Self-host M3: Native emit for compiler compile-smoke fixture (post-#1493)

[PurHur]

Problem

#1493 targets strict HelloWorld native emit (no Zend bin/compile.php fallback). The next honest step toward #1498 / #1521 is not jumping straight to full lib/ — it is proving the self-host bundle can emit a slightly larger fixture that exercises the real compile driver (Compiler → JIT → AOT link) beyond a one-line echo.

Today test/selfhost/compiler_compile_smoke/ (or equivalent) may still use Zend emit even when M3 run is native.

Goal

BOOTSTRAP_M3_COMPILE_SMOKE_STRICT=1 ./script/bootstrap-selfhost-compile-smoke-probe.sh
# exits 0: native binary emits + links compile-smoke output without Zend compile.php

Milestone	Proves
HelloWorld strict	#1493 — minimal emit
This issue	Native emit for compiler_compile_smoke bundle (multi-op, still tiny)
M4 loop	#1498 — rebuild next compiler tree

Implementation hints

Step	Path	Notes
Fixture	test/selfhost/compiler_compile_smoke/main.php	Grow only as M3 allowlist (#1905, #1768) permits
Probe	script/bootstrap-selfhost-compile-smoke-probe.sh	Mirror bootstrap-selfhost-helloworld-probe.sh
Gate	BOOTSTRAP_M3_COMPILE_SMOKE_STRICT_GATE	Opt-in in ci-local.sh (0); flip after green
Blockers	lib/VM/HashTable.php, native runtime	Same class as #1514 / #1761
Allowlist	lib/JIT.php M3 batches	Extend #1905 snapshot when symbols land

Acceptance criteria

• Probe passes in php-compiler:22.04-dev with LLVM 9
• Documented in docs/self-host-target.md M3 ladder (between HelloWorld and M4)
• Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492 epic + ROADMAP 🗺️ ROADMAP: Self-host + web-capable PHP subset (living) #78 reference this stepping stone
• make north-star2-verify (DevEx: make north-star2-verify presenter gate (self-host M0–M4) #1865) includes probe when gate 1

Verification (local / Docker only)

make docker-build-22
docker run --rm -v "$(pwd):/compiler" -w /compiler php-compiler:22.04-dev \
  bash -lc 'script/apply-patches.sh && BOOTSTRAP_M3_COMPILE_SMOKE_STRICT=1 ./script/bootstrap-selfhost-compile-smoke-probe.sh'

No GitHub Actions.

Dependencies

• M3: BOOTSTRAP_M3_HELLOWORLD_STRICT — native HelloWorld emit (no Zend fallback) #1493 — HelloWorld strict emit (blocker)
• M3: Native HelloWorld runtime segfault in __hashtable__readStringKeyValue (helloworld_compile_smoke) #1514 ✅ / Self-host M3: HashTable rehash for native AOT runtime (#66 → #1514) #1761 ✅ — hashtable runtime fixes
• Self-host M3: check-m3-allowlist-snapshot.php drift guard (#1768 SSOT) #1905 — M3 allowlist drift guard
• Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492 — parent epic

Links

• docs/bootstrap-selfhost.md, docs/self-host-target.md
• ROADMAP 🗺️ ROADMAP: Self-host + web-capable PHP subset (living) #78 Phase 5 Self-host

[PurHur]

Backlog batch 97: implementation split tracked in #1977 (native compile_driver_smoke emit). Keep this issue as umbrella; close together when BOOTSTRAP_M3_COMPILE_SMOKE_STRICT probe passes without Zend fallback.

[PurHur]

Probe landed (partial M3) — #1972 merged bootstrap-selfhost-compile-smoke-probe.sh:

• Default gate: bundle link + Zend emit of compiler_smoke_standalone.php + native run (emit_path=zend)
• Strict mode (BOOTSTRAP_M3_COMPILE_SMOKE_STRICT=1): exits 1 until native emit lands here

Implementation track consolidated here; #1977 closed as duplicate (same compile_driver_smoke.php goal).

Next PR should: wire native emit path in probe (no bin/compile.php fallback), then enable BOOTSTRAP_M3_COMPILE_SMOKE_STRICT_GATE (#1968).

[PurHur]

Batch 100 update: #1994 merged M3 compile-smoke native emit infrastructure (probe + strict gate wiring). Strict native emit of compile_driver_smoke.php remains open on this issue.

Next steps:

1. Land strict emit lowering (or extend Self-host M3: compile-driver real lowering symbol batch tracker #1768 batches)
2. Flip CI: BOOTSTRAP_M3_COMPILE_SMOKE_STRICT_GATE opt-in in ci-local after #1937 #1968 opt-in → CI: Default BOOTSTRAP_M3_HELLOWORLD_STRICT_GATE=1 in ci-local after #1493 #1866 default-on in ci-local after green Docker run
3. Coordinate with open Fix M2 spine native link (#1960) #1988 only if spine units overlap compile-driver path

Verify (local):
```bash
BOOTSTRAP_M3_COMPILE_SMOKE_STRICT=1 ./script/bootstrap-selfhost-compile-smoke-probe.sh
```