dobios / btor2-opt

Very basic btor2 parser, circuit miter, and code optimizer

btor2-opt

Very basic btor2 parser, circuit miter, and code optimizer.

Overview

This repo contains two main scripts:

• btor2-opt: Takes a .btor2 file and a list of pass names as argument and prints out the transformed result.
• btor2-miter: Takes a .fir file as input and runs it through firrtl and firtool to obtain two .btor2 designs which are then merged into a single miter circuit before being returned to the user. Note that this requires having firrtl and firtool in your path, specifically a version of firtool that has the --btor2 flag.

The rest of the code can be found in the src folder, which contains a basic parser for btor2 (not entirely complete, but supports anything firtool --btor2 can produce), an internal representation of the language and a simple pass infrastructure, where you can add any of you custom passes.

Adding a Pass

Simply create a new class (as its own file) in src/passes that inherits from Pass. Then in the constructor, make sure you give it a name. The pass's logic itself is written by overiding the run(p: list[Instruction]) -> list[Instruction] method. The pass must then be imported in src/passes/passes.py and instantiated in the all_passes list. Passes are grouped either in transforms, which contain all of the passes that transform the AST, and validation, which contains all of the passes used to gurantee the syntactic correctness of the output program.

Here is a simple example pass that renames all inputs to "inp_n".

# Example pass: Simply renames all inputs to inp_<pos>
class RenameInputs(Pass):
    def __init__(self):
        super().__init__("rename-inputs")

    # I chose to have this pass not modify p in place
    # you can also simply modify p and return it
    def run(p: list[Instruction]) -> list[Instruction]:
        i = 0
        res = []
        for inst in p:
            if isinstance(inst, Input):
                res.append(Input(inst.lid, inst.sort, f"inp_{i}"))
                i += 1
            else:
                res.append(inst)
        return res

# Make sure to add an instance of the pass to the all_passes array
all_passes = [RenameInputs()]

This pass can then be called by running:

python3 btor2-opt.py ex.btor2 rename-inputs