Tessera PVM

Tessera PVM is a Python implementation of the Tessera virtual machine, offering two execution modes: a straightforward interpreter and a more performant recompiler.

Project Structure

• tsrkit_pvm/: The main package.
  • core/: Abstract base classes and core PVM components.
  • common/: Shared utilities and data structures.
  • interpreter/: The interpreter-based PVM implementation.
  • recompiler/: The recompiler-based PVM implementation.
• tests/: The project's test suite, which includes PVM test cases and schemas.

Core Components

The fundamental building blocks of the PVM are defined in tsrkit_pvm/core/:

• ipvm.py: Contains the PVM abstract base class.
• program_base.py: Defines the base class for PVM programs.
• memory.py: Provides the base class for memory management.

Implementations

1. Interpreter: Located in tsrkit_pvm/interpreter/, this implementation executes bytecode instruction by instruction. It is easier to debug and inspect.
2. Recompiler: Found in tsrkit_pvm/recompiler/, this implementation recompiles PVM bytecode into native machine code for significantly faster execution.

Installation

Install the package using pip:

pip install .

Usage

The primary way to run a PVM program is to use the static execute method on either the Interpreter or Recompiler class.

Here is a corrected example of how to execute a PVM program with the interpreter:

from tsrkit_pvm.interpreter.pvm import Interpreter
from tsrkit_pvm.interpreter.program import Program
from tsrkit_pvm.interpreter.memory import INT_Memory
from tsrkit_pvm.common.status import ExecutionStatus

# Your PVM bytecode
bytecode = bytes([0, 0, 14, 40, 2, 200, 50, 1, 40, 2, 200, 67, 2, 51, 1, 40, 246, 165, 20])

# 1. Decode the bytecode into a Program object
# The `decode` method returns a single Program instance.
program = Program.decode(bytecode)

# 2. Initialize memory, registers, and gas
# INT_Memory takes a dictionary for initial memory, a list for input, and a list for output.
memory = INT_Memory({}, [], [])
registers = [0] * 13  # PVM has 13 registers
gas = 100_000

# 3. Execute the program
status, final_pc, remaining_gas, final_registers, final_memory = Interpreter.execute(
    program=program,
    program_counter=0,
    gas=gas,
    registers=registers,
    memory=memory
)

# 4. Check the result
if status == ExecutionStatus.OUT_OF_GAS:
    print("Execution finished: Out of gas.")
    print(f"Gas consumed: {gas - remaining_gas}")
else:
    print(f"Execution finished with status: {status}")

Testing

To run the comprehensive test suite and verify the functionality of both the interpreter and recompiler, use pytest:

poetry run pytest