Implementation Decisions

VM

• For comparison operators, we will only use equality, non-equality (to handle NaN appropriately), greater, and greater-equal. Lesser and lesser-equal will be implemented by flipping.

Function Calling Convention

• On call:
  • Caller pushes parameters in backwards order, then function object.
  • Caller uses CALL instruction.
    • Push the frame pointer.
    • Push the program counter.
    • Set the new frame pointer to be at the stack pointer.
• On return:
  • Callee uses RET instruction.
    • RET assumes the return value is on top of the stack.
    • Read the return value and store temporarily.
    • Set stack pointer to frame pointer.
    • Reset program counter.
    • Reset frame pointer.
    • Pop function object.
    • Pop parameters.
    • Push return value to the top of the stack.

Bytecode File Format

• Metadata:
  • Magic number (consider versioning?)
  • Maximum number of global values
  • Execution start index
  • Length (?)
• Static data:
  • Strings
  • Function definition:
    • Name
    • Number of parameters
    • Body bytecode
• Instructions