Compile target: ARM64 / AArch64 Linux

• Type: feature
• Status: done
• Owner: claude
• Blocked-by: feature-target-i386
• Unblocks: feature-target-arm32, feature-additional-cpu-targets
• Opened: 2026-06-06 (user request; roadmap.md Phase 3)

Motivation

ARM64 (Raspberry Pi 4+) is the first non-x86 ISA — a real test of the target-abstraction introduced by the i386 work. Reuses that backend parameterization rather than re-deriving it.

Scope

Per ../../developer/roadmap.md Phase 3:

• AArch64 register set, AAPCS64 calling convention, fixed-width instruction encoding.
• AArch64 ELF emission and Linux syscall ABI.
• First ISA where instruction encoding differs structurally from x86 (no variable-length opcodes) — the encoder must generalize.

Acceptance

ARM64 output runs on an AArch64 Linux host (e.g. Pi 4); the suite passes; the build meets the fixedpoint gate for the AArch64 target.

Dependency note

Blocked-by feature-target-i386 is the roadmap's strategic staging plus reuse of the target-abstraction it introduces — not a hard ISA requirement. Move to urgent/ to pull it forward.

Log

• 2026-06-06 — ticket opened from user request + roadmap Phase 3.
• 2026-06-10 — concrete deliverable set with user: binary runs on Raspberry Pi 5 (BCM2712, Cortex-A76, ARMv8.2-A, 64-bit Pi OS). i386 before this is not about i386 — it flushes 32-bit assumptions (ptr size, Int64 pairs, ELF32) ahead of the ESP32 goal. qemu-aarch64 runner + exit-42 probe already green (chore-qemu-test-env).
• 2026-06-10 — Resolved SIGSEGV in RX memory by using BSS_INTBUF, added width emitters (EmitwriteIntWA64, EmitwriteUIntWA64), resolved SpacesOffset misalignment using EmitDataRef/ldr x1. Tests pass. Committed.