel;
    DFLatencyConfig config = {
            {dfcxx::ADD_INT, 2},
            {dfcxx::MUL_INT, 3}
    };
    kernel.compile(config, dfcxx::Linear);
}

Prerequisites

[!!!] Current version was tested only on Ubuntu 20.04 [!!!]

DFCxx uses DFCIR and FIRRTL (CIRCT) intermediate representations, making them project's dependencies. DFCIR is present in DFCxx in the form of a git-submodule, so it has to be initialized with the following commands:

git submodule init
git submodule update

CIRCT is also needed to build DFCIR, so please refer to DFCIR building guide before building DFCxx. DFCxx shares dependencies with DFCIR.

[!!!]Currently supported CIRCT release: 1.72.0, Apr 5 2024 (link)[!!!]

Building DFCxx

DFCxx is a CMake package, so in order to build it a simple CMake environment has to be set up.

DFCxx needs to know the locations where DFCIR and CIRCT have been installed, and corresponding full paths to these location have to be passed to CMake environment in the form of DFCIR_BUILD_DIR and CIRCT_BIN_HOME CMake variables:

assuming CIRCT-archive was downloaded in home directory (~) and was extracted using tar -xvf, thus firtool-1.72.0 (the directory with the top-level CMakeLists.txt-file) is also in the home directory, with DFCIR being built as a git-submodule of DFCxx, the CMake environment can be set up using the following commands:

cd <DFCXX_DIR>
mkdir build
cd build
cmake .. -G Ninja -DCIRCT_BIN_HOME="~/firtool-1.72.0" -DDFCIR_BUILD_DIR="<DFCXX_DIR>/DFCIR/build"

After this, use cmake --build . to build DFCxx.

Usage of DFCxx

Currently DFCxx project is concentrated in a single static library - a CMake target, addressed by its alias DFCXX::DFCXX. Using CMake find_package(REQUIRED CONFIG HINTS)-functionality, this library can be incorporated in other projects (the full path after HINTS needs to specify the build-directory for DFCxx).

The following code describes a simple CMakeLists.txt-file of a project, using DFCxx:

cmake_minimum_required(VERSION 3.16 FATAL_ERROR)
project(TESTPROJECT C CXX)
set(CMAKE_CXX_STANDARD 17)

find_package(DFCXX REQUIRED CONFIG HINTS "~/DFCXX/build")

add_executable(TEST test.cpp)
target_link_libraries(TEST DFCXX::DFCXX)

Along with the project, a number of usage examples is provided: they can be found in the examples-directory, and within each example's directory its corresponding kernel definition can be found (*.h-file) with subdirectories code for different scheduling configurations (main.cpp-files).