SVPY

What is SVPY?

SVPY is a simple python-based precompiler used to accelerate the process of coding in Verilog/System Verilog. It allows for easy insertion of python code into SV files, and can be highly customized with plugins.

Basic Usage

When a file is processed by SVPY, each line in the SV file is simply passed along to the output file unless a macro is specified. If a macro is found, that line is instead interpreted as python code.

To write something to the output file with python, you can use svwrite(line) to dynamically write a line to the output. Some examples of macro usage are as follows:

// Any line starting with "$ " is a macro
$ x = 1
$ y = 2
$ svwrite("logic foo = " + str(x + y))

// Triple dollar signs indicate block macro
$$$
from math import cos
svwrite(f"real theta = {cos(1)}")

def scaled_add(a, b):
  return f"{a} << 4 + {b} << 4"
$$$

// $$<code>$$ Can be for inline macros, where <code> is automatically evaluated and inserted into the line
logic a = $$3 + 4$$
logic b = $$12 / 3$$
logic test = $$scaled_add("a", "b")$$

Running the above code blocks through SVPY produces the following output:

// Any line starting with "$ " is a macro
logic foo = 3

// Triple dollar signs indicate block macro
real theta = 0.5403023058681398

// $$<code>$$ Can be for inline macros, where <code> is automatically evaluated and inserted into the line
logic a = 7
logic b = 4.0
logic test = a << 4 + b << 4

Environment Setup

Running SVPY simply requires running a Python file that calls the build() command. An example file can be seen below:

from svpy import build

build(input_directory="src", output_directory="build", plugins=["my_plugin1", "my_plugin2"])

Result:

• All files in the filepath input_directory are processed
• The processed files are placed in output_directory (file names are echoed from input)
• The plugins listed in plugins are automatically imported for every file processed

Plugins

Plugins are simply python modules that can be imported into an svpy project and are accessible from the processed SV files. An example plugin can be seen below:

to_bits.py

__all__ = [
    "to_bits"
]

from math import floor

# Converts a decimal value into binary
def to_bits(value, bits=16, precision=0):
    value = value * (2**precision)

    output = ""

    value = floor(value)
    for i in range(bits):
        output = (str(value % 2)) + output
        value = floor(value / 2)

    return f"{bits}'b" + output

If to_bits.py were included in the plugins list, then the to_bits function would be made available to all SV files. Plugins can be imported from any paths accessible by the current python context.

Note: This isn't much different than simply importing python modules normally, which is also possible. I just thought plugins made it sound cooler and more extensible.