Description

Implement a virtual machine (VM) capable of executing bytecode generated by the BytecodeEmitter. The VM should support basic operations such as loading constants, storing and loading variables, and performing arithmetic operations. Additionally, the VM should manage memory efficiently using a simple garbage collection mechanism based on reference counting.

Tasks

1. Define Bytecode Instructions:

   • Add opcodes for basic operations: LOAD_CONST, STORE_NAME, LOAD_NAME, ADD, SUBTRACT, MULTIPLY, DIVIDE, PRINT, RETURN.

2. Implement GCObject and Subclasses:

   • Create GCObject class with reference counting.
   • Implement GCInt subclass for integer values.
   • Implement GCString subclass for string values.

3. Develop Virtual Machine:

   • Initialize the VM with bytecode, constants, and names.
   • Implement stack-based execution of bytecode instructions.
   • Add support for arithmetic operations.
   • Implement variable storage using an environment dictionary.

4. Garbage Collection:

   • Increase reference count when objects are added to the stack or environment.
   • Decrease reference count when objects are removed from the stack or environment.
   • Ensure objects are deallocated when their reference count reaches zero.

5. File I/O:

   • Implement method to load bytecode, constants, and names from a binary file.

6. Cython Optimization:

   • Add type annotations for performance optimization.
   • Create setup.py for building the Cython extension.

Details

Bytecode Instructions

• LOAD_CONST: Pushes a constant onto the stack.
• STORE_NAME: Stores the top value from the stack in the environment with a given name.
• LOAD_NAME: Pushes the value of a named variable onto the stack.
• ADD, SUBTRACT, MULTIPLY, DIVIDE: Perform arithmetic operations on the top two values on the stack.
• PRINT: Prints the top value from the stack.
• RETURN: Ends execution of the bytecode.

Classes

GCObject

• Reference counting for memory management.
• incref and decref methods to manage reference counts.
• destroy method to handle object-specific cleanup.

GCInt and GCString

• Subclasses of GCObject for integer and string values, respectively.
• Override destroy method as needed.

Virtual Machine

• Initialize with bytecode, constants, and names.
• Execute bytecode instructions using a stack-based approach.
• Manage variables with an environment dictionary.
• Implement reference counting for garbage collection.

File I/O

• Method to load bytecode, constants, and names from a binary file.

Cython Optimization

• Use type annotations to optimize performance.
• Create setup.py for building the Cython extension.

References

• Cython Documentation
• Python's struct Module

Expected Outcome

A fully functional virtual machine capable of executing bytecode with basic arithmetic and variable management. The VM should also include a simple garbage collection mechanism to manage memory efficiently.

Additional Information

This issue aims to implement a foundational VM that can be extended with more complex features and optimizations in future iterations.