Operand Model — Named Slots

Overview

VERA uses named slots instead of registers. A slot is a named storage location scoped to a function. The compiler decides whether each slot lives in a hardware register, on the stack, or is spilled to memory.

Slot Rules

• Slots are declared implicitly on first assignment (when they appear as a destination).
• Slot names are alphanumeric identifiers with underscores: [a-zA-Z_][a-zA-Z0-9_]*
• Slots are scoped to their enclosing function — no global slots (use global for that).
• Slots have a fixed type determined by the first instruction that writes to them.
• A slot's type must be consistent across all instructions that reference it. It is an error to use count as i64 in one instruction and f64 in another.
• Slots can be reassigned (they are not single-assignment).

Why Not Registers

Explicit registers (r0, r1, rax, x0) are architectural concerns. They make the representation non-portable and force the author to do register allocation — a job the compiler does better. Named slots let the agent focus on logic while the compiler handles resource mapping.

Why Not Variables

Slots are not variables in the programming-language sense. There is no scope nesting, no shadowing, no lifetime management at the language level. A slot is simply a name for a value that the compiler maps to physical storage. This keeps VERA at the assembly level.