M4: Bootstrap loop — native binary rebuilds next compiler revision

[PurHur]

Parent

Epic: #1492 (Self-host critical path M3→M5)

Milestone

M4 — bootstrap loop: native gen-1 compiles gen-2 without Zend on the compile step

Problem (May 2026 harness)

Scaffold landed; remaining gap is M5 cold boot (no vendor/, compiled driver everywhere) — not “no gen-2 binary.”

Slice	Status (2026-05-27 probe)
test/selfhost/bootstrap_loop_smoke/ lint + link	✅
make bootstrap-loop-probe (full)	✅ emit_path=native, exit 0
bootstrap-loop-gen1-full-spine-emit.sh	✅ gen-2 compiler_lib_spine_smoke bundle OK
Zend-free cold boot	⬜ #2771, #2768

Goal

Bootstrap loop closed for CI: gen-1 native binary compiles gen-2 smoke and (opt-in) full spine; no php bin/compile.php on the compile step; documented in docs/bootstrap-m5-fast-path.md.

Definition of done

• test/selfhost/bootstrap_loop_smoke/ + ./script/bootstrap-loop-probe.sh
• Gen-2 smoke native (emit_path=native) — full probe exit 0
• Full-spine gen-2 (bootstrap-loop-gen1-full-spine-emit.sh) green on harness
• BOOTSTRAP_M4_LOOP_PROBE=1 default-on in ci-local.sh llvm tail — Self-host: M4 full-spine probe target and wave-check driver smoke CLI #2777
• Full-spine slice default in bootstrap-loop-probe.sh when BOOTSTRAP_M4_GEN1_COMPILE_FULL_SPINE=1 — Self-host M4: default-on full-spine gen-1 emit in bootstrap-loop-probe / ci-local #2770
• No vendor/ at loop step — Self-host M5: cold-boot wave-check without vendor/ on disk #2771 / M5: Prelink vendor (php-cfg, php-types, php-llvm) — no composer at cold boot #1416 M5
• docs/bootstrap-selfhost.md M4 rows updated (no “exit 2” / partial HelloWorld)

Repro

# Smoke ladder (green)
./script/docker-exec.sh -- bash -lc 'make bootstrap-loop-probe'

# Inventory-scale gen-2 (green)
./script/docker-exec.sh -- bash -lc './script/bootstrap-loop-gen1-full-spine-emit.sh'

# Optional: full probe with spine env
BOOTSTRAP_M4_GEN1_COMPILE_FULL_SPINE=1 ./script/bootstrap-loop-probe.sh

Scope (next PRs)

Piece	Path
CI default	script/ci-local.sh, script/ci-defaults.env
Full-spine in probe	script/bootstrap-loop-probe.sh
M5 driver	script/bootstrap-selfhost-driver-smoke.sh, #2769

Unblock order

#2768 Expr_Closure → #2771 cold boot → #2769 compiled wave-check → M5

Links

• docs/self-host-target.md M4
• docs/bootstrap-m5-fast-path.md
• Self-host: M4 full-spine probe target and wave-check driver smoke CLI #2777, Self-host M4: default-on full-spine gen-1 emit in bootstrap-loop-probe / ci-local #2770, Self-host M5: cold-boot wave-check without vendor/ on disk #2771, Self-host M5: bootstrap-selfhost-driver-smoke — compiled gen-1 replaces Zend in wave-check #2769

[PurHur]

Reopening: PR #1512 delivered prerequisite ladder + --dry-run only. M4 DoD (gen-1→gen-2 native rebuild, second-gen smoke) is still open — see probe NEXT output and issue checklist.

[PurHur]

Blocked on gen-1 link until #1519 (missing test/bootstrap-aot/global_smoke_aliases.php). Verified: compiler_helloworld_smoke links OK; bootstrap_loop_smoke fails at Zend AOT link with IncludeHelper #54.