Introduction

Strontium is a register-based bytecode virtual machine with typed registers and multimethod dispatch, built to power the Mag programming language.

Mag source code is parsed and compiled to Strontium bytecode by magc, then executed here.

Registers

The following registers are pre-allocated when the machine starts:

Register	Type	Content	Description
bc	Array<UInt8>	[]	Bytecode of the running program.
arg	any		Argument register for multimethod dispatch.
ret	any		Return value register for method calls.
r1..r8	Empty		General-purpose registers, allocated as needed.

Instruction Set

Opcode	Name	Description
0	HALT	Stop execution.
1	LOAD	Load a literal value into a register.
2	MOVE	Move a value from one register to another (source is cleared).
3	COPY	Copy a value from one register to another (source is unchanged).
4	CALCULATE	Arithmetic on two registers (ADD, SUBTRACT, MULTIPLY, DIVIDE, MODULO, POWER, SQRT).
5	COMPARE	Comparison on two registers (EQ, NEQ, LT, LTE, GT, GTE); result written to a third.
6	BITWISE	Bitwise operation (AND, OR, XOR, NOT, LSH, RSH).
7	JUMP	Set the program counter to an absolute byte address.
8	JUMPC	Conditional jump: jumps when the register at conditional_address holds Boolean(false).
9	INTERRUPT	Emit a VM interrupt (PRINT, READ).
10	CALL	Call a method at an absolute byte address, pushing a new stack frame.
11	RETURN	Return from a method call, restoring the previous stack frame.
14	STOREL	Store a register value into the current stack frame's local variables.
15	LOADL	Load a value from the current stack frame's local variables into a register.
16	DISPATCH	Multimethod dispatch: match the value in arg against registered patterns and jump to the match.

Multimethod Dispatch

Methods are registered in a dispatch table keyed by name. Each entry carries a DispatchPattern:

• Value(v) — matches a specific value (e.g. 0 for fib(0)), precedence 3
• Type(t) — matches any value of a given type (e.g. Int for def foo(n Int)), precedence 2
• Any — matches anything (untyped variable pattern), precedence 1

The first pattern with the highest precedence that matches the argument wins.

Project Status

Alpha — API and semantics will change. Not suitable for production use.

License

Licensed under the MIT license.