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PyCDE

PyCDE stands for Python circuit design entry. It is an experimental, opinionated, Python-based fronted for CIRCT's Python bindings. The goal is to make the definition of hardware modules using the bindings simple.

Installation

via Pip

PyCDE is now being released on PyPI: https://pypi.org/project/pycde/

Installing and Building with Wheels

The simplest way to get started using PyCDE is to install it with the pip install command:

$ cd circt
$ pip install frontends/PyCDE --use-feature=in-tree-build

If you just want to build the wheel, use the pip wheel command:

$ cd circt
$ pip wheel frontends/PyCDE --use-feature=in-tree-build

This will create a pycde-<version>-<python version>-<platform>.whl file in the root of the repo.

Manual Compilation

If you are interested in developing PyCDE, or simply want to install it yourself with CMake, you can configure CMake similarly to the Python bindings:

$ cd circt
$ mkdir build
$ cd build
$ cmake -G Ninja ../llvm/llvm \
    -DCMAKE_BUILD_TYPE=Debug \
    -DLLVM_ENABLE_PROJECTS=mlir \
    -DLLVM_ENABLE_ASSERTIONS=ON \
    -DLLVM_EXTERNAL_PROJECTS=circt \
    -DLLVM_EXTERNAL_CIRCT_SOURCE_DIR=.. \
    -DMLIR_ENABLE_BINDINGS_PYTHON=ON \
    -DCIRCT_BINDINGS_PYTHON_ENABLED=ON \
    -DCIRCT_ENABLE_FRONTENDS=PyCDE

Afterwards, use ninja check-pycde to ensure that PyCDE is built and the tests pass.

If you want to use PyCDE after compiling it, you must add the core CIRCT bindings and PyCDE to your PYTHONPATH:

export PYTHONPATH="$PWD/build/tools/circt/python_packages/circt_core:$PWD/build/tools/circt/python_packages/pycde"

If you are installing PyCDE through ninja install, the libraries and Python modules will be installed into the correct location automatically.

Usage

The following example demonstrates a simple module that adds two integers:

import pycde

from circt.dialects import comb


@pycde.module
class AddInts:
    a = pycde.Input(pycde.types.i32)
    b = pycde.Input(pycde.types.i32)
    c = pycde.Output(pycde.types.i32)

    @pycde.generator
    def construct(mod):
        mod.c = comb.AddOp.create(mod.a, mod.b)


system = pycde.System([AddInts])
system.print()
system.generate()
system.print()
system.emit_outputs()

Modules are decorated with @pycde.module, and define their ports using pycde.Input and pycde.Output. To control how the body of the module is generated, decorate a method with @pycde.generator. The generator is passed an object of the module, and ports can be accessed through named attributes.

In order to work with modules, you must add them into a pycde.System. This is constructed by passing a list of modules. Calling the generate method will run the module(s) generators. Calling the print_verilog method will export the system to System Verilog.

The above example will print out three times:

The AddInts module with an empty body
The AddInts module after its body has been generated
The AddInts module represented in System Verilog

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