How does CRuby represent execution state using VM registers and stack abstraction?

CRuby uses a stack-based VM with pseudo-registers mapped onto stack slots.

Although YARV is a stack-based VM, it internally uses optimized stack slot indexing that behaves like virtual registers. Each instruction manipulates stack positions rather than named registers. Locals are stored in fixed stack offsets, enabling fast access. This hybrid design allows simplicity of stack machines with near-register performance.