Program and the CompilerKit Runtime

Program is a simple struct type that is used by Codegen to store and return a program’s compiled bytecode that can be run using the CompilerKit runtime. You should not build a Program instance by hand, but instead use Codegen.

CompilerKit::Program

struct Program {
    std::vector<uint8_t> code;
    std::vector<float> constants;
    uint16_t variableCount;
};

Programs do not have methods. Instead, they can be run using the free-standing function CompilerKit::run(const Program& program). For debugging purposes, a program can be disassembled and printed to an output stream with the standard caret syntax:

Program prog = codegen.getProgram();
std::cout << prog << "\n"; // print out machine code for debugging.
run(program);

The CompilerKit Runtime

The CompilerKit runtime is a very simple stack-based virtual machine. Operations pop their operand values from the stack, and push their results onto it. There is a separate memory dedicated to local variables, and a constant pool included with the program.

Instructions for the runtime are 8-bit long, with an optional 16-bit operand, used for instructions that require a jump offset, a constant index, or a local variable index. The table presented below lists valid runtime instructions.

Mnemonic	Operand	Stack Effect	Description
Halt	no	[]	Stop the execution of the program
Noop	no	[]	Do nothing
Const	16-bit index	push 1	Push the constant at index onto stack
Load	16-bit index	push 1	Push the local variable at index onto stack
Store	16-bit index	pop 1	Pop a value into the local variable at index
Input	no	push 1	Read value from stdin and push it onto stack
Output	no	pop 1	Pop a value and display it on stdout
Neg	no	pop 1, push 1	Pop a float from the stack, and push its opposite
Add	no	pop 2, push 1	Pop floats b then a, push a + b
Sub	no	pop 2, push 1	Pop floats b then a, push a - b
Mul	no	pop 2, push 1	Pop floats b then a, push a * b
Greater	no	pop 2, push 1	Pop floats b then a, push a > b
Less	no	pop 2, push 1	Pop floats b then a, push a < b
Equals	no	pop 2, push 1	Pop floats b then a, push a == b
And	no	pop 2, push 1	Pop booleans b then a, push a && b
Or	no	pop 2, push 1	Pop booleans b then a, push a || b
Not	no	pop 1, push 1	Pop boolean a from stack, and push !a
Jump	16-bit offset	[]	Advance instruction pointer by offset
Loop	16-bit offset	[]	Rewind instruction pointer by offset
IfNot	16-bit offset	pop 1	Pop boolean from stack, if false, same as Jump