Skip to content

isa.md

Latest commit

 

History

History
107 lines (74 loc) · 2.45 KB

isa.md

File metadata and controls

107 lines (74 loc) · 2.45 KB

ZASM ISA v1.0.0 (Normative)

Purpose and scope

ZASM is a human-facing assembly language that lowers to WAT. This document defines its register model, instruction set, directives, and primitive calling conventions. All conforming assemblers/linkers MUST follow these rules.

Register model

Registers are i32 locals in the generated WAT.

  • HL: primary accumulator and pointer (slice ptr)
  • DE: secondary accumulator and length (slice len)
  • A: byte accumulator
  • BC: general purpose
  • IX: general purpose

Rules:

  • Registers are function-local.
  • HL/DE form the standard slice (ptr,len) ABI.
  • There is no flags register; comparisons use CP and $cmp.

Instruction set

Load/store

  • LD r, imm|sym
  • LD r1, r2
  • LD A, (HL)
  • LD (HL), A

r/r1/r2 are from {HL,DE,A,BC,IX}. (HL) is the only supported memory form.

Arithmetic

  • INC HL|DE|BC
  • DEC DE|BC
  • ADD HL, #imm
  • ADD HL, DE
  • SUB HL, #imm
  • SUB HL, DE

Compare and branch

  • CP HL, rhs
    • rhs is DE, immediate, or a symbol constant.
    • Sets $cmp = HL - rhs (signed).
  • JR label
  • JR COND, label with COND in {EQ,NE,LT,LE,GT,GE} (signed compare vs 0).

Call/return

  • CALL sym
  • RET

Directives

  • DB — data bytes
  • DW — i32 constant
  • RESB — reserve bytes (zeroed)
  • STR — data bytes + auto <name>_len
  • EQU — constant symbol from a numeric literal
  • PUBLIC — export a symbol
  • EXTERN — import a function symbol

Primitive calls (reserved _ namespace)

All symbols starting with _ are reserved for host primitives.

_in

  • Inputs: HL = dst_ptr, DE = cap
  • Returns: HL := nread

_out

  • Inputs: HL = ptr, DE = len

_log

  • Inputs: HL = topic_ptr, DE = topic_len, BC = msg_ptr, IX = msg_len

_alloc

  • Input: HL = size
  • Return: HL := ptr (or -1 on OOM)

_free

  • Input: HL = ptr

Error behavior

  • Unknown mnemonic/directive: hard error.
  • Unknown symbol: hard error.
  • Duplicate symbol: hard error.

Determinism requirements

  • Emitted IR and WAT MUST be byte-for-byte deterministic for identical inputs.
  • Data layout is deterministic: fixed base offset and 4-byte alignment.
  • No timestamps, random IDs, or host-dependent formatting.

Versioning

  • ISA version is v1.0.0.
  • Backward-compatible additions MAY be introduced in later minor versions.